SU764943A1 - Method of abrasive lapping of parts - Google Patents

Description

one

The invention relates to abrasive machining and can be used for highly efficient machining of ceramic, hard alloy, quartz, ruby, glass and other parts.

There is a known method of fine-tuning holes, at which the external pressure is changed with a frequency from 100 to 1000.

The disadvantages of this method of refinement are the relatively small expansion of the high-frequency part of the spectrum of the abrasive friction force and the absence of frequencies in the spectrum, which intensify the development of fracture microcracks deep into the material.

The purpose of the invention is to increase the productivity of the finishing process and improve the quality of the surface to be treated.

This is achieved by performing a smooth sweep of the frequency of change in external pressure. The lower limit of the frequency of the external pressure is determined from the condition:

“Ax mime

.min

V

where v

max and min

the maximum values of the speed of movement of any part of the dedal by lapping, respectively; and - abrasive grain;

K is the proportionality coefficient.

In addition, during roughing, the external pressure is additionally changed with a constant frequency f, while f, (Finishing is carried out outside the frequency range from 0

15 to 30 Hz.

Claims (4)

FIG. Figure 1 shows the frequency spectrum of the abrasive friction force in the case of a change in external pressure with a constant frequency and movement of the preparation section at a constant speed; 2 - frequency spectrum of the abrasive friction force in the case of a smooth sweep of the frequency of change in external pressure; in fig. 3 - frequency spectrum of the power of abrasive friction of the proposed method during roughing; Fig. 4 30 is a functional diagram of a pressure control system that implements the proposed refinement method. Spectral analysis of the forces arising in the process of abrasive finishing shows that if a part that moves on ground with a relative speed V is acted upon by a variable pressure (from priter or holder) of the type R + PDax, then in the frequency spectrum of the Dnormal and tangential forces there are three groups constants to cix: component with zero frequency, with frequency f, and a group of components with frequencies (see Fig. 1). fo-f-i. Frequency f ,. is generated by the movement of the part on the lap and is defined as. to-. - “a NB„ „+ HB. Pry a - the diameter of the abrasive grain; K - coefficient of proportionality; HB.g, HB „p. - Brinell hardness of the material of the part and priter, respectively. When the surface element of the workpiece moves at a variable speed, the spectrum of abrasive friction forces contains frequencies from G "„ „L K to f.," H (where SGM and VAIUU are the maximum and speed values of the element surface speed relative to abrasive grains , respectively. When pr (which is true for most cases) Umr, / min can be taken equal to the corresponding values of the velocities of the surface element of the part, relative to pritir. If the frequency of change in external pressure is less than the value of f - jmax FMHH then the frequency bandwidth does not occur. The best result can be achieved if the pressure is variable with a variable frequency, and the smallest frequency (with a sufficiently large acceleration of the relative motion of the part along the lap) is chosen from the condition MikHi max min (Fig. 2). The highest value of the frequency of pressure changes is determined empirically, when a further increase in the upper frequency limit does not lead to a significant improvement in the frequency of the surface of the workpiece. When treating fragile materials, the microtreatment fracture troughs define a value that has a low frequency part of the spectrum from 0 to 30 g. Therefore, when roughing, along with the increased width of the high frequency part of the spectrum, abrasive friction (pressure) creates a regular low frequency component 0.2 - 30 Hz (see Fig. 3), depending on the material of the part and the quality of the surface after the technological operation, prior to the process of abrasive finishing. For finishing, in order to obtain the minimum defective layer, they work outside the frequency range from 0 to 30 Hz, i.e. in this area stabilize the strength of the abrasive friction (pressure). The pressure control system, which implements the proposed method of abrasive finishing (see Fig. 4), has a finishing machine 1 with abrasive friction force sensors 2 installed on it, the output of the last through amplifier 3 is connected to a stabilization circuit 4, which, in cBOfo, is connected through the switching unit 5 with the pressure control circuit 6. The output of the generator 7 pulses and the output of the time sensor 8 are also connected to the input of the switching unit 5. The second input of the pressure control circuit is connected to the output of the pulse generator 9, the input of which, in turn, is connected to the output of the sawtooth voltage generator 10. The control system operates as follows. The sawtooth voltage supplied by the saw generator 10 continuously changes the frequency of the pulse generator 9 from f to f, where f and f are the smallest ii the highest generator frequency values determined by the initial and final saw voltage values. The variable frequency voltage is supplied to a pressure control circuit b, which performs a pressure change with the same frequency. When the rough adjustment, the pressure control circuit 6 also receives pulses of constant frequency from the generator 7 of pulses through the switching unit 5. When finishing the finishing, the control signal 5 from the switching unit 5 is supplied with a control signal from the stabilization circuit 4 generated based on a comparison of the signal from the sensor 2 of the abrasive friction force amplified by the amplifier 3. and a constant voltage setting the pressure level set in the stabilizer 4. Switching unit 5 is controlled by time sensor 8. The proposed method allows to increase the productivity and quality of the finishing parts. Claims 1. A method of abrasive finishing of parts, at which an external pressure is changed, characterized in that, in order to increase the productivity and quality of processing, a smooth swing of a change in external pressure is realized. 2. The method according to claim 1, is also distinguished by the fact that the lower boundaries of the external pressure frequency are determined from the condition: MSTX (LMM MII OS where V aiij; maximal and minimal values of the speed of movement of any part of the part by lapping, respectively; a - abrasive grit; k - coefficient of proportionality. 3. The method according to claim 1 and 2, characterized in that during the rough finishing, the external pressure is additionally changed with a constant frequency f, while f "f min 4. Method according to paragraphs. 1 and 2, that is, that the fine tuning is carried out outside the frequency range from 0 to 30 Hz. Sources of information taken into account in the examination 1. USSR author's certificate 138155, cl. B 24 B 1/00, 1961. -.R./,  .four fi il 0 f) / I T V; r H Y / x / 0- / I / o / - / ftnin-ft w / MWMr ftmn-ff  Aww / ikfMtne fi