Arc milling and grinding compound tool suitable for fused quartz machining and preparation method

Abstract

The invention discloses a circular arc milling and grinding composite cutter suitable for fused quartz processing, the cutter comprises a T-shaped cutter bar and a milling and grinding cutter head, the milling and grinding cutter head is composed of a circular ring layer and a grinding material layer, the circular ring layer is made of PCBN (Polycrystalline Cubic Boron Nitride), and the grinding material layer is made of CBN (Cubic Boron Nitride); the diameter of the head part of the T-shaped cutter bar is the same as the inner diameter of the circular ring of the circular ring layer; the head of the T-shaped cutter bar is brazed on the inner surface of the circular ring layer; a plurality of micro blades with certain inclination angles are processed on the outer surface of the circular ring layer; the micro blade comprises a blade front groove, a front cutter face, a cutting blade and a rear cutter face, an abrasive layer is deposited on the rear cutter face, and the rear cutter face where the abrasive layer is deposited and the cutting blade are located on the same circumference. The depth of the compact layer in the ultra-precision grinding stage of the fused quartz can be controlled, and the completeness of the ultra-precision grinding surface and the subsequent polishing efficiency are improved.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision machining technology and relates to a circular arc milling composite tool, specifically a circular arc milling composite tool suitable for fused silica machining and its preparation method. Background Technology

[0002] Fused silica (FSC) material possesses excellent chemical stability, a low coefficient of thermal expansion, high light transmittance, and strong resistance to laser damage. Optical components made from FSC are widely used in important fields such as aerospace, semiconductors, optical communications, and microelectronics. Currently, ultra-precision grinding is one of the key technologies for processing medium- and large-diameter FSC optical components. However, the densification deformation behavior of FSC material during ultra-precision grinding affects the material's physical properties and service performance, exacerbates the formation of microcracks, and affects surface integrity, requiring subsequent polishing processes to remove them. Therefore, controlling the dense layer during the ultra-precision grinding stage is a crucial challenge that urgently needs to be addressed to improve the surface quality and subsequent polishing efficiency.

[0003] In recent years, to improve the surface integrity of fused silica in precision grinding, scholars both domestically and internationally have conducted a series of studies on the evolution of nano-scratching microstructure, improvement of grinding wheel structure, and optimization of process parameters. Research has found that the plastic deformation behavior of fused silica materials is divided into densification deformation and shear flow deformation. Shear flow deformation depends on densification deformation; that is, shear flow behavior only occurs when the material reaches a critical densification saturation. High temperatures can effectively reduce the critical densification saturation, and low-strain-rate behaviors such as increasing abrasive grain sharpness and reducing grinding speed can effectively reduce the depth of the dense layer. However, currently commonly used grinding tools are mostly grinding wheels with bonded abrasive grains with large negative rake angles, which do not meet the low strain-rate requirements and are prone to clogging during dry grinding (high temperature), exacerbating the depth of the dense layer. Therefore, it is necessary to develop an ultra-precision grinding tool that is resistant to high temperatures, facilitates chip removal, and has a small rake angle micro-edge. Summary of the Invention

[0004] In order to control the depth of the dense layer in the precision grinding stage of fused silica, improve the surface integrity of ultra-precision grinding and the efficiency of subsequent polishing, this invention provides a circular arc milling composite tool and its preparation method suitable for fused silica machining.

[0005] The objective of this invention is achieved through the following technical solution: A circular arc milling compound tool suitable for fused silica machining includes a T-shaped tool holder and a milling head, wherein: The milling cutter head is brazed onto the T-shaped cutter shank; The milling head consists of two parts: a ring layer and an abrasive layer. The ring layer is made of PCBN (polycrystalline cubic boron nitride), and the abrasive layer is made of CBN (cubic boron nitride). The overall diameter is 30~100mm and the thickness is 5~20mm. The head of the T-shaped tool holder is brazed to the inner surface of the annular layer; The T-shaped tool holder is made of cemented carbide, with a shank diameter of 10-25mm, a head diameter that is the same as the inner diameter of the annular layer, and a length of 50-120mm. The outer surface of the annular layer is machined with several micro-blades with a certain angle; The micro-blade includes a rake groove, a rake face, a cutting edge, and a flank face. An abrasive layer is deposited on the flank face, and the flank face with the abrasive layer deposited is on the same circumference as the cutting edge. The radial thickness of the annular layer is 8~15mm, and the axial thickness is 5~20mm; The number of micro-blades is 10 to 30; The width of the cutting edge groove is 2~5mm, the depth is 2~5mm, the inclination angle of the cutting edge is 30°~60°, the rake angle is -6°~6°, the clearance angle before the abrasive layer is deposited is 5°~10°, and the clearance angle after deposition and shaping is 0°. The thickness of the abrasive layer is 3~10mm, the abrasive is CBN cubic boron nitride abrasive with fine particle size of 3000# or higher, and the binder is metallic nickel or copper with high bonding strength.

[0006] A method for preparing the above-mentioned circular arc milling composite tool suitable for fused silica machining includes the following steps: Step 1: Welding the T-shaped tool holder head to the annular layer: The inner surface of the annular layer is welded to the T-shaped tool holder head using a brazing method to obtain a milling and grinding composite tool blank; Step 2, Laser shaping of the arc contour of the outer surface of the ring: The milling composite tool blank obtained in Step 1 is installed on the spindle of the XYZBC multi-axis linkage ultra-precision machine tool. The spindle drives the tool to rotate. A laser in-situ dressing system is set up. The laser beam is adjusted to be tangent to the circumferential direction of the tool, and the laser incident direction is parallel to the rotation direction of the tool. Excess material is removed layer by layer according to the predetermined trajectory to shape the arc contour feature. Step 3, Precision grinding of micro-edges: After step 2 is completed, without disassembling the tool, the dressing wheel is installed on the high-speed axis of the B turntable, and the front groove, front face, cutting edge and back face are dressed by XYZBC multi-axis linkage servo grinding to obtain a milling cutter with micro-edges. Step 4, Abrasive layer deposition: Abrasive is deposited on the surface of a milling cutter with micro-cutting edge by laser cladding or electroplating to obtain a milling-grinding composite tool blank with an abrasive layer; Step 5, Secondary Precision Grinding: Reinstall the milling composite tool blank with abrasive layer from Step 4 onto the spindle of the machine tool from Step 2, and use a GC bar to trim the arc contour until the cutting edge from Step 3 is exposed. Using the position of the cutting edge as a reference, grind the front groove according to the grinding method in Step 3.

[0007] Compared with the prior art, the present invention has the following advantages: (1) Effective control of the dense layer depth during fused silica precision grinding. Compared with traditional ultra-precision grinding wheels, high-strength and continuous PCBN polycrystalline cubic boron nitride micro-blades can remove fused silica material at low strain rates.

[0008] (2) Effectively improves the chip removal capacity and life of the cutting tool. The high-strength and continuous PCBN polycrystalline cubic boron nitride micro-edge plays a dominant cutting role, reducing the degree of clogging of the abrasive grains on the back face. The micro-edge with helical inclination and the front groove have a guiding effect, so that the chips are discharged from the cutting area along a fixed path, which is suitable for dry grinding and high-temperature machining conditions.

[0009] (3) Dressability of the micro-edge. Dressing only requires rotating the tool in the opposite direction to that used when machining the material, and grinding with a GC bar or Al2O3 dressing wheel to complete the dressing.

[0010] (4) It has the advantages of controllable cost and suitability for promotion in engineering. The tool with severe wear of the abrasive layer can still be recycled. By thinning the PCBN polycrystalline cubic boron nitride layer, a new milling composite tool can be obtained according to the preparation method described in this invention. The tool of this invention is not limited to fused silica material, but can also be applied to other amorphous hard and brittle materials with similar physical properties to fused silica. Attached Figure Description

[0011] Figure 1 A schematic diagram of a circular arc milling composite tool suitable for fused silica machining; Figure 2 Cross-sectional view and enlarged view of a circular arc milling composite tool suitable for fused silica machining; Figure 3 The preparation method of a circular arc milling composite tool suitable for fused silica processing includes: (a) welding the tool holder to a PCBN ring, (b) laser shaping of the circular arc profile, (c) precision grinding of the micro-blade, (d) electroplating deposition of CBN abrasive, (e) secondary precision grinding, (el) circular arc profile shaping, and (e2) micro-blade forming. In the figure, 1 is the T-shaped tool holder, 11 is the shank of the T-shaped tool holder, 12 is the head of the T-shaped tool holder, 2 is the milling cutter head, 21 is the PCBN polycrystalline cubic boron nitride annular layer, 22 is the CBN cubic boron nitride abrasive layer, 211 is the rake groove, 212 is the rake face, 213 is the cutting edge, 214 is the flank face before abrasive deposition, and 215 is the flank face after abrasive deposition. Detailed Implementation

[0012] The technical solution of the present invention will be further described below with reference to the accompanying drawings, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0013] This invention provides a circular arc milling composite tool suitable for fused silica machining, such as... Figure 1 and Figure 2 As shown, the cutting tool consists of a T-shaped tool holder 1 and a milling head 2. The milling head 2 comprises two parts: a PCBN polycrystalline cubic boron nitride annular layer 21 and a CBN cubic boron nitride abrasive layer 22. The overall diameter of the milling head 2 is Φ50mm, and the thickness is 10mm. The milling head 2 is brazed onto the cemented carbide T-shaped tool holder 1. The shank 11 of the T-shaped tool holder has a diameter of Φ20mm, the head 12 of the T-shaped tool holder 1 has a diameter of Φ30mm, and the overall length is 80mm. Due to the limited clamping diameter of the fixture and the limited radial thickness of the PCBN polycrystalline cubic boron nitride annular layer 21, the interior of the PCBN annular layer is compensated and filled by the tool holder head. First, several micro-cutting edges with a certain inclination angle are machined on the outer surface of the PCBN polycrystalline cubic boron nitride annular layer 21. The micro-cutting edges include a rake groove 211, a rake face 212, a cutting edge 213, and a flank face. Then, CBN abrasive is deposited on the outer surface of the PCBN polycrystalline cubic boron nitride annular layer 21 with micro-blades using laser cladding or electroplating. Excess CBN abrasive is further removed using laser processing or precision grinding technology, exposing the PCBN polycrystalline cubic boron nitride cutting groove 211, rake face 212, and cutting edge 213. Only the flank face is deposited with CBN abrasive. After processing, the flank face 215 with deposited abrasive is on the same circumference as the cutting edge 213. The grinding action of the abrasive layer attached to the flank face of the micro-blades softens the fused silica surface at high temperature. The continuous cutting edge on the micro-blades further removes the locally softened fused silica material, reducing the critical densification saturation of the fused silica during shear flow and the final densified layer depth, thus improving the subsurface grinding quality.

[0014] In this invention, the radial thickness of the PCBN polycrystalline cubic boron nitride annular layer 21 is 10 mm, and the axial thickness is 10 mm. There are 12 micro-blades; the width and depth of the rake groove 211 are 5 mm; the inclination angle of the cutting edge 213 is 45°; the rake angle is 0°; the clearance angle before depositing the CBN cubic boron nitride abrasive layer 22 is 8°; and the clearance angle after deposition and shaping is 0°. The CBN cubic boron nitride abrasive layer 22, deposited by laser cladding or electroplating, has a thickness of 10 mm. The abrasive is fine-grained CBN cubic boron nitride abrasive of 3000# or higher, and the binder is nickel or copper, which have high bonding strength.

[0015] A method for preparing the above-mentioned circular arc milling composite tool, such as... Figure 3 As shown, it includes the following steps: Step 1: Welding the T-shaped tool holder to the PCBN polycrystalline cubic boron nitride annular layer: Refer to... Figure 3 (a) The inner surface of the PCBN polycrystalline cubic boron nitride ring is welded to the cemented carbide T-shaped tool holder by brazing to obtain the original blank of the milling composite tool.

[0016] Step 2: Laser shaping of the arc contour of the outer surface of the PCBN polycrystalline cubic boron nitride ring: Refer to... Figure 3 (b) The original blank of the milling composite tool obtained in step 1 is installed on the spindle of the XYZBC multi-axis linkage ultra-precision machine tool equipped with a laser in-situ dressing system. The spindle drives the tool to rotate, and the laser beam is adjusted to be tangent to the circumferential direction of the tool. The laser incident direction is parallel to the rotation direction of the tool. Excess material is removed layer by layer according to the predetermined trajectory to shape the arc contour feature.

[0017] Step 3, Precision sharpening of the micro-blade: Refer to Figure 3 (c) After step 2 is completed, without disassembling the tool, the dressing wheel is installed on the high-speed axis of the B turntable. Through XYZBC multi-axis linkage servo grinding, the front groove, front face, cutting edge and back face are dressed to obtain a circular arc PCBN polycrystalline cubic boron nitride end mill with micro-cutting edge.

[0018] Step 4, CBN cubic boron nitride abrasive layer deposition: Refer to Figure 3 (d) Using the PCBN polycrystalline boron nitride end mill in step 3 as the cathode and the nickel plate as the anode, the CBN cubic boron nitride abrasive in the electroplating solution is electroplated and deposited on the surface of the end mill to obtain a milling composite tool blank with a CBN cubic boron nitride abrasive layer.

[0019] Step 5, Secondary Precision Grinding: Refer to Figure 3 (e) Reinstall the milling composite tool blank with CBN cubic boron nitride abrasive layer from step 4 onto the spindle of the machine tool from step 2, and trim the arc contour with a GC bar until the PCBN polycrystalline cubic boron nitride cutting edge from step 3 is exposed. Using this as a reference, grind the front groove according to the grinding method of step 3.

Claims

1. A circular arc milling composite tool suitable for fused silica machining, characterized in that... The cutting tool includes a T-shaped tool holder and a milling head, wherein: The milling cutter head consists of two parts: a circular layer and an abrasive layer. The head of the T-shaped tool holder is brazed to the inner surface of the annular layer; The outer surface of the annular layer is machined with several micro-blades with a certain angle; The micro-blade includes a front groove, a front face, a cutting edge, and a back face. An abrasive layer is deposited on the back face, and the back face with the abrasive layer deposited is on the same circumference as the cutting edge.

2. The circular arc milling composite tool for fused silica machining according to claim 1, characterized in that... The annular layer is made of PCBN (polycrystalline cubic boron nitride), and the abrasive layer is made of CBN (cubic boron nitride). The overall diameter is 30~100mm and the thickness is 5~20mm.

3. The circular arc milling composite tool for fused silica machining according to claim 1, characterized in that... The T-shaped tool holder is made of cemented carbide, with a shank diameter of 10-25mm, a head diameter that is the same as the inner diameter of the annular layer, and a length of 50-120mm.

4. The circular arc milling composite tool for fused silica machining according to claim 1, characterized in that... The radial thickness of the annular layer is 8~15mm, and the axial thickness is 5~20mm.

5. The circular arc milling composite tool for fused silica machining according to claim 1, characterized in that... The number of micro-blades is 10 to 30.

6. The circular arc milling composite tool for fused silica machining according to claim 1, characterized in that... The width of the cutting edge groove is 2~5mm, the depth is 2~5mm, the inclination angle of the cutting edge is 30°~60°, the rake angle is -6°~6°, the clearance angle before the abrasive layer is deposited is 5°~10°, and the clearance angle after deposition and shaping is 0°.

7. The circular arc milling composite tool for fused silica machining according to claim 1, characterized in that... The thickness of the abrasive layer is 3~10mm, the abrasive is CBN cubic boron nitride abrasive with fine particle size of 3000# or higher, and the binder is metallic nickel or copper with high bonding strength.

8. A method for preparing a circular arc milling composite tool suitable for fused silica machining as described in any one of claims 1-7, characterized in that... The method includes the following steps: Step 1: Welding the T-shaped tool holder head to the annular layer: The inner surface of the annular layer is welded to the T-shaped tool holder head using a brazing method to obtain a milling and grinding composite tool blank; Step 2, Laser shaping of the arc contour of the outer surface of the ring: The milling composite tool blank obtained in Step 1 is installed on the spindle of the XYZBC multi-axis linkage ultra-precision machine tool. The spindle drives the tool to rotate. A laser in-situ dressing system is set up. The laser beam is adjusted to be tangent to the circumferential direction of the tool, and the laser incident direction is parallel to the rotation direction of the tool. Excess material is removed layer by layer according to the predetermined trajectory to shape the arc contour feature. Step 3, Precision grinding of micro-edges: After step 2 is completed, without disassembling the tool, the dressing wheel is installed on the high-speed axis of the B turntable, and the front groove, front face, cutting edge and back face are dressed by XYZBC multi-axis linkage servo grinding to obtain a milling cutter with micro-edges. Step 4, Abrasive layer deposition: Abrasive is deposited on the surface of a milling cutter with micro-cutting edge by laser cladding or electroplating to obtain a milling-grinding composite tool blank with an abrasive layer; Step 5, Secondary Precision Grinding: Reinstall the milling composite tool blank with abrasive layer from Step 4 onto the spindle of the machine tool from Step 2, and use a GC bar to trim the arc contour until the cutting edge from Step 3 is exposed. Using the position of the cutting edge as a reference, grind the front groove according to the grinding method in Step 3.

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