RU2160659C2 - Grinding wheel dressing method - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: prior to dressing, ends of grinding wheel are coated with conducting layers. Wheel is driven to rotation. Dressing tool along with sensing elements and control unit is moved along generatrix of wheel operating surface. After every longitudinal displacement tool is driven to transverse motion. Preliminarily moment of dressing tool touching the conducting layer on wheel end, diameter of which is of minimum wear, is recorded. As soon as moment of dressing tool touching the conducting layer is recorded preliminary operation is stopped. As a result, straightening of wheel operating surface along the entire length of generatrix is ensured. EFFECT: improved dressing quality. 1 tbl, 4 dwg

Description

 The invention relates to mechanical engineering and can be used in the processing of parts on grinding machines.

 Known methods of dressing grinding wheels ([1], S. 234), which produce a gradual alignment of the working surface of the wheel, including rough, finish dressing and nursing. The number of passes and dressing modes at each stage are set depending on the size of the stock taken during the upcoming grinding operation.

 A disadvantage of the known technical solution is that at the draft stage for guaranteed alignment of the working surface, the number of passes is not specified, which increases the consumption of abrasive. So, depending on the type of grinding, the abrasive consumption for dressing is 50 ... 95% ([1], p. 229).

 The closest technical solution to the proposed one is the dressing method of grinding wheels [2], in which at each stage the ruling tool is informed of longitudinal and transverse movement along the generatrix of the working surface and the dressing force is measured at each pass, while each dressing step is stopped after reaching a specific for each stage of the quantity φ. This reduces the consumption of abrasive.

 The disadvantage of this method is the low accuracy of the geometric shape of the working surface of the circle after editing. This is due to the fact that in the process of, for example, circular external grinding with longitudinal feed, the working cylindrical part of the wheel wears unevenly ([1], p. 215). When the circle contacts the part, the greatest load falls on the edges of the circle, which, as a result, crumble at each pass, while both the cylindrical working surface and the end surfaces are destroyed. The magnitude of these defects is significantly (up to 2 ... 3 times) higher than the magnitude of the defective layer on the remaining portion of the working surface. Subsequent editing by known methods (without fixing the touch of the ends of the circle with the governing tool), the defective layer is removed from the cylindrical portion of the working surface, its straightness and cylindricality are restored, while the length of the generatrix of the cylindrical working part is less than the height of the circle due to defects in chipping the edges of the circle. The cylindrical part of the circle finishes (calibrates) the surface of the part, so reducing its length causes a deterioration in the quality of the surface of the part (roughness and shape accuracy).

 The objective of the invention is to improve the quality of editing by improving the geometric shape of the circle.

 The elimination of defects on the edges and the working surface during dressing is achieved by the fact that in the method of dressing the grinding wheels the rotation is reported to the latter, and the ruling tool is moved longitudinally along the generatrix of the wheel, and after each longitudinal movement the tool is given lateral movement, the value of which is selected depending on the nature of wear of the working surface, and before editing on the ends of the circle they apply electrically conductive layers, and at the rough stage fixes the moment of contact with the ruling inst by the runtime of the electrically conductive layer at the end of the circle having the smallest wear of the diameter, while fixing the moment of contact of the electrically conductive layer at the end of the circle that has the greatest wear of the diameter, the roughing editing step is stopped.

 Application before the start of processing on the ends of the electrically conductive layers allows, at the end of dressing, to fix the actual wear of the circle taking into account chipping of the edges and to improve the quality of dressing by increasing the accuracy of the geometric shape of the circle.

 In FIG. 1 is a functional diagram of the proposed method. In FIG. 2, 3, 4 presents the editing sequence for the proposed method.

On the functional diagram:
1 - grinding wheel, being edited, having a working surface 2;
3 - electrically conductive layers at the ends of the circle;
4 - machine spindle;
5, 7 - touch control sensors by the governing tool of the electrically conductive layers;
6 - the ruling instrument;
8 - control unit.

The method is as follows (Fig 1). The grinding wheel 1 with the worn working 2 and end surfaces, and accordingly the electrically conductive layers 3 is mounted on the spindle of the machine 4 and rotated with a speed of V _cr . The ruling tool 6 together with the sensors 5 and 7, the control unit 8 is fixed on the support of the machine and moved along the generatrix of the working surface of the circle 2 with a longitudinal feed S _CR and in the radial direction with a transverse feed S _pop .

By combining these motions (V _cr, S _ave, S _pop) produce editing - removing the defective layer (Δ) on the working surface of the wheel 2 (FIG 2.).

After removing part of the defective layer (Δ ₁ ) when the governing tool touches the electrically conductive layer 6 at the end (point 1), which has the smallest wear of diameter D ₁ , the sensor 5 turns on the control unit 8 and puts it into "standby" mode. The dressing process continues until the remnants of the defective layer (Δ ₂ ) are removed, FIG. 3, and touches by the governing tool 6 of the electrically conductive layer at the end (point 2) having the greatest wear of the diameter D ₂ . By the signal of the sensor 7, the control unit 8 exits the "standby" mode, the editing step is stopped, the ruling tool 6 is brought out of contact with the working surface 2.

The proposed straightening method ensures the alignment of the working surface along the entire length of the generatrix, i.e. the length of the generatrix of the cylindrical part of the circle (l) is equal to the height of the circle (H _cr ) (Fig. 4). The accuracy of the geometric shape of the working surface of the circle (the straightness of the generatrix and non-circularity) is formed at the subsequent finishing and nursing stages, which are performed by known methods.

 Tests of the proposed dressing method on a circular grinding machine mod. 3A164 when machining a shaft made of 34XH1M HRC 40 ... 45 steel with a diameter of 250 mm and a length of 13000 mm. Used grinding wheel PP 500x50x305 with characteristics 93A40CM2K8. The governing tool (Slavutich diamond substitute), dressing and grinding modes were adopted in accordance with current standards. The machine was equipped with control systems for the degree of alignment of the working surface according to the known and proposed dressing method based on a strain gauge amplifier, an electronic control unit, type 310 probes and other elements with a flow chart in FIG. 1.

 The test results are shown in the table.

Using the proposed method for editing an abrasive wheel in comparison with the known one allows, by increasing the length of the generatrix of the cylindrical working surface of the wheel to the optimum value (l = H _cr ) and the accuracy of the geometric shape of the circle (non-cylindricality), reduce the height of the roughness on the treated surface by 23%.

SOURCES OF INFORMATION:
1. Lizard P.I. and others. Grinding metals. Minsk, Belarus, 1963.

 2. Patent of Russia N 2014210, B 24 B 53/00.

Claims (1)

 A method of dressing grinding wheels, including the draft, finishing and nursing stages of dressing with a message to the grinding wheel rotation, and the ruling tool of longitudinal movement along the generatrix of the wheel, while after each longitudinal movement of the tool report lateral movement, the value of which is selected depending on the nature of wear of the working surface, characterized in that before editing the ends of the circle are applied electrically conductive layers, and at the rough stage they fix the moment of contact with the ruling inst by the runtime of the electrically conductive layer at the end of the circle having the smallest wear of the diameter, while fixing the moment of contact of the electrically conductive layer at the end of the circle that has the greatest wear of the diameter, the roughing editing step is stopped.

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