Method and device for machining arc root of arc thread

Abstract

The invention belongs to the technical field of thread machining, and particularly relates to an arc thread root machining method and device. The method comprises the following steps: determining a stepping angle when a tooth root arc is machined according to a tool nose radius, a tooth root arc radius and surface roughness of a tool; calculating a cutter rotation angle of each cutter during machining according to the stepping angle; calculating the offset coordinate of each cutter when the cutter moves according to the cutter tip radius, the tooth form parameter and the cutter rotation angle of each cutter; the tooth form parameters comprise a tooth bottom arc radius, a tooth height and a tooth form angle; and the arc tooth bottom is machined according to the calculated offset coordinate of each cutter when the cutter moves and the cutter rotation angle until the cutter rotation angle is rotated from # imgabs0 # to # imgabs1 # theta to form a tooth form angle, and the machining efficiency is improved while it is guaranteed that the surface roughness of the arc tooth bottom is consistent.

Description

Technical Field

[0001] The invention belongs to the technical field of thread processing, and in particular relates to a method and a device for processing an arc thread arc tooth bottom. Background Art

[0002] Threaded connection is a common connection method. Compared with ordinary metric threads, MJ threads, etc., arc threads have great advantages in processing and manufacturing, structural strength and fatigue resistance. For example, the Chinese invention patent application with application publication number CN109967982A discloses a method for preparing an arc thread anchor assembly for a wind turbine generator set, wherein the external thread on the anchor is a continuous arc thread, including a crest arc, a straight line segment, a bottom arc, and a straight line segment connected in sequence, and the straight line segment is tangent to the crest arc and the bottom arc, respectively. Since the arc thread adopts a large pitch and non-equal width tooth thickness, not only the axial fit clearance is large, but also stress concentration can be reduced and fatigue resistance can be improved. In addition, the Chinese utility model patent with authorization announcement number CN209818480U discloses a high-strength arc thread connection pair. The arc thread connection pair adopts an arc thread tooth profile. The internal thread and the external thread are in surface contact, and the force is evenly distributed. It can effectively reduce the stress concentration when the thread is loaded, and has good anti-fatigue performance. The patent discloses two arc thread structures with thread major diameters of 42 and 48, and pitches of 6.35 and 8.5 respectively. The patent with authorization announcement number CN116877555B discloses a stud for connecting the root of a wind turbine blade and a processing method thereof. The external thread of the stud thread section is an arc thread, and the nominal diameter d of the arc thread is 1.3mm. 公称 =36mm~40mm, arc thread pitch Pr=(0.153~0.192)d 公称 , arc thread tooth height hr = (0.37 ~ 0.44) Pr, arc thread minor diameter d1r = d 公称 -0.8746Pr. The tooth profile of the large pitch arc thread is a symmetrical structure, including two symmetrical arc tooth tops, two side lines and an arc tooth bottom. In traditional technology, the arc tooth bottom of the arc thread is generally processed by the method of equal-pitch linear feed, such as Figure 1As shown, the tooth bottom is fed with equal spacing linearly according to the spacing of Δx. However, due to the large arc radius of the tooth bottom of the large pitch arc thread, the direct processing tool is subjected to large force, which is prone to overload or tool vibration. In addition, the surface roughness of the arc tooth bottom processed by the equal spacing linear feed method is relatively discrete and the processing efficiency is low. Therefore, in recent years, there have also been arc feed methods that use equal angle stepping based on polar coordinates, sine function or cosine function. The arc feed method with equal angle stepping can ensure that the roughness of the machined surface tends to be consistent, but its step angle is selected based on experience. When the step angle is too large, the roughness of the machined surface cannot be guaranteed. When the step angle is too small, the processing efficiency is too low. Therefore, in order to ensure the surface roughness during processing, the step angle used is generally too conservative. Although the processing efficiency is improved compared with the equal spacing linear feed efficiency, it is still relatively low. Summary of the invention

[0003] The purpose of the present invention is to provide a method and device for processing the arc thread arc root, so as to solve the problem that the existing method for processing the arc thread arc root cannot achieve consistent roughness and high processing efficiency at the same time.

[0004] In order to solve the above technical problems, the present invention provides a method for processing the arc thread arc tooth bottom, comprising the following steps:

[0005] 1) Determine the step angle when machining the tooth bottom arc according to the tool tip radius, tooth bottom arc radius and surface roughness;

[0006] 2) Calculate the tool rotation angle for each cut during processing based on the step angle;

[0007] 3) Calculate the offset coordinates of each cut when the tool moves according to the tool tip radius, tooth profile parameters and tool rotation angle of each cut; tooth profile parameters include tooth bottom arc radius, tooth height and tooth profile angle;

[0008] 4) According to the calculated offset coordinates of each cut and the tool rotation angle when the tool moves, the arc tooth bottom is processed until the tool rotation angle changes from Rotate to θ is the tooth angle.

[0009] Furthermore, in step 1), the step angle when machining the tooth bottom arc is determined according to the following formula:

[0010]

[0011] Where Δβ is the step angle, R 刀 is the tool tip radius, R 底 R is the radius of the tooth bottom arc, z is the surface roughness.

[0012] Furthermore, the method for calculating the tool rotation angle of each cut during processing based on the step angle is as follows: if the absolute value of the difference between the offset of the next cutter rotation angle determined according to the current step angle in the radial feed direction of the turning tool and the offset of the current cutter rotation angle in the radial feed direction of the turning tool is greater than the absolute value of the maximum feed amount, then the step angle is redetermined according to the maximum feed amount, and the tool rotation angles of each cutter after the current cut are calculated based on the redetermined step angle.

[0013] Furthermore, the method for re-determining the step angle according to the maximum feed amount is to calculate the step angle according to the following formula:

[0014]

[0015] Among them, Δβ′ is the re-determined step angle, β n is the tool rotation angle of the nth tool, the nth tool is the current tool, R 底 R is the radius of the tooth bottom arc, 刀 is the tool tip radius, X n is the X-direction offset of the tool position relative to the origin O, ΔX max is the maximum feed amount, X 底 is the X-direction offset of the center of the arc of the tooth bottom relative to the origin O, the origin O is the intersection of the tooth top and the symmetry axis of the tooth profile, the radial retraction direction of the turning tool is the positive X direction, the radial feed direction of the turning tool is the negative X direction, the positive direction of the angular momentum when the spindle rotates counterclockwise is the positive Z direction, and the negative direction of the angular momentum when the spindle rotates counterclockwise is the negative Z direction.

[0016] Furthermore, the tool tip radius must be greater than or equal to the minimum tool tip radius and less than or equal to the maximum tool tip radius; the maximum tool tip radius is the tooth bottom arc radius, and the minimum tool tip radius is the set multiple of the maximum tool tip radius, and the set multiple is greater than or equal to 1 / 3 and less than or equal to 1 / 2.

[0017] Furthermore, the offset coordinate of each cutter when the cutter moves is (X n , Z n ), X n and Z n Calculated according to the following formula:

[0018] X n =X 底 -(R 底 -R 刀 )cos(β n )

[0019] Z n =(R 底 -R 刀 )sin(β n )

[0020] Among them, X n The X-direction offset of the tool position relative to the origin O, Z n X is the Z-direction offset of the tool position relative to the origin O. 底 R is the X-direction offset of the center of the tooth bottom arc relative to the origin O, 底 R is the radius of the tooth bottom arc, 刀 is the tool tip radius, β n is the tool rotation angle of the nth tool, the origin O is the intersection of the tooth top and the tooth profile symmetry axis, the radial retraction direction of the turning tool is the positive X direction, the radial feed direction of the turning tool is the negative X direction, the positive direction of the angular momentum when the spindle rotates counterclockwise is the positive Z direction, and the negative direction of the angular momentum when the spindle rotates counterclockwise is the negative Z direction.

[0021] Furthermore, X 底 Calculated according to the following formula:

[0022] X 底 =R 底 -H

[0023] Among them, H is the tooth height.

[0024] Furthermore, in step 2), the tool rotation angle of each cut is equal to the tool rotation angle of the previous cut minus the step angle of the current layer.

[0025] Furthermore, the rotation direction of the tool during machining is counterclockwise.

[0026] The beneficial effects of the above technical solution are as follows: the present invention is a pioneering invention. When the arc tooth bottom of the arc thread is processed by the equal-angle feed method, the relationship between the surface roughness and the step angle is established, and the step angle is determined based on the surface roughness. Therefore, the maximum step angle that can be achieved during processing can be selected to process the arc tooth bottom while ensuring the consistency of the surface roughness of the tooth bottom processing. This solves the problem that the step angle cannot achieve both consistent roughness and high processing efficiency at the same time due to the experience-based selection of the step angle during existing equal-angle processing. This ensures consistent surface roughness while also improving processing efficiency.

[0027] In order to solve the above technical problems, the present invention also provides a circular arc thread circular arc root processing device, including a processor, wherein the processor is used to execute computer program instructions to implement the circular arc thread circular arc root processing method introduced above.

[0028] The beneficial effects of the above technical solution are as follows: the present invention is a pioneering invention. When the arc tooth bottom of the arc thread is processed by the equal-angle feed method, the relationship between the surface roughness and the step angle is established, and the step angle is determined based on the surface roughness. Therefore, the maximum step angle that can be achieved during processing can be selected to process the arc tooth bottom while ensuring the consistency of the surface roughness of the tooth bottom processing. This solves the problem that the step angle cannot achieve both consistent roughness and high processing efficiency at the same time due to the experience-based selection of the step angle during existing equal-angle processing. This ensures consistent surface roughness while also improving processing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the tool path when machining the tooth bottom with equal-pitch linear feed in the prior art;

[0030] Figure 2 is a flowchart of processing arc thread arc tooth bottom according to an embodiment of the method of the present invention;

[0031] Figure 3 Schematic diagram of the tool path of the embodiment of the method of the present invention;

[0032] Figure 4 It is a geometric relationship diagram when calculating the arc step angle of the tooth bottom in the embodiment of the method of the present invention;

[0033] Figure 5 is a geometric relationship diagram when calculating offset coordinates in an embodiment of the method of the present invention;

[0034] Figure 6 Schematic diagram of tooth bottom cutting traces in an embodiment of the method of the present invention. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the specific implementation methods of the present invention are further described below in conjunction with the accompanying drawings.

[0036] The present invention adopts an equal-angle feed method to machine the arc tooth bottom of an arc thread, establishes a relationship between surface roughness and step angle, and determines the step angle based on the surface roughness, so that the maximum step angle that can be achieved during machining can be selected to machine the arc tooth bottom while ensuring the consistency of the surface roughness of the tooth bottom machining, thereby solving the problem that the step angle is selected based on experience during the existing equal-angle machining and cannot simultaneously achieve consistent roughness and high machining efficiency. The method of arc feed is adopted to ensure the consistency of surface roughness while greatly improving the machining efficiency of the arc of the tooth bottom of a large pitch thread.

[0037] Method Embodiment

[0038] A method for machining a circular arc thread arc tooth bottom of the present invention, as Figure 2 As shown, the specific process is as follows:

[0039] 1. Determine the coordinates of the center of the arc at the bottom of the tooth (X 底 , Z 底 ).

[0040] The intersection of the tooth top and the tooth profile symmetry axis is taken as the origin O, the radial retraction direction of the turning tool is the positive direction of X, the radial feed direction of the turning tool is the negative direction of X, the positive direction of the angular momentum when the spindle rotates counterclockwise is the positive direction of Z, the negative direction of the angular momentum when the spindle rotates counterclockwise is the negative direction of Z, the tooth profile angle is θ (in degrees), and the arc radius of the tooth bottom is R 底 , the center of the arc at the bottom of the tooth is O 底 , tooth height is H, calculate the center of the tooth bottom arc O 底 X-direction offset relative to the origin O 底 and the Z-direction offset Z relative to the origin O 底 The calculation formula is as follows:

[0041] X 底 =-(HR 底 )=R 底 -H

[0042] Z 底 =0

[0043] 2. Determine the tool tip radius.

[0044] In this embodiment, the tool uses an existing arc groove tool. The maximum tool tip radius To ensure machining efficiency, the minimum tool tip radius The maximum tool tip radius of the tool with the set multiple is greater than or equal to 1 / 3 and less than or equal to 1 / 2. Preferably, the set multiple is 1 / 2, that is:

[0045]

[0046] At this time, the tool nose radius R 刀 The selection range is:

[0047] 0.5R 底 ≤R 刀 ≤R 底

[0048] like Figure 3 As shown in the figure, the center of the tooth bottom arc is used as the rotation axis, the vertical downward direction is the positive direction of the tool radius R2, the counterclockwise direction is the positive direction of the rotation angle β, and the machining is performed with the step angle Δβ when machining the tooth bottom arc, so that the tool rotation angle when machining the tooth bottom arc is Movement from 0 to The unit of rotation angle is °, and the tool radius R2 = R 底 -R 刀 .

[0049] 3. Determine the step angle when machining the tooth bottom arc based on the surface roughness.

[0050] like Figure 4 As shown, O 刀 is the center of the current tool tip arc, O′ 刀 is the center of the arc of the tool tip of the next cut. The step angle between two adjacent cuts is Δβ. According to the cosine theorem, the calculation formula of Δβ is as follows:

[0051]

[0052] Among them, R z is the surface roughness, R z Determine according to actual needs. According to the surface roughness, the arc radius of the tooth bottom and the tool tip radius, the step angle suitable for the arc tooth top can be calculated.

[0053] 4. Calculate the tool rotation angle based on the step angle.

[0054] The tool rotation angle of each cut is equal to the tool rotation angle of the previous cut minus the step angle of the current layer, β n =β n-1 -Δβ,β n is the tool rotation angle of the nth tool, β n-1 is the tool rotation angle of the n-1th tool,

[0055] 5. Calculate the offset coordinates of each cut when the tool moves.

[0056] According to the tool tip radius, tooth profile parameters and the rotation angle of each layer of tool, the offset coordinates (X n , Z n ); tooth profile parameters include tooth bottom arc radius, tooth height and tooth profile angle. Figure 5 As shown in the figure, for any tool n when machining the tooth bottom arc, the tool rotation angle is β n , the X-direction offset of the tool position (i.e. the center of the tool tip arc) relative to the origin O n The calculation formula is:

[0057] X n =X 底 -(R 底 -R 刀 )cos(β n )=R 底 -H-(R 底 -R 刀 )cos(β n )

[0058] The Z offset of the tool position relative to the origin O n The calculation formula is:

[0059] Z n =(R 底 -R 刀 )sin(β n )

[0060] 6. According to the calculated offset coordinates (X n , Z n ) and the corresponding rotation angle β n The arc tooth bottom is machined until the tool rotation angle changes from Rotate to

[0061] like Figure 6 As shown, the feed direction is in an arc from right to left. First, calculate the tool rotation angle β1 of the first cut: β1 = β0-Δβ, The tool offset coordinates (X1, Z1) of the first cut are calculated based on β1, and (X1, Z1) is used as the offset coordinates to perform spiral processing according to the rotation angle of β1; then the tool rotation angle β2 of the second cut is calculated: β2 = β1-Δβ, and the offset coordinates (X2, Z2) of the second cut are calculated based on β2, and (X2, Z2) is used as the offset coordinates to perform spiral processing according to the rotation angle of β2, and so on until the processing is completed. At this point, the processing of the tooth bottom arc is completed. Preferably, considering the rigid deformation of the guide rod, the tool rotates counterclockwise when the tool is moving, so that the current processing tool position always has material to support the tool, effectively reducing the tool vibration phenomenon. Specifically, considering that the tooth shape is a symmetrical tooth shape, the first cut of each layer is counterclockwise relative to the center of the tooth top arc of the tooth side to be processed, and the last cut of each layer is counterclockwise relative to the center of the tooth top arc of the tooth side to be processed. Overall, it is tangent to the tooth top arc and rotates and offsets toward the tooth bottom.

[0062] As another embodiment, in order to avoid reducing the tool life when the feed amount exceeds the preset maximum feed amount, the present invention also considers the maximum feed amount ΔX when determining the step angle. max If the absolute value of the difference between the offset of the next tool rotation angle determined according to the current step angle in the radial feed direction of the turning tool and the offset of the current tool rotation angle in the radial feed direction of the turning tool is greater than the absolute value of the maximum feed amount, the step angle is re-determined according to the maximum feed amount, and the tool rotation angles of each tool after the current tool are calculated according to the re-determined step angle. Specifically, for any tool, the tool offset coordinate is (X n , Z n ), the tool rotation angle of the n+1th tool calculated according to the current step angle Δβ is β n+1, the corresponding offset coordinates of the n+1th knife are (X n+1 , Z n+1 ), if the absolute value of the difference between the offsets of the two knives in the X direction |X n+1 -X n |Greater than the maximum feed amount ΔX max The absolute value of the maximum feed amount ΔX max Re-determine the step angle Δβ′ and use it to replace the value of Δβ, and calculate the new tool offset coordinate (X′) of the n+1th tool n+1 , Z′ n+1 ), X′ n+1 To consider the X-direction offset of the tool position of the n+1th tool relative to the origin O when the maximum feed amount is considered, Z′ n+1 is the Z-direction offset of the tool position of the n+1th tool relative to the origin O when considering the maximum feed amount, β′ n+1 is the rotation angle of the n+1th tool when considering the maximum feed amount. Figure 5 The geometric relationship shown in the figure, the calculation formula of Δβ′ is as follows:

[0063]

[0064] Z′ n+1 =(R 底 -R 刀 )sin(β′ n+1 )

[0065]

[0066] The re-determined Δβ′ is used as the new step angle to replace the original Δβ and continue machining until The arc tooth top processing is completed at the same time.

[0067] Device Embodiment

[0068] The present invention provides a circular arc thread circular arc root processing device, which is used to execute computer program instructions to implement a circular arc thread circular arc root processing method introduced in the above method embodiment. The device can be a CNC lathe for processing threads.

Claims

1. A method for machining an arc thread arc root, characterized in that: The steps include: 1) Determine the step angle when machining the tooth bottom arc according to the tool tip radius, tooth bottom arc radius and surface roughness; 2) Calculate the tool rotation angle for each cut during processing based on the step angle; 3) Calculate the offset coordinates of each cut when the tool moves according to the tool tip radius, tooth profile parameters and tool rotation angle of each cut; tooth profile parameters include tooth bottom arc radius, tooth height and tooth profile angle; 4) According to the calculated offset coordinates of each cut and the tool rotation angle when the tool moves, the arc tooth bottom is processed until the tool rotation angle is Rotate to θ is the tooth angle.

2. The method for machining the arc thread arc root according to claim 1, characterized in that: In step 1), the step angle when machining the tooth bottom arc is determined according to the following formula: Where Δβ is the step angle, R 刀 is the tool tip radius, R 底 R is the radius of the tooth bottom arc, z is the surface roughness.

3. The method for machining the arc thread arc root according to claim 1, characterized in that: The method for calculating the tool rotation angle of each cut during processing based on the step angle is as follows: if the absolute value of the difference between the offset of the next cutter rotation angle determined according to the current step angle in the radial feed direction of the turning tool and the offset of the current cutter rotation angle in the radial feed direction of the turning tool is greater than the absolute value of the maximum feed amount, then the step angle is redetermined based on the maximum feed amount, and the tool rotation angles of each cut after the current cut are calculated based on the redetermined step angle.

4. The method for machining the arc thread arc root according to claim 3, characterized in that: The method for re-determining the step angle according to the maximum feed amount is to calculate the step angle according to the following formula: Among them, Δβ′ is the re-determined step angle, β n is the tool rotation angle of the nth tool, the nth tool is the current tool, R 底 R is the radius of the tooth bottom arc, 刀 is the tool tip radius, X n is the X-direction offset of the tool position relative to the origin O, ΔX max is the maximum feed amount, X 底 is the X-direction offset of the center of the arc of the tooth bottom relative to the origin O, the origin O is the intersection of the tooth top and the symmetry axis of the tooth profile, the radial retraction direction of the turning tool is the positive X direction, the radial feed direction of the turning tool is the negative X direction, the positive direction of the angular momentum when the spindle rotates counterclockwise is the positive Z direction, and the negative direction of the angular momentum when the spindle rotates counterclockwise is the negative Z direction.

5. The method for machining the arc thread arc root according to claim 1, characterized in that: The tool tip radius must be greater than or equal to the minimum tool tip radius and less than or equal to the maximum tool tip radius; the maximum tool tip radius is the tooth bottom arc radius, and the minimum tool tip radius is the set multiple of the maximum tool tip radius, and the set multiple is greater than or equal to 1 / 3 and less than or equal to 1 / 2.

6. The method for machining the arc thread arc root according to claim 1, characterized in that: The offset coordinate of each cut when the tool moves is (X n , Z n ), X n and Z n Calculated according to the following formula: X n =X 底 -(R 底 -R 刀 )cos(β n ) Z n =(R 底 -R 刀 )sin(β n ) Among them, X n The X-direction offset of the tool position relative to the origin O, Z n X is the Z-direction offset of the tool position relative to the origin O. 底 R is the X-direction offset of the center of the tooth bottom arc relative to the origin O, 底 R is the radius of the tooth bottom arc, 刀 is the tool tip radius, β n is the tool rotation angle of the nth tool, the origin O is the intersection of the tooth top and the tooth profile symmetry axis, the radial retraction direction of the turning tool is the positive X direction, the radial feed direction of the turning tool is the negative X direction, the positive direction of the angular momentum when the spindle rotates counterclockwise is the positive Z direction, and the negative direction of the angular momentum when the spindle rotates counterclockwise is the negative Z direction.

7. The method for machining the arc thread arc root according to claim 6, characterized in that: X 底 Calculated according to the following formula: X 底 =R 底 -H Among them, H is the tooth height.

8. The method for machining the arc thread arc root according to claim 1, characterized in that: In step 2), the tool rotation angle of each cut is equal to the tool rotation angle of the previous cut minus the step angle of the current layer.

9. The method for machining the arc thread arc root according to claim 1, characterized in that: The tool rotates counterclockwise during machining.

10. A circular thread arc root processing device, comprising a processor, characterized in that: The processor is used to execute computer program instructions to implement the method for processing the arc thread arc root as described in any one of claims 1-9.

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