Patent Publication Number: US-2016230283-A1

Title: Fused Material Deposition Microwave System And Method

Description:
BACKGROUND 
     Additive manufacturing processes are used to produce three-dimensional objects. Layers of material are deposited and bonded together (optionally onto an object or a substrate) according to a prescribed pattern or design to create a 3-dimensional (3D) object. A 3D printer implements this printing process by depositing a layer of material (e.g., liquid, powder, extrusion (e.g., wire) or sheet) onto a pre-existing object or substrate and subsequently fusing, by the focused application of energy, some or all of the material to the pre-existing object or substrate according to the prescribed pattern. The process repeats to deposit and fuse multiple layers (each layer representing a cross section through the object) to form the 3D object. 
     Existing 3D printing processes include selective laser melting (SLM), direct metal laser sintering (DMLS), selective laser sintering (SLS), fused deposition modeling (FDM), stereo-lithography (SLA), laminated object manufacturing (LOM), electron beam melting (EBM), stereo-lithography (STL), digital light processing (DLP), and direct metal deposition (DMD). These additive manufacturing methods, however, have several drawbacks and limitations. For example, there are trade-offs between equipment and material costs, object resolution, speed, and properties of the finished object. Typically, compromises are required in order to achieve specific project objectives. These compromises are especially limiting in the case of additive manufacturing of metals and ceramics as well as large parts made of any material. For example, to address the costs associated with 3D printing of metal objects, a non-metallic object may first be created using 3D printing and then used to produce a mold for casting metal copies. Alternatively, additive manufacturing of metals may require a multi-step process in which several long and costly steps are required, limiting the benefits of additive manufacturing. 
     Laser-based processes for additive manufacturing of metals are described for example in U.S. Pat. No. 6,122,564 and U.S. Pat. No. 7,765,022. In these processes, a laser beam is focused onto an object, creating a melt pool into which additional powdered metal is injected. However, laser-based 3D printing processes for metallic and ceramic parts are often slow and limited in the size of objects they can print. Although resolution of such laser devices is high, the speed of generating the object is often slow because the laser beam is narrowly focused and has a small diameter requiring rapid movement (scanning) across each deposited layer (resulting in non-uniform heat distribution, poor fusing, and inconsistent mechanical properties between different parts). Moreover, penetration of the laser beam into certain materials is limited, resulting in the thickness of each added layer being small. Further, small diameter and small penetration thickness of a laser beam often can cause significant residual stress in the material leading to undesirable properties of the work piece. 
     Selective laser sintering methods, where a laser beam fuses layers of metal inside of powder bed, such as described in U.S. Pat. No. 4,863,538, are limited in the size of parts that can be produced because the parts are fabricated inside a large volume of metallic powder deposited layer by layer in the printing process, and hence the manufacturing process requires a very large amount of high quality uniform powder material. For large scale objects, the amount of power required for manufacturing becomes impractical. 
     Other methods of applying heat during the sintering portions of additive manufacturing processes entail a number of drawbacks and limitations. For example, sintering beams derived from frequencies around 2.45 GHz (i.e., wavelengths approximately equal to 12.22 cm) may be used; but the energy distribution of such beams can be difficult to control, with the beam being excessively diffused and unfocussed. As a result, heat is unintentionally applied outside of intended target areas, and precise control over depths of energy penetration become impossible. 
     SUMMARY OF THE INVENTION 
     A fused material deposition microwave system includes a high power microwave source, at least one deposition nozzle having adjustable outlet diameter for depositing one or more materials, a waveguide for guiding microwave energy to the deposition nozzle to melt the materials, and a material source to supply one or more materials to the deposition nozzle. The system further includes a controller for controlling the deposition nozzle, microwave energy flow, and material source, according to a computer-aided manufacturing (CAM) set of instructions to deposit and fuse molten material on a workpiece. 
     A fused material deposition microwave method includes delivering one or more materials to a deposition nozzle, guiding microwave energy from a high power microwave source to the deposition nozzle to melt the one or more materials, and controlling the material delivery, microwave energy, and position of the deposition nozzle according to a computer-aided manufacturing (CAM) set of instructions, thereby depositing and fusing molten material into a workpiece. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a fused material deposition microwave system, in an embodiment. 
         FIG. 2  shows a cross-sectional view of a fused material deposition microwave system with a flexible waveguide, in an embodiment. 
         FIG. 3  shows a cross-sectional view of a fused material deposition microwave system with a reflector, in an embodiment. 
         FIG. 4  shows a cross-sectional view of a fused material deposition microwave system with a waveguide including one or more reflectors, in an embodiment. 
         FIG. 5  shows a cross-sectional view of a portion of a fused material deposition microwave system highlighting a deposition nozzle, in an embodiment. 
         FIG. 6  shows a cross-sectional view of a deposition nozzle with adjustable waveguide position, in an embodiment. 
         FIG. 7  shows a cross-sectional view of a deposition nozzle with a separate waveguide and material conduit, in an embodiment. 
         FIG. 8  shows a portion of a fused material deposition microwave system, highlighting a waveguide enclosed in a conduit with four channels for deposition of different materials, in an embodiment. 
         FIG. 9  shows a cross-sectional view of a fused material deposition microwave system with a robotic arm, in an embodiment. 
         FIG. 10  shows a cross-sectional view of a mobile fused material deposition microwave system, in an embodiment. 
         FIG. 11  is a block diagram of a controller for a fused material deposition microwave system, in an embodiment. 
         FIG. 12  is a flowchart illustrating one exemplary method for microwave control during fused material deposition, in an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       FIG. 1  shows one fused material deposition microwave system  100 . System  100  includes a deposition nozzle  110  for depositing one or more materials, a microwave energy source  120  for providing microwave energy, and a material source  130  for supplying one or more materials. Examples of microwave energy source  120  include a gyrotron, klystron, magnetron, or other source of high-power microwave energy. Microwave energy source  120  is for example an integrated high-power microwave source that includes a compact power supply. Alternatively, microwave energy source  120  is modular, has an external power supply, and is coupled to a larger manufacturing apparatus. The modular embodiment is beneficial when system  100  is for example integrated into a CNC mill or a laser-based 3D printer. In an embodiment, the output power of microwave energy source  120  is adjusted by tuning current and voltage of an internal electron gun that directly affects electron current flowing inside a microwave cavity (e.g., inside a gyrotron). The change in electron current directly affects the amount of microwave energy created in the gyrotron and released. 
     Returning to  FIG. 1 , a conduit  140  guides material from material source  130  to deposition nozzle  110 . Material source  130  includes for example a source of pressurized gas or fluid configured to carry material from the material source  130  via a conduit  140  to the deposition nozzle  110 . Conduit  140  is flexible and moveable in three dimensions and includes a flexible waveguide that guides a beam of microwave energy from microwave energy source  120  to deposition nozzle  110 . Inside deposition nozzle  110 , material and microwave energy interact causing the material to melt immediately before or immediately after leaving the nozzle. Deposition nozzle  110  deposits molten material, which fuses to form a desired workpiece  160 . System  100  includes a deposition chamber  150 , to provide a controlled atmosphere for example. In an embodiment, deposition chamber  150  controls temperature, pressure, and gas composition. Gas composition includes for example a non-oxidative gas such as hydrogen or argon used to prevent oxidation of workpiece  160 . In an embodiment, air is removed from nearby the workpiece by displacing it with an inert gas, thereby creating a substantially oxygen-free atmosphere in chamber  150 . Workpiece  160  is formed on a moveable base, such as moveable base  170 . System  100  may include a cooler  190  used to cool moveable base  170 , thereby increasing the rate at which molten material solidifies. Cooler  190  may include one or more of the following components: a solid state heat pump, refrigerator, air heat exchanger with a fan, or a coolant loop with a pump that drives flow of a cooling liquid. A cooler  190  may be positioned at or inside a moveable base  170  or it may be positioned elsewhere within the deposition chamber  150 . Cooling takes place while material is deposited, providing an advantage in efficiency over existing additive manufacturing systems and methods that heat and cool material in cycles. 
     Again returning to  FIG. 1 , deposition nozzle  110  moves to a desired location along a first rail  112  and a second rail  114  to accommodate motion of nozzle  110 . In an embodiment, actuators rotate the nozzle around one or more of the rails to allow rotational degrees of freedom. Thus, system  100  deposits molten material in the desired location by coordinating the position of moveable base  170  and deposition nozzle  110 . Motion of base  170  along with motion of deposition nozzle  110  provides higher flexibility of a fabrication process and enables fabrication of more complex parts. Deposited molten material solidifies into the desired shape of workpiece  160 , which is optionally aided by atmospheric control of deposition chamber  150  and cooling of moveable base  170  by cooler  190 . Cooling is for example further provided to workpiece  160  by distributing a gas or liquid through conduit  140  and out deposition nozzle  110 . In an embodiment, cooling of deposition nozzle  110  is accomplished by immersion in a liquid. Deposition chamber  150  is for example partially filled with liquid configured to conduct away heat produced during material deposition. A controller  180  is provided to control all controllable features of system  100 , including deposition nozzle  110 , microwave energy source  120 , material source  130 , deposition chamber  150 , moveable base  170 , and cooler  190  according to a computer-aided manufacturing (CAM) set of instructions  185 . 
     Controller  180  is shown in exemplary detail in  FIG. 2  and  FIG. 11 . One or more instruments are configured to determine parameters of deposition chamber  150  and provide chamber parameter information to controller  180  in real-time. Chamber parameters define: (a) chamber conditions, such as temperature, pressure, atmosphere, and microwave power distribution in chamber  150 , and (b) parameters related to workpiece  160 . Measuring chamber parameters enables real-time feedback to controller  180  for active and adaptive control of material deposition (e.g., deposition rate) and microwave beam properties (e.g., beam size, power density, frequency). Methods for determining chamber conditions include several known instruments. To monitor temperature, uniformity, heat distribution and dissipation and other parameters of workpiece  160 , an infrared camera is for example provided with a radio frequency (RF) filter to protect the camera lens from small amounts of microwave energy which could escape the nozzle. An RF diode or a harmonic mixer is configured to provide real-time frequency measurements for feedback control of microwave source  120 . In an embodiment, one or more fluid loops are configured such that changes in temperature of the fluid are used as an indication of microwave power level. In an embodiment, more precise bolometric measurement tools are used to measure precise power output of the high power microwave source  120 . Instrumentation provides feedback on the application of microwave energy to workpiece  160 , including for example an optical pyrometer or another sensor disposed so as to observe temperatures at one or more locations on workpiece  160 . Knowledge and control of a wide range of environmental and process parameters are an integral part of fabricating complex objects. Controller  180  is configured to control parameters based on their real-time measurements, thus leading to an adaptive rather than fully predetermined manufacturing process. In an embodiment, controller  180  conducts simulations and analysis based on measured chamber parameters and uses the results to adapt CAM set of instructions  185  during the manufacturing process. 
       FIG. 2  shows a cross-sectional view of a fused material deposition microwave system  200 , which is an example of system  100  of  FIG. 1 . A dashed line  101  is drawn on the side and top of system  100  of  FIG. 1  to illustrate the location of cross-section used for  FIG. 2 . System  200  includes four material sources  230 ( 1 ),  230 ( 2 ),  230 ( 3 ), and  230 ( 4 ) for supplying four materials  235 ( 1 ),  235 ( 2 ),  235 ( 3 ), and  235 ( 4 ). The amount of material  235 ( 1 ) flowing to deposition nozzle  110  is for example controlled by an electro-mechanical shutter  236 ( 1 ). Only material  235 ( 1 ) and electro-mechanical shutter  236 ( 1 ) are noted in  FIG. 2  for clarity. Examples of material  235  include metals, ceramics, pre-ceramic polymers, and plastics. 
     It should be appreciated that mechanisms controlling flow of materials from material sources  230  can be different from electro-mechanical shutter  236 ( 1 ) and are determined by properties of the material. For example, when material is in the form of suspension, a valve may be used to control the flow. Other mechanisms known in the art may be used to supply material without limiting the scope of the invention. 
     Metals are naturally reflective making them difficult to heat with microwave energy, but metallic powders may be configured to be highly absorptive. Absorptivity and thermal characteristics of metallic and ceramic powders are configured for example by adjusting size and form of particles, adding small quantities of various secondary materials, creating mixtures, and by a number of other means known in the art and actively researched today. To increase microwave interaction and to enable easier delivery of materials  235  from hoppers  230  to nozzle  110  via conduit  140 , materials  235  are in the form of a powder, nano-particle, gel, suspension or other form. In an embodiment, powdered materials  235  are carried to nozzle  110  via an added medium such as a flow of gas or fluid that picks up materials  235  leaving hoppers  230  and carrying them to nozzle  110 . A pump (not shown) may be used to establish positive pressure between hoppers  230  and nozzle  110  to assist material  235  deposition. A conduit  240  guides materials  235  as illustrated by an arrow  238 . Conduit  240  is configured for example with channels to independently guide a plurality of materials to deposition nozzle  110  (see  FIG. 8 ). 
     Materials  235  are added layer by layer, with a plurality of layers being added. In an embodiment, layers of differing materials are added such that they bond to one another (e.g., metal disposed adjacent to ceramic or a metal deposited on a layer of metal) providing three-dimensional objects made of metals, ceramics and other materials in commercially significant quantities with consistent high quality. Accordingly, production efficiency and quality are improved, while costs and other requirements such as manufacturing time are reduced relative to conventional additive manufacturing systems and methods involving metallic and ceramic materials. 
     Returning to  FIG. 2 , conduit  240  includes a waveguide  245  that guides a beam of microwave energy  225  from microwave energy source  120  to deposition nozzle  110 . In an embodiment, microwave beam  225  is a Gaussian beam. In an embodiment, microwave beam  225  is a high-power millimeter-wave beam. The use of millimeter frequencies, such as for example 20-180 GHz, allows for precise and adjustable control of the beam and its energy distribution. Millimeter waves of approximately 20-180 GHz can be controlled and propagated from microwave source  120  to nozzle  110  via waveguide  245  of mm- and cm-size dimensions thus conforming to dimensions adequate for additive manufacturing applications as distinguished from low frequency radiation such as 2.45 GHz. Millimeter waves generated with high power microwave sources such as gyrotrons are typically generated with high efficiencies (40-60%) at high power levels (above 20 kW) and are significantly more powerful and more efficient than lasers used in additive manufacturing applications. Furthermore, compared to laser beams, microwave beam  225  is more spread-out and penetrates deeper into material  235 , providing more uniform energy distribution. Advantages include faster deposition, decreased cost, and increased speed of production for large structures. 
     In some cases, it is beneficial to control the frequency of microwave beam  225 . The frequency of microwave beam  225  is directly related to the strength of magnetic field, which causes gyration of electrons in the electron beam current flowing inside the gyrotron cavity. Although in many cases vacuum tubes, like gyrotrons, are designed to operate at a specific frequency determined by both the magnetic field and tube design, it is possible to vary the frequency in a number of ways, by for example using a step tunable gyrotron. By decreasing the field with a fixed multiple it is possible to operate the gyrotron at a different frequency while outputting a different mode. Also, by small changes in the magnetic field, it is possible to change the output frequency by a small amount (e.g., from 90 GHz to 90.5 GHz), which may be beneficial in some special use cases. The frequency is also affected by the geometry of the gyrotron&#39;s cavity, such that microwaves are emitted most efficiently at certain multiples of the magnetic field. The control over frequency is beneficial in manufacturing various materials, where said materials are optimized and configured to preferentially absorb microwaves of a specific frequency. 
     Again returning to  FIG. 2 , an arrow  228  illustrates the direction of travel of microwave beam  225 . In an embodiment, waveguide  245  is a flexible corrugated tube adapted to guide microwave beam  225 . In some embodiments waveguide  245  comprises walls configured to absorb a portion of microwave energy, thereby pre-heating material  235  flowing through conduit  240 . Side-to-side movement of deposition nozzle  110  along first rail  112  is illustrated by arrows  215 . Up/down movement of deposition nozzle  110  and first rail  112  along second rail  114  is illustrated by arrows  217 . In an embodiment, front/back movement of deposition nozzle  110  and first rail  112  occurs along a third rail (not shown), thus enabling deposition nozzle  110  to move in three dimensions. In an embodiment, movement of deposition nozzle  110  includes manipulating a position or orientation with one or more servo motors responsive to commands from controller  180 . In an alternate embodiment, controller  180  receives signal(s) that indicate where materials  235  are deposited, thereby instructing deposition in a desirable manner (e.g., to create a desired object shape). System  200  may include more than one deposition nozzle  110 , thereby enabling simultaneous deposition of more than one material  235  in separate locations of workpiece  160 . 
     System  200  allows fabrication of very high quality parts made of various steels, refractory metals, and ceramics. The ability to manipulate the position and orientation of deposition nozzle  110 , coupled with moveable base  170 , enables several advantageous uses. For example, to repair a defect such as a crack within workpiece  160 , fused material deposition system  200  applies molten material directly to the crack and over the crack thereby fixing the structural damage. 
     In an embodiment, system  200  applies microwave energy to internal portions of workpiece  160  without at the same time adding material  235 . This allows pre-heating workpiece  160  before starting deposition of a new material layer, which is beneficial in certain applications. 
     In another embodiment, system  200  is configured to adjust deposition nozzle  110  and flow of the material  235  to allow a controlled portion of energy from microwave beam  225  to escape from nozzle  110 . This energy would heat an area adjacent to the location of material deposition bringing the temperature of workpiece  160  closer to the temperature of the newly deposited layer of material. Pre-heating all or part of workpiece  160  with microwave beam  225  may be beneficial for reducing thermal stress and alleviating thermal relaxation during the cooling process. 
     In some cases it is beneficial to maintain microwave beam  225  on workpiece  160  after a layer of material is deposited and flow of material  235  has ceased. This allows a more gradual and uniform cooling of workpiece  160 . To achieve a desirable cooling rate, deposition nozzle  110  is for example configured to output microwave beam  225  with a predetermined shape and intensity for providing uniform distributed microwave heating to workpiece  160  during the cooling process. Shape of beam  225 , amount of power from microwave energy source  120 , and rate and duration of material  235  deposition are controlled by controller  180  through CAM set of instructions  185 , based on chamber parameters and properties of workpiece  160 . 
       FIG. 3  shows a cross-sectional view of a fused material deposition microwave system  300 . System  300  is a different implementation of system  100  of  FIG. 1 . Location of the cross-section through system  300  is similar to dashed line  101  of  FIG. 1 . System  300  includes conduit  340  configured to guide material  235  to deposition nozzle  110 , and a reflector  342  configured to reflect microwave beam  225  to deposition nozzle  110 . Although only one reflector  342  is shown in  FIG. 3 , system  300  may include any number of reflectors for focusing and directing microwave beam  225  to deposition nozzle  110 . Reflectors are well suited for creating large objects, while flexible waveguides, such as in  FIG. 2 , allow a higher degree of control. 
       FIG. 4  shows a cross-sectional view of a fused material deposition microwave system  400 . System  400  is a different implementation of system  100  of  FIG. 1 . Location of the cross-section through system  400  is similar to dashed line  101  of  FIG. 1 . System  400  includes conduit  440  configured to guide material  235  to deposition nozzle  110 . System  400  includes a waveguide  445 , which has at least one reflector  342  configured to reflect microwave beam  225  to deposition nozzle  110 . In this embodiment, waveguide  445  is configured primarily to prevent microwaves escaping into the chamber rather than for guiding beam  225 , while most of the guiding function is performed by reflector  342 . Waveguide  445  optionally houses microwave diagnostics such as bolometers and frequency measuring sensors to provide real-time feedback to controller  180  for controlling output of microwave source  120 . In an embodiment, waveguide  445  includes zero, one, or more, each of mirrors, horns, phase manipulators, launchers, and beam isolators to further manipulate microwave beam  225  without departing from the scope hereof. In an embodiment, beam isolators are located at microwave source  120  output, in waveguide  445 , or in deposition nozzle  110  to control power of microwave beam  225 . 
       FIG. 5  shows a cross-sectional view of a portion of a fused material deposition microwave system  500 . System  500  includes deposition nozzle  510 , which is an embodiment of deposition nozzle  110  of  FIG. 1 .  FIG. 5  further illustrates a nozzle outlet  518  of deposition nozzle  510 . System  500  is configured to deliver materials  235 ( 1 ),  235 ( 2 ) through channels of conduit  240  in direction  238  to nozzle outlet  518 . System  500  uses controller  180  to control delivery rates of one or more materials according to CAM set of instructions  185 . Thus, materials  235 ( 1 ),  235 ( 2 ) may be delivered from material sources  230 ( 1 ),  230 ( 2 ) simultaneously or sequentially and at similar or differing rates, thereby enabling formation of complex workpieces. 
     System  500  includes waveguide  245  to guide microwave energy beam  225  in direction  228  to nozzle outlet  518 . Inside nozzle outlet  518 , microwave energy beam  225  interacts with one or more materials  235 . The amount of energy needed to melt material  235  is computed by controller  180  based on the material used (defined in the CAM set of instructions  185 ). The amount of energy is controlled by adjusting the output of microwave energy source  120  or by introducing attenuation into the path of microwave beam  225 . Attenuation can be accomplished by changing the reflecting properties of waveguide  245  or one or more reflectors, such as reflector  342  of  FIGS. 3 and 4 . Attenuation is also accomplished for example by means of a controllable isolator introduced into waveguide  245  or at the output of microwave source  120 . 
     In some embodiments, a fraction of microwave energy is reflected back to microwave source  120  from mirrors, nozzles, or other parts of the system. In such cases, it is beneficial to introduce an isolator at the output of microwave source  120 . 
     In an embodiment, waveguide  245  is highly reflective, leading to low loss of microwave energy. In an alternative embodiment, waveguide  245  absorbs a fraction of microwave energy, thereby pre-heating material  235  as it flows through conduit  240 . Pre-heating material  235  causes faster melting in nozzle outlet  518 , thereby enabling faster deposition rates. 
     In an embodiment, nozzle outlet  518  has a mechanically adjustable diameter that is controlled by controller  180  according to CAM set of instructions  185 . Increasing the diameter of nozzle outlet  518  enables faster deposition rates. Conversely, decreasing the diameter of nozzle outlet  518  reduces droplet size of molten material thereby improving resolution for depositing material. The diameter of nozzle outlet  518  is matched to a material melting rate, which depends on parameters of microwave beam  225 , delivery rates of one or more materials  235  from material source  230 , properties (e.g., conductivity and permittivity) of one or more materials  235 , and the fraction of microwave energy absorbed by waveguide  245 . 
       FIG. 6  shows a cross-sectional view of a deposition nozzle  600 , which is an embodiment of deposition nozzle  110  of  FIG. 1 . Deposition nozzle  600  includes an adjustable waveguide  645 , which is configured to move positions relative to conduit  240 . Arrows  646  and  647  show up and down motion of waveguide  645 , respectively. Adjusting the position of waveguide  645  relative to conduit  240  increases or decreases the volume of material  235 ( 1 ),  235 ( 2 ) to be melted through interaction with microwave energy beam  225  in nozzle outlet  518 . Position of waveguide  645  relative to conduit  240  is controlled by controller  180  according to CAM set of instructions  185 . An adjustable position of waveguide  645  relative to conduit  240  provides an additional controllable feature for controlling melting of different materials. 
       FIG. 7  shows a cross-sectional view of a deposition nozzle  700 , which incorporates the same principles as the deposition nozzle  110  of  FIG. 1 , but allows a different arrangement of components within the fused material deposition system. Deposition nozzle  700  includes waveguide  245  disposed outside of conduit  240 . Microwave energy beam  225  heats material  235  outside a nozzle outlet  718  as material  235  is deposited. In an embodiment, material  235  is sprayed from nozzle outlet  718  near the end of waveguide  245 , thereby adding material  235  to workpiece  160 . In an embodiment, material source  230  includes a pump to supply increased pressure for spraying material  235 . Control of the pump is performed by controller  180  according to CAM set of instructions  185 . 
       FIG. 8  shows a portion of a fused material deposition microwave system  800 . System  800  includes a conduit  840 , which is an embodiment of conduit  140  of  FIG. 1 . Conduit  840  includes channels  841 ,  842 ,  843 , and  844 , shown in a cross-sectional view  845  that are configured to transport different materials to deposition nozzle  110 . Conduit  840  includes four channels but may include fewer or greater than four depending on the number of different materials desired. 
     In a preferred embodiment, the fused material deposition microwave system  800  includes a deposition nozzle  110  that is adjustable and controllable in position, orientation, and outlet diameter; in this way such a configurable deposition nozzle  110  is particularly suited for deposition of powdered materials heated beyond melting point. Control over nozzle  110  allows for fabrication of parts with varying materials while improving deposition speed and localization of powder deposition onto workpiece  160 . Waveguide  245  is accordingly matched to a specific form of high power millimeter-wave microwave energy  225 , which further allows for robust control over beam characteristics. 
       FIG. 9  shows a cross-sectional view of a fused material deposition microwave system  900 . System  900  is an alternative implementation of a system  100  of  FIG. 1 . Location of the cross-section through system  900  is similar to dashed line  101  of  FIG. 1 . System  900  includes a robotic arm  995  for moving position and orientation of deposition nozzle  110  in three dimensions, thereby positioning a nozzle outlet  918  with controller  180  according to CAM set of instructions  185 . In this embodiment, the positioning of deposition nozzle  110  is accomplished with robotic arm  995  for greater flexibility compared to using rails. 
       FIG. 10  shows a cross-sectional view of a mobile fused material deposition microwave system  1000 . System  1000  is an example of system  100  of  FIG. 1 . System  1000  is configured on a vehicle to provide a mobile fused material deposition microwave system. Mobile system  1000  is adapted to perform fused material deposition outside of a chamber with controlled atmosphere by equipping robotic arm  995  with a gas hose that is integrated with, or attached to, deposition nozzle  110 . Robotic arm  995  is for example configured to supply a flow of oxygen-free gas, such as hydrogen, nitrogen or argon, to prevent oxidation. Disposing non-oxidative gas while depositing molten material prevents oxidation and cools the molten material. Advantages of mobile system  1000  include the ability to fabricate complex components in remote locations and the ability to repair or modify existing infrastructure such as bridges. Thus, workpiece  1060  represents either a newly built workpiece or an existing object to be repaired or modified. 
       FIG. 11  shows controller  180  in further exemplary detail. Controller  180  is for example a computer that includes a memory  1102 , a processor  1104 , and an interface  1106  for receiving CAM set of instructions  185 . Memory  1102  stores software  1120  that includes machine readable instructions that when executed by processor  1104  provide control and functionality of system  100  as described herein. Software  1120  includes a beam control algorithm  1122  and a deposition control algorithm  1124 . 
     Beam control algorithm  1122  provides instructions to control microwave beam  225  properties (e.g., beam size, power density). Beam control algorithm  1122  operates to process chamber parameters  1110  and CAM set of instructions  185  to generate beam instructions  1142  that control operation of microwave energy source  120  for each step in generating workpiece  160 . Chamber parameters  1110  provide for example the size, shape, and contents of deposition chamber  150  to software  1120 . Chamber parameters  1110  also provide for example parameters within the chamber such as temperature, pressure, and atmosphere to software  1120 . In some embodiments, chamber parameters  1110  are real-time parameters that provide a variety of changing characteristics at every step of the deposition process, including for example thermal infrared images of workpiece  160  provided after, and in between, each step of the process. 
     Beam control algorithm  1122  may use a simulation model employing basic physics principles to compute necessary beam instructions  1142  after every step based on chamber parameters  1110 . The simulation model is for example custom written, but its principle of operation, which is based on thermo-mechanical, fluid dynamic and electromagnetic principles, may be similar to COMSOL, ANSYS, Autodesk Simulation 360, or any other physics based simulation tool. Note that the simulation runs within controller  180 , or optionally controller  180  uses an external computer, such as a remote or a cloud-based server, wherein controller  180  uses an Internet connection to exchange data with the remote computer. 
     CAM set of instructions  185  includes an object shape  1132 , which defines the shape of the workpiece  160  being generated, a sequence  1134  that defines steps for generating each layer of workpiece  160 , and instructions for control of microwave beam  225  during each step of the process. For example, CAM set of instructions  185  defines the three-dimensional shape of the object to be generated and the type of material for each layer added to workpiece  160 . A sequence  1134  that defines steps for generating each layer is for example an adjustable sequence that is modified based on the input of chamber parameters  1110  during each step of the deposition process by software  1120 . Beam instructions  1142  for control of microwave beam  225  are for example an adjustable set of instructions modified by software  1120  during each step of the deposition process based on chamber parameters  1110 . 
     Deposition control algorithm  1124  processes CAM set of instructions  185  and chamber parameters  1110  to generate deposition instructions  1144  that control deposition nozzle  110  to deposit material  235  on workpiece  160 , control flow of material  235  to the nozzle  110 , control timing and rate of deposition, control cooler  190 , and in some embodiments provide other control functions as needed. 
       FIG. 12  is a flowchart illustrating one exemplary fused material deposition microwave method  1200 . Method  1200  is for example implemented within software  1120  of controller  180 . 
     In step  1201 , method  1200  reads a first step from CAM set of instructions  185  and current chamber parameters  1110 . In one example of step  1201 , software  1120  reads information of a first step for creation of a workpiece  160  from sequence  1134  of CAM set of instructions  185 . 
     In step  1202 , method  1200  controls material source  230  to supply material  235  at a specified rate through conduit  240  to deposition nozzle  110 . In one example of step  1202 , software  1120  controls material source  230  to supply material  235  at a specified rate through conduit  240  to deposition nozzle  110  based upon the first step of CAM set of instructions  185 . 
     In step  1203 , method  1200  positions nozzle  110  to a desired location and orientation. In one example of step  1203 , software  1120  controls deposition nozzle  110  to a desired location and orientation based on the first step of CAM set of instructions  185 . 
     In step  1204 , method  1200  calculates microwave beam  225  parameters. In one example of step  1204 , software  1120  invokes beam control algorithm  1122  to calculate beam instructions  1142  based upon chamber parameters  1110 , object shape  1132 , and first step of sequence  1134 . In an embodiment, beam instructions  1142  include one or more of (i) power of the beam, (ii) time of the pulse, and (iii) frequency of the beam (if for example microwave energy source  120  is multi-frequency). 
     In step  1206 , method  1200  controls microwave energy source based upon microwave beam  225  parameters. In one example of step  1206 , software  1120  sends beam instructions  1142  from controller  180  to microwave energy source  120 . In an embodiment, software  1120  sends beam control instructions to mirrors and isolator(s) within the waveguide when such additional control is needed. 
     In step  1208 , method  1200  activates high power microwave energy source  120 . In one example of step  1208 , software  1120  sends beam parameters defined within beam instructions  1142  to microwave energy source  120 , wherein microwave energy source  120  generates microwave beam  225  based upon the beam parameters. 
     It must be appreciated that the time between steps  1201 ,  1202 ,  1203 ,  1204 ,  1206  and  1208  can be extremely small so as to be considered negligible for a mechanical system, where motion of various components such as nozzle actuators, pump actuators and other mechanical components operate much slower than deposition instructions  1144 . 
     In step  1210 , method  1200  reads a next step of the CAM set of instructions  185  and current chamber parameters  1110 . In one example of step  1210 , software  1120  reads a next step for manufacturing workpiece  160  from sequence  1134  of CAM set of instructions  185 . Based on CAM set of instructions  185  and chamber parameters  1110 , beam control algorithm  1122  and deposition control algorithm  1124  may be adjusted. 
     In step  1211 , method  1200  controls material source  230  to supply material  235  at a specified rate through conduit  240  to deposition nozzle  110 . In one example of step  1211 , software  1120  controls, material source  230  to supply material  235  at a specified rate through conduit  240  to deposition nozzle  110  based upon the current step of CAM instructions  185 . 
     In step  1212 , method  1200  positions nozzle  110  to a desired location and orientation. In one example of step  1212 , software  1120  controls deposition nozzle  110  to a desired location and orientation based on the current step of CAM set of instructions  185 . 
     In step  1213 , method  1200  calculates next microwave beam  225  parameters. In one example of step  1213 , software  1120  invokes beam control algorithm  1122  to calculate beam instructions  1142  based upon current chamber parameters  1110 , object shape  1132 , and the current step of sequence  1134 . 
     In step  1214 , method  1200  controls microwave energy source  120  based upon microwave beam  225  parameters. In one example of step  1214 , software  1120  sends beam instructions  1142  from controller  180  to microwave energy source  120 . In an embodiment, software  1120  sends beam instructions  1142  to mirrors and isolator(s) within the waveguide when such additional control is needed. 
     In step  1215 , method  1200  activates high power microwave energy source  120 . In one example of step  1215 , software  1120  sends beam parameters defined within beam instructions  1142  to microwave energy source  120 , wherein microwave energy source  120  generates microwave beam  225  based upon the beam parameters. 
     Step  1216  is a decision. If, in step  1216 , method  1200  determines that the end of the CAM set of instructions  185  has been reached, method  1200  continues with step  1218 ; otherwise, method  1200  repeats steps  1210  through  1216 . 
     In step  1218 , method  1200  deactivates the high power microwave energy source. In one example of step  1218 , software  1120  sends a control signal to deactivate microwave energy source  120 . Method  1200  then terminates. 
     This disclosure has been described above primarily with reference to its application in a 3D additive manufacturing system. It should be clear to one skilled in the art of material processing and additive manufacturing, however, that systems of other varied configurations and for other uses such as part repairs and material processing can be envisaged without being limited to those examples provided herein. 
     Changes may be made in the above methods and systems without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall therebetween.