GB2143762A

GB2143762A - Articulated-arm robot for cutting

Info

Publication number: GB2143762A
Application number: GB08416582A
Authority: GB
Inventors: Florian Bauer; Manfred Czychy; Gerhard Hubsch; Wolfgang Lehmann
Original assignee: Messer Griesheim GmbH
Current assignee: Messer Griesheim GmbH
Priority date: 1983-07-11
Filing date: 1984-06-29
Publication date: 1985-02-20
Also published as: IT1196174B; DE3324948C2; IT8421674A0; GB2143762B; DE3324948A1; GB8416582D0; FR2548941A1; IT8421674A1; JPS6037266A

Abstract

The invention relates to an articulated-arm robot 10 for cutting, especially for oxyacetylene or plasma-arc cutting of metals, with an articulated arm 16 and a pivot joint 18 fastened to the free end of the articulated arm. To simplify the programming of three-dimensional parts and to compensate automatically for the changes in height of workpieces as the result of warping during cutting, a cutting torch 32 with an associated torch-height control is fastened to the pivot joint. <IMAGE>

Description

SPECIFICATION Articulated-arm robot for cutting The invention relates to an articulated-arm robot for cutting, according to the pre-characterising clause of Claim 1.

Articulated-arm robots make it possible to automate the production process and are a precondition for a constant increase in productivity.

Articulated-arm robots for cutting, especially for oxyacetylene cutting or plasma-arc cutting of metals, to which a programming unit is assigned in order to guide the cutting torch automatically along a predetermined path, have been used more and more frequently in recent years in the sheet-metal fabrication industry (Messer Griesheim Prospectus No. 32.3023, volume 1981, Eurobot 3, and Messer Griesheim Prospectus No. 32.3020, volume 83, Eurobot 10-W).

The path curve of the robot movement of the known articulated-arm robot, that is to say the cutting course, is programmed by means of point selection of the individual path points by hand. As a result of key pressure on the programming unit, the individual axes are moved into the respective positions and are stored in the robot control when the programming key is pressed. In oxyacetylene or plasma-arc cutting, the cutting torch must, by means of the path control, follow with high repeating accuracy a path which is curved arbitrarily in space.

If the curved path does not follow a uniform course in space, or if changes in the workpiece height occur because heat is introduced into the workpiece, on the one hand it is very expensive or no longer possible to program the irregularly curved path, since a very large number of path points have to be selected point by point or at most 2,000 path points can be stored. On the other hand, changes in workpiece height as a result of warping during cutting are not taken into account by the program control. This results in defective oxyacetylene or plasma-arc cuts.

The object on which the invention is based is to simplify the programming of three-dimensional cutting paths by means of the programming unit described above.

A further object is to compensate automatically for the changes in height of workpieces as a result of warping during cutting, the cutting torch being guided at the "correct height", that is to say at a constant distance above the path to be cut. The "correct height" differs here at least from time to time from the "programmed height".

In a robot of the generic type, these objects are achieved by means of the characterising features of Claim 1.

The advantages obtained by means of the invention are to be seen essentially in the fact that in a simple way, as a result of the arrangement of the cutting torch/torch-height control on the pivot joint of the articulated-arm robot, on the one hand the number of path points to be controlled can be reduced substantially, since differences in height in the path no longer need to be selected individually, and on the other hand variations in height as a result of warping are compensated for. As a result of this device according to the invention, it is advantageously possible to cut three-dimensional workpieces by means of paths stored two-dimensionally, the height being kept constant automatically.

In order, in particular, to put these advantages into practice without an expensive programming control unit and software, a motor-driven slide is arranged between the pivot joint of the articulated-arm robot and the cutting torch.

A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows a perspective representation of the articulated-arm robot according to the invention; Figure 2 shows an enlarged representation of the components, the pivot joint, cutting torch and torchheight control.

In Figure 1, an articulated-arm robot with five degrees offreedom is designated as a whole by 10.

The five degrees of freedom of the articulated-arm robot 10 are produced by the rotary unit 12, the arms 14, 16 and the pivot joint 18.

The controlled axes 12, 14 and 16 are driven via the servo-motors 20,22,24. The pivot joint 18 is driven via a motor not shown in any more detail and can be swivelled through 180 and rotated through 300 .

According to a preferred embodiment of the invention, there is on the pivot joint 18 a slide 21 which consists of a guide part 28 fastened to the pivot joint 18 and of a slide part 30 movable linearly on the guide part 28.

Mounted in the guide part 28 is a recirculating ball-screw not shown in any more detail, which serves for guiding the slide part 30. The recirculating ball-screw is driven via a motor located in the guide part 28.

As shown in Figure 2, the cutting torch 32 is fastened in a pivotable fork piece 34 on the slide part 30.

Located between the side parts 36,38 of the fork piece 34 is a bearing block not shown in any more detail, which is connected via a shaft to the side parts 36,38 of the fork piece 34. The shaft is mounted in aligned bores of the side parts 36,38 and a bore of the bearing block. The underside of the bearing block is designed as a fastening plate which is screwed to the slide part 30. The front side of the fork piece 34 is designed as a torch support 40. Fastened in the bore 42 of the torch support 40 is an oxyacetylene cutting torch 32 which is supplied via the gas and oxygen delivery lines 44,46.

Fastened to the side of the fork piece 34 is a control housing 48 in which the resonant and control circuit of the capacitive torch-height control 55 is located.

The resonant and control circuit is supplied with electricity via the lines 50. A capacitive tracer unit 54 is mounted on the side of the control housing 48 facing the torch nozzle 52. The capacitive tracer unit 54 consists of a tracer 56 which is arranged in the immediate vicinity of the torch nozzle 52 and which is connected to the control housing 48 via a retaining rod 58. Connected on the side of the control housing 48 facing away from the torch support 40 is an air supply 64 which serves for cooling the electronic/ electrical components of the capacitive resonant and control circuits. Fastened to the slide part 30, on the same side of the slide 26, is a feed 66 which supplies air to the gap between the tracer 56 and the workpiece via a copper tube 68.Because the gap is supplied with air, the pressure of which can be adjusted as desired at the valve 70, on the one hand the tracer 56 is cooled and on the other hand a constant atmosphere is maintained between the capacitive tracer unit 54 and the workpiece, so that combustion gases and smoke, etc., do not influence the capacitance between the tracer 56 and the workpiece.

When the capacitive torch-height control 55 detects a deviation in the height of the workpiece from the programmed height and/or the height set at the torch-height control 55, the height signal controls the motor of the slide 26, and the slide 26, the stroke of which preferably amounts to 50 mm, moves the cutting torch 32 at a corresponding constant distance set at the torch-height control 55.

So that proper programming is guaranteed, the slide 26 is controlled so that it is located in the middle position during programming. In this way, readjustment with a range of +20 mm to -20 mm is guaranteed during cutting. After a cut has been completed, the slide 26 automatically moves into the upper position. For a new workpiece, the torch is advanced towards the workpiece from this upper position and the height is set via the sensing tracer 56.

It is also possible, of course, not to control the motor-driven slide directly by means of the torchheight control 55, but to feed the height signals to the robot control which then controls the motordriven slide 26.

Furthermore, it is also possible to enter the changes in height, detected by the torch-height control 55, directly into the robot control which moves the entire articulated-arm tobot and thus sets the cutting torch to the desired height. In this case, the motor-driven slide 26 on the pivot joint 18 can be omitted.

Claims

1. Articulated-arm robot for cutting, especially for oxyacetylene or plasma-arc cutting of metals, with an articulated arm and a pivot joint fastened to the free end of the articulated arm, characterised in that a cutting torch with an associated torch-height control is fastened to the pivot joint.

2. Articulated-arm robot according to Claim 1, characterised in that a motor-driven slide is fastened between the pivot joint and the cutting torch with an associated torch-height control.

3. Articulated-arm robot according to Claim 1 or 2, characterised in that the torch-height control is connected directly to a robot control.

4. Articulated-arm robot according to Claim 2, characterised in that the output signals from the torch-height control can be fed to the motor of the slide.

5. Articulated-arm robot according to one of Claims 1 to 4, characterised in that the torch-height control is designed as a capacitive height control.

6. Articulated-arm robot according to one of Claims 1 to 5, characterised in that an air supply for cooling the control housing and the tracer and for maintaining a constant atmosphere between the tracer and the workpiece is associated with the torch-height control.

7. Articulated-arm robot for cutting, substantially as described with reference to the drawings.