Patent Publication Number: US-9839978-B2

Title: Method and system for additive manufacturing using high energy source and hot-wire

Description:
PRIORITY 
     The present application is a continuation in part of, and claims priority to, U.S. patent application Ser. No. 14/163,367 filed on Jan. 24, 2014, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     Certain embodiments relate to additive manufacturing applications. More particularly, certain embodiments relate to a system and method to use a combination filler wire feed and energy source system for additive manufacturing applications. 
     BACKGROUND 
     The use of additive manufacturing has grown recently using various methods. However, known methods have various disadvantages. For example, some processes use metal powders which are generally slow and can result in a fair amount of waste of the powders. Other methods, which use arc based systems, are also slow and do not permit for the manufacture of highly precise articles of manufacture. Therefore, there is a need for additive manufacturing processes and systems which can operate a high speeds, with a high level of precision. 
     Further limitations and disadvantages of conventional, traditional, and proposed approaches will become apparent to one of skill in the art, through comparison of such approaches with embodiments of the present invention as set forth in the remainder of the present application with reference to the drawings. 
     SUMMARY 
     Embodiments of the present invention comprise a system and method for additive manufacturing where a high energy device irradiates a surface of a work piece with a high energy discharge to create a molten puddle on a surface of the work piece. A wire feeding device feeds a wire to the puddle, and a power supply supplies a heating signal to the wire where the heating signal comprises a plurality of current pulses and where each of the current pulses creates a molten droplet on a distal end of the wire which is deposited into the puddle. Each of the current pulses reaches a peak current level after the wire feeder causes the distal end of the wire to contact said puddle and the heating signal has no current in between the plurality of the current pulses. The wire feeder controls the movement of the wire such that the distal end of the wire is not in contact with the puddle between subsequent peak current levels of the current pulses, and the power supply controls the heating current such that no arc is created between the wire and the work piece during the current pulses. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects of the invention will be more apparent by describing in detail exemplary embodiments of the invention with reference to the accompanying drawings, in which: 
         FIG. 1  illustrates a schematic block diagram of an exemplary embodiment of an additive manufacturing system of the present invention; 
         FIGS. 2A to 2D  illustrate a droplet deposition process in accordance with an exemplary embodiment of the present invention; 
         FIG. 3  illustrates another view of a droplet deposition process in accordance with an exemplary embodiment of the present invention; 
         FIGS. 4A to 4B  illustrate representative current waveforms that can be used with embodiments of the present invention; 
         FIG. 5  illustrates a representative embodiment of a voltage and current waveform of the present invention; 
         FIGS. 6A and 6B  illustrate utilization of a laser to aid in droplet deposition; 
         FIG. 7  illustrates an exemplary embodiment of wire heating system in accordance with an aspect of the present invention; 
         FIG. 8A  illustrates an exemplary embodiment of a current waveform that can be used with the system of  FIG. 7 ; 
         FIG. 8B  illustrates an exemplary embodiment of waveforms for current, voltage, wire feed speed and laser power for an exemplary embodiment of the present invention; 
         FIG. 9  illustrates another exemplary embodiment of a wire heating system of the present invention; 
         FIG. 10  illustrates a further exemplary embodiment of the present invention using multiple wires; 
         FIG. 11  illustrates another exemplary embodiment of a system of the present invention; 
         FIG. 12  illustrates a power supply system in accordance with an embodiment of the present invention; 
         FIG. 13  illustrates an embodiment of a system which uses multiple consumables at one time; 
         FIG. 14  illustrates an another embodiment of the system in  FIG. 13 ; 
         FIG. 15  illustrates a further exemplary embodiment of the system shown in  FIG. 13 ; 
         FIG. 16  illustrates an exemplary embodiment of a non-bonding manufacturing substrate; 
         FIG. 17A to 17C  illustrate further exemplary embodiments of a non-bonding manufacturing substrate; 
         FIG. 18A  illustrates an embodiment of a non-bonding substrate having a cooling system; 
         FIG. 18B  illustrates an exemplary embodiment of a manufacture truss structure that can be used with embodiments of the present invention; 
         FIGS. 19A to 19C  illustrate exemplary embodiments of braided additive manufacturing consumables that can be used with systems described herein; 
         FIGS. 20A to 20B  illustrate an exemplary braided consumable that has been deformed in accordance with embodiments of the present invention; 
         FIG. 20C  illustrates an embodiment of a dual wire deposition contact tip assembly as described herein; 
         FIG. 20D  illustrates a further exemplary embodiment of a dual wire contact tip of the present invention; 
         FIGS. 21A and 21B  illustrate an exemplary contact tip assembly of the present invention that can be used to deform consumables for delivery during a deposition process; 
         FIG. 22  illustrates another exemplary consumable of the present invention; 
         FIG. 23  illustrates a further exemplary embodiment of a consumable for additive manufacturing as described herein; and 
         FIGS. 24A to 24D  illustrates additional exemplary embodiments of additive manufacturing consumables that can be used with embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the invention will now be described below by reference to the attached Figures. The described exemplary embodiments are intended to assist the understanding of the invention, and are not intended to limit the scope of the invention in any way. Like reference numerals refer to like elements throughout. 
     The term “additive manufacturing” is used herein in a broad manner and may refer to any applications including building up, constructing, or creating objects or components 
       FIG. 1  illustrates a functional schematic block diagram of an exemplary embodiment of a combination filler wire feeder and energy source system  100  for performing additive manufacturing. The system  100  includes a laser subsystem capable of focusing a laser beam  110  onto a workpiece  115  to heat the workpiece  115 . The laser subsystem is a high intensity energy source. The laser subsystem can be any type of high energy laser source, including but not limited to carbon dioxide, Nd:YAG, Yb-disk, YB-fiber, fiber delivered or direct diode laser systems. Other embodiments of the system may include at least one of an electron beam, a plasma arc welding subsystem, a gas tungsten arc welding subsystem, a gas metal arc welding subsystem, a flux cored arc welding subsystem, and a submerged arc welding subsystem serving as the high intensity energy source. The following specification will repeatedly refer to the laser system, beam and power supply, however, it should be understood that this reference is exemplary as any high intensity energy source may be used. For example, a high intensity energy source can provide at least 500 W/cm 2 . The laser subsystem includes a laser device  120  and a laser power supply  130  operatively connected to each other. The laser power supply  130  provides power to operate the laser device  120 . 
     The system  100  also includes a hot filler wire feeder subsystem capable of providing at least one resistive filler wire  140  to make contact with the workpiece  115  in the vicinity of the laser beam  110 . Of course, it is understood that by reference to the workpiece  115  herein, the molten puddle is considered part of the workpiece  115 , thus reference to contact with the workpiece  115  includes contact with the puddle. The wire feeder subsystem includes a filler wire feeder  150 , a contact tube  160 , and a power supply  170 . During operation, the filler wire  140  is resistance-heated by electrical current from the power supply  170  which is operatively connected between the contact tube  160  and the workpiece  115 . In accordance with an embodiment of the present invention, the power supply  170  is a pulsed direct current (DC) power supply, although alternating current (AC) or other types of power supplies are possible as well. The wire  140  is fed from the filler wire feeder  150  through the contact tube  160  toward the workpiece  115  and extends beyond the tube  160 . The extension portion of the wire  140  is resistance-heated such that the extension portion approaches or reaches the melting point before contacting a puddle on the workpiece. The laser beam  110  serves to melt some of the base metal of the workpiece  115  to form a puddle and can also be used to melt the wire  140  onto the workpiece  115 . The power supply  170  provides energy needed to resistance-melt the filler wire  140 . As will be explained further below, in some embodiments the power supply  170  provides all of the energy needed while in other embodiments the laser or other high energy heat source can provide some of the energy. The feeder subsystem may be capable of simultaneously providing one or more wires, in accordance with certain other embodiments of the present invention. This will be discussed more fully below. 
     The system  100  further includes a motion control subsystem capable of moving the laser beam  110  (energy source) and the resistive filler wire  140  in a same direction  125  along the workpiece  115  (at least in a relative sense) such that the laser beam  110  and the resistive filler wire  140  remain in a fixed relation to each other. According to various embodiments, the relative motion between the workpiece  115  and the laser/wire combination may be achieved by actually moving the workpiece  115  or by moving the laser device  120  and the wire feeder subsystem. In  FIG. 1 , the motion control subsystem includes a motion controller  180  operatively connected to a robot  190 . The motion controller  180  controls the motion of the robot  190 . The robot  190  is operatively connected (e.g., mechanically secured) to the workpiece  115  to move the workpiece  115  in the direction  125  such that the laser beam  110  and the wire  140  effectively travel along the workpiece  115 . In accordance with an alternative embodiment of the present invention, the laser device  110  and the contact tube  160  may be integrated into a single head. The head may be moved along the workpiece  115  via a motion control subsystem operatively connected to the head. 
     In general, there are several methods that a high intensity energy source/wire may be moved relative to a workpiece. If the workpiece is round, for example, the high intensity energy source/wire may be stationary and the workpiece may be rotated under the high intensity energy source/wire. Alternatively, a robot arm or linear tractor may move parallel to the round workpiece and, as the workpiece is rotated, the high intensity energy source/wire may move continuously or index once per revolution to, for example, overlay the surface of the round workpiece. If the workpiece is flat or at least not round, the workpiece may be moved under the high intensity energy source/wire as shown if  FIG. 1 . However, a robot arm or linear tractor or even a beam-mounted carriage may be used to move a high intensity energy source/wire head relative to the workpiece. 
     The system  100  further includes a sensing and current control subsystem  195  which is operatively connected to the workpiece  115  and the contact tube  160  (i.e., effectively connected to the output of the power supply  170 ) and is capable of measuring a potential difference (i.e., a voltage V) between and a current (I) through the workpiece  115  and the wire  140 . The sensing and current control subsystem  195  may further be capable of calculating a resistance value (R=V/I) and/or a power value (P=V*I) from the measured voltage and current. In general, when the wire  140  is in contact with the workpiece  115 , the potential difference between the wire  140  and the workpiece  115  is zero volts or very nearly zero volts. As a result, the sensing and current control subsystem  195  is capable of sensing when the resistive filler wire  140  is in contact with the workpiece  115  and is operatively connected to the power supply  170  to be further capable of controlling the flow of current through the resistive filler wire  140  in response to the sensing, as is described in more detail later herein. In accordance with another embodiment of the present invention, the sensing and current controller  195  may be an integral part of the power supply  170 . 
     In accordance with an embodiment of the present invention, the motion controller  180  may further be operatively connected to the laser power supply  130  and/or the sensing and current controller  195 . In this manner, the motion controller  180  and the laser power supply  130  may communicate with each other such that the laser power supply  130  knows when the workpiece  115  is moving and such that the motion controller  180  knows if the laser device  120  is active. Similarly, in this manner, the motion controller  180  and the sensing and current controller  195  may communicate with each other such that the sensing and current controller  195  knows when the workpiece  115  is moving and such that the motion controller  180  knows if the filler wire feeder subsystem is active. Such communications may be used to coordinate activities between the various subsystems of the system  100 . 
     As is generally known, additive manufacturing is a process in which a material is deposited onto a workpiece so as to create desired manufactured product. In some applications the article of manufacture can be quite complex. However, known methods and systems used for additive manufacturing tend to be slow and have limited performance. Embodiments of the present invention address those areas by providing a high speed and highly accurate additive manufacturing method and system. 
     The system  100  depicted in  FIG. 1  is such an exemplary system, where the wire  140  is repeatedly melted, in droplets, and deposited onto the workpiece to create the desired shape. This process is exemplary depicted in  FIGS. 2A-2D . As shown in these figures. As shown in  FIG. 2A  a surface of the workpiece is irradiated by the laser beam  110  (or other heat source) while the wire  140  is not in contact with the workpiece. The beam  110  creates a molten puddle A on the surface of the workpiece. In most applications the puddle A has a small area and the level of penetration is not that which would be required for other operations, such as welding or joining. Rather, the puddle A is created so as to prepare the surface of the workpiece to receive and cause sufficient bonding with a droplet from the wire  140 . Thus, the beam density of the beam  110  is to be such that only a small puddle is created on the workpiece, without causing too much heat input into the workpiece or to create too large of a puddle. Upon creation of the puddle, a droplet D is formed on the distal end of the wire  140  as the wire is advanced to the puddle A so as to make contact with the puddle A, see  FIG. 2B . After contact, the droplet D is deposited onto the puddle A and workpiece (see  FIG. 2C ). This process is repeated so as to create a desired workpiece. In  FIG. 2D  an optional step is shown in which the beam  110  is directed at the deposited droplet D after it is separated from the wire  140 . In such embodiments, the beam  110  can be used to smooth the workpiece surface and/or add additional heat to allow the droplet D to be fully integrated to the workpiece. Further, the beam can be used to provide additional shaping of the workpiece. 
       FIG. 3  depicts an exemplary deposition process of the droplet D from the wire  140 . The image on the left edge of  FIG. 3  depicts the wire  140  making contact with the workpiece. This contact is detected by the power supply  170 , which then provides a heating current to the wire  140  so as to heat the wire to at or near a melting temperature for the wire  140 . The detection circuit used to detect contact between the workpiece and the wire  140  can be constructed and operate like known detection circuits used in welding power supplies, and therefore a detailed explanation of the circuit&#39;s operation and structure need not be provided herein. The heating current from the power supply  170  is ramped up very quickly to provide the necessary energy to melt the droplet D from the end of the wire  140 . However, the current is controlled carefully so that no arc is created between the wire  140  and the workpiece. The creation of an arc could prove to be destructive to the workpiece and is thus undesirable. Thus, the current is be controlled in such a way (explained further below) so as to prevent the formation of an arc. 
     Turning back to  FIG. 3 , the wire  140  makes contact with the workpiece and the power supply  170  provides a melting current (1). In some exemplary embodiments, an open circuit voltage OCV can be applied to the wire  140  prior to contact. After contact the current is ramped up quickly so to melt the end of the wire  140  to create a droplet D to be deposited (2). The current also causes the wire  140  to neck down just above the droplet D so as to allow for the separation of the droplet D from the wire  140  (3). However, the current is controlled such that while the wire  140  is necking down the current is either turned off or greatly reduced so that when the wire  140  separates from the droplet D no arc is created between the wire  140  and the workpiece (4). In some exemplary embodiments, the wire  140  can be retracted away from the workpiece during and just prior to the breaking of the connection between the droplet D and the wire  140 . Because the droplet D is in contact with the puddle the surface tension of the puddle will aid in breaking the droplet away from the wire  140 . Once the droplet has been separated from the wire  140 , the wire  140  is advanced to repeat the process to deposit another droplet. The wire  140  can be advanced at the same positioned and/or the next droplet can be deposited at any desired location. 
     As discussed previously, the laser beam  110  can also be utilized after the droplet D has been deposited on the workpiece to smooth or otherwise shape the workpiece after deposition. Furthermore, the beam  110  can further be utilized during the deposition process. That is, in some exemplary embodiments the beam  110  can be used to add heat to the wire  140  to aid in causing the formation of the droplet and/or the separation from the droplet D from the wire  140 . This will be discussed further below. 
     Turning now to  FIGS. 4A and 4B , each depict exemplary current waveforms that can be utilized with exemplary embodiments of the present invention. In  FIG. 4A , as can be seen, the waveform  400  has a plurality of pulses  401 , where each pulse represents the transfer of a droplet D from the wire  140 . A current pulse  401  is started at the time the wire  140  makes contact. The current is then increased using a ramp up portion  402  to a peak current level  401  which occurs just before the separation between the wire  140  and the droplet D. In this embodiment, during the ramp up portion  402  the current continually increases to cause the droplet to be formed and the necking down to occur in the wire before separation. Before separation of the droplet D the current is rapidly decreased during a ramp down portion  404  so that when separation occurs no arc is created. In the waveform  400  of  FIG. 4A  the current is shut off and drops to zero. However, in other exemplary embodiments of the present invention, the current can be dropped to a lower separation level and need not be shut off completely until the separation occurs. In such embodiments, the lower separation current level will continue to add heat to the wire  140  thus aiding in the breaking off of the droplet D. 
       FIG. 4B  depicts another exemplary embodiment of a current waveform  410 . However, in this embodiment, the pulses  411  have a ramp up portion  402  which utilizes a plurality of different ramp rate sections—as shown. In the embodiment shown, the ramp up portion  402  utilizes three different ramp rates  402 A,  402 B and  402 C prior separation of the droplet D. The first ramp rate  402 A is a very steep and rapid current increase so as to quickly heat the wire  140  so as to start the melting process as soon as possible. After the current reaches a first level  405 , the current ramp rate is changed to a second ramp rate  402 B which is less than the first ramp rate. In some exemplary embodiments, the first current level is in the range of 35 to 60% of the peak current level  413  for the pulse. The ramp rate  402 B is less than the initial ramp rate  402 A so as to aid in the control of the current and prevent the formation of an arc, or microarcs. In the embodiment shown the second ramp rate is maintained until the droplet D begins to form at the distal end of the wire  140 . In the embodiment shown, once the droplet D starts to form the current ramp rate is changed again to a third ramp rate  402 C which is less than the second ramp rate  402 B. Again, the decrease in the ramp rate is to allow for added control of the current so as to prevent the inadvertent creation of an arc. If the current was increasing too rapidly it can be difficult (because of various issues such as system inductance) to rapidly decrease the current when separation is detected and prevent the creation of an arc. In some exemplary embodiments, the transition point  407  between the second and third ramp rates is in the range of 50 to 80% of the peak current level  413  of the pulse  411 . Like the pulses in  FIG. 4A , the current is significantly reduced when the separation of the droplet is detected, which will be explained more fully below. It should also be noted that other embodiments of the present invention can use different ramp rate profiles without departing from the scope or spirit of the present invention. For example, the pulses can have two different ramp rate sections or can have more than three. Furthermore, the pulses can utilize a ramp up which is constantly changing. For example, the current can follow an inverse parabolic curve to the peak current level, or can utilize a combination of different configurations, where a constant ramp rate is used from wire contact to the first current level  405  and then an inverse parabolic curve can be used from that point. 
     As explained herein, the peak current levels of the pulses  401 / 411  is to be below an arc generation level, but sufficient to melt off the droplet D during each pulse. Exemplary embodiments of the present invention can utilize different control methodologies for the peak current level. In some exemplary embodiments, the peak current level can be a peak current threshold that is determined by various user input parameters that are input prior to the additive operation. Such parameters include, wire material type, wire diameter, wire type (cored v. solid) and droplets-per-inch (DPI). Of course, other parameters can also be utilized. Upon receiving this input information, the power supply  170  and/or the controller  195  can utilize various control methodologies, such as a look-up table, and determine a peak current value for the operation. Alternatively, the power supply  170  can monitor the output current, voltage, and/or power from the power supply  170  to determine when the separation will occur and control the current accordingly. For example, dv/dt, di/dt and/or dp/dt can be monitored (using a premonition circuit, or the like) and when separation is determined to occur the current is turned off or reduced. This will be explained in more detail below. 
     The following is a discussion of the use and operation of exemplary embodiments of the present invention. At the beginning of an additive manufacturing process the power supply  170  can apply a sensing voltage between the wire  140  and a workpiece  115  via the power source  170 . The sensing voltage may be applied by the power supply  170  under the command of the sensing and current controller  195 . In some embodiments, the applied sensing voltage does not provide enough energy to significantly heat the wire  140 . With the sensing voltage being applied, the distal end of the wire  140  is advanced toward the workpiece  115 . The laser  120  then emits a beam  110  to heat the surface of the workpiece  115  and create a puddle to receive the wire  140 . The advancing is performed by the wire feeder  150  and the contact with the workpiece is sensed when the distal end of the wire  140  first makes contact with the workpiece  115 . For example, the controller  195  may command the power supply  170  to provide a very low level of current (e.g., 3 to 5 amps) through the wire  140 . The sensing may be accomplished by the sensing and current controller  195  measuring a potential difference of about zero volts (e.g., 0.4V) between the wire  140  (e.g., via the contact tube  160 ) and the workpiece  115 . When the distal end of the filler wire  140  is shorted to the workpiece  115  (i.e., makes contact with the workpiece), a significant voltage level (above zero volts) may not exist between the filler wire  140  and the workpiece  115 . 
     After contact, the power source  170  can be turned off over a defined time interval (e.g., several milliseconds) in response to the sensing. Then the power source  170  can be turned back on at the end of the defined time interval to apply a flow of heating current through the wire  140 . Also, after contact is sensed the beam  110  can be turned off so as to not add too much heat to the puddle or the workpiece  115 . In some embodiments the laser beam  110  can stay on to aid in the heating and separation of the droplet D. This will be discussed in more detail below. 
     In some exemplary embodiments of the present invention, the process can include stopping the advancing of the wire  140  in response to the sensing, restarting the advancing (i.e., re-advancing) of the wire  140  at the end of the defined time interval, and verifying that the distal end of the filler wire  140  is still in contact with the workpiece  115  before applying the flow of heating current, or after the heating current is being applied and the droplet D is being formed. The sensing and current controller  195  may command the wire feeder  150  to stop feeding and command the system  100  to wait (e.g., several milliseconds). In such an embodiment, the sensing and current controller  195  is operatively connected to the wire feeder  150  in order to command the wire feeder  150  to start and stop. The sensing and current controller  195  may command the power supply  170  to apply the heating current pulses to heat the wire  140  as described above, and this process can be repeated to deposit multiple droplets on a workpiece. 
     During operation, the high intensity energy source (e.g., laser device  120 ) and the wire  140  can be moved along a workpiece  115  to provide the droplets as desired. The motion controller  180  commands the robot  190  to move the workpiece  115  in relation to the laser beam  110  and the wire  140 . The laser power supply  130  provides the power to operate the laser device  120  to form the laser beam  110 . In further embodiments, the laser device  120  includes optics that can be adjusted to change the shape of the laser beam  110  on the impact surface of the workpiece. Embodiments can use the beam shape to control the shape of the deposition process, that is by using a beam with a rectangular, elliptical or oval shape a relative narrow deposition can be made, thus making a thinner walled structure. Further, the beam shape can be used to shape the deposition after the droplet has separated from the consumable. 
     As discussed above, the pulse current is to be turned off or greatly reduced when it is determined that the break between the wire  140  and the droplet D is about to occur. This can be accomplished in a number of different ways. For example, such sensing may be accomplished by a premonition circuit within the sensing and current controller  195  measuring a rate of change of one of a potential difference between (dv/dt), a current through (di/dt), a resistance between (dr/dt), or a power through (dp/dt) the wire  140  and the workpiece  115 . When the rate of change exceeds a predefined value, the sensing and current controller  195  formally predicts that loss of contact is about to occur. Such premonition circuits are well known in the art for arc welding, and their structure and function need not be described in detail herein. 
     When the distal end of the wire  140  becomes highly molten due to heating, the distal end will begin to pinch off from the wire  140  onto the workpiece  115 . For example, at that time, the potential difference or voltage increases because the cross section of the distal end of the wire decreases rapidly as it is pinching off. Therefore, by measuring such a rate of change, the system  100  can anticipate when the distal end is about to pinch off and lose contact with the workpiece  115 . 
     As explained previously, when the separation of the droplet is sensed the current can be turned off or greatly reduced by the power supply  170 . For example, in some exemplary embodiments, the current is reduced to be in the range of 95 to 85% of the peak current value of the pulses. In exemplary embodiments, this current reduction occurs before separation between the wire and the puddle. 
     For example,  FIG. 5  illustrates an exemplary embodiment of a pair of voltage and current waveforms  510  and  520 , respectively, associated with an additive manufacturing process of the present application. The voltage waveform  510  is measured by the sensing and current controller  195  between the contact tube  160  and the workpiece  115 . The current waveform  520  is measured by the sensing and current controller  195  through the wire  140  and workpiece  115 . 
     Whenever the distal end of the wire  140  is about to lose contact with the workpiece  115 , the rate of change of the voltage waveform  510  (i.e., dv/dt) will exceed a predetermined threshold value, indicating that pinch off is about to occur (see the slope at point  511  of the waveform  510 ). As alternatives, a rate of change of current through (di/dt), a rate of change of resistance between (dr/dt), or a rate of change of power through (dp/dt) the filler wire  140  and the workpiece  115  may instead be used to indicate that pinch off is about to occur. Such rate of change premonition techniques are well known in the art. At that point in time, the sensing and current controller  195  will command the power supply  170  to turn off (or at least greatly reduce) the flow of current through the wire  140 . 
     When the sensing and current controller  195  senses that the distal end of the filler wire  140  again makes good contact with the workpiece  115  after some time interval  530  (e.g., the voltage level drops back to about zero volts at point  512 ), the sensing and current controller  195  commands the power supply  170  to ramp up the flow of current (see ramp  525 ) through the resistive filler wire  140  toward a predetermined output current level  550 . The time interval  530  can be a predetermined time interval. In accordance with an embodiment of the present invention, the ramping up starts from a set point value  540 . This process repeats as the energy source  120  and wire  140  move relative to the workpiece  115  and as the wire  140  advances towards the workpiece  115  due to the wire feeder  150  to deposit droplets at the desired locations. In this manner, an arc is prevented from forming between the distal end of the wire  140  and the workpiece  115 . Ramping of the heating current helps to prevent inadvertently interpreting a rate of change of voltage as a pinch off condition or an arcing condition when no such condition exists. Any large change of current may cause a faulty voltage reading to be taken due to the inductance in the heating circuit. When the current is ramped up gradually, the effect of inductance is reduced. 
     As explained previously, the power supply  170  provides a heating current to the filler wire  140 . The current passes from the contact tip  160  to the wire  140  and then into the workpiece. This resistance heating current causes the wire  140  between the tip  160  and the workpiece to reach a temperature at or near the melting temperature of the filler wire  140  being employed. Of course, the heat required to reach the melting temperature of the filler wire  140  will vary depending on the size and chemistry of the wire  140 . Accordingly, the heat to reach the desired temperature of the wire during manufacturing will vary depending on the wire  140 . As will be further discussed below, the desired operating temperature for the filler wire can be a data input into the system so that the desired wire temperature is maintained during manufacturing. In any event, the temperature of the wire should be such that the wire  140  can deposit a droplet into the puddle. 
     In exemplary embodiments of the present invention, the power supply  170  supplies a current which causes at least a portion of the distal end of the wire  140  at a temperature at or above 90% of its melting temperature. For example, when using a filler wire  140  having a melting temperature around 2,000° F., the temperature of the wire as it contacts can be approximately 1,800° F. Of course, it is understood that the respective melting temperatures and desired operational temperatures will vary on at least the alloy, composition, diameter and feed rate of the filler wire  140 . In further exemplary embodiments, portions of the wire are maintained at a temperature of the wire which is at or above 95% of its melting temperature. Of course, in some embodiments, the distal end of the wire is heated to at least 99% of its melting temperature by the heating current. Thus, when the heated droplet is in contact with the molten puddle created by the laser the heat from the puddle can add heat to the wire  140  so as to fully create the molten droplet at the end of the wire  140  so that the droplet is adhered to and stays with the puddle when the wire  140  is withdrawn. By maintaining the filler wire  140  at a temperature close to or at its melting temperature the wire  140  is easily melted into or consumed into the puddle created by the heat source/laser  120 . That is, the wire  140  is of a temperature which does not result in significantly quenching the puddle when the wire  140  makes contact with the puddle. Because of the high temperature of the wire  140  the wire melts quickly when in contact with the puddle. In other exemplary embodiments, the wire can be heated to at or above 75% of its melting temperature. However, when heating to a temperature near 75% it will be likely that additional heating will be necessary to make the droplet sufficiently molten to transfer, which is further discussed below. 
     As described previously, in some exemplary embodiments, the complete melting of the wire  140  can be facilitated only by entry of the wire  140  into the puddle. However, in other exemplary embodiments the wire  140  can be completely melted by a combination of the heating current, the puddle and the laser beam  110  impacting on a portion of the wire  140 . That is, the heating/melting of the wire  140  can be aided by the laser beam  110  such that the beam  110  contributes to the heating of the wire  140 . However, because many filler wires  140  are made of materials which can be reflective, if a reflective laser type is used the wire  140  should be heated to a temperature such that its surface reflectivity is reduced, allowing the beam  110  to contribute to the heating/melting of the wire  140 . In exemplary embodiments of this configuration, the wire  140  and beam  110  intersect at the point at which the wire  140  enters the puddle. This is shown in  FIGS. 6A and 6B . 
     As shown in  FIG. 6A , in some exemplary embodiments, the beam  110  can be used to aid in the deposition of droplets D onto the workpiece  115 . That is, the beam  110  can be used to add heat to the distal end of the wire  140  to create the molten droplet. In such embodiments, the heating current from the power supply can be kept at a level well below an arc generation level, thus ensuring that no arc will be created but proper droplet transfer can be achieved. In such embodiments the beam can be directed such that it only impacts the droplet D, or in other embodiments the beam  110  is large enough, shaped or rastered in a fashion that it impacts at least a portion of the droplet and at least some of the puddle to continue to add heat to the puddle to receive the droplet D. In exemplary embodiments of the energy density of the beam  110  during this phase of the process is typically less than the energy density of the beam when it is used to create the puddle on the workpiece  115 . 
       FIG. 6B  depicts other exemplary embodiments of the present invention, where the beam  110  at the wire  140  just above the droplet to aid in its separation from the wire. In such embodiments, when it is sensed or determined that the wire  140  is necking down above the droplet, a beam  110  is directed to the wire at the connection between the droplet D and the wire  140  such that the beam  110  aids in separating the two. Such embodiments aid in the prevention of an arc being generated because it is not needed to use the heating current to control the separation. In some exemplary embodiments the beam  110  can come from the same laser  120  that is used to create the puddle initially. However, in other embodiments, the beam in  FIG. 6B  can also be emitted from a second separate laser which is also controlled by the controller  195 . Thus, in such embodiments when the controller and/or power supply detects the formation of a droplet or the imminent separation of the droplet D, the output current of the power supply  170  can be dropped while the laser beam is directed to the wire  140  to cause the desired separation. 
     Turning now to  FIG. 7 , an exemplary embodiment of a heating system  700  and contact tip assembly  707  is shown. It is generally noted that embodiments of the present invention can utilize contact tips  160  and resistance heating systems that are known with respect to hot-wire or some welding systems, without departing from the spirit or scope of the present invention. However, in other exemplary embodiments, a system  700  as shown in  FIG. 7  can be utilized. In this system  700  the contact tip assembly is comprised of two conductive portions  701  and  703  which are electrically isolated from each by a insulation portion  705 , which can be made from any dielectric material. Of course, in other embodiments the insulation portion need not be present, so long as the tip portions  701  and  703  are electrically isolated from each other. The system  700  also includes a switching circuit  710  which switches the current path to/from the power supply  170  between the contact tip portion  701  and the workpiece  115 . In some embodiments, it may be desirable to maintain the wire  140  at some threshold temperature during the manufacturing process while the wire  140  is not in contact with the workpiece  115 . Without the wire  140  in contact with the workpiece  115  (e.g., during repositioning) no current will flow through the wire  140  and as such resistance heating will stop. Of course, residual heat will still be present but may degrade quickly. This embodiment allows the wire  140  to be continuously heated even though it is not in contact with the workpiece  115 . As shown, one lead from the power supply is coupled to the an upper portion  703  of the contact tip assembly  707 . During operation, when the wire  140  is in contact with the workpiece the switch  710  is positioned such that the current path is from the upper portion  703  through the wire  140  and the workpiece, returning to the power supply  170  (dashed line in switch  710 ). However, when the droplet D separates from the wire  140  and contact with the workpiece  115  is broken the switch  710  is switched such that the current path if from contact tip portion  703  to contact tip portion  701  and back to the power supply  170 . This allows at least some heating current to pass through the wire to continue to resistance heat the wire at some background heating level. Because of such a configuration, the wire can be heated to its desired deposition level quicker. This is especially the case if there has been a long duration between droplet depositions, during which the wire could cool. Thus, in exemplary embodiments the power supply  170  provides a current pulse or pulses (as generally described herein) to deposit droplets when the switch  710  is in a first position (first current path) which directs the current through the work piece, and then the power supply  170  provides a background or heating current (which can be constant current for example) when the switch is in a second position (second current path) that directs the current through both portions  701 / 703  of the contact tip to keep the wire heated in between droplet transfers. In some embodiments the switch can switch between each droplet transfer pulse, while in other embodiments the switch can switch after a plurality of droplet transfer pulses. In exemplary embodiments, the background/heating current level is selected to be a level which keeps the wire at a desired—non melting—temperature. If the temperature is too high it can become difficult to push the wire to the puddle. In some exemplary embodiments, the background/heating current is in the range of 10 to 70% of a peak current level reached during the droplet transfer pulses. 
     It is noted that in  FIG. 7  the switch  710  is shown external to power supply  170 . However, this depiction is just for clarity and the switch can be internal to the power supply  170 . Alternatively the switch can also be internal to the contact tip assembly  707 . The insulation portion  705  can be made from any insulation type material or can simply be an isolative gap between the components  701  and  703 . The switch can be controlled by the controller  195  (as shown) or can be controlled directly by the power supply  170  depending on the desired configuration. 
     In other exemplary embodiments, a wire preheating device can be positioned upstream of the assembly  707  which preheats the wire  140  before it enters the tip  707 . For example, the preheating device can be an induction heating device, which requires no current flow through the wire  140  to heat the wire  140 . Of course, resistance heating systems can also be used. This preheating device can be used to maintain the wire at a temperature as describe above. Further, the preheating can be used to also remove any undesirable moisture from the wire  140  before it is deposited (which is especially important when using Ti). Such preheating systems are generally known and need not be described in detail. The preheating device can be set to heat the wire  140  to a predetermined temperature before the wire enters the tip assembly  707 , thus allowing the current from the power supply  170  to be used to deliver enough current to complete the deposition process. It should be noted that the preheating device should heat the wire  140  to a level which compromises the wire  140  such that the wire  140  can be properly pushed through the tip  707 . That is, if the wire  140  is too hot it can become overly flexible, which can compromise the responsiveness of the wire  140  when being pushed. 
       FIG. 8A  depicts an exemplary manufacturing current waveform  800  that can be used with the system  700  in  FIG. 7 . In  FIG. 8A  a basic current waveform  800  is shown which comprises two components—a pulse portion  801  and a background portion  803 . The pulse portion is comprised of current pulses used to deposit droplets as discussed herein. During these pulses the current is directed from the tip portion  703  through the workpiece  115 . However, during the background portion the current is directed from the tip portion  703  to portion  701  to heat the wire  140  when it is not in contact with the workpiece  115 . Of course, it should be noted that the connections of the contact tip portions  701 / 703  to the positive and negative power supply terminals as shown in  FIG. 7  is exemplary and the connections can be reversed based on the desired system set up and performance. As explained previously, the background current level  803  between pulses  801  is used to keep the wire at a sustained temperature between droplet depositions. In some exemplary embodiments of the present invention, the background current keeps the wire  140  at a temperature which is in the range of 40 to 90% of the melting temperature of the wire  140 . In other exemplary embodiments, the current  803  keeps the wire  140  at a temperature in the range of 50 to 80% of the melting temperature of the wire  140 . 
     It is further noted that it may not be desirable or necessary to constantly switch to the background current between each pulse  801 . This could be particularly true during a high rate of droplet deposition. That is, during a high rate of droplet deposition, the wire  140  will be maintained at a high level of temperature between droplets. Thus, in some exemplary embodiments, the switching to the background heating current (as described above) occurs only after a time duration has expired or when the duration between droplet pulses exceeds a threshold time. For example, in some embodiments, if the time between pulses is to exceed 1 s the system  700  will use the switching and background heating current as described above. That is, if the manufacturing method utilized has a pulse frequency over a determined threshold frequency then the above switching will be used. In exemplary embodiments of the present invention, this threshold is in the range of 0.5 to 2.5 s between pulses. In other embodiments, the system  700  can utilize a timer (internal to the controller  195  and/or the power supply  170 ) which monitors the time between pulses and if the time exceeds a threshold amount the switching and background heating current described above will be utilized. For example, if the system  700  determines that a latency between pulses has exceeded a threshold time limit (for example, 1 s) then the background heating current will be utilized to keep the wire  140  at a desired temperature. Such an embodiment can be utilized in embodiments where the set threshold time has expired—that is, in real time the system  700  determines that the time limit has expired, or can be used when the system  700  predicts that the next pulse will not occur before the expiration of the time limit. For example, if the system  700  (e.g., controller  195 ) determines that the next pulse will not occur before the expiration of the time limit (for example, due to movement of the workpiece  115  and/or wire  140  then the system  700  can immediately initiate the switching and background heating current described above. In exemplary embodiments of the present invention, this duration threshold is in the range of 0.5 to 2.5 seconds. 
       FIG. 8B  depicts exemplary waveforms that can be used with exemplary embodiments of the present invention to deposit a droplet as described herein. The exemplary waveforms are for the transfer of a single droplet according to embodiments of the present invention. The waveforms shown are for laser power  810 , wire feed speed  820 , additive wire heating current  830 , and voltage  840 . It should be understood that the waveforms depicted are intended to be exemplary and other embodiments of the present invention can use other waveforms having different characteristics than shown or described herein. As shown, the droplet transfer cycle begins at  811 , where the laser power is directed at the workpiece and is increased  812  to a peak laser power level  813 . After a duration Tp the laser creates a puddle on the workpiece at point  814 . At this point the wire feeder starts to drive the additive wire towards the puddle. The wire feed speed increases  821  to a peak wire feed speed  822  after the puddle is created at  814 . In exemplary embodiments of the present invention, the wire feed speed reaches its peak level  822  at approximately the same time as the distal end of the wire makes contact with the puddle  821 ′. However, in other exemplary embodiments the wire feed speed can reach its peak level  822  prior to the wire making contact. As shown, at the same time the wire feeding process begins an open circuit voltage is applied to the wire  841  so that it reaches a peak voltage level  842  at some point prior to wire making contact with the puddle. Also, when the wire makes contact with the puddle the heating current  830  starts to flow (at point  831 ), and the voltage  840  begins to drop  843 . The voltage drops to a level  844  which is below an arc detection voltage  848 , above which it is determined that an arc would be created. 
     After the wire makes contact with the puddle the laser power  810 , wire feed speed  820  and current  830  are maintained at their respective peak levels for a period of time Ta, during which a droplet of the wire is deposited into the puddle. After the expiration of the deposition time period Ta (at  815 ), which can be for a predetermined period of time controlled by the heating power supply (for example, using a timer circuit), the laser power is ramped down  816 , along with the wire feed speed  823 . The heating current  830  is maintained at its peak level  833  for a period of time after the expiration of the time period Ta (top point  834 ) and while the laser power and the wire feed speed are being decreased. This aids in separating the droplet from the wire. After the droplet addition period Ta a wire retraction period Tr begins. After the current  830  starts its ramp down  835  (starting at point  834 ) the wire feed speed is reduced to zero (at point  827 ) and the wire feeder is controlled to retract the wire  824  at a peak retraction speed  825 . Also, during the retraction period the current  830  is reduced to a burnback current level  836  which is used to provide burnback of the wire as it is withdrawn from the puddle. During the wire retraction period Tr the current  830  is maintained at the burnback current level  836  until the voltage reaches or passes the arc detection voltage level  848  at point  845 , which is caused by the wire separating from the puddle (causing current to drop and voltage to increase). When the voltage level  848  is reached, an arc suppression routine  847  is initiated to prevent an arc from being generated. During this time, the voltage climbs to a peak level  846 . 
     The arc detection voltage level  848  is a predetermined level used by the power supply and/or system controller to ensure that no arc is generated between the retreating wire and the workpiece. The arc detection voltage level  848  is set by the power supply and/or system controller based on various user inputs, including, but not limited to, wire type, wire diameter, workpiece material type, droplet per inch input, droplet per minute input, etc. 
     When the arc detection voltage level  848  is reached (at  845 ) the current  830  is shut off by the power supply ( 837 ) and the retraction of the wire is stopped ( 826 ) and the droplet transfer cycle ends at point  817 , when the current  830  and wire feed speed  820  each reach 0. In the embodiment shown, the laser power  810  is also shown being shut off at the end of the cycle at point  817 . In other exemplary embodiments, the laser power  810  is shut off at the time the arc voltage threshold  848  is reached (at point  845 ). This cycle is then repeated for a plurality of droplet deposits. 
     In some exemplary embodiments, (not shown) a laser power pulse can be initiated between droplet transfer cycles (as shown In  FIG. 8B ) to aid in smoothing the workpiece or otherwise adding energy to the workpiece in between droplet transfers. For example, a laser power pulse can be initiated in between each droplet transfer cycle, or in other embodiments a laser power pulse can be initiated after a number n of droplet transfer cycles, as needed. 
       FIG. 9  depicts another exemplary system  900  of the present invention. The system  900  comprises a background power supply  170 ′ and a pulsing power supply  170 . This system operates very similar to that discussed above, except that the background heating current is supplied by a separate power supply  170 ′. Thus, in some embodiments the background power supply  170 ′ can provide a constant heating current during manufacturing and it is not necessary to provide the switching discussed above. The pulsing power supply  170  operates as described otherwise herein, except that its peak output current can be reduced because of the additional heating/current being provided by the power supply  170 ′. In such embodiments, the level of control or precision with the pulse power supply  170  can be increased. That is, the pulse power supply  170  can reach its peak pulse level quicker because of the lesser current demands on the power supply  170 . Of course, the same will be true in decreasing current. Each of the power supplies  170 / 170 ′ can be controlled by the controller  195 , or can be configured in a master/slave relationship, which is generally known. Furthermore, although these power supplies are shown separately for clarity, they can be housed within a single unit without departing from the spirit or scope of the present invention. 
     Also, shown in  FIG. 9  is another contact tip assembly  900 , having conductive portions  901  and  905  and insulation portion  903 . In this embodiment, the conductive portion  905  is configured such that the heating current is transmitted as close to the exposed distal end of the wire  140  as possible. Such a configuration helps to ensure that the heating of the wire is maintained as close to the distal end as possible, optimizing the effects of the background heating. In further embodiments, the stick out X of the distal end of the wire  140  from the contact tip  910  is kept to a minimum distance. If the stick out X is maintained too long the heating effects from the background heating current can be adversely affected. Thus, in some exemplary embodiments, the stick out X is maintained in the range of 0.1 to 0.5 inches. In other exemplary embodiments, the stick out is maintained in the range of 0.2 to 0.4 inches. Further, in additional exemplary embodiments, to obtain further benefits from the background heating, between droplet pulses the wire  140  is retracted fully, or near fully, into the contact tip  900 , such that the stick out X is in the range of 0 to 0.15 inch. Such embodiments are capable of keeping the distal end of the wire  140  at the desired background heating temperature without overheating other portions of the wire  140  not close to the distal end. In other exemplary embodiments, the stick out distance can be larger, particularly when using larger diameter consumables. For example, in some exemplary embodiments, the stick out distance can be in the range of 0.75 to 2 inches. Of course, in some other embodiments a longer stick out can be utilized. 
     Turning now to  FIG. 10 , another exemplary system  1000  is depicted, where the contact tip assembly  1010  is capable of delivering more than one wire  140 / 140 ′ to the workpiece  115 . In some additive manufacturing operations it may be desirable to utilize different wires for different portions of the manufacture. The system  1000  allows for the switching between different wires depending on what is desired for the manufacturing. Although not shown, each wire  140 / 140 ′ can be coupled to its own wire feeding apparatus to advance retract the respective wires  140 / 140 ′ as needed during manufacturing. Thus, during manufacturing the controller  195  can position the contact tip assembly  1010  such that the appropriate wire is to be used for the manufacturing. For example, it may be desirable to build a base with a first consumable  140  having first properties, and then add to that base a layer made with the wire  140 ′, having different properties to achieve a desired manufacturing result. For example, the wires  140 / 140 ′ can have different sizes, shapes, and/or composition based on the desired manufacturing parameters. It should also be noted that although the contact tip assembly is shown with only two wires  140 / 140 ′, embodiments of the present invention, can utilize a contact tip assembly, or separate contact tips to provide any number of varying consumables. Embodiments of the present invention are not limited in this regard. 
     Furthermore, the contact tip assembly  1010  in  FIG. 10  is shown such that the wires  140 / 140 ′ are not insulated from each other. In such an embodiment, the appropriate wire is advanced to the workpiece  115  for deposition, and as such the current from the power supply  170  will be directed through that wire—causing deposition. When the wire is to be changed, the other wire is advanced while the other is retracted such that the current path is now through the other wire. In other exemplary embodiments, the contact tip assembly  1010  can be constructed such that the wires  140 / 140 ′ are electrically isolated from each other. In such embodiments, switching, like that discussed regarding  FIG. 7 , can be utilized. In some exemplary embodiments, a laser beam (not shown in  FIG. 10 ) can affect or otherwise alter the energy distribution in the puddle between the wires  140  and  140 ′ by being scanned between the two wires. This 
     The positioning and movement of the contact tip assembly  1010  relative to the workpiece  115  can be effected by any number of means. Specifically, any known robotic or motion control systems can be used without departing from the spirit or scope of the present invention. That is, the appropriate wire  140 / 140 ′ can be positioned using any known means or methods, including robotic systems, and can be controlled by controller  195 . For example, the contact tip assembly  1010  can comprise three or more different wires and be constructed and utilized similar to known computer numerical control (CNC) machining heads which are rotated and positioned to allow for the utilization of appropriate tooling. Such systems and control logic can be utilized in embodiments of the present invention to provide the desired positioning of the desired wire. 
     The wires (or consumables) used with embodiments of the present invention are to have a size and chemistry as needed for a particular manufacturing operation. Typically, the wires have a circular cross-section, by other embodiments are not limited in this way. Other exemplary embodiments can utilize wires having a non-circular cross-section based on the manufacturing method and manufacturing process. For example, the wires can have a polygonal, oval, or elliptical shape to achieve a desired manufacturing criteria. Circular cross-section wires can have a diameter in the range of 0.010 to 0.045 inch. Of course, larger ranges (for example, up to 5 mm) can be used if desired, but the droplet control may become more difficult as the diameter increases. Because of the use of the laser and the heating control methodologies describe herein, embodiments of the present invention can provide very precise manufacturing. This is particularly true with embodiments that utilize smaller diameter wires, such as in the range of 0.010 to 0.020 inch. By using such small diameters a large DPI (droplets per inch) ratio can be achieved, thus providing highly accurate and detailed manufacturing. The chemistry of the wires is to be selected to provide the desired properties for the manufactured component. Further, the wire(s) utilized can either have a solid or metal-core configuration. Cored wires can be used to create a composite material construction. For example, a cored wire having an aluminum sheath and an aluminum oxide core can be used. 
     It is further noted that because no arc is used with the processes describe herein, most applications of the present invention will not require shielding gas of any kind. However, in some applications it may be desirable to use a shielding gas to prevent oxidation, or for other purposes. 
       FIG. 11  depicts yet another exemplary embodiment of the present invention.  FIG. 11  shows an embodiment similar to that as shown in  FIG. 1 . However, certain components and connections are not depicted for clarity.  FIG. 1  depicts a system  1100  in which a thermal sensor  1110  is utilized to monitor the temperature of the wire  140 . The thermal sensor  1110  can be of any known type capable of detecting the temperature of the wire  140 . The sensor  1110  can make contact with the wire  140  or can be coupled to the tip  160  so as to detect the temperature of the wire. In a further exemplary embodiment of the present invention, the sensor  1110  is a type which uses a laser or infrared beam which is capable of detecting the temperature of a small object—such as the diameter of a filler wire—without contacting the wire  140 . In such an embodiment the sensor  1110  is positioned such that the temperature of the wire  140  can be detected at the stick out of the wire  140 —that is at some point between the end of the tip  160  and the puddle. The sensor  1110  should also be positioned such that the sensor  1110  for the wire  140  does not sense the puddle temperature. 
     The sensor  1110  is coupled to the sensing and control unit  195  (discussed with regard to  FIG. 1 ) such that temperature feedback information can be provided to the power supply  170  and/or the laser power supply  130  so that the control of the system  1100  can be optimized. For example, the power or current output of the power supply  170  can be adjusted based on at least the feedback from the sensor  1110 . That is, in an embodiment of the present invention either the user can input a desired temperature setting (for a given manufacturing operation and/or wire  140 ) or the sensing and control unit  195  can set a desired temperature based on other user input data (electrode type, etc.) and then the sensing and control unit  195  would control at least the power supply  170  to maintain that desired temperature. 
     In such an embodiment it is possible to account for heating of the wire  140  that may occur due to the laser beam  110  impacting on the wire  140  before the wire enters the puddle. In embodiments of the invention the temperature of the wire  140  can be controlled only via power supply  170  by controlling the current in the wire  140 . However, as explained above, in other embodiments at least some of the heating of the wire  140  can come from the laser beam  110  impinging on at least a part of the wire  140 . As such, the current or power from the power supply  170  alone may not be representative of the temperature of the wire  140 . As such, utilization of the sensor  1110  can aid in regulating the temperature of the wire  140  through control of the power supply  170  and/or the laser power supply  130 . 
     In a further exemplary embodiment (also shown in  FIG. 11 ) a temperature sensor  1120  is directed to sense the temperature of the puddle. In this embodiment the temperature of the puddle is also coupled to the sensing and control unit  195 . However, in another exemplary embodiment, the sensor  1120  can be coupled directly to the laser power supply  130 . Feedback from the sensor  1120  is used to control output from laser power supply  130 /laser  120 . That is, the energy density of the laser beam  110  can be modified to ensure that the desired puddle temperature is achieved. 
     In yet a further exemplary embodiment of the invention, rather than directing the sensor  1120  at the puddle, it can be directed at an area of the workpiece  115  adjacent the puddle. Specifically, it may be desirable to ensure that the heat input to the workpiece  115  adjacent the deposition location is minimized. The sensor  1120  can be positioned to monitor this temperature sensitive area such that a threshold temperature is not exceeded adjacent the deposition location. For example, the sensor  1120  can monitor the workpiece temperature and reduce the energy density of the beam  110  based on the sensed temperature. Such a configuration would ensure that the heat input adjacent the deposition location would not exceed a desired threshold. Such an embodiment can be utilized in precision manufacturing operations where heat input into the workpiece is important. 
     In another exemplary embodiment of the present invention, the sensing and control unit  195  can be coupled to a feed force detection unit (not shown) which is coupled to the wire feeding mechanism (not shown—but see  150  in  FIG. 1 ). The feed force detection units are known and detect the feed force being applied to the wire  140  as it is being fed to the workpiece  115 . For example, such a detection unit can monitor the torque being applied by a wire feeding motor in the wire feeder  150 , and thus parameters related to the contact between the distal end of the wire  140  and the workpiece  115 . This, coupled with current and/or voltage monitoring, can be used to stop the feeding of the wire after contact is made with the puddle to allow for the separation of the droplet D. Of course, as indicated previously, the controller  195  can just use voltage and/or current sensing to detect contact between the wire  140  and the puddle and can use this information alone to stop wire feeding if desired when contact is made. 
     In a further exemplary embodiment, the sensor  1120  can be used to detect the size of the puddle area on the workpiece. In such embodiments, the sensor  1120  can be either a heat sensor or a visual sensor and used to monitor an edge of the puddle to monitor the size and/or position of the puddle. The controller  195  then uses the detected puddle information to control the operation of the system as described above. 
     The following provides further discussion regarding the control of the heating pulse current that can be used with various embodiments of the present invention. As mentioned previously, when the distal end of the wire  140  is in contact with puddle/workpiece  115  the voltage between the two can be at or near 0 volts. However, in other exemplary embodiments of the present invention it is possible to provide a current at such a level so that a voltage level above 0 volts is attained without an arc being created. By utilizing higher currents values it is possible to have the wire  140  reach high temperatures, closer to an electrode&#39;s melting temperature, at a quicker rate. This allows the manufacturing process to proceed faster. In exemplary embodiments of the present invention, the power supply  170  monitors the voltage and as the voltage reaches or approaches a voltage value at some point above 0 volts the power supply  170  stops flowing current to the wire  140  to ensure that no arc is created. The voltage threshold level will typically vary, at least in part, due to the type of wire  140  being used. For example, in some exemplary embodiments of the present invention the threshold voltage level is at or below 6 volts. In another exemplary embodiment, the threshold level is at or below 9 volts. In a further exemplary embodiment, the threshold level is at or below 14 volts, and in an additional exemplary embodiment; the threshold level is at or below 16 volts. For example, when using mild steel wires the threshold level for voltage will be of the lower type, while wires which are for stainless steel manufacturing can handle the higher voltage before an arc is created. Thus, such a system can monitor the voltage and control the heating current by comparing the voltage to a voltage set point, such that when the voltage exceeds, or is predicted to exceed the voltage set point, the current is shut off or reduced. 
     In further exemplary embodiments, rather than maintaining a voltage level below a threshold, such as above, the voltage is maintained in an operational range. In such an embodiment, it is desirable to maintain the voltage above a minimum amount—ensuring a high enough current to maintain the wire at or near its melting temperature but below a voltage level such that no arc is created. For example, the voltage can be maintained in a range of 1 to 16 volts. In a further exemplary embodiment the voltage is maintained in a range of 6 to 9 volts. In another example, the voltage can be maintained between 12 and 16 volts. Of course, the desired operational range can be affected by the wire  140  used for the manufacturing operation, such that a range (or threshold) used for an operation is selected, at least in part, based on the wire used or characteristics of the wire used. In utilizing such a range the bottom of the range is set to a voltage at which the wire can be sufficiently deposited in the puddle and the upper limit of the range is set to a voltage such that the creation of an arc is avoided. 
     As described previously, as the voltage exceeds a desired threshold voltage the heating current is shut off by the power supply  170  such that no arc is created. Thus, in such embodiments the current can be driven based on a predetermined or selected ramp rate (or ramp rates) until the voltage threshold is reached and then the current is shut off or reduced to prevent arcing. 
     In the many embodiments described above the power supply  170  contains circuitry which is utilized to monitor and maintain the voltage as described above. The construction of such type of circuitry is known to those in the industry. However, traditionally such circuitry has been utilized to maintain voltage above a certain threshold for arc welding. 
     As explained previously, the heating current can also be monitored and/or regulated by the power supply  170 . This can be done in addition to monitoring voltage, power, or some level of a voltage/amperage characteristic as an alternative. That is, the current can be driven to, or maintained, at a desired level to ensure that the wire  140  is maintained at an appropriate temperature—for proper deposition in the puddle, but yet below an arc generation current level. For example, in such an embodiment the voltage and/or the current are being monitored to ensure that either one or both are within a specified range or below a desired threshold. The power supply  170  then regulates the current supplied to ensure that no arc is created but the desired operational parameters are maintained. 
     In yet a further exemplary embodiment of the present invention, the heating power (V×I) can also be monitored and regulated by the power supply  170 . Specifically, in such embodiments the voltage and current for the heating power is monitored to be maintained at a desired level, or in a desired range. Thus, the power supply not only regulates the voltage or current to the wire, but can regulate both the current and the voltage. In such embodiments the heating power to the wire can be set to an upper threshold level or an optimal operational range such that the power is to be maintained either below the threshold level or within the desired range (similar to that discussed above regarding the voltage). Again, the threshold or range settings will be based on characteristics of the wire and manufacturing being performed, and can be based—at least in part—on the filler wire selected. For example, it may be determined that an optimal power setting for a mild steel electrode having a diameter of 0.045″ is in the range of 1950 to 2,050 watts. The power supply will regulate the voltage and current such that the power is driven to this operational range. Similarly, if the power threshold is set at 2,000 watts, the power supply will regulate the voltage and current so that the power level does not exceed but is close to this threshold. 
     In further exemplary embodiments of the present invention, the power supply  170  contains circuits which monitor the rate of change of the heating voltage (dv/dt), current (di/dt), and or power (dp/dt). Such circuits are often called premonition circuits and their general construction is known. In such embodiments, the rate of change of the voltage, current and/or power is monitored such that if the rate of change exceeds a certain threshold the heating current to the wire  140  is turned off. 
     In other exemplary embodiments of the present invention, the change of resistance (dr/dt) is also monitored. In such an embodiment, the resistance in the wire between the contact tip and the puddle is monitored. As explained previously, as the wire heats up it starts to neck down and this can create a tendency to form an arc, during which time the resistance in the wire increases exponentially. When this increase is detected the output of the power supply is turned off as described herein to ensure an arc is not created. Embodiments regulate the voltage, current, or both, to ensure that the resistance in the wire is maintained at a desired level. 
       FIG. 12  depicts an exemplary system  1200  which can be used to provide the heating current to wire  140 . (It should be noted that the laser system is not shown for clarity). The system  1200  is shown having a power supply  1210  (which can be of a type similar to that shown as  170  in  FIG. 1 ). The power supply  1210  can be of a known welding/heating power supply construction, such as an inverter-type power supply. Because the design, operation and construction of such power supplies are known they will not be discussed in detail herein. The power supply  1210  contains a user input  1220  which allows a user to input data including, but not limited to: wire type, wire diameter, a desired power level, a desired wire temperature, voltage and/or current level. Of course, other input parameters can be utilized as needed. The user interface  1220  is coupled to a CPU/controller  1230  which receives the user input data and uses this information to create the needed operational set points or ranges for the power module  1250 . The power module  1250  can be of any known type or construction, including an inverter or transformer type module. It is noted that some of these components, such as the user input  1220  can also be found on the controller  195 . 
     The CPU/controller  1230  can determine the desired operational parameters in any number of ways, including using a lookup table, In such an embodiment, the CPU/controller  1230  utilizes the input data, for example, wire diameter and wire type to determine the desired current level for the output (to appropriately heat the wire  140 ) and the threshold voltage or power level (or the acceptable operating range of voltage or power). This is because the needed current to heat the wire  140  to the appropriate temperature will be based on at least the input parameters. That is, an aluminum wire  140  may have a lower melting temperature than a mild steel electrode, and thus requires less current/power to melt the wire  140 . Additionally, a smaller diameter wire  140  will require less current/power than a larger diameter wire. Also, as the manufacturing speed increases (and accordingly the deposition rate) the needed current/power level to melt the wire may be higher. 
     Similarly, the input data will be used by the CPU/controller  1230  to determine the voltage/power thresholds and/or ranges (e.g., power, current, and/or voltage) for operation such that the creation of an arc is avoided. For example, for a mild steel electrode having a diameter of 0.045 inches can have a voltage range setting of 6 to 9 volts, where the power module  1250  is driven to maintain the voltage between 6 to 9 volts. In such an embodiment, the current, voltage, and/or power are driven to maintain a minimum of 6 volts—which ensures that the current/power is sufficiently high to appropriately heat the electrode—and keep the voltage at or below 9 volts to ensure that no arc is created and that a melting temperature of the wire  140  is not exceeded. Of course, other set point parameters, such as voltage, current, power, or resistance rate changes can also be set by the CPU/controller  1230  as desired. 
     As shown, a positive terminal  1221  of the power supply  1210  is coupled to the contact tip  160  of the system and a negative terminal of the power supply is coupled to the workpiece W. Thus, a heating current is supplied through the positive terminal  1221  to the wire  140  and returned through the negative terminal  1222 . Such a configuration is generally known. 
     A feedback sense lead  1223  is also coupled to the power supply  1210 . This feedback sense lead can monitor voltage and deliver the detected voltage to a voltage detection circuit  1240 . The voltage detection circuit  1240  communicates the detected voltage and/or detected voltage rate of change to the CPU/controller  1230  which controls the operation of the module  1250  accordingly. For example, if the voltage detected is below a desired operational range, the CPU/controller  1230  instructs the module  1250  to increase its output (current, voltage, and/or power) until the detected voltage is within the desired operational range. Similarly, if the detected voltage is at or above a desired threshold the CPU/controller  1230  instructs the module  1250  to shut off the flow of current to the tip  160  so that an arc is not created. If the voltage drops below the desired threshold the CPU/controller  1230  instructs the module  1250  to supply a current or voltage, or both to continue the manufacturing process. Of course, the CPU/controller  1230  can also instruct the module  1250  to maintain or supply a desired power level. Of course, a similar current detection circuit can be utilized, and is not shown for clarity. Such detection circuits are generally known. 
     It is noted that the detection circuit  1240  and CPU/controller  1230  can have a similar construction and operation as the controller  195  shown in  FIG. 1 . In exemplary embodiments of the present invention, the sampling/detection rate is at least 10 KHz. In other exemplary embodiments, the detection/sampling rate is in the range of 100 to 200 KHz. 
     In each of  FIGS. 1 and 11  the laser power supply  130 , power supply  170  and sensing and control unit  195  are shown separately for clarity. However, in embodiments of the invention these components can be made integral into a single system. Aspects of the present invention do not require the individually discussed components above to be maintained as separately physical units or stand-alone structures. 
     In some exemplary embodiments described above, the system can be used in such a fashion to combine cladding and droplet deposition as described above. That is, during the construction of a workpiece it may not always be required to have high precision construction, for example during the creation of a supporting substrate. During this phase of construction a hot wire cladding process can be used. Such a process (and systems) are described in U.S. application Ser. No. 13/212,025, which is incorporated herein by reference in its entirety. More specifically, this application is incorporated fully herein to the extent it described the systems, methods of use, control methodology, etc. used to deposit material using a hot-wire system in a cladding or other type of overlaying operation. Then, when a more precise deposition methodology is desired to construction the workpiece the controller  195  switches to a droplet deposition method, as described above. The controller  195  can control the systems described herein to utilize droplet deposition and cladding deposition processes as needed to achieve the desired construction. 
     Embodiments described above can achieve high speed droplet deposition. For example, embodiments of the present invention can achieve droplet deposition in the range of 10 to 200 Hz. Of course, other ranges can be achieved depending on the parameters of the operation. In some embodiments, the droplet deposition frequency can be higher than 200 Hz, depending on some of the parameters of the operation. For example, larger diameter wires will typically use a deposition frequency less than 200 Hz, whereas smaller diameter wires, such as in the range of 0.010 to 0.020 inch can achieve faster frequencies. Other factors that affect the droplet deposition frequency include laser power, workpiece size and shape, wire size, wire type, travel speed, etc. 
       FIG. 13  depicts another exemplary embodiment of the present invention, where a plurality of consumables can be deposited at the same time. In the embodiment shown four consumables are being deposited. However, embodiments are not limited in this regard as any number can be utilized. In such embodiments, the buildup of the workpiece can be accelerated as multiple consumables can be deposited in a single pass. As will be described further below, other advantages to such a configuration are also attained. 
     As shown in the exemplary system  1300 , a contact tip assembly  1305  houses a plurality of contact tips  1303 ,  1303 ′,  1303 ″,  1303 ′″, each of which deliver a consumable  140 ,  140 ′,  140 ″,  140 ″ (respectively) to the workpiece being created. In the shown embodiment, each of the contact tips are electrically isolated from each other such that each contact tip can receive a separate current waveform to be used for deposition. For example, as shown in the exemplary system  1300 , a power supply is electrically coupled to each contact tip so as to separately provide and control the current waveform for each consumable. As a note the system controller  195  is not shown in this Figure. However, the system  1300  can include a controller  195  as described previously herein to control the operation of each of the power supplies, as well as the operation. In the embodiment shown, a power supply system  1310  is shown having distinct individual power supply modules P.S. # 1  through P.S. # 4  ( 1311 ,  1312 ,  1313  and  1314 ), each of which is capable of outputting a distinct current to deposit the consumables. Each of the currents can be similar to the exemplary waveforms described herein, having different parameters, etc. Further, each of the power supplies  1311 - 1314  can be constructed and operated similar to the power supplies discussed herein with respect to  FIGS. 1 through 12 . In some exemplary embodiments, each of the power supplies  1311 - 1314  can be separate power supply modules in a single power supply system  1310 —for example being within a single housing. In other exemplary embodiments, each of the power supplies  1311 - 1314  can be separate and distinct power supplies, which can be linked to each other to synchronize, and otherwise control, their operation. 
     During operation, the system  1300  can create a workpiece on a substrate S by depositing multiple layers in a single pass. In the  FIG. 13  embodiment, each consumable  140 - 140 ′″ is creating a separate layer L# 1 , L# 2 , L# 3 , L# 4 , where each trailing consumable is creating a layer on top of the preceding layer. This is accomplished by having the tips  1303 - 1303 ′″ in line with each other in the travel direction as shown. During deposition, the leading consumable  140  is deposited onto the substrate S creating the first layer L# 1 , and the trailing consumable  140 ′ is deposited onto the previous layer L# 1 , to create a second layer L# 2 —and so on. To allow for the creation of the layers, at different heights, the contact tip assembly  1305  can position the contact tips are different heights relative to the substrate S surface. As shown in  FIG. 13 , the contact tips have a staggered or stepped formation to allow for the stacking of the layers. In other exemplary embodiments, the contact tips can be at the same level, relative to the surface, but the stick-out distance of the consumables can be adjusted appropriately to achieve the desired stacking of layers. 
     In exemplary embodiments of the present invention, the spacing between the consumables (in the travel direction) is such that the subsequent layers can be adequately constructed on the previously deposited layer. In exemplary embodiments, the spacing is such that the consumables are not deposited in the same puddle. That is, the trailing consumable does not make contact with the preceding puddle. However, the respective puddles are adjacent to each other on the workpiece. That is, in exemplary embodiments, while the puddles are adjacent or near to each other, their molten portions do not contact each other. Of course, the puddles can be at different elevation levels (see e.g.,  FIG. 13 ), and the temperature of the deposit between the puddles can be very high, but the molten portions are not contacting each other. 
     It is noted that although not shown in  FIG. 13 , the system  1300  can also use a laser or heat input system as described in the above exemplary embodiments. Specifically, the system  1300  can use a laser to create a molten puddle and/or aid in melting the consumable. In some exemplary embodiments, individual beams can be directed to each separate consumable deposition process and be controlled individually for each respective deposition process. The individual beams can be generated from separate laser emitting devices, or can come from a single laser emitting device, but is divided into separate beams via optics and laser splitters, etc. The deposition of each individual consumable  140  to  140 ′″ can be controlled as described previously. Alternatively, in other exemplary embodiments a single laser/heat source can be used which is rastered between consumables during the deposition process to provide the desired heat input for each consumable deposition process. For example, a laser beam can be rastered to the deposition of each consumable  140 - 140 ′″ and the interaction time at each consumable location is controlled to achieve the desired heat input for each deposition operation. 
     In exemplary embodiments of the present invention, the type, size and composition of the consumables  140 - 140 ′″ is chosen based on the desired properties of the workpiece. In some embodiments, each of the consumables  140 - 140 ′″ are the same, having the same diameter and composition. However, in other exemplary embodiments, the consumables can have different properties. For example, the consumables  140 - 140 ′″ can have different diameters, such that the layers L# 1 -L# 4  can be made with different widths, by using varying diameter consumables. Moreover, the consumables can have different compositions to allow for the creation of a workpiece having varying physical/compositional characteristics at different places. In such embodiments, the composition of a workpiece being manufactured can be changed “on the fly”. That is, a first material can be used to make certain portions of a workpiece—using some contact tips—and then without stopping the system can deposition a different or additional materials—as desired. 
     For example, exemplary embodiments of the present invention can be used to manufacture a structure or workpiece using a mixture of stainless steel and mild steel. Further, such structures can be built with a nickel material being added. Of course, these are simply exemplary and embodiments of the present invention allow for the mixture of multiple materials to be build a desired structure. In other exemplary embodiments, a band or layer of non-magnetic material/metal can be added to the workpiece for various reasons, including measurement of the workpiece. Differing materials can also be used to convert a material to an austenitic stainless steel. 
     In addition to varying properties/types of the consumables, embodiments of the present invention can deliver the consumables  140 - 140 ′″ with varying wire feed speeds. That is, in some embodiments, the wire feed speed for all of the consumables is the same. However, in other embodiments it may be desirable to vary the wire feed speeds. This can be done via the controller  195  and the respective wire feeding systems of the consumables (not shown for clarity). By varying the respective wire feed speeds, the physical properties of the workpiece being created can be affected. For example, it may be desirable to have at least one of the layers L# 1  to L# 4  thinner than the others. In such embodiments, the wire feed speed for the respective consumable of the thinner layer can be slowed, thus resulting in a thinner layer. 
     Moreover, in exemplary embodiments different current waveforms can be provided to the consumables  140 - 140 ′″. In the system  1300  shown there are separate power supply modules  1311 - 1314  providing the respective deposition currents to the consumables. In some embodiments, each of the currents can be the same, while in other embodiments the current waveforms can be different—having different frequencies, peak current levels, etc. This can be the case when using differing wire feed speeds and/or differing consumables to ensure proper deposition. 
     By varying aspects of the deposition of any of the consumables  140 - 140 ′″ the system  1300  provides significant flexibility in the creation of the layers L# 1 -L# 4 . That is, in exemplary embodiments any one, or a combination of, consumable type, composition, diameter, wire feed speed, and deposition current waveform can be varied, relative to another consumable, to achieve a desired property of a layer or the deposition process. Thus, embodiments of the present invention allow for the rapid construction or build-up of a workpiece with a significant amount of flexibility and precision in the construction of any layer or the deposition of a consumable. That is, different layers can have different thicknesses, widths, shapes, etc. based on the use of varying deposition/consumable properties. 
       FIG. 14  depicts another view of the system  1300  shown in  FIG. 13 . As shown, and discussed above, the contact tips  1303  and  1303 ′ are mounted to the contact tip assembly  1305  which orients, holds and moves the contact tips as desired. Further, as discussed above, the contact tips are held in a staggered or stepped pattern to allow for the creation of the layers on top of each other—as shown. In such embodiments, the stick-out X for each of the respective consumables  140 ,  140 ′ is maintained as generally the same distance. However, in other embodiments this need not be the case. That is, the stick-out distance X for each respective consumable  140 , 140 ′ can be varied to achieve a desired deposition performance. In fact, in some embodiments, the contact tips  1303 , 1303 ′ can be secured such that their respective distal end faces are co-planar with each other, relative to the surface of the substrate S. In such an arrangement the stick-out distance X of trailing consumables (e.g.,  140 ′) would be less than each preceding consumable (e.g.,  140 ) when layers L# 1 , L# 2  are being constructed as shown. 
     Further, as shown, in some embodiments the contact tips  1303 , 1303 ′ are movable within the contact tip assembly  1305 . In such embodiments, an actuator mechanism  1320 , such as rollers, an actuator, etc. can be used to move the contact tips  1303 , 1303 ′ in and out of the contact tip assembly  1305  to provide the desired stick-out and/or geometry of the workpiece being constructed. The actuators  1320  can also be controlled by the controller  195  (not in in  FIG. 14 ) such that the contact tips can be moved “on the fly” during a deposition process. For example, during deposition the relative height of the contact tips and/or stick out distance X of the consumables can be adjusted to achieve the desired geometry of the workpiece being manufactured. This movement can be created a number of ways as described above. For example, servos, motor control rollers, linear actuators, etc. can be used to move the contact tips as desired. Such control enhances the flexibility of the manufacturing capabilities of the system  1300 . 
     It is noted, that while  FIGS. 13 and 14  depict the contact tip assembly  1305  such that the consumables are in line in a travel/deposition direction, the contact tip assembly  1305  can also be positioned in a lateral configuration where the contact tips are in a line which is normal to the travel direction. That is, the contact tips can be side-by-side to provide a wide material deposition. In such an embodiment, the consumables are deposited adjacent to each other, rather than on top of each other as shown in the  FIGS. 13 and 14 . Of course, in other exemplary embodiments, the contact tip assembly  1305  can be oriented such that the contact tips are oriented at an angle relative to the travel direction. Embodiments of the present invention are not limited in this regard. 
       FIG. 15  depicts another exemplary embodiment, where the contact tip assembly  1305  is also rotatable relative to the travel direction of the deposition process. As shown in this top down view, in a first position A the consumable are deposited in line as shown in  FIGS. 13 and 14 . As the contact tip assembly  1305  continues to travel, it is rotated to a new position B such that the deposition of the layers changes shape, as shown. The contact tip assembly  1305  can be controlled and rotated by any known devices and methods, such as by using a step motor, motor, or any other known system (for example, those systems used in robotic welding to control/facilitate movement and rotation). The controller  195  can be used to control the rotation/movement of the contact tip assembly  1305  relative to the substrate S. By having the assembly  1305  rotatable, a shape of the workpiece can be created as needed. For example, a wall thickness of a workpiece can be increased/decreased as needed. Further, during the rotation of the assembly  1305  any one, or a combination of, the wire feed speed, the current waveform, stick-out and/or contact tip position of for any of the consumables can be adjusted. For example, as shown in  FIG. 15 , prior to position A only one of the consumables is being deposited to create the layer L# 1 , as shown. This can be the leading consumable in the assembly. As the assembly  1305  is turned, a second consumable  140 ′ begins being deposited for a second layer L# 2  such that the deposit L# 2  couples to and adds onto the first layer L# 1 . This can be down without adding undesired height, but just to increase the width of the workpiece being created. Similarly, the subsequent consumables  140 ″ and  140 ′″ can begin deposition similarly and sequentially as the assembly  1305  is rotated to the desired position B. Similarly, this motion can be used to create a ledge or overhang on the workpiece without the need for additional support for the overhang. In such embodiments, the rotation of the assembly  1305  and the adjustment of the deposition of any one, or all, of the consumables (as described above) can allow an overhang to be created relatively easily. For example, the adjustment of the feed rate and/or the stick out/contact tip depth positioning can allow for the creation of a ledge relatively simply. 
     Therefore, the system  1300  greatly increases the manufacturing flexibility of the additive manufacturing processes and systems described herein. 
       FIGS. 16, 17A -C and  18 A depict exemplary embodiments of a substrate  1600  that can be used with the methods and systems described herein. The substrate  1600  is electrically conductive—so as to provide for a current path for the deposition current/waveform—but also has a non-bonding surface  1610  such that it is relatively easy to remove a workpiece from the substrate  1600  after completion of the manufacturing process. 
     Typically, in additive manufacturing, the workpiece being constructed is placed on a substrate or surface which is conductive so as to provide a proper current path for the consumable heating current. However, because the substrate is conductive (i.e. metallic) the workpiece becomes bonded with the substrate. That is, during the initial manufacture of the workpiece, the initially created layers become adhered to the substrate via the deposition process. Because of this, an additional processing step is needed to remove the workpiece from the substrate and potentially remove some of the substrate material from the final workpiece. This adds additional processing as well as creates a potential risk of damage to the workpiece. It is understood by those of ordinary skill in the art that bonding between a workpiece and the substrate typically occurs when there is fusion between the workpiece and the substrate, such that the material from the workpiece mixes with the material of the substrate in an admixture zone on the substrate—consistent with joining technologies. Embodiments of the present invention address this issue. 
       FIG. 16  depicts an exemplary substrate  1600  which is made from a conductive material, which allows current to pass through it, but prevents the workpiece  110  from bonding to it. For example, in some exemplary embodiments the substrate can be made from copper or graphite, which are conductive but will not bond with aluminum or steel workpieces. In additional exemplary embodiments the substrate  1600  can be made as a matrix of a number of different materials. For example, the substrate  1600  can be made from a non-electrically conductive ceramic or clay material matrix material which has a conductive (e.g., metallic) material distributed within the ceramic or clay matrix so as to create a conductive path. As shown in  FIG. 16 , the non-conductive matrix  1603  has conductive particles  1605  distributed throughout it such an electrical current path can be made from the surface  1610  to a ground point  1625 —to which a lead from a power supply can be connected. In some exemplary embodiments, the substrate  1600  can be primarily ceramic with copper particles  1605  distributed throughout, having a sufficient amount of copper to provide a copper density that allows an electrical current to be transferred from the workpiece surface of the substrate to another location of the substrate, to which a ground or current cable is secured. The conductive material  1605 , which can be copper, can be in either a powder, granular, string or ribbon form. However, the conductive material should be distributed such that the an electrically conductive path is formed from the surface  1600  to the ground point  125 . The ground point  125  can be positioned anywhere on the substrate  1600 . It is noted that in some exemplary embodiments it is not necessary for the conductive material be distributed evenly throughout the entire substrate structure  1600  but it should be distributed sufficiently throughout the workpiece surface  1610  to provide for a current path from where a workpiece is positioned or started on the substrate surface  1610 . The matrix material  1603  can be any material, or combination of materials which will not bond with the workpiece. The materials can be non-conductive and have a high melting temperature so that the surface of the matrix  1603  will not melt during the formation of the workpiece on the surface. As indicated above, the matrix material can be any one of, or a combination of clay, ceramic. Other materials can include cast iron, with a high carbon content or any other alloy which would become brittle when the additive process is conducted on the surface. As described above, the additive process has a relatively low (if any) admixture, so propagation of the alloy from the substrate into the build will be minimal. However, the propagation can be such that the first layer of the build becomes brittle, while at the same time still being conductive. When the build is complete the user can then easily bend and break the brittle interface to separate the build from the substrate. As indicated above, a ceramic material can be used for the substrate. Such ceramics should have a high melting temperature, such as Al 2 O 3 , or other similar ceramics. In another example, an aluminum material or alloy can be used as a substrate for a mild steel build. 
     In a further exemplary embodiment, the substrate can be made from a metallic powder having a density such that the substrate provides the desired conductivity and physical support for the build workpiece. In such embodiments, the powder can be easily knocked away from the build piece once completed. In even further exemplary embodiments, the substrate can be comprised of a conductive layer (e.g., copper, carbon, iron, etc.) placed on a base of nonconductive material, such as ceramic, which may or may not have conductive materials within the base material. By using a thin layer on a base material, the penetration into the substrate can be minimized, thus ensuring that there is no bonding to the substrate. 
     As shown in  FIG. 16 , in some exemplary embodiments, the substrate  1600  can have a contact zone  1620  in which the conductive material is present and outside of which the conductive material is not present, or is present to a lesser extent so that the substrate  1600  is less or non-conductive outside of the contact zone  1620 . In such embodiments, the workpiece  110  is started or placed on the surface  1610  such that it contacts the contact zone  1620  to ensure sufficient electrical contact, as outside of the contact zone  1620  little or no electrical conductivity will exist. In such embodiments, the contact zone  1620  has an area which is less than the area of the surface  1610 . Further, the contact zone  1620  can be shaped in any desired shape. Thus, in exemplary embodiments, to begin an additive manufacturing process the process begins in the contact zone  1620  of the surface  1610  to ensure that a current path for the workpiece exists. As the workpiece  110  is constructed portions of the workpiece can be formed on the surface  1610  outside of the contact zone  1620  so long as the workpiece is made as an integral piece—thus having a constant current path. Thus, a current path will always be provided for the manufacturing process, and the workpiece  110  can be manufactured on a conductive surface  1610  which does not bond to the workpiece  110 , allowing for easy removal and processing of the workpiece. 
       FIG. 17A  depicts another exemplary embodiment where the substrate  1600  has a lattice  1630  of conductive material which creates a grid structure on the surface  1610  of the substrate  100 . The lattice  1630  is made from a conductive material, such as copper, is embedded in the material of the substrate  1600 , which can be ceramic, clay or other non-conductive materials. The lattice  1630  can be formed such that a grid structure is formed on the surface  1610  such that regardless of the size or orientation of the workpiece  110  to be formed, the workpiece will contact at least some of the lattice  1630  to provide the needed conductive path. The lattice  1630  is to have a mesh size to provide the desired spacing for the size of the workpieces that are to be made on the substrate  1600 . In some embodiments, the lattice  1630  can have a depth that goes through the substrate  1600 , while in other embodiments the depth of the lattice  1630  does not go all the way through the substrate  1600 . Further, the lattice structure  1630  is formed such that the structure is conductive throughout so that regardless of where a workpiece makes contact with the lattice structure  1630  there is an electrical path to the ground point  1625 . Further, in exemplary embodiments, the lattice structure  1630  can exist in the substrate  1600  only in a contact zone similar to that described with respect to  FIG. 16 . That is, the lattice structure exposed to the surface  1610  is only in a discrete area of the surface  1610  (i.e., contact zone) and the lattice is coupled to the ground point  1625 . In such embodiments, so long as some portion of the workpiece is in the contact zone and makes contact with a portion of the lattice  1630 , a current path exists to allow for the manufacture of the workpiece. Again, however, because most of the surface  1610  is non-conductive and non-bonding, the removal and processing of the workpiece is easy as compared to known substrates. 
       FIG. 17B  shows another exemplary embodiment of a substrate  1600  that can be used with devices described herein. In this embodiment, the substrate  1600  comprises a plurality of discrete ground points  1651 / 1652 / 1653 , etc. distributed through an area of the substrate  1600 . The points can be distributed in a pattern, such as a lattice pattern such that their respective locations are known to the controller of any system using the substrate. The ground points are made from a conductive material, and can be wires, pins, etc., and can pass through the substrate  1600  such that they each are also exposed on another surface of the substrate  1600 . In the embodiment shown in  FIG. 17B  the ground points pass through the substrate  1600  such that their other ends are exposed on the bottom surface of the substrate  1600 . In other embodiments, the other ends can come out of a side face, if desired. Each of the ground points  1651 ,  1652 ,  1653 , etc. are electrically coupled to a switching circuit  1660  which is also electrically coupled to the power supply of the system and to the controller, which controls the operation of ground switches within the circuit  1660  as described below. Because the location of the ground points are known, an additive process can be started on one of the ground points (e.g., point  1651 ) which serves as the initial ground path for the additive process. Once the process is started, the puddle can be moved along the surface  1610  until it reaches a next ground point  1652 . The switching circuit  1660  can allow the controller to switch the ground point of the build process to the nearest ground point to the ongoing additive process. That is, as the contact tip of the process is moved the ground point can be switched to provide the nearest ground path to the operation. Further, in other exemplary embodiments, the switching circuit  1660  can open up more than one ground paths—through a plurality of ground points—to increase the amount of current that can be used for the process. Further, in exemplary embodiments, the switching circuit  1660  can be used to steer the ground current path to different locations to control the deposition process. For example, as the build process nears an edge of the substrate  1600  the switch  1660  can switch to ground points which are closer to the center of the substrate  1660  to aid in controlling the deposition process and the puddle. This can also be used to aid in controlling the direction of an arc, to the extent any arc is initiated in the deposition process. 
       FIG. 17C  shows a further exemplary embodiment of the present invention, where the substrate  1600  further includes a conductor  1670  which electrically couples all of the ground points  1651 ,  1652 ,  1653 , etc., and the conductor  1670  is coupled to the power supply, to complete the ground path for the deposition current. In such embodiments, no switching circuit  1660  as described above need be used. In the embodiment shown, the conductor  1670  is a conductive plate or layer mounted to a surface of the substrate  1600 , to which all of the ground points are coupled. Of course, the conductor  1670  need not be on the bottom surface, but can also be on another surface of the substrate  1600 . During use, as the build structure contacts more than one ground point  1651 , etc., additional ground paths are provided to the conductor  1670 , again allowing more current to be used in the process. In either of the above embodiments, the controller/power supply used for the deposition process can control the deposition current level so as to not exceed an acceptable current level for any one ground point. That is, at the beginning of a build process, if only one ground point  1651  is being used, the current is controlled such that the current level does not exceed an acceptable level for a single ground point  1651 . To do so could cause damage to the ground point. However, as the build proceeds to additional ground points, the controller can cause the current level to rise because of the additional ground points contacted—because an increased number of ground paths to the conductor  1670 . Therefore, in such embodiments, because the controller knows the location of each of the ground points, the controller can then increase the current as multiple ground points are utilized. In such embodiments, the deposition current can be increased incrementally with the contact of each respective ground point, or can be increased in a single step when a suitable number of ground points is contacted. For example, for a deposition current of 200 amps the controller can determined (using stored information) that a minimum of 4 ground points are needed for such a current level. The controller/power supply can utilize a first, lower, current level (e.g., 50 amps) until at least 4 ground points are contacted, at which time the deposition current is increased to the optimal level. In other embodiments, the current can be increased in increments as each new ground point is contacted until the minimum needed ground points are contacted. For example, the current can increase by 50 amps for each subsequent ground point, until the desired deposition current level is reached. The current increase steps can be predetermined/preprogrammed in the controller of the system. 
     In exemplary embodiments of the present invention, the ground points are wires or pins having an average diameter which is larger than that of the wire diameter used. In exemplary embodiments, the ground points are pins having an average diameter of at least 20% larger than the largest wire diameter used. In some exemplary embodiments, the diameter is in the range of 20 to 80% larger than the diameter of the largest diameter wire. Further, as shown in  FIG. 17C  the pins can have a larger head area—as shown—for additional contact with a workpiece. That is, the pins can have a larger head area (e.g., like a nail, etc.) at the contact surface of the substrate—see, e.g.,  FIG. 17C . To the extent the pins  1651 , etc. have a shape as shown in  FIG. 17C , the larger head area is not considered in determining the average diameter of the pin as discussed above. 
     In further exemplary embodiments, the ground points  1651 , etc. (e.g., pins, wires, rods, etc.) are removable and replaceable within the substrate  1600 . For example, as shown in  FIG. 17C , the pins simply rest in holes in the substrate and act as the ground points described above. Through admixture the pins become secured to the workpiece as its built, and then upon completion the workpiece is removed, along with the secured pins. Then, the pins/rods, etc. can be removed via a machining process and new pins can be replaced in the substrate  1600  for the next process. The removable pins  1651 , etc. should be of a sufficient length so as to make contact with a workpiece being built on the substrate and the contact plate  1670 , so that a proper ground current path can be made. 
       FIG. 18A  depicts another exemplary embodiment of the present invention, where the substrate  1600  contains at least one cooling channel  1640  through which a cooling medium can be passed during manufacture of a workpiece, or at least during the initial manufacture of a workpiece. The cooling medium can be a gas or a liquid and is used to keep the substrate at a temperature such that no portion of the surface  1610  melts, or is otherwise adhered, to a workpiece. By cooling the substrate  1600  via the use of a cooling manifold/channel  1640 , the surface  1610  can be kept cool, and any electrically conductive materials on the surface  1610  (e.g., lattice structure, conductive particles, etc.) can be kept cool so that any layer of the workpiece formed on the surface  1610  will not melt, or otherwise bond with the electrically conductive components on the surface  1610 . Other embodiments, can use other cooling methods/processes without departing from the scope or spirit of the present invention. For example, passive heat pipes can be used. 
     Thus, in exemplary embodiments, a substrate is provided which provides the needed electrically conductivity but also provides a non-bonding surface such that the removal and processing of the workpiece after manufacturer is easier. 
       FIG. 18B  depicts yet another structure that can be used with the exemplary additive manufacturing processes described herein. The additive manufacturing processes described herein can be used to manufacture complex and delicate workpieces. The easy manufacture of components such as these can be aided by starting the manufacturing process from a non-horizontal traditional substrate or work surface. For example, it may be advantageous to manufacture the workpiece in a hanging configuration. That is, it may be easier to manufacture the workpiece where the initial layers/deposition of the workpiece layers are hanging such that they extend from a bottom of a substrate—as opposed to a traditional bottom up, flat surface substrate. The embodiment shown in  FIG. 18B  depicts an exemplary truss structure  1800  which can be used in these situations. The truss structure  1800  can have a plurality of support components  1810  and  1820  which are electrically coupled to each other—to allow for current flow. The truss structure  1800  is configured such that a workpiece can be started at any point on the structure  1800  as desired for a given workpiece. For example, if it is easier to manufacture a workpiece upside down, or from a top down process, the part can be started at a point on one of the members  1810  and  820  and built downward by the processes described herein. Of course, the truss structure and the torch/contact tips being used should be designed such that the tips can be properly positioned in the truss structure  1800 . The part can then be built from the structure  1810 / 1820  down to the surface of a substrate  1600  as needed. As shown the truss structure  1800  can have its own ground contact point  1825 , or can simply be electrically conductive throughout. Further, in some exemplary embodiments, the truss structure can have contact protrusions  1830  to which the beginning of a part or workpiece is secured to start a build operation. These protrusions  1830  act as contact nodes to which the beginning of a workpiece is started. These protrusions can make it easier to begin a manufacturing process and can make it easier to separate the final part from the truss structure—without damaging the manufactured part. The protrusions  1830  can be made integrally with the parts  1810 / 1820  of the structure  1800 . In other embodiments, the protrusions  1830  can be made of a different material and/or be easily separable from the structure. For example, the protrusions  1830  can be pins or other fastener type components having a head or protrusion portion to which a part can be secured and started for a manufacturing process. Upon completion the pins can be removed from the truss structure allowing for easy removal of the manufactured part. The truss structure  1800  can take any desired shape or configuration for a given manufacturing process. 
     In exemplary embodiments, the truss structure  1800  can be a metallic structure that allows for the transfer of the current to the substrate  1600 —which can be any of the embodiments described above. In other exemplary embodiments, the truss structure can be made of a non-bonding, but conductive material, as generally described above with respect to  FIGS. 16 and 17 . In any event, the structure  1800  should be constructed such that it can provide a current path to either the substrate  1600  or a ground point  1825  to allow for the proper flow of the heating current. 
       FIGS. 19A, 19B and 19C  depict exemplary embodiments of an additive manufacturing consumable  1900  that can be used with embodiments of the invention described herein. It is generally understood that large diameter solid consumables require more current/energy to melt the consumable. However, smaller diameter consumables require less current/energy to melt, such that a lesser amount of current/energy is needed to melt a plurality of smaller diameter consumables that have, collectively, the same cross-sectional area as a single larger diameter solid wire. Thus, the consumable used in some exemplary embodiments of the present invention is a braided consumable  1900  made up from a plurality of wires  1903  which are braided. In some embodiments, the wires  1903  are the same, having the same diameter and composition. However, in other exemplary embodiments, the wires  1903  can be different from each other. For example, in some embodiments, two different wire types can be used to make the braided consumable  1900 . In such an embodiment, the wires can different based on diameter and/or composition. For example the center wire can have a first diameter and composition and the perimeter wires  1903  have a second diameter and composition, both of which are different than the first diameter and composition. This allows for the use of a consumable  1900  that has customized properties for a particular manufacturing process. It should be noted that the methods and systems described herein to deposit solid or cored consumables can be used to deposit a braided consumable such as that shown in  FIG. 19A . 
     Further, in the embodiment shown in  FIG. 19A , the center wire  1903 ′ is a non-braided wire, and the outer perimeter of wires  1903  are braided around the center wire  1903 ′. The braid can be made in a generally helical pattern along the length of the consumable  1900 . 
     In some exemplary embodiments, the braiding of the consumable  1900  can be used to increase the relative wire feed speed of a consumable type. For example, as shown in  FIG. 19A  the center consumable  1903  can be of a first type/material, and the surrounding wires  1903  can be of a different type/material. Because the length of the surrounding (outside) wires is longer than the center wire, for a given length of the consumable  1900  the effective deposition rates of each of the respective wire types are different. The effective, relative deposition rate of different wires types can also be affected by the relative number of wire types in a given bundle. Thus, embodiments of the present invention allow for increased flexibility in the deposition chemistry. 
       FIGS. 19B and 19C  depict another exemplary embodiment of a consumable that can be used with embodiments of the present invention. However, unlike the consumable  1900  in  FIG. 19A , the consumables  1900  in  FIGS. 19B and 19C  have a void  1910  at the core of the consumable, where the core  1910  is surrounded by a plurality of braided wires  1903 . This hollow consumable construction allows the consumable  1900  to be squeezed and “shaped” during deposition so as to allow the deposition process to be customizable. This will be explained in more detail below. 
     The braiding of the wires  1903  which form the exterior of the consumable  1900  is done in a general helical pattern, similar to known wire braiding methodologies, but a void  1910  is maintained at the core of the consumable  1900 . Like in  FIG. 19A , the wires  1903  can have the same diameter and composition in some embodiments, while in other embodiments the wires  1903  can have different properties. An example of this is depicted in  FIG. 19C , where the braiding includes a first wire type  1903  having a first diameter and composition, and a second wire type  1905  having a second diameter and composition. Of course, in some embodiments, even though the diameters of the wires  1903 / 1905  are different, the compositions can be the same. As shown in  FIG. 19C , the different wires  1903 / 1905  alternate around the perimeter of the cross-section of the consumable  1900 . In further exemplary embodiments, the wires  1903 / 1905  can have different melting temperatures which can provide for customize deposition profiles and layering, as needed. 
     The void  1910  should be dimensioned such that the consumable  1900 ′ remains relatively stable in the deposition process. If the void is too large, the consumable can become unstable and will not maintain its integrity in the deposition process. In exemplary embodiments, the diameter of the void  1910  is in the range of 5 to 40% of the effective diameter of the consumable  1900 ′. The “diameter of the void”  1910  is the diameter of the largest circular cross-section that can be fit within the void  1910 —as shown in  FIG. 19C  as the dashed circle. The “effective diameter” of the consumable  1900 ′ is the diameter of a circle having the same cross-sectional area of the combined cross-sectional area of all of the wires  1903 / 1905  that make up the consumable  1900 ′. 
     As indicated above, the consumable  1900  having a center void  1910  can be shaped during the deposition process to allow for changing of the deposition characteristics of the consumable. This is generally depicted in  FIGS. 20A and 20B , where the consumable  1900  has been squeezed in a direction relative to the travel direction of the consumable to achieve the desired width of the deposition. As described herein process and systems of the present invention can be used to make complex shapes via additive manufacturing. Thus, workpieces and shapes having varying thicknesses, etc. can be made. The consumable  1900  shown in  FIGS. 19B and 19C  allow these complex shapes and differing thicknesses to be easily made due to the void. In  FIG. 20A  the consumable is squeezed in a direction normal to the travel direction which narrows the consumable  1900  relative to the travel direction. By doing this, the resultant deposition will be narrower than the original diameter of the consumable. Similarly,  FIG. 20B  depicts the same consumable  1900  being squeezed in a direction along the travel direction, which results in widening the consumable  1900  relative to the travel direction. As such, with such squeezing a wider deposit can be made as needed. As stated above, the void  1910  should be of a size/diameter that allows for the deformation of the consumable  1900  to change its relative width as compared to its non-compressed state. 
     In some exemplary embodiments, the void  1910  can be filled with a flux or powder of a desired chemistry that is needed for the deposition. This can aid in delivering a desired material to the build that is not easily made into wire, or transferable through the melting of the wire. For example, an abrasion resistant powder can be added as a flux. 
       FIG. 20C  depicts another exemplary embodiment of a contact tip assembly  2000  and consumable delivery system and method that can be used with embodiments of the present invention. In this embodiment, at least two consumables  2010  and  2020  are directed to the contact tip assembly  2000  and the contact tip  2040 , which has an orifice  2030  that allows both consumables to pass through. Unlike the above embodiments, the consumables  2010  and  2020  are not braided. They can be delivered from the same consumable source (spool, reel, etc.) or can be delivered from separate sources. Further, they can be the same consumable, having the same dimensions and composition, or can be different as desired for a given manufacturing operation. In further exemplary embodiments, the consumables  2010  and  2020  can be fed at different rates, and in some embodiments, the feed rates can be changed “on the fly” during a deposition process. Such embodiments, allow for the customization of alloys for the build during the deposition process. For example, during a first portion of the process the consumables  2010  and  2020  are fed at the same rate, but at different stages of the build process the consumable  2010  is slowed down or sped up as needed to create the desired deposit chemistry. 
     Further, while two consumables are shown, other embodiments can use three or more as needed. In the embodiment shown, the consumables  2010  and  2020  are delivered to the orifice  2030  (which can be oval shaped, or any other shape to accommodate the consumables) and are then directed to the workpiece as with known consumable delivery systems. During deposition, the contact tip  2040  is oriented such that the consumables provide the desired deposition profile. Further, the contact tip  2040  is rotatable (as above described embodiments) to allow the consumables to be oriented as designed and have the shape or profile of the deposition process to be changed as desired. For example, as shown, the orientation on the left shows an in-line orientation which will provide a narrow deposit on the workpiece, but with an increased height as the consumables are in-line in the travel direction. Then, as needed, the contact tip  2040  can be rotated to the position shown on the right. The rotation can be effected by the controller  195  and motors, etc., and can be used during changes in deposition direction, without the need to change the orientation of the torch. The positioning on the right can be used when it is desired to increase the width of the deposit—in the travel direction. It is also noted that in some embodiments, it may not be necessary to feed both consumables  2010  and  2020  at the same time. In such embodiments, the consumables  2010  and  2020  would be fed by separate wire feeders (not shown) and the controller  195  can control which one of the consumables is being fed, or whether they are fed at the same time. In such embodiments, the consumable not being fed need not be withdrawn from the orifice  2030  and can thus be used to maintain the positioning of the consumable which is being fed. In such embodiments, the feeding of the consumables can be controlled by the controller  195 —which will feed either one, or both, of the of the consumables as needed at a given moment during the process. 
     Further, in the embodiment shown in  FIG. 20C , each of the consumables  2010  and  2020  are sharing the same current, as they are being directed through a single orifice  2030 . In such embodiments, the current can come from a single power source, and the current is shared by each consumable. However,  FIG. 20D  depicts a different exemplary embodiment. In the embodiment shown in  FIG. 20D  the contact tip assembly  2000  contains two electrically isolatable contact tip portions  2015  and  2025 . The tip portions  2015  and  2025  deliver the consumables  2010  and  2020 , respectively. However, the assembly  2000  contains a switching device or mechanism  2050  which can electrically couple the tip portions  2015  and  2025  to each other such that they share a current, or can electrically isolate the tip portions from each other. In an exemplary embodiment, each of the tip portions  2015  and  2025  are coupled to a separate power supply (PS# 1  and PS# 2 ). When the switch  2050  is in an open position, each respective power supply can provide a separate and distinct heating current to the respective consumables. In such embodiments, the consumables can be deposited at different rates, and or can be different in size and composition. This can be controlled and used as similar embodiments described above using multiple consumables. However, in this embodiment, as needed the controller  195  can close the switch, at which time the contact tip portions  2015  and  2025  become electrically coupled and can share a single current signal from one of the power supplies P.S. # 1  or P.S. # 2 . In such embodiments, it may only be needed to run a single power supply for a given operation, to reduce power usage and or eliminate the need for synchronizing signals. In such embodiments, the switch  2050  can be closed such that each of the tip portions  2015  and  2025  can now be coupled to each other so that the consumables  2010  and  2020  share the same signal from a single source. When the switch  2050  is opened the tip portions are electrically isolated from each other (via a dielectric material or other appropriate means), and if both consumables are to be deposited they would receive separate signals from separate power supplies. Alternatively, at some point during a deposition operation it may be only needed that a single consumable need be deposited. Thus, only one power supply is operated, but the switch  2050  is opened to isolated the other consumable for safety purposes. The switching mechanism  2050  can be any switch structure which is capable of isolating and connecting the tip portions  2015  and  2025 , and can be integral to the tip assembly  2000 , or can be remote from the assembly  2000 , as desired. 
     Turning now to  FIGS. 21A and 21B , a diagrammatical view of a representative contact tip assembly  1950  is shown using the consumable  1900  of  FIG. 19B .  FIGS. 21A and 21B  show a view looking up at the exit portion of the contact tip assembly  1950 , where  FIG. 21A  depicts the consumable in a non-compressed state and  FIG. 21B  depicts the consumable  1900  in a compressed state. It should be noted that the following description of the contact tip assembly  1950  is intended to be exemplary and those of skill in the art understand that other configurations and designs can be used to shape the consumable  1900  as desired to achieve the desired deposition during an additive manufacturing process. 
     As shown, the contact tip assembly  1950  has a consumable opening  1951  through which the consumable passes. While the opening  1951  is shown as square, embodiments of the present invention are not limited in this regard and other shapes can be used so long as the consumable  1900  can pass through in both its compressed and non-compressed state. In the embodiment shown, the assembly  1950  has two pairs of contact plungers  1953  and  1955 . The plungers are movable relative to the opening  1951 , as shown, such that they can extend into the opening and thus apply a compression force on the consumable  1900 . The contact plungers  1953  and  1955  are oriented such that one pair of plungers  1953  are moveable in a direction normal to the direction of movement of the other set of plungers  1955 . Thus, as shown in  FIG. 21B  the plungers  1953 / 1955  can squeeze the consumable  1900  in a desired direction to attain the desired shape. Each set of plungers can be moved via known actuation devices  1956 , such as linear actuators, etc. and can be controlled by the controller  195  (not shown in these figures). Further, each of the plungers  1953 / 1955  are configured to provide the heating current waveform to the consumable  1900  such that the heating current is delivered to the consumable  1900  via the plungers. It is noted that although one actuator  1956  and bias  1957  are shown in the Figures, exemplary embodiments would have similar components for each of the plungers. 
     As shown in  FIG. 21A , during a non-compressed state, each of the plungers  1953 / 1955  make contact with the consumable  1900  to deliver the heating current. The plungers  1953 / 1955  are held at a position, relative to the opening  1951 , to ensure that consumable  1900  is maintain in its natural state. Then, during deposition, it is determined (for example, by the controller) that a width of the consumable should be changed to achieve a desired deposition configuration—either the consumable should be made wider or narrower, as needed. Based on this information, the controller  195  causes the plungers  1955  to be actuated (via actuators  1956 ) and moved inward to compress the consumable  1900  as shown in  FIG. 21B . Additionally, to accommodate the change in shape of the consumable  1900  the plungers  1953  are withdrawn to allow the shape of the consumable to change. However, in exemplary embodiments, the withdrawn plungers  1953  still make contact with the consumable  1900  to hold the consumable  1900  at the proper position and to deliver the heating current. 
     During the deposition process, the shape of the consumable  1900  can be changed “on the fly” by moving the plungers to achieve the desired shape. For example, the controller  195  can control the plungers  1953 / 1955  to retract and extend as needed during the deposition to change the shape of the consumable  1900  to go from a wide deposition to a narrow deposition and back again, without stopping the deposition process. 
     As stated above, the movement/actuation of the plungers  1953 / 1955  can be effected by any known actuators, movement devices to effect the desired motion. In some exemplary embodiments, (not shown here) each plunger in the respective pair of plungers can be mechanical linked to each other such that their relative motions are maintained consistent with each other. In such embodiments, rather than having a separate actuator for each plunger, a single actuator can be used for each respective pair, and because of a mechanical linkage each of the plungers will move appropriately. 
     Further, as indicated above, the controller  195  can control the actuation of the plungers based on a desired shape to be constructed. In further exemplary embodiments, the assembly  1950  can be rotated as desired during the deposition operation to achieve a desired shape. That is, the assembly  1950  can be coupled to a rotation motor and/or robotic arm (or other similar motion device) and the controller  195  (or other system controller) can cause the assembly to rotate as needed, and have any of the plungers activated to achieve the desired consumable, and thus deposition, shape. 
       FIG. 22  depicts another exemplary embodiment of a consumable  2000  that can be used with exemplary embodiments of the present invention. The consumable  2000  includes a similar braided structure of wires  2003  with a space  2010  as described above, but also includes a sheath  2015 . The sheath  2015  can be constructed and formed similar to known sheath structures used for welding or brazing consumables. As shown, in this embodiment, the sheath  2015  complete encloses the wires  2003  and has a seam  2017 , which is a butt seam. The sheath  2015  can be made of any material desired to deposited on the work piece. In some embodiments the sheath  2015  can be the same material as the wires  2003 , while in other embodiments the sheath can be made of a different material/have a different composition. The sheath  2015  can also aid in the consumable  2000  maintaining its shape after it is reformed by the plungers in the contact tip assembly of  FIGS. 21A and 21B . Specifically, the squeezing of the wire through the orifice  1951  will cause the sheath  2015  to plastically deform, thus causing the consumable  2000  to hold the desired shape more easily. This can allow for the stick out of the consumable  2000  to be increased during a deposition process. 
       FIG. 23  depicts another exemplary consumable  2100  that can be used with embodiments of the present invention. The consumable  2100  contains a sheath  2110  and a core  2120 , where the sheath  2110  has a lower melting temperature than the core  2120 . By having such a divergent melting temperature, embodiments of the consumable  2100  can provide increased control over the manufacturing of a component. In embodiments where the consumable melts at the generally same temperature throughout, the dynamics of the molten puddle created play an important role in the deposition and build process. In certain instances the controlling of the puddle can be difficult, particularly in high precision manufacturing processes, or where the thickness of the workpiece being constructed is very thin. In such applications the puddle dynamics can be hard to control and account for. However, when using the consumable  2100  the sheath  2110  melts prior to the core  2120 . The molten sheath material then provides a molten matrix to adhere the core material to the workpiece. In such applications the importance of the puddle is decreased and in some instances, the puddle can be eliminated. Further, in alternative embodiments, the size and/or depth of the puddle can be reduced as the puddle and molten sheath material will work together to adhere the core material to the workpiece. As such, the dynamics of the puddle can be less important when using the consumable  2100 . 
     In exemplary embodiments the core  2120  can be a solid core, while in other embodiments the core  2120  can be powder or particles of a desired material. In such embodiments, the consumable  2100  can be shaped (as discussed above) to achieve a desired deposition. That is, because the core  2120  can be powder or granular, the exterior of the consumable  2100  can be shaped and squeezed to achieve a desired consumable profile. In additional embodiments the consumable can be constructed like that shown in at least  FIG. 22 , where the sheath surrounds a plurality of individual wires, and where at least some (or all) of the wires  2003  have a melting temperature which is higher than the sheath  2015 . In fact, in some of such embodiments, the wires  2003  can have different melting temperatures relative to each other. For example, a first number of the wires  2003  can have a first melting temperature (higher than the sheath melting temperature) and a second number of the wires  2003  can have a melting temperature which is either higher or lower than the melting temperature of the first number of wires  2003 . Such embodiments can provide increased flexibility in the melt and build profile of the consumable. Further, in some embodiments the heat source (e.g. laser) and/or current are controlled such that at least some of the core  2120  is also melted during the deposition process. However, in other embodiments, the material of the core  2120  is not melted during the deposition process. That is, the sheath  2110  is melted, and the liquid sheath material is used to secure the unmelted core material to the workpiece. In such embodiments, the workpiece is created in layers, alternating between the molten sheath material and the core material. It is noted that although  FIG. 23  depicts the consumable  2100  as having a circular cross-section, embodiments of the present invention are not limited in this regard. The consumable  2100  can also have any desired shape which benefits the construction of the workpiece as desired. For example, the consumable  2100  can have a square, rectangular, polygonal, or elliptical cross-section. Of course, other shape s can be used as well. 
     In exemplary embodiments, the materials of the sheath  2110  and the core  2120  are selected such that the sheath  2110  melts at a temperature which is in the range of 5 to 45% lower than that of the core material. In further exemplary embodiments, the melting temperature of the sheath  2110  is in the range of 10 to 35% lower than that of the core material. Of course, the exact composition of the materials for each of the sheath and the core are to be selected based on the desired composition and construction of the workpiece being built. 
       FIG. 24A  depicts another exemplary embodiment, where the consumable  2200  has a non-circular cross-section and the sheath material  2210  does not extend around the entire perimeter of the consumable  2200 . That is, the consumable  2200  has an asymmetric cross-section. For example, in the embodiment shown the sheath material  2210  is only position on one side of the core material  2220  of the consumable.  FIG. 24B  depicts another such exemplary embodiment, where the overall shape of the consumable is an hexagon and the sheath material  2210 ′ covers only 5 sides of the hexagonal cross-section of the core  2220 ′. Of course, other shapes and coverages can be used based on the desired performance and deposition properties of the consumable.  FIG. 24C  is another exemplary embodiment, which shows a consumable  2200 ″ having a symmetric cross-section, but the distribution of the sheath material  2210 ″ and the core material  2220 ″ is not symmetrical. This configuration allows the consumable to be used with contact tips and equipment designed for typical symmetric consumables, but the consumable itself is asymmetric. In such embodiments, the sheath material  2210  melts and provides adhesion for the core portion  2220  of the consumable, but does not melt from all around the consumable. In such embodiments, the consumable can be oriented as desired prior to adhesion during the deposition process. The sheath material acts as an adhesion material which binds or bonds the core material to the workpiece. Further, in such embodiments, the current/heat input is controlled to ensure the desired melting of the sheath material is attained without fully melting the core material. 
       FIG. 24D  is a further exemplary embodiment of a consumable  2200 ′″ that can be used with embodiments of the present invention. The consumable  2200 ′″ is similar to those discussed above, except that the sheath layer  2210 ′″ has a layered construction. In such embodiments, the sheath layer  2210 ′″ can be either a solid material or can be a flux. In fact, in any of the embodiments, discussed above, the sheath layer can be a flux, and not be a solid metallic sheath. In those embodiments, in some applications, it may be desirable to place a material within the flux sheath that should not be melted during the deposition process (or the melting is to be minimized). To achieve this, some embodiments use a layered sheath/flux  2210 ′″ where the composition of the flux against the surface S of the core  2220 ′″ is different than the chemistry of the flux at the outer edge of the flux. This is shown in  FIG. 24D  as layers A and B, where layer A has a first composition and layer B has a second composition. The creation of these layers can use known deposition techniques, which need not be discussed herein. This type of construction allows materials in the layer B to be removed from direct heat in the core  2220 ′″ which would otherwise melt components in the layer B. For example, it may be desirable to deposit tungsten carbide in the puddle, which could be susceptible to melting if they were in direct contact with the core  2220 ′″. In this embodiment, the layer A acts as a heat buffer, allowing the materials of layer B to be deposited with little or no melting. Of course, it should be understood that the delineation between the two layers A and B need not be a clear, precise line, but can be a transition from one composition to another. Further, the shape and relative cross-sectional area of the layer B, relative to the layer A, can be determined based on the desired composition of the application.  FIG. 24D  is shown as an exemplary embodiment and other shapes and configurations can be used without departing from the spirit or scope of the present invention. 
     A user interface coupled to a computer illustrates one possible hardware configuration to support the systems and methods described herein, including the controller  195 , or similar system used to control and/or operate the systems described herein. In order to provide additional context for various aspects of the present invention, the following discussion is intended to provide a brief, general description of a suitable computing environment in which the various aspects of the present invention may be implemented. Those skilled in the art will recognize that the invention also may be implemented in combination with other program modules and/or as a combination of hardware and software. Generally, program modules include routines, programs, components, data structures, etc., that perform particular tasks or implement particular abstract data types. 
     Moreover, those skilled in the art will appreciate that the inventive methods may be practiced with other computer system configurations, including single-processor or multiprocessor computer systems, minicomputers, mainframe computers, as well as personal computers, hand-held computing devices, microprocessor-based or programmable consumer electronics, and the like, each of which may be operatively coupled to one or more associated devices. The illustrated aspects of the invention may also be practiced in distributed computing environments where certain tasks are performed by remote processing devices that are linked through a communications network. In a distributed computing environment, program modules may be located in both local and remote memory storage devices. 
     The controller  195  can utilize an exemplary environment for implementing various aspects of the invention including a computer, wherein the computer includes a processing unit, a system memory and a system bus. The system bus couples system components including, but not limited to the system memory to the processing unit. The processing unit may be any of various commercially available processors. Dual microprocessors and other multi-processor architectures also can be employed as the processing unit. 
     The system bus can be any of several types of bus structure including a memory bus or memory controller, a peripheral bus and a local bus using any of a variety of commercially available bus architectures. The system memory can include read only memory (ROM) and random access memory (RAM). A basic input/output system (BIOS), containing the basic routines that help to transfer information between elements within the computer, such as during start-up, is stored in the ROM. 
     The controller  195  can further include a hard disk drive, a magnetic disk drive, e.g., to read from or write to a removable disk, and an optical disk drive, e.g., for reading a CD-ROM disk or to read from or write to other optical media. The controller  195  can include at least some form of computer readable media. Computer readable media can be any available media that can be accessed by the computer. By way of example, and not limitation, computer readable media may comprise computer storage media and communication media. Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile disks (DVD) or other magnetic storage devices, or any other medium which can be used to store the desired information and which can be accessed by a user interface coupled to the controller  195 . 
     Communication media typically embodies computer readable instructions, data structures, program modules or other data in a modulated data signal such as a carrier wave or other transport mechanism and includes any information delivery media. The term “modulated data signal” means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared and other wireless media. Combinations of any of the above should also be included within the scope of computer readable media. 
     A number of program modules may be stored in the drives and RAM, including an operating system, one or more application programs, other program modules, and program data. The operating system in the computer or the user interface  300  can be any of a number of commercially available operating systems. 
     In addition, a user may enter commands and information into the computer through a keyboard and a pointing device, such as a mouse. Other input devices may include a microphone, an IR remote control, a track ball, a pen input device, a joystick, a game pad, a digitizing tablet, a satellite dish, a scanner, or the like. These and other input devices are often connected to the processing unit through a serial port interface that is coupled to the system bus, but may be connected by other interfaces, such as a parallel port, a game port, a universal serial bus (“USB”), an IR interface, and/or various wireless technologies. A monitor or other type of display device, may also be connected to the system bus via an interface, such as a video adapter. Visual output may also be accomplished through a remote display network protocol such as Remote Desktop Protocol, VNC, X-Window System, etc. In addition to visual output, a computer typically includes other peripheral output devices, such as speakers, printers, etc. 
     A display can be employed with a user interface coupled to the controller  195  to present data that is electronically received from the processing unit. For example, the display can be an LCD, plasma, CRT, etc. monitor that presents data electronically. Alternatively or in addition, the display can present received data in a hard copy format such as a printer, facsimile, plotter etc. The display can present data in any color and can receive data from a user interface via any wireless or hard wire protocol and/or standard. 
     The computer can operate in a networked environment using logical and/or physical connections to one or more remote computers, such as a remote computer(s). The remote computer(s) can be a workstation, a server computer, a router, a personal computer, microprocessor based entertainment appliance, a peer device or other common network node, and typically includes many or all of the elements described relative to the computer. The logical connections depicted include a local area network (LAN) and a wide area network (WAN). Such networking environments are commonplace in offices, enterprise-wide computer networks, intranets and the Internet. 
     When used in a LAN networking environment, the computer is connected to the local network through a network interface or adapter. When used in a WAN networking environment, the computer typically includes a modem, or is connected to a communications server on the LAN, or has other means for establishing communications over the WAN, such as the Internet. In a networked environment, program modules depicted relative to the computer, or portions thereof, may be stored in the remote memory storage device. It will be appreciated that network connections described herein are exemplary and other means of establishing a communications link between the computers may be used. 
     While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.