Method for processing large-pitch fixed-start sawtooth internal thread

Abstract

The application discloses a processing method of a large-pitch fixed-start sawtooth internal thread, and comprises the following steps: positioning and clamping a workpiece on a workbench; fine boring of an inner hole and a reference surface A of a thread start size of the workpiece; drawing a cross line on an outer end surface with the inner hole axis as a center to determine a start line K; rotating a pick-up tool to make the pick-up tool coincide with the start line K to determine a pick-up point circumferential position; moving the pick-up tool to the workpiece outside, setting a tool setting sample plate in the inner hole, making a thread start size reference surface B of the tool setting sample plate adhere to the reference surface A, making a tool tip of the pick-up tool coincide with a tool setting mouth of the tool setting sample plate to determine an axial position of the pick-up point; and setting a numerical control processing program to perform cutting processing from the pick-up point position. The method is suitable for non-rotating body workpieces, can determine the thread pick-up point position at one time, does not need to repeatedly process the reference surface to ensure the start size precision, is simple in process, short in processing operation time, can effectively improve production efficiency, reduce manufacturing cost, and is beneficial to batch production.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, specifically relating to a machining method for a large-pitch, fixed-starting-point sawtooth internal thread. Background Technology

[0002] Machining large, non-rotating, high-pitch, sawtooth-shaped internal threads with a fixed starting point typically involves positioning, clamping, and aligning the part on a large horizontal lathe using a large, specialized lathe fixture. The machining method follows standard thread machining procedures, but a special measuring tool is used to determine the actual position of the thread's starting point. Based on the determined position, the starting thread dimension is then verified against a reference surface (surface A) to ensure the correct starting point size.

[0003] Its main drawbacks are: inconvenient clamping and difficulty in aligning parts; uncertain starting point position of the thread, requiring multiple measurements with specialized measuring tools and repeated machining of the reference surface for the thread starting point size to ensure the thread starting point size; low production efficiency, unsuitable for mass production. Furthermore, for example... Figure 1 and Figure 2 For large and complex non-rotating parts, when the thread start point dimension (L1) and other feature dimensions (K2) are on the same reference plane, existing manufacturing methods need to ensure the dimensions of other feature parts at the same time when determining the thread start point. If the dimensional accuracy of other feature parts is high, it will lead to difficulties in part processing or problems in ensuring the dimensional accuracy of other parts. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for machining a large-pitch, fixed-start-point sawtooth internal thread. This method first positions, clamps, and aligns the workpiece, then uses scribing and tool setting to determine the thread starting point position in one step. Finally, a CNC boring and milling machine is used to machine the large-pitch, fixed-start-point sawtooth internal thread. This method is suitable for non-rotating workpieces. During machining, there is no need to repeatedly machine the reference surface of the fixed starting point to ensure the accuracy of the starting point dimension, simplifying the machining process, improving the accuracy of the starting point position, shortening machining time and auxiliary time, effectively improving production efficiency, reducing manufacturing costs, and facilitating mass production.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for machining large-pitch, fixed-start-point sawtooth internal threads, applicable to the machining of non-rotating workpieces, includes the following steps:

[0007] S1. Position and clamp the workpiece to be processed on the worktable of the CNC boring and milling machine;

[0008] S2, the reference plane A for the inner hole and thread start dimensions of the precision boring workpiece;

[0009] S3. Draw a cross line on the outer end face of the workpiece with the axis of the inner hole after precision boring as the center, and take the vertical line in the cross line as the starting line K of the fixed starting thread.

[0010] S4. Rotate the pick-off tool on the spindle of the CNC boring and milling machine so that the tip of the pick-off tool coincides with the starting line K, and determine the circumferential position of the starting point;

[0011] S5. Move the pick-up knife axially to the outside of the workpiece, and set a tool setting template in the inner hole after precision boring. The thread starting point dimension reference surface B of the tool setting template is in contact with the thread starting point dimension reference surface A of the workpiece. Move the pick-up knife radially so that the tip of the pick-up knife matches the tool setting edge of the tool setting template, and determine the axial position of the starting point.

[0012] S6. Set the CNC machining program of the CNC boring and milling machine according to the design parameters of the sawtooth internal thread, and start thread cutting from the determined starting point.

[0013] In one embodiment of this application, the thread starting point dimension of the tool setting template is L, and the calculation formula is as follows:

[0014] L=L1-tanαⅹ(ΦD2-ΦD)÷2+np

[0015] Where L1 is the dimension from the reference plane A to any thread inspection point on the workpiece, α is the angle between the inclined surface of the sawtooth internal thread and the perpendicular to the thread axis, ΦD2 is the major diameter of the sawtooth internal thread, ΦD is the pitch diameter of the sawtooth internal thread, n is an integer multiple, and p is the pitch of the sawtooth internal thread.

[0016] The thread inspection point is the thread pitch diameter point directly below the sawtooth internal thread.

[0017] In one embodiment of this application, the L value of the tool setting template should be greater than the distance from the reference surface A to the outer end face of the inner hole of the workpiece.

[0018] In one embodiment of this application, step S1, positioning and clamping the workpiece to be processed on the worktable of a CNC boring and milling machine, specifically includes:

[0019] Place the workpiece to be processed on the worktable, use a dial indicator to align the inner hole, and use a pressure plate to press and fix the workpiece, controlling the runout to ≤0.05mm, thereby achieving the positioning and clamping of the workpiece.

[0020] In one embodiment of this application, the reference surface A for the inner hole and thread start dimensions of the precision-bored workpiece in S2 specifically includes:

[0021] The inner hole is machined to the size ΦD1 of the thread to be machined; the reference surface A is precision bored to ensure the dimensional accuracy of other feature parts at the other end of the inner hole.

[0022] In one embodiment of this application, the angle of the distal side bevel of the tool setting template is consistent with the angle of the outer side bevel of the sawtooth internal thread, and matches the angle of the hook-and-loop cutter. During tool setting, the tool setting edge and the tip of the hook-and-loop cutter are properly matched.

[0023] In one embodiment of this application, in step S6, thread cutting is performed using radial feed and uniform depth of cut.

[0024] In one embodiment of this application, the spindle speed of the CNC boring and milling machine is 10 r / min, the cutting depth per cut is 0.05 mm during roughing, and the cutting depth per cut is 0.025 mm during finishing.

[0025] In one embodiment of this application, the cutting speed of the pick cutter is 120 mm / min, the cutting depth per cut is 0.05 mm during roughing, and the cutting depth per cut is 0.025 mm during finishing.

[0026] Compared with the prior art, the beneficial effects of the present invention are:

[0027] 1. The machining method for large-pitch, fixed-starting-point sawtooth internal threads of the present invention first clamps, aligns, and fixes the workpiece on the worktable. The circumferential position of the starting point is determined by scribing. Then, the axial position of the starting point is determined using a dedicated tool setting template, thus achieving one-time determination of the thread starting point position. Finally, the machining is controlled by setting the CNC machining program of the CNC boring and milling machine. During the machining process, there is no need to repeatedly machine the reference surface of the fixed starting point to ensure the starting point dimension accuracy. This simplifies the machining process, improves the accuracy of the starting point position, shortens the machining time and auxiliary time, effectively improves production efficiency, reduces manufacturing costs, and is conducive to mass production.

[0028] 2. This method is applicable to the machining of sawtooth internal threads with a fixed starting point on non-rotating workpieces, especially for the machining of large and complex non-rotating workpieces. It does not require special lathe fixtures. The workpieces are placed on the worktable and aligned through the inner hole. The clamping and alignment are convenient, saving the cost of lathe fixtures and reducing the auxiliary time of repeatedly clamping and aligning the workpieces.

[0029] 3. Effectively ensures that the reference surface at the starting point of the thread and other feature parts are on the same reference surface, which addresses the issue of high precision requirements for the reference surface machining.

[0030] 4. The thread starting point dimension L of the tool setting template is easy to calculate, the tool setting template is simple to process, and the axial position of the starting point can be quickly determined by using the tool setting template. It has high precision and is easy to operate. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a front view structural diagram of the workpiece in the embodiment.

[0033] Figure 2 for Figure 1 A cross-sectional view of the starting point line K and an enlarged schematic diagram of the cross-sectional shape of the sawtooth internal thread.

[0034] Figure 3 This is a schematic diagram of the tool setting structure for the tool setting template and the tool picking mechanism.

[0035] Figure 4 This is a schematic diagram of the tool template.

[0036] Figure label:

[0037] 1. Pick the blade; 2. Set the blade template; 21. Set the blade edge. Detailed Implementation

[0038] In the following description, only certain exemplary embodiments are briefly described. As those skilled in the art will recognize, the described embodiments can be modified in various ways without departing from the spirit or scope of the embodiments of this application. Therefore, the drawings and description are considered to be exemplary in nature and not restrictive.

[0039] In the description of this invention, it should be understood that the terms "center," "length," "thickness," "upper," "lower," "vertical," "inner," "outer," "axial," "radial," "circumferential," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0041] This invention provides a method for machining a large-pitch, fixed-starting-point sawtooth internal thread, which is used for machining large-pitch, fixed-starting-point sawtooth internal threads on non-rotating workpieces.

[0042] by Figure 1 and Figure 2 The following is a detailed description of the sawtooth internal thread machining of a non-rotating workpiece as an example.

[0043] Among them, such as Figure 1 The image shown is a front view of the outer end face of the workpiece. Cross lines are drawn on the end face, and the vertical straight line is the starting line K.

[0044] Figure 2 for Figure 1 A cross-sectional structural diagram along the starting point line K, where the diameter of the inner hole to be machined is ΦD3; the common datum plane for other feature parts and the inner hole (threaded hole) is datum plane A; the diameter of the inner hole in the threaded state to be machined is ΦD1, that is, the minor diameter of the sawtooth internal thread is ΦD1; the pitch diameter of the sawtooth internal thread is ΦD; and the major diameter of the sawtooth internal thread is ΦD2.

[0045] The specific steps for machining sawtooth internal threads are as follows:

[0046] Step S1: Place the non-rotating workpiece to be processed on the worktable of the CNC boring and milling machine, use a dial indicator to align the inner hole ΦD3, and use a pressure plate to clamp and fix the aligned workpiece, controlling the runout to ≤0.05mm, so as to position and clamp the workpiece on the worktable.

[0047] Step S2: The reference surface A for the inner hole and thread start point dimensions of the precision boring workpiece.

[0048] Specifically, the original inner hole size ΦD3 of the workpiece is precision bored to the size ΦD1 of the thread to be machined, which is the minor diameter size ΦD1 of the sawtooth internal thread. Simultaneously, the common datum surface, datum surface A, is precision bored to the threaded hole and other feature parts at the other end of the inner hole. When precision boring this datum surface A, the dimensional accuracy of the other feature parts at the other end is ensured. If the dimensional requirement for other feature parts is K2, its size is controlled within the range of K2 ± 0.05 mm.

[0049] Step S3, as follows Figure 1 As shown, with the axis of the fine-bored inner hole as the center, that is, with the axis of the inner hole in the state of the thread to be machined as the center, the inner hole size is ΦD1; draw an upright cross line on the outer end face of the workpiece (i.e. the outer end face of the threaded hole), and take the vertical line in the cross line as the starting line K of the fixed starting point thread.

[0050] Step S4: Grind the pick-up cutter 1 into the required shape according to the grinding template, then install the pick-up cutter 1 on the spindle of the CNC boring and milling machine, move and rotate the pick-up cutter 1 so that the tip of the pick-up cutter 1 coincides with the starting line K, thereby determining the circumferential position of the starting point.

[0051] Step S5, as follows Figure 3 and Figure 4 As shown, the pick-up tool 1, after being circumferentially positioned, is axially moved to the outside of the workpiece. Then, a corresponding tool setting template 2 is set in the inner hole ΦD1 after precision boring, so that the thread starting point dimension reference surface B of the tool setting template 2 is closely fitted with the thread starting point dimension reference surface A of the workpiece. The pick-up tool 1 is moved radially along the inner hole (keeping the circumferential position unchanged) so that the tool setting edge 21 of the tool setting template 2 is aligned with the tip of the pick-up tool 1. This determines the axial position of the starting point, which includes the axial distance and axial direction.

[0052] In one implementation, such as Figure 3 and Figure 4 As shown, the angle of the distal side bevel of the tool setting template 21 (i.e., the bevel away from the workpiece or the bevel near the picker 1) is consistent with the angle of the outer side bevel of the sawtooth internal thread (i.e., the bevel near the end face of the threaded hole). The tip angle of the picker 1 matches the angle of the distal side bevel of the tool setting template 21. During tool setting, the tool setting template 21 and the tip of the picker 1 fit together through the bevel, so as to accurately position the picker 1 in the axial direction and make the positioning more precise.

[0053] Among them, the tool template 2 has different thread starting point size L according to the design parameters of different sawtooth internal threads.

[0054] Specifically, such as Figure 2 As shown, the thread starting point dimension L of the tool setting template 2 (i.e., the length from the thread starting point dimension reference plane B of the tool setting template to the tool setting edge) is calculated and determined according to the formula L=L1-tanαⅹ(ΦD2-ΦD)÷2+np.

[0055] Where L1 is the dimension from the reference plane A to any thread inspection point on the workpiece;

[0056] α is the angle between the inclined surface of the sawtooth internal thread and the surface perpendicular to the thread axis;

[0057] ΦD2 is the major diameter of the sawtooth internal thread;

[0058] ΦD is the pitch diameter of the sawtooth internal thread;

[0059] n is an integer multiple;

[0060] p is the pitch of the sawtooth internal thread.

[0061] L1 is determined according to the design requirements of the sawtooth internal thread; the thread inspection point is the thread pitch diameter point directly below the sawtooth internal thread, which is also the midpoint when the outer inclined surface of the sawtooth internal thread is directly below.

[0062] like Figure 2 As shown, in this embodiment, α is 4°.

[0063] When designing and fabricating the tool setting template 2, the thread starting point dimension L of the tool setting template 2 should be greater than the distance from the datum surface A to the inner hole / outer end face of the internal thread of the workpiece, that is, the n value should be greater than the actual number of turns of the internal thread to be machined. This ensures that the starting point is outside the inner hole of the workpiece, guaranteeing that the cutting process can be completed in one pass from the outside to the inside, with consistent machining direction and more stable and reliable accuracy.

[0064] Step S6: After tool setting is completed, remove tool setting template 2; according to the design parameters of the sawtooth internal thread, set the CNC machining program of the CNC boring and milling machine, and use the three-axis linkage of the CNC boring and milling machine to start the thread cutting machining at the determined starting point.

[0065] When performing thread cutting, a radial feed and uniform depth of cut are used. This effectively reduces the surface roughness of the sawtooth thread, minimizes crack formation, and improves machining accuracy.

[0066] In one embodiment, the workpiece material is high-strength alloy structural steel 35CrNi3Mo. The CNC machining program controls the spindle speed of the CNC boring and milling machine to 10 r / min, that is, the rotation speed of the pick-and-place tool 1 is 10 r / min; at the same time, the depth of cut 'a' is set for each roughing operation. p =0.05mm; depth of cut a during finishing. p =0.025mm.

[0067] Alternatively, the CNC machining program can be set to control the cutting speed of the pick-and-loop tool 1 to V. c =120mm / min; simultaneously, set the depth of cut a for each roughing operation. p =0.05mm; depth of cut a during finishing. p =0.025mm. Setting the above parameters for cutting can effectively avoid cracking of the sawtooth internal thread, ensuring that the machined sawtooth internal thread has high precision and low surface roughness.

[0068] During the sawtooth internal thread cutting process, a special tooth profile template and a special tooth profile template are used to check the thread tooth profile; a standard plug gauge is used to check the minor diameter of the thread; a special major diameter plug gauge is used to check the major diameter of the thread; a special composite gauge is used to check the thread pitch and the starting dimension of the thread, and whether the thread inspection point is perpendicular to the workpiece and directly below it on ΦD, that is, whether the thread inspection point is located at the thread pitch point directly below the sawtooth internal thread.

[0069] In summary, the processing method of this application allows for the one-time determination of the thread starting point position. During processing, there is no need to repeatedly machine the reference surface for determining the starting point to ensure dimensional accuracy, simplifying the processing technology, improving the accuracy of the starting point position, and shortening processing and auxiliary time. This effectively improves production efficiency, reduces manufacturing costs, and is beneficial for mass production. This method is suitable for machining sawtooth internal threads with a fixed starting point on non-rotating workpieces, especially large and complex non-rotating workpieces. It eliminates the need for dedicated lathe fixtures; the workpiece is placed on a worktable and aligned via the inner hole, making clamping and alignment convenient and saving on lathe fixture costs and reducing auxiliary time spent on repeated clamping and alignment. It effectively addresses the issue of high precision requirements for the reference surface when the thread starting reference surface and other feature parts are on the same reference surface. Furthermore, the calculation of the thread starting point dimension L of the tool setting template 2 is convenient, the machining of the tool setting template 2 is simple, and the axial position of the starting point can be quickly determined using the tool setting template 2 with high accuracy and ease of operation.

Claims

1. A method for machining a large-pitch, fixed-starting-point sawtooth internal thread, characterized in that, This method is applicable to the machining of non-rotating workpieces, where the thread starting reference plane and other feature parts of the workpiece share the same reference plane, and includes the following steps: S1. Position and clamp the workpiece to be processed on the worktable of the CNC boring and milling machine; S2, the reference surface A for the inner hole and thread starting dimensions of the precision boring workpiece; the dimension ΦD1 for machining the inner hole to the state of the thread to be machined; the precision boring reference surface A ensures the dimensional accuracy of other feature parts at the other end of the inner hole; the minor diameter dimension of the sawtooth internal thread is ΦD1; S3. Draw a cross line on the outer end face of the workpiece with the axis of the inner hole after precision boring as the center, and take the vertical line in the cross line as the starting line K of the fixed starting thread. S4. Rotate the pick-off tool on the spindle of the CNC boring and milling machine so that the tip of the pick-off tool coincides with the starting line K, and determine the circumferential position of the starting point; S5. Move the pick-up knife axially to the outside of the workpiece, and set a tool setting template in the inner hole after precision boring. The thread starting point dimension reference surface B of the tool setting template is in contact with the thread starting point dimension reference surface A of the workpiece. Move the pick-up knife radially so that the tip of the pick-up knife matches the tool setting edge of the tool setting template, and determine the axial position of the starting point. S6. Set the CNC machining program of the CNC boring and milling machine according to the design parameters of the sawtooth internal thread, and start thread cutting from the determined starting point position; The thread starting point dimension of the tool template is L, and the calculation formula is as follows: L=L1-tanα×(ΦD2-ΦD)÷2+np Where L1 is the dimension from the reference plane A to any thread inspection point on the workpiece, α is the angle between the inclined surface of the sawtooth internal thread and the perpendicular to the thread axis, ΦD2 is the major diameter of the sawtooth internal thread, ΦD is the pitch diameter of the sawtooth internal thread, n is an integer multiple, and p is the pitch of the sawtooth internal thread. The thread inspection point is the thread pitch diameter point directly below the sawtooth internal thread. The L value of the tool setting template is greater than the distance from the reference surface A to the outer end face of the inner hole of the workpiece.

2. The machining method for a large-pitch, fixed-starting-point sawtooth internal thread according to claim 1, characterized in that, In step S1, positioning and clamping the workpiece to be processed on the worktable of the CNC boring and milling machine specifically includes: Place the workpiece to be processed on the worktable, use a dial indicator to align the inner hole, and use a pressure plate to press and fix the workpiece, controlling the runout to ≤0.05mm, thereby achieving the positioning and clamping of the workpiece.

3. The machining method for a large-pitch, fixed-starting-point sawtooth internal thread according to claim 1, characterized in that, The angle of the distal side bevel of the blade-setting template is consistent with the angle of the outer side bevel of the sawtooth internal thread, and matches the angle of the tip of the pick-and-loop cutter. During blade setting, the blade-setting edge and the tip of the pick-and-loop cutter are adapted and matched.

4. The machining method for a large-pitch, fixed-starting-point sawtooth internal thread according to claim 1, characterized in that, In S6, thread cutting is performed using radial feed and uniform depth of cut.

5. The machining method for a large-pitch, fixed-starting-point sawtooth internal thread according to claim 4, characterized in that, The spindle speed of the CNC boring and milling machine is 10 r / min. The cutting depth per cut is 0.05 mm during roughing and 0.025 mm during finishing.

6. The machining method for a large-pitch, fixed-starting-point sawtooth internal thread according to claim 4, characterized in that, The cutting speed of the pick cutter is controlled at 120 mm / min, the cutting depth per cut is 0.05 mm during roughing, and the cutting depth per cut is 0.025 mm during finishing.

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