Patent Publication Number: US-6705921-B1

Title: Method and apparatus for controlling cutting tool edge cut taper

Description:
FIELD OF THE INVENTION 
     The present invention relates to methods and apparatuses for orienting a cutting tool. More particularly, the present invention relates to methods and apparatuses for controlling, reducing or eliminating the tapered edge that results when a workpiece is cut with a cutting tool. 
     BACKGROUND OF THE INVENTION 
     Cutting tools for cutting workpieces are generally known, with examples including drills and the like. One particular genre of cutting tools is non-contact cutting tools. Typically these tools emit a high energy stream towards a workpiece to cut the workpiece. Examples of such non-contact cutting tools include laser tools, torches such as an acetylene torch, plasma cutting tools, and high pressure waterjets. 
     Taking waterjet systems as exemplary of non-contact cutting tools, a typical waterjet system includes a waterjet head that is supplied with liquid at an ultra high pressure (UHP), for example 10,000 to 60,000 pounds per square inch (psi). The UHP liquid is discharged in an axial direction from the head in a high velocity stream against the workpiece. The liquid stream is used to cut through materials such as wood, metal, paper and foam. An abrasive particulate material can be added to the stream, and the liquid/abrasive stream can be used to cut through composites, metals and other dense materials. The cutting stream typically is concentrated in a small area that may be for example about 0.05 inch diameter, and has a high flow rate of for example about one to three gallons per minute (gpm). With commonly available equipment, the waterjet head and the cutting stream are maintained perpendicular to the top surface of the workpiece and are moved by a computer numerically controlled (CNC) system in order to cut through the workpiece along a cut line. 
     Although non-contact cutting tools such as waterjet systems have many advantages, an unfortunate result of making a cut with such a tool can be the taper of the cut edge. In most instances it would be desirable for the finished edge to have no taper and to be in a plane perpendicular to the workpiece top surface. However, the non-contact cutting stream, such as the water stream, may produce an edge that is inclined or tapered. The cutting stream may remove more material at the top than at the bottom of the cut, and in this case the resulting cut edge has what can be termed a positive taper. Referring particularly to waterjet systems by way of example, the amount of the taper is dependent on many variables including the speed at which the waterjet head is moved along the workpiece surface. At very slow speeds a relatively taper-free or a negatively tapered edge can be formed. Slower cutting speeds, however, increase production times and are disadvantageous. 
     A prior art waterjet cutting system designated as a whole as  10  is shown in FIG.  1 . The system  10  is used to form a cut  12  in a workpiece  14 , and includes a waterjet head assembly  16 . The waterjet head  16  includes a valve body  18  operated to open or closed positions by an actuator  20  controlled remotely by the presence or absence of pressurized air supplied to the actuator  20  through an air control conduit  22 . Ultra high pressure (UHP) liquid is supplied to the waterjet head  16  from a suitable UHP pump system  21  at pressures of between about 10,000 and 60,000 PSIG through a UHP liquid supply conduit  23  normally formed of stainless steel and having sufficient flexibility to permit movement of the waterjet head  16  around the surface of the workpiece  14 . 
     A valve nut  24  attaches a tube  26  to the bottom of the valve body  18 . When the valve in the valve body  18  is opened by the application of pressurized air within the actuator  20 , UHP liquid flows downward through the valve body  18  and the tube  26  to an outlet nozzle assembly  28  including a mixing chamber housing  30  and a nozzle  32 . The nozzle  32  is aligned with the longitudinal axis of the waterjet head  16 , and includes an axial discharge passage through which a concentrated UHP liquid stream is discharged at high pressure and high velocity. 
     For many applications, fine particles of an abrasive material such as garnet are added to the liquid stream. The mixing chamber member  30  receives particulate abrasive through a flexible rubber or neoprene abrasive supply line  34 . When UHP liquid flows through the mixing chamber member  30 , abrasive material is entranced in the liquid stream and a liquid/abrasive stream having increased cutting capability is discharged from the nozzle  32 . 
     The waterjet head  16  is supported, typically with its axis vertical and perpendicular to the top surface  38  of the workpiece  14 , by a clamp  36  or similar fixture. The clamp  36  is carried by a support arm  40  extending from a clamp plate  42  attached to a front plate  44  of a support member or lift  46 . The lift  46  is moved in three orthogonal directions by a three axis X-Y-Z drive  48 . Typically the drive  48  can move the waterjet head  16  in an X direction from side to side over the workpiece  14  and, separately or simultaneously, in a Y direction forward and rearward over the workpiece  14 . The drive  48  can also move the head  16  in a Z direction, vertically with respect to the workpiece. A computer numerical control (CNC) system  50  controls the drive  48  to perform a cutting operation upon the workpiece  14 . The head is moved in the Z direction to place the outlet of the nozzle  32  near the top workpiece surface  38 . Then the control system moves the head  16  in the X and/or Y directions to form the cut  12 . Typically the control system  50  is programmed to cut the workpiece in selected straight and/or curved lines and/or corners to fabricate finished parts having a desired shape. 
     Prior art waterjet systems of the type seen in FIG. 1 are commercially available from sources including EASE Cutting Systems, 411 Ebenezer Road, Florence, S.C. 29501-0504. A further description of the prior art system  10  can be found at the title pages and pages 2-4, 2-5, 2-7, 2-8, 2-12, 4-29, 4-30 and 2-24 through 6-26 of ESAB Cutting Systems manual No. F14-135 dated May, 1999, filed herewith and incorporated herein by reference. A further description of a prior art waterjet head can also be found in U.S. Pat. No. 6,126,524 incorporated herein by reference. 
     When the cut  12  is formed in the workpiece  14  by the vertically disposed head  16 , the sides of the cut  12  are defined by inclined, sloped walls  12 A and  12 B. These sloped walls form a tapered cut  12 . The slope of the sides  12 A and  12 B of the tapered cut  12  can be as large as a several degrees. This taper can be undesirable, and in most operations a sidewall of the finished part that is perpendicular to the top surface  38  would be preferred. In some operations, a taper different from that of sides  12 A and  12 B would be preferred, for example to provide a beveled edge. 
     It would be desirable to control the taper of the cut edge so that taper could be reduced or eliminated or, alternatively, so that a controlled beveled edge of a desired angle could be produced. It has been recognized that positive taper can be reduced by slowing the cutting speed of the waterjet head. This practice, however, adds to manufacturing time and cost. In addition, expensive five-axis tilt control assembly systems are available for providing tilt and rotation in addition to X-Y-and Z movement that may offer some degree of taper control. Known five axis systems, however, are costly, complex, and bulky. These and other factors are deterrents to their use. 
     A proposed solution for cut edge bevel control is shown in U.S. Pat. No. 5,199,342 to Hediger (“the &#39;342 patent”). The system disclosed in the &#39;342 patent generally discloses a waterjet nozzle movably held by an X-Y drive system at a first point, and with the nozzle end pivotably held. X-Y movement at the first point causes the nozzle to be oriented at an angle to a workpiece. The X-Y drive system moves the first connection point in a first frame, which is movably held on a second frame. While some degree of tilt is provided, the overall configuration of the system of the &#39;342 patent entails a degree of complexity and cost that is undesirable. 
     Unresolved needs therefore remain in the art. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to methods and apparatuses for controlling the taper of a workpiece edge cut by a cutting tool. A tilt control assembly of the invention includes a tilt control assembly body with first and second supports coupled to the body. Each of the first and second supports is connected to the head along an axis of the head. In a first exemplary tilt control assembly of the invention, the first support is eccentric and movably coupled to the tilt control assembly body. A drive is coupled to the first support and is operative to rotate the first head support and position the head at a selected angle to the workpiece. In a second exemplary tilt control assembly of the invention, both of the first and second supports are movable, and are coupled to a drive operative to rotate the first and second head supports and position the head at a selected angle to the workpiece. In a preferred embodiment of the apparatus of invention, both the first and second head supports are eccentric. 
     In still an additional aspect of the present invention, a method for positioning a cutting tool head is provided. An exemplary method comprises the steps of supporting a cutting tool head with first and second supports along an axis of the head, and moving both of the supports to position the head at a selected angle to the workpiece. Preferably, both the first and second supports are moved eccentrically. 
     Methods and apparatuses of the invention thereby provide advantages and solutions to problems of the prior art. For example, an apparatus of the invention that has two eccentric head supports provides compact and relatively inexpensive tilt control capabilities that can be used to control the taper of a cut edge over a wide range of taper or bevel angles. Additional advantages and aspects of the invention will be better understood through consideration of the detailed description of invention embodiments provided herein below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention together with the above and other objects and advantages may best be understood from the following detailed description of the preferred embodiments of the invention illustrated in the drawings, wherein: 
     FIG. 1 is a partly schematic, side elevational view of a prior art waterjet cutting system also showing in cross section a cut made by the system in a workpiece; 
     FIG. 2 is a partly schematic, side elevational view of a waterjet cutting system of the present invention showing partly in cross section a tilt control assembly of the invention, and also showing in cross section a cut in a workpiece made by performing the method of the present invention; 
     FIG. 3 is an enlarged cross section of a portion of the tilt control assembly and a portion of the nozzle shown in FIG. 2; 
     FIG. 4 is a cross section top view of the tilt control assembly of FIG. 2 viewed generally along the line  4 — 4  of FIG. 2; 
     FIG. 5 is a flowchart illustrating steps of a method for controlling the taper of a workpiece cut by a non-contact cutting tool; and 
     FIG. 6 is a schematic view illustrating an example of cutting a workpiece in accordance with the present invention. 
    
    
     DETAILED DESCRIPTION 
     Having reference now to the drawings, FIG. 2 shows a waterjet cutting system in accordance with the present invention, generally designated as  100 . An advantage of the invention is that it can incorporate many of the components of a standard, prior art system such as that seen in FIG. 1, and therefore is relatively low in cost. In FIG.  2  and the other figures of the drawings, the same reference characters are used for components of the system  100  that are in common with the system of FIG. 1, and the description of these common components is not repeated except where helpful to an understanding of the invention. 
     In the system  100 , a tilt control assembly shown generally at  102  (partly in cross section), is provided for selectively positioning the jet head  16  at an angle to the workpiece  160 . The tilt control assembly  102  includes first and second eccentric head supports  104  and  106  (shown in cross section in FIG. 2) that are disposed along an axis of the jet head  16 . More specifically, the eccentric supports  104  and  106  are connected to the tube  26  along its axis. Each of the eccentric supports  104  and  106  is connected by a drivebelt  108  and  110 , respectively, to a respective drive wheel  112  and  114 . The top view of the tilt control assembly  102  shown in FIG. 4 better illustrates the placement of the drive wheels  112  and  114 . The supports  104  and  106 , as well as the drive wheels  112  and  114  are all coupled to a tilt control assembly body  115  that is connected to the lift  46 . Through rotation of the eccentric supports  104  and  106 , the jet head  16  may be positioned at a desired degree of tilt. 
     In the preferred tilt control assembly  102 , the eccentric head supports  104  and  106  are in the form of eccentric gears optionally having formations such as teeth or the like on their perimeter (not illustrated) for cooperating with the drive belts  108  and  110 . The gears  104  and  106  are preferably constructed of a material selected for cost, durability, and the like, and may be stock items available from hardware supply vendors such as the McMaster Carr Corp., 600 County Line Road, Elmhurst, Ill. (“McMaster Carr”). As best illustrated by the cross section of FIG. 3, the preferred eccentric gears  104  and  106  have an inner bearing housing  116  and  118  fixedly held in their eccentric throughbores  120  and  122 , respectively. The bearing housings  116  and  118  may be fixedly held in the eccentric throughbores  120  and  122  by friction, adhesive, fasteners such as a screw, bolt, or pin, or the like. Each of the bearing housings  116  and  118  has a respective throughbore  124  and  126  with the shape of a spherical segment. A spherical bearing  128  and  130  is tiltably held in each of the throughbores  124  and  126 . The bearings  128  and  130  each have a respective tube receiving passage  131  and  133  for receiving the tube  26  of the jet head. 
     The bearings  128  and  130  preferably have a shape adapted to cooperate with the shape of the bearing housing throughbores  124  and  126 , such as the cooperating spherical convex/concave shapes illustrated in FIG.  3 . The cooperating shapes preferably allow for snap fitting of the bearings  128  and  130  into the bearing housings  116  and  118 , while allowing for tilt and rotational movement. The bearings  128  and  130  may be constructed of materials selected for strength, cost, low friction, and like factors. An exemplary material of construction is Delrin. The bearings  128  and  130  along with the bearing housings  116  and  118  may be available from stock supply at hardware vendors such as McMaster Carr. 
     A first bearing race  132  is defined between the eccentric gears  104  and  106  with a roller bearing assembly  134  movably held therein to facilitate rotation of the two gears  104  and  106  relative to one another. The roller bearing assembly  134  is preferably suitable to facilitate simultaneous rotation of the gears  104  and  106  in opposite directions. As will be appreciated by those knowledgeable in the art, suitable roller bearing configurations are known. An example preferred roller bearing  134  configuration comprises a plurality of roller bearings held in a cage or the like and sandwiched between upper and lower washers that contact the race  132 , and is available from McMaster Carr as a “Needle-Roller Thrust Bearing Assembly.” 
     The gears  104  and  106  are movably retained in a bracket  136 . Second and third bearing races  138  and  140  are defined between the bracket  136  and the eccentric gears  104  and  106 . A plurality of ball bearings  142  are rotatably held in the races  138  and  140  to facilitate rotation of the gears  104  and  106  relative to the bracket  136 . 
     Referring once again to FIG. 2 in addition to FIG. 3, the first and second eccentric gears  104  and  106  may be rotated through action of the drive wheels  112  and  114  and drive belts  108  and  110  to orient the head  16  at a desired angle to the workpiece  160 . The limits of orientation depend on factors that include the degree of eccentricity (i.e., the distance from the center of the gear that the eccentric throughbore  120  and  122  is centered), and the vertical spacing of the supports  104  and  106  from one another. As shown by FIG. 2, a tilt controller  144  in combination with a tilt motor  146  are provided to selectively rotate each of the drive wheels  112  and  114 . The drive wheels  112  and  114  may be rotatably supported on a bracket  147 , and may be provided with formations such as gear teeth about their perimeter for cooperating with the drive belts  108  and  110 . The tilt motor  146  may be a DC stepper motor connected to the tilt assembly body  115 . The drive wheels  112  and  114  can be rotated independently of one another. Two motors  146  are provided, with one motor  146  linked to each of the drive wheels  112  and  114 . Although only a single motor  146  has been illustrated in FIG. 2, it will be appreciated that a second motor  146  is generally behind the first as depicted in that FIG. 
     In order to properly orient the eccentric supports  104  and  106 , the tilt controller  144  may be provided with pre-determined positioning data, an algorithm, or other like data or logic for specifying what rotational position each of the supports  104  and  106  must be in to achieve a desired head  16  angle. The tilt controller  144  may be linked to the X-Y-Z drive  48 , so that tilt of the head  16  can be accomplished in cooperation with X-Y-Z movement. Additionally, a sensor  148  (FIG. 2) may further be provided for sensing X-Y-Z movement of the head  16  from the X-Y-Z drive  48  or from other input. The sensor  146  may specify a desired tilt angle based on X-Y-Z movement if, for instance, a constant bevel edge is desired on a workpiece  160  being cut as the head  16  is moved along a desired X-Y cutting path on the workpiece  160 . 
     It will be appreciated that the tilt controller  144  and/or the sensor  148  may be functionally integral with one another, and may further be functionally integral with the tilt motors  146 . As used herein, the tilt motors  146 , the tilt controller  144 , and the sensor  148  may be generally referred to individually or collectively for convenience as a “tilt drive”. Accordingly, it will be understood that a “tilt drive” as used herein broadly refers to one or more functional components that generally include one or more tilt motors such as the motor  146  for driving rotation of the eccentric supports  104  and  106  in addition to a tilt controller such as controller  144  for determining or specifying the degree of rotation of the supports  104  and  106  required to achieve a desired angle of head  116  tilt. A tilt drive may further include a sensor  148  or other sensing or position calculating capability internal to the controller  144  and/or the X-Y-Z drive  48 . 
     Those knowledgeable in the art will appreciate that other drive systems for rotating the eccentric supports  104  and  106  may be provided as alternatives to the drive wheels  112  and  114  and drive belts  108  and  110 . For example, a direct worm or gear drive system may be used. In such an embodiment, the eccentric supports  104  and  106  are driven directly by the worm or gear drive. Selection of a particular drive system will depend on factors such as cost, size, degree of precision of movement required, and the like. It is believed that a worm gear drive, for example, may offer some benefits in terms of compactness over the drive wheel and drive belt configuration illustrated in FIG.  2  and FIG.  4 . 
     Those knowledgeable in the art will appreciate that a wide variety of applications for tilt control assemblies of the invention exist, and that different ranges of angles of orientation will be desirable for different applications. An exemplary orientation range is between about 0° (i.e., vertical) and about 45°. In one configuration suitable to achieve a substantially vertical orientation, the two supports  104  and  106  are substantially axially aligned with one another, and are equally eccentric (i.e., throughbore located equal distance off center on each support). It is believed that for a typical non-contact cutting tool, an axial separation distance shown as distance A in FIG. 3 (which is intended to represent the distance between the axial centerlines of the first and second eccentric supports  104  and  106 ) of about 1 in. or less, and a degree of eccentricity of less than about 0.1 in. (i.e., the eccentric throughbores  120  and  122  centered about 0.1 in. or less from the center point of the respective gears  104  and  106 ) will be useful. 
     In an exemplary waterjet cutting tool of the invention, the tilt control assembly  102  is suitable to orient the head  16  at an angle of between about 0° and about 9°. In order to achieve this range, two substantially identical eccentric supports  104  and  106  are provided with eccentric throughbores  120  and  122  centered about 0.055 in. off center of the gears  104  and  106  (i.e., eccentric by about 0.055 in.), and with a distance of about 0.75 in. separating the axial centerlines of the two eccentric gears  104  and  106  (i.e., the distance A of FIG. 3 equal to about 0.75 in.). With these dimensions, when the throughbores  120  and  122  are oriented in line with one another, the head  16  is substantially vertical. When the throughbores  120  and  122  are oriented at about 180° from one another with these preferred dimensions, a maximum tilt of about 9° is achieved. 
     As the jet head  16  is tilted at various angles, the tube  26  may move with respect to one or both of the eccentric gears  104  and  106 . For example, when the eccentric gears  104  and  106  are rotated from an aligned position to their maximum tilt, the tube  26  will move in an axial direction through one or both of the bearings  128  and  130 . Accordingly, the present invention contemplates allowing for some degree of movement of the tube  26  through the bearings  128  and  130 . The need for tube  26  movement, however, should be balanced against a need for restraining the tube  26  from excessive slippage when a high-pressure jet stream is being ejected from the head  16 . As illustrated by FIG. 3, a shoulder  150  is provided in the preferred waterjet  100  to engage the bearing  128 . To allow for a limited degree of axial movement of the tube  26  through the bearings  128  and  130 , a movable sleeve  152  is provided for engaging the bearing  130 . The sleeve  152  is urged by a biasing spring  154  into engagement with the bearing  130 , and has a maximum degree of slippage limited by an annular stop  156  that supports the spring  154 . Alternatives to the biasing spring  154  are available for urging the sleeve  152  into engagement with the bearing  118 . For example, it is believed that a compressible foam element may provide advantages over a spring in terms of cost. 
     In addition to apparatuses, the present invention is also directed to methods for controlling the bevel of an edge of a workpiece cut by a non-contact cutting tool. In considering methods of the invention, it will be appreciated that the methods may comprise steps of using a tilt control apparatus or a non-contact cutting tool of the invention. Accordingly, it will be appreciated that the FIGS. 2-4 and the description made herein with regards to those figures may be useful for description of methods of the invention in addition to an apparatus. 
     FIG. 5 is a flowchart illustrating the steps of a method of the invention. The head of a non-contact cutting tool is supported with a first eccentric support (block  200 ). An additional step of supporting the head with a second eccentric support along an axial line of the head is performed (block  202 ). To orient the head at a desired angle, the first and second eccentric supports are then rotated (block  204 ). 
     With the general method description of FIG. 5 now having been made, a more detailed exemplary method of the invention directed to controlling the bevel of an edge cut may be illustrated through consideration of the workpiece  160  of FIG.  2 . In accordance with this method of the invention, steps are provided for using the tilt control assembly  102  to control the taper of the finished edge resulting from the cut  158  in the workpiece  160 . The cut  158  is defined on one side by an edge  158 A and on the other side by an opposed edge  158 B. In FIG. 2, the portion of the workpiece  160  including the edge  158 B is a finished part  164  severed from the workpiece  160  by the waterjet cutting operation. The tilt control assembly  102  maintains the waterjet head  16  tilted at a predetermined angle relative to a vertical line so that, in the arrangement of FIG. 2, the edge  158 B of the finished part is generally perpendicular to the top surface  162 . 
     A method of controlling the taper may be better illustrated through consideration of the schematic of FIG.  6 . The workpiece  160  is cut along a line  166  seen on the top surface  162 . The line  166  includes a first segment  166 A extending in what can be termed a plus X direction, a second segment  166 B extending in a Y direction and a segment  166 C extending in a negative X direction. The X-Y-Z drive  48  moves the lift  46 , the tilt control assembly  102 , and the waterjet head  16  over the surface  162  to form the cut  158  through the workpiece along the line  166 . The cut  158  along the line  166  severs the finished part  164  from the workpiece  160 , leaving a scrap section  168  of the workpiece  160 . 
     The tilt angle of the waterjet head  16  relative to a vertical line is selected so that the generally perpendicular cut edge  158 B is achieved on the finished part side of the cut  158 . The axis of the tilted waterjet head  16  and the vertical line are in a common tilt plane. The tilt control assembly  102  tilts the waterjet head  16  by rotating the supports  104  and/or  106  to achieve the perpendicular edge  158 B along the entire length of the cut  158  extending along the line  166 . The tilt control assembly  102  maintains the tilt plane at a constant bevel control angle relative to the direction of travel of the waterjet head  16 . 
     More specifically, at one point in the line segment  166 A, a vertical line  170 A is drawn for reference. The axis of the waterjet head  16  when it intersects the line  170 A is represented by a line  172 A. The lines  170 A and  172 A form a tilt angle  174 , and lie in a common tilt plane. Along the line segment  166 A, this common tilt plane lies in the Y direction, perpendicular to the line segment  166 A and to the direction of travel of the waterjet head  16  along the line segment  166 A. In this example, the bevel control angle is ninety degrees. 
     When the moving waterjet head  16  completes the cut  158  along the line segment  166 A and reaches the corner at the line segment  166 B, the tilt control assembly  102  rotatably adjusts the positions of the supports  104  and  106  in order to place the tilt plane in the X direction and to maintain the tilt plane at the ninety degree bevel control angle to the line segment  166 B and to the direction of travel of the waterjet head  16 . At one point in the line segment  166 B, a vertical line  170 B is drawn for reference. The axis of the waterjet head  16  when it intersects the line  170 B is represented by a line  172 B. The lines  170 B and  172 B continue to form the tilt angle  174 , and continue to lie in the common tilt plane. At the ninety degree comer where the line segment  166 A meets the line segment  166 B, the tilt control assembly  102  rotatably adjusts the supports  104  and  106  to maintain the constant ninety degree bevel control angle between the tilt plane and the direction of movement of the waterjet head  16 . 
     At the ninety degree corner where the waterjet head  16  moves from the line segment  166 B to the line segment  66 C, the tilt control assembly  102  again rotates the supports  104  and  106  to keep the tilt plane at the constant bevel control angle, perpendicular to the direction of travel of the waterjet head  16 . At one point in the line segment  166 C, a vertical line  170 C is drawn for reference. The axis of the waterjet head  16  when it intersects the line  170 C is represented by a line  172 C. The lines  170 C and  172 C continue to form the tilt angle  174 , and continue to lie in the common tilt plane. The bevel control angle of ninety degrees relative to the direction of travel is maintained. The line  172 C is inclined oppositely to the line  172 A because the direction of travel of the waterjet head  16  along line segment  166 C is opposite to the direction of travel along the line segment  166 A. 
     The bevel control angle can be an angle different from ninety degrees if desired. The ninety degree angle is preferred because it minimizes the size of the tilt angle  174  required to obtain the perpendicular finished edge  158 B. The size of the tilt angle needed to produce a perpendicular edge  158 B depends on the material and thickness of the workpiece, the speed of movement of the waterjet head  16  and other factors. The tilt angle for a particular job can be determined by experimentation with trial runs or by past experience. The line  166  seen in FIG. 6 includes straight line segments and sharp ninety degree comers. However, the invention is applicable to any cutting line including curved line segments, radiused corners and any other shapes. Regardless of the configuration of the path, the tilt control assembly  102  can operate to maintain a constant bevel control angle. 
     Also, the tilt angle is chosen to achieve the edge orientation that is desired. FIG. 2 illustrates the tilt angle selected to achieve an edge  158 B that is perpendicular to the top surface  162 . A smaller angle or a tilt in the opposite direction may be selected to achieve a positive beveled edge. A larger angle may be selected to achieve a reverse or negative beveled edge. The bevel control angle can be varied along the path of cutting if a non-uniform edge is desired, for example, beveled on one portion of the finished part and perpendicular on another portion. 
     Methods and apparatuses of the present invention thereby provide an elegant and effective solution to many otherwise unresolved problems of the prior art. For example, a tilt control assembly of the invention is a relatively compact and inexpensive system that can be used to achieve a wide range of desired tilt angles for non-contact cutting tools. Similarly, a method of the invention can be used to control the tilt of a non-contact cutting tool to effectively control the bevel of a workpeice cut in a relatively simple and inexpensive manner. 
     Those knowledgeable in the art will appreciate that discussion of preferred and exemplary embodiments of the present invention has been made herein for purposes of illustrating the known best modes of practice of the invention, but that many other invention embodiments may be practiced. By way of example, although preferred embodiments of the invention are directed to a tilt control assembly for use with a non-contact waterjet cutting tool, the invention may be useful with other non-contact cutting tools, and with contact cutting tools such as drills and the like. With reference to preferred invention embodiments for practice with non-contact cutting tools, it will be appreciated that the invention may be useful when practiced with non-contact cutting tools other than waterjets, with lasers, plasma cutters and torches as examples. 
     Further, although invention embodiments have been illustrated that include two eccentric supports, other invention embodiments may utilize other combinations of different types of supports. By way of example, a single eccentric support with a second, non-moving pivotal support may prove useful for some applications. Also, a single eccentric support with a second movable, but non-eccentric, support (e.g., X movable only) may prove useful for other applications. By way of still further example, although apparatuses have been illustrated with supports disposed generally vertically from one another, other invention embodiments may have supports oriented in a generally horizontal direction. Accordingly, description herein of exemplary invention embodiments should not be taken to limit the scope of the appended claims.