GB2040074A

GB2040074A - Laser beam machining

Info

Publication number: GB2040074A
Application number: GB7944443A
Authority: GB
Original assignee: Kombinat Feinmechanische Werke Halle Veb
Current assignee: Kombinat Feinmechanische Werke Halle Veb
Priority date: 1978-12-27
Filing date: 1979-12-28
Publication date: 1980-08-20
Also published as: DD140117B1; DD140117A1; DE2947071A1; GB2040074B

Abstract

Apparatus machines material by laser beams eg for cutting welding or engraving. It includes a numerical control system for coordinates of a high- precision guide system 38 and a laser beam source (1) having a telescopic system (2) outside the material (13) to be machined so that the highly reflective part of the laser radiation is guided from the source (1) via deflecting mirrors to a laser cutting head under units (12, 21 ). A first measuring means (11), a first setting element (17), an automatically adjustable adjusting mirror (22) and a second setting element (18) are disposed in the zone of the source (1) and are connected to a second measuring means (12), which contains a measuring orifice (21) locked on the high- precision guide system (38) by a voltage U1 (9). Also provided are a measured value voltage device (3), a first amplifier (4), a first controller (6) of a limit value adjustment, and a second amplifier (5) connected to controller (6) by an external guide voltage. <IMAGE>

Description

SPECIFICATION Apparatus for the high-precision machining of materials using laser beams This invention relates to apparatus for the highprecision machining of various materials using laser beams in processes such as cutting, welding and engraving, in given numerically controlled paths and contours.

The use of laser beams in the machining of various types of material is known, the laser beams usually being directed at the place where machining takes place, relative movement occurring between the laser beam and the plane of the workpiece to be machined. The disadvantage of this known technical method is that, in high precision machining in the range of hundredths of a millimetre the laser and the laser optical system must be moved jointly over the workpiece, and due to the mass inertia of these units, only relatively low machining speeds can be achieved if a high degree of accuracy is required.

Lasers of high continuous output power are also very heavy, and this makes the high-precision machining of materials difficult. It has been suggested that this disadvantage can be overcome by moving only a lightweight laser optical system at high speed over the plane of the workpiece, an adjustable pair of reflecting mirrors being provided whose radii of curvature are harmonisedwith one another and are disposed on two deflecting mirrors disposed on the guide machine between the output window of the laser and the laser beam. The mirror geometry is influenced by altering the distance between the pair of reflecting mirrors. With the laser cutting system, it is impossible to perform highprecision machining with a high degree of reproducibility, since during machining, the laser beam directions are continuously disturbed due to the movements.

In another proposal, adjusting devices for laser mirrors are used which are adjusted externally using micrometer gauges, 3 mm of the adjusting points on conical micrometer spindles, each offset by 120", enabling the mirrors to be adjusted on a pre-defined axis. The disadvantage of this arrangement is that, quite apart from its expensive construction, the axial micrometer gauge of the mirrors must be constantly readjusted, particularly during the high-precision machining of materials.

All these prior art systems have the disadvantage that a hitherto uncontrollable reflection radiation from the workpiece on to the measuring means falsifies the measuring results, so that it is impossible to make any accurate comparison between the required and actual values.

It is an object of the invention to provide an arrangement for the high-precision machining of materials by means of laser beams whose operation results in increased productivity and a reproducibly high machining quality. The problem to be solved by the invention therefore is to design an arrangement for the numerically controlled high-precision machining of materials by means of laser beams using a movable optical system for machining which will enable a high machining speed to be achieved over an accuracy range of hundredths of a millimetre.

In a preferred construction of the invention, a cross-slide rest of a high precision guide system is movably disposed above a surface for machining, the precision guide system containing an X- and a Y-drive connected to a numerical control system, a measuring means II having a measuring orifice and a laser cutting head which is disposed therebelow at a distance of about 2 to 3 times the focal length from the laser cutting optical system. The measuring means II is connected by a voltage U1 to a measured value voltage device. Disposed outside the highprecision guide system is a laser beam source with its telescopic system, a measuring means I, consisting of a deflection measuring member and a measuring cone, a first control or setting element I, an automatically adjustable adjusting mirror and a second final control or setting element 11.Connected to the measuring means I by a voltage U2 is the measured value voltage device, which is also connected to a first amplifier I and a first controller I of a limit value adjustment and a second setting element II. At the first controller I, a second amplifier II is connected by an external guide voltage to the second controller II, which is also connected to the first amplifier I and to the first final control element I.

The plane reflection surface of the deflection measuring member is rendered highly reflective. An arcuate, optically imaging surface is disposed opposite the plane reflection surface at an angle of 5 to 17% During the operation of the installation, the laser beam source, which corresponds with the telescopic system, is guided precisely in the direction of the first coordinate of the high-precision guide system.

One of the mirrors of the telescopic system is also additionally constructed as a deflection measuring member. The highly reflective part of the laser radiation of the deflection measuring member reflects the laser beam, via the deflecting mirror, through the measuring orifice of the second measuring means II into the laser cutting head. The transmitting proportion of the laser beam passes in the form of a measuring signal into the measuring cone, where it is taken in the form of voltage U1 and voltage U2 to the measured value voltage device.

The measuring signal measures the laser beam power during the machining of the material and is also used for stabilizing the laser beam source. One mirror of the telescopic system is attached to an adjustable mounting which is disposed, in two coordinates adjustable perpendicularly to one another, to be adjustably pivoted via the controllable first and second setting elements I and II independently of one another.Disturbances in the transmission of the highly reflective parts of the laser radiation, the movement of the high-precision guide system, fluctuations in power, changes in the direction of the beam and mains voltage fluctuations are compensated for due to the fact that, at the first measuring means I of the deflection measuring member and at the second measuring means II, decentring radiation shadows at the measuring orifice are determined as differential values and used as controlled variables for dynamic readjustment of the automatic adjusting mirror.

A preferred apparatus of the invention will now be described, by way of example only, with reference to the drawings, wherein: Figure 1 shows diagrammatically, an arrangement of the invention; Figure 2 is a plan view of a setting element shown in Figure 1; Figure 3 is a side elevation showing the coordinate final control element shown in Figure 1; Figure 4 is a side elevation of the control element shown on its mirror side; Figure 5 is a section, corresponding to Figure 2, through the controllable final control element; and Figure 6 is a section through a deflection measuring member.

Referring to the drawings, there is shown in Figure 1 a high-precision guide system 38 in the form of a known cross-slide rest disposed to travel over a surface 13 for machining. The precision guide system 38 includes an X-drive 15 and a Y-drive 16 connected to a numerical control system 14, second measuring means it, 12 having a measuring orifice 21 and a laser cutting head which is disposed therebelow at a distance of about 2 to 3 times the focal length from the laser cutting optical system.

The second measuring means 1112 is connected by a voltage U1 9 to a measured value voltage device 3.

Disposed outside the high-precision guide system 38 is a laser beam source 1 and associated telescopic system 2, a first measuring means 1, 11 having a deflection measuring member 36 (see Figure 6) and a measuring cone 28, a first setting element 1, 17, an automatically adjustable adjusting mirror 22 and a second setting element 11 18. Connected to the first measuring means 111 by a voltage U2 10, is the measured value voltage device 3, which again is connected via a first amplifier 14 and a first controller 16, with a limit value adjustment 19 and the second setting element 11 18.At the first controller 16, a second amplifier 115 is connected, by an external guide voltage 8, to the second controller it 7, which is also connected to the first amplifier 14 and to the first setting element 1 17. The deflection measuring member 36 is, pivotably attached to a mounting 35 cooled by cooler 33 with its plane reflection surface 41 rendered highly reflective. An arcuate, optically imaging surface 40 is disposed opposite the plane reflection surface 41 at an angle 42 of between 5 and 17 .

During the operation of the illustrated installation, the laser beam source 1, which corresponds with the telescopic system 2, is guided precisely in the direction of the first coordinate of the high-precision guide system 38. One of the mirrors of the telescopic system 2 is also additionally constructed as a deflection measuring member 36. The highly reflective part of the laser radiation 25 of the deflection measuring member 36 reflects the laser beam 27, via the deflecting mirror 20 (Figure 11, through the measuring orifice 21 of the second measuring means 1112 into the laser cutting head. The transmitting proportion of the laser beam 26 passes in the form of a measuring signal 29 into the measuring cone 28, (Figure 6) where it is taken in the form of voltage U1 9 and voltage U2 10 in the measured value voltage device 3.The measuring signal 29 measures the laser beam power during the machining of the material and is also used for stabilizing the laser radiation source 1. One mirror of the telescopic system 2 is attached to an adjustment retaining means 39 (Figure 2) which is disposed, in two coordinates 30 adjustable perpendicularly to one another, to be adjustably pivoted by means of the controllable setting element 117 and setting element 1118 independently of one another by means of a setting screw 31, control signal input 37 and a controllable third setting element 24.Disturbances in the transmission of the highly reflective parts of the laser radiation 25, the movement of the highprecision guide system 38, fluctuations in power, changes in the direction of the beam and mains voltage fluctuations are compensated by the feature that, at the first measuring means 111 of the deflection measuring member 36 and at the second measuring means 1112, decentering radiation shadows at the measuring orifice 21 are determined as differential values and are used as controlled vari ablesforthe dynamic readjustment of the automatic adjusting mirror 22. For spectral analysis, the deflection measuring member 36 is turned through 1800.

As a result, the measuring cone 28 receives unfalsified values of the reflection component of the highly reflecting part of the laser radiation 25 of the material to be investigated, so that spectral analyses can also be performed on materials having large surfaces. Due to a ready, rapid and automatically adjusted control of the direction of the laser beams 27, the illustrated arrangement provides increased productivity and a degree of accuracy in the range of hundredths of a millimetre in the high-precision machining of materials.

Claims

1. Apparatus forthe high-precision machining of material by means of laser beams, the apparatus comprising a numerical control system for the coordinates of a high-precision guide system, a laser beam source having a telescopic system disposed outside the surface to be machined, the arrangement being such that the highly reflective part of the laser radiation is guided from the laser radiation source via deflecting mirrors to a laser cutting head, a first measuring means, a first setting element, an automatically adjustable adjusting mirror and a second setting element being disposed in the zone of the laser radiation source and being connected to a second measuring means provided with a measuring orifice which is locked on the high-precision guide system by a voltage U1, a measured value voltage device, a first amplifier and a first controller of a limit value adjustment, a second amplifier being connected atthefirstcontrollervia an external guide voltage to a second controller which is also connected to the first amplifier and the first setting element; an arcuate, optically imaging surface disposed opposite a plane reflection surface of a deflection measuring member at an angle of be tween Sand 17% the deflection measuring member being adjustably attached to both the first measuring means and the second measuring means; the automatically adjustable adjusting mirror being mounted on adjustment retaining means movable in two coordinates adjustable perpendicularly to one another, said mirror being adjustably pivotable by means of said first and second setting elements independently of one another by a control signal input and a controllable third setting element.

2. Apparatus as claimed in claim 1, wherein the deflecting measuring member is disposed on a mounting which is pivotable through 180%

3. Apparatus substantially as herein described with reference to the accompanying drawings.