GB1570298A - Method of grinding and grinding machine for carrying out the method - Google Patents

Description

(54) A METHOD OF GRINDING AND GRINDING MACHINE FOR CARRYING OUT THE METHOD (71) We, FRITZ STUDER AG, a Swiss Body Corporate of Glockenthal, Thun, Switzerland, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- The invention relates to a method of grinding for use on machine-tools, particularly circular grinding machines, and to a grinding machine for carrying out the method.

Grinding methods are known in which the grinding wheel carries out the machining operation at a speed of revolution corresponding to the optimum peripheral- speed, and with a preselected depth of infeed which differs for various operations and at a preselected rate of advance which is constant for the various operations. In these methods, involving for example preliminary grinding or roughing operations, the rate of advance is kept relatively low when the depth of infeed is great, so as to reduce wear of the wheels to a minimum. In the following final grinding or finishing operation, a high rate of advance is used, accompanied by a small depth of infeed, so as to ensure a very accurate shape and a good surface finish.

The methods outlined above are at present carried out as separate operations so that a correspondingly lengthy period is required for performing the entire machining process.

If the preliminary grinding and the final grinding operations are carried out under the optimum conditions for preliminary grinding, a relatively rough surface results.

If the preliminary grinding and the final grinding operations are carried out under the optimum conditions for final grinding, very considerable wear on the wheels can be expected. This is the case particuiarly when a well-defined shape has to be' ground to close tolerances.

According to the present invention we provide a method of grinding for use on circular grinding machines, wherein, during a particular grinding operation the speed of movement of the workpiece is automatically varied as a function of a machining factor, such that initial infeed of the grinding wheel takes place while the workpiece repeatedly rotates åt relatively low speed and further infeed of the grinding wheel takes place while the workpiece rotates at relatively high speed.

Such a method enables one to reduce the time required for the entire machining of a workpiece and also to reduce the wear on grinding wheels to a minimum.

The invention also provides a grinding machine for grinding a workpiece, compnsl ing a grinding wheel, means for mounting and rotating the workpiece, and means for automatically varying the speed of revolution of the workpiece during the machining operation by means of-a control or regulating device, as a function of a machining factor such that in use initial infeed- of the grinding wheel takes place while the workpiece repeatedly rotates at relatively low speed and further infeed of the grinding wheel takes place while the workpiece rotates at relatively high speed, Machining factors may be one or more of rate of infeed, - infeed distancej amount of material removed, time - taken lot removing material, and the change in the size'of the workpiece.

The variation in speed of movement may be varied as a function of one or a number of machining factors. Suitable integrator eircuitry can be provided, if desired to select one. our more factos in preference to others.

In order that the invention wilL be more fully understood, the following, descriptiot is given, by way of example -only, reference being made. to the accompanying drawing, in which: Figure 1 shows diagrammatically a crosssection through one embpdiment of .drcular grinding 'mactine;--- during a preliminary grinding, and - - Figure 2 is ,, a, similar view of a circular grinding machining'during final grinding.

A grinding wheel 2 mounted in a grinding wheel holder 1 machines a workpiece 4 held in a workpiece holder 3. A transverse slide 7 which supports holder 1 is fed towards the workpiece 4 by means of a servomotor 5 and an adjusting element 6. In the preliminary grinding operation illustrated in Figure 1, the workpiece is ground over the relatively large infeed distance 8 while the workpiece 4 is being slowly rotated (symbolized by the short arrow).

The final grinding operation is illustrated in Figure 2. The speed of revolution of the workpiece 4 is increased - hy means of a control and regulating device 9 and a workpiece motor 10 (this increase being symbolised by the long arrow). In this case however the infeed distance 8 is reduced to a relatively small value. After this combined preliminary and final grinding operation has been carried out, the transverse slide 7 is returned to its initial position, and the workpiece 4 is changed. By displacing the longitudinal slide 11 on the machine bed 12, it is also possible to bring the same workpiece 4 into a position where a different diameter is to be machined, and then to proceed with machining.

By continuously adapting the rate of advance to suit the depth of infeed, a preliminary grinding operation can be directly combined with the final grinding operation, and this greatly reduces the machining time. A side-effect of operating while using optimum cutting movements that is achieved both during preliminary grinding and final grinding is that the normally heavy wear on the wheels is reduced. Thus, all workpieces can be machined with satisfactory accuracy, and a smaller number of truing operations is required. This in turn enables the grinding wheel to be utilised in a better manner.

WHAT WE CLAIM IS: 1. A method of grinding for use on circular grinding machines, wherein, during a particular grinding operation, the speed of movement of the workpiece is automatically varied as a function of a machining factor, such that initial infeed of the grinding wheel takes place while the workpiece repeatedly rotates at relatively low speed and further infeed of the grinding wheel takes place while the workpiece rotates at a relatively high speed.

2. A method according to claim 1, wherein the speed of movement of the workpiece is varied as a function of the rate of infeed.

3. A method according to claim 1 or 2, wherein the speed of movement of the workpiece is varied as a function of the infeed displacement of the grinding wheel.

4. A method according to claim 1, 2 or 3, wherein the speed of movement of the workpiece is varied as a function of the amount of material removed from the workpiece.

5. A method according to any preceding claim, wherein the speed of movement of the workpiece is varied as a function of the desired time for- the removal of material from the workpiece.

6. A method according to any preceding claim, wherein the speed of movement of the workpiece is varied as a function of the change in the size of the workpiece.

7. A grinding -machine for grinding a workpiece, comprising a grinding wheel, means for mounting and rotating the workpiece, and means for automatically varying the speed of revolution of the workpiece during the machining operation by means of a control or regulating device, as a function of a machining factor such that in use initial infeed of the grinding wheel takes place while the workpiece repeatedly rotates at relatively low speed and further infeed of the grinding wheel takes place while the workpiece rotates at relatively high speed.

8. A grinding machine according to claim 7, wherein the speed of revolution of the workpiece can be varied during the machining operation by means of a control or regulating device, as a function of the rate of infeed of the grinding wheel relative to the workpiece.

9. A grinding machine according to claim 7 or 8, wherein the speed of revolution of the workpiece can be varied during the machining operation as a function of the infeed displacement of the grinding wheel relative to the workpiece.

10. A grinding machine according to claim 7, 8 or 9, wherein the speed of revolution of the workpiece can be varied during the machining operation, as a function of the desired time for removal of material from the workpiece.

11. A grinding machine according to claim 7, 8, 9 or 10, wherein the speed of revolution of the workpiece can be varied during the machining operation, as a function of the change in the diameter of the workpiece.

12. A method of grinding substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

13. A grinding machine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (13)

**WARNING** start of CLMS field may overlap end of DESC **. A grinding wheel 2 mounted in a grinding wheel holder 1 machines a workpiece 4 held in a workpiece holder 3. A transverse slide 7 which supports holder 1 is fed towards the workpiece 4 by means of a servomotor 5 and an adjusting element 6. In the preliminary grinding operation illustrated in Figure 1, the workpiece is ground over the relatively large infeed distance 8 while the workpiece 4 is being slowly rotated (symbolized by the short arrow). The final grinding operation is illustrated in Figure 2. The speed of revolution of the workpiece 4 is increased - hy means of a control and regulating device 9 and a workpiece motor 10 (this increase being symbolised by the long arrow). In this case however the infeed distance 8 is reduced to a relatively small value. After this combined preliminary and final grinding operation has been carried out, the transverse slide 7 is returned to its initial position, and the workpiece 4 is changed. By displacing the longitudinal slide 11 on the machine bed 12, it is also possible to bring the same workpiece 4 into a position where a different diameter is to be machined, and then to proceed with machining. By continuously adapting the rate of advance to suit the depth of infeed, a preliminary grinding operation can be directly combined with the final grinding operation, and this greatly reduces the machining time. A side-effect of operating while using optimum cutting movements that is achieved both during preliminary grinding and final grinding is that the normally heavy wear on the wheels is reduced. Thus, all workpieces can be machined with satisfactory accuracy, and a smaller number of truing operations is required. This in turn enables the grinding wheel to be utilised in a better manner. WHAT WE CLAIM IS:

1. A method of grinding for use on circular grinding machines, wherein, during a particular grinding operation, the speed of movement of the workpiece is automatically varied as a function of a machining factor, such that initial infeed of the grinding wheel takes place while the workpiece repeatedly rotates at relatively low speed and further infeed of the grinding wheel takes place while the workpiece rotates at a relatively high speed.

2. A method according to claim 1, wherein the speed of movement of the workpiece is varied as a function of the rate of infeed.

3. A method according to claim 1 or 2, wherein the speed of movement of the workpiece is varied as a function of the infeed displacement of the grinding wheel.

4. A method according to claim 1, 2 or 3, wherein the speed of movement of the workpiece is varied as a function of the amount of material removed from the workpiece.

5. A method according to any preceding claim, wherein the speed of movement of the workpiece is varied as a function of the desired time for- the removal of material from the workpiece.

6. A method according to any preceding claim, wherein the speed of movement of the workpiece is varied as a function of the change in the size of the workpiece.

7. A grinding -machine for grinding a workpiece, comprising a grinding wheel, means for mounting and rotating the workpiece, and means for automatically varying the speed of revolution of the workpiece during the machining operation by means of a control or regulating device, as a function of a machining factor such that in use initial infeed of the grinding wheel takes place while the workpiece repeatedly rotates at relatively low speed and further infeed of the grinding wheel takes place while the workpiece rotates at relatively high speed.

8. A grinding machine according to claim 7, wherein the speed of revolution of the workpiece can be varied during the machining operation by means of a control or regulating device, as a function of the rate of infeed of the grinding wheel relative to the workpiece.

9. A grinding machine according to claim 7 or 8, wherein the speed of revolution of the workpiece can be varied during the machining operation as a function of the infeed displacement of the grinding wheel relative to the workpiece.

10. A grinding machine according to claim 7, 8 or 9, wherein the speed of revolution of the workpiece can be varied during the machining operation, as a function of the desired time for removal of material from the workpiece.

11. A grinding machine according to claim 7, 8, 9 or 10, wherein the speed of revolution of the workpiece can be varied during the machining operation, as a function of the change in the diameter of the workpiece.

12. A method of grinding substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.

13. A grinding machine substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.