RU2211129C1 - Way of finishing abrasive machining of hole with elliptical surface - Google Patents

Abstract

FIELD: machining of metals, grinding of parts with holes having curvilinear elliptical cross-sections. SUBSTANCE: machined part and grinding spindle with wheel are given rotation and relative longitudinal feed. Rotation axis of grinding spindle is set at angle α with rotation axis of machined part to secure template-free machining. Value of angle is established depending on major and minor semi-axes of machined elliptical surface of hole. Wheel with peripheral cutting surface is divided during dressing into two parts equal in height. Machining is carried out with circular feed of cutting-in around cross point of axes of part and wheel. EFFECT: widened technological capabilities of way, increased precision and quality of machining. 3 cl, 4 dwg

Description

 The invention relates to metal working by grinding and can be used in the manufacture of parts with holes with curved elliptical cross sections.

 A known method of finishing a concave toroidal surface such as a groove of the outer ring of a deep groove ball bearing with a disk tool, in which the tool is brought into and inserted into the product in one circular motion, while the axis of rotation of the spindle is located at a distance equal to the radius of the circular axis of the groove of the product, and the axis the rotation of the tool with respect to the axis of the product is positioned at an angle according to the above formula [1].

 However, this method has limited technological capabilities and narrow specialization, while it requires the manufacture of complex and expensive equipment for its implementation, it does not allow to process elliptical internal surfaces and does not ensure the independence of the profile of the processed product from the diameter of the grinding wheel.

 A known method of boring holes with an elliptical surface, based on the fact that the projection of the circle on an inclined surface gives an ellipse [2]. Processing is carried out by rotating the cutter mounted in the spindle of the machine, and feeding at an angle to the workpiece mounted on the support.

 The known method has limited technological capabilities and narrow specialization and is not suitable for abrasive machining of holes with an elliptical surface, while it requires the manufacture of special equipment and a long setup time for its implementation, in addition, the issue of feeding the cut-in with repeated passes has not been resolved.

 The objective of the invention is to expand the technological capabilities of the method, improving the accuracy and quality of processing the inner elliptical surface, reducing the roughness and solving the issue of the implementation of the infeed for repeated passes, as well as ensuring the independence of the profile of the processed product from the diameter of the grinding wheel.

The problem is achieved by the proposed method of finishing abrasive machining of holes with an elliptical surface, namely, that the rotation axis of the grinding spindle is set to the rotation axis of the workpiece at an angle α, which is determined by the formula
α = arc cos (b / a),
where a and b are the major and minor axes of the processed ellipse, respectively.

 Moreover, the peripheral cutting surface of the circle when editing is divided into two surfaces of equal height: the farthest part is machined when the intersection of the axes of rotation of the part and the tool is located to the right of the machined part due to the longitudinal feed, the primal part is closest to the machined part works when the intersection of the axes of rotation of the part and the tool is in the workpiece or to the left of it.

 In this case, the insertion feed for removing the general allowance left for grinding is carried out in a circular motion around t. O, changing the angle α in the direction of reduction.

 In addition, as the wear and dullness of the circle make editing, in which there is a decrease in the outer diameter. To restore the latter, the circle is turned relative to the spindle, increasing the angle β of inclining it to a plane perpendicular to the axis of rotation of the circle.

 In FIG. 1 shows a diagram of an implementation of a method for finishing abrasive machining of holes with an elliptical surface; figure 2 is a left view along A in figure 1; in FIG. 3 shows a diagram of the implementation of the method of finishing abrasive machining of holes with an elliptical surface with a worn-out circle as much as possible; in FIG. 4 is a left view along B in FIG. 3.

The method of finishing abrasive processing of an hole with an elliptical surface is based on the fact that the projection of the circle onto an inclined plane gives an ellipse. Finishing abrasive treatment of a pre-bored hole is carried out by a rotating grinding wheel 1 mounted on a spindle, for example, inside a grinding machine, with a longitudinal feed S _pr The axis of rotation of the grinding spindle with a circle 1 is placed at an angle α to the axis of rotation of the workpiece 2, installed, for example, in the front headstock of the machine. The angle α is determined by the formula
α = arc cos (b / a),
where a and b are the major and minor axes of the processed ellipse, respectively.

The circle 1 can be located on the spindle both parallel and inclined at an angle β to a plane perpendicular to the axis of rotation, and is fixed to the spindle by means of mounting flanges 3 with beveled ends and nuts. Smooth adjustment of the angle β of the inclination of the circle 1 is carried out by mutual rotation of the flanges 3, in which the beveled ends are made at an angle β _max / 2, and the rotation of one flange from one end to an angle relative to the axis should correspond to the rotation of the same angle of the other flange with another end of the circle.

Before grinding begins with the new standard wheel, its peripheral cutting surface is corrected by dividing into two equal parts 4 and 5 of the surface, where the extreme side part 5 works when the intersection of the axes of rotation of the part and the tool is to the right of the workpiece (according to Fig. .1 and 3) due to the longitudinal feed S _pr , the front part 4 works when the intersection of the axes of rotation of the part and the tool is located in the workpiece or to the left of it. The outer diameter D of the new circle is 2a, i.e. value larger than the axis of the processed ellipse.

To remove the total allowance t left for grinding, a transverse feed S _{α is} necessary for cutting, which is carried out in a circular motion around t. On the intersection of the axes of rotation of the part and the tool, changing the angle α in the direction of reduction.

 As the abrasive wheel is worn out and its blunting is necessary, dressing is necessary, as a result of which the outer diameter decreases, therefore, to restore the outer diameter of the tool being machined, the circle is turned relative to the spindle, increasing its angle of inclination β to a plane perpendicular to the axis of rotation of the circle.

The maximum possible angle β _{max of} rotation of the circle relative to the spindle is equal to the angle α, while the diameter of the circle will be equal to 2b of the minor axis of the processed ellipse. With a smaller circle diameter, processing an ellipse of a given size is not possible. The remaining abrasive tool can be used to process smaller elliptical holes.

Example. Finishing abrasive machining of the hole with a curved elliptical surface (replacing the key connection) of the coupling half on the mod grinding machine. 3K228V. The material of the workpiece is steel 45 GOST 1050-74 (HB 260), the major axis of the elliptical hole is 2a = 125 mm, the minor axis is 2b = 104.26 mm, the machining length is 50 mm, the abrasive wheel is D _max = 125 mm, d = 32 mm, N = 20 mm, 24A25 cm 17K43 GOST 2424-83.

Processing modes: speed of the workpiece 40 m / min, minute longitudinal feed S _ol = 5390 mm / min, tool rotation speed 20 m / s, grinding allowance t = 0.3 mm per side, angle of inclination of the grinding spindle to the axis of rotation of the part α = arc cos (53.83 / 62.5) = 30 ^o 32 ', where 53.83 = (54.13-0.3) mm is the size of the semi-semi-axis of the workpiece, to remove the allowance t = 0.3 mm, grinding the spindle was rotated in total to an angle value α = 30 ^o (on S _α = 0 ^° 32 ′). Transverse circular feed circle - S _α = 0,015 mm / dv. stroke (S _α = 0 ^° 001′36 ″ / two-way).

 The processing was carried out in 20 passes with a coolant - emulsion. Abrasive processing by the proposed method allowed to obtain an elliptical inner surface of the desired quality and roughness (Ra = 0.63 μm) without burns and microcracks.

 The proposed method for finishing abrasive processing of holes with an elliptical surface allows you to expand the technological capabilities of obtaining accurate curved surfaces and relates to non-carbon kinematic methods. It allows you to increase the accuracy and quality of processing the inner elliptical surface, reduce the roughness and ensure the independence of the profile of the processed product from the diameter of the grinding wheel.

Sources of information taken into account
1. A. p. 563272, MKI V 24 V 19/06. The method of finishing processing a concave toroidal surface such as a groove of the outer ring of a deep groove ball bearing. Gavrilov V.P., Kolpakov D.I. Application 1859111/08, application. 12/18/72. publ. 06/30/77. Bull. 24.

 2. Karelin N.M. Ball-free machining of cylindrical parts with curved cross-sections. - M.: Mechanical Engineering, 1966, C 11-13, Fig. 10 is a prototype.

Claims (4)

1. The method of finishing abrasive machining of holes with an elliptical surface, including the rotation of the workpiece and the grinding spindle with a circle and a longitudinal feed, characterized in that the axis of rotation of the grinding spindle is set at an angle α to the axis of rotation of the workpiece, the angle being determined by the formula:
α = arc cos (b / a),
where a and b are, respectively, the major and minor axis of the machined elliptical surface of the hole.  2. The method according to p. 1, characterized in that they use a circle with a peripheral cutting surface, divided when editing it into two parts of equal height, while, during longitudinal feeding, the point of intersection of the axes of rotation of the workpiece and the circle to the right of the part is processed lead the farthest part of the circle farthest from the workpiece, and when the said point is inside the part or to the left of it, the near-end part closest to the workpiece.  3. The method according to p. 1 or 2, characterized in that to remove the total allowance for grinding, feed the insert with a circular motion of a circle around the point of intersection of the axes of rotation of the part and the circle with a change in angle α in the direction of its decrease.  4. The method according to any one of paragraphs. 1-3, characterized in that the circle is rotated relative to the spindle with an increase in the angle β of its inclination to a plane perpendicular to the axis of rotation of the circle, to restore the value of the outer diameter of the circle when it is worn.

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