Processing method of a rotary cutter and rotary cutter

Abstract

This invention discloses a machining method for a circular cutting tool and the tool itself. Based on the traditional processes of rough machining of the tool blank's inner hole, fine grinding of the inner hole, end face machining, and external grinding of the cutting edge, this method adds an inner hole datum rework process after fine grinding and before cutting edge grinding. This process uses a diamond grinding wheel with a grit size of not less than 800 mesh to perform micro-grinding on the finely ground inner hole on a high-precision internal grinding machine, obtaining a precision datum inner hole with a roundness error of no more than 0.003 mm. This datum inner hole is then used as the sole datum for external grinding of the cutting edge. This invention fundamentally solves the problem of insufficient datum precision by actively correcting the inner hole roundness damage caused by the preceding grinding process, ultimately significantly improving the roundness of the cutting edge's outer circle and its concentricity with the inner hole. It is particularly suitable for the ultra-precision machining of circular cutting tools made of high-hardness materials such as cemented carbide.

Description

Technical Field

[0001] This application relates to the field of circular cutting tool processing technology, and in particular to a method for processing a circular cutting tool and a circular cutting tool. Background Technology

[0002] Circular cutters are key precision tools widely used in industries such as papermaking, metal processing, and film slitting. Their core performance indicators, such as cutting edge sharpness, dimensional stability, and service life, largely depend on the geometric accuracy of the tool, especially the roundness of the outer circle of the cutting edge and the concentricity between the cutting edge and the mounting reference inner hole.

[0003] Currently, the typical machining process for circular cutting tools mainly includes: first, roughing and finishing the inner hole of the tool blank (usually including rough grinding and fine lapping) to obtain an inner hole as a reference; then, grinding the two end faces to ensure parallelism; finally, using the machined inner hole as a reference, grinding the outer circle and angle of the cutting edge on a precision grinding machine. Among these, the finishing of the inner hole often adopts the honing (or "grinding") process. This process uses free abrasive grains to perform micro-cutting on the inner hole surface, which can effectively improve the surface finish and dimensional consistency of the inner hole, and is considered to be the final step in the finishing of the inner hole.

[0004] However, the aforementioned traditional process suffers from a long-overlooked but seriously problematic technical issue that significantly impacts final machining accuracy: during the grinding process, due to factors such as uneven abrasive distribution, fluctuations in grinding pressure, and heat generated during processing, the roundness of the inner hole after grinding undergoes uncontrollable degradation. This minute, random roundness deviation is directly replicated and amplified onto the outer diameter of the cutting edge during subsequent grinding, which serves as a reference. Consequently, the roundness of the outer diameter and its theoretical concentricity with the inner hole fail to meet the ultra-precision levels required for high-end applications. Although the inner hole dimensions and surface finish meet the requirements, this hidden deficiency in reference accuracy becomes the main bottleneck restricting further improvements in the overall accuracy of the circular cutting tool. Summary of the Invention

[0005] The purpose of this invention is to provide a machining method for a circular cutting tool. By adding a high-precision inner hole datum rework process after the fine grinding process, the roundness deviation of the inner hole caused by grinding is eliminated, thereby providing an ultra-precision datum for the cutting edge grinding, and ultimately ensuring the high roundness and concentricity of the outer circle of the cutting edge.

[0006] To achieve the above objectives, this application provides the following technical solution:

[0007] A method for machining a circular cutting tool includes sequentially performing rough machining of the tool blank's inner hole, fine grinding of the inner hole, end face machining, and external cylindrical grinding of the cutting edge. After completing the fine grinding of the inner hole and before starting the external cylindrical grinding of the cutting edge, an additional inner hole datum reworking process is added. The inner hole datum reworking process involves clamping the tool blank, which has already undergone fine grinding in the previous process, onto a high-precision internal cylindrical grinding machine, and using an ultra-fine diamond grinding wheel with a grit size of not less than 800 mesh to perform micro-grinding on the finely ground inner hole; thereby obtaining a precision datum inner hole with a roundness error of not more than 0.003 mm. This precision datum inner hole is directly used as the positioning datum for the subsequent external cylindrical grinding of the cutting edge.

[0008] Furthermore, in the internal bore reference repair process, the diamond grinding wheel has a grit size of 1500 mesh and a hardness of soft.

[0009] Furthermore, the grinding parameters for the internal hole datum repair process are: workpiece spindle speed 3-8 rpm, grinding wheel axial feed speed 0.2-0.5 m / min, and radial feed amount 0.001-0.003 mm per pass.

[0010] Furthermore, the internal bore reference repair process, after completing the radial feed, also includes a no-feed polishing stage, with a polishing time of 30 to 90 seconds.

[0011] Furthermore, when performing the inner hole reference repair process, a high-precision fixture is used for clamping, which is positioned by the outer circle or end face of the tool blank.

[0012] Furthermore, when performing the external cylindrical grinding process of the cutting edge, a tapered shank or mandrel that maintains a clearance fit or transition fit with the precision reference inner hole is used for clamping.

[0013] Furthermore, the material of the circular cutter blank is cemented carbide.

[0014] A circular cutter, manufactured by a circular cutter machining method.

[0015] The beneficial effects of this application are as follows:

[0016] This application fundamentally eliminates the defect of uncontrollable roundness of the reference inner hole caused by the grinding process in traditional processes by adding a high-precision, micro-cutting inner hole rework process after the fine grinding process and before the cutting edge grinding process. This method can obtain a precision reference inner hole with extremely small roundness error, which serves as the sole reliable reference for subsequent cutting edge grinding. This improvement directly ensures high roundness during the final outer diameter grinding of the cutting edge and high concentricity between the cutting edge and the inner hole, thereby significantly improving the overall geometric accuracy and cutting performance of the circular cutting tool. Attached Figure Description

[0017] Figure 1 A flowchart illustrating a machining method for a circular cutter provided in an embodiment of this application;

[0018] Figure 2 This is a front view of a circular cutter provided in an embodiment of this application;

[0019] Figure 3 for Figure 2 Sectional view at CC;

[0020] Figure 4 For T Figure 3 A magnified view of the area at point B;

[0021] Figure 5 This is a three-dimensional structural schematic diagram of a circular cutter provided in an embodiment of this application; Detailed Implementation

[0022] The specific embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The following examples are used to illustrate this application, but are not intended to limit the scope of this application.

[0023] like Figures 2 to 5 As shown, a circular cutter includes a blade body 1, an inner hole 2 located at the center of the blade body, and a cutting edge 3 located on the outer periphery of the blade body.

[0024] like Figure 1 As shown, a machining method for a circular cutting tool includes sequential processes of rough machining of the inner hole of the tool blank, fine grinding of the inner hole, end face machining, and external cylindrical grinding of the cutting edge. After completing the fine grinding of the inner hole and before starting the external cylindrical grinding of the cutting edge, an additional inner hole datum reworking process is added. The inner hole datum reworking process is as follows: the tool blank, whose inner hole has been finely ground in the previous process, is clamped in a high-precision internal cylindrical grinding machine, and a diamond grinding wheel with a grit size of not less than 800 mesh is used to perform micro-grinding on the finely ground inner hole; a precision datum inner hole with a roundness error of not more than 0.003 mm is obtained, and this precision datum inner hole is directly used as the positioning datum for the subsequent external cylindrical grinding of the cutting edge.

[0025] In one embodiment, during the internal bore datum rework process, the diamond grinding wheel has a grit size of 1500 mesh and a soft hardness. This choice achieves a balance between "fine shaping" and "flexible fit." The ultra-fine 1500 mesh grit ensures extremely shallow cutting depth per abrasive grain, enabling nanoscale material removal. This allows for precise correction of microscopic shape errors in the internal bore (such as roundness deviations), rather than simply improving surface finish. Simultaneously, the "soft" grinding wheel possesses good self-sharpening properties and a degree of elasticity, allowing it to better conform to the microscopic contours of the internal bore surface during grinding. This facilitates contour dressing, avoiding potential "biting" or high-stress cutting caused by an excessively hard wheel, thus protecting the integrity of the internal bore surface. Ultimately, this achieves excellent surface quality while efficiently removing shape errors.

[0026] In one embodiment, the grinding parameters for the internal hole datum rework process are: workpiece spindle speed 3-8 rpm, grinding wheel axial feed rate 0.2-0.5 m / min, and radial feed increment 0.001-0.003 mm. This combination of parameters ensures a "super-stable, low-stress, and highly controllable" grinding state. The extremely low operating speed (3-8 rpm) and slow axial feed (0.2-0.5 m / min) significantly reduce vibration and impact during the grinding process, ensuring the extreme stability of the process system. The micron-level radial feed increment of 0.001-0.003 mm keeps the material removal process completely under precise control, enabling accurate and selective correction of roundness errors and avoiding overcutting or thermal stress concentration caused by excessive feed. These parameters are the key operational guarantee for achieving stable convergence of internal hole roundness to the sub-micron level (≤0.003 mm).

[0027] In one embodiment, the internal bore datum reworking process includes a feedless polishing stage after radial feed, lasting 30 to 90 seconds. This stage is crucial for "accuracy stabilization and surface finishing." After radial feed stops, the grinding wheel and workpiece surface remain in contact and move relative to each other for a certain period. This process effectively eliminates microscopic chatter marks or residual stresses that may be left by previous micro-feed grinding. Through continuous micro-friction and polishing, the internal bore geometry (roundness) is further stabilized and homogenized, and the surface finish (Ra value) is significantly improved. This ensures that the obtained precision datum bore not only meets the requirements in size and shape but also has an optimal surface condition, providing ideal conditions for subsequent high-precision clamping.

[0028] In one embodiment, during the internal bore datum rework process, a high-precision fixture positioned on the outer diameter or end face of the tool blank is used for clamping. The core advantage of this clamping method is "protecting the datum and isolating clamping errors." During datum rework, the fixture is positioned and clamped on the outer diameter or end face of the tool blank, completely avoiding the clamping force acting directly on the inner bore wall to be repaired. This fundamentally prevents elastic or plastic deformation of the inner bore that may be caused by the clamping itself, ensuring that the "rework" process corrects the actual error of the "finished inner bore" rather than introducing new clamping errors. This is a prerequisite for obtaining a true, reliable, and high-precision datum.

[0029] This high-precision fixture employs an improved precision three-jaw chuck structure. Each jaw's clamping surface does not directly contact the outer diameter of the tool blank; instead, an arc-shaped locating block made of cemented carbide or hardened steel is fixed there. The inner arc surface of this locating block is precision ground, and its radius of curvature matches the outer diameter of the tool blank. An adjustable-height precision end-face locating step is set at the center of the chuck. During clamping, the lower end face of the tool blank is first pressed against this step to achieve axial positioning. When the chuck is driven, the three jaws move radially synchronously, gently clamping the outer diameter of the tool blank through the arc-shaped locating blocks and pressing the lower end face of the tool blank firmly against the end-face locating step.

[0030] Its working principle is as follows: the main axial positioning and load bearing are achieved through the end face steps, and the outer circle is centered through the arc-shaped blocks on the jaws. The clamping force is dispersed through the rigid end face and the uniformly contacting outer arc surface, completely avoiding the clamping force acting directly or indirectly on the inner hole wall that needs to be repaired, thus achieving clamping with no deformation and high repeatability positioning accuracy.

[0031] In one embodiment, during the external cylindrical grinding process, a tapered shank or mandrel with a clearance fit or transition fit to the precision reference inner hole is used for clamping. The advantage of this design is that it achieves both precise positioning and damage-free assembly / disassembly. Based on the extremely high roundness of the inner hole obtained after rework, using a mandrel with a precision clearance or transition fit ensures extremely high coaxiality between the workpiece and the mandrel during grinding, thus achieving accurate reference transfer; it also avoids the disassembly difficulties or scratches on the inner hole surface that might result from using an interference fit. This clamping method fully utilizes the advantages of a high-precision reference, ensuring machining accuracy while also considering the operability in actual production and the protection of the machined surface.

[0032] In one embodiment, the circular cutter blank is made of cemented carbide.

[0033] A circular cutter, manufactured by a circular cutter machining method.

[0034] The working principle of this application is as follows:

[0035] At the start of the process, a high-precision fixture based on the outer diameter or end face of the tool blank is used for clamping. This ensures the positional accuracy of the tool blank in the machine tool coordinate system, while avoiding new clamping deformation introduced by the clamping force acting directly on the already finely ground inner hole wall, providing a stable starting point for "rework". A diamond grinding wheel with extremely high grit (≥800 mesh, preferably 1500 mesh) and relatively soft hardness is used. The high grit ensures a very small cutting edge and extremely low single-pass cutting amount, achieving material removal at the nanometer to submicron level; the soft grinding wheel has good self-sharpening and elastic yielding properties, better adapting to the micro-shape of the inner hole for contour dressing rather than forced cutting. Extremely low spindle speed (3-8 rpm) and slow axial feed (0.2-0.5 m / min) ensure a smooth grinding process and minimize heat accumulation. Each minute radial feed of 0.001-0.003 mm allows the grinding wheel to progressively and selectively remove microscopic protrusions or shape deviations on the surface of the finely ground inner hole caused by random grinding, thereby systematically correcting roundness errors.

[0036] The final stage, feedless grinding (30-90 seconds), utilizes the continuous micro-friction and polishing action between the grinding wheel and the workpiece surface to further homogenize surface stress, stabilize the obtained geometry, and ultimately converge and lock the roundness of the inner hole within a high-precision range of ≤0.003mm. The "precision reference inner hole" obtained in this step has a significantly higher geometric accuracy (roundness) than an inner hole that has only undergone fine grinding.

[0037] When performing external cylindrical grinding of the cutting edge, a tapered shank or mandrel with a precision clearance fit or transition fit to the "precision reference inner hole" is used for clamping. Because the reference inner hole itself has extremely high roundness, the workpiece rotation axis during cutting edge grinding is highly coincident with the geometric center line of the reference inner hole.

[0038] Based on this highly concentric clamping configuration, the grinding wheel of the universal tool grinder can accurately reflect the design contour when grinding the outer diameter and angle of the cutting edge. The workpiece rotational eccentricity previously caused by datum error (inner hole roundness difference) is greatly suppressed, resulting in excellent roundness of the ground cutting edge outer diameter. Furthermore, its concentricity with the inner hole (typically reaching 0.015mm or higher) is directly guaranteed by the accuracy of the reconstructed datum inner hole.

[0039] The embodiments described above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make several improvements and substitutions without departing from the technical principles of this application, and these improvements and substitutions should also be considered within the scope of protection of this application.

Claims

1. A method for machining a circular cutting tool, comprising sequentially performing rough machining of the tool blank's inner hole, fine grinding of the inner hole, end face machining, and external grinding of the cutting edge, characterized in that, After completing the inner hole fine grinding process and before starting the cutting edge outer cylindrical grinding process, an additional inner hole datum rework process is added. The inner hole datum rework process is as follows: the tool blank whose inner hole has been finely ground in the previous process is clamped in a high-precision internal grinding machine, and a diamond grinding wheel with a grit size of not less than 800 mesh is used to perform micro-grinding on the finely ground inner hole; a precision datum inner hole with a roundness error of not more than 0.003mm is obtained, and this precision datum inner hole is directly used as the positioning datum for subsequent cutting edge external grinding; The grinding parameters for the internal bore datum repair process are: workpiece spindle speed 3-8 rpm, grinding wheel axial feed speed 0.2-0.5 m / min, and radial feed amount 0.001-0.003 mm per pass.

2. The machining method of the circular cutter according to claim 1, characterized in that, In the internal bore reference repair process, the diamond grinding wheel has a grit size of 1500 mesh and a hardness of soft.

3. The processing method of the circular cutter according to claim 1, characterized in that, After completing the radial feed, the internal bore reference repair process also includes a no-feed polishing stage, with a polishing time of 30 to 90 seconds.

4. The machining method of the circular cutter according to claim 1, characterized in that, When performing the inner hole reference repair process, a high-precision fixture is used for clamping, which is positioned by the outer circle or end face of the tool blank.

5. The machining method of the circular cutter according to claim 1, characterized in that, When performing the aforementioned external cylindrical grinding process, a tapered shank or mandrel that maintains a clearance fit or transition fit with the precision reference inner hole is used for clamping.

6. The machining method of the circular cutter according to claim 1, characterized in that, The circular cutter blank is made of cemented carbide.

7. A circular cutter, characterized in that, The circular cutter is manufactured by the processing method according to any one of claims 1 to 6.

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