US-12617040-B2 - Method for determining a minimum width and an attachment position of a microjoint and method for machining a workpiece

US12617040B2US 12617040 B2US12617040 B2US 12617040B2US-12617040-B2

Abstract

A method for determining a minimum width of a microjoint by which, when machining a workpiece, in particular a sheet-like workpiece, a workpiece part remains connected to a remaining workpiece of the workpiece. In the method, the minimum width of the microjoint is determined in dependence on at least one machining parameter which influences a relative position of the workpiece part in relation to the remaining workpiece during the machining of the workpiece. A further method determines an attachment position of such a microjoint and a still further method machines the workpiece.

Inventors

Florian Sepp
Simon Ockenfuß
Patrick Mach
Kai Etzel
Christoph Weiss

Assignees

TRUMPF Werkzeugmaschinen SE + Co. KG

Dates

Publication Date: 20260505
Application Date: 20221107
Priority Date: 20200506

Claims (14)

1 . A method for determining a minimum width of a microjoint by which, when machining a workpiece, a workpiece part remains connected to a remaining workpiece of the workpiece, which comprises: determining the minimum width of the microjoint in dependence on at least one machining parameter which influences a relative position of the workpiece part in relation to the remaining workpiece during the machining of the workpiece, wherein the machining of the workpiece includes thermal cutting of the workpiece with a machining beam; wherein the minimum width of the microjoint is determined in dependence on the at least one machining parameter in a form of a gas pressure of a cutting gas leaving a machining nozzle that acts on the workpiece part during a cutting free of the workpiece part from the remaining workpiece.
2 . The method according to claim 1 , wherein the minimum width of the microjoint at which a maximum upstanding height, by which the workpiece part stands up above the remaining workpiece, is not exceeded during a tilting of the workpiece part in relation to the remaining workpiece due to an effect of the gas pressure acting on the workpiece part.
3 . The method according to claim 2 , wherein the maximum upstanding height is not greater than a distance between the machining nozzle and the remaining workpiece, wherein the distance is less than 2 mm.
4 . The method according to claim 1 , wherein the workpiece is a sheet-shaped workpiece.
5 . The method according to claim 1 , wherein the machining beam is a laser beam.
6 . The method according to claim 3 , wherein the distance is less than 1 mm.
7 . A method for determining a minimum width of a microjoint by which, when machining a workpiece, a workpiece part remains connected to a remaining workpiece of the workpiece, which comprises: determining the minimum width of the microjoint in dependence on at least one machining parameter which influences a relative position of the workpiece part in relation to the remaining workpiece during the machining of the workpiece, wherein the machining of the workpiece includes a displacement of the remaining workpiece together with the workpiece part along a workpiece support, wherein the minimum width of the microjoint is determined in dependence on the at least one machining parameter in a form of an acceleration of the workpiece part during the displacement along at least one displacement direction.
8 . The method according to claim 7 , wherein the minimum width of the microjoint at which, during the displacement of the workpiece part together with the remaining workpiece, a flexural stress at the microjoint that does not exceed a maximum flexural stress is determined.
9 . The method according to claim 8 , wherein the maximum flexural stress at the microjoint is not greater than a yield strength of a material of the workpiece.
10 . The method according to claim 8 , wherein the minimum width of the microjoint is made up of the minimum width of the microjoint at which the maximum flexural stress is not exceeded and a safety factor.
11 . The method according to claim 10 , wherein the safety factor dependent on the minimum width of the microjoint at which the maximum flexural stress is not exceeded.
12 . A method for determining an attachment position of a microjoint by which a workpiece part remains connected to a remaining workpiece when machining a workpiece, which comprises the step of: determining a minimum width of the microjoint in a case of multiple different attachment positions along an outer contour of the workpiece part, wherein the minimum width is determined by the method according to claim 1 ; and selecting an attachment position along the outer contour for the machining of the workpiece for which a smallest minimum width of the microjoint has been determined.
13 . A method for machining a workpiece, which comprises the steps of: machining the workpiece while thereby forming at least one microjoint by which a workpiece part remains connected to a remaining workpiece, the at least one microjoint is formed at an attachment position along an outer contour of the workpiece part, the attachment position is selected along the outer contour for the machining of the workpiece for which a minimum width of the microjoint has been determined by the method according to claim 1 .
14 . A non-transitory computer program readable storage medium having computer executable instructions for carrying out all of the steps of the method according to claim 1 when the computer program runs on a data processing system.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation, under 35 U.S.C. § 120, of copending International Patent Application PCT/EP2021/061767, filed May 5, 2021, which designated the United States; this application also claims the priority, under 35 U.S.C. § 119, of German Patent Application DE 10 2020 205 680.3, filed May 6, 2020; the prior applications are herewith incorporated by reference in their entirety. FIELD AND BACKGROUND OF THE INVENTION The present invention relates to a method for determining a minimum width of a microjoint by which, when machining a workpiece, in particular a sheet-like workpiece, a workpiece part remains connected to a remaining workpiece of the workpiece. The invention also relates to a method for determining an attachment position of such a microjoint and also to a method for machining a workpiece, in particular a sheet-like workpiece, the method including: machining the workpiece while thereby forming at least one microjoint by which a workpiece part remains connected to a remaining workpiece. Microjoints are retaining bars between workpiece parts and a remaining workpiece, sometimes also referred to below as the residual cut-out sheet. Microjoints are mainly set for example during the laser cutting or punching of workpieces, in particular sheet-like workpieces, in order to hold otherwise detached parts of the workpiece in the residual cut-out sheet in such a way that they do not become tilted, and for example in this way to prevent collisions between the machining head during the machining of the workpiece and the workpiece part. Microjoints also make it easier for the parts of the workpiece to be automatically unloaded together with the residual cut-out sheet. The retaining bars or the microjoints are created by not cutting or punching the outer contour of the workpiece part right up to the end. Small retaining bars with a width of several tenths of a millimeter to a millimeter (so-called microjoints) are set by the programmer of the control program for the machine tool, for example a laser cutting system, either manually or by a control mechanism contained in the programming software. The size and the attachment position of the microjoint along the outer contour of the workpiece part must in this case usually be established by the programmer. It is mostly the case here that all of the microjoints that are set on a sheet-like workpiece are of the same width, irrespective of the conditions of the process, the properties of the workpiece part (weight, geometry), the material, etc. This has the consequence that microjoints on small workpiece parts tend to be too wide and the small parts of the workpiece can consequently only be removed with difficulty from the residual cut-out sheet. In addition, the subsequent work necessary for removing the microjoints that are too wide is onerous. It is generally the case that: The wider the microjoint, the greater the subsequent work required to remove attachment marks at the cut or punched edge. On large workpiece parts, on the other hand, the microjoint set by the programmer may not be wide enough, and so the workpiece part is not securely held in the residual cut-off sheet and this may have the consequence of a collision between the tilted workpiece part and the machining head. It is known from Japanese patent application JPH 0663659A to calculate the optimum width of a microjoint in dependence on the thickness of the workpiece, the length and physical properties of the material of the workpiece and also the surface area of the detached workpiece part. It is known from Japanese patent application JPH0439706A to read out an optimum microjoint width, dependent on the material and thickness of the workpiece, in an automated manner from a parameter database. SUMMARY OF THE INVENTION The invention is based on the object of providing a method for determining a minimum width of a microjoint, an attachment position of a microjoint and also a method for machining a workpiece with which the microjoint has an optimum width. This object is achieved according to a first aspect by a method of the type mentioned at the beginning in which the minimum width of the microjoint is established in dependence on at least one machining parameter which influences a relative position of the workpiece part in relation to the remaining workpiece during the machining of the workpiece. The inventors have realized that the determination of an optimized microjoint width requires that account is taken of not only parameters of the workpiece part or information concerning the workpiece part—as in JPH0663659A—but also machining parameters of a process or of a machining method in which the workpiece part is formed (typically cut or punched) or manipulated (for example displaced). The at least one machining parameter typically influences a relative position of the workpiece part in relation to the remaining workpiece during the machining of the workp