Abstract:
Multi-axis laser cutting systems are provided. The cutting systems include a multi-axis, relatively high acceleration drive system, which includes drives that are configured to generate balanced inertial forces. In some implementations, the drives operate according to a polar coordinate systems.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to multi-axes laser processing machines. 
       BACKGROUND 
       [0002]    A number of commercially available laser processing machines include two separate axis systems, a first axis system for relatively low acceleration movement of the processing head (e.g., laser cutting head) over relatively long distances, and a second axis system for relatively high acceleration movement of the processing head in a relatively restricted space. In some cases, the two axis systems cannot operate simultaneously. 
         [0003]    It has been proposed, e.g., in WO 2006/075209, to coordinate the two axis systems. The system disclosed in WO 2006/075209 includes a moving member that moves the processing head over relatively long distances along Cartesian axes (x, y), a pair of slides on the moving member that are configured to move the processing head over relatively short distances along Cartesian axes (u, v), and mobile balancing weights which are operatively associated with the slides. The presence of the mobile balancing weights is said to enable “a drastic reduction in the transmission of undesirable vibrations from the moving member to the supporting structure of the machine.” The mobile weights are displaced by their own actuators, separate from the actuators that drive movement of the moving member and slides, in a direction opposite to the direction of movement of the slides. Thus, the proposed laser processing machines include, in addition to the low acceleration axis and high acceleration axis systems, a separate axis system that is required to reduce vibrations during movement of the processing head. 
       SUMMARY 
       [0004]    The present invention features, in one aspect, a laser processing machine having separate low acceleration and high acceleration axis systems which are coordinated with each other. Inertial forces in the high acceleration axis system arc balanced without the need for a separate counterbalance drive system. The low acceleration and high acceleration axis systems are capable of operating simultaneously during machine operation. 
         [0005]    The X-Y Cartesian coordinates system is used for the low acceleration axes, while the polar coordinates system is used for the high acceleration axes. The use of the polar coordinate system with the high acceleration axes allows the axes to be configured so that inertial forces are balanced at all times during operation, without the need for an independently driven counterbalance system. 
         [0006]    In one aspect, the invention features a laser processing machine, comprising: (a) a laser processing head; (b) a multi-axis system, comprising a mounting axis on which the processing head is mounted, the mounting axis including a counterbalance and a drive, and being configured so that the drive moves the counterbalance and the processing head in a manner so that the inertial force generated by movement of the processing head is balanced by the movement of the counterbalance and the mounting axis is substantially continuously balanced during operation; and (c) a long travel system, on which the multi-axis system is mounted for coordinated movement. The multi-axis system is configured to move the processing head over relatively shorter distances and at relatively higher acceleration than the long travel drive system. 
         [0007]    Some implementations may include one or more of the following features. The multi-axis system is a polar coordinate system defining an R-axis and a W-axis. The mounting axis is the R-axis is of the polar coordinate system. The W-axis of the multi-axis system comprises a disc and two drive motors on opposite sales of the disc, the inertial forces of the drive motors being substantially balanced. The long travel drive system is a Cartesian coordinate system. The multi-axis drive system and long travel drive system are configured for simultaneous movement. The mounting axis comprises a pair of ball screw transmissions driven by the drive to move the counterbalance and processing head in opposite directions at substantially the same speed. The R-axis is mounted on the W-axis. The machine bather includes a Z-axis configured to provide vertical movement of the processing head. The multi-axis system is configured so that the Z-axis will be stationary during movement of the R-axis and W-axis. 
         [0008]    In another aspect, the invention features a laser processing machine, comprising: (a) a laser processing head; (b) a multi-axis polar coordinate system comprising an R-axis and a W-axis, one of the axes being a mounting axis on which the processing head is mounted, the mounting axis being configured so that the mounting axis is substantially continuously balanced during operation; and (e) a long travel system, on which the multi-axis system is mounted for coordinated movement. The multi-axis system is configured to move the processing head over relatively shorter distances and at relatively higher acceleration than the long travel drive system. 
         [0009]    Some implementations may include one or more of the following features. The mounting axis is the R-axis of the polar coordinate system. The W-axis of the multi-axis system comprises a disc and two drive motors on opposite sides of the disc, the inertial forces of the drive motors being substantially balanced. The long travel drive system is a Cartesian coordinate system. The multi-axis drive system and long travel drive system are configured for simultaneous movement. The mounting axis comprises a counterbalance and a pair of ball screw transmissions driven by a single drive to move the counterbalance and the processing head in opposite directions at substantially the same speed. The R-axis is mounted on the W-axis. The machine further includes a Z-axis configured to provide vertical movement of the processing head. The multi-axis system is configured so that the Z-axis will be stationary during movement of the R-axis and W-axis. 
         [0010]    The invention also features, in another aspect, a method of processing a workpiece comprising; (a) using a multi-axis system to move a processing head relatively short distances during operation of the processing head, the multi-axis system comprising a mounting axis on which a processing head is mounted, the mounting axis including a counterbalance and a drive, and being configured so that the drive moves the counterbalance and the processing head in a manner so that the inertial force generated by movement of the processing head is balanced by the movement of the counterbalance and the mounting axis is substantially continuously balanced during operation; and (b) using a long travel system, on which the multi-axis system is mounted for coordinated movement, to move the processing head relatively longer distances during operation of the processing head. 
         [0011]    In yet a further aspect, the invention features a method of processing a workpiece comprising: (a) using a multi-axis polar coordinate system to move a processing head relatively short distances during operation of the processing head, the multi-axis system comprising a mounting axis configured so that the mounting axis is substantially continuously balanced during operation; and (b) using a long travel system, on which the multi-axis system is mounted for coordinated movement, to move the processing head relatively longer distances during operation of the processing head. 
         [0012]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0013]      FIG. 1  is a perspective view of a laser cutting machine. 
           [0014]      FIG. 2  is a perspective view diagrammatically indicating the multi-axis systems of the cutting machine of  FIG. 1 . 
           [0015]      FIG. 3  is a diagrammatic view showing the path of a laser beam through the axis system shown in  FIG. 2   
           [0016]      FIGS. 4-6  are perspective views and  FIG. 7  is a side view of a multi-axis system. 
           [0017]      FIG. 8  is a perspective view of the R-axis of the multi-axis system. 
           [0018]      FIG. 9  is a partially cut-away view showing the torque motor and transmission of the R-axis. 
           [0019]      FIG. 10  is a perspective view of a portion of the W-axis (prior to assembly of all components).  FIG. 10A  is a detailed view of the transmission of the W-axis.  FIG. 10B  is a perspective view of the assembled W-axis and R-axis. 
           [0020]      FIGS. 11 and 12  are perspective views of the Z-axis of the multi-axis system, taken from different positions. 
           [0021]      FIGS. 13 and 14  are perspective views showing the Z-axis assembled with the R-axis and W-axis. 
       
    
    
     DETAILED DESCRIPTION 
     Overview 
       [0022]    Referring to  FIGS. 1-3 , a laser cutting machine  10  includes an enclosure  12 , a workpiece support  14 , a multi-axis system  16  configured to move in a polar (R-W) coordinate system, and a laser cutting head (not shown in  FIGS. 1-3 ) mounted on the multi-axis system. The multi-axis system is configured to move the cutting head over small distances with very high acceleration. As illustrated in  FIG. 2 , the multi-axis system  16  moves, as a whole, with low acceleration, large scale movements on an x-y Cartesian coordinate system. Movement of the multi-axis system on the x-y Cartesian coordinate system is coordinated with, and can proceed simultaneously with, movement in the R-W polar coordinate system. For example, the multi-axis system  16  may be mounted to move in the Y direction on rails  18 , which are in turn movable in the X direction along rails  20 , as shown. This x-y axis system is conventional, and will not be discussed herein. 
         [0023]    The multi-axis system  16  provides high acceleration, movement over small distances using a polar coordinate system. System coordinates are a radial coordinate R that represents the radial distance from a pole  0 , and an angular coordinate W that represents the counter-clockwise angle from the a 0° ray referred to as the polar axis. The multi-axis system includes an R-axis which moves the laser cutting head to a desired radial (R) coordinate, and a W-axis which moves the laser cutting head to a desired angular (W) coordinate. The multi-axis system also allows the cutting head to be moved vertically (raised or lowered relative to the workpiece), in the Z direction. Thus, the multi-axis system  16  includes an R-axis, a W-axis, and a Z-axis that are assembled into a single unit to provide coordinated movement in all three dimensions. Details of these drives and their operation will be discussed below. 
         [0024]    In preferred implementations, the R-W axes have a travel of at least about 75 mm, preferably at least about 100 mm in the R direction, and an angular range of at least about 75°, preferably at least about 85 °, e.g., 88°. Preferably, the speed of the R-W axes is at least about 100 m/min, more preferably at least about 120 m/min, and the acceleration is at least about 30 m/s 2  and more preferably at least about 50 m/s 2 . 
         [0025]    The laser beam path through the multi-axis system, which also will be discussed in more detail below, is shown diagrammatically in  FIG. 3 . 
         [0026]    In preferred implementations, as many components as possible are mounted on the Y axis housing, so that the R and W axes are as light as possible, allowing optimal acceleration and velocity of the R-W axes. In some implementations, the R-axis components weigh less than about 40 kg, preferably less than about 30 kg, while the R-axis components and W-axis components combined weigh less than about 100 kg, preferably less than about 90 kg. Preferably, the R, W and Z axes combined weigh less than about 130 kg, more preferably less than about 110 kg. 
         [0027]    Assembled Multi-Axis Unit 
         [0028]    We will first briefly discuss the assembled multi-axis unit, and then will discuss the components of each of the R-axis, W-axis and Z-axis in detail. 
         [0029]    Referring to  FIG. 9 , the R-axis  140  moves using a ball screw transmission, as will be discussed below. The laser cutting bead  3  is mounted on the end of the ball screw  34 , and the counter balance  4  is mounted on the nut  35 A of ball screw  35 . The R-axis moves the cutting head  3  and a counter balance  4  in opposite directions, so radial inertial forces are balanced. Balancing of the inertial forces reduces or eliminates the tendency of the system to vibrate during operation. 
         [0030]    Referring to  FIGS. 10 ,  10 A the W-axis drives are mounted on Y-axis housing  13 , and rotate the W axis through arcuate gear segments  2 . As will be discussed below, the W-axis drives produce equal inertial forces having opposite directions. Thus, the forces on the W-axis are balanced, and thus the W-axis does not contribute to vibration of the multi-axis system. 
         [0031]    A central bending mirror  7  ( FIG. 7 ) is installed on the W-axis housing  1  and rotates with it, always directing the laser beam towards an autolas mirror  17  ( FIG. 7 ). As a result, the laser beam will follow the path of the W-axis and thus the cutting head. 
         [0032]    The R-axis  140  is installed in the W-axis housing  1  and rotates with rotation of the W-axis. 
         [0033]    Referring to  FIG. 7 , the Z-axis is driven by drives  9  through ball screws  10  ( FIG. 7 ). The Z-axis is guided by four guides  11  on plate  12 . The Z-axis and the entire multi-axis system  16  is mounted on the Y axis carriage  160  ( FIG. 4 ), thus allowing coordinated simultaneous movement in the R-W and x-y axes. 
         [0034]    R-Axis Components 
         [0035]    As discussed above, the R-axis  140  is configured to provide linear movement of the cutting head to a given radial coordinate. 
         [0036]    Receiving to  FIGS. 8 ,  9 , the R-axis  140  includes a torque motor  32  which rotates a ball nut  34 A and ball screw  35 . As shown in detail in  FIG. 9 , the hall screw  34  moves through the torque motor  32 . The cutting head  3  is connected to the outside end of the ball screw  34 . The counterbalance  4 , which is equal in weight to the cutting head  3 , is mounted to the nut  35   a  which moves along hall screw  35 . 
         [0037]    During operation, the cutting head  3  and counterbalance  4  move along the ball screws  34  and  35  in opposite directions at the same speed to balance inertial forces. The cutting head  3  and counterbalance  4  are driven, through the ball screws  34 ,  35  by the same motor (torque motor  32 ). Because the cutting head and counterbalance are driven by the same motor, inertial forces are always in balance when the cutting head is in motion, without the need to activate a separate motor or separate counterbalancing mechanism. 
         [0038]    The R-axis drive  140  further includes a pair of mechanical stops  36  and  37  ( FIG. 8 ) provided for safety and a rotary encoder  38 , provided for positioning and motor control. If desired, the cutting head  3  may be mounted on the R-axis by an automated coupling device such as those that are well known in the machine installation art. 
         [0039]    W-Axis Components 
         [0040]    The W-axis is configured to provide rotational movement of the cutting head, to a given angular coordinate. Referring to  FIGS. 10 and 10B , the W-axis includes a rotatable W-axis housing  1 , and, mounted on the W-axis housing  1 , the R-axis  140 . Thus, the R-axis  140  rotates with the W-axis. The W-axis housing  1  rotates about a center bearing  42 , resulting in smooth rotational movement of the cutting head. 
         [0041]    Two torque motors  44 ,  46  ( FIG. 10 ) are provided for driving a transmission  48  that rotates the W-axis housing  1 . Referring to  FIG. 10A , the transmission  48  includes a pinion  52  and an arcuate rack  54 . The arcuate rack  54  is made up of the arcuate gear segments  2 , discussed above, which are engaged by the pinions. The torque motors are mounted on opposite sides of the Y-axis housings, and the inertial forces create by the two motors are equal and opposite, so that the inertial forces balance each other. A rotary encoder  50  is provided to control the motors. 
         [0042]    Because the motors are mounted on a Y-axis housing  13 , the amount of weight that is being rotated is reduced, allowing higher acceleration of the W-R axes. 
         [0043]    As discussed above, a central bending mirror  7  ( FIGS. 7 ,  10 B) is installed on the W-axis housing  1  and rotates with it, so that the laser beam is always directed towards an autolas mirror  17  that then directs it to the cutting head  3  ( FIG. 7 ). The mirror  7  is connected to a beam bellow  58  and to a gas channel  60 , to enclose a path for the laser beam. Another beam bellow  62  is connected to the opposite side of the gas channel  60 . The beam bellow  58  is connected to the cutting head, while the beam bellow  62  is connected to the counterbalance  4  in a manner so that as the cutting head  3  and counterbalance  4  move one of the bellows is compressed while the other is extended. This prevents the gas in the beam path from being compressed, and prevents a vacuum from being created (see  FIG. 10B ). 
         [0044]    Z-axis guides  11  ( FIGS. 10B ,  7 ) are provided, to guide vertical movement of the R and W axes by the Z-axis drives  9 . These guides are mounted to plate  12  ( FIG. 7 ) which in turn is connected to W axis housing through central bearing  43  thus when the W axis rotates the guides  11  remain stationary. The Y axis housing  13  includes a mechanical stop  66  for the W-axis for safety. 
         [0045]    Z-Axis Components 
         [0046]    Referring to  FIG. 11 , the Z-axis  9  includes two motors  70 , each of which drives a ball screw transmission  72  that includes ball screws  10  ( FIG. 7 ) and ball screw support bearings  74 . Movement is guided by the Z-axis guides  11 , as discussed above. Part of the weight of the multi-axis drive system and cutting head is counterbalanced by counterbalance springs  78  ( FIG. 12 ) which are built into the Z-axis guides. Z-shaft scrapers  80  remove contamination from Z-axis guides  11 . 
         [0047]    It is not necessary to counterbalance the inertial forces of the motors  70 , because the cutting head does not move in the Z-direction during cutting operation. 
         [0048]    Referring to  FIGS. 11 and 14 , the laser beam passes through the Z-axis, from the center mirror  7 A installed on the Y-axis housing to Z beam tube  76 , center bending mirror  7  and Aatolas mirror  17 , discussed above and thus to the cutting head. 
         [0049]    Other Embodiments 
         [0050]    A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. 
         [0051]    For example, while a laser cutting head has been described above, other types of laser processing heads may be used, and the laser processing machine may be used for other types of workpiece processing such as laser welding. 
         [0052]    Accordingly, other embodiments are within the scope of the following claims.