Composite super-precision machining method and machining jig

Abstract

The application discloses a composite super-precision machining method and a machining jig, and is used for machining micro workpieces with mirror surfaces, haze surfaces and cylindrical surfaces. The method comprises the following steps: loading a workpiece rough blank into a CNC machining jig, milling an end surface and reserving a turning allowance in a mirror surface area; after adjusting the workpiece special-shaped surface edge to be flush with the jig pre-machining profile under a high-power microscope, performing sand blasting treatment on the exposed part of the workpiece to form a haze surface; then, transferring the workpiece to a super-precision turning clamp, stacking a mirror surface turning steady state by using a composite included angle formed by the clamp and a suction cup, and performing super-precision turning according to the reserved allowance. The application further provides a CNC machining jig and a super-precision turning clamp for realizing the above method. The application completely avoids sputtering damage of haze surface machining to the mirror surface area, is stable in size control, is good in product consistency, greatly reduces the scrap rate, significantly shortens the machining time of a single piece, and is suitable for batch production of micro composite surface precision workpieces.

Description

Technical Field

[0001] This invention relates to the field of workpiece surface processing technology, and in particular to a composite ultra-precision turning method and processing fixture. Background Technology

[0002] In the field of machining micro-precision components, it is often necessary to perform composite machining of multiple different surface properties on the same workpiece. (See attached image) Figure 1 As shown, the target workpiece of this invention is a miniature circular needle with a diameter of approximately Φ1mm. Its key end features include: a surface (surface a) that needs to achieve an ultra-precision machined mirror finish, a surface (surface b) that needs to have a uniformly atomized texture, and a cylindrical surface (surface c) that is not allowed to have any atomized contamination. Among them, the mirror surface, the atomized surface, and the cylindrical surface are in a compound angle relationship, which brings great challenges to the machining process.

[0003] Currently, EDM (Electrical Discharge Machining) is widely used in the industry to create a matte finish on such workpieces. However, this existing technology has several insurmountable drawbacks. First, the high-temperature discharge generated during EDM can cause metal molten sputtering, forming deep sputtering cracks and recast layers on the workpiece surface. This is especially problematic in areas requiring subsequent mirror finishing (surface a), leaving microscopic damage that cannot be completely eliminated by subsequent processes, severely affecting the smoothness and integrity of the mirror finish. Second, EDM can easily blur the contours of fine structures such as minute angles and narrow planes, and round the edges, making it difficult to guarantee overall shape accuracy and control critical dimensions. Furthermore, due to the instability of the discharge process, the consistency of critical dimensions between different batches, and even between different workpieces within the same batch, is poor, resulting in a high product scrap rate, severely restricting production efficiency and cost control.

[0004] In view of the shortcomings of the existing technology, there is an urgent need in the field for a composite machining process that can achieve both high-precision mirror turning and uniform matte forming on the same workpiece without causing negative impacts on each other. Summary of the Invention

[0005] The purpose of this invention is to provide a composite ultra-precision turning method that can completely avoid sputtering damage to the workpiece mirror surface, and has stable dimensional control and low workpiece scrap rate.

[0006] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A composite ultra-precision turning method for machining workpieces with mirror, matte, and cylindrical surfaces includes the following steps: Step 1: Load the workpiece blank into the CNC machining fixture, so that the end of the workpiece protrudes to a predetermined height and the bottom is suspended in the air, and then fasten it with the side screws. Step 2: Mill the end face of the workpiece on CNC and reserve a turning allowance for ultra-precision turning in the mirror area of ​​the workpiece. Step 3: Loosen the side screws, adjust the workpiece under a high-powered microscope so that the edge of the irregular surface of the workpiece is flush with the pre-machined contour of the CNC machining fixture, and then tighten the screws again. Step 4: Place the CNC machining fixture containing the workpiece into the sandblasting machine and sandblast the exposed part of the workpiece to create a matte finish on the target surface. Step 5: Remove the sandblasted workpiece from the CNC machining fixture, clamp it individually into the ultra-precision turning fixture, and position and lock it by the bottom of the workpiece. Step 6: Install the ultra-precision turning fixture onto the ultra-precision turning chuck. Use the combined angle formed by the ultra-precision turning fixture and the ultra-precision turning chuck to stack the workpiece mirror surface to achieve a stable state for end-plane turning. Perform ultra-precision turning on the workpiece mirror surface according to the turning allowance reserved in Step 2 to complete the workpiece machining.

[0007] Furthermore, in step four, the sandblasting treatment uses 400# gravel, the sandblasting air pressure is 0.2MPa, the sandblasting exposure time is 10 seconds, and the spray angle is 30°~40°.

[0008] Furthermore, in step four, sandblasting is replaced by laser sandblasting.

[0009] Furthermore, in step two, the CNC milling uses a Φ0.2mm milling cutter.

[0010] Furthermore, in step six, the ultra-precision turning conditions are: spindle speed 1100 rpm, feed rate 0.2 mm / min, depth of cut 0.5 μm, and tool radius 0.05 mm.

[0011] Furthermore, the bottom surface of the ultra-precision turning fixture that contacts the ultra-precision turning suction cup forms a 10° angle with the cylindrical surface of the workpiece.

[0012] Furthermore, the CNC machining fixture can simultaneously clamp multiple workpieces for synchronous processing.

[0013] Furthermore, in step one, before loading the workpiece blank into the CNC machining fixture, the ends of the workpiece blank are first nickel-plated with a margin.

[0014] The present invention also provides a composite ultra-precision turning fixture for implementing the above-mentioned machining method, including a CNC machining fixture and an ultra-precision turning jig; the CNC machining fixture has a pre-machined contour for clamping the workpiece during milling and sandblasting, with the bottom of the workpiece suspended and secured by side screws; the ultra-precision turning jig is used to clamp the workpiece during ultra-precision turning of the sandblasted workpiece, with its bottom surface in contact with the ultra-precision turning suction cup forming a predetermined angle with the cylindrical surface of the workpiece to stack the workpiece mirror surface for end-plane turning in a stable state.

[0015] Existing technologies can no longer fully meet the requirements of the target workpiece. The bottleneck lies in ensuring the texture and size of the matte surface of the target workpiece while avoiding affecting other features of the target workpiece during the process. However, the processing method of the present invention completely avoids sputtering damage to the mirror surface when processing the target workpiece, and the size control is stable, the workpiece scrap rate drops sharply, and the process time is significantly reduced. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the target workpiece of the present invention; Figure 2 This is a schematic diagram of the CNC machining fixture structure of the present invention; Figure 3 This is a schematic diagram showing that the edge of the irregular surface of the target workpiece is flush with the pre-processed contour of the fixture. Figure 4 This is a schematic diagram of the ultra-precision machining fixture of the present invention; Figure 5-12 This is a schematic diagram of the processing steps in Example 1; Figure 13 The image shows the effect of the product prepared using the process of this invention; Figure 14 The image shows the effect of the product prepared using the existing process. Detailed Implementation

[0017] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, but this does not constitute a limitation on the scope of protection of the present invention.

[0018] See Figure 1-14 A composite ultra-precision turning method includes the following steps: 1. The target workpiece 1 is loaded into fixture 2 ( Figure 2 The workpiece and fixture form a limit at the bottom to prevent the target workpiece from rotating; this is achieved by screw 21 ( Figure 3 ) Locking; Measure the height of the target workpiece, set the machining allowance, and mill the end face using a Φ0.2mm milling cutter on a high-speed CNC machine; Mirror finish of the target workpiece ( Figure 1(a) In this section, a turning allowance needs to be reserved for precision turning; before loading the target workpiece into the CNC machining fixture, the end of the target workpiece is nickel plated and a allowance is left. After the end is nickel plated, the surface roughness of the mirror surface after ultra-precision turning can reach RMS 10 nm, and it is suitable for milling the fine structure of the target workpiece with a Φ0.2mm milling cutter on a high-speed CNC. 2. After the end face CNC machining is completed, loosen screw 21 ( Figure 2 Under a high-powered microscope, adjust the target workpiece so that the edge of the irregular surface of the target workpiece is flush with the pre-machined contour of the fixture (e.g., Figure 3 As shown in Table 1, the cylindrical surface of the target workpiece is shielded, and the exposed part of the target workpiece is sandblasted to a uniform mist surface in a sandblasting machine. The sandblasting conditions are shown in Table 1. 400# fine sand particles are used, and the erosion of the workpiece surface is less than 0.001mm. This can meet the mist surface requirements of the target workpiece, without losing the workpiece processing accuracy, and completely avoid irremovable cracks. Table 1

[0019] 3. The sandblasted target workpiece is then loaded into the ultra-precision turning fixture. Figure 4 The bottom of the workpiece is limited to prevent rotation; referring to the composite angle of the precision-machined surface of the target workpiece, the bottom surfaces of fixtures 31 and 32 (the surfaces that contact the ultra-precision machining suction cup 33) form a 10° angle with the cylindrical surface of the target workpiece 1, so as to superimpose an end plane that can be precision-machined; through screw 34 ( Figure 4 Clamps 31 and 32 are used to clamp the target workpiece. The clamps 31 and 32 are then secured to the ultra-precision turning chuck 33 by screws 35, and ultra-precision turning is performed. The precision turning conditions are shown in Table 2.

[0020] Table 2

[0021] Example 1 Reference Appendix Figure 5-12 A composite ultra-precision turning method includes the following steps: 1. Accepted materials are loaded into the CNC fixture. The area to be machined protrudes at least 2mm from the fixture surface. The workpiece hanger is ensured to be suspended in the air and secured with screws. Figure 5 As shown; 2. Using a UVM spindle at 26000 R / M and a Φ0.3 tool feed of F150, perform milling operations, such as... Figure 6 As shown; 3. Adjust the workpiece height so that only the surface to be sandblasted is exposed above the fixture surface, such as... Figure 7 As shown; 4. Apply protective medium to the remaining parts that do not require sandblasting, such as... Figure 8 As shown; 5. Spray with 400# gravel at a pressure of 0.2MPa for 10 seconds. Figure 9 As shown; 6. Mount the machine into the precision machining fixture and secure it with the side screws. Figure 10 As shown; 7. Secure the precision machining fixture to the suction cup base using the bottom screws. Figure 11 As shown; 8. The precision turning spindle speed is 1100 R / M. The target surface undergoes planetary motion around the spindle center. The scraping process of the target surface with an R0.05 diamond cutting tool exhibits a "lunar eclipse" phenomenon. Figure 12 As shown.

[0022] The time required for the process of this invention is compared with that of the original process, as shown in the table below:

[0023] It is evident that the invented process can significantly reduce the manufacturing time of a single workpiece and effectively improve efficiency.

[0024] Figure 13 The image shows the effect of a workpiece produced using the process of this invention (UVM + sandblasting + precision turning). The workpiece has: a uniform sandblasted surface with clear angular features; a smooth and complete contour on the precision-turned surface; and no blasting damage or gaps on the outer periphery of the precision-turned surface.

[0025] Figure 14 The image shows the effect of the workpiece produced by the original process (EDM + precision machining). The workpiece has: uneven sanding surface and obvious corner radius; irregular contour of precision machined surface; EDM damage and gaps on the outer periphery of precision machined surface (more than 90% of them exist, but only minor ones are selected).

[0026] As can be seen from the above comparison, the composite ultra-precision turning method of the present invention can effectively solve the problems existing in the prior art, and it takes less time and produces better quality products.

[0027] In summary, compared with the prior art, the present invention has the following beneficial effects: 1. Completely eliminate processing damage to the mirror area. This invention employs sandblasting (physical sandblasting or laser sandblasting) to replace traditional EDM (Electrical Discharge Machining) to achieve a matte finish on workpieces. During sandblasting, the abrasive particles only act on the exposed surface of the workpiece, completely avoiding the problems of molten sputtering, high-temperature heat-affected zones, and recast layers caused by EDM. This eliminates irreparable damage to the mirror-like area caused by sputtering cracks, providing a prerequisite for obtaining a complete mirror finish during subsequent ultra-precision turning.

[0028] 2. High machining precision, clear and complete microstructure. Before sandblasting, this invention first uses CNC milling to form the microstructure of the workpiece end face, and then uses a high-magnification microscope to precisely adjust the edges of the irregular surface of the workpiece to be flush with the pre-processed contour of the fixture, ensuring that the boundary of the sandblasting area is precisely controllable. Sandblasting uses 400# fine abrasive particles, and the erosion of the workpiece surface is less than 0.001mm. This creates a uniform matte effect without blurring or rounding key features such as fine angles and narrow planes, resulting in a clear overall outline and accurate dimensions of the workpiece.

[0029] 3. Good product consistency and significantly reduced scrap rate. This invention enables the simultaneous clamping and machining of multiple workpieces using CNC fixtures. Combined with precise positioning under a high-magnification microscope and standardized sandblasting and turning parameters, it effectively eliminates the problem of large dimensional differences between workpieces caused by fluctuations in discharge state in the EDM process. Practical verification shows that workpieces machined using this method have uniform sandblasted surfaces, clear angular features, smooth and complete precision-machined surface contours, stable finished product quality, and a significantly reduced scrap rate.

[0030] 4. Significantly reduces processing time per piece and improves production efficiency. Data comparing the processing times of the new and old processes show that the total processing time for a single piece using the method of this invention (UVM milling + sandblasting + ultra-precision turning) is 135 minutes, while the total processing time for a single piece using the existing EDM process (electrode machining + electrical discharge machining + precision turning + inspection) is 235 minutes. The processing time for a single piece using this invention is reduced by about 100 minutes, the efficiency is improved by more than 42%, and the manufacturing cost is significantly reduced, making it suitable for mass production.

[0031] 5. The ingenious fixture design enables ultra-precision turning on workpieces with complex angles. This invention addresses the structural characteristics of a workpiece where the mirror surface and cylindrical surface form a compound angle. It designs a dedicated ultra-precision turning fixture, which stacks a stable state that allows for end-plane turning of the mirror surface by means of a predetermined angle formed between the bottom surface of the fixture and the contact surface of the ultra-precision turning chuck. This makes ultra-precision turning, which was originally difficult to perform on workpieces with compound angles, feasible and expands the application scope of ultra-precision turning technology.

[0032] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A composite ultra-precision turning method for machining workpieces with mirror-like, matte, and cylindrical surfaces, characterized in that, Includes the following steps: Step 1: Load the workpiece blank into the CNC machining fixture, so that the end of the workpiece protrudes to a predetermined height and the bottom is suspended in the air, and then fasten it with the side screws. Step 2: Mill the end face of the workpiece on CNC and reserve a turning allowance for ultra-precision turning in the mirror area of ​​the workpiece. Step 3: Loosen the side screws, adjust the workpiece under a high-powered microscope so that the edge of the irregular surface of the workpiece is flush with the pre-machined contour of the CNC machining fixture, and then tighten the screws again. Step 4: Place the CNC machining fixture containing the workpiece into the sandblasting machine and sandblast the exposed part of the workpiece to create a matte finish on the target surface. Step 5: Remove the sandblasted workpiece from the CNC machining fixture, clamp it individually into the ultra-precision turning fixture, and position and lock it by the bottom of the workpiece. Step 6: Install the ultra-precision turning fixture onto the ultra-precision turning chuck. Use the combined angle formed by the ultra-precision turning fixture and the ultra-precision turning chuck to stack the workpiece mirror surface to achieve a stable state for end-plane turning. Perform ultra-precision turning on the workpiece mirror surface according to the turning allowance reserved in Step 2 to complete the workpiece machining.

2. The composite ultra-precision turning method according to claim 1, characterized in that, In step four, the sandblasting treatment uses 400# gravel, the sandblasting air pressure is 0.2MPa, the sandblasting exposure time is 10 seconds, and the spraying angle is 30°~40°.

3. The composite ultra-precision turning method according to claim 1, characterized in that, In step four, sandblasting is replaced by laser sandblasting.

4. The composite ultra-precision turning method according to claim 1, characterized in that, In step two, CNC milling is performed using a Φ0.2mm milling cutter.

5. The composite ultra-precision turning method according to claim 1, characterized in that, In step six, the ultra-precision turning conditions are: spindle speed 1100 rpm, feed rate 0.2 mm / min, depth of cut 0.5 μm, and tool radius 0.05 mm.

6. The composite ultra-precision turning method according to claim 1, characterized in that, The bottom surface of the ultra-precision turning fixture that contacts the ultra-precision turning suction cup forms a 10° angle with the cylindrical surface of the workpiece.

7. The composite ultra-precision turning method according to claim 1, characterized in that, The CNC machining fixture can clamp multiple workpieces simultaneously for synchronous processing.

8. The composite ultra-precision turning method according to claim 1, characterized in that, Before loading the workpiece blank into the CNC machining fixture in step one, the ends of the workpiece blank are nickel plated with a margin.

9. A composite ultra-precision turning fixture, used to implement the method according to any one of claims 1 to 8, characterized in that, It includes a CNC machining fixture and an ultra-precision turning fixture; the CNC machining fixture has a pre-machined contour and is used to clamp the workpiece during milling and sandblasting, with the bottom of the workpiece suspended and secured by side screws; the ultra-precision turning fixture is used to clamp the workpiece during ultra-precision turning after sandblasting, and its bottom surface forms a predetermined angle with the surface in contact with the ultra-precision turning chuck and the cylindrical surface of the workpiece to stack the workpiece mirror surface for end-plane turning in a stable state.

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