DE1930367A1 - Method or device for processing a moving workpiece - Google Patents

Description

19303a?

s *

DIFL. ING. B. HOIiZSB 80 AtTGSBUlEO

-ΉΠΒL8KB-STIiA.ee »M OUiHi SMfS

Aiagsbarg., June 12, 1969

National Research Development Corporation, Kingsgate House, 66-74 Victoria Street, London, S.W.l, England

Method or device for processing a self moving workpiece

The invention relates to the machining of moving Workpieces and in particular, but not exclusively, automatic balancing or automatic balancing machines.

Due to the increasing use of devices, which with

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have high speed rotating machine parts, it has become necessary to develop fully automatic dynamic balancing machines, which can be used in mass production are adjusted on the assembly line.

Automatic balancing devices used in the automotive industry are already known.

Here, the machine part to be balanced is initially set to a level sufficient for plaguing and recording an imbalance Speed brought and then stopped, after which this part is adjusted circumferentially until the point from which material must be removed to correct the imbalance, one located at a certain point Opposite cutting tool. In the subsequent machining process, a certain relationship is established between the depth of cut and the vibration ™ caused by the imbalance amplitude complied with. In general, the rotating machine part is then brought up to the balancing speed again, to check the effectiveness of the correction.

Depending on the desired balancing tolerance, this is Process relatively cheap and reliable if the weight of the parts to be balanced is over a few kilograms and the material in question is easy to process.

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However, when it comes to materials that resist normal machining, it is difficult to to control the removal of the unbalanced masses and accordingly repeated balancing operations are required. Often one takes Recourse to hand-held grinding tools, with each machine part being machined in an on-off mode.

Among the other processing options available, electron beam processing, by electrical discharge and by means of a laser beam the advantage that the material removal is not influenced by the mechanical properties of the material in question and that the machining can be carried out while the machine part in question is at the balancing speed turns. Electron beam processing machines are expensive and it is impractical to operate them under vacuum. The machining by electrical discharge machining is not very effective and difficult to control in air. When processing with a laser beam, the low pulse repetition frequency of the laser system and the thermal load capacity limit of the cavity, the processing speed, but the processing can take place in a room atmosphere and the Removal parameters can be well controlled.

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Processing with a laser is preferable as it allows semi-automatic or automatic operation, because so-called hard materials can be machined, and also only a negligibly low cutting pressure is required and because finally material removal can be carried out at the balancing speed. The editing can only be done at low speed and the costs per laser pulse limit this processing method, as far as it applies to balancing, to small rotating parts or rotors.

It is therefore desirable to maximize both the efficiency of the removal and the power density of the focused point of light is dependent, as, too to increase the total ablation rate per pulse maximally, which of the total energy and thus of the depends on the respective pulse length.

For each material there is an optimal energy density, which depends on the physical properties of the material in question is dependent, with the largest Energy density for materials with high thermal conductivity is to be assumed.

90985

When between the focused point of light and the workpiece a relative movement takes place, as in the case of balancing is the case, the resulting power density is reduced and the loss of material removed during balancing in the normal range of linear peripheral speeds * - the effect is considerable. Although it is possible to provide for an increase in the laser energy to compensate for the machining energy to be provided at standstill, but it must then the thermal load on the laser rooms can be increased considerably, which is why the average is reduced Pulse length and therefore a reduction in the total energy per pulse is required. The effort and the costs of the system are also increased. But it is essential that the load on the laser is within normal limits is kept in order to keep the cost per pulse low and to avoid reducing the life of the laser. Unfortunately, the erosion energy cannot be increased by using a Q-switching operation because then the power of the laser for the duration of each short pulse is considerably above the optimum, while however the output energy is low because of the individual pulses are short. In addition, there is an uncertainty regarding the life of the major parts of the laser, these considerations allow the Q-switching operation to be complete

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appear uneconomical »

The object of the invention is to be achieved, the removal effect when machining moving work " to increase pieces economically by means of a laser beam *

Based on a process for processing because of the workpieces, in which light emitted by a laser hits a certain area of the Workpiece is directed, the solution of the stated object is achieved according to the invention in that the beam path of the emitted light is changed during the movement of the workpiece so that the point of light incidence on the workpiece the mentioned area to be processed follows *

The invention also provides a device for Proposed execution of this method in which an optical system is provided in the beam path, which diffracts and / or reflects the light emanating from the laser mentioned in such a way that the emitted light is directed onto the The area of the moving workpiece falls and this area is followed by t

If the specified area to be processed is moving

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Workpiece when moving along a circular path, such as if this is the case, for example, with a rotating workpiece, then it is the optical device or the optical system preferably synchronized with the workpiece movement and the light emitted by the laser follows that to be processed Area during part of each cycle until machining is finished.

By tracking the point of light focused on the workpiece on the area to be processed, the effective removal energy can be increased. Since a certain area is processed repeatedly, a local one is made Machining and the process of removal are the same as for a stationary workpiece. The erosion is more effective because the machining process, once started, is more effective than at the beginning, which is true at least for a certain period of time.

The laser is preferably operated in burst mode and has a device according to the invention suitable for this purpose Control means to control the intensity of the laser beam by controlling the laser pumping speed as well as controlling the pulse length and thus the ablation energy. The control means may include a delay line,

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which with a flash tube that supplies the pump energy for the laser is coupled.

The optical devices or the optical system can contain a prism with two mutually parallel prismatic surfaces, which are arranged on the axis of the emitted light beam and with their mutually parallel surfaces parallel to this axis. Furthermore, drive means are provided for rotating the prism about an axis which is perpendicular to said surfaces and to a plane which contains the axis of the emitted light beam and the workpiece area to be machined. The arrangement is made so that while the said area is approaching the prism, the light emerging from the laser undergoes total internal reflection in the prism, is directed onto the area to be processed and follows this area, while this ψ is relatively close to the prism is located.

When machining rotating workpieces, two identical prisms are provided, each two have mutually parallel surfaces which have the shape of isosceles, right-angled triangles. Those Prism faces on opposite sides of each of the two hypotenuses of the right-angled triangles

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are limited, are directly opposite one another, but do not touch. The drive means can then drive the prism assembly at half the speed of the workpiece.

For machining workpieces, the. according to the invention Device be provided with setting means that allow a change and display of the point on which the light directed by the laser hits the workpiece, whereby precautions are taken by which this point can be brought into a predetermined position, on which editing is to be carried out.

For the purpose of balancing, the device according to the invention with measuring elements for determining the in a certain Effective imbalance forces can be provided at the level and display devices can also be provided which specify the location of a certain material area of a workpiece, which is used to produce the dynamic compensation on Workpiece is to be removed. The above-mentioned point and the point indicated by the display means can then be used for Coverage: be possible.

The measuring device can contain two wattmeters, from

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whose outputs each have a signal that can be picked up proportional to the output indicator. These wattmeters deliver In Icartesian coordinates, a designation of the material area that is to be removed for the purpose of balancing is. Furthermore, a potentiometer corresponding to a sine function, which is connected to the output of one of the wattmeters is coupled, a cosine function corresponding ^ potentiometer, which is connected to the output of the other wattmeter is coupled and a summation circuit can be provided, which adds the outputs of the potentiometers, so that 3ich pin Signal variable phase results, which depends on the setting of the potentiometer and to drive a motor which controls the setting with which the light emitted by the laser is directed onto the workpiece will.

_k The term used in this description

"Machining" includes not only the removal and ablation of material by means of a laser beam, but also the deposition or application of material on a workpiece by means of such an energy beam, also the Machining carried out for the purpose of balancing can be done by applying material.

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AA

For the purpose of depositing or applying material a wire or thread of the material to be applied is brought into the focus of the energy beam. The latter causes an explosion or evaporation of the material, which then occurs at the desired points on the relevant, is deposited near the focal point of the workpiece.

In the following, the invention is illustrated by the description of specific exemplary embodiments with reference to FIG explained in more detail in the accompanying drawings. In the drawings show:

1 shows an arrangement according to the invention,

by means of which a laser beam can be made to target a certain area of a circumferential To follow the workpiece during part of this cycle,

Fig. 2 is a block diagram of a he

inventive device for balancing a rotating Part,

Fig. 3a shows the shape of the pulse of a

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Laser, which is operated in burst mode,

Fig. 3b shows the shape of a pulse of a

Laser operating in Q switching mode is operated,

4 shows the circuit diagram of a delay line and a flash tube which is used in the device according to FIG. _2A , and

Fig. 5 to 10 further arrangements for guidance

of a laser beam or its focal point along a desired one Way.

In the device according to FIG. 1 of the drawings , a light beam emanating from a laser 10 is focused by means of a lens 11 and deflected in a prism 12 by total internal reflection before it strikes a rotor 13 to be balanced. The rotor rotates in the direction of arrow 14 so that unbalance forces can be determined and the prism 12 is rotated about an axis 15 which is right

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at an angle to the plane of the drawing of Hg. 1, the Rotation in the direction of arrow 16 takes place. The focal point of the bundle of light rays then moves along a path which approximately coincides with part of the path of a point on the rotor. To show the path of the focal point for a position 12 * of the prism indicated by broken lines, the beam path 18 is also through broken lines drawn. The beam path shown in solid lines corresponds to a central position and the machining of the rotor takes place approximately between the point indicated by broken lines and a corresponding point on the side opposite the center position. Outside these limits the point of incidence of the beam moves away from the focal point, as can be seen from FIG. 1, and the The beam hits the rotor surface more tangentially.

Opposite the prism 12, another prism 19 is arranged so that its largest surface corresponds to the corresponding one Surface of the prism 12 is directly opposite, but does not touch it, so that the two surfaces through a Air layers are separated from each other and total internal reflection can take place in the prisms. By using of two prisms, the speed of the prisms can be half as great

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be chosen because after every half turn one prism takes the place of the other prism.

To balance a rotating part, it is necessary to determine the location of a material area, the removal of which leads to a reduction in the imbalance forces on a ^ tolerable level leads, and then this material range accordingly to be removed. This material range is determined by means of known devices, for example according to 'Schenk carried out, which is briefly discussed below, and the removal of the relevant material area made by means of a device according to the invention, in which a laser beam with the workpiece movement is synchronized that the beam of the laser during part of each revolution follows the area to be removed.

As can be seen from Fig. 2 of the drawings, the rotor 13 is mounted in two bearings held by sensors 21 and 22 and is in a manner not shown in detail via an air drive or a magnetic drive offset in rotation. For balancing, the imbalance must be determined in two planes and the feelers are located accordingly in these levels. The sensors 21 and 22 have magnetic cores 23

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/ • Γ

and 2 ¹ I, the displacements of which within coils 25 and are proportional to the effective unbalance forces.

A light receiver 27 is used to relate these forces to a specific part of the rotor provided, the Lichtirapulse from the rotor picks up, the latter is provided with a strip in the same black and white colored areas is divided. The output signal of the light receiver 27 is in the form of a square wave, whose repetition frequency corresponds to the speed of the rotor. This square wave is in a converter circuit 28 transformed into a sine wave and, then on the one hand a wattmeter 29 and, on the other hand, a wattmeter 32 via a 90 ° phase shifter 31. The ones from the Displays supplied with wattmeters show the position of the desired area on the rotor in Cartesian coordinates, the origin of the coordinates being on the rotor axis and the x-axis and the y-axis in known relation to the The border between the black and white areas of the mentioned stripe.

When determining the unbalance according to Schenk, the display shows a light beam is used, which is reflected at two mirrors arranged one behind the other, the Mirror can be adjusted by angle, which leads to the "initial.

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Signals from the wattmeter are proportional. This bundle of light rays is then projected onto a ground glass, so that you get a point of light whose position the respective position of the desired area on the rotor.

The apparatus of Figure 2 of the drawings includes an evaluation device according to Schenk, which is indicated schematically at 85. In addition, there are wattmeter outputs which provide electrical signals proportional to the wattmeter readings. These output signals are potentiometers coupled via amplifiers 33 and 34, respectively or 36 supplied, the winding resistances of which are each depending on the position of the sliding contact after a Change sine function or after a cosine function. the Signals that can be taken from the potentiometers can be added vectorially in an amplifier 37, so that a sinusoidal signal results, whose phase position with reference to the phases of the wattmeter signals by changing the Setting of the sliding contacts of the mentioned potentiometers and 36 can be changed.

The output signal of the amplifier 37 is fed to a pulse shaper 38, which is fed to an amplifier 40 emits a square wave signal. The amplifier 40 is over

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4Ψ

another amplifier 41 connected to a motor 42, which drives the prisms 12 and 19, which in the Pig. 2 according to the direction of view along the arrow 1 of the drawings as above the end of the laser IO are shown located. A frequency dividing circuit 39 reduces the frequency of the signal fed to the motor 42 by half, so that the speed of this motor increases accordingly halved.

Since there is an inevitable delay in firing a laser, there is between amplifier 40 and one of the laser associated logic safety circuit 45 is a phase delay circuit 44 placed. The output of the logical Safety circuit 45 is used to control a trip unit 46 to ignite the laser 10. At a point in time which lags behind the rotation of the prism by almost 360 °, the Phase delay circuit 44 once during each revolution of the rotor 13 the possibility of triggering of the laser, so that it can be actuated to emit a pulse that is in phase with the prism movement can.

A device, indicated schematically at 86 and connected to the amplifier, generates a on a ground glass Point of light, which denotes that rotor point on

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which the light emitted by the laser is incident on.

To balance a rotor, it is set in rotation and a light point appears at the optical outputs of the wattmeter 29, which indicates the position of the workpiece area to be removed. The coupled potentiometers 35 and 36 are then adjusted until the point of light indicating the point of impact of the laser beam on the rotor coincides with the point of light indicating the position of the workpiece area to be removed. A key (not shown) forming part of the safety logic circuit is then depressed so that the trigger unit 46 is able to ignite the laser at the desired time during each revolution of the rotor. While material is being removed from the rotor, the optical indicators of the wattmeters 29 and 32 show a reduction in the unwanted forces ψ and when these forces have reached a permissible limit, the button is released.

With the coil 26, the converter circuit 28 and the phase shifter 31 are two more, not shown Wattmeter connected in the same way as wattmeter 29 and 32. These other wattmeters also have optical ones Output means and their electrical outputs can be via

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a changeover switch (not shown) can be connected to the inputs of amplifiers 33 and J> k instead of the outputs of wattmeters 29 and 32.

If you take care in a known manner that the the coils 25 and 26 supplied signals proportionally to the associated wattmeters in each case according to the distance of the Rotor 13 and the bearing 21 are fed from the bearing 22, a balancing takes place on the basis of the bearing determined imbalance forces independent of imbalance forces, which are found on the bearing 22. Are the imbalance forces absorbed at the bearing 21 to a permissible Limit has been reduced, the aforementioned changeover switch is operated and the same process is used to reduce the Storage 22 determined imbalance forces repeated to an acceptable level.

As mentioned earlier, the laser is preferably used in the Pig. 3a of the drawings indicated push operation actuated, and not in the in, Fig. 3b of the drawings indicated Q-switching operation. In order to obtain the desired duration of the impact su, which can be between 600 microseconds and 10 milliseconds depending on the rotor material to be removed, the release unit H6 contains a Pig. ² I.

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of the drawings, where; for different materials are used in each case with different delay lines.

A flash tube 47, which the pump energy for the Laser IO supplies is via a delay line that contains a series of capacitors CL through C and a series of Contains inductors L. to L, with a direct current source 48 connected. If an electronic switch ^ 9 is closed, so the capacitors are charged until the voltage applied to the capacitor C has reached a certain ' Has reached value. The logical safety circuit is capable of determine that the delay line is ready for operation and emits a trigger pulse to the flash tube, wherein the trigger pulse is provided in the correct phase relationship in the manner described. After discharge of the capacitors, the process is repeated until the holder lJ9 is opened again.

Since the flash tube 4? has a low impedance of the order of 0.2 ohms to 0.3 ohms, does the delay line match the tube ¹ I step by step? each stage containing a capacitor and an inductor. The last stage (C _n L _n ) determines the rise

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Yes, the envelope of the impulse surge and the total value of the inductances and capacitances determines the duration of the surge in each case between the burst duration, the rise time, the adaptation and the physical limit values of the flash tube to *

meet.

While the above description of an exemplary embodiment serves to explain an arrangement with a double prism, there are of course also other possibilities for causing the light point of the laser to follow a workpiece area to be machined. For example, a single prism can be used by either simply removing prism 19 and doubling the speed of motor 42, or by using an arrangement shown in Figure 5 of the drawings. A light beam 51 emanating from a laser is reflected in a prism 52, which is set in rotation about an axis in the direction of rotation indicated by the arrow 5 ^, so that a focal point generated by a lens 55 follows a path indicated by the arrow 56.

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Furthermore, a moving lens system can be used in which, as shown in FIG. Another possibility is to move about an axis 63 in rotation, which is perpendicular to the drawing plane of FIG. 7 of the drawings, and through the center of curvature of the convex lens surface "is so that a focal point of 6k in the direction of an arrow 65 'a plano-convex lens 62 emotional.

As shown in FIGS. 8 and 9 of the drawings is shown, mirrors can be used to move the focal point, a mirror 66 may, for example, about the axis of a laser beam are made to rotate 67, wherein the ψ laser beam by a lens 69 on a rotor 68 is focused. The laser beam is directed from the rotating mirror onto a cylindrical mirror 70 which is arranged coaxially to the laser beam 67 and which reflects the laser beam on its inner surface, which is only partially shown. With this arrangement it can be achieved that the focal point follows the area to be processed during the entire rotation time.

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In the arrangement according to FIG. 9 of the drawings, a mirror 72 is rotated about an axis 73 which is on the plane of the drawing stand vertically. The rotation takes place in the direction of an arrow 74 'so that a focal point 75 follows a path which is indicated by the arrow 76 and runs close to the surface of a rotor 77.

Finally, as in Fig. 10 of the drawings is shown, a transparent cube 78 such in Revolution are offset so that a focal point 79 describes a trajectory indicated by an arrow 80.

The invention is of course not limited to the balancing of any parts, but can can also be used to machine parts that can either rotate or move linearly. In the Machining rotating workpieces can, for example, be used in an embodiment of the invention that is modified compared to FIG. 2 of the drawings. The location of the to be removed Area with respect to the boundaries between the black and white marker areas is known and will be similar the system for reproducing the displays of the wattmeter 29 and shown on a ground glass. The converter circuit 28 and the phase shifter 31 are directly connected to the Yer

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stronger 33 and 3 ¹ I connected and you get a display which indicates the point at which the laser beam strikes the workpiece.

To carry out a processing, the potentiometers 35 and 36 are adjusted until the one to be processed _ The area coincides with the point of incidence of the laser beam and the aforementioned button is then used until the end the processing depressed.

A manual adjustment of the potentiometers 35 and 36 can be avoided both during balancing and other types of processing if the outputs of the amplifiers and 3 ^ are compared with the image which indicates the point of impact of the laser on the workpiece. An error signal is determined by comparing obtained which is fed to a ψ servo mechanism serving the error signal to adjust the potentiometer in the sense of a reduction. The end of the balancing or machining process is then determined by the logic circuit.

It should also be pointed out that the balancing or machining according to the invention does not apply to the only example described type of synchronization of the laser beam with the workpiece is limited.

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Claims (1)

is- Claims 1. A method for processing moving workpieces in which light emitted by a laser occurs a certain area of the workpiece to be machined is directed, characterized in that the beam path of the emitted light during the movement of the workpiece is changed so that the point of incidence of the light on the workpiece follows the area to be machined. ». ! The method according to claim 1, "in particular for dynamic balancing, in which the plane parallel to the direction of rotation is effective on a rotating part Imbalance forces are measured and the position of an area of the relevant part is determined by processing it the imbalance forces are lower, and at which the light emitted by the laser on the mentioned area is directed, characterized in that the beam path of the emitted light during the rotation of the part is changed in such a way that the point of incidence of the light falls to the region mentioned in each case during at least part of each revolution follows, - 25 - 90085 1/0414 3. A device for performing the method according to claim 1 or 2, characterized in that in the beam path, an optical system (12, 19 or 52 or 57 or 66 or 70 or 72 or 78) is provided which _s the light emitted by the laser (10) diffracts and / or reflects in such a way that the emitted light is directed onto the ^ Area of the moving workpiece or the rotating part (13 or 68) falls and this area follows. 4. Device according to claim 3 for processing workpieces which perform a movement which runs at least in a certain area within a circular path, characterized in that at least part of the optical system (12 »19 or 52 tosw. 57 or, 62 or 66, 70 or or 78) is movable in this way. that the beam path of the ™ emitted light follows the range mentioned, and that In addition, Synchronisiereinriehtungeia (27 to 42) are provided are, by means of which the movement of the optical system or the relevant part of the optical system with the Workpiece movement can be synchronized in such a way that the Beam path of the emitted light until the end of the Machining of the mentioned area follows during a part of each workpiece cycle. - 26 - 90985170414 5. Device according to claim 3 or 4, characterized in that the optical system has a prism (12) has two parallel surfaces, which around one to these and one to the axis of the emitted light as well as the plane containing the area to be processed is rotatable (42) perpendicular to the axis, and that in addition the arrangement is made so that when the area to be processed approaches the prism, the " Light experiences total internal reflection in the prism and is directed to the area mentioned, which the beam path follows, while this area to be processed located relatively close to the prism (Fig. 1). 6. Device according to claim 5 for performing the method according to claim 2, characterized in that a further prism (19) is provided, that further each of the prisms (12, 19) each have two mutually parallel surfaces ι possesses, each of which has the shape of right-angled, isosceles triangles, that further the opposite to each other Sides bounded by the hypotenuses of these triangular surfaces Prism surfaces of the two prisms are opposite each other, but do not just touch and that finally the both prisms can be driven together (42), the drive means of these prisms at half the speed of the workpiece or drive the rotating part (Fig. 1). - 27 - 909851/0414 7. Device according to claim 3 or 4, characterized in that that the optical system includes a prism (52) which is on the axis of the light emitted by the laser Rahlenbünde Is (51) is arranged and has prism surfaces parallel to this axis as well as to one another, that furthermore Drive means are provided for rotating the prism about said axis (53) and that finally the arrangement is made ^ is that during the approach of the area to be machined of the rotating part to the prism that of the laser emitted light in the prism total internal reflection learns in such a way that it is directed to the area to be processed and follows this area while the area is relatively close to the prism (Fig. 5). 8. Device according to claim 3 or 4, characterized in that the optical system includes a bilaterally convex lens (57), that, furthermore, drive means for moving said lens w perpendicular to its optical axis by the light emitted from the laser light beam (59) is provided through and that the arrangement is such that the light passing through the lens is essentially focused on the area to be processed (58) and follows this area as it passes the lens (Pig. 6). - 28 - 90985 1/04 1 A 9. Device according to claim 3 or 4, characterized in that the optical system has a mirror (70) with a curved, to the axis of rotation (67) of the area to be processed coaxial mirror surface, further a further mirror (66) for reflecting the from light emitted by the laser onto the first-mentioned mirror with a mirror surface lying on the axis (67) of the emitted light, but forming an angle to this, and finally drive means which serve to rotate the further mirror around the axis of the emitted light, so that a cylindrical surface is swept, the arrangement being such that the light emanating from the laser is thrown onto the latter during the rotation of the second mirror and is reflected from there onto the first mirror, from where the light falls on the area to be processed, while this rotates (Fig. 8). 10. Device according to claim 3 or 4, characterized in that ' shows that the optical system contains a mirror (72) which is in the beam path of the emitted by the laser Light lies, and that drive means for rotating this Mirror are provided around an axis (73) perpendicular to the direction of movement of the area to be processed, the The arrangement is made in such a way that when the area to be processed approaches the mirror, the - 29 - 909 851/0414 outgoing light is reflected on the said bar area and the beam path follows the area as it moves relatively close to the mirror (Fig. 9). 11. Device according to claim 3 or 4, characterized in that the optical system contains a cuboid JBlock (78) made of transparent material, which is arranged in the beam path of the light emitted by the laser and that drive means for rotating the block about one to the direction of movement ( 80) of the au machined area perpendicular axis are provided, the arrangement being such ₉ that is at the approach of said range to block the light emanating from the laser light keiia passage broken by the block and directed to the su machined, while this moves close to the block (Fig, 10). 12. Device according to one of 6 claims 3 to H _3, characterized in that a Yorriehtung is provided for ¥ change and display that point at which the light emitted by the laser would be incident on the memory piece when the laser is operated. 13 «Device according to claim 12 for balancing a rotating workpiece, with measuring devices for determination 80 9851/0414 of unbalance forces in a certain plane and display means for displaying the position of an area of the workpiece in question, the machining of which leads to a reduction in the unbalance forces, marked by the fact that the point at which the light emitted by the laser would impinge on the workpiece when the laser is actuated , can be changed such that this point coincides with the direction indicated by the position indicating means and that then the laser is activated so long until the _s are effective in the said plane unbalance forces is reduced to an acceptable level (Fig. 2). Ik. Device according to claim 13 »characterized in that a cyclical electrical signal can be taken from the measuring device (23, 25, 24, 26), the amplitude and phase position of which depends on the size or the instantaneous position of a material area, the removal of which leads to a reduction the imbalance forces effective in the plane concerned would result in the display means also having a position reference signal source (27, 28) which presents a cyclical signal whose phase position is dependent on the current position of a reference point on the workpiece (13) two wattmeters (29 _s 32) are provided, each having two inputs, their - 31 - 909851 / OAU τι the signal of the measuring device is fed to one input each, while the signal of the position reference signal source the second input of one wattmeter directly and the second input of the other wattmeter via a phase shifter (3D which causes a 90 ° phase shift) that further every wattmeter has an output from which one to the respective P Display of the relevant wattmeter, proportional signal it can be removed that, furthermore, a potentiometer corresponding to a sinusoidal function is connected to the output of one wattmeter (35) is coupled, while a cosine function corresponding to the output of the other wattmeter Potentiometer (36) is coupled and that finally a summation device (37) for summing the output signals of the two potentiometers is provided, of which each depending on the respective setting of the mentioned ^ Potentiometer a signal that changes in phase is detachable, which is used to feed a rotating part of the optical system (12, 19) performing Motor serves to control the position of the point of incidence of the light emitted by the laser on the workpiece (Fig. 2). 15. Device according to one of claims 3 to 14, characterized by control means for controlling the pumping - 32 - 90985 1/04 V3 energy for the laser in such a way that it is operated in burst mode (Fig. 4). 16. The device according to claim 15 »characterized in that the control means includes a delay line (C ₁ to C, L ₁ to L _n ) which is connected to a flash tube (47) for generating the pump energy for the laser, and that this delay line is constructed from several stages connected in series to one another, each of which contains a series inductance and a parallel capacitance (FIG. 4). - 33 909851/0414 -31 * r Lee on the back