Machining method of high-precision helical surface

Abstract

The invention provides a method for machining a high-precision helical surface, which belongs to the technical field of machining, and comprises the following steps of: machining a side edge of a milling cutter, moving the cutter along with the trajectory of the helical surface, roughly machining the helical surface with the allowance of 0.8-1.5 mm, and finely machining the helical surface on a numerical control milling machine. According to the invention, high-precision large-pitch helical surface processing can be realized.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, and in particular relates to a method for machining high-precision helical surfaces. Background Technology

[0002] In existing technologies, some landing gear cam components have a helical surface structure. The helical surface is the mating surface, requiring the mating area of ​​the upper and lower cams to be no less than 75%, with a surface roughness of Ra 0.8. When the pitch is large, such as a cam structure pitch of 160mm (e.g.) Figure 1 As shown, if the helical surface is machined using the bottom edge of a milling cutter, the tool overhang is too large, and chatter is likely to occur during machining. Furthermore, due to tool diameter interference, there will be overcutting and residue in the machining of the helical surface, making it impossible to match the theoretical contour. The large surface error after machining the helical surface can easily lead to clearance in the cam fit, affecting the function of the component.

[0003] Therefore, a method for machining high-precision, large-pitch helical surfaces is needed. Summary of the Invention

[0004] The technical problem to be solved by this invention is that chatter is prone to occur on the helical surface during processing, and there is overcutting and residue in the processing of the helical surface, which can easily lead to gaps in the cam fit.

[0005] The technical solution of this invention is: A high-precision machining method for helical surfaces involves using a milling cutter with its side edge for machining. The cutter moves along the trajectory of the helical surface. First, the helical surface is rough-machined with a allowance of 0.8~1.5mm, and then the helical surface is finished on a CNC milling machine.

[0006] The finishing process includes: Step 1. Calculate the infeed point coordinates. Determine the starting coordinates (x0, y0) of the helical surface based on the workpiece's external dimensions. Calculate the offsets Δx and Δy based on the tool radius and the actual infeed position to obtain the infeed point coordinates (x0+Δx, y0+Δy'). Step 2. Align the three-jaw chuck with the center of the machine tool table; Step 3. Remove the workpiece, determine the origin of the Z-axis coordinate of the workpiece, and set the tool length of the milling cutter used for finishing the helical surface; Step 4. Clamp the workpiece on the three-jaw chuck, making the end face of the workpiece flush with the bottom plane of the three-jaw chuck. Use a probe to flatten the two spiral blank surfaces of the workpiece and determine the X-axis and Y-axis directions of the workpiece coordinate system. Step 5. Raise the tool to a safe height, compensate for the machine tool tilt axis rotation offset, and rotate the machine tool A-axis to -90°. Step 6. Perform semi-finishing on the helical surface based on the linear and rotary motion of the machine tool; Step 7. During the finishing process, adjust the offset Δy to make the spiral surface size meet the preset requirements.

[0007] In step 1, when calculating the offsets Δx and Δy, assuming the diameter of the machining tool is d, the offsets Δx and Δy are: Δx = 0.5d * sinα, Δy = 0.5d * cosα, where α is the helix angle.

[0008] In step 2, the three-jaw chuck is installed in the center of the machine tool table, the workpiece is clamped on the three-jaw chuck, the end face of the workpiece is flush with the bottom plane of the three-jaw chuck, the probe is used to align the outer circle of the workpiece, and the position of the three-jaw chuck is finely adjusted until the center of the outer circle of the workpiece coincides with the center of the machine tool table. In step 3, the probe is used to align the bottom plane of the three-jaw chuck as the origin Z0 of the workpiece's Z-axis coordinate.

[0009] Specifically, step 6 includes: moving the tool to the infeed point, offsetting the theoretical infeed point size by 0.1 to 0.2 mm, keeping the machine tool X-axis stationary, using incremental mode to move the machine tool Y-axis to the required helical surface height size, and simultaneously rotating the machine tool C-axis to the required angle size of the helical surface to complete the semi-finishing of the helical surface.

[0010] Specifically, step 7 includes: lifting the tool to a safe plane, then moving the tool to the infeed point, keeping the machine tool's X-axis stationary, using incremental mode to move the machine tool's Y-axis to the required helical surface height, and simultaneously rotating the machine tool's C-axis to the required angle of the helical surface to complete the finishing of the helical surface.

[0011] The roughing of the helical surface is performed using a milling machine in conjunction with an indexing plate and gears.

[0012] The beneficial effects of this application are as follows: The process employs a milling cutter with its side cutting edge, where the tool follows the trajectory of the helical surface. Rough machining of the helical surface is performed first, leaving a margin of 0.8~1.5mm, followed by finish machining on a CNC milling machine. This method enables the machining of high-precision, large-pitch helical surfaces. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the workpiece; Figure 2 This is a schematic diagram of the decomposition of the spiral trajectory; Figure 3 A schematic diagram is established for the coordinate system of the workpiece to be processed; Figure 4 This is a schematic diagram of the tool machining trajectory. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0016] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited from each other.

[0017] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] To ensure the machining accuracy and surface quality of the helical surface of the parts, this invention proposes a practical and effective method for machining high-precision, large-pitch helical surfaces.

[0019] In order to provide a high-precision machining method for helical surfaces in this embodiment of the invention, it is necessary to first determine the tool offset and machining error. The specific determination process is as follows: 1) Decompose the helical trajectory of the cutting tool into a linear trajectory and a rotary trajectory. Helical surface machining can simplify two-axis linkage with one linear motion and one rotary motion, such as... Figure 2 As shown.

[0020] 2) Establish the coordinate system of the workpiece to be processed. Use the cylinder axis as the Y-axis, the straight line direction of the cylinder as the X-axis, and the origin as the center of the end face of the workpiece to be processed, as follows: Figure 3 As shown.

[0021] 3) Calculate the offset coordinates of the starting tool. The machining trajectory is as follows: Figure 4 As shown. Let the diameter of the machining tool be d, then the theoretical offset Δx of the X-axis and the theoretical offset Δy of the Y-axis are: Δx=0.5d*sinα Δy=0.5d*cosα Where α is the helix angle.

[0022] In actual programming, to prevent overcutting at the starting point, the starting point is not necessarily the starting point of the helix; instead, the tool is usually placed in the avoidance zone. Therefore, the Y-axis offset calculation must also consider the tool placement position. Assuming the C-axis (machine tool table) rotates by β degrees (0~360°) to the tool placement position, the actual Y-axis offset y is: Δy'=0.5d*cosα+βP / 360 4) Calculate the actual machining error. The main factor affecting the accuracy of the helical surface profile is the X-axis offset, while the Y-axis offset affects the positional dimensions of the helical surface. The X-axis offset is affected by the helix angle of the helical surface. Due to the difference between the major and minor diameters of the helical surface, let the major and minor diameters be D1 and D2, respectively. Then, the deviation value δX between the major and minor diameters of the helical surface is:

[0023] Where P is the pitch.

[0024] To reduce theoretical errors, the mean diameter D of the helix surface is used as the calculated value for the helix angle. However, this results in residual helix at the major diameter position and overcutting at the minor diameter position. Figure 1 Parameter calculations, from the above formula, yield the maximum residual value and the maximum overcut value along the X-axis: δX 1max ≈0.0093dδX 2max ≈-0.010d, Unlike conventional machining methods that directly machine the helical surface on a CNC milling machine using the bottom edge of a milling cutter, which results in a small contact area and low surface roughness, this invention uses the side edge of a milling cutter for machining. The cutter moves along the trajectory of the helical surface, thus... Figure 3 Taking the workpiece shown as an example, the processing method includes the following steps: First, rough machining of the helical surface is performed using a conventional milling machine with an indexing plate and gears, leaving a margin of 0.8~1.5mm. Then, finish machining of the helical surface is performed on a CNC milling machine.

[0025] For the rough machining process, please refer to relevant technologies.

[0026] The finishing process is as follows: 1. Calculate the infeed point coordinates. Determine the starting coordinates (x0, y0) of the helical surface based on the workpiece's external dimensions. Calculate the offsets Δx and Δy based on the tool radius and the actual infeed position, thus obtaining the infeed point coordinates (x0+Δx, y0+Δy'). The offsets Δx and Δy are calculated as follows: Assuming the machining tool diameter is d, the offsets Δx and Δy are: Δx = 0.5d*sinα, Δy = 0.5d*cosα, where α is the helix angle.

[0027] 2. Before processing, install the three-jaw chuck in the center of the machine tool table, clamp the workpiece on the three-jaw chuck, and make sure the end face of the workpiece is flush with the bottom plane of the three-jaw chuck. Use a probe to align the outer circle of the workpiece and fine-tune the position of the three-jaw chuck until the center of the outer circle of the workpiece coincides with the center of the machine tool table. 3. Remove the workpiece, use the probe to align the bottom plane of the three-jaw chuck as the origin Z0 of the workpiece's Z-axis coordinate, and set the cutter length of the milling cutter used for finishing the helical surface; 4. Clamp the workpiece on the three-jaw chuck, with the end face of the workpiece flush with the bottom plane of the three-jaw chuck. Use a probe to flatten the two spiral blank surfaces of the workpiece, thereby determining the X-axis and Y-axis directions of the workpiece coordinate system. 5. Call the program, select the workpiece coordinate system, raise the tool to a safe height, enable the tool center point management TCPM function to compensate for the machine tool tilt axis rotation offset, and rotate the A-axis to -90°. 6. Move the tool to the infeed point, offsetting the theoretical infeed point size by 0.1 to 0.2 mm. Keep the machine tool X-axis stationary and use incremental mode to move the machine tool Y-axis to the required helical surface height size. At the same time, rotate the C-axis to the required angle size of the helical surface to complete the semi-finishing of the helical surface. 7. After lifting the tool to the safe plane, move the tool to the infeed point. Keep the X-axis of the machine tool stationary and use incremental mode to move the Y-axis of the machine tool to the required height of the helical surface. At the same time, rotate the C-axis to the required angle of the helical surface to complete the finishing of the helical surface.

[0028] In one embodiment, the present invention is implemented as follows: 1) Complete part clamping and establish coordinate system; 2) Machining the helical surface of the cam using a C40U CNC machine; 3) Select D10R0 cutting tools; 4) The starting point of the spiral surface is 45mm from the end face; other parameters are as follows: Figure 1 As shown, The specific processing procedure can be as follows: N1T4 L6 / / Tool Selection N2G90 G54 G17 X0 Y0 Z+200 / / Run to safe plane N3M3 S650 / / Spindle rotation N4M8 / / Cutting fluid on N5G90 G01 X0 Y+100 Z+200 A+0 C+0 / / Part runs to initial state N6M128 F400 / / Enable TCPM mode N7G01 A-90 F400 / / A-axis rotation N8M129 / / Reset M128 N9G01 G91 X+2.58 Y+148.06Z-50 C+6 / / Move to the tool entry point, X=2.58, Y=51.94 N10G01 Z-5.6 F160 / / Downward cut N11G01 Y-77.333 C+174 / / Spiral surface machining N12G01 X-5.16 / / Move to the next helical surface machining start point N13G01 Y+77.333 C+174 / / Spiral surface machining N14G01 X+5.16 C+12 / / Move to retraction point N15G0 Z+100 / / Retract the blade N16G90 G01 X0 Y+100 Z+200 / / Move to safe plane N17G01 A0 C0 F400 / / Rotary shaft returns to zero N18M30 / / Program End The above description merely illustrates embodiments of the present invention and is quite specific and detailed; however, it should not be construed as limiting the scope of the patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Furthermore, any parts of the present invention not described in detail are conventional techniques.

Claims

1. A method for machining a high-precision helical surface, characterized in that, The helical surface is first roughed using a milling cutter with a side cutting edge, and the tool moves along the trajectory of the helical surface. The roughing is then performed on the helical surface with a margin of 0.8~1.5mm, and the finishing is then performed on a CNC milling machine.

2. The method as described in claim 1, characterized in that, The finishing process includes: Step 1. Calculate the infeed point coordinates. Determine the starting coordinates (x0, y0) of the helical surface based on the workpiece's external dimensions. Calculate the offsets Δx and Δy based on the tool radius and the actual infeed position to obtain the infeed point coordinates (x0+Δx, y0+Δy'). Step 2. Align the three-jaw chuck with the center of the machine tool table; Step 3. Remove the workpiece, determine the origin of the Z-axis coordinate of the workpiece, and set the tool length of the milling cutter used for finishing the helical surface; Step 4. Clamp the workpiece on the three-jaw chuck, making the end face of the workpiece flush with the bottom plane of the three-jaw chuck. Use a probe to flatten the two spiral blank surfaces of the workpiece and determine the X-axis and Y-axis directions of the workpiece coordinate system. Step 5. Raise the tool to a safe height, compensate for the machine tool tilt axis rotation offset, and rotate the machine tool A-axis to -90°. Step 6. Perform semi-finishing on the helical surface based on the linear and rotary motion of the machine tool; Step 7. During the finishing process, the offset Δy is adjusted to ensure that the dimensions of the spiral surface meet the preset requirements.

3. The method as described in claim 1, characterized in that, In step 1, when calculating the offsets Δx and Δy, let the diameter of the machining tool be d. Then the offsets Δx and Δy are: Δx = 0.5d * sinα, Δy = 0.5d * cosα, where α is the helix angle.

4. The method as described in claim 1, characterized in that, In step 2, install the three-jaw chuck in the center of the machine tool table, clamp the workpiece on the three-jaw chuck, and make sure the end face of the workpiece is flush with the bottom plane of the three-jaw chuck. Use a probe to align the outer circle of the workpiece and fine-tune the position of the three-jaw chuck until the center of the outer circle of the workpiece coincides with the center of the machine tool table.

5. The method as described in claim 1, characterized in that, In step 3, the probe is used to align the bottom plane of the three-jaw chuck as the origin Z0 of the workpiece's Z-axis coordinate.

6. The method as described in claim 1, characterized in that, Step 6 specifically includes: moving the tool to the infeed point, offsetting the theoretical size of the infeed point by 0.1 to 0.2 mm, keeping the X-axis of the machine tool stationary, using incremental mode to move the Y-axis of the machine tool to the required height of the helical surface, and at the same time rotating the C-axis of the machine tool to the required angle size of the helical surface, thus completing the semi-finishing of the helical surface.

7. The method as described in claim 1, characterized in that, Step 7 specifically includes: lifting the tool to a safe plane, then moving the tool to the infeed point, keeping the machine tool's X-axis stationary, using incremental mode to move the machine tool's Y-axis to the required helical surface height dimension, while simultaneously rotating the machine tool's C-axis to the required angle dimension of the helical surface, thus completing the finishing of the helical surface.

8. The method as described in claim 1, characterized in that, The helical surface is rough-machined using a milling machine in conjunction with an indexing plate and gears.

Images