Large-pitch arc thread machining method and device

Abstract

The invention belongs to the technical field of thread machining, and particularly relates to a large-pitch arc thread machining method and device. The method comprises the following steps: determining an equivalent root width when an arc thread is equivalent to a trapezoid according to a tool nose radius and a thread angle of a tool; determining the equivalent crest width when the arc thread is equivalent to the trapezoid according to the radius of the tool nose, the actual tooth height and the thread angle of the tool; the actual tooth height serves as the equivalent tooth height when the arc thread is equivalent to the trapezoid; the equivalent tooth bottom width serves as the equivalent tool width when the tool is equivalent to the trapezoidal turning tool; setting a radial spacing, and determining the number of flank processing layers according to the equivalent tooth height; the tool nose positions of the adjacent layers of tools are controlled to be spaced by the radial distance in the radial feeding direction and spaced by the product of the radial distance and a half thread angle tangent value in the axial direction, and the offset coordinates of the tool noses of all the layers during tooth side machining are calculated through the equivalent tooth bottom width, the equivalent tooth crest width and the thread angle; layered machining is carried out on the tooth side according to the offset coordinates of each layer of tool nose, and the cutting force is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of thread processing, and particularly relates to a method and a device for processing large-pitch circular arc threads. 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. 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 uniform. It can effectively reduce the stress concentration when the thread is loaded and has good fatigue resistance. The patent discloses two arc thread structures with major thread diameters of 42 and 48, and the pitches are 6.35 and 8.5 respectively. The patent with authorization announcement number CN116877555B discloses a double-ended stud for connecting the root of wind turbine blades and a processing method thereof. The external thread of the thread section of the double-ended stud is an arc thread, and the nominal diameter d of the arc thread is 42 and 48. 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.

[0003] In traditional technology, a forming cutter with an arc bottom surface is generally used to process large pitch arc threads in a linear feed method, such as Figure 1 As shown. However, the linear feed method will cause the tool contact surface to become larger and larger, causing the tool force to gradually increase, and the tool needs a larger cutting force to process arc threads. This will cause the tool to vibrate when using ordinary tool bars to process arc threads, and the load on the tool, tool holder and machine tool when processing arc threads is much greater than that of ordinary threads, resulting in the arc thread depth limit being much smaller than that of ordinary threads when using ordinary thread machines to process internal arc threads. The ordinary thread machine may even stop and alarm due to excessive load. Therefore, it is necessary to customize special machine tools, tools and anti-vibration tool bars to process arc threads, which increases processing costs. Summary of the invention

[0004] The purpose of the present invention is to provide a method and device for machining large pitch arc threads, so as to solve the problem that a large cutting force is required when machining large pitch arc threads by using a forming cutter in a linear feed mode, resulting in increased machining costs.

[0005] In order to solve the above technical problems, the present invention provides a large pitch circular thread processing method, comprising: determining the equivalent tooth bottom width when the circular arc thread is equivalent to a trapezoid according to the tool tip radius and the tooth profile angle; determining the equivalent tooth top width when the circular arc thread is equivalent to a trapezoid according to the tool tip radius, the actual tooth height and the tooth profile angle; using the actual tooth height as the equivalent tooth height when the circular arc thread is equivalent to a trapezoid; using the equivalent tooth bottom width as the equivalent tool width when the tool is equivalent to a trapezoidal turning tool; the tool is a forming tool; setting the radial spacing, and determining the number of tooth side processing layers according to the equivalent tooth height; controlling the tool tip positions of adjacent layers to be spaced by the radial spacing in the radial feed direction and by the product of the radial spacing and the half tooth profile angle tangent in the axial direction, and using the equivalent tooth bottom width, the equivalent tooth top width and the tooth profile angle to calculate the tool tip offset coordinates of each layer when processing the tooth side; the axial direction is the direction of the lathe rotation axis; and layering the tooth side according to the tool tip offset coordinates of each layer.

[0006] Furthermore, the method for calculating the tool tip offset coordinates of each layer when machining the tooth side is as follows: first, the Z direction offset Z of the tool tip position of each layer relative to the origin O is calculated. n and the X-direction offset X of the tool tip relative to the origin O n , and then according to X n and Z n Determine the tool tip offset coordinates of each layer when machining the tooth side, X n and Z n The calculation formula is:

[0007] X n =-nΔX

[0008]

[0009] Where n is the nth layer of the tooth side processing layer; ΔX is the radial spacing, W′ 顶 is the equivalent crest width, W′ 底 is the equivalent tooth bottom width, θ is the tooth profile angle, 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.

[0010] Furthermore, according to the Z-direction offset Z of the tool tip position of each layer relative to the origin O n The maximum Z-direction offset distance ΔZ of the tool tip relative to the origin O max Determine the number of cutters per layer when machining the tooth side: If Z n <ΔZ max , then the number of knives per layer is 2, and the corresponding tool tip offset coordinate is (X n , Z n ) and (X n , -Zn ); otherwise, the number of knives per layer is 3, and the corresponding tool tip offset coordinate is (X n , Z n )、(X n ,0)、(X n , -Z n ).

[0011] Furthermore, the maximum Z-direction offset distance ΔZ of the tool tip relative to the origin O is max It is 0.5 times the equivalent tool width.

[0012] Furthermore, the equivalent crest width is calculated according to the following formula:

[0013]

[0014] Among them, W′ 顶 is the equivalent crest width, H is the actual tooth height, R 刀 is the tool tip radius, and θ is the tooth angle.

[0015] Furthermore, the equivalent tooth bottom width is calculated according to the following formula:

[0016]

[0017] Among them, W′ 底 is the equivalent tooth bottom width, R 刀 is the tool tip radius, and θ is the tooth angle.

[0018] Furthermore, the radial spacing is based on the maximum feed amount ΔX max Make your selection:

[0019] ΔX≤ΔX max

[0020]

[0021] Among them, R 刀 is the tool tip radius, and θ is the tooth angle.

[0022] Furthermore, the number of tooth side machining layers is calculated according to the following formula:

[0023]

[0024] Among them, N is the number of tooth side processing layers, H′ is the equivalent tooth height, and ΔX is the radial spacing.

[0025] Furthermore, after machining the tooth side, the tool movement is controlled by using (-H, 0) as the tool tip offset coordinate to complete the machining of the tooth bottom and tooth top of the large pitch arc thread; H is the actual tooth height.

[0026] The beneficial effects of the above technical solution are as follows: the present invention is a pioneering invention, which performs profiling based on the principle of cutting processing with the left and right edges of a trapezoidal turning tool, calculates the equivalent tool width when the forming tool is equivalent to a trapezoidal turning tool, and the equivalent tooth height, equivalent tooth top width and equivalent tooth top height when the arc thread is equivalent to a trapezoid, sets the radial spacing, determines the number of processing layers of the arc thread tooth side after being equivalent to the trapezoid based on the set radial spacing and equivalent tooth height, controls the tool to decrease in the radial feed direction at intervals of the radial spacing and in the axial direction at intervals of the product of the radial spacing and the half tooth profile angle tangent value, calculates the offset coordinates of each layer based on the above equivalent parameters, and adjusts the circle according to the offset coordinates. The tooth side of the arc thread is processed in layers. When the forming cutter processes the tooth side of the arc thread, it no longer uses radial linear feed for processing, but feeds obliquely, and the blade side of the forming cutter is equivalent to the left and right blades of the trapezoidal turning tool to cut the tooth side, reducing the contact area between the tool and the tooth profile blank, so that the cutting force is greatly reduced, and the load of the tool, tool holder and machine tool is also greatly reduced. Therefore, there is no need to specially customize special machine tools, tools and anti-vibration tool bars to process arc threads. Ordinary thread machine tools can be used directly to process arc threads to obtain large-pitch arc threads that meet the thread processing depth, which greatly reduces the processing cost when using forming cutters to process large-pitch arc threads.

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

[0028] The beneficial effects of the above technical solution are as follows: the present invention is a pioneering invention, which performs profiling based on the principle of cutting processing with the left and right edges of a trapezoidal turning tool, calculates the equivalent tool width when the forming tool is equivalent to a trapezoidal turning tool, and the equivalent tooth height, equivalent tooth top width and equivalent tooth top height when the arc thread is equivalent to a trapezoid, sets the radial spacing, determines the number of processing layers of the arc thread tooth side after being equivalent to the trapezoid based on the set radial spacing and equivalent tooth height, controls the tool to decrease in the radial feed direction at intervals of the radial spacing and in the axial direction at intervals of the product of the radial spacing and the half tooth profile angle tangent value, calculates the offset coordinates of each layer based on the above equivalent parameters, and adjusts the circle according to the offset coordinates. The tooth side of the arc thread is processed in layers. When the forming cutter processes the tooth side of the arc thread, it no longer uses radial linear feed for processing, but feeds obliquely, and the blade side of the forming cutter is equivalent to the left and right blades of the trapezoidal turning tool to cut the tooth side, reducing the contact area between the tool and the tooth profile blank, so that the cutting force is greatly reduced, and the load of the tool, tool holder and machine tool is also greatly reduced. Therefore, there is no need to specially customize special machine tools, tools and anti-vibration tool bars to process arc threads. Ordinary thread machine tools can be used directly to process arc threads to obtain large-pitch arc threads that meet the thread processing depth, which greatly reduces the processing cost when using forming cutters to process large-pitch arc threads. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a linear feed of a forming cutter for processing arc threads in the prior art;

[0030] Figure 2 1. is a flowchart of machining large pitch arc threads according to an embodiment of the method of the present invention;

[0031] Figure 3 It is a schematic diagram of the tooth angle of a trapezoidal turning tool in the prior art;

[0032] Figure 4 is a geometric relationship diagram when calculating equivalent parameters in an embodiment of the method of the present invention;

[0033] Figure 5 is a geometric relationship diagram of calculating the maximum feed amount and the maximum offset distance of the tool tip position relative to the origin O in the Z direction in an embodiment of the method of the present invention;

[0034] Figure 6 The first layer of the method embodiment of the present invention is a tool path diagram of three cutters;

[0035] Figure 7 This is a tool path diagram of the first layer of the method embodiment of the present invention with 2 knives. DETAILED DESCRIPTION

[0036] 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.

[0037] The present invention uses a forming cutter to process large pitch circular arc threads, and the cutting method no longer uses a straight-line cutting method, but uses an oblique feeding method to make the blade side of the forming cutter equivalent to the left and right blades of a trapezoidal turning tool for cutting the tooth side. Considering that the circular arc thread forming cutter and the processed circular arc thread tooth side are both non-planar, the present invention refers to the principle of processing the tooth angle of the trapezoidal turning tool for profiling, designs the equivalent parameters of the circular arc thread forming cutter and the circular arc thread, calculates the offset coordinates of each layer based on the established equivalent parameters, and processes the thread layer by layer using the left and right cutting layered processing method according to the offset coordinates, thereby reducing the contact surface between the tool and the tooth blank, greatly reducing the cutting force, and greatly reducing the load of the tool, tool holder and machine tool, so that there is no need to specially customize special machine tools, tools and anti-vibration tool bars to process circular arc threads, and ordinary thread machine tools can be directly used to process circular arc threads to obtain large pitch circular arc threads that meet the thread processing depth, greatly reducing the processing cost when using forming cutters to process large pitch circular arc threads.

[0038] Method Embodiment

[0039] A large pitch arc thread processing method of the present invention, as Figure 2As shown, the specific process is as follows:

[0040] 1. Profiling is performed based on the principle of machining tooth profile angles with a trapezoidal turning tool. The equivalent tooth bottom width when the arc thread (i.e. the tooth profile to be machined) is equivalent to a trapezoid is determined according to the tool tip radius and tooth profile angle; the equivalent tooth top width when the arc thread is equivalent to a trapezoid is determined according to the tool tip radius, actual tooth height and tooth profile angle; the actual tooth height is used as the equivalent tooth height when the arc thread is equivalent to a trapezoid; the equivalent tooth bottom width is used as the equivalent tool width when the tool is equivalent to a trapezoidal turning tool.

[0041] When using a forming cutter as a tool to process a large pitch arc thread, since the bottom surface of the forming cutter is an arc, the bottom surface of the forming cutter and the processed arc thread tooth side are not flat, but the left and right two-edged cutting method requires knowing the bottom width of the tool (i.e. tool width), the bottom width of the tooth profile (i.e. tooth bottom width), tooth height and the top width of the tooth profile (i.e. tooth top width). In addition, since the trapezoidal turning tool in the prior art uses the left and right cutting method to process the tooth profile angle, such as Figure 3 As shown: the trapezoidal turning tool has three cutting edges, and the angle between the left and right cutting edges is equal to the tooth angle of the thread to be processed, which can conveniently process the tooth side while ensuring the roughness. Therefore, the present invention refers to the principle of processing the tooth side of the trapezoidal turning tool for profiling, and obtains the equivalent tool width W' 刀 , equivalent tooth bottom width W′ 底 , equivalent tooth height H′ and equivalent tooth crest width W′ 顶 .

[0042] Since it is a forming tool process, the equivalent tool width W' 刀 Equal to the equivalent tooth bottom width W′ 底 , the equivalent tooth height H′ is equal to the actual tooth height H of the tooth profile to be processed. 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 tool tip radius is R 刀 , the center of the arc at the bottom of the tooth is O 底 , according to Figure 4 The geometric relationship shown can be obtained:

[0043]

[0044] H′=H

[0045]

[0046] 2. Determine the radial spacing ΔX in the radial feed direction.

[0047] In order to reduce the cutting force, ΔX needs to be less than or equal to the maximum feed amount ΔX in the radial feed direction. max , according to ΔX max Select a suitable radial spacing ΔX, where ΔX refers to the absolute distance between the current layer tool tip position and the previous layer tool tip position in the radial feed direction. Figure 5 It can be seen that ΔX max The calculation formula is:

[0048]

[0049] ΔX≤ΔX max

[0050] 3. Calculate the maximum offset distance ΔZ of the tool tip relative to the origin O in the Z direction max .

[0051] ΔZ max =0.5W' 刀

[0052] 4. Determine the number of tooth side machining layers N based on the equivalent tooth height.

[0053]

[0054] Indicates rounding up.

[0055] 5. Calculate and control the tool tip positions of adjacent layers with radial spacing as the interval in the radial feed direction and with the product of radial spacing and half the tangent value of tooth profile angle as the interval in the axial direction, and use the equivalent tooth bottom width, equivalent tooth top width and tooth profile angle to calculate the tool tip offset coordinates of each layer when machining the tooth side; the axial direction is the direction of the lathe rotation axis, and the tool tip position decreases according to the corresponding intervals in the radial feed direction and the axial direction.

[0056] Among them, the method for calculating the tool tip offset coordinates of each layer when machining the tooth side is as follows: first, the tool tip position of each layer ( Figure 4 The Z-direction offset Z of point P in the image relative to the origin O n and the X-direction offset X of the tool tip relative to the origin O n , the calculation formula is:

[0057] X n =-nΔX

[0058]

[0059] Wherein, n is the nth layer of the tooth side processing layer.

[0060] Then, according to the Z-direction offset Z of the tool tip position of each layer relative to the origin O n The maximum Z-direction offset distance ΔZ of the tool tip relative to the origin Omax Determine the number of cutters per layer when machining the tooth side: If Z n <ΔZ max , then the number of knives per layer is 2, and the corresponding tool tip offset coordinate is (X n , Z n ) and (X n , -Z n ); otherwise, the number of knives per layer is 3, and the corresponding tool tip offset coordinate is (X n , Z n )、(X n ,0)、(X n , -Z n ).

[0061] 6. The tooth side of the large pitch arc thread is processed in layers according to the tool tip offset coordinates of each layer.

[0062] Taking the tool feed from right to left as an example, calculate the Z-direction offset Z1 of the first layer tool tip position relative to the origin O and the X-direction offset X1 of the first layer tool tip position relative to the origin O. If Z1 ≥ ΔZ max , then the tool tip offset coordinates of the first layer are (X1, Z1), (X1, 0) and (X1, -Z1), and the tool path is as follows: Figure 6 As shown: First, the first cut is processed with (X1, Z1) as the offset coordinate, then the second cut is processed with (X1, 0) as the offset coordinate, and finally the last cut is processed with (X1, -Z1) as the offset coordinate. At this point, the first layer is processed. max , then the tool tip offset coordinates of the first layer are (X1, Z1) and (X1, -Z1), and the tool path is as follows: Figure 7 As shown: First, the first cut is processed with (X1, Z1) as the offset coordinate, and finally the last cut is processed with (X1, -Z1) as the offset coordinate. At this point, the first layer is processed.

[0063] Then, the tool feed spacing ΔX in the X direction is used as the X-axis step, and the offset coordinates of the second layer are calculated in the above manner. The second layer is processed according to the offset coordinates of the second layer, and so on, until the Nth layer is processed.

[0064] 7. After processing the tooth side, use (-H, 0) as the tool tip offset coordinate to control the tool to perform the last cut, completing the processing of the tooth bottom and tooth top of the large pitch arc thread, thereby completing the large pitch arc thread processing.

[0065] Device Embodiment

[0066] A large pitch arc thread processing device of the present invention is used to execute computer program instructions to implement a large pitch arc thread processing method described in the above method embodiment. The device can be a CNC lathe for processing threads, and the lathe executes computer program instructions to control a forming cutter to process large pitch arc threads according to a large pitch arc thread processing method described in the method embodiment.

Claims

1. A method for machining a large pitch circular arc thread, characterized in that: include: Determine the equivalent tooth bottom width when the arc thread is equivalent to a trapezoid according to the tool nose radius and tooth profile angle; determine the equivalent tooth top width when the arc thread is equivalent to a trapezoid according to the tool nose radius, actual tooth height and tooth profile angle; use the actual tooth height as the equivalent tooth height when the arc thread is equivalent to a trapezoid; use the equivalent tooth bottom width as the equivalent tool width when the tool is equivalent to a trapezoidal turning tool; the tool is a forming tool; Set the radial spacing and determine the number of tooth side machining layers based on the equivalent tooth height; The tool tip positions of adjacent layers are controlled to be spaced by radial spacing in the radial feed direction and by the product of radial spacing and half of the tangent value of tooth profile angle in the axial direction, and the tool tip offset coordinates of each layer when machining tooth side are calculated using equivalent tooth bottom width, equivalent tooth top width and tooth profile angle; the axial direction is the direction of the lathe rotation axis; The tooth side is processed in layers according to the tool tip offset coordinates of each layer.

2. The method for machining large pitch circular arc threads according to claim 1, characterized in that: The method for calculating the tool tip offset coordinates of each layer when machining the tooth side is as follows: First, calculate the Z direction offset Z of the tool tip position of each layer relative to the origin O n and the X-direction offset X of the tool tip relative to the origin O n , and then according to X n and Z n Determine the tool tip offset coordinates of each layer when machining the tooth side, X n and Z n The calculation formula is: X n =-nΔX Where n is the nth layer of the tooth side processing layer; ΔX is the radial spacing, W′ 顶 is the equivalent crest width, W′ 底 is the equivalent tooth bottom width, θ is the tooth profile angle, 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.

3. The method for machining large pitch circular arc threads according to claim 2, characterized in that: According to the Z-direction offset Z of the tool tip position of each layer relative to the origin O n The maximum Z-direction offset distance ΔZ of the tool tip relative to the origin O max Determine the number of cutters per layer when machining the tooth side: If Z n <ΔZ max , then the number of knives per layer is 2, and the corresponding tool tip offset coordinate is (X n , Z n ) and (X n , -Z n ); otherwise, the number of knives per layer is 3, and the corresponding tool tip offset coordinate is (X n , Z n )、(X n ,0)、(X n , -Z n ).

4. The method for machining a large pitch circular arc thread according to claim 3, characterized in that: The maximum offset distance ΔZ of the tool tip relative to the origin O in the Z direction max It is 0.5 times the equivalent tool width.

5. The method for machining large pitch circular arc threads according to claim 1, characterized in that: Calculate the equivalent crest width according to the following formula: Among them, W′ 顶 is the equivalent crest width, H is the actual tooth height, R 刀 is the tool tip radius, and θ is the tooth angle.

6. The method for machining large pitch circular arc threads according to claim 1, characterized in that: Calculate the equivalent tooth bottom width according to the following formula: Among them, W′ 底 is the equivalent tooth bottom width, R 刀 is the tool tip radius, and θ is the tooth angle.

7. The method for machining large pitch circular arc threads according to claim 1, characterized in that: The radial spacing is based on the maximum feed amount ΔX max Make your selection: ΔX≤ΔX max Among them, R 刀 is the tool tip radius, and θ is the tooth angle.

8. The method for machining large pitch circular arc threads according to claim 1, characterized in that: Calculate the number of tooth side machining layers according to the following formula: Where N is the number of tooth side machining layers, H ′ is the equivalent tooth height, ΔX is the radial spacing.

9. The method for machining large pitch circular arc threads according to claim 1, characterized in that: After machining the tooth side, the tool movement is controlled with (-H, 0) as the tool tip offset coordinate to complete the machining of the tooth bottom and tooth top of the large pitch arc thread; H is the actual tooth height.

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

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