A compact silicon nitride ceramic cone head low-damage processing technology

Abstract

The application provides a compact silicon nitride ceramic cone head low-damage machining tool and process, aiming at the characteristics of hard and brittle compact silicon nitride material, large and uneven blank allowance of solid block roughcast, optimizes blank cutting method and allowance distribution, and designs and manufactures a low-stress clamping tool, the tool can realize large-area fitting and supporting of a contoured surface, and uses a low-stress clamping mode of vacuum adsorption to replace a pressing plate, solves the technical problems of edge collapse and cracks caused by excessive local stress. At the same time, according to the product structure characteristics, a regional variable parameter machining track is formulated, which can reduce the cutting force fluctuation and improve the cutting stability, and provides reliability support for high-quality machining of compact silicon nitride ceramic material.

Description

Technical Field

[0001] This invention belongs to the field of ceramic material machining, and specifically relates to a low-damage machining process for dense silicon nitride ceramic cones. Background Technology

[0002] Ceramic materials possess excellent mechanical and wave-transmitting properties, but they are also difficult to machine due to their high brittleness, high hardness, and high wear resistance, making them typical hard-to-machine materials. With the increasing demands for these materials, the structures of ceramic parts are trending towards complex, non-referenced curved surface structures, which presents several challenges in machining these parts:

[0003] (1) Ceramic materials are both hard and brittle, and are prone to cracking and breakage during processing, making it more difficult to achieve high-precision, low-damage processing.

[0004] (2) For non-axisymmetric structural parts, the shape and allowance of the product blank are extremely irregular, and the workpiece clamping force is uneven and there is local stress concentration due to the thermal stress deformation during the sintering process of ceramic materials, which easily causes crack propagation.

[0005] (3) The workpiece adopts a contour-following blank-without-reference-base processing scheme. The workpiece and tooling cannot be accurately positioned. It is necessary to repeatedly measure and test cut multiple times to determine the workpiece outline and allowance. The processing efficiency is low, the dimensional accuracy is poor, and the processing yield is not high.

[0006] To address the aforementioned issues, this invention proposes a low-damage machining process for dense silicon nitride ceramic cones. This process achieves low-damage machining of dense silicon nitride ceramic cones through specialized tooling design and manufacturing, clamping method optimization, and toolpath optimization. Summary of the Invention

[0007] In order to overcome the shortcomings of the existing technology, the inventors have conducted intensive research and provided a low-damage processing technology for dense silicon nitride ceramic cones, which solves problems such as edge chipping, cracking and surface roughness during workpiece processing.

[0008] The technical solution provided by this invention is as follows:

[0009] A low-damage processing technology for dense silicon nitride ceramic cones includes:

[0010] The original blank material is cut into rectangular blank blocks that meet the allowance requirements;

[0011] The four corners of the rectangular blank are cut off to form an octagonal cross-section blank, creating four new inclined surfaces.

[0012] The octagonal cross-section blank block is fixed in the octagonal groove at the bottom of the auxiliary clamping block. The auxiliary clamping block has a relative clamping plane. The clamping plane and the bottom surface meet the flatness requirements. After installation, the upper surface of the octagonal cross-section blank block meets the flatness requirements.

[0013] Install a water tank base on the plane of a high-speed machining center, straighten and align it in the X and Y directions, and install a vise and a surface adsorption fixture on the water tank base.

[0014] The auxiliary clamping block and the octagonal cross-section blank block are installed together in the jaws of the vise, and the jaw clamping plate clamps the clamping plane of the auxiliary clamping block.

[0015] The outer contour of the octagonal cross-section blank block is rough machined using diamond abrasive tools. The areas near the four inclined surfaces of the octagonal cross-section blank block are rough machined separately to make the blank contour after rough machining similar to the product contour.

[0016] Use diamond abrasive tools to semi-finish the outer contour of a curved surface in the circumferential direction;

[0017] Use diamond abrasive tools to finish the outer contour of the curved surface in the circumferential direction; at least two cutting directions are used in the semi-finishing and finishing processes. In the roughing, semi-finishing and finishing processes, the outer contour is machined along the edge contour and curvature of the large end to determine the length.

[0018] After removing the auxiliary clamping block and the blank after the finishing surface, the finished cone is placed into the surface adsorption fixture. The finished surface fits into the contour surface of the surface adsorption fixture. The cone is adsorbed onto the contour surface of the adsorption fixture by vacuuming.

[0019] The water tank base, along with the surface adsorption fixture and the cone head, is transferred to a surface grinder. The clamping plane and bottom surface of the auxiliary clamping block are used for alignment. The auxiliary clamping block and the octagonal cross-section blank block are machined using a diamond grinding wheel. The large end is ground to remove the excess material, resulting in a silicon nitride ceramic cone head. During the roughing, semi-finishing, finishing, and grinding processes to remove the large end excess material, the processing area is cooled by spraying deionized water.

[0020] The low-damage processing technology for dense silicon nitride ceramic cones provided by the present invention has the following beneficial effects:

[0021] This invention addresses the challenges of dense silicon nitride ceramic materials, such as hardness and brittleness, and large and uneven allowances in solid blanks. It optimizes the blank cutting method and allowance distribution, and designs and manufactures low-stress clamping fixtures to solve technical problems like chipping and cracking caused by excessive local stress. Based on the product's structural characteristics, a regional variable-parameter machining trajectory is developed, which reduces cutting force fluctuations, improves cutting stability, and achieves high-quality product machining, with post-machining surface chipping dimensions ≤0.05mm. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the cutting of the original blank material;

[0023] Figure 2 This is a schematic diagram of the machining tooling structure.

[0024] Explanation of icon numbers

[0025] 1-Octagonal cross-section blank block; 2-Surplus material around the perimeter; 3-Auxiliary clamping block; 4-Water tank base; 5-Visor; 6-Surface adsorption fixture; 7-Water tank baffle plate; 8-Air nozzle; 9-Spiral groove; 10-Support bushing. Detailed Implementation

[0026] The features and advantages of the present invention will become clearer and more explicit from the following detailed description.

[0027] The term “exemplary” as used herein means “serving as an example, embodiment, or illustration.” Any embodiment illustrated herein as “exemplary” is not necessarily to be construed as superior to or better than other embodiments.

[0028] This invention provides a low-damage processing technology for dense silicon nitride ceramic cones, comprising the following steps:

[0029] Step (1): Use a height gauge and scriber to mark lines on the original blank block, ensuring that the allowance is uniform in all directions. Cut the original blank block into rectangular blank blocks that meet the processing requirements according to the marked lines;

[0030] Step (2): Considering the cone structure, the rectangular blank has a large machining allowance at the four corners. When the tool is machining the product in the circumferential direction, there is cutting at the corners and no cutting between the corners. The tool transitions from the no-cutting area to the corner area. Once it contacts the corner, it will vibrate, which is not conducive to the stable processing of the product.

[0031] To reduce the machining allowance at the four corners of the rectangular blank and to reduce vibration caused by uneven cutting allowance, the rectangular blank is cut into an octagonal blank 1, producing four new 45° bevels; the remaining material 2 around the four sides can be used for processing performance test samples.

[0032] Step (3): Use fiberglass or other materials to process auxiliary clamping block 3. The outer contour of auxiliary clamping block 3 is 20-30mm larger than the cross-section of the octagonal blank block. It has a relative clamping plane. The clamping plane and the bottom surface meet the flatness requirements (flatness ≤ 0.02mm). If the outer contour of auxiliary clamping block 3 is a rectangular clamping block, the clamping plane and the bottom surface meet the flatness requirements. According to the actual measured dimensions of the cross-section of the octagonal blank block, process an octagonal groove on the upper surface of auxiliary clamping block 3 to meet the fitting clearance of 0.1-0.2mm. The depth of the groove is less than the height allowance of the octagonal blank block. Drill holes at the rounded corners of the groove to avoid interference with the sharp corners of the octagonal blank block.

[0033] Step (4): Apply adhesive such as 914 glue to the inner wall of the groove of the auxiliary clamping block 3 and one end of the octagonal cross-section blank block 1. Insert the glued end of the octagonal cross-section blank block 1 into the groove of the auxiliary clamping block 3. Use a dial indicator or height gauge to check that the flatness of the upper surface of the octagonal cross-section blank block 1 is ≤0.02mm (as a reference surface). If there is any deviation, it can be leveled by tapping. After meeting the requirements, let it cure at room temperature for 3-5 hours. If you need to improve the curing efficiency, you can use a hot air gun to heat the gap. After heating, it should be cooled naturally to avoid sudden heating and cooling that may cause cracks in the product.

[0034] Step (5): Install the water tank base 4 on the plane of the high-speed machining center, straighten and align it in the X and Y directions, and install the vise 5 and the surface adsorption fixture 6 on the water tank base 4.

[0035] The sink base 4 can be made of materials such as 5A06, and the flatness of the bottom surface should be ≤0.02mm.

[0036] The clamping plate at the jaws of the vise that contacts the product is made of a flexible contact material such as nylon, while the rest is made of metal materials such as 2Cr13 stainless steel.

[0037] The surface adsorption fixture 6 includes a support base and a support bushing 10. A conical groove is formed on the support base, and the outer surface of the groove matches the surface of the support bushing 10 to accommodate it. An air passage communicating with the outside is provided at the bottom of the conical groove, and an air nozzle 8 connected to a vacuum pump is installed at the outlet of the air passage. The inner surface of the support bushing 10 matches the product surface, and a spiral groove 9 is formed on the inner surface, with its small end opening to connect to the air passage. The vacuum pump draws the conical head tightly against the support bushing 10. The support bushing 10 is made of nylon material and flexibly conforms to the conical head.

[0038] Step (six): Install the cured auxiliary clamping block 3 together with the octagonal cross-section blank block 1 into the jaws of the vise 5, and clamp the clamping plates of the jaws to clamp the auxiliary clamping block 3 on both symmetrical sides.

[0039] Step (7): Install the water tank baffle 7 in the groove around the water tank base 4. Use deionized water for cooling during the processing. The water tank baffle 7 can be a 5A06 welded part. The weld height is not lower than the height of the vise 5 and the surface adsorption fixture 6. After assembly with the water tank base 4, it can ensure sealing and prevent water leakage.

[0040] Step (8): Find each plane of the octagonal cross-section blank block 1, and the flatness should be ≤0.02mm;

[0041] Step (9): Use diamond abrasive tools to rough machine the outer contour. For rough machining of sharp corners, use a reciprocating machining path with layered machining in different areas and a high speed and small depth of cut. Specifically, the tool speed is 6000-8000 r / min and the depth of cut is 0.02-0.04 mm.

[0042] Specifically, the areas near the four 45° angled surfaces on the octagonal cross-section blank block 1 are rough-machined respectively, so that the blank outline after rough machining is similar to the product outline, and the blank allowance is preferably 1 to 2 mm.

[0043] Step (10): Use diamond abrasive tools to semi-finish the outer contour of the curved surface in the circumferential direction. Use a cycloidal machining toolpath and a machining method with high speed, low feed, and large depth of cut. Specifically: speed 6000-8000 r / min, feed 800-1500 mm / min, depth of cut 0.04-0.08 mm; the blank allowance after semi-finishing is 0.1-0.5 mm.

[0044] Step (XI): Use diamond abrasive tools to perform circumferential finishing of the curved surface contour. Employ a cycloidal toolpath and a high-speed, high-feed, and low-depth-of-cut machining method. Specifically: speed 6000-8000 r / min, feed 2000-4000 mm / min, depth of cut 0.02-0.04 mm. Use at least two cutting directions during semi-finishing and finishing processes to avoid the accumulation of residual height by changing the cutting direction.

[0045] In step (12), during roughing, semi-finishing, and finishing, to ensure machining allowance, the outer contour surface is extended by 5-10mm along the edge contour and curvature of the large end.

[0046] Step (13): Disassemble the auxiliary clamping block 3 and the blank after the finishing surface, and put the finished cone into the surface adsorption fixture 6. The finished surface fits into the contour surface of the surface adsorption fixture 6.

[0047] Step (XIV): Install the air pipe of the vacuum pump on the air nozzle 8 of the surface adsorption fixture 6, start the vacuum pump, and suck out the air in the spiral groove 9 on the surface adsorption fixture 6 so that the cone head is adsorbed on the contour surface of the adsorption fixture 6.

[0048] Step (15): Transfer the water tank base 4 together with the surface adsorption fixture 6 and the cone head to the surface grinder. Use the plane of the auxiliary clamping block 3 for alignment, and use a diamond grinding wheel to process the auxiliary clamping block 3 and the octagonal cross-section blank block 1. Grind away the excess at the large end to avoid chipping the edge of the cone head.

[0049] The diamond abrasive tool in steps (nine to eleven) has a mesh size of ≥80, and the diamond grinding wheel in step (xv) has a mesh size of ≥600.

[0050] Example

[0051] Example 1

[0052] In this embodiment, the dense silicon nitride ceramic cone is a rectangular blank envelope block with a blank size of approximately 50×50×60mm. The forming surface is rough and the allowance is uneven. The specific processing procedure is as follows:

[0053] Step (1): Based on the maximum envelope size of the product, add machining allowance, and use a height gauge and scriber to scribble lines on the original blank block. The scribing dimensions are 44×44×58mm. See [link / details]. Figure 1 Cut the original blank into rectangular blank blocks that meet the processing requirements according to the marked dividing lines;

[0054] Step (2): Cut the rectangular blank into an octagonal blank 1 with a side length of about 18mm, creating four new 45° bevels; the remaining material 2 around the perimeter can be used for processing performance test samples.

[0055] Step (3): Use fiberglass material to process rectangular auxiliary clamping block 3. The flatness of the clamping plane and the bottom surface should meet the requirement of ≤0.02mm. The outer contour size of auxiliary clamping block 3 is 70×70mm. According to the actual measured size of the octagonal cross section, process an octagonal groove on the upper surface of the auxiliary clamping block with a gap of 0.1mm and a groove depth of 6mm. Drill holes at the sharp corners of the groove to avoid gaps.

[0056] Step (4): Apply 914 glue to the inner wall of the groove of the auxiliary clamping block 3 and one end of the octagonal cross-section blank block 1. Insert the glued end of the octagonal cross-section blank block 1 into the groove of the auxiliary clamping block 3. Use a dial indicator to check that the flatness of the upper surface of the octagonal cross-section blank block 1 is ≤0.02mm. If there is a deviation, it can be leveled by tapping. After meeting the requirements, let it cure at room temperature for 5 hours. If a hot air gun is used to heat the gap, the curing time can be shortened to 3 hours.

[0057] Step (5): Install the water tank base 4 on the plane of the high-speed machining center, straighten and align it in the X and Y directions, and install the custom vise 5 and the surface adsorption fixture 6 on the water tank base 4; the flatness of the bottom surface of the water tank base 4 is ≤0.02mm.

[0058] Step (six): Install the cured auxiliary clamping block 3 together with the octagonal cross-section blank block 1 into the jaws of the vise 5, and clamp the auxiliary clamping block 3 on both symmetrical sides.

[0059] Step (7): Install the water tank baffle 7 in the groove around the base 4 of the water tank, and use deionized water for cooling during the processing.

[0060] Step (8): Find each plane of the octagonal cross-section blank block 1, and the flatness should be ≤0.02mm;

[0061] Step (9): Use a diamond abrasive tool (100 grit) to rough machine the outer contour. Reciprocate the machining in the area near the four 45° angled surfaces on the octagonal cross-section blank block 1. The rotation speed is 6000 r / min and the depth of cut is 0.04 mm.

[0062] Step (10): Use a diamond abrasive tool (100 mesh) to semi-finish the outer contour of the curved surface in the circumferential direction. Use a cycloidal machining toolpath, spindle speed 6000 r / min, feed rate 1000 mm / min, and depth of cut 0.08 mm.

[0063] Step (XI): Use diamond abrasive tools (100 mesh) to finish the outer contour of the curved surface. Use cycloidal machining toolpath, spindle speed 6000 r / min, feed 3000 mm / min, depth of cut 0.04 mm. Use at least two cutting directions during semi-finishing and finishing to avoid the accumulation of residual height by changing the cutting direction.

[0064] During roughing, semi-finishing, and finishing processes, in order to ensure machining allowance, the outer contour surface is extended by 5mm along the edge contour and curvature of the surface at the large end.

[0065] Step (13): Disassemble the auxiliary clamping block 3 and the blank after the finishing surface, and put the finished cone into the surface adsorption fixture 6. The finished surface fits into the contour surface of the surface adsorption fixture 6.

[0066] Step (XIV): Install the air pipe of the vacuum pump on the air nozzle 8 of the surface adsorption fixture 6, start the vacuum pump, and suck out the air in the spiral groove 9 on the surface adsorption fixture 6 so that the cone head is adsorbed on the contour surface of the adsorption fixture 6.

[0067] Step (15): Transfer the water tank base 4 together with the surface adsorption fixture 6 and the cone head to the surface grinder. Use diamond abrasive (800 mesh wheel) to process the auxiliary clamping block 3 and the octagonal cross-section blank block 1. Grind to remove the excess at the large end, with a cutting depth of 0.005mm, to avoid chipping the edge of the cone head.

[0068] Product performance: The surface accuracy after processing meets the requirements, there are no cracks, and the surface chipping size is ≤0.05mm.

[0069] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

[0070] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A low-damage processing technology for dense silicon nitride ceramic cones, characterized in that, include: The original blank material is cut into rectangular blank blocks that meet the allowance requirements; The four corners of the rectangular blank are cut off to form an octagonal cross-section blank, creating four new inclined surfaces. The octagonal cross-section blank block is fixed in the octagonal groove at the bottom of the auxiliary clamping block. The auxiliary clamping block has a relative clamping plane. The clamping plane and the bottom surface meet the flatness requirements. After installation, the upper surface of the octagonal cross-section blank block meets the flatness requirements. In the step of fixing the octagonal cross-section blank block into the octagonal groove at the bottom of the auxiliary clamping block, the outer contour of the auxiliary clamping block is 20-30mm larger than the cross-section of the octagonal cross-section blank block, and the clamping plane and bottom surface meet the flatness requirement of ≤0.02mm; the octagonal groove of the auxiliary clamping block meets the requirement of a fitting clearance of 0.1-0.2mm with the octagonal cross-section blank block, the groove depth dimension is smaller than the height allowance dimension of the octagonal cross-section blank block, and holes are drilled at the rounded corners of the groove to avoid interference with the sharp corners of the octagonal cross-section blank block; Apply adhesive to the inner wall of the octagonal groove of the auxiliary clamping block and one end of the octagonal cross-section blank block. Insert the adhesive-coated end of the octagonal cross-section blank block into the octagonal groove of the auxiliary clamping block. Check that the flatness of the upper surface of the octagonal cross-section blank block is ≤0.02mm. After the requirement is met, cure. Install a water tank base on the plane of a high-speed machining center, straighten and align it in the X and Y directions, and install a vise and a surface adsorption fixture on the water tank base. The auxiliary clamping block and the octagonal cross-section blank block are installed together in the jaws of the vise, and the jaw clamping plate clamps the clamping plane of the auxiliary clamping block. The outer contour of the octagonal cross-section blank block is rough machined using diamond abrasive tools. The areas near the four inclined surfaces of the octagonal cross-section blank block are rough machined separately to make the blank contour after rough machining similar to the product contour. Use diamond abrasive tools to semi-finish the outer contour of a curved surface in the circumferential direction; Use diamond abrasive tools to finish the outer contour of the curved surface in the circumferential direction; at least two cutting directions are used in the semi-finishing and finishing processes. In the roughing, semi-finishing and finishing processes, the outer contour is machined along the edge contour and curvature of the large end to determine the length. After removing the auxiliary clamping block and the blank after the finishing surface, the finished cone is placed into the surface adsorption fixture. The finished surface fits into the contour surface of the surface adsorption fixture. The cone is adsorbed onto the contour surface of the adsorption fixture by vacuuming. The water tank base, along with the surface adsorption fixture and the cone head, is transferred to a surface grinder. The clamping plane and bottom surface of the auxiliary clamping block are used for alignment. The auxiliary clamping block and the octagonal cross-section blank block are machined using a diamond grinding wheel. The large end is ground to remove the excess material, resulting in a silicon nitride ceramic cone head. During the roughing, semi-finishing, finishing, and grinding processes to remove the large end excess material, the processing area is cooled by spraying deionized water.

2. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, In the steps of installing the water tank base on the plane of the high-speed machining center, straightening and aligning it in the X and Y directions, and installing the vise and the surface adsorption fixture on the water tank base, the flatness of the bottom surface of the water tank base should be ≤0.02mm.

3. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, In the steps of installing a water tank base on the plane of a high-speed machining center, straightening and aligning it in the X and Y directions, and installing a vise and a surface adsorption fixture on the water tank base, the clamping plate at the vise jaws that contacts the product is made of a flexible contact material.

4. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, In the steps of installing a water tank base on the plane of a high-speed machining center, straightening and aligning it in the X and Y directions, and installing a vise and a surface adsorption fixture on the water tank base, the surface adsorption fixture includes a support base and a support bushing. A conical groove is formed on the support base, and the outer surface of the conical groove matches the surface of the support bushing to accommodate the support bushing. An air passage is provided at the bottom of the conical groove to communicate with the outside, and an air nozzle connected to a vacuum pump is installed at the outlet of the air passage. The inner surface of the support bushing matches the surface of the product, and a spiral groove is formed on the inner surface, with the small end opening to communicate with the air passage. The conical head is pressed tightly against the support bushing by vacuum pump suction.

5. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, After the step of installing the auxiliary clamping block and the octagonal cross-section blank block together in the jaws of the vise, and clamping the clamping plate of the jaws to clamp the clamping plane of the auxiliary clamping block, the method further includes: aligning each plane of the octagonal cross-section blank block, requiring a flatness of ≤0.02mm.

6. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, Before the step of rough machining the outer contour of the octagonal cross-section blank block with diamond abrasive tools, a water tank baffle is installed in the circumferential groove of the water tank base. The height of the water tank baffle is not lower than the height of the vise and the surface adsorption fixture. After being assembled with the water tank base, it ensures a tight seal and prevents water leakage.

7. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, In the step of roughing the outer contour of the octagonal cross-section blank block using diamond abrasive tools, the tool rotation speed is 6000-8000 r / min and the cutting depth is 0.02-0.04 mm.

8. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, In the step of semi-finishing the outer contour of the curved surface using diamond abrasive tools, a cycloidal machining toolpath is adopted, with a rotational speed of 6000-8000 r / min, a feed rate of 800-1500 mm / min, and a depth of cut of 0.04-0.08 mm.

9. The low-damage processing technology for dense silicon nitride ceramic cones according to claim 1, characterized in that, In the step of circumferentially finishing the outer contour of the curved surface using diamond abrasive tools, a cycloidal machining toolpath is adopted, with a rotational speed of 6000-8000 r / min, a feed rate of 2000-4000 mm / min, and a depth of cut of 0.02-0.04 mm.

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