RU2365482C2 - Method for precision grinding of electric spindle shaft - Google Patents

Abstract

FIELD: technological processes, metal working.

SUBSTANCE: invention is related to the field of precision machine building and may be used in manufacturing of electric spindle shafts at round-grinding lathes. Shaft is installed in centres of round-grinding lathes. Rotation is imparted to it by means of lead with yoke fixed on shaft. In process of final grinding, alternate grinding of front and back journals of electric spindle shaft is carried out with its shift. Prior to final grinding of back journal yoke is fixed at finally ground front journal of electric spindle shaft in the area, where deformation of central shaft opening is not available from yoke effect, with provision of striking of electric spindle shaft front journal that does not exceed 0.002 mm.

EFFECT: higher accuracy of external surface shape in electric spindle shaft.

14 dwg

Description

The invention relates to the field of precision engineering and can be used in all areas where the manufacture of bodies of revolution during circular grinding on circular grinding machines. The high accuracy of the circumference of the outer diameter during round grinding of the shaft of the electrospindle and pneumatic spindle becomes a source of information, creating the possibility of obtaining a stable result.

The solution of technical problems goes into information technology, which allows you to organize technical solutions at a higher level, providing a further increase in the economic efficiency of products and improvement of technological processes in the manufacture of bodies of revolution.

A technical solution is known in which a method of grinding a body of revolution, in particular a shaft, is disclosed, including installing the shaft in the centers of a circular grinding machine, telling it to rotate by means of a leash with a collar fixed to the shaft, and grinding it (see P. Lizard and others. Metal Grinding, Minsk, BELARUS Publishing House, 1963, p. 84-89).

The disadvantage of this method is the low accuracy of the shaft processing due to deformation of its center hole when fixing the clamp.

The technical result of the invention is to improve the accuracy of the shape of the outer surface of the shaft of the electrospindle and processing efficiency.

The specified technical result is achieved by the fact that the shaft of the electrospindle is installed in the centers of the circular grinding machine, it is informed of the rotation by means of a leash with a collar attached to the shaft, and the front and rear necks of the spindle shaft are alternately final grinded with its rearrangement, and the clamp is fixed before final grinding of the rear neck on the finally polished front neck of the electrospindle shaft in a place where there is no deformation of the center hole of the shaft due to the clamp, with the beating of the front neck of the spindle shaft, not exceeding 0.002 mm.

The result is achieved as follows.

1. By investigating the causes associated with obtaining high accuracy of the circumference of the outer diameter of the ground body, measured in tenths of a micrometer 0.2-0.5 (0.0002-0.0005 mm), and the reasons that impede the receipt of this accuracy.

2. The use of high-precision indicator measuring instruments with a division price of 0.0005 mm and 0.001 mm.

3. The use of constructive solutions for the pneumatic spindle A 30/100, which become a reference point for obtaining a stable result during round grinding of the outer surface of the shaft due to the absence of deformation of the center hole of the Technological Installation Base (TUB) during grinding.

4. Using a constructive solution with respect to the AC 72 / 0.25 pneumatic spindle shaft, which allows fixing the deformation that arose from the compression force when fixing the clamp on the shaft, which led to the search for a solution to get out of this situation.

In the course of patent research on scientific, technical and patent literature, no sources similar to the one proposed were found. In accordance with the foregoing, we can conclude that it meets the conditions of "novelty" and "inventive step".

The invention is presented in the drawings, where:

- figure 1 shows the grinding process of the shaft of the pneumatic spindle A 30/100;

- figure 2 is a section along BB of figure 1;

- figure 3 - the grinding process of the shaft of the pneumatic spindle AC 72 / 0.25;

- figure 4 is a section along BB of figure 3;

- figure 5 - the grinding process of the shaft of the pneumatic spindle AC 72 / 0.25 with the installation of the clamp in another place on the shaft;

- in Fig.6 - the process of measuring the runout of the shaft AC 72 / 0.25 in the centers of the machine in the process of circular grinding;

- Fig.7 - the grinding process of the shaft of the electric spindle ШК 36 / 1,5;

- Fig. 8 shows the grinding process of the electric spindle shaft ШК 36 / 1,5 after rearrangement;

- figure 9 is a section along BB of Fig; 8;

- figure 10 - the grinding process of the front neck of the shaft of the electric spindle ШК 36 / 1,5;

- figure 11 is a grinding process of the rear neck of the shaft of the electrospindle ShK 36 / 1,5;

- Fig.12 is a circular diagram of the inner hole of the shaft AC 72 / 0.25;

- Fig.13 is a circular diagram of the deformed inner bore of the shaft AC 72 / 0.25;

- on Fig - two roundograms superimposed on each other.

The production (manufacturing) of electric spindles and pneumatic spindles in precision engineering occupies a special place and has its own niche. The electrospindle and pneumatic spindle belong to the means of production and are themselves the production of means of production.

The rotational speed of the shaft of the electrospindle and pneumatic spindle is calculated in tens of thousands of revolutions per minute. Three-phase high frequency current up to 2500 hertz provides the ability to obtain rotation speeds up to 150,000 rpm. The speed of rotation of the pneumatic spindle is provided by the turbine, which is located on the shaft of the pneumatic spindle.

The requirements for a shaft rotating at such a high speed are very stringent. The tolerance on the outer mounting dimensions of the shaft necks is expressed by the size of the tolerance of 0.002-0.003 mm (2-3 microns) and does not depend on the diameter of the shaft neck, from 8 mm to 50 mm, the tolerance is one (single), 1-2 accuracy by ESDP. Tolerance for tapering, parallelism is expressed by a value from 0.0006-0.0015 mm. Deviations from roundness (non-circularity) are expressed as 0.0005-0.0012 mm.

Precision engineering places high demands on the manufacture of parts.

High accuracy makes high demands on creating the conditions for fulfilling the task, which become a source of information.

The Experimental Research Institute of Metal Cutting Machines (ENIMS), developed a spindle in which there were no rolling bearings, the so-called pneumatic spindles.

Rolling bearings are replaced by graphite bearings. The method of operation of such a bearing is as follows: compressed air, free of moisture and oil, is supplied into the gap between the shaft and the graphite bearing, which keeps the shaft suspended. The rotation speed of the pneumatic spindle shaft can range from 20,000 rpm to 250,000 rpm. The shaft, which rotates at such a high speed, has increased demands on the shape of the outer diameter of the shaft surface. The non-circular shape of the outer diameter of the shaft surface shall not exceed 0.0005 mm. The design features of the shafts of the pneumatic spindles required special attention to the TUB.

The grinding process of the shaft A 30/100 is shown in figure 1 where: A is the base surface, 1 is the shaft during grinding, which is located between the centers 3 and 4, the grinding wheel 2, the grinding shaft is moved by the hydraulic system of the machine. The plate of the front headstock 5, on which the leash 6 is mounted, transmitting the rotation of the front headstock to the shaft 1, using a bolt 7 and a clamp 8. The bolt 7 is in contact with the surface of the flats 9 for the key.

Figure 2 shows a section along BB-1 of figure 1, where the plane of the surface of the flats 9 serves as the fulcrum of the bolt 7 of the clamp 8.

The pneumatic spindle shaft A 30/100 (the shaft rotates at a speed of 30000-100000 rpm) has a key flange, which is used by the grinder to fix the clamp on the shaft, with which rotation from the front headstock of the machine is transmitted to the pneumatic spindle shaft. The flank for the key turned out to be an auxiliary element during the round grinding, which was used by the grinder, it created conditions under which the center holes of the TUB were not subjected to deformation during the process of precision grinding. The absence of deformation created a unity of basing, in which the center openings of the TUB were in a straight line. The absence of TUB deformation allowed the grinder to obtain high accuracy of the shape of the outer diameter of the shaft surface, up to 0.0005 mm.

The technological installation base created on the device for internal grinding (patent No. 2287420) allows grinding the shaft A 30/100 on a circular grinding machine along the outer diameter with a non-circular tolerance of up to 0.0005 mm. Grinding was done on a Jones-Shipman machine tool. Model 1305 EIT (Jones-Shipman).

During circular grinding of the AC 72 / 0.25 pneumatic spindle shaft, the parameter for non-circularity of the shaft diameter was not maintained. According to the drawing, the permissible shaft non-circularity is up to 0.0005 mm. During the final round grinding, the non-circularity was obtained more than 0.001 mm. Repeated grinding of the TUB did not increase the accuracy.

Figure 3 shows the grinding process of the base surface A of the shaft AC 72 / 0.25. Shaft 1 is located between centers 3 and 4.

To transfer the rotation of the part in the centers of the machine, a clamp is used, which is fixed with a bolt or screw on the shaft.

The clamping force, which creates a bolt when fixing the clamp on the shaft, deforms the shaft at the point of application of force. The inner hole of the shaft allows you to measure the magnitude of the deformation of the caliper on the inner diameter of the hole. The magnitude of the deformation of the hole shows the magnitude of the deformation of the center hole, since they are mating surfaces. The runout of the shaft in the centers of the machine without a clamp does not exceed 0.002 mm. The runout of the shaft with a fixed clamp increases by 0.001-0.003 mm. The internal shaft hole at the compression points decreases by 0.015-0.025 mm, and at points located at an angle of 90 ° it increases by 0.010-0.015 mm. A cylindrical hole under the compression force changes shape and takes the form of an ellipse, therefore, the center hole also takes the form of an ellipse. A shaft with a deformed TUB when installed in the centers of the machine shows an increase in the runout of the shaft surface by only 0.001-0.003 mm. The paradoxical case is that the inner cylindrical surface took the form of an ellipse and the TUB, conjugated with the cylindrical surface, undergoes a similar change, and the runout in the centers changes very slightly by 0.001-0.003 mm. The shape of the inner hole has changed, the hole has acquired the shape of an ellipse by a value from 0.025-0.040 mm, and the amount of runout has increased by 0.001-0.003 mm.

In Fig. 4, a section along BB-B of Fig. 3 shows the place of attachment of the collar deforming the shaft, and the internal hole of the shaft, by which the strain value can be fixed.

Deformed TUB slightly increases the runout of the shaft in the centers of the machine, but prevents a stable result when grinding the outer surface of the shaft. The deformed TUB takes the form of an ellipse, the contact points of the part with the centers of the machine change the position of the part little, but the vertices of the deformed TUB have intermittent (point) contact with the surface of the center of the machine, and this is the reason for instability during circular grinding.

Having ascertained the cause of instability, we transfer the clamp to another shaft diameter, more distant from the center hole, and check the effect of the clamp fixing force on the change in the shape of the center hole. Figure 5 shows the mounting location of the clamp, which when attached does not deform the center hole of the TUBE. The inner diameter of the shaft at the interface with the center hole has not changed. The runout of the shaft in the centers of the machine without a clamp and with a fixed clamp has not changed.

The round grinding process has become stable, the non-circularity of the outer surface of the shaft does not exceed 0.0005 microns.

Figure 6 fixes a method for checking the occurrence of the moment of changing the shape of the center hole when fixing the clamp at point I and the measuring point of the runout. When fixing the clamp at point II, there is no increase in runout on the shaft surface.

A positive result is used and is used to improve grinding technology.

The electrospindle shaft has two necks for rolling bearings. Grinding of shaft necks is made alternately, with a permutation of a shaft. The clamp is mounted on the shaft at one end of the shaft, and the shaft neck is grinded at the other end of the shaft. The front shaft journal is finally ground first. The clamp clamping force does not deform the tube. The grinding process of the front neck of the shaft occurs in favorable conditions (Fig.7). After rearranging the shaft (Fig. 8), the fixed collar deforms the TUB at the front headstock, and grinding is performed at the tailstock of the grinding machine. Grinding occurs on that section of the shaft where there is no change in the TUB. Grinding is carried out at a great distance from the deformed TUB, and this circumstance allows to obtain high precision polished surface.

There is a violation of the unity of basing, but this moment remains unrecorded.

The design of the shaft of the electric spindle provides a hole for fixing the mandrel with a cutting tool. The center hole on this side has an increased diameter, which creates conditions for the deformation of the center hole.

In Fig.9 a section along BB of Fig.8 at the attachment point of the clamp, which creates a force and changes the shape of the center hole.

Figure 10 illustrates the grinding process of the front neck of the shaft ШК 36 / 1,5.

The grinding of the spindle shaft necks is carried out with a permutation, which leads to the case when the front shaft neck is ground with an undeformed TUB, since the center hole at the clamp point of the clamp on the opposite end of the shaft has a center hole diameter of 6 mm and the clamp clamp forces do not deform the TUB.

11 illustrates the grinding process of the rear journal of the shaft SHK 36 / 1,5. The finally polished surface of the front neck of the shaft allows you to check the accuracy of the installation of the part before final grinding of the rear neck of the shaft. Point I is the mounting location of the clamp. Point II - the final grinding of the surface of the rear neck of the shaft. Point III - the place to check the runout of the finally polished front shaft journal.

Grinding of the other shaft neck after rearrangement takes place under adverse conditions. The clamp clamping force on the shaft deforms the shaft and TUB deforms at the same time.

Check indicator shows an increase in the runout of the neck of the shaft. Additional runout indicates misalignment of the necks of the spindle shaft relative to each other. Minor misalignment occurs over the entire length of the shaft, and therefore remains unnoticed, difficult to identify. The resulting misalignment of the necks of the electrospindle shaft by an insignificant amount of 0.001-0.003 mm at high speeds, expressed by tens of thousands of revolutions per minute, increases the vibration of the working electrospindle, which reduces the cleanliness of the polished surface and at the same time reduces the working life of the electrospindle bearings.

The magnitude of the error is very small, and therefore it is not detected. The error occurs over the entire length of the shaft of the electrospindle during grinding, and a check in the centers on the PB-500 occurs on the section from the center hole to the end of the shaft neck, which does not allow to detect such a small error.

Claims (1)

The method of precision grinding of the electrospindle shaft, including installing the shaft in the centers of the circular grinding machine, telling it to rotate by means of a leash with a clamp fixed to the shaft, and grinding it, characterized in that during the final grinding, the front and rear necks of the electrospindle shaft are alternately ground with its rearrangement and, before final grinding of the rear neck, the clamp is fixed on the finally polished front neck of the electrospindle shaft in the place where exists centering shaft hole deformation on impact clamp, ensuring heartbeat front shaft journal electrospindle not exceeding 0.002 mm.

Images