PCB corner hole lamination avoidance type drilling and deburring processing technology

Abstract

This invention discloses a PCB corner hole stacking avoidance drilling and deburring process, including the following steps: S1: Straight drilling area processing; S2: Right-angle corner area optimization; S3: Overall path planning; S4: EA dedicated slotting tool selection and matching; S5: Two-pass graded differentiated cutting parameter setting; S6: Slot hole composite avoidance cycle processing; S7: Finished product quality inspection and control: After processing, the straight hole openings are inspected to be free of burrs and flash, the corner slot walls are smooth without delamination and edge bursting, and the hole size and slot shape tolerances meet the standards. No further manual grinding or deburring is required, and the hole can directly flow into the next process. This invention solves the problem that traditional processes generally use continuous circular stacking of tools in the same direction or dense overlapping hole design, where the tool needs to repeatedly cut in the same area. However, the resin and fiberglass substrates at the corners are easily subjected to repeated extrusion and tearing, resulting in defects such as burrs at the hole openings, flash on the hole edges, substrate delamination and edge bursting, rough hole walls, copper foil tearing, and hole position misalignment.

Description

Technical Field

[0001] This invention belongs to the field of deburring technology, and particularly relates to a PCB corner hole stack-avoidance drilling deburring process. Background Technology

[0002] In the field of printed circuit board (PCB) manufacturing, dense drilling in L-shaped corner areas is a typical challenge in the precision machining of multilayer boards. Traditional machining processes typically employ continuous, overlapping circular cutting paths or densely overlapping hole designs in the same direction to achieve hole connections in corner areas, requiring the tool to repeatedly cut within the same region. However, the resin and fiberglass substrates in irregularly shaped corner areas of PCBs are highly susceptible to the following problems under repeated pressure and tearing from the tool:

[0003] I. Defects at the orifice and the hole wall: The substrate at the corner is squeezed and deformed, forming heavy burrs at the orifice and burrs on the hole edge, and may even cause substrate delamination and edge bursting; overlapping toolpaths can easily aggravate tool wear and heat, resulting in poor hole wall roughness, scratches on the inner copper foil, and hole position deviation exceeding tolerance.

[0004] II. Potential problems in subsequent processes: After processing, manual deburring is required, which is extremely inefficient and costly. It can also easily damage the holes and lines of the finished product, resulting in batch scrap. Mechanical brushing and sanding can only treat the surface of the groove. The inner side of the L-shaped corner and the dead corner of the groove depth cannot be cleaned. Excessive corrosion can also damage the substrate and cause dimensional deformation.

[0005] III. Equipment and Consumable Limitations: Existing optimization solutions mostly rely on high-end specialized drilling equipment or customized consumables. Due to the high cost of equipment modification and poor compatibility of consumables, small and medium-sized PCB enterprises find it difficult to widely apply these solutions. Summary of the Invention

[0006] The purpose of this invention is to address the challenge of dense drilling in the L-shaped corner area during PCB manufacturing, a typical difficulty in the precision machining of multilayer boards. Traditional processes generally employ continuous circular overlapping cutting or densely overlapping hole designs in the same direction, requiring the tool to repeatedly cut in the same area. Under repeated extrusion and tearing, the resin and fiberglass substrates at the corners are prone to defects such as burrs at the hole openings, burrs on the hole edges, substrate delamination and edge bursting, rough hole walls, copper foil tearing, and hole misalignment. Subsequent manual deburring is inefficient, costly, and easily damages the finished product. Mechanical brushing cannot clean the inner side of the L-shaped corner and the dead corners of the groove depth, and excessive processing can also lead to substrate dimensional deformation. Existing optimization solutions mostly rely on high-end specialized equipment or customized consumables, which are difficult for small and medium-sized PCB enterprises to widely apply due to high modification costs and poor consumable compatibility. Therefore, this invention proposes a PCB corner hole stacking avoidance drilling deburring process.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a PCB corner hole stack-overlapping avoidance drilling and deburring process, comprising the following steps:

[0008] S1: Processing of straight drilling area: Reduce the standard design diameter of the straight drilling area of ​​the PCB by 0.1mm and process it by staggered reciprocating drilling.

[0009] S2: Right-angle corner area optimization: Abandon the original densely overlapping hole structure and optimize the corner point to EA arc transition groove structure. The arc groove smoothly connects the horizontal and vertical straight drilling trajectories, eliminating the stress concentration at the corner and the squeeze of overlapping holes.

[0010] S3: Overall toolpath planning: small-diameter circulating drilling in straight sections, smooth transition of EA grooves in corner sections, and use red and blue layered bidirectional alternating toolpaths to avoid continuous repeated cutting at the same position;

[0011] S4: EA dedicated slotting cutter selection and matching: Select PCB dedicated EA slotting cutter to adapt to corner slots + repeated drilling composite machining;

[0012] S5: Two-pass graded differentiated cutting parameter settings:

[0013] S5a: First pass of root drilling: Low speed, low feed, and small cutting amount are used to stabilize the hole position at low speed and avoid extrusion and deformation of the substrate;

[0014] S5b: Second pass finishing drill: Simultaneously increase spindle speed, feed rate, and layered cutting amount, optimize oil and gas cooling pressure, and quickly finish the hole wall and remove residual burrs;

[0015] S5c: EA Groove Corner Exclusive Parameters: Individually matches the EA groove tool arc feed parameters, reduces corner feed by 30%, increases spindle speed, smooths arc cutting, and eliminates groove wall chipping, burrs, and nodules;

[0016] S6: Composite avoidance cycle machining of slots and holes: Prioritize completing two rounds of small-diameter repeated drilling on straight sections, and then machine the EA arc groove at the corner; the EA groove cutter in the corner groove area moves clockwise and counterclockwise in a bidirectional arc reciprocating motion, with interval avoidance cycle cutting to disperse the concentrated heat and compressive stress at the corner; the entire process is monitored for tool breakage and wear online, and the corner groove machining shortens the EA groove cutter replacement cycle, avoiding secondary burrs caused by dull tool tearing;

[0017] S7: Finished Product Quality Control: After processing, straight holes are inspected to be free of burrs and flash, corner groove walls are smooth without delamination or edge bursting, and hole dimensions and groove shape tolerances meet the standards. No further manual grinding or deburring is required, and the product can directly flow into the next process.

[0018] Furthermore, in step S4a, the coating of the carbide-coated EA grooving tool is EA coating, and the tool specifications are matched to a hole diameter and corner groove width reduced by 0.1mm.

[0019] Furthermore, in step S5a, the spindle speed for the first pass of drilling is 95krpm, the feed rate is 0.4m / min, the retraction speed is 15m / min, and the drilling is performed at a slow speed.

[0020] Furthermore, in step S5b, the spindle speed of the second finishing drill is 105krpm, the feed rate is 1.5m / min, the retraction speed is 15m / min, and cutting is added.

[0021] Furthermore, in step S5c, the spindle speed of the corner EA groove is 85krpm, the feed rate is 0.4%, and the cutting is a gentle circular arc.

[0022] Furthermore, the processing object is a FR-4 PCB with 2-4 or more layers, featuring densely packed L-shaped slots and corners.

[0023] Further, step S4 includes:

[0024] S4a: The tool specifications are matched with a hole diameter and corner groove width reduced by 0.1mm. It adopts a carbide-coated EA grooving tool to ensure a high rigidity cutting edge structure and is compatible with both drilling and cutting and arc groove milling.

[0025] S4b: Optimized tool rigidity, shortened cutting edge length, enhanced corner impact resistance, and eliminated corner cutting issues such as tool bounce, edge chipping, and tool breakage.

[0026] This invention provides a PCB corner hole stack-avoidance drilling deburring process. It reduces the standard hole diameter in straight drilling areas by 0.05mm to 0.15mm, dispersing cutting stress through "offset reciprocating drilling." In right-angle corner areas, densely overlapping holes are eliminated, replaced by an EA arc transition groove structure. The smoothness of the arc eliminates stress concentration at sharp corners and avoids overlapping and squeezing of holes. A carbide-coated EA groove milling cutter is selected, its specifications matching the reduced hole diameter and corner groove width. Impact resistance is optimized by "shortening the cutting edge and enhancing rigidity." It is compatible with both "drilling and cutting" and "arc groove milling" working conditions, eliminating corner tool bounce, chipping, and tool breakage. During the graded cutting process, low speed, low feed, and small depth of cut are used. The cutting depth is low and stable to form the hole position, avoiding the extrusion deformation of the substrate. The spindle speed, feed rate and layered cutting depth are increased. With oil and gas cooling, the hole wall is quickly smoothed and residual burrs are removed. The feed rate at corners is reduced and the spindle speed is increased. The tool is controlled to move back and forth in both clockwise and counterclockwise along the arc to disperse the heat and extrusion stress at the corner. The straight section adopts "red and blue layered bidirectional alternating toolpath" to avoid continuous repeated cutting at the same position. In the corner area, the straight section is drilled twice before machining the EA arc groove. The EA groove tool moves back and forth in both clockwise and counterclockwise, with interval avoidance and cyclic cutting to further disperse stress. The tool breakage and wear monitoring is on throughout the process to shorten the replacement cycle of the EA groove tool when machining the corner groove and avoid the secondary burrs caused by the dull tool tearing.

[0027] Therefore, this embodiment has the following advantages compared to the prior art:

[0028] A new deburring process for PCB corner holes using a stacked, avoidance-type drilling method solves the problem of dense drilling in the L-shaped corner area, a typical challenge in the precision machining of multilayer boards. Traditional processes generally use continuous, circular, stacked cutting tools or densely overlapping hole designs, requiring the tool to repeatedly cut in the same area. Under repeated extrusion and tearing, the resin and fiberglass substrates at the corners are prone to defects such as burrs at the hole openings, burrs on the hole edges, substrate delamination and edge bursting, rough hole walls, copper foil tearing, and hole misalignment. Subsequent manual deburring is inefficient, costly, and easily damages the finished product. Mechanical brushing cannot clean the inner side of the L-shaped corner and the dead corners of the groove depth, and over-processing can also lead to substrate dimensional deformation. Existing optimized solutions mostly rely on high-end specialized equipment or customized consumables, which are difficult for small and medium-sized PCB enterprises to widely adopt due to high modification costs and poor consumable compatibility. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This diagram illustrates the steps of a PCB corner hole stack-out avoidance drilling and deburring process.

[0031] Figure 2 This is a finished product image of a PCB corner hole stack-avoidance drilling and deburring process.

[0032] Figure 3 This is a comparison diagram of the original process and the process of this application for a PCB corner hole stack-out avoidance drilling and deburring process. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0037] In the description of the embodiments of the present invention, it should be noted that the terms "upper" and "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] Example 1:

[0040] Please see Figure 1-3 This invention provides a technical solution: a PCB corner hole stack-avoidance drilling and deburring process, comprising the following steps:

[0041] S1: Processing of straight drilling area: Reduce the standard design diameter of the straight drilling area of ​​the PCB by 0.1mm and process it by staggered reciprocating drilling.

[0042] S2: Right-angle corner area optimization: Abandon the original densely overlapping hole structure and optimize the corner point to EA arc transition groove structure. The arc groove smoothly connects the horizontal and vertical straight drilling trajectories, eliminating the stress concentration at the corner and the squeeze of overlapping holes.

[0043] S3: Overall toolpath planning: small-diameter circulating drilling in straight sections, smooth transition of EA grooves in corner sections, and use red and blue layered bidirectional alternating toolpaths to avoid continuous repeated cutting at the same position;

[0044] S4: EA dedicated slotting cutter selection and matching: Select PCB dedicated EA slotting cutter to adapt to corner slots + repeated drilling composite machining;

[0045] S5: Two-pass graded differentiated cutting parameter settings:

[0046] S5a: First pass of root drilling: Low speed, low feed, and small cutting amount are used to stabilize the hole position at low speed and avoid extrusion and deformation of the substrate;

[0047] S5b: Second pass finishing drill: Simultaneously increase spindle speed, feed rate, and layered cutting amount, optimize oil and gas cooling pressure, and quickly finish the hole wall and remove residual burrs;

[0048] S5c: EA Groove Corner Exclusive Parameters: Individually matches the EA groove tool arc feed parameters, reduces corner feed by 30%, increases spindle speed, smooths arc cutting, and eliminates groove wall chipping, burrs, and nodules;

[0049] S6: Composite avoidance cycle machining of slots and holes: Prioritize completing two rounds of small-diameter repeated drilling on straight sections, and then machine the EA arc groove at the corner; the EA groove cutter in the corner groove area moves clockwise and counterclockwise in a bidirectional arc reciprocating motion, with interval avoidance cycle cutting to disperse the concentrated heat and compressive stress at the corner; the entire process is monitored for tool breakage and wear online, and the corner groove machining shortens the EA groove cutter replacement cycle, avoiding secondary burrs caused by dull tool tearing;

[0050] S7: Finished Product Quality Control: After processing, straight holes are inspected to be free of burrs and flash, corner groove walls are smooth without delamination or edge bursting, and hole dimensions and groove shape tolerances meet the standards. No further manual grinding or deburring is required, and the product can directly flow into the next process.

[0051] First, by minimizing the diameter of the straight section holes by 0.05mm to 0.15mm and introducing EA arc transition grooves to replace the traditional sharp-corner overlapping holes, stress concentration at geometric tips is eliminated, reconstructing a smooth mechanical transmission path. Second, a two-stage cutting strategy is used: the first stage is a low-stress undercut to reduce substrate extrusion, and the second stage is a high-speed finishing process to remove excess material and cut the fiber edges. Finally, combined with red and blue layered bidirectional toolpaths and forward and reverse bidirectional reciprocating avoidance cycles in corner areas, the tool is forced to work in a discontinuous cutting state, effectively dispersing instantaneous heat load and mechanical extrusion force. Thus, high-quality machining with smooth hole walls and no burrs at corners is achieved without relying on high-end equipment and subsequent manual grinding.

[0052] Specifically, see Figure 1-3 In step S4a, the carbide-coated EA grooving tool has an EA coating, and the tool specifications are matched to a hole diameter and corner groove width reduced by 0.1mm. This ensures that the cutting edge is compatible with the mechanical conditions of drilling and milling circular grooves simultaneously.

[0053] Specifically, see Figure 1-3 In step S5a, the spindle speed for the first pass of drilling is 95krpm, the feed rate is 0.4m / min, the retraction speed is 15m / min, and the drilling is performed at a slow speed.

[0054] This invention provides a PCB corner hole stack-avoidance drilling deburring process. It reduces the standard hole diameter in straight drilling areas by 0.05mm to 0.15mm, dispersing cutting stress through "offset reciprocating drilling." In right-angle corner areas, densely overlapping holes are eliminated, replaced by an EA arc transition groove structure. The smoothness of the arc eliminates stress concentration at sharp corners and avoids overlapping and squeezing of holes. A carbide-coated EA groove milling cutter is selected, its specifications matching the reduced hole diameter and corner groove width. Impact resistance is optimized by "shortening the cutting edge and enhancing rigidity." It is compatible with both "drilling and cutting" and "arc groove milling" working conditions, eliminating corner tool bounce, chipping, and tool breakage. During the graded cutting process, low speed, low feed, and small depth of cut are used. The cutting depth is low and stable to form the hole position, avoiding the extrusion deformation of the substrate. The spindle speed, feed rate and layered cutting depth are increased. With oil and gas cooling, the hole wall is quickly smoothed and residual burrs are removed. The feed rate at corners is reduced and the spindle speed is increased. The tool is controlled to move back and forth in both clockwise and counterclockwise along the arc to disperse the heat and extrusion stress at the corner. The straight section adopts "red and blue layered bidirectional alternating toolpath" to avoid continuous repeated cutting at the same position. In the corner area, the straight section is drilled twice before machining the EA arc groove. The EA groove tool moves back and forth in both clockwise and counterclockwise, with interval avoidance and cyclic cutting to further disperse stress. The tool breakage and wear monitoring is on throughout the process to shorten the replacement cycle of the EA groove tool when machining the corner groove and avoid the secondary burrs caused by the dull tool tearing.

[0055] Therefore, this embodiment has the following advantages compared to the prior art:

[0056] A new deburring process for PCB corner holes using a stacked, avoidance-type drilling method solves the problem of dense drilling in the L-shaped corner area, a typical challenge in the precision machining of multilayer boards. Traditional processes generally use continuous, circular, stacked cutting tools or densely overlapping hole designs, requiring the tool to repeatedly cut in the same area. Under repeated extrusion and tearing, the resin and fiberglass substrates at the corners are prone to defects such as burrs at the hole openings, burrs on the hole edges, substrate delamination and edge bursting, rough hole walls, copper foil tearing, and hole misalignment. Subsequent manual deburring is inefficient, costly, and easily damages the finished product. Mechanical brushing cannot clean the inner side of the L-shaped corner and the dead corners of the groove depth, and over-processing can also lead to substrate dimensional deformation. Existing optimized solutions mostly rely on high-end specialized equipment or customized consumables, which are difficult for small and medium-sized PCB enterprises to widely adopt due to high modification costs and poor consumable compatibility.

[0057] Example 2:

[0058] See Figure 1-3The figure shows a PCB corner hole stack-avoidance drilling deburring process provided by Embodiment 2 of the present invention. Based on the above embodiments, the following improved technical solutions are made: In step S5b, the spindle speed of the second fine finishing drill is 105krpm, the feed speed is 1.5m / min, the retraction speed is 15m / min, and cutting is added.

[0059] Example 3:

[0060] See Figure 1-3 The figure shows a PCB corner hole stack-avoidance drilling deburring process provided by Embodiment 3 of the present invention. Based on the above embodiments, this embodiment further makes the following improved technical solutions: In step S5c, the spindle speed of the corner EA groove is 85krpm, the feed rate is 0.4%, and the cutting is a smooth arc.

[0061] Example 4:

[0062] See Figure 1-3 The figure shows a PCB corner hole stack-avoidance drilling deburring process provided by Embodiment 4 of the present invention. Based on the above embodiments, the following technical solutions are further improved: the processing object is a 2-4 layer or more FR-4 PCB L-shaped slot corner dense circuit board.

[0063] Example 5:

[0064] See Figure 1-3 The figure illustrates a PCB corner hole stack-out avoidance drilling deburring process provided in Embodiment 5 of the present invention. This embodiment further improves upon the above embodiments by making the following technical solutions: Step S4 includes:

[0065] S4a: The tool specifications are matched with a hole diameter and corner groove width reduced by 0.1mm. It adopts a carbide-coated EA grooving tool to ensure a high rigidity cutting edge structure and is compatible with both drilling and cutting and arc groove milling.

[0066] S4b: Optimized tool rigidity, shortened cutting edge length, enhanced corner impact resistance, and eliminated corner cutting issues such as tool bounce, edge chipping, and tool breakage.

[0067] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A PCB corner hole stack-avoidance drilling and deburring process, characterized in that, Includes the following steps: S1: Processing of straight drilling area: Reduce the standard design diameter of the straight drilling area of ​​the PCB by 0.1mm and process it by staggered reciprocating drilling. S2: Right-angle corner area optimization: Abandon the original densely overlapping hole structure and optimize the corner point to EA arc transition groove structure. The arc groove smoothly connects the horizontal and vertical straight drilling trajectories, eliminating the stress concentration at the corner and the squeeze of overlapping holes. S3: Overall toolpath planning: small-diameter circulating drilling in straight sections, smooth transition of EA grooves in corner sections, and use red and blue layered bidirectional alternating toolpaths to avoid continuous repeated cutting at the same position; S4: EA dedicated slotting cutter selection and matching: Select PCB dedicated EA slotting cutter to adapt to corner slots + repeated drilling composite machining; S5: Two-pass graded differentiated cutting parameter settings: S5a: First pass of root drilling: Low speed, low feed, and small cutting amount are used to stabilize the hole position at low speed and avoid extrusion and deformation of the substrate; S5b: Second pass finishing drill: Simultaneously increase spindle speed, feed rate, and layered cutting amount, optimize oil and gas cooling pressure, and quickly finish the hole wall and remove residual burrs; S5c: EA Groove Corner Exclusive Parameters: Individually matches the EA groove tool arc feed parameters, reduces corner feed by 30%, increases spindle speed, smooths arc cutting, and eliminates groove wall chipping, burrs, and nodules; S6: Composite avoidance cycle machining of slots and holes: Prioritize completing two rounds of small-diameter repeated drilling on straight sections, and then machine the EA arc groove at the corner; the EA groove cutter in the corner groove area moves clockwise and counterclockwise in a bidirectional arc reciprocating motion, with interval avoidance cycle cutting to disperse the concentrated heat and compressive stress at the corner; the entire process is monitored for tool breakage and wear online, and the corner groove machining shortens the EA groove cutter replacement cycle, avoiding secondary burrs caused by dull tool tearing; S7: Finished Product Quality Control: After processing, straight holes are inspected to be free of burrs and flash, corner groove walls are smooth without delamination or edge bursting, and hole dimensions and groove shape tolerances meet the standards. No further manual grinding or deburring is required, and the product can directly flow into the next process.

2. The PCB corner hole stack-overlapping deburring process according to claim 1, characterized in that, In step S4a, the coating of the carbide-coated EA grooving tool is EA coating, and the tool specifications are matched to a hole diameter and corner groove width reduced by 0.1mm.

3. The PCB corner hole stack-overlapping deburring process according to claim 1, characterized in that, In step S5a, the spindle speed for the first pass of drilling is 95krpm, the feed rate is 0.4m / min, the retraction speed is 15m / min, and the drilling is performed at a slow speed.

4. The PCB corner hole stack-overlapping deburring process according to claim 1, characterized in that, In step S5b, the spindle speed of the second finishing drill is 105krpm, the feed rate is 1.5m / min, the retraction speed is 15m / min, and cutting is added.

5. The PCB corner hole stack-avoidance drilling and deburring process according to claim 1, characterized in that, In step S5c, the spindle speed of the corner EA groove is 85krpm, the feed rate is 0.4%, and the cutting is a gentle circular arc.

6. The PCB corner hole stack-overlapping deburring process according to claim 1, characterized in that, The processing target is a FR-4 PCB with 2-4 or more layers, featuring densely packed L-shaped slots and corners.

7. The PCB corner hole stack-avoidance drilling and deburring process according to claim 1, characterized in that, Step S4 includes: S4a: The tool specifications are matched with a hole diameter and corner groove width reduced by 0.1mm. It adopts a carbide-coated EA grooving tool to ensure a high rigidity cutting edge structure and is compatible with both drilling and cutting and arc groove milling. S4b: Optimized tool rigidity, shortened cutting edge length, enhanced corner impact resistance, and eliminated corner cutting issues such as tool bounce, edge chipping, and tool breakage.

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