RU2418670C2 - Method of round grinding with application of ultrasound oscillations - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to machine building and may be used in grinding work pieces like bearings races, sleeves etc. Prior to grinding, the workpiece is arranged on arbor for FM ultrasound oscillations to be applied to the former. Because of said oscillations imparted to workpiece in grinding, cutting forces, contact and local temperature in zone of contact between abrasive grains and workpiece are reduced. Grinding over, workpiece and aforesaid device are removed from machine tool for workpiece to be subjected to ultrasound effects outside grinding zone. This allows removing residual stresses in workpiece surface areas and increasing efficiency since, at the time, another workpiece is ground.

EFFECT: grinding wheel longer life, higher processing efficiency.

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Description

The invention relates to mechanical engineering, namely to processing by round external grinding of workpieces such as rings of bearings, bushings.

There is a method of ultrasonic stabilization of residual stresses (see. Babenko MG. Improving the technology to ensure dimensional accuracy of precision parts such as bearing rings based on the use of ultrasonic stabilization of internal stresses. Abstract of thesis ... Candidate of Technical Sciences: 05.02.08 / Saratov State. technical university - Saratov, 2002. - 16 p.), in which after grinding the parts through the polished surface, ultrasonic vibrations (ultrasonic vibrations) of a certain amplitude and frequency are reported.

The reasons that impede the achievement of the technical result indicated below when using the known method include the absence of the influence of ultrasound energy on the grinding process of the workpieces, as well as an increase in the manufacturing cycle of the part due to the inclusion of time for ultrasonic stabilization of residual stresses. In the process of grinding and relieving residual stresses, various technological equipment is used. In addition, the drawback is the involvement of a relatively small number of dislocations in the process of dislocation absorption of ultrasound energy, the sizes of which lie in a narrow range, since the frequency dependence of the dislocation absorption is resonant in nature, and the intrinsic resonance frequency of the dislocation is determined by the length of the dislocation segment (see Ultrasound. Small Encyclopedia / Under the general editorship of I.P. Golyamina. - M .: Soviet Encyclopedia, 1979. - 400 p.). This drawback is due to the fact that in the specified method, ultrasonic testing of a certain fixed frequency is used. As a result, the efficiency of removing technological residual stresses is small.

The closest to the claimed invention in terms of features is the grinding method selected as a prototype, which consists in the continuous application of ultrasonic vibrations to the workpiece during grinding (see Pat. No. 2276004, C1, publ. 2006.05.10 Bull. No. 13, RU, main IPC index B24B 1/04 (2006.01) “Grinding method”).

The reasons that impede the achievement of the technical result indicated below when using the known method adopted for the prototype include the fact that in the known method, ultrasonic testing does not significantly affect the grinding process, since there is a local contact area of the tool to relieve residual stresses and the workpiece, and UZK are distributed on the limited volume of preparation.

The invention consists in the following. In the grinding process, the cutting ability of the grinding wheel is gradually reduced, which leads to the need for a corresponding decrease in the performance of defect-free grinding or (and) to a deterioration in the quality of the polished parts. One way to improve the grinding efficiency of workpieces from various materials is to apply ultrasonic testing in the grinding process, in this case, to the workpiece. The application of ultrasonic testing allows to reduce the friction coefficient in the contact zone of the circle - workpiece, cutting forces, contact and local temperatures, which leads to the preservation of the cutting ability of abrasive grain (AZ), and therefore, it is possible to increase processing productivity and the period of resistance of the circle. In addition, during grinding in the surface layer of the workpiece, in most cases, tensile residual stresses are formed that adversely affect the performance of the product. One way to relieve residual stresses is to apply ultrasonic testing. In this case, the application of ultrasonic testing on the workpiece occurs both during grinding and after it is finished and the workpiece is removed, along with the mandrel, which allows to impose vibrations from the machine on the workpiece. It is possible to process the next workpiece on the machine. There is no need to install - remove the workpiece in the second fixture, since one fixture is used. This provides an increase in processing productivity and the efficiency of removing residual stresses.

The technical result is an increase in the durability of the grinding wheel and processing performance while ensuring the specified quality of the polished parts.

The specified technical result in the implementation of the method of circular external grinding with the application of ultrasonic vibrations includes the application of ultrasonic vibrations to the workpiece in the grinding process.

The peculiarity lies in the fact that before grinding, the workpiece is mounted on a mandrel, which allows you to apply vibrations to the workpiece, and ultrasonic vibrations are superimposed on the workpiece not only during grinding, but also after this process is completed and the workpiece with the mandrel removed from the machine.

Due to the ultrasonic vibrations transmitted to the workpiece during grinding, the cutting forces, contact and local temperatures in the contact zone of AZ with the workpiece are reduced. Reducing local temperatures in the contact zone of AZ with the workpiece allows to improve the quality of the polished parts and to reduce the mass of metal adhering to the grains of the wheel, thereby increasing the durability of the grinding wheel and grinding performance. With a change in frequency, the wavelength changes, and the location of the vibration nodes will be unstable, therefore, the application of frequency-modulated ultrasonic vibrations to the workpiece ensures that all sections of the surface layer of the workpiece oscillate. The extended period of application of frequency-modulated ultrasonic vibrations to the workpiece allows maximum removal of residual stresses from the workpiece and improves the operational characteristics of the part. This is ensured by the fact that after processing by grinding the workpiece together with the mandrel is removed from the machine and frequency-modulated ultrasonic vibrations continue to be applied to it outside the processing zone, thereby increasing the efficiency of removing residual stresses in the surface layers of the workpiece, and at the same time on the machine the next workpiece is processed. There is also no need to install and remove the workpiece in various devices. To communicate to the polished workpiece of ultrasonic vibrations of a frequency-modulated shape, an electric signal modulated in frequency is used, which can be obtained using an ultrasonic generator (USG).

The drawing shows a diagram of a mandrel for implementing the method of circular external grinding with the imposition of ultrasonic testing.

The mandrel contains a mandrel-emitter 1, the housing 2, the workpiece 3, the piezoelectric transducers 4, a reflecting nut 5, brushes 6, an arm 7, current collectors 8.

The blanks 3 are installed on the mandrel-emitter 1, press the reflective nut 5 to the end of the mandrel-emitter 1. The mandrel for the implementation of this method is installed in the center of the machine, after having put on the mandrel a lead. Elastic mechanical vibrations, modulated in frequency, are communicated to the workpieces 3 through the emitter mandrel 1 generated from electric vibrations of the ultrasonic frequency using piezoelectric transducers 4. The electric vibrations communicated by the ultrasonic generator are transmitted to the piezoelectric transducers 5 using brushes 6 and current collectors 8. After that, the preforms 3, rotation through the leash is communicated, and grinding is carried out. The housing 2 remains stationary due to the bracket 7, attached to the table of the machine. This solution allows the application of frequency-modulated oscillations on the workpiece without complicating the grinding process. The application of frequency-modulated ultrasonic vibrations to the workpiece ensures that all sections of the surface layer of the workpiece 3 oscillate.

Thus, the workpieces 3 are communicated with frequency-modulated ultrasonic vibrations, which leads to a decrease in cutting forces, local temperatures, friction coefficient AZ with the workpiece 3 and a decrease in the residual stresses arising during grinding.

After processing by grinding, the workpiece 3 together with the mandrel is removed from the machine and frequency-modulated ultrasonic vibrations continue to be applied to it outside the processing zone in order to relax the residual stresses in the surface layer of the workpiece 3.

Claims (1)

A method of processing workpieces with superimposed ultrasonic vibrations (ultrasonic testing), including installing the workpiece on a mandrel for applying ultrasonic testing, round external grinding of the workpiece on the machine and removing the workpiece with the said mandrel from the machine, with the ultrasound being continuously applied to the workpiece during grinding and after its completion and removal from the machine workpiece with a mandrel for applying ultrasonic testing.