INITIAL DISTANCE APPROACH FOR LASER PROCESSING

• US 20170361400A1
• Filed: 09/01/2017
• Published: 12/21/2017
• Est. Priority Date: 03/03/2015
• Status: Active Application

• Current Assignee: Trumpf Laser- und Systemtechnik GmbH (TRUMPF SE + Co. KG)
• Original Assignee: Trumpf Laser- und Systemtechnik GmbH (TRUMPF SE + Co. KG)
• Inventors: Hagenlocher, Tobias
• Granted Patent: US 10,843,292 B2
• Time in Patent Office: Days
• CPC Class Codes: B23K 26/0342 Observing magnetic fields related to the workpiece
• CPC Class Codes: B23K 26/048 by controlling the distance between laser head and workpiece
• CPC Class Codes: B23K 26/0853 Devices involving movement of the workpiece in at least in two axial directions, e.g. in a plane
• CPC Class Codes: B23K 26/0884 in at least in three axial directions, e.g. manipulators, robots
• CPC Class Codes: B23K 26/21 by welding
• CPC Class Codes: B23K 26/361 for deburring or mechanical trimming B23K26/351 takes precedence
• CPC Class Codes: B23K 26/38 by boring or cutting
• CPC Class Codes: B23K 37/0235 the guide member forming part of a portal
• CPC Class Codes: B23K 37/04 for holding or positioning work
• CPC Class Codes: B23K 37/0461 Welding tables

Abstract

In an example method, a laser processing head is moved from an entrance region over a workpiece to a starting position above the workpiece. During this time, a distance control system is used to control the distance between the laser processing head and the workpiece based on measurements obtained from one or more distance sensors. Further, the laser processing head is moved from the starting position to a position beyond an edge of the workpiece. During this time, the distance control system is disengaged. When the laser processing head reaches the position beyond an edge of the workpiece, laser emission is initiated, and the laser processing head is moved back towards the starting position. Upon reaching the starting position, the distance control system is reengaged. The laser processing head is subsequently moved along a pre-determined path to cut the workpiece.

Claims

1. A method for approaching a starting position for laser processing a workpiece with a laser processing head having a distance sensor system, wherein the laser processing head is configured to perform a contour cut with respect to the workpiece starting from a workpiece edge of the workpiece, the method comprising:

providing position information relating to the starting position, wherein the starting position is provided at a working distance from a surface of the workpiece, and space information relating to a predetermined entrance area, wherein the predetermined entrance area at least partially extends at a distance to the surface of the workpiece, wherein the distance is larger than the working distance, wherein the predetermined entrance area is at a minimum distance from the starting position, the minimum distance allowing an adaptation of the distance of the laser processing head to the working distance during a movement of the laser processing head from the entrance area to the starting position;

moving the laser processing head through the entrance area in direction of the starting position and activating a distance control operation after entry of the laser processing head in the entrance area, wherein the distance control operation is based on the distance sensor system to control the distance of the laser processing head to the surface of the workpiece;

continuing the moving of the laser processing head from the entrance area to the starting position, while adapting the distance of the laser processing head from the workpiece to the working distance by the distance control;

continuing the moving of the laser processing head beyond the workpiece edge and, prior to the laser processing head passing the workpiece edge, deactivating the distance control and freezing a set distance of the laser processing head by a distance freezing operation;

turning on a laser emission from the laser processing head;

moving the laser processing head back to the workpiece edge and above the workpiece in direction of the starting position; and

passing the starting position with the laser processing head at the working distance under laser emission, and prior to the laser processing head passing the starting position or upon the laser processing head reaching the starting position, reactivating the distance control and deactivating the distance freezing of the laser processing head.

2. The method according to claim 1, wherein the distance control is deactivated and/or the distance freezing is activated at the starting position (27) is performed upon the laser processing head reaching the starting position.

3. The method according to claim 1,

wherein the laser processing head passes the starting position at the working distance.

4. The method according to claim 1, wherein the entrance area is defined as a volume or a spherical volume relative to the starting position.

5. The method according to claim 1, wherein the starting position is set outside of a tolerance range given for the workpiece edge.

6. The method according to claim 1, wherein the entrance area is positioned between an endpoint of a preceding laser processing movement of the laser processing head and the starting position, and

wherein the method further comprises

moving the processing head starting from the endpoint along a trajectory such that the laser processing head is initially at a safety distance from the workpiece and is subsequently lowered in a direction of the entrance area.

7. The method according to claim 1, wherein the entrance area is positioned outside of a tolerance range of the workpiece edge.

8. The method according to claim 1, further comprising defining the entrance area and the starting position to be arranged with respect to the workpiece such that, along a stretch from the entrance area to the starting position, a usability of the distance control operation is ensured.

9. The method according to claim 1, wherein movement of the laser processing head between the starting position and the edge, and outside of the edge, is performed in increments.

10. The method according to claim 1, wherein after deactivation and before reactivation of the distance control operation, the movement is continues towards a turning point and back from the turning point linearly.

11. The method according to claim 10, wherein a movement direction of the laser processing head between the starting position and the turning point lies in a plane that spans orthogonally to the normal to the workpiece at the starting position.

12. The method according to claim 10, wherein a projection line relating to a movement segment between the starting position and the turning point, encompasses an angle on the workpiece surface with respect to a normal to the workpiece edge at an intersection of the projection line with the edge, wherein the angle is between 0°

and 45°

.

13. The method according to claim 1, wherein, at the starting point, the laser processing head is aligned such that a propagation direction of the laser of the laser processing head corresponds to a normal to the workpiece at the starting position.

14. A machine tool comprising:

a laser processing system including a laser system;

a workpiece mount;

a laser processing head including a distance sensor system, wherein the laser processing head is optically coupled to the laser system and is configured to control a relative movement between the laser processing head and the workpiece mount for performing a contour cut of the workpiece, the contour cut beginning at a workpiece edge of the workpiece, and

a control unit configured to perform the method according to claim 1.

15. The machine tool according to claim 14, further comprising

an input device for inputting local information relative to the starting position and space information relating to the predetermined entrance area in dependence of

a geometry of the workpiece,

a tolerance range of the workpiece edge,

a speed with which the processing head is movable relative to the workpiece, and/or

an accuracy of a measurement of the distance sensor system,

such that the entrance area at least partly extends in a distance to the surface of the workpiece, wherein the distance is larger than the working distance, wherein the entrance area is at a minimum distance from the starting position, the minimum distance allowing an adaptation of the distance of the laser processing head to the working distance during a movement of the laser processing head from the entrance area to the starting position.

16. A method for cutting a workpiece, the method comprising:

obtaining position information with respect to the workpiece, the position information indicating;

a location of a starting position above the workpiece, and

a location of an entrance region above the workpiece;

moving a laser processing head to the entrance region;

upon arrival of the laser processing head at the entrance region, engaging a distance control system to control a distance between the laser processing head and the workpiece, wherein the distance control system is configured to control the distance between the laser processing head and the workpiece based on measurements obtained from one or more distance sensors;

moving the laser processing head from the entrance region to the starting position;

upon arrival of the laser processing head at the starting position, disengaging the distance control system;

moving the laser processing head from the starting position to a position beyond an edge of the workpiece;

upon arrival of the laser processing head at the position beyond the edge of the workpiece, initiating laser emission by the laser processing head;

moving the laser processing head from the position beyond the edge of the workpiece to the starting position, such that the laser emission is incident on the workpiece;

upon arrival of the laser processing head at the starting position, engaging the distance control system to control the distance between the laser processing head and the workpiece; and

moving the laser processing head along a pre-determined path to cut the workpiece.

17. The method of claim 16, wherein the entrance region is defined by a spherical volume around a reference point.

18. The method of claim 16, wherein when the laser processing head is positioned at the starting position, the laser processing head is aligned such that a direction of laser emission by the laser processing head is parallel to a normal of a surface of the workpiece.

19. The method of claim 16, wherein moving the laser processing head from the starting position to the position beyond the edge of the workpiece includes moving the laser processing head along a plane orthogonal to a normal of a surface of the workpiece to a return position beyond the edge of the workpiece.

20. The method of claim 16, wherein moving the laser processing head from the starting position to the position beyond the edge of the workpiece includes moving the laser processing head along a path between the starting position and a return position beyond the edge of the workpiece, wherein an angle between a projection of the path and a normal of the edge of the workpiece is between 0°

and 45°

.