WO1997038822A1

WO1997038822A1 - System for deburring or grinding a workpiece using a robot or manipulator, method of using said system, and use of said system and method

Info

Publication number: WO1997038822A1
Application number: PCT/DK1997/000158
Authority: WO
Inventors: Søren E. KNUDSEN; Michael Sander Jensen
Original assignee: Georg Fischer Disa A/S
Priority date: 1996-04-12
Filing date: 1997-04-11
Publication date: 1997-10-23
Also published as: DK42596A; DK171660B1; AU2380797A

Abstract

In a system for deburring a workpiece (8), such as a casting, using a robot (3) provided with gripping means (4) to grip the workpiece to be deburred, said system comprising at least one stationary, rotating deburring means (9, 9a, 11, 11a), such as a grinding wheel (9a, 11a), said deburring means being trued-up from time to time, and in which the robot is controlled to move the contour or contours of the workpiece to be deburred past the deburring means with a correct pre-loading and/or spacing for carrying out the deburring. The main novel feature is that the robot, in addition to the normal tools, is provided with at least one contact-less sensor (52, 53) for sensing a surface position on the deburring means (9, 9a, 11, 11a), possibly also a trueing-up means (51). With this arrangement, the robot can carry out calibrating and trueing-up operations on tools during or between the normal processing steps.

Description

SYSTEM FOR DEBURRING OR GRINDING A WORKPIECE USING A ROBOT OR MANIPULATOR. METHOD OF USING SAID SYSTEM. AND USE OF SAID SYSTEM AND METHOD

TECHNICAL FIELD

The present invention relates to a system for deburring or grinding a workpiece using a robot or manipulator, said system being of the kind set forth in the pream- ble of claim 1 , as well as a method of using said system of the kind set forth in claim 4, and use of the system and the method

BACKGROUND ART

Within the prior art, deburring of cast objects has generally been carried out by either moving the contour of the casting past and in contact with a grinding wheel or other deburring tool, or to move the deburring tool past and in contact with the contour of the object to be deburred In general, small objects have been moved past a grinding wheel, whereas deburring of greater objects was carried out by moving the deburring tool past the contour of the object

The prior art comprises attempts at automating these processes, e g using robots When using robots, these must be controlled in some way in order to provide the desired deburring.

In the most simple embodiments, in which the tool is moved about the object to be deburred, the tool is merely moved through a predetermined path, or the object is moved according to a predetermined movement profile without taking the size of the burrs or the condition of the tool into consideration This has given cause to problems, because the tool or the object to be deburred can be damaged when large burrs are encountered, or the degree of deburring is insufficient due to the tool being worn. For this reason, it has been necessary to take these problems into account when devising robot-automated deburring, lea- ding to complicated control and positioning systems.

EP-B1-410,836 discloses an example of measures carried out on a deburring ro¬ bot. This publication discloses that the pressure on a deburring tool being moved about the contour on the object by the robot arm can be controlled as a function of the rotational speed of the tool, and shock-absorbing means may be placed be¬ tween the tool and the robot arm. Thus, with this tool it has been necessary to use an advanced form of control of the pressure exerted by the tool, and this again makes it necessary to sense the position of the tool, as otherwise this position is not known.

US-A-4, 894 ,597 describes equipment of the kind, in which a robot arm moves a grinding tool about the contour of a workpiece. For controlling the movement of the tool the robot arm is provided with a contact-less sensor system adapted to sense the contour of the object to be deburred, and sensed values from this sensor sys- tem is used in connection with a pressure-sensor system in the robot arm to control the grinding tool during the deburring. As the sensor system is unable to sense the momentary condition of the abrasive disc in the grinding tool, a tool for measuring the diameter of the abrasive disc is also provided. This measuring tool is situated separately relative to the workpiece and the robot arm and is used to calibrate the sensor system on the robot arm in such a manner, that the sensor is moved corre¬ sponding to changes in the diameter of the abrasive disc or grinding wheel.

Thus, when using such equipment it is necessary to have optic sensing during the deburring, this being complicated due to the grinding dust being generated, and to move the grinding tool to a dedicated diameter-measuring tool placed separately from the normal working area in order to adjust the optical sensing in dependence on the condition of the abrasive disc, and to provide a good deburring. A similar equipment for deburring the ends of pipes is known from EP-A1-362.413. In this equipment, the optical sensor system is replaced by a "copying claw" on the robot arm, following the surface of the pipe in burr-free areas. The copying claw is used for moving a grinding stone constituting the deburring tool on the robot arm.

In order to compensate for wear of the grinding stone, the arm is moved to a dedi¬ cated calibrating station, in which the copying claw is made to abut against a base block, after which the grinding stone is moved on the robot arm into abutment against a sensor element, so that the grinding-stone surface takes up a given posi¬ tion relative to the copying claw on the robot arm.

In these known systems, the sensor system and the working face of the deburring tool are adjusted relative to each other in or at a separately positioned dedicated calibrating station. In order to carry out this adjustment, it is necessary with this prior-art equipment to have complicated, "tailor-made" equipment to make it possi¬ ble to move the grinding stone relative to the sensor, or vice versa, on the robot arm. After this, the deburring tool is moved to the workpiece, at which the sensor (the optical sensor system or the copying claw) is used to control the movement of the deburring tool relative to the workpiece.

Correspondingly, in prior-art systems of the kind, in which a robot arm moves the workpiece past a stationary deburring tool, it is known to construct the deburring tool in such a manner, that it is possible by means of measuring equipment and other equipment to adjust the working faces of the deburring tool in order to com¬ pensate for wear on abrasive discs and grinding stones.

Thus, the prior-art technologies described above suffer from the disadvantage that they require equipment which is complicated to construct and in many cases must be "tailor-made", making them costly. Further, these prior-art technologies necessi¬ tate the use of additional movable equipment increasing the risk of operating er- rors, as well as complicated dedicated calibrating stations situated externally of the normal working area.

DISCLOSURE OF THE INVENTION

It is the object of the present invention to provide a simple equipment of the kind, in which the workpiece is moved past a tool with a substantially improved accuracy, especially accuracy of reproduction, without necessitating the use of complicated equipment or extensive modifications to e.g. a standard robot, or the use of separa¬ te calibrating stations.

This object is achieved in a system of the kind set forth in the preamble of claim 1 using the means set forth in the characterizing clause, as well as with a method of the kind set forth in claim 4, further with a use according to claim 9.

By constructing the system in the manner set forth in claim 1 , it is possible to avoid the use of pressure-sensor-based positioning with the accompanying costs and inaccuracies, including continuous pressure along long paths of movement, at the same time making it possible to carry out deburring with a knowledge of the sur¬ face postion of the tool, it being possible using the simple means set forth in the characterizing clause of claim 1 to sense this surface from time to time.

With the embodiment set forth in claim 2, it is also possible to carry out mainte- nance work on the tool using simple means, so that the condition of the tool does not affect the deburring.

With the embodiment set forth in claim 3 it is possible to achieve that wear on the tool carrying out the trueing-up of the grinding stone will not affect the quality of the trueing-up, and finally also the deburring proper. Likewise, when proceeding according to the method of claim 4, it is possible to a- chieve a substantial improvement of the deburring process using a conventionally constructed deburring machine without extensive modification of standard equip¬ ment. In this manner, the deburring tool will also be monitored, thus also providing information about this tool.

By also proceeding in the manner set forth in claim 5, it is possible to achieve an additional improvement in the quality of the deburring, because the tool carrying out the deburring is maintained in good condition.

With the method according to claim 6, it is possible using simple equipment to a- chieve the same accuracy of deburring as will otherwise only be possible using complicated equipment.

By additionally carrying out the method in the manner set forth in claim 7, it is pos¬ sible to modify the method on the basis of previous experience, so that optimum quality and quantity are achieved.

By also omitting to initialize the robot itself, such as indicated in claim 8, it is possi- ble to achieve a high degree of accuracy in the deburring itself without the need for modifying a standard program, or by the accuracy in other working processes being disturbed by the method according to the previous claims.

By also using the system and the method as set forth in claim 9, it is possible to utilize the fact that a standard robot in a relatively simple manner can lift heavy objects and position the latter in space, without the size of burrs during the debur¬ ring operation being of substantial significance for the forces necessary for this. In contrast, placing of tools on a manipulator or robot will normally require special adaptation of the tools to the robot and continuous supply of energy to the tool, and the latter will be subject to large differences in the force exerted on it as a function of the burr size, all this being of importance to the quality of the deburring. BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed part of the present description, the invention will be ex- plained in more detail with reference to the exemplary embodiment of a deburring system according to the invention shown in the drawing, in which

Figure 1 shows an integrated robot cell, in plan view, Figure 2 shows a standard robot with six degrees of freedom, Figures 3 and 4 show the distal parts of a robot, in elevation and plan view, re¬ spectively, and Figure 5 is a process diagram of a calibrating routine according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Figure 1 shows an integrated robot cell 1 of the kind, in which a common base- -plane element 15, 16 supports a robot 3, possibly also stationary tools 9, 11 or other means, relative to which a workpiece is to be positioned accurately.

The robot cell shown in Figure 1 is built on a baseframe 16, shown partly diagram¬ matically, upon which a baseplate 15 is placed, so that the assembly of these two parts constitutes the base-plane element. Control equipment 2 is situated on the rearmost end of the base-plane element, while the robot 3 is placed on the rear part of the element. The robot's base 30, at the same time constituting the proximal datum, is secured to the baseframe 16 and the baseplate 15 by means of bolts 17, this being the location in which the greatest forces occur. Further forward in the robot cell, stationary tools 9, 11 are placed on the baseplate 15, possibly also on the baseframe 16. The forward end of the cell comprises a deposition area 5 for incoming workpieces as well as a deposition area 12 for outgoing workpieces 8; the deposition area 12 can advantageously be in the form of a conveyor 12 as shown, or else as a slide or chute. In this basic position, the robot 3 can take a workpiece 8 from the deposition area 5 by means of its gripper or working head 4. Then, the robot 3 transfers the work- piece 8 across to the first stationary tool 9, at which the robot 3 moves the workpie- ce 8 in the manner necessary to carry out the first process step. Next, the robot 3 moves the workpiece 8 to the next tool 11 , at which the robot 3 moves the work- piece 8 in the manner necessary to carry out the process step concerned. After this, the robot 3 moves the workpiece 8 to the deposition area 12, on which it de¬ posits the workpiece 8. At this stage, the robot 3 is ready to take a new workpiece 8 from the entrance area 5 and carry out a new process cycle.

In the present description, the robot cell 1 is described as having one or two statio¬ nary tools 9, 11, but it may, of course, comprise a greater number of tools.

During the process cycles, the robot 3 moves the workpiece 8 into position at a processing tool 9, 11 and carries out the requisite movements of the workpiece 8 for executing the process step concerned; this may e.g. be constituted by rotation and translation of the workpiece 8 relative to a desired final contour, said move¬ ments being determined relative to the processing face of a cutting wheel 9a, an abrasive wheel 11a etc. As these processing faces change due to wear or dama¬ ge, it is necessary now and then to square them up and/or to modify the process movements relative to them.

The robot itself may be a standard robot or manipulator with five or six degrees of freedom, e.g. as shown in Figure 2 and comprising a base 30 constituting the prox¬ imal datum, a first robot arm 31 rotatably connected to the base 30 and capable of turning relative to it in directions A1 , a second robot arm 32 pivotable about a pivot pin 31a in directions A2, a third robot arm 33 pivotable about a pivot pin 32a in di¬ rections A3, a fourth robot arm 34 rotatable in directions A4 relative to the third robot arm 33, a fifth robot arm 35 pivotable in directions A5 about a pivot pin 34a secured to the distal part 37 of the fourth robot arm 34, and finally a distal robot part 36 rotatable in directions A6 relative to the fifth robot arm 35. The distal robot part 36 is adapted to have secured to it the working head 4, that may be a gripper, a tool or the like. The bearing, about which the distal robot part 36 can rotate relati¬ ve to the fifth robot arm 35 in the directions A6, is constituted by a rotational bear¬ ing allowing rotation through e.g. 720°. The joint, about which the fifth robot arm 35 can pivot relative to the distal part 37 in the directions A5, is constituted by a pivot joint allowing movement through less than one turn, e.g. 240° or ± 120°. Together with its forwardmost or distal part 37, the fourth robot arm 34 constitutes an elonga¬ te, rigid robot element, onto which auxiliary equipment, such as e.g. a welding transformer, can be secured. Standard robots and manipulators of this kind with five or six degrees of freedom are manufactured in great numbers, e.g. for the automobile industry, for which reason they present a highly advantageous pri¬ ce/quality ratio as compared to the tailor-made robots or manipulators with fewer degrees of freedom.

Thus, when a standard robot is used in the integrated deburring cell, there will typi¬ cally normally be provided a greater number of degrees of freedom and a greater programming potential than what is immediately necessary for a deburring robot or manipulator.

With the present invention, these "surplus" degrees of freedom are utilized to carry out checking, calibrating and trueing-up of a rotating deburring tool, e.g. an abrasi¬ ve wheel, that is worn down by the deburring processes, possibly changing its pro¬ cessing face. Thus, it will be necessary from time to time to carry out a trueing-up and/or calibrating of the surface of the abrasive wheel in order to know the tatter's condition and/or position.

According to a first embodiment of the invention, at least one sensor 52, 53 is/are placed externally on one of the distal articulations of the robot 3 in the manner shown in Figures 3 and 4, the signals from the sensor or sensors being transmitted to the control equipment 2, possibly via a measurement processing circuit 54. As the position of the individual robot articulations are known or can be computed at any time, the instantaneous position of the sensor 52 is also known or can be computed, because its position is fixed relative to a robot part and the position of the latter is known or can be computed on the basis of the positions of the articula¬ tions situated proximally relative to the robot part concerned. Thus, in a calibrating step, the robot can direct the sensor 52, 53 towards the abrasive wheel or other object of calibration, and advance the sensor 52, 53 along a given path towards the abrasive wheel to a point, at which the sensor senses a distance signal or pro¬ duces a detection signal, causing the robot to stop. If the processing face of the abrasive wheel has changed, this is detected as a difference in the position of the robot or in the distance between the robot and the processing face. This detection can be used to compute a difference or offset between a reference position and the measured position, and this offset can be transformed into an offset to be ad¬ ded to the movements of the robot, when the latter controls processing with the tool concerned without the necessicity of initializing the position of the robot, which would cause changes to the tatter's position in other processing steps. Further, the signal from the sensor 52 may be used as a basis to decide whether the abrasive wheel is to be trued-up and/or replaced.

Further, when a trueing-up tool 51 is placed externally of one of the distal parts of the robot, it is possible on the basis of the data obtained through the calibrating to advance this trueing-up tool 51 for trueing-up the abrasive wheel by means of the robot 3 when and/or if necessary.

The trueing-up tool is also subject to wear, for which reason there is provided a further, stationary sensor 57, that can be used in a step of calibrating the trueing- -up tool to sense the distance to the processing face of the trueing-up tool or to detect said face, when the robot 3 advances the trueing-up tool 51 towards the sensor 57 to a given point in a manner corresponding to what has been described with regard to the preceding calibrating step. During this operation, it is possible to compute an offset for the trueing-up process and/or to decide whether the trueing- -up tool is to be replaced. Advantageously, a further, second sensor 53 is placed externally of one of the di¬ stal parts of the robot, if it is desired to calibrate a further tool and the first sensor 52 is positioned in a manner making it inconvenient for this calibrating.

The system for calibrating and trueing-up can advantageously be built on a base¬ plate 50 capable of being secured to one of the distal parts 34, 37 of the robot 3, whereas in this case the latter may be a standard robot normally being produced without a sensor or a trueing-up tool. On this trueing-up baseplate 50, one or a number of sensors 52, 53 and possibly a trueing-up tool 51 is/are placed. These parts 51-53 are situated in a manner suitable for the operations to be carried out by them, and the parts 51-53 and the baseplate 50 can possibly be constructed to allow for changes in the positioning, e.g. if additional stationary tools are intro¬ duced. Further, a measurement processing circuit 54 can advantageously be pla¬ ced on the baseplate 50, to which circuit 54 the signals from the sensors 52, 53 are transmitted via conduits 55, possibly also the control to the trueing-up tool 51 , so that the signals can be processed before having collected substantial noise, pos¬ sibly transformed into signals that are reduced to the most important signals and/or are easier to process for the control equipment 2. Further, this simplifies the wiring, there now being solely a single unit to be connected, which is of substantial impor- tance when the connecting conduit or conduits is/are to run past movable joints or articulations.

Further, the relative accuracy will be very high, when the calibrating is carried out in a position of the robot close to the position in which the calibrating result is to be used, because changes due to wear etc. can influence the absolute accuracy through long paths of movement but hardly along short paths of movement; this is especially important when calibrating the trueing-up tool, because calibrating of robot tools is usually carried out in a calibrating area remote from the processing area. The sensors to be used may be of any kind, but are preferably non-contact sensors adapted to measure according to optical, capacitive, magnetic or ultrasonic prin¬ ciples, so as to avoid the wear occurring with the use of a contact sensor.

Using the present invention, it is a simple matter to convert a standard robot into a specialized robot, especially when using the technology described in Applicant's co-pending DK application No. 0424/96 entitled "Energy-transfer connection for a robot" (B, S & Co. ref. 55870). This specialized robot can e.g. be well-suited to ope¬ rate in cramped spaces, and it can carry out special operations, such as calibrating and trueing-up abrasive wheels etc. This can be achieved by attaching a base¬ plate 50, 60 with the requisite auxiliary equipment in the form of energy converters 61 , units 51-54 for trueing-up, calibrating etc., attaching said baseplate 50, 60 on a standard robot arm, e.g. in a location adapted for the attachment of auxiliary e- quipment, and additionally attach a spacer-roller unit 66 on a rotary joint, and at- tach a unit with at least one guide roller 65, 65a on a robot part, as well as possibly attaching a tensioning device 68 to a robot part being held immovably relative to the robot part, to which the baseplate 50, 60 is secured.

By using the special construction of the deburring cell described in Applicant's co-pending DK-application No. 0423/96: "Integrated deburring cell for deburring castings" (B, S & Co. ref. 55869) and energy transfer, an increased speed can be achieved, this being of great importance in deburring. In this connection, it should be noted that an automatic casting machine is frequently able to produce castings eight times as fast as it has been possible to debur them up to now, the difference in speed depending on the size of the casting. Thus, it is also advantageous that it is easy to move the cell, as this makes it possibe to vary the number of cells for each casting machine or foundry hall, all according to need.

The calibrating and trueing-up system having been described, and the technical solutions it comprises, makes it possible in a simple manner to tailor a deburring cell according to a customer's desires. In this connection it is especially advantageous that it is easy to move the complete deburring cell. Thus, it is possible to make the final adjustments to the specially adapted cell in the factory, in which it can also be tested and run-in, thus obviating the need for running-in time and final adjustments when installing the cell for the user.

Figure 5 shows an example of a calibrating and trueing-up process, serving solely purposes of illustration:

R1 Start the calibrating and trueing-up program.

R2 Initialize the program and enter the starting values.

R3 Go to a first calibrating in block X1 (R3-R8) comprising sensing and calibra¬ ting of tools.

R4 If the calibrating responds that the tool is to be replaced, go to R5, otherwi- se to R7.

R5 If an early warning is to be given that the tool is soon to be replaced, go to R6, otherwise to R15 with status signal.

R6 Light up the early-warning signal "tool is soon to be replaced".

R7 If the calibrating reponds that trueing-up is to be carried out, go to R8, otherwise go to R9.

R8 Carry out trueing-up operation.

R9 If other objects are to be calibrated, go to R10, otherwise to R11.

R10 Carry out steps corresponding to X1 for one or more tools.

R11 Count the status counts. R12 If it is the last calibrating and trueing-up, go to R13, otherwise go to R15.

R13 Wait for activation while other processes are being carried out.

R14 If calibrating is to be carried out, go to X1 , otherwise go to R11.

R15 At finish, store status and light-up status signals.

R16 Go to stop, wait or return.

The above is solely to serve as an example, and for a person skilled in this field, it will be an obvious possibility to have the block R13 in the top of the program, as well as to carry out R9 and R14 in such a manner, that it is possible to choose an arbitrary procedure Xn when so desired according to a priority sequence.

This can e.g. be carried out by letting the "No"-line from R14 run to the point before R9 instead of after R9.

When the program is a sub-program under the control program for the robot pro¬ per, it is clearly possible to connect R16 between R12 and R13, and to start the program with R14 (after initialization) and to terminate it with R13. There are, however, of course many other possibilities.

List of Parts

1 Robot cell/Deburring cell

2 Control equipment

3 Robot

4 Working head

5 Deposition area, entrance area

6 Outer gate

7 Inner gate

8 Workpiece

9 First tool

9a Cutting wheel

10 Slide/Chute

10a Box

11 Second tool

11a Abrasive wheel

12 Deposition area, exit, conveyor

13 Unloading area

14 Door

15 Baseplate

16 Baseframe

17 Bolts

18 Lifting hooks, eye bolts

19 Rear wall

20 Front wall

21 Top

22 Sidewall

23 Sidewall

24 Lifting aperture

25 Inspection window

26 Power-supply connector

27 Exit aperture 28 Outlet hole

30 Base / Proximal robot datum

31 First robot arm 31a Pivot pin

32 Second robot arm 32a Pivot pin

33 Third robot arm

34 Fourth robot arm 34a Pivot pin

35 Fifth robot arm

36 Distal robot part

37 Distal part (of 34)

A1 First degree of freedom, rotary joint

A2 Second degree of freedom, pivoting joint

A3 Third degree of freedom, pivoting joint

A4 Fourth degree of freedom, rotary joint

A5 Fifth degree of freedom, pivoting joint A6 Sixth degree of freedom, rotary joint

50 Baseplate for trueing-up system

51 Trueing-up tool

52 First sensor 53 Second sensor

54 Measurement processing circuit

55 Conduit

56 Fixing screws

57 Stationary sensor 60 Baseplate

61 Energy converter

65 Inner guide roller Outer guide roller Spacer-roller unit Tensioning device

Claims

1. System for deburring or grinding a workpiece (8) using a manipulator or robot (3) provided with gripping means (4) to grip the workpiece (8) to be deburred or ground, said system comprising at least one stationary, rotating deburring means (9, 9a, 11, 11a), e.g. an abrasive wheel (9a, 11a), said deburring means being tru- ed-up from time to time, and in which the robot is controlled to move the contour or contours of the workpiece to be deburred past the deburring means with a correct pre-loading and/or spacing for carrying out the deburring, characterized in that the robot is provided with at least one non-contact sensor (52, 53), especially of the optical or distance-sensing kind, for sensing a surface position on the debur¬ ring means (9, 9a, 11, 11a).

2. System according to claim 1, characterized in that the robot (3) is provided with at least one trueing-up unit (51) placed on the working head (4) or a part (34-36) of the robot being proximal in relation thereto, especially the second part proximally of a joint connecting the working head, said trueing-up unit (51) be¬ ing adapted to carry out trueing-up of the deburring means (9, 9a, 11, 11a).

3. System according to claim 1or2, characterized by at least one fur¬ ther sensor (57), especially of the optical or proximity-sensing kind, placed stationa¬ ry adjacent the deburring means (9, 11).

4. Method of deburring or grinding using a system according to any one or any of the claims 1-3 for deburring a workpiece (8) using a manipulator or robot (3) provided with gripping means (4) to grip the workpiece to be deburred, there being at least one stationary grinding wheel (9a, 11a) or other rotating deburring means being trued-up from time to time, and in which the robot is controlled to move the contour or contours of the workpiece to be deburred past the grinding wheel with correct pre-loading and/or spacing for carrying out the deburring, character¬ ized in that the robot in a first calibrating step takes up a given position, in which a sensor (52, 53) on the robot is located immediately outside of the largest periphe- ry, which the grinding wheel can have or was measured as having during the previ¬ ous calibrating operation, after which the robot moves the sensor towards the sur¬ face of the grinding wheel until its surface is registered, said registering subsequ¬ ently being used for either: adjusting the initial position and/or pre-loading of the robot for a subsequent deburring step, or to decide whether the grinding wheel is to be trued-up, and if so to which size, or to decide whether the grinding wheel is to be replaced.

5. Method according to claim 4, c h a r a c t e r i z e d in that in a trueing-up step, a trueing-up means (51) carried by the robot (3) is moved into abutment with the surface of the grinding wheel (9a, 11a), after which the trueing-up means is moved into a position determined on the basis of the previous registering of the surface of the grinding wheel.

6. Method according to claim 5, c h a r a c t e r i z e d in that in a step of true¬ ing-up and calibrating, the robot (3) is set to a given position causing a surface on a trueing-up means (51) carried by the robot to be placed immediately outside of a stationary, especially contact-less sensor (57) placed adjacent to the grinding wheel (9, 9a, 11, 11a) and in which the initial position for said surface is either de¬ termined beforehand, determined according to the most advanced position to be taken up by the trueing-up means, or determined as measured at the previous cali¬ brating operation, after which the robot moves the trueing-up tool towards the sen- sor until the surface is registered, said registering subsequently being utilized for either: adjusting the initial position and/or the pre-loading of the manipulator during a subsequent trueing-up process, or for deciding whether the trueing-up tool is to be replaced.

7. Method according to claim 6, characterized in that the first calibrating step is carried out at the start and then continuously after a given number of, at least one, intermediary deburring process or processes, that at the start, a step of calibrating the trueing-up means is carried out, that at the start, a trueing-up step is possibly carried out, that a trueing-up step is carried out each time a given number or at least one calibrating step or steps has/have been carried out, and that a step of trueing-up and calibrating is carried out each time a given num¬ ber of, at least one, trueing-up step has/have been carried out.

8. Method according to any one or any of the claims 4-7, characterized in that the positional registration in the calibrating steps is exclusively used for final positioning of the robot (3) during the processing and calibrating processes referred to, and not to initialize the robot proper.

9. Use of the system and the method according to any one or any of the claims 1-8 for deburring medium-heavy objects (8) of between 1 and 500 kg, especially between 15 and 200 kg.