RU2344921C1 - Method for honing of blind holes - Google Patents

Abstract

FIELD: technological processes; mechanical engineering.

SUBSTANCE: rotary and axial reciprocal motions are imparted to honing bars, and speed of bar rotary motion speed is changed. Speed is increased at their every axial travel from reversing point at the open edge of hole to reversing point at its bottom and is reduced, when honing heads travel in reverse direction.

EFFECT: higher accuracy and efficiency of processing due to increase of stock removal at the bottom of processed hole.

5 dwg, 1 ex

Description

The invention relates to finishing and can be used in the treatment of limited surfaces.

A known method of honing, in which the honing bars inform rotational and reciprocating motion (Honing. Reference. Manual. / Under the general editorship of S.I. Kulikov. - M.: Mechanical Engineering, 1973. - 168 S.).

However, with this method of honing, the absence of run-out over the edge of the hole from the side of its bottom while reducing the cutting speed due to the reverse of the translational movement of the honing head (where the axial velocity of the bars is zero) leads to a reduction in the stock removal in this section and the formation of the taper of the hole.

There is a method of honing blind holes, in which, in order to increase the removal of the allowance at the bottom of the hole, the processing is performed with trapezoidal bars, the larger base of the trapezoid facing the bottom of the hole being machined (Questions of calculating and designing equipment that improves accuracy during honing. Proceedings of UAI, issue 44 - Ufa, 1973, 159 p.).

The disadvantages of this method is that, firstly, the domestic industry does not produce bars of this form, and secondly, increased wear of the bars from the side of the larger base of the trapezoid.

There is also a known method of honing, which consists in increasing the reverse time of the translational movement of the honing head at the bottom of the hole to be machined (Kudoyarov R.G. Precision of machine parts during diamond honing. / Ed. By Doctor of Technical Sciences, Professor V.Ts. Zoriktuev . - M.: Publishing House of the Moscow Aviation Institute, 2002. - 170 p.).

The disadvantage of this method of honing is to increase the processing time due to the delay of the bars at the bottom of the hole and, therefore, to reduce the performance of honing.

The closest technical solution to the claimed one is the method of honing, in which the honing bars are informed of rotational and reciprocating movements, and the speed of rotational motion is changed during processing (Honing. Reference manual. / Under the general editorship of S.I. Kulikov. - M .: Mashinostroenie, 1973. - 168 p.) By superimposing on the rotational movement of the spindle of the machine circular harmonic (sinusoidal) vibrations.

However, this method of honing also does not prevent the formation of tapering when processing blind holes.

The objective of the present invention is to improve the accuracy and productivity of processing by increasing the removal of stock at the bottom of the hole being machined.

This task is achieved by the method of honing blind holes, in which the honing bars are given rotational and reciprocating movements, and the rotational speed is changed during processing, in contrast to the prototype, the rotational speed of the bars is increased with each axial movement of the bars from the reverse point at the open edge of the hole to the reverse point at the bottom of the hole being machined and reduce this speed when they move in the opposite direction.

With an increase in the speed of rotational movement for the same time interval, each cutting grain of the honing bars at the bottom of the hole goes a greater way due to the greater speed, therefore, each grain removes a larger allowance than at a constant speed of rotation. Therefore, an increase in the speed of rotation of the honing head at the bottom of the hole leads to an increased removal of the allowance in this section of the hole and, therefore, to prevent the formation of surface shape deviations and increase processing productivity.

The essence of the method of honing is as follows.

The honing bars are introduced into the hole to be machined and pressed against the surface to be machined by means of a radial feed mechanism. At the same time, the bars are informed of reciprocating and rotational movements. Further, as the bars approach the bottom of the hole being machined, the speed of the rotational movement is increased so that at the bottom of the hole this speed assumes the maximum value. After the reverse movement of the bars during their reverse movement from the bottom of the hole, the rotation speed of the bars is reduced so that at the opposite point from the bottom of the hole the reverse speed takes a minimum value. Then the axial movement of the honing stones is reversed, and the cycle of the movement of the bars is repeated until the hole is machined.

The invention is illustrated by drawings.

Figure 1 shows the surface scan of the machined hole with a diameter of 38 mm and a length of 75 mm, having an initial shape deviation in the form of an ovality of 0.01 mm.

Figure 2 shows the surface scan of the machined hole by honing without increasing the speed of the peripheral speed of the bars.

Figure 3 shows the surface scan of the machined hole of the proposed method of honing with an increase in the peripheral speed of the bars.

Figures 4 and 5 show the dynamics of changes in processing indices for a batch of 10 parts without changing the peripheral speed and with the change in peripheral speed, respectively.

The proposed method for honing blind holes can be implemented by a honing machine having a controlled drive of rotation of the honing head. A similar drive is implemented in lathes with a contour numerical control system and allows, when turning the end face of a part, to increase its frequency of rotation as the cutter moves to the axis of rotation of the part, but to ensure a constant cutting speed.

Concrete implementation example

When processing for 60 minutes a blind hole with a diameter of 38.2 mm and a length of 75 mm, having an initial shape deviation in the form of an ovality of 0.01 mm (figure 1), a honing head equipped with 4 bars 40 mm long and 5 mm wide, with a radial discrete feeding of bars of 0.5 μm in size for each double stroke, axial speed of 6 m / min and constant peripheral speed of 10 m / min achieved non-circularity of the hole 4.7 μm and deviation of the forming hole from straightness of 0.0279 mm, the maximum size of the taken stock on the side of 0.0299 mm (figure 2).

From figure 2 it is seen that at the bottom of the blind hole there is ovality in contrast to the open edge of the hole, where ovality is completely eliminated. As a result, a taper is formed in the machined hole with the bottleneck at the bottom of the hole.

The increase in peripheral speed as the bars approach the bottom of the hole to be processed from 10 m / min to 20 m / min with the same other processing parameters allowed to obtain a non-circularity of the hole 1.2 μm; deviation of the generatrix from straightness of 0.0107 mm; the maximum value of the removed allowance on the side of 0.0309 mm (figure 3).

The effectiveness of the proposed method was tested on processing a batch of 10 parts. A comparison of the data on the allowance removal and the deviation of the forming hole from straightness (non-cylindricality) when processing a batch of 10 parts, respectively, without changing the peripheral speed and with its change, shows that increasing the peripheral speed at the bottom of the hole to be machined provides greater stability of the obtained deviation of the generatrix of the hole from straightness due to more uniform wear of the bars.

Thus, the application of the proposed method allowed to reduce the deviation of the generatrix of the hole from straightness by more than 2.5 times, and the ovality of the hole by 4 times with an increase in stock removal.

Claims (1)

The method of honing blind holes, including communicating to the honing bars of rotational and axial reciprocating movements and changing the speed of the rotational motion during processing, characterized in that the speed of rotational motion of the honing bars is increased with each axial movement from the reverse point at the open edge of the hole to the reverse point at its bottom and reduce this speed when the honing bars move in the opposite direction.

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