A cylindrical cam spiral groove machining method based on envelope shaping

Abstract

The present application belongs to the technical field of mechanical processing, and discloses a cylindrical cam helical groove machining method based on envelope forming, which improves the machining principle from passive "shape copying" to active "motion creation", and envelopes the shape of the target helical groove through accurate relative motion, thereby avoiding the approximation error of point contact and the interference problem of profile milling, and achieving high machining precision; the forming tool with the same width as the target helical groove is adopted, and the machining of the entire helical groove can be completed through single tool path, compared with the scanning milling which needs multiple tool paths, the machining path is greatly shortened, and the efficiency is improved by several times; the continuous tangent envelope cutting is stable and has little vibration, effectively eliminates "tool marks", and the tool heat dissipation condition is better than that of full blade width profile milling, thereby improving the part surface quality, reducing tool wear, prolonging the tool service life, realizing high-precision, high-efficiency and high-surface-quality machining of the cylindrical cam helical groove, and being suitable for high-precision and large-batch production.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, and in particular relates to a precision and efficient machining method for cylindrical cam helical grooves based on tool motion envelope forming. Background Technology

[0002] Cylindrical cam mechanisms are commonly used in mechanical design. The cam, as the driving element, performs continuous, constant-speed rotary motion, while the driven element can move according to any desired motion pattern. These mechanisms are widely used in various mechanical equipment, and the machining quality of the helical groove directly affects the mechanism's motion accuracy and service life. To ensure smooth, unimpeded movement of the cam mechanism, the normal cross-sections of the working surfaces on both sides of the cylindrical cam's helical groove should remain parallel to each other, and the upper and lower working sections of the helical groove must have equal width. Currently, cam helical groove machining typically employs two processes: multi-axis linkage interpolation milling or general-purpose form milling cutter profile milling.

[0003] Multi-axis linkage interpolation milling (scanning milling): Using ball end mills or end mills, the scanning motion of the tool "approaches" the preset 3D CAD model of the helical groove. It is a point contact or line contact machining process. In order to approximate the theoretical profile, extremely close tool step distances are required during the process. The tool path is long, the idle stroke is large, and the cutting efficiency is low. "Tool marks" are inevitably left during the milling process, resulting in large profile errors. Long tool overhang machining is prone to tool deformation, affecting the consistency of groove width. The tool side edge wears severely, and the cutting vibration leads to high surface roughness value, forming a work-hardened layer, which affects fatigue strength. General-purpose profile milling cutter: This method uses a milling cutter with the same width as the cam helical groove and achieves machining through single-axis or multi-axis interpolation. Although it improves cutting efficiency to some extent, the contact relationship between the tool and the workpiece on the helical surface is complex and prone to interference. Furthermore, the simultaneous participation of the entire cutting edge in cutting results in large cutting forces and poor heat dissipation. It places extremely high demands on the rigidity of the machine tool and the toughness of the tool, making it difficult to apply in high-precision applications.

[0004] Existing processes present a trade-off between tool life, machining accuracy, and efficiency. Therefore, it is necessary to develop a method that innovates from the machining principle level to achieve high-precision, high-efficiency, and high-surface-quality machining of spiral grooves. Summary of the Invention

[0005] The technical problem to be solved by this invention is the mutual constraint between accuracy, efficiency and tool life in the machining of cylindrical cam grooves.

[0006] To solve the above-mentioned technical problems, the specific technical solution of the present invention is as follows: A method for machining helical grooves in a cylindrical cam based on envelope forming includes the following machining steps. Step 1: Use a precision hydraulic collet or three-jaw chuck to clamp the cylindrical cam blank workpiece onto the turning spindle of the milling and turning machining center; Step 2: Use a dial indicator to perform radial and axial alignment to ensure that the workpiece axis coincides with the turning axis; Step 3: Mount the machining tool onto the milling spindle of the machining center via a hydraulic tool holder, and input the tool's geometric parameters and radius compensation into the machining center's CNC system; Step 4: Establish the tool-workpiece motion relationship: Based on the design parameters of the spiral groove, establish the relative motion mathematical relationship between the main motion and feed motion of the tool and the workpiece, and adjust the attitude of the milling spindle according to the helix angle β of the spiral groove to determine the spatial position relationship and motion trajectory between the tool axis and the workpiece axis. Step 5: Generate CNC machining program: Based on the tool-workpiece motion relationship established in step 4, a multi-axis linkage CNC machining program for mill-turn machining center is generated. The program includes motion commands for each axis, spindle speed, feed rate and coolant control parameters. Step 6, Envelope Milling: The machining program of the mill-turn machining center is started, and the tool and workpiece move relative to each other according to the preset program. The workpiece rotates at a constant speed, and the tool moves along a precise path coordinated with the spiral line of the workpiece under the linkage drive of the X and Z axes. By continuously controlling the position and attitude of the tool, it is made tangent to the groove wall at every cross-sectional position of the spiral groove to achieve dynamic envelope forming. At the same time, the cutting force and vibration are monitored in real time, and the process parameters are adjusted to ensure a stable cutting state. Step 7, Quality Inspection: After machining, the cross-sectional shape, surface roughness and dimensional accuracy of the spiral groove are detected by the online measurement system integrated into the machine tool. If there is a deviation, return to step 3 to modify the tool parameters for compensation machining.

[0007] Furthermore, the milling and turning machining center described in step 1 has X-axis and Z-axis linear axes, a turning spindle and a milling spindle, which can realize multi-axis linkage control.

[0008] Furthermore, the geometric parameters of the tool in step 3 include diameter, cutting length, and cutting width.

[0009] Furthermore, in step 3, based on the normal cross-sectional shape of the target spiral groove, a machining tool with a specific geometric profile is selected or customized, and its cutting edge shape is adapted to the theoretical cross-sectional shape of the spiral groove.

[0010] Furthermore, in step 4: The main motion is the uniform rotation of the workpiece. The feed motion is a linear motion that is synthesized by the X-axis and Z-axis interpolation and matched with the lead of the helix. The kinematic relationship between the main motion and the feed motion: for every revolution of the workpiece, the tool moves precisely one lead distance on the Z-axis; Posture adjustment: The milling spindle adjusts its angle according to the helix angle β to ensure that the working surface of the tool side cutting edge remains parallel and tangent to the side of the helical groove during the machining process, so as to achieve continuous envelope forming; Helix angle β: refers to the angle between the cutting at any point on the helix and the plane perpendicular to the helix axis, β=arctan(Ph / πd). Lead Ph: The distance the helix moves along the axis after rotating once around the axis; Diameter d: Diameter of the cam base circle.

[0011] This invention has the following advantages: it elevates the machining principle from passive "shape replication" to active "motion creation," using precisely controlled relative motion to envelop the shape of the target helical groove, avoiding the approximate error of point contact and the interference problem of contour milling, resulting in high machining accuracy; it employs a forming tool with the same width as the target helical groove, allowing the entire helical groove to be machined in a single pass, significantly shortening the machining path and increasing efficiency several times compared to scanning milling which requires multiple passes; continuous tangential envelope cutting is smooth and has low vibration, effectively eliminating "tool marks," and the tool's heat dissipation conditions are superior to full-width contour milling, improving the surface quality of the part while reducing tool wear and extending tool life, achieving high-precision, high-efficiency, and high-surface-quality machining of cylindrical cam helical grooves, suitable for high-precision, mass production. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a cylindrical cam structure; Figure 2 This is a schematic diagram of a milling and turning machining center. Figure 3 This is a schematic diagram of the helix angle; Figure 4 This is a schematic diagram of B-axis attitude adjustment; Figure 5 This is a structural diagram of the forming tool; Figure 6 A schematic diagram of a tool enveloping a spiral groove; The markings in the diagram are as follows: 1. Tool holder; 2. Milling cutter head. Detailed Implementation

[0013] To better understand the purpose, structure, and function of this invention, the invention will be described in further detail below with reference to the accompanying drawings.

[0014] This embodiment processes a rectangular helical groove for a right-handed cylindrical cam with a base circle diameter of 100mm, a lead of 200mm, a groove width of 20mm, and a radius of radius R2. The specific processing procedure is as follows: Step 1): Select a five-axis milling and turning machining center (e.g., Hardinge TU300S), equipped with a linear axis (with...). Figure 2 (X-axis, Z-axis), turning axis (with) Figure 2 C-axis), milling axis (with) Figure 2 The B-axis (center B-axis) enables five-axis simultaneous machining. Figure 2 In the middle: X-axis and Z-axis are the axes of linear motion; The C-axis, a rotary axis, is the turning spindle used to clamp workpieces and achieve precise indexing and continuous rotation. The swing axis B-axis is the milling spindle, used to mount tools and adjust their angle.

[0015] Step 2): Place the cylindrical cam workpiece (attached) Figure 1 Mounted on the turning spindle (with) Figure 2 The workpiece is placed on the hydraulic chuck of the C-axis and aligned with a dial indicator. The radial and axial runout is controlled within 0.01mm to ensure that the workpiece rotation axis coincides with the C-axis axis of the machine tool turning axis. Step 3): Select a slotting cutter with a cutting edge width that matches the normal cross-sectional shape of the target helical groove (see attached diagram). Figure 5 ).

[0016] The cutting edge shape of the milling cutter disc 2 is adapted to the theoretical cross-sectional shape of the spiral groove. In this embodiment, a forming groove milling cutter with a "rectangular shape with R2 fillet" is selected, with a cutting edge width of 20mm. The tool holder 1 is installed on the milling spindle through a high-rigidity hydraulic tool holder to ensure a firm clamping. At the same time, the precise geometric parameters of the tool (such as diameter, tool length, tool width, tool tip fillet radius, etc.) are input into the CNC system, and the corresponding tool radius compensation is set. Step 4): Establish the relative motion relationship between the tool and the workpiece; Main motion: The workpiece rotates at a constant speed; Linked motion: The X-axis and Z-axis perform interpolation motion, synthesizing a precise linear motion that matches the helical lead (200mm). The motion relationship is as follows: for every revolution of the workpiece (C-axis), the tool moves precisely one lead (200mm) in the X-axis direction; Helix angle (with) Figure 3 ): β=arctan(Ph / πd)=aretan(200 / π×100)=32.5°; Attitude adjustment: Rotate the B-axis by 32.5° to ensure that the side cutting surface of the tool remains parallel to the side of the spiral groove of the cylindrical cam workpiece during the machining process, thus achieving a tangential envelope; Step 5): CNC program generation. Based on the motion relationship established in Step 4, a multi-axis linkage CNC machining program is generated, including motion commands, process parameters, auxiliary functions and other machining parameter settings. Motion commands: Linkage commands for the X-axis, Z-axis, B-axis, and C-axis; Process parameters: workpiece (C-axis) speed, tool (B-axis) speed, feed rate, etc. Auxiliary functions: coolant switch, etc.

[0017] Step 6): Envelope milling: Start the machining program, the machine tool begins to move in tandem, the workpiece rotates, and the cutting tool starts from the end of the workpiece and performs continuous envelope milling along a helical path (see attached). Figure 6 Throughout the process, the position and orientation of the tool are precisely controlled by the CNC system, so that it is tangent to the spiral groove surface at every instant, dynamically enveloping the complete spiral groove shape. During the cutting process, the coolant provides sufficient cooling and lubrication, ensuring a stable cutting state.

[0018] Step 7): Quality inspection. After machining, the width of the spiral groove is inspected using the machine tool's integrated online measurement system. In this example, the groove width dimensional error is within 0.015mm, and there are no visible tool marks, meeting the technical requirements.

[0019] This embodiment breaks away from the traditional "groove shape replication" machining method and adopts reverse thinking to provide a cam helical groove machining method based on the "motion envelope forming" principle. This method constructs a precise "tool-workpiece" motion system and precisely controls the relative motion between the tool and workpiece, ensuring they remain tangent along a series of continuous contact lines. This dynamically "envelopes" the geometry of the target helical groove, successfully solving the problem of mutual constraints between accuracy, efficiency, and tool life in cylindrical cam groove machining, replacing traditional point-contact scanning or full-width profile milling.

[0020] Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art will be able to make various modifications and improvements without departing from the principles of the present invention, and these modifications and improvements should also be considered to fall within the scope of protection of the present invention.

Claims

1. A method for machining helical grooves in a cylindrical cam based on envelope forming, characterized in that, The processing steps include the following: Step 1: Use a precision hydraulic collet or three-jaw chuck to clamp the cylindrical cam blank workpiece onto the turning spindle of the milling and turning machining center; Step 2: Use a dial indicator to perform radial and axial alignment to ensure that the workpiece axis coincides with the turning axis; Step 3: Mount the machining tool onto the milling spindle of the machining center via a hydraulic tool holder, and input the tool's geometric parameters and radius compensation into the machining center's CNC system; Step 4: Establish the tool-workpiece motion relationship: Based on the design parameters of the spiral groove, establish the relative motion mathematical relationship between the main motion and feed motion of the tool and the workpiece, and adjust the attitude of the milling spindle according to the helix angle β of the spiral groove to determine the spatial position relationship and motion trajectory between the tool axis and the workpiece axis. Step 5: Generate CNC machining program: Based on the tool-workpiece motion relationship established in step 4, a multi-axis linkage CNC machining program for mill-turn machining center is generated. The program includes motion commands for each axis, spindle speed, feed rate and coolant control parameters. Step 6, Envelope Milling: The machining program of the mill-turn machining center is started, and the tool and workpiece move relative to each other according to the preset program. The workpiece rotates at a constant speed, and the tool moves along a precise path coordinated with the spiral line of the workpiece under the linkage drive of the X and Z axes. By continuously controlling the position and attitude of the tool, it is made tangent to the groove wall at every cross-sectional position of the spiral groove to achieve dynamic envelope forming. At the same time, the cutting force and vibration are monitored in real time, and the process parameters are adjusted to ensure a stable cutting state. Step 7, Quality Inspection: After machining, the cross-sectional shape, surface roughness and dimensional accuracy of the spiral groove are detected by the online measurement system integrated into the machine tool. If there is a deviation, return to step 3 to modify the tool parameters for compensation machining.

2. The method for machining helical grooves of a cylindrical cam based on envelope forming according to claim 1, characterized in that, The milling and turning machining center described in step 1 has X-axis and Z-axis linear axes, a turning spindle and a milling spindle, and can realize multi-axis linkage control.

3. The method for machining helical grooves of a cylindrical cam based on envelope forming according to claim 1, characterized in that, The geometric parameters of the tool in step 3 include diameter, cutting length, and cutting width.

4. The method for machining helical grooves of a cylindrical cam based on envelope forming according to claim 1, characterized in that, In step 3, based on the normal cross-sectional shape of the target spiral groove, a machining tool with a specific geometric profile is selected or customized, and its cutting edge shape is adapted to the theoretical cross-sectional shape of the spiral groove.

5. The method for machining helical grooves of a cylindrical cam based on envelope forming according to claim 1, characterized in that, In step 4: The main motion is the uniform rotation of the workpiece. The feed motion is a linear motion that is synthesized by the X-axis and Z-axis interpolation and matched with the lead of the helix. The kinematic relationship between the main motion and the feed motion: for every revolution of the workpiece, the tool moves precisely one lead distance on the Z-axis; Posture adjustment: The milling spindle adjusts its angle according to the helix angle β to ensure that the working surface of the tool side cutting edge remains parallel and tangent to the side of the helical groove during the machining process, so as to achieve continuous envelope forming; Helix angle β: refers to the angle between the cutting at any point on the helix and the plane perpendicular to the helix axis, β=arctan(Ph / πd). Lead Ph: The distance the helix moves along the axis after rotating once around the axis; Diameter d: Diameter of the cam base circle.

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