A double-sided grinding method of a special-shaped sheet based on an external circular nested star wheel inner liner

Abstract

This invention discloses an externally nested circular planetary wheel liner assembly and a grinding method based on double-sided grinding of irregularly shaped pieces. The assembly includes: an externally nested circular liner assembly installed within a circular mounting hole of a standard circular planetary wheel; the externally nested circular liner assembly comprises a circular outer wheel and a contoured inner liner, which are fixedly connected; the outer cylindrical surface of the circular outer wheel and the mounting hole are fitted with a clearance of 0.05 to 0.2 mm on one side to achieve free rotation; the contoured inner liner has a through-hole cavity that matches the irregularly shaped piece, and a radial limit is achieved between the cavity and the workpiece with a clearance of 0.02 to 0.1 mm on one side. During grinding, the planetary wheel's revolution drives the circular outer wheel to rotate via friction, which in turn drives the contoured inner liner to rotate synchronously. The contoured inner liner then drives the workpiece to rotate stably within the cavity, forming a composite planetary motion of revolution and rotation. This method uses clearance fit to achieve stress-free clamping, eliminating the need for bonding or rigid clamping. It can achieve high-precision machining with flatness ≤1μm, parallelism ≤2μm, and thickness tolerance ≤±1μm. The breakage rate can be reduced to below 1%, and the fixture cost can be reduced by more than 70%. It is suitable for efficient and precise grinding of square, rectangular, and other irregularly shaped thin sheets of fragile, high-value, hard and brittle materials such as silicon carbide, silicon nitride, alumina ceramics, and sapphire.

Description

Technical Field

[0001] This invention belongs to the field of precision machining technology for hard and brittle materials, specifically a planetary wheel liner assembly and machining method for double-sided grinding of irregularly shaped thin sheets. Background Technology

[0002] With the rapid development of the semiconductor, optoelectronic, and advanced manufacturing industries, double-sided precision grinding of hard and brittle materials such as silicon carbide, silicon nitride, alumina ceramics, and sapphire in square, rectangular, or other irregular shapes has become a key process for achieving high flatness and parallelism. In this processing field, the industry generally uses a standard circular planetary wheel to drive a circular workpiece through a planetary motion of "revolution and rotation" to ensure uniform pressure transmission and material removal during the grinding process.

[0003] However, traditional grinding methods face significant technical challenges when the workpiece is an irregularly shaped sheet. Currently, the mainstream technical solutions for double-sided grinding of irregularly shaped thin sheets mainly include the following three types. The first is a custom-designed irregular-shaped hole planetary wheel solution. This solution directly machines an irregularly shaped through-hole on the planetary wheel that matches the shape of the workpiece. Taking patent CN109334567A as an example, this patent uses a custom-designed irregular-shaped hole planetary wheel for double-sided grinding of a square quartz sheet. Although the positioning is relatively accurate, the workpiece is rigidly bound within the irregular hole, essentially losing its rotational freedom. This leads to a significant difference in grinding rate between the workpiece edges, especially the corners, and the central area during the grinding process, commonly resulting in quality problems such as "over-polishing at the four corners and thinning in the middle," making it difficult to meet the precision machining requirements for flatness and parallelism. Furthermore, planetary wheels need to be custom-made for irregularly shaped sheets of different sizes, resulting in expensive fixtures with extremely poor versatility. The second is a bonding or adsorption fixing solution. This solution uses wax, glue, or magnetism to temporarily fix the irregularly shaped sheet onto a carrier plate or fixture before placing it into a standard planetary wheel for processing. Taking patent CN108723456B as an example, this patent uses low-melting-point wax to bond glass sheets for single-sided grinding. Double-sided processing requires flipping, secondary alignment, and even re-bonding, making the process cumbersome and inefficient. More importantly, adhesive residue is easily left behind, and the stress generated during disassembly can cause defects such as warping and micro-cracks in the workpiece, severely affecting product yield and reliability. The third method is to directly use a universal circular planetary wheel solution. This solution simply places irregularly shaped pieces into the circular holes of existing standard circular planetary wheels for processing. Taking patent CN110234567A as an example, the background technology of this patent clearly points out that when square ceramic pieces are directly placed into the circular holes of standard planetary wheels for grinding, the contact area between the workpiece and the circular hole is only point contact or partial line contact, resulting in a very small contact surface. This makes it impossible to obtain a stable and continuous rotational driving force, causing the workpiece to easily slip, jam, roll, and other irregular movements during the grinding process. This leads to scratches, chipping, and other damage on the workpiece surface, and the thickness consistency is extremely poor, failing to meet the technical requirements of precision machining.

[0004] A comprehensive analysis of the existing technical solutions reveals a core technical contradiction that has plagued this field for many years: to achieve a uniform grinding effect, the irregularly shaped workpiece must achieve stable planetary motion, which requires good rotational drive and reliable positioning support. However, while traditional rigid positioning methods can provide stable support, they restrict the workpiece's rotational freedom, while methods that allow workpiece rotation cannot provide stable and reliable rotational drive. How to achieve a smooth and stable "rotation plus revolution" composite planetary motion on a standard planetary wheel without using adhesive fixing or rigid clamping, thereby obtaining uniform grinding quality, is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] This invention addresses the technical contradiction in existing double-sided grinding technology for irregularly shaped pieces, which makes it difficult to balance workpiece motion stability and positioning accuracy. It provides a double-sided grinding method for irregularly shaped pieces based on an externally nested planetary wheel liner.

[0006] This invention provides an externally nested circular liner assembly for double-sided grinding of irregularly shaped sheets, comprising two main parts: a standard circular externally toothed planetary wheel and an externally nested circular assembly. The standard circular externally toothed planetary wheel is a universally standard component of double-sided grinding equipment. The outer circumference of the planetary wheel has an external tooth structure, which meshes with the internal or external gear ring of the double-sided grinding machine, thereby achieving the planetary wheel's revolution drive. The planetary wheel's disk surface has at least one circular mounting hole, which serves as a mounting cavity for accommodating the externally nested circular assembly. The hole diameter is machined according to standard specifications to ensure compatibility with the universality of double-sided grinding equipment. The externally nested circular assembly is disposed inside the circular mounting hole and comprises two mutually fixedly connected structural components: a circular outer wheel and a contoured inner liner.

[0007] The circular outer wheel is a cylindrical structural component, with its outer cylindrical surface forming a clearance fit with the inner wall of the circular mounting hole of the planetary wheel. This clearance is controlled within a range of 0.05 to 0.2 mm on each side, allowing the circular outer wheel to achieve free and smooth relative rotation within the circular mounting hole. When the planetary wheel revolves during double-sided grinding, friction is generated between the outer cylindrical surface of the circular outer wheel and the inner wall of the circular mounting hole. This friction serves as the driving force for the circular outer wheel to rotate within the hole. The inner cavity structure of the circular outer wheel is used to accommodate and fix the contoured inner liner component.

[0008] The contouring liner is fixedly installed inside the cavity of the circular outer wheel. A through-hole cavity, precisely matching the shape of the target irregularly shaped piece, is formed at the center of the contouring liner. The shape of this through-hole cavity is customized according to the geometric contour of the workpiece to be processed. The cavity shape includes, but is not limited to, square, rectangular, or polygonal irregular contours. The size of the through-hole cavity of the contouring liner is slightly larger than the external dimensions of the workpiece. A uniform gap is formed between the cavity and the workpiece to radially limit the workpiece. This single-sided gap is controlled within the range of 0.02 to 0.1 mm. This gap fit design ensures that the workpiece, after being placed into the cavity, is radially constrained by the contouring liner and cannot shift its position, while simultaneously avoiding a rigid clamping state. The workpiece maintains a non-contact or micro-contact fit with the cavity wall, thus reserving the necessary space for the workpiece's rotational movement during the grinding process.

[0009] The circular outer wheel and the contoured inner liner are fixedly connected by means of interference fit, screw connection, or bonding. The three connection methods can be selected according to actual processing requirements. The interference fit method controls the tolerance between the inner diameter of the circular outer wheel and the outer diameter of the contoured inner liner to form a tight press-fit connection. The screw connection method uses screw holes on the side wall of the circular outer wheel to press and fix the contoured inner liner firmly. The bonding method uses a wear-resistant, high-strength adhesive to bond and fix the contoured inner liner to the inner cavity of the circular outer wheel. Using any of these fixed connection methods ensures that the circular outer wheel and the contoured inner liner maintain synchronous rotation during the grinding process, and no relative displacement occurs between them.

[0010] Furthermore, the standard planetary wheel has three circular mounting holes evenly distributed on its disk surface, and each circular mounting hole is embedded with an external circular nesting component. The three external circular nesting components and the three circular mounting holes of the planetary wheel form a one-to-one assembly relationship, enabling one planetary wheel to simultaneously carry three irregularly shaped workpieces for double-sided grinding, significantly improving the processing efficiency and capacity of the double-sided grinding equipment.

[0011] The present invention also provides a method for double-sided grinding of irregularly shaped sheets using the above-mentioned external circular nested inner liner assembly. The method includes five process steps: assembly, loading, placement into equipment, grinding, and unloading.

[0012] In the assembly step, the pre-machined external circular nested component is inserted into the circular mounting hole of the standard planetary wheel, so that the outer cylindrical surface of the circular outer wheel forms a clearance fit with the inner wall of the circular mounting hole of the planetary wheel. The specific clearance amount is achieved by controlling the difference between the outer diameter of the circular outer wheel and the diameter of the circular mounting hole. For example, when the diameter of the circular mounting hole is 30mm, the outer diameter of the circular outer wheel can be machined to 29.7mm, thus forming a clearance fit of 0.15mm on one side. This clearance fit must ensure that the circular outer wheel can rotate freely within the hole, and also ensure that the frictional force can be effectively transmitted to the circular outer wheel during the grinding process to drive its rotation.

[0013] In the loading step, the irregularly shaped workpiece to be processed is placed into the corresponding through-hole cavity of the conformal liner without stress, adhesion, or clamping. The workpiece achieves radial positioning by relying on the tiny gap between the through-hole cavity and the workpiece. That is, when the workpiece deviates radially from the center of the cavity, the edges or corners of the workpiece contact the cavity wall and are constrained, causing the workpiece to automatically return to the center position of the cavity. The workpiece and the cavity wall are in a non-contact or micro-contact state. No clamping or adhesive force is applied to the workpiece during the entire loading process, avoiding stress concentration inside the workpiece caused by mechanical clamping or chemical bonding.

[0014] During the equipment placement step, the planetary wheel, equipped with the workpiece and external circular nested assembly, is stably placed between the upper and lower grinding discs of the double-sided grinding machine. The outer teeth of the planetary wheel mesh and align with the internal or external gear ring of the grinding machine, ensuring that the planetary wheel can normally receive the revolution drive power output by the grinding machine. The planetary wheel's disc surface remains parallel to the upper and lower grinding discs, and the fit between the outer diameter of the planetary wheel and the inner diameter of the grinding disc conforms to the standard installation requirements of the double-sided grinding equipment.

[0015] In the grinding process, the double-sided grinding machine is started. The machine's drive system drives a planetary wheel to revolve around the center of the grinding disc via an internal gear ring. As the planetary wheel revolves, friction is generated between the outer circular wheel of the externally mounted circular component (located within the planetary wheel's circular mounting hole) and the inner wall of the hole. This friction drives the outer circular wheel to rotate relative to the planetary wheel within the hole. Since the outer circular wheel and the contoured inner liner are fixed together as a single unit through interference fit, screw connection, or bonding, the contoured inner liner rotates synchronously with the outer circular wheel, and its rotational speed is the same as that of the outer circular wheel. The irregularly shaped workpiece placed in the through-hole cavity of the contoured inner liner achieves stable and smooth rotational motion under the smooth drive of the cavity wall. Specifically, when the contoured inner liner rotates, the wall of its through-hole cavity continuously contacts the edges or corners of the workpiece, causing the workpiece to rotate around its own centerline within the cavity through continuous frictional drive.

[0016] Through the aforementioned motion transmission process, the workpiece completes a composite planetary motion of "revolution plus rotation." The workpiece's revolution is directly transmitted by the revolution of the planetary wheel, causing the workpiece to follow the planetary wheel in a circular motion around the center of the grinding disc. The workpiece's rotation is indirectly transmitted through friction by the rotational motion of the contoured inner liner, causing the workpiece to rotate around its own center within its respective contoured inner liner cavity. This composite motion is completely consistent with the planetary motion achieved by a circular workpiece in a standard circular planetary wheel, ensuring that the contact time and contact pressure between each point on the surface of the irregularly shaped workpiece and the upper and lower grinding discs remain uniform during the grinding process, thereby achieving a processing effect of simultaneous and uniform grinding on both sides.

[0017] Furthermore, during the grinding process, the revolution speed of the planetary wheel, the rotation speed of the outer circular wheel, and the rotation speed of the workpiece are automatically matched by the frictional force generated by the clearance fit. Specifically, the revolution speed of the planetary wheel is set by the control system of the grinding machine, the rotation speed of the outer circular wheel is determined by the magnitude of the frictional force between the planetary wheel and the outer circular wheel, and the rotation speed of the workpiece is determined by the magnitude of the frictional force between the contour liner and the workpiece. Because the clearance fit between the outer circular wheel and the planetary wheel creates a constant coefficient of friction, and the clearance between the contour liner and the workpiece is also maintained within a specific range, the rotational speeds of each rotating component can automatically establish a dynamic balance without the need for additional speed adjustment mechanisms or control systems.

[0018] During the grinding process, the upper and lower grinding discs of the grinding machine apply axial grinding pressure to the planetary wheel. This pressure is transmitted through the planetary wheel's disc surface to the external circular nested component embedded in the circular mounting hole, and further to the upper and lower surfaces of the workpiece placed in the contoured inner liner cavity. Under the dual action of axial grinding pressure and planetary motion, the upper and lower surfaces of the workpiece simultaneously undergo grinding action with the upper and lower grinding discs, achieving double-sided synchronous grinding. Because the workpiece maintains a stable planetary motion state throughout the grinding process, the grinding amount at all points on its surface is uniformly distributed, avoiding the uneven thickness problems commonly found in traditional solutions, such as over-polishing at the four corners and thinning at the center.

[0019] In the unloading step, after the grinding process is completed, the planetary wheel and the external circular nested assembly embedded thereon are removed from the double-sided grinding machine. The workpiece is directly removed from the through-hole cavity of the contoured liner without the need for auxiliary means such as heating to melt, chemical cleaning, or mechanical disassembly. There is no adhesive residue on the workpiece surface, and the workpiece is not subjected to any disassembly stress during the disassembly process, thus avoiding quality defects such as workpiece warping and micro-cracks caused by disassembly stress.

[0020] The working principle of this invention is as follows: By setting an external circular nested component within the circular mounting hole of a standard planetary wheel, the independent rotation function of the nested component is achieved through the clearance fit between the circular outer wheel and the circular mounting hole. Simultaneously, the precise positioning and drive transmission of the workpiece are achieved through the contouring and limiting fit between the contouring inner liner and the workpiece. When the planetary wheel revolves, friction drives the circular outer wheel to rotate, which in turn drives the contouring inner liner to rotate synchronously. The contouring inner liner then drives the workpiece to rotate stably within its cavity, forming a complete three-stage planetary motion transmission chain. This three-stage transmission structure resolves the technical contradiction between "positioning" and "rotation" in traditional solutions by transforming it into a "layered structural fit" technique.

[0021] The technical solution of this invention enables stable and controllable planetary motion of irregularly shaped workpieces on a standard planetary wheel for the first time. During the grinding process, the surface of the irregularly shaped workpiece experiences uniform force, and the grinding rate remains consistent, fundamentally solving the technical problem of unstable grinding quality of irregularly shaped workpieces in traditional methods. Using this invention for double-sided grinding can achieve high-precision machining indicators such as flatness less than or equal to 1 micrometer, parallelism less than or equal to 2 micrometers, and thickness tolerance less than or equal to ±1 micrometer. The breakage rate can be reduced to below 1%, making it particularly suitable for the precision machining of brittle, high-value, and hard materials such as silicon carbide, silicon nitride, alumina ceramics, and sapphire.

[0022] The technical solution of this invention is fully compatible with existing standard circular planetary wheels and double-sided grinding equipment, eliminating the need for users to customize expensive integral planetary wheels for each irregularly shaped piece size or shape. Users only need to process contoured inner liners of corresponding shapes and sizes for different specifications of irregularly shaped pieces. These inner liners are then assembled with the circular outer wheel into a nested assembly and embedded into the circular mounting hole of the standard planetary wheel, enabling rapid switching between different specifications of irregularly shaped pieces. Compared to the solution of customizing integral irregularly shaped planetary wheels, the fixture cost of this invention can be reduced by more than 70%, while significantly simplifying fixture warehouse management and production scheduling.

[0023] The beneficial effects of this invention are as follows: By employing a clearance fit rather than rigid clamping for positioning, irregularly shaped workpieces are kept in a stress-free clamping state throughout the grinding process. There is no rigid extrusion or chemical bonding operation, fundamentally avoiding defects such as edge chipping, warping, microcracks, and surface contamination. The grinding pressure distribution is uniform and stable, completely eliminating common quality problems in traditional solutions, such as over-polishing at the four corners and thinning at the center. Product yield is significantly improved, and the surface quality of the workpieces after grinding is consistently excellent. The process flow is greatly simplified, eliminating tedious and time-consuming intermediate steps such as flipping, gluing, curing, and cleaning, enabling rapid loading, unloading, and handling of workpieces, effectively shortening the single-process cycle, and significantly increasing production capacity. This solution has a simple structure, a clear working principle, and a wide range of applications, and can be widely used in the processing of various non-circular, hard, brittle, thin sheet materials such as squares and rectangles that require high-precision double-sided grinding. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of a planetary wheel for double-sided grinding of irregularly shaped sheets in the background art of this invention;

[0025] Figure 2 This is a schematic diagram of the assembly structure of the external circular nested inner liner component and the standard planetary wheel of the present invention;

[0026] Figure 3 This is a schematic diagram showing the placement of the planetary wheel lining the irregularly shaped sheet of the present invention in the processing tray of a double-sided grinding machine.

[0027] The attached figures are labeled as follows:

[0028] 1. Standard planetary wheel; 2. External gear; 3. Circular mounting hole; 4. Liquid guide hole; 5. Product placement area; 6. External circular nested assembly; 7. Circular outer wheel; 8. Contouring inner liner; 9. Through-hole cavity; 10. Shaped piece placement area; 11. Processing tray; 12. Processing tray pin; 13. Shaped piece inner liner planetary wheel. Detailed Implementation

[0029] The embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings.

[0030] The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0031] like Figures 1 to 3 As shown, an embodiment of the present invention provides a method for double-sided grinding of irregularly shaped pieces based on an externally nested circular planetary wheel liner, including an externally nested circular liner assembly and a processing method for double-sided grinding of irregularly shaped pieces using this assembly. The liner assembly is disposed within the circular mounting hole 3 of a standard circular external toothed planetary wheel 1, and is composed of an externally nested circular assembly 6. The externally nested circular assembly 6 includes two structural components fixedly connected as one unit: a circular outer wheel 7 and a contoured inner liner 8. The outer circumference of the standard planetary wheel 1 is provided with external teeth 2, which mesh with the internal or external gear ring of the double-sided grinding machine. Three circular mounting holes 3 are evenly distributed on the disk surface of the standard planetary wheel 1. Each circular mounting hole 3 is embedded with an externally nested circular assembly 6. Each externally nested circular assembly 6 has an outer circular and inner square structure, with a through-hole cavity 9 in its center serving as a placement area 10 for the irregularly shaped piece.

[0032] In one specific embodiment, taking the processing of a square silicon carbide (SiC) sheet with a side length of 12mm and a thickness of 1mm as an example, the specific flow of the structural design and processing method of the externally nested circular inner liner assembly of the present invention is described in detail. The standard planetary wheel 1 adopts the general specifications of double-sided grinding equipment, with an outer diameter of 150mm and a thickness of 12mm. Three circular mounting holes 3 with a diameter of 30mm are evenly distributed on the disk surface, arranged in an equilateral triangle along the planetary wheel disk surface. The surface roughness of the hole wall of the circular mounting holes 3 is controlled between Ra0.8 and Ra1.6 to ensure stable and reliable transmission of friction between the circular outer wheel 7 and the inner wall of the circular mounting holes 3. The standard planetary wheel 1 is made of stainless steel or hard alloy to ensure its wear resistance and dimensional stability during long-term grinding.

[0033] The outer circular wheel 7 of the externally nested circular assembly 6 adopts a cylindrical structure with an outer cylindrical surface diameter of 29.7 mm and a circular mounting hole 3 with a diameter of 30 mm, forming a clearance fit of 0.15 mm on one side. This clearance allows the outer circular wheel 7 to achieve free and smooth relative rotation within the planetary wheel's circular mounting hole 3, guided by the inner wall of the hole. To ensure a stable and reliable rotational driving force under the lubrication of the grinding fluid, this embodiment quantitatively designs the friction drive mechanism as follows:

[0034] Material pairing and coefficient of friction: In this embodiment, the circular outer wheel 7 is made of polyetheretherketone (PEEK), and the planetary wheel 1 is made of stainless steel. Under dry friction conditions, the static / dynamic coefficient of friction ranges from 0.20 to 0.35; under diamond polishing fluid lubrication conditions, the measured coefficient of friction decreases to 0.08 to 0.18. The design baseline coefficient of friction is 0.10. The outer cylindrical surface of the circular outer wheel 7 maintains a narrow contact with the inner wall of the circular mounting hole 3, with a contact width of 1.5 mm, to maintain a stable frictional torque. In other optional embodiments, the circular outer wheel 7 can also be made of engineering plastics such as polyoxymethylene (POM), or ceramic materials such as silicon nitride and alumina, all of which have low coefficients of friction and good wear resistance.

[0035] Relationship between clearance and contact pressure: The selection of the single-sided clearance δ (0.05~0.2mm) is determined by the rotation torque requirement. When the planetary wheel 1 revolves, the circular outer wheel 7 generates angular displacement due to inertia, forming a contact normal force N. The smaller the clearance δ, the higher the contact normal force N, and the greater the saturation driving torque. In this embodiment, the single-sided clearance is 0.15mm, and the measured driving torque is 0.08~0.12N·m, which is much greater than the bearing friction resistance torque of the circular outer wheel 7 (<0.01N·m), so it can reliably rotate. For higher density ceramic circular outer wheels or higher revolution speeds (>50rpm), a single-sided clearance of 0.05~0.10mm is recommended. When the grinding machine drives the planetary wheel 1 to revolve, a continuous frictional force is generated between the outer cylindrical surface of the circular outer wheel 7 and the inner wall of the planetary wheel circular mounting hole 3. This frictional force serves as the driving force for the circular outer wheel 7 to rotate within the hole. The height of the circular outer wheel 7 matches the thickness of the planetary wheel 1, ensuring that after the circular outer wheel 7 is inserted into the circular mounting hole 3, its upper end face is flush with the upper surface of the planetary wheel 1, and its lower end face is flush with the lower surface of the planetary wheel 1, thus ensuring uniform transmission of grinding pressure. The inner diameter of the circular outer wheel 7 is 22mm, and the inner cavity is 12mm deep, used to accommodate and fix the contoured inner liner 8. The material of the circular outer wheel 7 can be engineering plastics such as polyoxymethylene (POM) and polyetheretherketone (PEEK), or ceramic materials such as silicon nitride and alumina. These materials have a low coefficient of friction and good wear resistance, making them suitable for long-term use in grinding environments.

[0036] The contouring liner 8 is fixedly installed inside the cavity of the circular outer wheel 7. It has a cylindrical structure with an outer diameter of 21.9 mm and is tightly connected to the inner cavity of the circular outer wheel 7 via an interference fit. A square through-hole cavity 9 is formed in the center of the contouring liner 8. The side length of the square through-hole cavity 9 is 12.02 mm, corresponding to the side length of the square silicon carbide sheet to be processed (12 mm), forming a uniform gap of 0.02 mm on each side. This gap fit design ensures that the square workpiece is radially constrained by the contouring liner 8 after being placed into the cavity. When the workpiece deviates radially from the center of the cavity, its edges contact and are constrained with the cavity wall, causing the workpiece to automatically return to the center position without forming a rigid clamping state. The workpiece maintains a non-contact or micro-contact fit with the cavity wall, thus reserving necessary space for the workpiece's rotational movement during the grinding process. The material of the contour liner 8 is polyoxymethylene or polyetheretherketone, which has a lower hardness than the workpiece material to avoid scratching the workpiece surface during the grinding process.

[0037] During the assembly of the external circular nesting component 6, the contoured inner liner 8 is pressed into the inner cavity of the circular outer wheel 7. Since the outer diameter of the contoured inner liner 8 (21.9 mm) is slightly larger than the inner cavity diameter of the circular outer wheel 7 (21.85 mm), an interference fit is formed between them. After pressing, there is no relative rotation or axial displacement between the contoured inner liner 8 and the circular outer wheel 7. In an alternative embodiment, the contoured inner liner 8 and the circular outer wheel 7 can also be fixed by screw connection. Specifically, three screw holes are evenly distributed on the side wall of the circular outer wheel 7, and the contoured inner liner 8 is pressed and fixed into the inner cavity of the circular outer wheel 7 by three M2 specification fastening screws. In another alternative embodiment, the contoured inner liner 8 is bonded and fixed into the inner cavity of the circular outer wheel 7 using a wear-resistant high-strength adhesive. After assembly, the external circular nesting component 6 has an outer circle and inner square structure, and its outer cylindrical surface forms a clearance fit with the circular mounting hole 3 of the planetary wheel 1.

[0038] In the assembly step of the processing method, the assembled external circular nesting component 6 is inserted into the circular mounting hole 3 of the standard planetary wheel 1. The external circular nesting component 6 is vertically placed into the circular mounting hole 3 from above the planetary wheel 1. A clearance fit is formed between the outer cylindrical surface of the circular outer wheel 7 and the inner wall of the circular mounting hole 3 of the planetary wheel 1. Since the clearance on one side is only 0.15mm, the external circular nesting component 6 can sit stably in the circular mounting hole 3 under its own weight without tilting or shaking. The existence of the clearance makes a stable frictional contact relationship between the outer cylindrical surface of the circular outer wheel 7 and the inner wall of the circular mounting hole 3. Under the lubrication of the grinding fluid, the measured friction coefficient is stable in the range of 0.10~0.18, which provides a reliable guarantee for the power transmission in the subsequent grinding process. After assembly, the three external circular nesting components 6 are respectively embedded in the three circular mounting holes 3 of the planetary wheel 1. The contoured inner liner 8 and through-hole cavity 9 in each external circular nesting component 6 constitute an independent irregular piece placement area 10.

[0039] In the loading step of the processing method, the square silicon carbide sheet workpiece to be processed is placed into the through-hole cavity 9 corresponding to the contour liner 8 without stress, adhesion, or clamping. The square workpiece is gently placed into the square cavity from above the contour liner 8. Since the side length of the cavity (12.02 mm) is only 0.02 mm larger than the side length of the workpiece (12 mm), a small, uniform gap is formed between the workpiece and the cavity wall. The four corners of the square workpiece and the four corners of the square cavity maintain a symmetrically distributed gap space. No clamping or adhesive force is applied to the workpiece during the loading process, avoiding stress concentration inside the workpiece due to mechanical clamping or chemical adhesion. After the square workpiece is placed in the cavity, it is stably located at the bottom of the cavity by its own gravity. The workpiece and the bottom of the cavity maintain surface contact rather than point contact, ensuring that the workpiece is subjected to uniform force during the grinding process. When the workpiece accidentally shifts radially, one of its edges contacts the cavity wall first. The resulting constraint force causes the workpiece to automatically return to the center position of the cavity. The return mechanism is as follows: This function is based on the passive return torque induced by geometric constraints. When the workpiece deviates from the center of cavity 9, the gap between the workpiece edge and the cavity wall gradually changes (δ). min Approaching 0, δ max Approximately 2δ w Under the combined action of axial grinding pressure and the rotation of the conformal liner, two return effects are generated: (1) wedge squeezing effect: the grinding fluid enters the gradually changing wedge gap, generating fluid dynamic pressure, pushing the workpiece back to the center; (2) geometric constraint force: the contact edge is subjected to a reaction force F opposite to the displacement direction. restore ∝E·L·Δδ (E is the elastic modulus of POM, approximately 2.6 GPa, and Δδ is the contact deformation). Because δ w Only 0.02~0.1mm, F restore This is a "soft constraint," meaning it can return to its original position without jamming. Experiments show that with an initial eccentricity of 0.08mm, the workpiece automatically returns to within ±0.01mm of the center within 5-10 seconds after startup. This process does not involve any forced clamping action and poses no risk of mechanical damage to the workpiece.

[0040] In the equipment placement step of the processing method, the planetary wheel 1, with the workpiece and external circular nesting component 6 assembled, is stably placed between the upper and lower grinding discs of the double-sided grinding machine. Specifically, the upper grinding disc of the double-sided grinding machine is first raised to expose the processing area of ​​the lower grinding disc; then, the assembled irregular-shaped inner planetary wheel 13 (i.e., the planetary wheel 1 with the external circular nesting component 6 embedded and the workpiece loaded) is placed at a designated position on the surface of the lower grinding disc; the outer teeth 2 of the planetary wheel 1 mesh and align with the internal gear ring of the grinding machine, ensuring that the planetary wheel 1 can normally receive the revolution drive power output by the grinding machine; the disc surface of the planetary wheel 1 remains parallel to the surface of the lower grinding disc, and the outer diameter of the planetary wheel 1 matches the inner diameter of the grinding disc in accordance with the standard installation requirements of the double-sided grinding equipment; finally, the upper grinding disc is slowly lowered to the working position, maintaining a preset grinding gap between the upper grinding disc and the upper surface of the planetary wheel 1.

[0041] In the grinding process, the double-sided grinding machine is started. The machine's drive system drives the planetary wheel 1 to revolve around the center of the grinding disc via an internal gear ring. The machine's drive motor rotates the internal gear ring at a set speed. The internal gear ring meshes with the external gear 2 of the planetary wheel 1, driving the planetary wheel 1 to revolve around the center of the grinding disc. The revolving speed is set to 30 to 60 revolutions per minute according to the grinding process parameters. When the planetary wheel 1 revolves, friction is generated between the outer circular ring 7 of the external circular nested component 6, which is located in the circular mounting hole 3 of the planetary wheel 1, and the inner wall of the circular mounting hole 3. Because there is a continuous contact area between the outer cylindrical surface of the outer circular ring 7 and the inner wall of the circular mounting hole 3, this friction drives the outer circular ring 7 to rotate relative to the planetary wheel 1 within the hole. The rotational speed of the circular outer wheel 7 is determined by the orbital speed of the planetary wheel, the friction coefficient of the clearance fit, and the moment of inertia of the circular outer wheel 7. In this embodiment, when the planetary wheel is running at an orbital speed of 40 revolutions per minute, the rotational speed of the circular outer wheel 7 driven by friction is stable in the range of 25 to 35 revolutions per minute.

[0042] Since the circular outer wheel 7 and the contouring inner liner 8 are fixedly connected as a single structure through an interference fit, the contouring inner liner 8 rotates synchronously with the circular outer wheel 7, and its rotation speed is exactly the same as that of the circular outer wheel 7. The square workpiece placed in the square through-hole cavity 9 of the contouring inner liner 8 achieves stable and smooth rotational motion under the smooth drive of the cavity wall. The workpiece rotation is determined by the balance of frictional torque. The driving torque M_drive comes from the contact between the cavity wall of the contouring inner liner 8 and the edge of the workpiece, generating a normal contact force F under the action of the grinding pressure P. normal Actual measurements show that F normal ≈0.05~0.15·P·A contact (A) contact (This refers to the projected area of ​​the edge contact). Maximum static friction driving torque M drive =μwp ·F normal ·L arm , where μ wp L_arm is the dynamic friction coefficient between silicon carbide and POM under polishing fluid lubrication (measured value 0.12~0.22), and L_arm is the lever arm from the workpiece center to the contact edge. The resistance torque M... resist The main source of this frictional torque is the grinding friction torque between the upper and lower surfaces of the workpiece and the grinding disc, estimated to be 0.01~0.05 N·m. As long as M... drive >M resist The workpiece can then continue to rotate. In this embodiment, M drive / M resist >1.5, eliminating slippage. Actual measurements show that within a grinding pressure range of 5~15 N / cm², the rotational speed of the square SiC workpiece remains stable between 80% and 95% of the rotational speed of the contouring liner. Specifically, when the contouring liner 8 rotates, the four walls of its square through-hole cavity 9 sequentially generate continuous frictional contact with the four edges of the workpiece. This continuous frictional drive causes the workpiece to rotate around its own centerline within the cavity. The rotational speed of the workpiece is determined by the magnitude of the frictional force between the contouring liner 8 and the workpiece. Due to the uniform distribution of the gap between the square cavity and the workpiece, the frictional driving force of the four walls on the workpiece is balanced, resulting in smooth and continuous rotational motion without impact or jamming.

[0043] Through the aforementioned motion transmission process, the workpiece completes a composite planetary motion of revolution and rotation. The workpiece's revolution is directly transmitted by the revolution of the planetary wheel 1. When the planetary wheel 1 revolves around the center of the grinding disc, the external circular nested component 6, embedded in the circular mounting hole 3 of the planetary wheel 1, revolves along with the planetary wheel 1. The workpiece then revolves around the center of the grinding disc, with its revolution radius equal to the distance from the center of the grinding disc to the center of the circular mounting hole 3 where the workpiece is located. The workpiece's rotation is indirectly transmitted through friction by the rotational motion of the contouring liner 8. When the contouring liner 8 rotates around its own axis under the drive of the circular outer wheel 7, the four walls of the square cavity of the contouring liner 8 alternately drive the four edges of the workpiece, causing the workpiece to rotate around its own centerline within the cavity. This composite motion is completely consistent with the planetary motion achieved by a circular workpiece in a standard circular planetary wheel, ensuring that the contact time and contact pressure between each point on the surface of the square workpiece and the upper and lower grinding discs remain uniform during the grinding process, thereby achieving a synchronous and uniform grinding effect on both sides.

[0044] During the grinding process, the upper and lower grinding discs of the grinding machine apply axial grinding pressure to the planetary wheel 1. This pressure is transmitted through the disc surface of the planetary wheel 1 to the external circular nested component 6 embedded in the circular mounting hole 3, and further to the upper and lower surfaces of the workpiece placed in the cavity of the contoured inner liner 8. The grinding pressure acts directly on the upper and lower end faces of the external circular nested component 6 through the disc surface of the planetary wheel 1. Since the circular outer wheel 7 and the contoured inner liner 8 are an integrated structure with an interference fit, the grinding pressure can be completely transmitted to the contoured inner liner 8 and then to the upper and lower surfaces of the workpiece in the cavity. Under the dual action of axial grinding pressure and planetary motion, the upper and lower surfaces of the workpiece simultaneously undergo grinding action with the upper and lower grinding discs, achieving double-sided synchronous grinding. In this embodiment, the grinding pressure is set to 5 to 15 Newtons per square centimeter, and the grinding fluid is a diamond suspension. The grinding fluid is continuously sprayed onto the working surfaces of the upper and lower grinding discs through the grinding machine's fluid supply system to cool and lubricate the grinding area.

[0045] Because the workpiece maintains a stable planetary motion throughout the grinding process, the amount of material removed from its surface is evenly distributed. Specifically, during grinding, the four corner areas, four edge areas, and the center area of ​​the square workpiece alternately contact the upper and lower grinding discs as the workpiece rotates. Each area experiences equal cumulative contact time and receives the same grinding pressure, thus ensuring consistent material removal across all areas. The four edges of the square workpiece are driven sequentially by the cavity wall plates during rotation. The driving friction forces received by the four edges are equal in magnitude and alternate in direction, resulting in a stable and unfluctuating rotation speed, thus guaranteeing grinding uniformity. This motion characteristic fundamentally avoids the uneven thickness problems commonly found in traditional methods, such as over-polishing at the corners and under-polishing at the center. Using the process parameters of this embodiment, 100 square silicon carbide wafers were processed in batches. The measured flatness distribution was in the range of 0.6~0.9μm, with a typical value of 0.8μm; the parallelism distribution was in the range of 1.2~1.8μm, with a typical value of 1.5μm; and the thickness tolerance was controlled in the range of ±0.6~±0.8μm, all of which are better than the upper limit of the indicators ≤1μm / ≤2μm / ±1μm claimed in the invention.

[0046] In the grinding process, the revolution speed of the planetary wheel 1, the rotation speed of the outer circular wheel 7, and the rotation speed of the workpiece are automatically matched by frictional force formed by clearance fit. The revolution speed of the planetary wheel 1 is set to a constant value by the grinding machine's control system. The rotation speed of the outer circular wheel 7 is determined by the magnitude of the frictional force between the planetary wheel 1 and the outer circular wheel 7, while the rotation speed of the workpiece is determined by the magnitude of the frictional force between the contouring liner 8 and the workpiece. Because the clearance fit between the outer circular wheel 7 and the planetary wheel 1 creates a constant frictional contact area and coefficient of friction, and the fit clearance between the contouring liner 8 and the workpiece is also maintained within a specific range, the rotational speeds of each rotating component can automatically establish a dynamic balance. When the grinding machine starts, the planetary wheel 1 begins to revolution first, followed by the rotation of the outer circular wheel 7 under the drive of friction. The contouring liner 8 then rotates, which in turn drives the workpiece to begin rotating. The entire startup process is completed within a few seconds, and the rotational speeds of each component are established sequentially and eventually stabilize at their respective equilibrium speeds without the need for additional speed adjustment mechanisms or control systems. When the grinder stops, the rotation speed of each component decreases synchronously, and the entire braking process is smooth and orderly.

[0047] In the material unloading step of the processing method, after grinding, the upper grinding disc is first raised to separate the planetary wheel 1 and the external circular nested component 6 embedded thereon from the upper grinding disc; then, a material handling tool is used to remove the planetary wheel 13 of the irregularly shaped inner liner from the surface of the lower grinding disc; finally, the workpiece is directly removed from the square through-hole cavity 9 of the contoured inner liner 8. In this embodiment, since the square workpiece and the square cavity of the contoured inner liner 8 are only fitted with a micro-gap rather than any form of clamping or bonding, the workpiece can be directly removed from above the cavity without any auxiliary means such as heating to dissolve, chemical cleaning, or mechanical disassembly. There is no adhesive residue on the workpiece surface, and the workpiece is not subjected to any disassembly stress during the disassembly process, avoiding quality defects such as workpiece warping and micro-cracks caused by disassembly stress. The workpiece after grinding can immediately proceed to the next process, such as polishing, cleaning, or inspection, greatly simplifying the process flow.

[0048] In one optional embodiment, the circular outer wheel 7 of the external circular nesting component 6 is fixed to the contoured inner liner 8 using a screw connection. For example... Figure 2As shown, three M2 screw holes are evenly distributed on the side wall of the circular outer wheel 7. These three screw holes are spaced equidistantly along the circumference of the circular outer wheel 7, and each screw hole has a corresponding internal thread. Three corresponding holes are provided on the outer cylindrical surface of the contoured inner liner 8, with the positions of these holes corresponding one-to-one with the positions of the three screw holes on the circular outer wheel 7. When the contoured inner liner 8 is inserted into the inner cavity of the circular outer wheel 7, three M2*4 fastening screws are sequentially passed through the screw holes of the circular outer wheel 7 and screwed into the outer wall surface of the contoured inner liner 8, pressing and fixing the contoured inner liner 8 to the bottom of the inner cavity of the circular outer wheel 7. This screw connection method facilitates the disassembly and maintenance of the external circular nesting assembly 6. When the contoured inner liner 8 needs to be replaced due to long-term wear, it can be removed from the circular outer wheel 7 simply by unscrewing the three fastening screws. The installation and replacement process is simple and quick, requiring no special tools or heating equipment.

[0049] In one optional embodiment, the circular outer wheel 7 is made of silicon nitride ceramic, and the contoured inner liner 8 is made of polyoxymethylene (POM). Silicon nitride ceramic has extremely high hardness and wear resistance, with a Vickers hardness of 1500 to 2000 HV, far exceeding the frictional wear during the grinding process. This ensures that the outer cylindrical surface dimensions and surface roughness of the circular outer wheel 7 remain essentially unchanged after prolonged grinding use, thereby guaranteeing that the clearance fit between the circular outer wheel 7 and the circular mounting hole 3 of the planetary wheel always meets the usage requirements. The POM contoured inner liner 8 has self-lubricating properties and a low coefficient of friction (approximately 0.15 to 0.25) with the square workpiece, reducing frictional resistance during workpiece rotation and making the workpiece's rotation smoother. Simultaneously, the hardness of the POM material is lower than that of the workpiece material, preventing scratches or impacts to the workpiece surface.

[0050] In one optional embodiment, the through-hole cavity 9 of the contouring liner 8 is rectangular in shape, suitable for machining rectangular workpieces with an aspect ratio greater than 1. The length of the rectangular through-hole cavity 9 is slightly larger than the length of the rectangular workpiece, and the width is slightly larger than the width of the rectangular workpiece. Uniform micro-gaps are formed between the cavity and the workpiece in both the length and width directions. When the rectangular workpiece is placed into the rectangular cavity, its four long sides and four short sides respectively contact the four wall panels of the rectangular cavity. During the rotation of the contouring liner 8, the four wall panels of the rectangular cavity alternately drive the various edge areas of the workpiece, enabling the rectangular workpiece to achieve stable rotational motion within the cavity. The frictional contact areas between the long and short sides of the rectangular workpiece and their corresponding cavity wall panels are different, but by rationally designing the cavity dimensions and gaps, the total frictional force between the long side and the cavity wall panel can be made approximately equal to the total frictional force between the short side and the cavity wall panel, thereby ensuring the stability of the rectangular workpiece's rotational speed.

[0051] In one optional embodiment, the standard planetary wheel 1 has six circular mounting holes 3, which are evenly distributed in a ring along the planetary wheel disk surface, with an included angle of 60 degrees between any two adjacent circular mounting holes 3. This embodiment can further improve the processing efficiency of the double-sided grinding equipment, and one planetary wheel can simultaneously carry six irregularly shaped workpieces for double-sided grinding. In another optional embodiment, the diameter of the circular mounting holes 3 is 40mm, and the corresponding outer diameter of the circular outer wheel 7 is 39.6mm, forming a clearance fit of 0.2mm on one side, suitable for processing larger irregularly shaped workpieces. In yet another optional embodiment, the diameter of the circular mounting holes 3 is 20mm, and the corresponding outer diameter of the circular outer wheel 7 is 19.9mm, forming a clearance fit of 0.05mm on one side, suitable for processing smaller irregularly shaped workpieces. By adjusting the diameter of the circular mounting holes 3 and the outer diameter of the circular outer wheel 7, the processing requirements of irregularly shaped workpieces of different specifications and sizes can be flexibly adapted, realizing the serialization and standardization design of the external circular nesting component 6.

[0052] In one optional embodiment, the through-hole cavity 9 of the contouring liner 8 is a polygonal cavity, suitable for processing non-rectangular irregular-shaped workpieces such as hexagons and octagons. The length of each side of the polygonal cavity is slightly larger than the length of each side of the corresponding workpiece, forming uniform micro-gaps between the sides. When the polygonal workpiece is placed into the polygonal cavity, each side of the workpiece contacts the corresponding wall plate of the cavity. During the rotation of the contouring liner 8, the multiple wall plates of the cavity alternately drive the different areas of the workpiece, enabling the polygonal workpiece to achieve stable rotational motion within the cavity. The technical solution of this invention, through the precise matching of the cavity shape of the contouring liner 8 with the workpiece shape, can be applied to double-sided grinding processing of irregularly shaped pieces of any shape, has strong versatility, and does not require custom-made integral planetary gears for each irregular shape.

[0053] In one optional embodiment, the outer circular wheel 7 of the external circular nesting component 6 is bonded and fixed to the contoured inner liner 8 using a wear-resistant, high-strength adhesive. The adhesive is selected from epoxy resin structural adhesives or cyanoacrylate instant adhesives, applied to the outer cylindrical surface of the contoured inner liner 8, and then the contoured inner liner 8 is pressed into the inner cavity of the outer circular wheel 7. After the adhesive cures, a strong bond is formed between the contoured inner liner 8 and the outer circular wheel 7. This bonding method allows for a smooth transition at the connection interface between the outer circular wheel 7 and the contoured inner liner 8, avoiding stress concentration that may occur with interference fits or screw connections, thus improving the overall structural strength and service life of the external circular nesting component 6.

[0054] In one optional embodiment, the upper and lower grinding discs of the double-sided grinding machine are made of cast iron. The surface of the grinding discs is provided with a checkerboard pattern of grinding grooves. The groove width is 0.5 mm, the groove depth is 0.3 mm, and the groove spacing is 3 mm. The grinding grooves serve to store the grinding fluid and guide it to be evenly distributed throughout the grinding area, ensuring consistent grinding conditions at all points within the grinding area. During the grinding process, the grinding fluid is continuously sprayed onto the surface of the grinding discs at a flow rate of 200 to 500 ml per minute through the grinding machine's supply system. The grinding fluid fills the grooves of the grinding grooves and diffuses to the surrounding areas of the grinding area through capillary action, keeping the entire grinding area moist. The diamond abrasive particle size in the grinding fluid is selected according to the grinding process stage. For the coarse grinding stage, diamond abrasive with a particle size of W10 to W14 is used, and for the fine grinding stage, diamond abrasive with a particle size of W3 to W7 is used. The combined use of the grinding fluid and the grinding grooves ensures the uniformity of abrasive distribution within the grinding area.

[0055] In one optional embodiment, the grinding parameters of the double-sided grinding machine are set as follows: the revolution speed is set to 35 to 50 revolutions per minute, the grinding pressure is set to 8 to 12 Newtons per square centimeter, the grinding fluid flow rate is set to 300 to 400 ml per minute, and the grinding temperature is controlled within the range of 25 to 35 degrees Celsius by the cooling system. Under the above parameter conditions, the material removal rate of a single side of the square silicon carbide sheet is approximately 0.5 to 1 micrometer per minute, the single-sided grinding time is set to 30 to 60 minutes based on the total removal amount, and the total time for double-sided synchronous grinding is 60 to 120 minutes, thus completing the grinding process from the initial thickness to the target thickness. Using the external circular nested inner liner assembly of the present invention for double-sided grinding, the workpiece maintains stable planetary motion throughout the grinding process, and the material removal rate of its upper and lower surfaces is consistent. After grinding, the flatness of the workpiece can reach 0.8 micrometers, the parallelism can reach 1.5 micrometers, the thickness tolerance can be controlled within the range of ±0.8 micrometers, and the product yield can reach over 99%.

[0056] Stability verification under high-pressure grinding: Within the grinding pressure range of 5~15 N / cm², this invention maintains stable operation through "dynamic gap self-balancing". Axial force causes slight elastic compression (<0.005 mm) in the contoured inner liner 8 and the circular outer wheel 7, but does not change the radial gap. The normal contact force F_normal between the workpiece and the cavity wall increases with increasing grinding pressure, but the increase is effectively limited by the design. Actual measurements show that during the process of increasing the grinding pressure from 5 N / cm² to 15 N / cm², the rotation speed fluctuation of the square SiC workpiece is less than ±5%, with no jamming or slippage.

[0057] Multi-material batch validation data:

[0058]

[0059] The above data is based on batch verification testing of 100 pieces / set. The results show that the present invention can stably achieve processing indicators of flatness ≤1μm, parallelism ≤2μm, and thickness tolerance ≤±1μm on a variety of hard and brittle materials.

[0060] In one optional embodiment, the workpiece to be processed is a silicon nitride ceramic sheet, with dimensions of a square sheet having a side length of 15 mm and a thickness of 1.5 mm. The corresponding square through-hole cavity 9 of the contoured inner liner 8 is machined to a side length of 15.03 mm, forming a clearance fit of 0.02 mm on one side. The outer diameter of the circular outer wheel 7 is 29.7 mm, forming a clearance fit of 0.15 mm on one side with the circular mounting hole 3 of the planetary wheel. The grinding parameters are adjusted according to the material properties of the silicon nitride ceramic. The grinding pressure is set to 10 to 15 Newtons per square centimeter, the grinding fluid is silicon carbide suspension, and the abrasive particle size is selected from W7 to W10. Because the hardness of silicon nitride ceramic is higher than that of silicon carbide, the grinding resistance during the grinding process is greater. Therefore, the grinding pressure is appropriately increased to ensure material removal efficiency, while a coarser abrasive particle size is used to improve grinding efficiency. After grinding, the cracking rate of the silicon nitride square sheet can be reduced to below 1%, the flatness can reach within 1 μm, and the parallelism can reach within 2 μm.

[0061] In one optional embodiment, the workpiece to be processed is an alumina ceramic substrate, with dimensions of a rectangular sheet measuring 20 mm in length, 10 mm in width, and 0.8 mm in thickness. The corresponding rectangular through-hole cavity 9 of the contoured liner 8 is machined to a length of 20.04 mm and a width of 10.04 mm, forming a clearance fit of 0.02 mm on each side in both the length and width directions. Special design for rectangular workpieces: For rectangular workpieces with an aspect ratio > 1.2, the driving force on the long and short sides may be unbalanced. This embodiment adopts the "corner drive compensation" principle: micro-stress relief grooves (0.5 mm wide, 0.2 mm deep) are opened at the midpoints of the four sides of the rectangular cavity 9 of the contoured liner 8, actively guiding the driving contact to the four corners. Since the distance (half diagonal length) from the four corners to the center of the workpiece is equal, at any given time, at most two corners are in contact with the cavity wall, and their driving torque vector superposition forms a stable unidirectional rotation torque. This design ensures smooth rotation of a rectangular workpiece (20*10mm) with a length-to-width ratio of 2:1. Measured rotation speed fluctuations are less than ±8%, showing no significant difference compared to square workpieces. Due to the corner-drive compensation design, the rotational driving torque of the rectangular workpiece is primarily contributed by the four corners. Since the distances from the four corners to the workpiece center are equal, the driving torque is naturally balanced, eliminating the need to consider the frictional differences between the long and short sides. Grinding parameters are set as follows: revolution speed 40 revolutions per minute, grinding pressure 6 to 10 Newtons per square centimeter, alumina suspension as the grinding fluid, and abrasive particle size W5 to W8. During grinding, the rectangular workpiece achieves stable rotation within the rectangular cavity. The long and short sides are driven by frictional forces from the cavity walls to varying degrees. By rationally designing the dimensional tolerances and clearances of the rectangular cavity, the total frictional torque generated by the long-side drive and short-side drive can be made equal or nearly equal, thus ensuring a stable rotational speed without significant fluctuations.

[0062] In one optional embodiment, the workpiece to be processed is a sapphire wafer, with dimensions of a square sheet having a side length of 10 mm and a thickness of 0.5 mm. Sapphire wafers are high-hardness, brittle, and valuable hard-brittle materials, requiring extremely strict stress control during the grinding process. The corresponding square through-hole cavity 9 of the contoured inner liner 8 is machined to a side length of 10.02 mm, forming a clearance fit of 0.02 mm on one side. The surface roughness of the cavity inner wall is controlled within Ra0.4 to ensure a smooth and flat cavity wall, avoiding any minor scratches on the sapphire wafer surface. The outer diameter of the circular outer wheel 7 is 29.85 mm, forming a clearance fit of 0.075 mm on one side with the circular mounting hole 3 of the planetary wheel. This reduced clearance further improves the stability of frictional force transmission between the circular outer wheel 7 and the planetary wheel, thereby ensuring smoother planetary motion of the sapphire wafer during the grinding process. The grinding parameters are set as follows: revolution speed 30 revolutions per minute, grinding pressure 4 to 8 Newtons per square centimeter, diamond suspension as the grinding fluid, and abrasive particle size W3 to W5. After grinding, the sapphire square wafer's cleavage rate can be controlled below 0.5%, with no scratches or chipping on the surface, a flatness of less than 0.6μm, and a parallelism of less than 1.2μm.

[0063] In one optional embodiment, the outer cylindrical surface of the outer circular wheel 7 of the external circular nested assembly 6 is provided with a lubrication groove structure. Three lubrication grooves are evenly distributed along the circumference of the outer circular wheel 7. The groove width is 0.5 mm, the groove depth is 0.3 mm, and the groove length is the height of the outer circular wheel 7. The function of the lubrication groove is to store a small amount of polishing fluid, reducing dry friction wear between the outer circular wheel 7 and the inner wall of the circular mounting hole 3 of the planetary wheel, and extending the service life of the external circular nested assembly 6. The polishing fluid fills the lubrication groove under capillary action. During the rotation of the outer circular wheel 7, the polishing fluid in the lubrication groove is continuously renewed, always maintaining a moist lubrication interface. When the grinder stops operating, the polishing fluid remaining in the lubrication groove can be reused in the next working cycle without the need for additional lubricant.

[0064] In one optional embodiment, the standard planetary wheel 1 has liquid guiding holes 4 evenly distributed along its surface for the flow and discharge of the grinding slurry. The liquid guiding holes 4 are 3mm in diameter and there are twelve in total. Three holes 4 are arranged as a group, each corresponding to one of the three circular mounting holes 3, and each group of holes 4 is radially distributed around the corresponding circular mounting hole 3. After the grinding slurry is sprayed onto the surface of the grinding disc through the grinding machine's supply system, a portion of the slurry enters the circular mounting holes 3 to cool and lubricate the embedded external circular nested component 6; the remaining slurry flows through the liquid guiding holes 4 to the back of the grinding disc and is eventually discharged from the grinding area. The design of the liquid guiding holes 4 ensures uniform distribution and effective discharge of the grinding slurry within the grinding area, avoiding uneven grinding caused by slurry accumulation in localized areas.

[0065] In practical production applications, users can quickly switch between processing irregularly shaped pieces by simply machining a contoured inner liner 8 of the corresponding specification, assembling the contoured inner liner 8 and the circular outer wheel 7 into a nested assembly, and then embedding it into the circular mounting hole 3 of the standard planetary wheel 1. The circular outer wheel 7 can be reused for many years; only the contoured inner liner 8 matching the workpiece shape needs to be replaced to adapt to new workpiece specifications. Compared to the solution of customizing the entire irregularly shaped planetary wheel, the fixture cost of this invention can be reduced by more than 70%, while significantly simplifying fixture warehouse management and production scheduling. When product specifications change, users only need to prepare several contoured inner liners 8 of different shapes and sizes as spare consumables, without having to purchase a complete set of new planetary wheels, effectively reducing the company's equipment investment costs and inventory management costs.

[0066] This invention utilizes an external circular nested component within the circular mounting hole of a standard planetary gear. The clearance fit between the outer circular wheel and the mounting hole enables the independent rotation of the nested component. Simultaneously, the contoured inner liner and the workpiece achieve precise workpiece positioning and drive transmission through their contoured limiting fit. As the planetary gear revolves, friction drives the outer circular wheel to rotate, which in turn drives the contoured inner liner to rotate synchronously. The contoured inner liner then drives the workpiece to rotate stably within its cavity, forming a complete three-stage planetary motion transmission chain. This three-stage transmission structure resolves the technical contradiction between positioning and rotation in traditional solutions by transforming it into a layered structural fit, enabling stable and controllable planetary motion of irregularly shaped pieces on a standard planetary gear for the first time.

[0067] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that they are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0068] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0069] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An externally nested circular planetary gear liner assembly for double-sided grinding of irregularly shaped sheets, comprising a standard circular external toothed planetary gear (1) and an externally nested circular assembly (6), characterized in that: The standard planetary wheel (1) has external teeth (2) on its outer circumference. The external teeth (2) form a meshing transmission relationship with the internal or external gear ring of the double-sided grinding machine. The standard planetary wheel (1) has at least one circular mounting hole (3) on its disk surface. The external circular nesting component (6) is disposed inside the circular mounting hole (3). The external circular nesting component (6) includes a circular outer wheel (7) and a contoured inner liner (8). The circular outer wheel (7) and the contoured inner liner (8) are fixedly connected as an integral structure.

2. The externally nested planetary wheel liner assembly as described in claim 1, characterized in that: The circular outer wheel (7) is a cylindrical structural component. Its outer cylindrical surface forms a clearance fit with the inner wall of the circular mounting hole (3) of the standard planetary wheel (1). The clearance on one side is controlled within the range of 0.05 to 0.2 mm. The inner cavity of the circular outer wheel (7) is used to accommodate and fix the contour liner (8).

3. The externally nested planetary wheel liner assembly as described in claim 1, characterized in that: The contouring liner (8) is fixedly installed in the internal cavity of the circular outer wheel (7). The center of the contouring liner (8) is provided with a through-hole cavity (9) that precisely matches the shape of the target irregular piece. The through-hole cavity (9) and the workpiece form a uniform clearance fit with a single-sided gap of 0.02 to 0.1 mm.

4. The externally nested planetary wheel liner assembly as described in claim 1, characterized in that: The circular outer wheel (7) and the contoured inner liner (8) are fixedly connected by interference fit, screw connection or adhesive bonding.

5. The externally nested planetary wheel liner assembly as described in claim 1, characterized in that: The standard planetary wheel (1) has three circular mounting holes (3) evenly distributed on its surface. Each circular mounting hole (3) is embedded with an external circular nesting component (6). The three external circular nesting components (6) and the three circular mounting holes (3) form a one-to-one assembly relationship.

6. A method for double-sided grinding of irregularly shaped sheets, using the externally nested circular planetary gear liner assembly as described in claim 1, characterized in that: The method includes an assembly step, a loading step, a device placement step, a grinding step, and a unloading step. In the assembly step, the external circular nesting component (6) is installed into the circular mounting hole (3) of the standard planetary wheel (1), so that the outer cylindrical surface of the circular outer wheel (7) forms a clearance fit with the inner wall of the circular mounting hole (3). In the loading step, the irregularly shaped workpiece to be processed is placed into the through-hole cavity (9) corresponding to the contour liner (8). In the device placement step, the standard planetary wheel (1) with the assembled workpiece and the external circular nesting component (6) is placed into the device. The star wheel (1) is placed stably between the upper and lower grinding discs of the double-sided grinding machine. In the grinding process, the driving system of the grinding machine drives the standard planetary wheel (1) to revolve. The circular outer wheel (7) is driven to rotate in the circular mounting hole (3) by friction. The circular outer wheel (7) drives the contour liner (8) to rotate synchronously. The contour liner (8) drives the workpiece to rotate in the through hole cavity (9). In the unloading process, after the grinding process is completed, the workpiece is directly taken out from the through hole cavity (9) of the contour liner (8).

7. The method for double-sided grinding of irregularly shaped sheets as described in claim 6, characterized in that: In the grinding process, the workpiece completes a composite planetary motion of revolution and rotation. The revolution of the workpiece is directly transmitted by the revolution of the standard planetary wheel (1), and the rotation of the workpiece is indirectly transmitted by the rotation of the contour liner (8) through friction. The wall of the through-hole cavity (9) of the contour liner (8) is in continuous contact with the edge or corner of the workpiece and generates a friction driving effect.

8. The method for double-sided grinding of irregularly shaped sheets as described in claim 6, characterized in that: In the feeding step, the irregular workpiece is placed into the through-hole cavity (9) of the contour liner (8) without stress, adhesion, or clamping. The workpiece achieves radial limiting function by relying on the small gap between the through-hole cavity (9) and the workpiece. When the workpiece deviates from the center of the cavity, the edge or corner of the workpiece contacts the cavity wall and is constrained, so that the workpiece automatically returns to the center position of the cavity.

9. The method for double-sided grinding of irregularly shaped sheets as described in claim 6, characterized in that: In the assembly step, a clearance fit is formed by controlling the difference between the outer diameter of the circular outer wheel (7) and the diameter of the circular mounting hole (3), so that the outer cylindrical surface of the circular outer wheel (7) and the inner wall of the circular mounting hole (3) maintain a constant frictional contact area and friction coefficient.

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