Internal thread parallel shaft type grinding machining method

Abstract

The invention relates to a thread machining method. An internal thread parallel shaft type grinding machining method comprises the steps of preparation before grinding; the tooth form parameters of the internal threads are determined, the grinding wheel is finished and shaped according to the coordinates of the tooth form outline of the internal threads, the coordinates comprise the X direction and the Z direction, the grinding wheel is compensated in the Z direction, and the height of threads machined on the grinding wheel is not larger than that of threads of the internal threads; and finally, processing internal threads. According to the internal thread parallel shaft type grinding machining method, burrs can be effectively avoided, the machining cost is reduced, and the procedure is simple. The technical problems that in the prior art, when parallel shaft type grinding machining is conducted on internal threads, the number of working procedure steps is large, and cost is high are solved.

Description

Technical Field

[0001] The invention relates to a thread processing method, in particular to an internal thread parallel axis grinding processing method. Background Art

[0002] The internal thread processing of ordinary nuts is generally carried out by grinding with the center axis of the grinding wheel and the center axis of the nut at a certain angle to avoid interference between the grinding wheel and the nut. However, for nuts with a large aspect ratio, if a certain angle is still maintained, the grinding wheel arbor will collide with the top of the threaded hole, resulting in the inability to process deeply. The parallel axis grinding process is adopted, and the rotation axis of the grinding wheel and the nut are parallel and deviated by a certain distance, which can avoid the interference caused by the collision between the grinding wheel arbor and the nut. The grinding wheel used in this method is a diamond grinding wheel, and the grinding wheel tip angle is the same as the tooth profile angle of the internal thread of the nut. At this time, the thread tooth angle and the median diameter will change due to the interference between the grinding wheel and the internal thread. The tooth angle and median diameter caused by interference will produce errors. Currently, in the parallel axis grinding process of internal threads, the thread height processed on the grinding wheel is usually greater than the thread height of the internal thread. However, when the thread height on the grinding wheel is greater than the thread height of the internal thread, the small diameter of the internal thread cannot be ground, which will cause the burrs generated by grinding extrusion at the small diameter to be unable to be removed during grinding. It is necessary to add a separate burr removal station, which increases the processing cost. Summary of the invention

[0003] The invention provides an internal thread parallel axis grinding method which can effectively avoid burrs, reduce processing costs and has simple procedures; and solves the technical problems of multiple procedures and high costs in the prior art when processing internal threads by parallel axis grinding.

[0004] The above technical problem of the present invention is solved by the following technical solution: a parallel axis grinding method for internal threads, comprising:

[0005] The first step is preparation before grinding: prepare the thread grinder, disc dressing wheel, cylindrical grinding wheel and nut processing blank;

[0006] The second step is grinding wheel dressing: determine the tooth profile parameters of the internal thread, and perform grinding wheel dressing and shaping according to the coordinates of the internal thread tooth profile. The coordinates include the X direction and the Z direction. The grinding wheel is compensated in the Z direction so that the thread height processed on the grinding wheel is not greater than the thread height of the internal thread.

[0007] The third step is to process the internal thread: the nut blank is positioned by the end face, and the grinding wheel itself keeps rotating clockwise at high speed, while making linear feed motion along its own axis. After reaching the specified position, radial feed grinding begins, and the nut blank rotates counterclockwise slowly relative to the grinding wheel to complete the grinding of the entire internal thread.

[0008] When the grinding wheel is being dressed, the thread height processed on the grinding wheel is less than or equal to the thread height of the internal thread, so during the internal thread grinding process, the internal thread minor diameter is also ground, thereby avoiding the generation of burrs. The present invention can reduce the process of removing burrs separately and reduce the processing cost.

[0009] As a preferred step, in the first step, the internal thread processing program is input on the thread grinder: X = (e + h1) * t, Formula e is the eccentricity between the grinding wheel axis and the nut axis, which is equal to half of the difference between the internal thread minor diameter and the maximum diameter of the grinding wheel. h1 is the internal thread thread height, n is the number of internal thread heads, P is the internal thread pitch, and t is a parameter variable, t∈[0,1], It is the helix angle of the internal thread.

[0010] Preferably, in the second step, the correction parameters of the grinding wheel are designed as follows: X1=h2-r*sin(A / 2), Z1=X1*tan(A / 2), X2=r*sin(A / 2), Z2=r*cos(A / 2), Z3=P / 2-Z1-Z2, wherein h2 is the thread height of the grinding wheel, h2 is less than or equal to the thread height of the internal thread, r is the major diameter fillet of the internal thread, A is the thread angle of the internal thread, X1, X2, Z1, and Z2 are the coordinates corresponding to the thread profile of the internal thread, and Z3 is the pitch compensation.

[0011] The pitch compensation is performed on the Z direction of the grinding wheel to ensure accurate processing of the tooth angle and pitch of the internal thread.

[0012] Preferably, the tool angle of the dressing wheel is smaller than the internal thread profile angle, and the fillet at the top of the tool is smaller than or equal to the fillet size of the internal thread top.

[0013] Preferably, the grinding wheel is trimmed into one tooth shape or multiple tooth shapes. Different types of grinding wheels are rotated according to different internal threads to be processed. Grinding wheels with multiple tooth shapes are used to process internal threads with a helix angle of 0, thereby improving processing efficiency.

[0014] Therefore, the parallel-axis grinding method for internal threads of the present invention has the following advantages: when the grinding wheel is trimmed, the thread height processed on the grinding wheel is not greater than the thread height of the internal threads, so that during the internal thread grinding process, the internal thread minor diameter is also ground to avoid the generation of burrs, thereby eliminating the subsequent burr grinding process and reducing the processing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The figure is a schematic diagram of a grinding process of an internal thread parallel axis grinding process.

[0016] Figure 2 yes Figure 1 Front view of the grinding wheel.

[0017] Figure 3 yes Figure 1 Enlarged view of point A.

[0018] Figure 4 This is a front view of the grinding wheel in Example 2. DETAILED DESCRIPTION

[0019] The technical solution of the invention is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0020] Embodiment 1:

[0021] like Figure 1 and 2 As shown in Figure 3, a parallel axis grinding method for internal threads is used to process the nut of a differential planetary roller screw as an example. The internal thread of the nut is a helix angle A rectangular slot with a value of 0 and a number of teeth a = 12:

[0022] Preparation before grinding: prepare the thread grinder, disc dressing wheel, cylindrical grinding wheel and nut processing blank, and input the internal thread processing program on the thread grinder: X = (e + h1) * t, Formula e is the eccentricity between the axis of the grinding wheel 1 and the axis of the nut 2, which is equal to half of the difference between the minor diameter of the internal thread and the maximum diameter of the grinding wheel. h1 is the height of the internal thread, n is the number of internal thread heads, P is the internal thread pitch, and t is a parameter variable, t∈[0,1]. It is the helix angle of the internal thread. When machining differential planetary roller screw nuts, take Z = 0;

[0023] Grinding wheel dressing: Determine the tooth profile parameters of the internal thread, which include tooth angle, pitch, thread height, and major diameter fillet of the internal thread. Calculate the coordinates of the internal thread tooth profile to perform grinding wheel dressing and shaping: X1 = h2-r*sin(A / 2), Z1 = X1*tan(A / 2), X2 = r*sin(A / 2), Z2 = r*cos(A / 2), Z3 = P / 2-Z1-Z2, where h2 is the thread height of the grinding wheel, h2 is less than or equal to the thread height of the internal thread, r is the major diameter fillet of the internal thread, A is the tooth angle of the internal thread, X1, X2, Z1, and Z2 are the coordinates corresponding to the tooth profile of the internal thread, and Z3 is the pitch compensation. In order to improve processing efficiency, the grinding wheel is dressed to multiple tooth shapes, and the number of teeth b of the grinding wheel is two more than the number of teeth a of the internal thread of the nut, that is, b = a+2. And the height h2 of the thread 3 of the grinding wheel is equal to the height h1 of the thread of the internal thread of the nut;

[0024] Machining internal threads: The nut blank is positioned with the end face, and the grinding wheel itself keeps rotating at high speed clockwise, while making linear feed motion along its own axis. The axial movement is stopped after reaching the specified position, and radial feed grinding starts. The nut blank rotates slowly counterclockwise relative to the grinding wheel to complete the grinding of the entire internal thread. The processing is efficient through grinding wheels with multiple tooth shapes.

[0025] Embodiment 2:

[0026] like Figure 4 As shown, different from Example 1, the grinding wheel is dressed into a tooth shape for processing a helical internal thread with a helix angle not equal to 0.

[0027] Embodiment 3:

[0028] Different from the first embodiment, the height h2 of the thread 3 of the grinding wheel is smaller than the height h1 of the thread of the internal thread of the nut.

[0029] The specific embodiments described herein are merely examples of the concept of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A parallel axis grinding method for internal threads, characterized in that: The first step is preparation before grinding: prepare the thread grinder, disc dressing wheel, cylindrical grinding wheel and nut processing blank; The second step is grinding wheel dressing: determine the tooth profile parameters of the internal thread, and perform grinding wheel dressing and shaping according to the coordinates of the internal thread tooth profile. The coordinates include the X direction and the Z direction. The grinding wheel is compensated in the Z direction so that the thread height processed on the grinding wheel is not greater than the thread height of the internal thread. The third step is to process the internal thread: the nut blank is positioned by the end face, and the grinding wheel itself keeps rotating clockwise at high speed, while making linear feed motion along its own axis. After reaching the specified position, radial feed grinding begins, and the nut blank rotates counterclockwise slowly relative to the grinding wheel to complete the grinding of the entire internal thread.

2. The internal thread parallel axis grinding method according to claim 1, characterized in that: In the first step, enter the internal thread processing program on the thread grinder: X = (e + h1) * t, Formula e is the eccentricity between the grinding wheel axis and the nut axis, which is equal to half of the difference between the internal thread minor diameter and the maximum diameter of the grinding wheel. h1 is the internal thread thread height, n is the number of internal thread heads, P is the internal thread pitch, and t is a parameter variable, t∈[0,1], It is the helix angle of the internal thread.

3. A parallel axis grinding method for internal threads according to claim 1 or 2, characterized in that: In the second step, the correction parameters of the grinding wheel are designed as follows: X1=h2-r*sin(A / 2), Z1=X1*tan(A / 2), X2=r*sin(A / 2), Z2=r*cos(A / 2), Z3=P / 2-Z1-Z2, where h2 is the thread height of the grinding wheel, h2 is less than or equal to the thread height of the internal thread, r is the major diameter fillet of the internal thread, A is the thread angle of the internal thread, X1, X2, Z1, and Z2 are the coordinates corresponding to the thread profile of the internal thread, and Z3 is the pitch compensation.

4. The internal thread parallel axis grinding method according to claim 1 or 2, characterized in that: The tool angle of the dressing wheel is smaller than the internal thread profile angle, and the fillet at the top of the tool is smaller than or equal to the fillet size of the internal thread top.

5. The internal thread parallel axis grinding method according to claim 1 or 2, characterized in that: The grinding wheel is dressed into one tooth shape or multiple tooth shapes.

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