JP5586238B2 - High dynamic 3D machining system of workpiece using laser beam - Google Patents

Description

  The present invention relates to a system in which a laser beam transmitted through an optical fiber cable is guided by a joint arm of a robot to a workpiece to be processed. This type of system / device is generally known from US Pat.

  Three-dimensional machining of parts (hereinafter referred to as workpieces) is becoming increasingly important in manufacturing, especially for welding near net shape parts, or for trimming and trimming parts after reshaping operations. ing.

In particular, when the surface or contour of the workpiece to be machined by the laser beam is not located in a plane (hereinafter, referred to as a three-dimensional contour), luer over arm robot can be freely programmed movement sequence The use of provides a great degree of design freedom, reduces capital investment and provides acceptable manufacturing accuracy.

The output range of more than 1 kW, machining of 3-dimensional contour of the workpiece using the A over arm robot and the laser beam is carried out mainly by a solid-state laser (YAG, diode or fiber lasers). The laser beam of this type of laser can be advantageously guided over a length of several meters through a fiber optic cable containing one or more optical fibers, so that clearly the laser beam is directed to the robot arm The opportunity to guide to the robot hand via the fiber optic cable outside of is provided. The robot hand is provided with a processing lens system for focusing the laser beam on the workpiece.

  Regardless of whether the laser beam emanating from the laser source is guided through only one optical fiber or through a plurality of optical fibers grouped together in a single optical fiber cable, Laser beam is intended to refer to a laser beam having a beam axis.

  Patent Document 1 discloses a robot hand for three-dimensional processing of a workpiece. It is stated that a plug connector is disposed on an optical fiber cable in one hand axis constituting the fourth axis of a 5-axis robot. The connector can be a plug-and-socket connector or a screw-in connector.

  In order to protect against mechanical overload, the fiber optic cable is protected, for example, by a spiral sheath. It is stated that an optical lens system is incorporated in the plug, by which the laser beam is collimated using a method according to the prior art. It has been pointed out that the optical lens system that collimates the laser beam can also be a separate assembly located outside the plug and socket connector on the fiber side, ie outside the plug.

  When the laser beam is coupled into the robot hand in this way, the beam axis of the laser beam guided in the optical fiber of the optical fiber cable and the optical axis of the processing lens system of the robot hand do not coincide with each other. It will be apparent to those skilled in the art that they are offset and tilted relative to each other depending on the tolerance of the volume.

  However, since the laser beam travels only a relatively short distance inside the robot arm (which means that the beam path between the end of the fiber and the processing lens system is short), the laser beam in the processing lens system The point of incidence of the laser axis is still close enough to the point of passage of the optical axis, so that the laser beam is not weakened in this beam path in the robot hand.

  However, the disadvantage of this method of guiding the laser beam to the processing lens system and focusing the laser beam on the workpiece by the processing lens system is that the optical fiber cable that follows the movement of the robot arm has a high dynamic movement of the hand axis. Although it is not necessary to follow this, it is subjected to mechanical stress continuously. This stress should be damped by the sheath, which also limits the mobility of the optical fiber.

  In general, optical fibers should not be bent to bend radii of less than 150 mm, so if the robot hand moves along a rough workpiece, the fiber can be damaged due to kinks.

  In addition, fiber optic cables are more susceptible to damage from uncontrolled rebound in the case of high dynamic movement.

  In general, when an optical fiber is damaged, the fiber optic cable must be replaced, which is expensive and causes downtime. In this case, the distance between the processing location and the laser source can be several meters, for example 50 m, even when mating with a rapid-action coupling connector, It should be noted that the replacement of the fiber optic cable means that it takes a very long time.

  Patent Document 2 discloses a robot that performs industrial work using a laser beam, and the laser beam is guided into an optical fiber arranged inside a joint arm of the robot.

  Because optical fibers are susceptible to damage and have a small bend radius (100 mm to 200 mm), incorporating an optical fiber in this manner to guide a laser beam (into the robot arm) is for use in high dynamic robots. Not suitable.

  In both of the prior art solutions described above, the fiber optic cable moves with the robot arm and is therefore susceptible to dynamic stress, thereby shortening its useful life. It is the weakest link in the beam path and is considered a wear part.

  The optical fiber can act as a transport for the injected laser beam, or it can operate as the laser itself, ie, a fiber laser.

  The fiber laser includes an active fiber, such as a glass fiber doped with ytterbium or erbium and connected to the transmission fiber by a fusion splice. Since the length of the active fiber is limited due to undesired side effects, the total length of the fiber optic cable can reach the place where the laser beam is coupled into the beam path or where the laser beam acts. It is determined invariantly by the length of the transmission fiber guided to. The active fiber and transmission fiber constitute a substantially monolithic assembly, which must restore the fusion spliced to the active fiber from scratches for damage to the transmission fiber and subsequent replacement of the transmission fiber. Means that is necessary. In order to avoid mechanical stress on the transmission fiber, this fiber is connected to the process fiber in practical applications, and thus is divided into several parts: active fiber, transmission fiber and process fiber. The movement of the formed fiber optic cable is limited by the portion of the process fiber.

  Process fibers are made-to-order fibers that can be easily replaced via fiber-fiber couplings, which can be plug-and-socket connectors or threaded connectors. However, fiber-to-fiber coupling significantly degrades beam quality, in particular it is also due to an increase in beam diameter. This will be described using an example.

  Transmission fibers are, for example, 50 μm in diameter and are coupled to larger diameter process fibers, for example 100 μm, due to the inevitable alignment errors and tolerances of fiber-fiber coupling. By doubling the diameter, when the beam strikes the workpiece, the beam density across the beam cross-section is reduced by a factor of four, thereby reducing the processing speed and thus increasing the cycle time. Become. The overall efficiency of the machining process is reduced.

  Thus, if the need to incorporate process fibers (to fiber optic cables) can be lost, it is a welcome improvement.

Known from US Pat. Nos. 6,099,066 and 5,639,959 is a welding robot in which a laser beam in a robot arm is guided to a head for focusing the laser beam through a series of internal mirrors. This document does not provide any information on how the laser beam is delivered from the laser source to the required coupling location on the robot arm and how it is coupled there. It can be assumed that the intended laser source is a CO ₂ laser, but it emits a laser beam with a very high beam quality compared to a laser beam guided by an optical fiber. Due to events that occur in the optical fiber, the beam shape and beam caustic change so that the approximately Gaussian distribution of beam intensity changes to a top head distribution.

German Patent Invention No. 4335367C2 Specification European Patent No. 1579996B1 European Patent No. 04440002B German Patent Application Publication No. 69012307T3 Specification

The present invention is a problem to be solved is to provide a system for processing a workpiece 3-dimensionally by using a laser beam, the system without exposing the optical fiber cable to the mechanical stresses, A over arm type It operates by guiding a laser beam into a fiber optic cable using a robot.

Problems which the invention is filed, a system for processing high dynamic 3-dimensional workpieces by laser beam, a luer over beam-type robot having a robot frame and articulated arms, the fixed end of the arm attached to the robot frame, machining lens system to the free end of the arm is arranged, which lens system defines an optical axis, a over arm robot, an optical fiber cable, one end connected to the articulated arm, And a system comprising a fiber optic cable with which a laser beam having a beam axis is coupled into an articulated arm.

  The fiber optic cable is connected to the fixed end of the articulated arm so that the laser beam is guided through the entire articulated arm. In order to be able to guide a laser beam with uniform beam quality through the joint arm, the end of the fiber optic cable from which the laser beam exits is indirectly connected to the fixed end of the joint arm via an alignment unit Is done. The alignment unit comprises a collimating lens system and at least two alignment mirrors, each of the alignment mirrors rotating about at least one rotation axis and moving along at least one translation axis, The rotation axis and the translation axis are perpendicular to each other so that the beam axis of the laser beam can coincide with the optical axis. The fact that the beam axis can always be aligned with the optical axis allows the end of the fiber optic cable to be connected to the articulated arm using a commercially available plug-and-socket connector or screw-in connector. .

  The connection between the fiber optic cable and the alignment unit is made through a plug located on the fiber optic cable and a jack located on the housing of the alignment unit, which together form a fast acting lock. It is recommended to do.

  One advantage is that it can consist of only a fiber laser and a transmission fiber, or even simply a fiber laser, since the fiber optic cable is not subjected to mechanical stress, in which case the machine Contrary to the case where mechanical stress is applied, fiber-to-fiber coupling that reduces beam quality for coupling to additional process fibers as wear parts is eliminated.

  The alignment unit preferably also comprises a redirection mirror that can rotate about the third axis of rotation and move along the third axis of translation, so that the alignment unit has 6 degrees of freedom for alignment. Provided, the jack of the alignment group housing can be placed anywhere.

  It is preferable that the lens of the processing lens system and the lens of the collimating lens system can be translated relative to each other.

  By moving the lens of the processing lens system, the focal position can be adjusted for various distances from the processing lens system, which means that workpieces with different thicknesses are processed at a constant distance from the workpiece support surface. Is indispensable.

  By moving the lens of the collimating lens system, the focal length of the lens can be adjusted to the divergence of the laser beam as it exits the optical fiber cable.

  The invention will be described in more detail on the basis of examples and with reference to the drawings.

1 shows a schematic diagram of a system / apparatus disclosed by the present invention in a first example. FIG. 3 shows a schematic diagram of an alignment unit of the system / device disclosed by the present invention in a second example.

System / apparatus illustrated in Figure 1, the robot frame 1 comprises a luer over arm type robot having a and articulated arm 2 having a plurality of axes, the machining lens system 43 is arranged on the free end of the articulated arm This lens system defines an optical axis 4 for the beam path inside the articulated arm 2. The other end of the joint arm 2 is fixedly attached to the robot frame 1.

  The joint arm 2 is hollow, and a free opening of, for example, 30 mm extends along its entire length. A mirror positioned inside the joint arm 2 changes the direction of the laser beam 11 inside the joint arm 2. The spacing between the mirrors always remains the same regardless of the movement of the articulated arm 2, thereby addressing undesired variations in beam diameter. The direction of the optical axis 4 is changed via a mirror, and the fixed end of the joint arm 2 is in a stable space position in the direction of the first axis of the joint arm 2 when counted from the fixed end. The movement of the arm 2 is irrelevant.

  One end of the optical fiber cable 5 is indirectly connected to the fixed end of the joint arm 2 via the alignment unit 6. This design of the alignment unit 6 is intended to ensure that the incident laser beam 11 emanating from the fiber optic cable 5 can be aligned as follows. That is, the beam axis 10 of the laser beam coincides with the optical axis 4, that is, is aligned with the optical axis, and this optical axis is the first axis of the joint arm 2 at the fixed end of the joint arm 2. It is in a stable space position in the direction of.

  The connection between the optical fiber cable 5 and the alignment unit 6 is performed by a plug 7 disposed on the optical fiber cable 5 and a jack 9 disposed on the housing 8 of the alignment unit 6. Preferably, a quick action lock is formed. Since alignment is done at a later time, there are no specific requirements that the mechanical tolerances of the connection must meet.

  Since the end of the fiber optic cable 5 is indirectly connected to the fixed end of the joint arm 2 via a rigid connecting element, the fiber optic cable 5 remains fixed regardless of the movement that the joint arm 2 performs. is there. This means that the cable does not move and is therefore not subjected to dynamic stress.

  As a result, it may be possible to use an optical fiber cable 5 consisting solely of a fiber laser or consisting only of a fiber laser and a transmission fiber. That is, the fiber optic cable 5 is not subjected to mechanical stress and therefore is not subject to any significant wear and therefore does not need to be coupled to a process fiber that may be replaced as a wear part.

The optical fiber cable 5 is capable of performing only serves to transmit the arranged laser source or Raa over arm robot away the laser beam 11.

  The position of the beam axis 10 of the laser beam 11 emerging from the end of the optical fiber cable 5 is largely determined by the nature of the end of the optical fiber cable 5 and the connection formed by the plug 7 and jack 9. The inevitably generated deviation from the position of the beam axis 10 with respect to the optical axis 4 in the x direction, the y direction and the z direction and the inclination of the beam axis with respect to the optical axis 4 indicate that the laser beam 11 is directly coupled into the joint arm 2. If so, the beam is not guided coaxially with the optical axis 4 in the joint arm 2.

  Since the path length inside the joint arm 2 is long and there are a plurality of direction changes by the mirror incorporated in the joint arm 2, errors increase. Thus, according to one scenario, a part of the laser beam 11 does not hit the built-in mirror, but may be absorbed or reflected by other parts of the articulated arm 2 on which they hit. Such undesired absorption heats the joint arm 2 and thus damages it. Undesirable reflections degrade the beam quality of the laser beam 11.

  In order to be able to guide the laser beam 11 into the articulated arm 2 without increasing the complexity of the connection of the end of the fiber optic cable 5 while maintaining the same uniform beam quality, Before the laser beam 11 is guided into the joint arm 2, the alignment unit 6 is used to align the beam axis 10 with the optical axis 4.

  The alignment unit 6 includes two alignment mirrors 12.1, 12.2, and a collimating lens system 13. The collimating lens system 13 is optically arranged immediately downstream of the end of the optical fiber cable 5 in the direction of the beam, followed by two alignment mirrors 12.1, 12.2, followed by In the direction of the beam, the built-in mirror of the joint arm 2 is arranged all the way to the processing lens system 3.

  The collimating lens system 13 is designed as follows. That is, on the one hand, the divergent laser beam 11 emerging from the end of the optical fiber cable 5 is made parallel, so that the laser beam 11 is guided in the joint arm 2 as a bundle of parallel light with a constant beam diameter. Enable. On the other hand, the laser beam can be adapted so that the beam density across the beam cross-section is adapted, whereas these mirrors can be resistant to stresses so as to avoid the possibility that the built-in mirrors are overheated and consequently deformed. 11 is enlarged.

  The parallel laser beam 11 is then redirected via the two alignment mirrors 12.1, 12.2. Each of the mirrors can move about at least one axis of rotation and along one translation axis.

  The two required rotation axes and the two required translation axes are perpendicular to each other. The beam axis 10 is aligned with the optical axis 4 by appropriately moving and twisting the alignment mirrors 12.1, 12.2.

  In the second example shown in FIG. 2, the alignment unit also has a direction changing mirror 14 in addition to the two alignment mirrors 12.1, 12.2. Therefore, in contrast to the first example, it is not necessary to arrange the jack 9 in the housing 8 of the alignment unit 6 in the direction of the first axis of the robot, and it is possible to position it at any place instead. In this case, the direction changing mirror 14 serves to change the direction so that the laser beam 11 emitted from the end of the optical fiber cable 5 is directed toward the first alignment mirror 12.1. The alignment unit 6 including the two alignment mirrors 12.1 and 12.2 and the direction changing mirror 14 has six degrees of freedom in order to align the beam axis 10 with the optical axis 4.

  The distance between the surface of the workpiece and the free end of the articulated arm 2 designed to act as a machining head or cutting tip at the exit from the robot, ie at the free end of the articulated arm 2 Are controlled by capacitive or inductive ranging sensors and by targeted processing of sensor signals.

  Using the signal processed by the analysis unit, the robot position is changed by transmission to the robot control at a predetermined time.

  Control is done directly through the robot, not through external axes located on the robot head, which only complicates the overall design. In order to ensure tilt control and to avoid overshoot, the control strategy divides the region between the machining head / cutting tip and the workpiece surface into a far field and a near field. In the far field region, control is based on the distance between the workpiece and the machining head / cutting tip, and in the near field region, the distance to be maintained from the machining head / cutting tip (eg, 0). .2 mm to 2 mm) is used as the control variable.

DESCRIPTION OF SYMBOLS 1 Robot frame 2 Articulated arm 3 Processing lens system 4 Optical axis 5 Optical fiber cable 6 Alignment unit 7 Plug 8 Housing 9 Jack 10 Beam axis 11 Laser beam 12 Alignment mirror 13 Collimating lens system 14 Direction change mirror

Claims (4)

A system for highly dynamic three-dimensional processing of a workpiece by a laser beam,
A luer over beam-type robot having a robot frame (1) and joint arm (2), the fixed end of the arm is attached to the robot frame (1), machining the lens system to the free end of said arm ( 3) is arranged, the lens system defines an optical axis (4), and a over arm robot,
An optical fiber cable (5) connected to the fixed end of the joint arm (2) so that a laser beam (11) having a beam axis (10) can be coupled into the joint arm (2); In the system with
The optical fiber cable (5) is indirectly connected to the fixed end of the joint arm (2) via an alignment unit (6);
The alignment unit (6) comprises a collimating lens system (13) and at least two alignment mirrors (12.1, 12.2);
Each of the mirrors can pivot about at least one axis of rotation and move along at least one translation axis;
Wherein the rotation axis is translational axes perpendicular to each other, whereby said beam axis (1 0) Ri is possible to name that coincides with the optical axis (4),
System wherein the alignment unit (6) is a third pivot about a rotational axis and wherein Rukoto the direction changing mirror (14) also Yusuke which can be moved along the third translational axis.   The optical fiber cable (5) and the alignment unit (6) are connected to a plug (7) disposed on the optical fiber cable (5) and a jack (9) disposed on the housing of the alignment unit (6). The system of claim 1 wherein the plug and the jack together form a quick-acting lock. System according to claim 1, characterized in that the fiber optic cable (5) comprises a fiber laser and a transmission fiber .   System according to claim 1, characterized in that the lens of the working lens system (3) and the lens of the collimating lens system (13) can translate relative to each other.

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