DE2537630A1 - GRINDING METHOD AND GRINDING EQUIPMENT - Google Patents

Description

Grinding method and grinder

The invention relates to a grinding method according to the preamble of the main claim and a grinding device, in particular for carrying out the same according to the preamble of the main device claim.

There are known grinding processes in which the feed table, who carries the "workpiece, with a constant feed rate is moved in the direction of the grinding head, after which a spark-out is maintained for a desired period of time v / ird. The workpiece is ground to the desired diameter in an internal grinding machine, namely at constant feed.

However, in this grinding process, in which a constant feed rate is maintained, the rate at which material is removed decreases as the grinding. head or the grinding wheel or the grinding wheel becomes increasingly blunt. The grinding behavior is thus reduced proportionally to the dulling of the grinding tool. For the constant feed, a greater force is increasingly required, which can rise above a reasonable value. The surface roughness and the cylindricity of the V, ^tee also deteriorate.

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In the conventional methods, there is therefore an aftertreatment of the grinding wheel or the grinding head or the Grinding wheel after a predetermined number of workpieces has been ground, which is done by means of a corresponding Counter is determined. This number is determined according to the differences in the grinding head, the material of the workpiece »dem State of grinding or the desired fineness of the grinding process varies. A deviation in the workpiece diameter after an advanced process or a deviation in the grinding head often leads to the grinding head becoming blunt faster than was calculated in advance. The grinding process will thus continue with a blunt grinding tool until the predetermined number of grinding processes has ended is brought. This will improve the quality of the grinding process degraded.

Conversely, it can happen that a ship after a predetermined number of grinding operations is still sharp and has a good grinding ability, so that the grinding tool is reworked prematurely or too often, which shortens its service life. This also leads to the operating speed of the grinding machine being reduced.

The present invention is therefore based on the object of avoiding the errors and disadvantages mentioned above. These The object is according to the invention by the grinding method according to the subject of the main claim. solved. Advantageous further training this method are described in the subclaims.

The invention also aims to create a grinding machine, especially to carry out this procedure. This task is made by the subject of the main device claim Particularly advantageous developments of this device are described in the sub-device claims.

With the invention it is possible to control the grinding conditions, such as the. Feed speed on a grinding machine according to the changing conditions or pheno-

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menen during the grinding process.

With the invention, a grinding method is thus created "at where the speed of material removal is controlled and "where you get a superior cylindricity and roundness of the ground Workpiece received.

The invention also provides a grinding method and an apparatus for carrying out the same, in which a speed control of the material removal takes place, with a suitable feed speed for the Grinding head or the grinding wheel or the grinding wheel is maintained in such a way that the grinding wheel or the The grinding wheel or the grinding head maintains its grinding ability over a long period of time after an aftertreatment, with after-treatment of the grinding head or of the grinding wheel or of the grinding wheel, which is carried out too often, is avoided.

The invention also provides a grinding method and an apparatus for carrying out the same, in which a combination of speed control of material removal and residual material removal control takes place, with both a good efficiency for the grinding process achieved with short grinding cycles and precise fine grinding of the tool.

The invention finally provides a grinding method and an apparatus for carrying out the same, which a combination of speed control for material removal and a ratio control of the feed speed to the workpiece speed, superior surface roughness as well as good cylindricity and roundness are obtained on the workpiece.

Essential features of the invention are thus in a grinding process and to see a device for carrying out the same, in which the material distance from the workpiece con

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continuously or intermittently during a grinding process is measured and compared with predetermined material removal values established as a program, the difference a control of a drive device between the actual material distance versus the programmed value of the feed table causes this difference. is canceled or compensated.

In the case of the grinding method and grinding device according to the invention a control of the speed at which a material removal takes place from the workpiece, at least during the fine grinding process to predetermined values. The material removal is measured by a detector, which determines the size during the grinding process itself, the obtained The value is compared directly or indirectly with previously determined values after a conversion into the material removal rate The deviation of the material removal from the predetermined value causes a control the feed movement of the feed table or feed slide, the relative feed between the grinding head and the Workpiece causes.

Further details and advantages of the invention can be found in the enclosed Drawing visible.

FIG. 1 shows a block diagram with a partial perspective illustration of a preferred embodiment of FIG Invention;

In the diagram, FIG. 2 shows the feed rate, the actual material distance and the force of the grinding process as a function from the time in the embodiment shown in Figure 1;

FIG. 3 shows a further embodiment of the invention in a block diagram;

FIG. 4 shows in diagram form the advance and the actual material removal as a function of the time for the embodiment shown in Figure 3;

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FIG. 5 shows a third in the form of a block diagram preferred embodiment of the invention;

FIG. 6 shows the advance and in the form of a diagram the actual material removal as a function of time for the embodiment shown in FIG.

In the following, FIG. 1 will first be discussed. FIG. 1 shows a centerless internal cylindrical grinding machine in which the method according to the invention for controlling the speed of material removal is used. Reference numeral 1 shows schematically the centerless internal cylindrical grinding machine with the bed 2. A grinding tool table or support 3 is mounted on the bed and is slidably displaceable in the axial direction of a grinding wheel spindle k located thereon. Furthermore, a workpiece support 5 is attached to the bed 2. A feed slide 6 is mounted on the grinding tool support 3 so that it can slide horizontally and perpendicularly to the grinding wheel spindle axis and carries a piece spindle head (not shown in the drawing). A servomotor 7, which causes the feed movement of the feed slide 6, is also attached to the bed 2. The workpiece spindle head rotatably holds a workpiece W in its spindle.

The reference number 8 denotes a detector which carries out a measurement during the grinding process and continuously measures the inner diameter of the workpiece W while it is being ground. The output of the detector 8 becomes one Operating or operational circuit 9 is supplied. A tachometer 1o determines the revolutions of the workpiece Di and generates a corresponding output signal that it sends to a sampling clock pulse generator 11 leads. Those generated by the sampling clock pulse generator 11 Clock pulses are also used by the operational circuit fed. The clock pulses act as gate pulses for the signals coming from the detector 8 in the operational circuit 9, and in such a way that a signal from the detector 8 with a first clock pulse from another signal with a second clock pulse is subtracted. Therefore, from the output signals of the detector 8 and the clock pulse generator 11, the material removing speed becomes ΔI of the inner diameter for a work

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Calculated number of revolutions and a differential amplifier 12 supplied. The differential amplifier 12 also receives a fourth for the material removal speed, which is set by a setting device 14 and via a selection scarf tkreis 13 is supplied. The output of the differential amplifier, which is proportional to the difference between its two input signals, is fed to a servo control mechanism 15 fed, which controls the servomotor 7 for the feed to a suitable feed speed for the feed slide 6 to be maintained in such a way that the output signal 'des Differential amplifier 12 goes to zero.

The servo control mechanism 15 functions as an amplifier. It also receives the output signals from Schmidt trigger circuits 16, which in turn receive an output signal from the detector 8. _{An output signal P 1 is} generated by one of the Schmidt trigger circuits 16 when it receives a signal indicating the size, which corresponds to a first inside diameter of the workpiece which is determined in advance. Another output signal P ₂ is generated when another Schmidt trigger circuit receives a signal about the size, which corresponds to a second predetermined inner diameter. The output signal P ^ switches the servo control mechanism 15 so that the input terminal which receives the output signal of the differential amplifier is interrupted and the advancement of the carriage 6 is stopped. The output signal Pp switches the servo control mechanism 15 to rapid reverse, so that the feed slide 6 performs a rapid reverse, which is shown in FIG.

Reference numeral 17 denotes a power consumption detector which detects the power consumption of the spindle motor of the grinding wheel spindle 4. This power consumption is proportional to the force occurring tangentially during grinding. The output signal of the power consumption detector 17 is fed to a comparison circuit 19, which further receives power consumption values set in advance from a power consumption value setting device. An output signal F _{Q of} the comparison

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circuit 19 is the selection circuit 13 as a switching signal fed. Another output signal F. is sent to the detector 8 supplied as a start signal.

When operating the embodiment described above, first of all, the grinding wheel spindle 4 is moved in the direction of the workpiece, with a grinding tool 4a, for example a Grinding head, a grinding wheel or a grinding wheel is inserted into the bore of the workpiece W. Then drives der.ServGsteuermechanismus 15 to the servo motor 7, so that this the feed slide 6 moves.

FIG. 2 shows a diagram from which it can be seen that the feed speed of the feed slide 6 is kept constant during the first step. When the inner wall of the workpiece W comes into contact with the grinding tool 4a and the wheel axis, which carries the grinding tool 4a, is slightly bent at its upper side, so that the grinding tool 4a begins to grind the workpiece W, the grinding force gradually increases as a result, as shown by curve I in FIG. The gradual increase in the grinding force increases the power consumption of the grinding wheel spindle motor. When the actual power consumption reaches a value F ^ which is predetermined by the power consumption value setting device 18, an output signal Fjyj is supplied to the detector 8, so that the detector 8 starts its size measurement. The signal supplied by the detector 8 is continuously fed to the operational circuit 9 and converted to a material removal speed Δ, Ι with the aid of the clock pulses that come from the clock pulse generator 11.

The differential amplifier 12 receives the speed ΔI and a first speed value <& o, set in advance, which is determined by the setting device 14 via the selection circuit 13 is supplied. The actual speed Δΐ is set in advance at the speed Δ-ο compared. The servomotor 7 is then controlled in such a way that the difference between the speeds Δ-Ι and Δο decreases. This ensures that the grinding tool

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4a the workpiece ¥ at a constant material removal rate Z \ ο grinds that is a removal of its own or residual material g has.

With this constant grinding process, the inside diameter increases of the workpiece to a value that corresponds to a value P ^ defined in advance, which is the Schmidt trigger level is predetermined in the Schmidt trigger circuit 16. At at this point, the supply of the signals from the differential amplifier 12 to the servo control mechanism 15 is stopped, so that a switchover takes place in order to effect a final feed drive or a fine grinding drive on the servomotor 7 which the feed slide 6 is moved at a very low speed in order to carry out regrinding. Short before Pp, the servo control mechanism 15 receives a stop signal by a detector which determines the position of the 'feed slide 6 and is not shown in Figure 1 to cause spark-out. As soon

the detector 8 determines the size P £, i.e. at the moment the inside diameter has its final size, the direction of rotation of the servo motor 7 is reversed, so that the feed slide 6 is returned and a grinding cycle is ended.

The grinding behavior of the grinding tool 4a is gradually deteriorated as successive grinding cycles are carried out, in each of which there is a feed in which Hl is kept the same / ο. This increases the grinding force and the power consumption for the grinding spindle reaches a value F. A switching signal F _{Q is} fed to the selection circuit 13 from the comparison circuit 19 so that a switchover from A.ο to Ao- (To, ie. A fourth takes place , which is slightly smaller than A o. This is transmitted to the differential amplifier 12. The differential amplifier 12 compares the actual material removal speed A I with the second previously set material removal speed Δ o - oo, the servomechanism 15 being controlled so that the This means that the feed speed of the feed slide 6 decreases, which

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is associated with a decrease in the rate of material removal from Δ Ι to ho - cTo.

This means that the grinding operation is carried out at a feed speed for controlling the feed slide 6, at which the material removal speed ^ I is reduced to Λ ο - ίο in accordance with the deterioration in the sharpness of the grinding tool or the grinding ability. As a result, the grinding force is kept smaller than F _Q and the material removal curve of FIG. 2 shifts downwards.

If the grinding head becomes more blunt, so that the grinding force again reaches the value F in the material removal control of " ^ I = Λ ο - ei ο" before the detector 8 delivers an output signal of P ^, the comparison circuit 19 again generates an output signal of F _Q and sends this to the selection circuit 13 »so that it is switched to the next stage, in which a first value set in advance by the setting device 14 is passed to the differential amplifier 12 via the selection circuit 13. The actual material removing speed A I in this case is therefore controlled so that it becomes equal to Δ ο -2 ei ο. After this control of the material removal rate, an output signal P ^ is supplied by the detector 8, after which the subsequent grinding process takes place in the same way as mentioned above.

When the grinding force is F again in a material removal control of "Al = Ao - 2 <io" is reached before the detector 8 supplies an output signal P ^, post-processing takes place, while the grinding cycle is stopped.

In the embodiment described above, a constant Maintain material removal so that excellent grinding behavior is obtained without too great a grinding behavior Load acts or without the workpiece surface being abraded, so that an excellent cylindricity and upper

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surface roughness is maintained on the workpieces. Post-processing is only necessary if the grinding behavior of the grinding tool is decreased and the grinding force increases above a predetermined limit value. This leads to a longer service life the grinding wheel, a higher degree of efficiency in the individual cycles of the grinding operation.

A second embodiment of the invention will now be described which is shown in FIGS. 3 and 4. In this embodiment, the rate of material removal is controlled for the fine grinding process step, while a constant feed rate for the rough grinding Process step is applied, which takes place before fine grinding. A rough grinding feed rate adjuster 31 defines a value in advance, with the surface of the square pieces at this value when grinding is relatively rough, but in which a high efficiency for the grinding process and a good cylindricity can be obtained. The preset by the setting device 31 ' put value is supplied to a selection circuit 32 to the Servo motor 7 to be controlled via the servo control mechanism 15.

With the reference numeral 33 is an adjusting device for Speed of material removal in the fine grinding process step designated. The adjustment device 33 consists of a pulse generator 33a, a pulse motor 33b, which is driven by the pulse generator 33a, and a potentiometer 33c which is rotated by the pulse motor 33b will. The potentiometer 33c produces an output signal which increases linearly with the rotation of the pulse motor Control of the speed of material removal during fine grinding.

The signal determined by the detector 8, which indicates the diameter of the workpiece, is transmitted via an amplifier 34 to a Operation circuit 35 is supplied together with the output signal of the potentiometer 33 °. The operation circuit 35 generates an output signal that is the difference between its two input

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signals is proportional, ie. the difference between the signal of the potentiometer 33c and the signal of the amplifier 34. This output signal of the operation circuit 35 is passed through an amplifier 36 is supplied to the selection circuit 32.

The output signal of the detector is transmitted via the amplifier 34 a comparison circuit 37 is supplied. The comparison circuit 37 further receives predetermined signals P- * and P., which are supplied by a step adjuster 38. P ^ corresponds to the switching point of the process step of Rough grinding to the step of fine grinding. P / corresponds to the final size of the workpieces. When the comparison circuit 37 determines that the input signal from the detector matches the signal provided by the step setting device 38 P ^ or P. coincides, it generates an output signal that the selection circuit 32 successively adjusted.

In the operation of this embodiment, the feed carriage is first moved forward rapidly by the servomotor 7 until the The grinding tool comes close to the workpiece. At this point, the selection circuit 32 is switched over so that the by the setting device 31 in advance of the value Servo control mechanism 15 is supplied. The servomotor 7 therefore drives the feed slide, as shown in Figure 4, with a rough grinding speed.

When the grinding process after performing a rough grinding and before fine grinding arrives at point P, of Figure 4, the output signal of the detector 8 falls with the signal P-, the Step setting device 38 together what is determined by the comparison circuit 37, which thereupon a coincidence signal generated. This coincidence signal causes the selection circuit 32 to switch over so that the signal of the rough grinding feed rate setting device 31 is turned off and the output of the operation circuit 35 to the servo control mechanism 15 is supplied.

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At point P, of Figure 3, the pulse generator 33a begins to supply its pulses to the pulse motor 33b, thereby producing the output signal of the potentiometer 33c increases linearly. The difference value between the output signal of the detector 8 and the rising one The output of the potentiometer 33c is obtained from the operation circuit 35 is calculated and supplied to the servo control mechanism 15 via the selection circuit 32. The servo motor will thereby driven at a speed that the material distance corresponds to the output signal of the potentiometer, so that a fine grinding process is carried out.

When the diameter of the workpiece reaches the final value, determined the comparison circuit 37 a coincidence of the output signal of the detector 8 and that from the step adjuster 38 transmitted signal P ^. It thus becomes a coincidence signal which switches the selection circuit 32, whereby the output signal of the operation circuit 35 is turned off or is interrupted. As a result, the servo control mechanism 15 'causes the servo motor 7 to reverse rapidly performs.

A third embodiment of the invention will now be explained which is shown in FIGS. 5 and 6. This embodiment includes a residual material removal control for rough grinding, for the finished or. Regrinding a feed rate workpiece speed control and for fine grinding before regrinding, a material removal speed control. Those with the reference numerals 6, 7, 8, 15 »33, 35 and 36 in FIG Parts correspond to parts given the same reference numerals in the embodiments of FIGS. 1 or 3.

Reference numeral 41 denotes a workpiece spindle which holds a workpiece. The workpiece spindle 41 is of driven by a direct current motor 42 which is controlled by a drive device 43.

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The servo control mechanism 15 and the drive device 43 are connected to the output terminals of a selection circuit 44 tied together.

A position detector 45 determines the feed position of the feed slide, which moves the workpiece to be ground attached to it relative to a grinding wheel.

The output signals of the position detector 45 and the detector 8 are received by a first operation circuit 46. the Difference between the actual feed signal provided by the position detector 45 and the material removal signal, that is supplied by the detector 8, ie. the remaining material removal is calculated and a second operation circuit 47 supplied. The second operation circuit 47 further receives a preset signal from a standard remainder removal adjuster 48 so that the difference between the actual residual material removal and is calculated from the signal set in advance. The calculated output of the second Operation circuit 47 is supplied to selection circuit 44 through an amplifier 49. This calculated output becomes used for the drive device 43 to control the servomotor 7 so that the feed slide with a constant Remaining material removal g (as shown in Figure 6) is advanced during the rough grinding process.

The output signal of the detector 8 is also sent to a comparison circuit 5o, which further receives three kinds of standard workpiece diameter values, of which Pg corresponds to the point of change at which from a rough grinding a transition is made to fine grinding, Py the change point corresponds to the transition from fine grinding to finish or regrinding, and Pg corresponds to the point at which the grinding process is ended. These values are set in advance in a setting device 51. The comparison circuit 5o supplies an output signal to the selection

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circuit 44 when the signal corresponding to the workpiece diameter, which is supplied by the detector 8, coincides with one of the standard workpiece diameter values Pg, Py or P _g , whereby the selection circuit 44 is switched to another state.

The selection circuit 44 also receives the calculated output signal of the third operational circuit 35 via the amplifier 36 as well as two values set in advance, one of which corresponds to the feed speed Vp of the feed slide 6 during regrinding and the other corresponds to the workpiece spindle revolutions N _w , which can be set on a regrinding condition setting device 52. This feed rate is very small compared to that in fine grinding. The ratio of this feed rate to the workpiece spindle speed is suitable for obtaining a superior surface roughness on the workpiece. The previously established values for Vp and for M ^ are fed to the servo control mechanism 15 or the drive device 43, so that the feed slide 6 and the workpiece spindle 41 are controlled.

A switchover takes place during operation of this third embodiment the feed speed of the feed slide with a transition at point P ^ from fast feed to rough grinding, as shown in Figure 6, so that rather selection circuit 44 signals for the coarse grinding, ie. the Output signal representing the difference of the residual material removal value from the standard value from the output terminal of the amplifier 49 to the servo control mechanism 15. The servomotor 7 thus drives the feed slide 6, with it maintains a constant residual material removal g at which the surface roughness of the workpiece tends to deteriorate which, however, contributes to high-efficiency material removal good cylindricity and roundness.

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After the rough grinding process step has been carried out, the workpiece diameter reaches the next switching point Pg at which the output of the detector 8 with that set in advance Value Pg matches. This coincidence signal from the Comparison circuit 5o changes the state of the selection circuit 44, so that the output signal of the amplifier 49 is cut off or interrupted and, on the other hand, the output signal of the third operation circuit 35 to the servo control mechanism 15 is supplied. On this designated in Figure 6 with Pg At this point, the material removal rate adjuster 33 is energized, as in the second Embodiment at point P took place. The servo motor 7 drives hence the feed carriage 6 along a predetermined material removal line from FIG. 6, the grinding wheel fine-grinding the workpiece.

When the workpiece diameter, as shown in FIG. 6, _{arrives at P 7} , the output signal of the detector 8 coincides with the previously established value Py. This coincidence signal, which is supplied from the comparison circuit 5o, switches the selection circuit 44, so that the output signal of the third operation circuit 35 is cut off and the two values set in advance of the regrinding state setting device 52 to the servo control mechanism 15 or the Drive device 43 are supplied. The servomotor 7 therefore drives the feed slide 6 at a feed speed V _F , while the direct current motor 42 sets the workpiece spindle 41 in rotation at a speed N ". This ensures that the grinding wheel carries out a finish or regrinding of the workpiece at a very low feed rate Vp.

When the workpiece diameter arrives at Pg, the output signal falls of the detector 8 together with the fixed value Pg. This coincidence signal supplied by the comparison circuit 5o switches the selection circuit 44 so that the input signals from the regrinding condition setting device 52

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switched off or interrupted while the direction of rotation of the servo motor 15 is reversed, so that the feed slide 6 performs a quick return and the work spindle speed is returned to the value it was before took.

In the embodiments described, it is preferred to avoid rattling or hitting during grinding The device is provided with a device which gives the workpiece spindle a random distribution in speed during fine grinding or regrinding.

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Claims (12)

Claims 1.) Grinding process, characterized by Lne speed control for material removal, at the material distance from a workpiece constant or intermittent measured during a grinding process and compared with predetermined program values for the material removal where the difference between the actual material distance and a program value is the feed rate of the tool with respect to the grinding tool moving feed slide controls in such a way that the difference is made to disappear will. 2. Grinding method according to claim 1, characterized in that that the tangential grinding force is determined and converted into a Signal is converted to the program value of the material removal switches to another lower program value when the value of this signal exceeds a predetermined value. 3. Grinding method according to claim 2, characterized in that that the tangential grinding force is determined by the electrical power consumption of the spindle motor, which the Sets the grinding tool in rotation. 4. Grinding method according to one of the preceding claims, characterized in that the speed control of the material removal takes place during fine grinding, the next to a Rough grinding is carried out. 5. Grinding method according to claim 4, characterized in that that the rough grinding is performed with a residual material removal control, the difference between the actual feed of the feed slide and the actual material distance regulated from a predetermined value will. 609811/0293 6. Grinding method according to claim 5, characterized in that that after the fine grinding, regrinding is carried out, this regrinding being controlled in such a way that the ratio the feed rate of the feed slide to the number of revolutions of the work spindle is kept constant. 7. Grinding machine, in particular for carrying out a method according to one of the preceding claims, characterized by a servomotor (7) for driving a feed slide (6) which displaces a grinding tool relative to a workpiece (W) by a servo control mechanism (15) for the servo motor (7), by a detector (8), which measures the workpiece diameter during the grinding process, by a clock pulse generator (11), by an operation circuit (9), which the speed with which the material removal of the workpiece takes place, determined from the diameter values, one of which from the detector (8) to a first clock pulse of the clock pulse generator (11) is determined and the other to a second, by an adjusting device (14), which for this purpose serves to set speed values for the material removal in advance, and through a differential amplifier (12), the a control signal for the servo control mechanism (15) from a speed value of the material removal of the adjustment device (14) and the actual material removal rate manufactures, formed by the operational circuit (9) proportional to the difference between these speeds is. 8. Grinding machine according to claim 7 »characterized by a power consumption detector (17) for a grinding wheel spindle motor, which drives a tool grinding the workpiece by a power consumption value setting device (18), which is used to set power consumption values in advance, and by means of a comparison circuit (19), which output signals delivers if the determined value for the power consumption corresponds to one of the values set in advance, wherein the output signals make a selection so that a predetermined speed value for the 609811/0 293 Material removal fed to the differential amplifier (12) will. 9. Grinding machine, in particular for performing a method according to one of claims 1 to 6, characterized by a servomotor (7) for driving a feed slide (6) which moves a workpiece relative to a grinding tool, by a servo control mechanism (15) for the servo motor (7), by a detector (8), which determines the workpiece diameter during the grinding process, by a Function generator that generates a standard material removal function curve according to a grinding process, and through a differential amplifier which generates a control signal for the servo control mechanism (15) from the actual diameter values of the workpiece and the corresponding value of the function curve. 10. Grinding machine according to claim 9 _f, characterized by an adjusting device which makes it possible to set values for the diameter of the workpiece in advance in order to change the control mode of the grinding feed, and by a comparison circuit for generating output signals when the determined workpiece diameter matches one of the coincide with predetermined values, the output signals selecting one of the grinding feed control modes including the speed control of material removal in the servo control mechanism (15). 11. Grinding machine according to claim 1o, characterized by a position detector (45) which determines the feed position of the feed slide (6) by a first operation circuit (46) for achieving a residual material removal, which is the material distance from the workpiece determined by the size detector the feed path for the actual grinding subtracted which is determined by the bE REDUCED detector (45), which sets by a standard residual material removal adjusting device (48) which default Restmaterialentfernun- gene for rough grinding, and, by a second operation circuit (47) which Output signals generated by the 609811/0293 Difference between the actual residual material removal obtained from the first operational circuit (46) and that of the setting device (48) corresponds to a predetermined standard value, these output signals from the second operation circuit be selected for rough grinding to get to the servo control mechanism and being a speed control the material removal for fine grinding is used after a predetermined workpiece diameter has been determined in order to switch to fine grinding. ; 12. Grinding machine according to claim 1o, characterized by a regrinding state setting device (52) which predetermines the feed speed (V _p ) of the feed slide (6) and the number of revolutions (N ^) of the workpiece suitable for an excellent regrinding of the surface, and by a Motor speed control, which changes the speed of the workpiece spindle motor, the values for regrinding predetermined on the regrinding state setting device (52) being selected so that they are fed to the servo control mechanism and the motor speed control after a predetermined workpiece diameter has been determined, while the speed control of the material removal is used for fine grinding. 6 09811/0293 Blank page