A variable helix angle indexable shallow hole drill and drilling method

Abstract

This invention discloses a variable helix angle indexable shallow hole drill and drilling method. The outer circumference of the tool holder has a variable helix angle structure with the helix angle gradually decreasing from the top to the root of the tool holder. The inner insert has a radial offset and a radial displacement. The radial surface of the outer insert is used as a reference surface, and an axial rotation angle is set between the inner and outer inserts. Cooling holes are formed by a Y-shaped distribution from one cooling hole at the end of the tool holder to two cooling holes at the top of the tool holder, with the cooling hole at the end of the tool holder connected to the two cooling holes at the top of the tool holder. The hole depth is divided into different feed segments according to the tool diameter. Feeding stops when the tool tip reaches the boundary of each feed segment. At the stop point, the tool continues to rotate at a constant speed. After a fixed stop time, the tool feed speed is reduced while the tool speed remains constant to continue machining in the next feed segment until the root of the tool holder is reached and then feed stops. This facilitates rapid and smooth chip removal, improves the stability of the tool cutting process, and enhances machining accuracy.

Description

Technical Field

[0001] This invention relates to the field of machining tool design and manufacturing, specifically to a variable helix angle indexable shallow hole drill and its drilling method. Background Technology

[0002] With the advancement and development of the manufacturing industry, indexable shallow hole drills are increasingly being used in hole machining. High surface finish, smooth chip removal, and balanced radial forces are important standards for evaluating the cutting performance of indexable shallow hole drills. Manufacturers often encounter a series of problems when machining holes using traditional indexable shallow hole drills with a constant helix angle, such as poor stability during hole machining, susceptibility to vibration, and chip clogging and poor chip removal as the hole depth increases.

[0003] Currently, the process for hole machining using indexable shallow hole drills is based on traditional fixed cutting parameters. This method is prone to problems such as radial force imbalance and excessive axial force, leading to reduced product surface finish and tool life. These issues result in decreased product quality and tool damage, thus affecting normal machining operations. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, the first technical problem to be solved by the present invention is to provide a variable helix angle indexable shallow hole drill. After machining metal products with this variable helix angle indexable shallow hole drill, it helps to remove chips quickly and smoothly, and improves the stability of the cutting process and the machining accuracy.

[0005] The second technical problem to be solved by the present invention is to provide a feeding drilling method for a variable helix angle indexable shallow hole drill, which is beneficial to the discharge of residual chips in the hole, avoids chip blockage, reduces the axial force of the tool, thereby reducing tool wear and extending the tool service life.

[0006] The technical solution adopted in this invention is:

[0007] A variable helix angle indexable shallow hole drill, characterized by comprising:

[0008] The tool holder has two helical grooves on its outer circumference. The helical grooves are a variable helical angle structure that gradually decreases from the top of the tool holder to the root of the tool holder.

[0009] The inner blade is fixedly mounted at the center of the top of the tool holder and located in one of the spiral grooves. The inner blade is provided with radial overcenter distance and radial overcenter amount.

[0010] The outer blade is fixedly mounted on the top edge of the guide rod and located in another spiral groove. The inner and outer blades are of the same model and both have a cutting inclination angle. The radial surface of the outer blade is used as the reference surface, and an axial rotation angle is set between the inner and outer blades.

[0011] The cooling holes extend in a Y-shape from one cooling hole at the end of the cutter to the top of the cutter shank, forming two cooling holes. The cooling hole at the end of the cutter is connected to the two cooling holes at the top of the cutter shank.

[0012] In the above technical solution, the maximum helix angle at the top of the tool holder is 15° to 20°, and the minimum helix angle at the root of the tool holder is 5° less than the helix angle at the top of the tool holder.

[0013] In the above technical solution, the radial overcenter distance of the inner blade is 0.1mm to 0.3mm, and the radial overcenter amount is 0.3mm to 0.4mm.

[0014] In the above technical solution, the angle between the two cooling holes at the top of the tool holder and the axis of the tool body is 14° to 16°.

[0015] In the above technical solution, the two blades are provided with an axial height difference along the blade body axis.

[0016] In the above technical solution, the radial surface of the outer blade is used as the reference surface, and the axial rotation angle between the inner blade and the outer blade is set to 3° to 5°.

[0017] In the above technical solution, the back angle of each blade is 10° to 12°.

[0018] In the above technical solution, the radius of the blade tip arc is 0.3mm to 0.5mm.

[0019] A method for drilling shallow holes using a variable helix angle indexable shallow hole drill is characterized by the following: using the aforementioned variable helix angle indexable shallow hole drill, the hole depth is divided into different feed segments according to the tool diameter. Feeding stops when the tool head reaches the junction of each feed segment. At the stop point, the tool continues to rotate at a constant speed. After a fixed stop time, the tool feed speed is reduced while maintaining a constant tool speed to continue processing in the next feed segment until the tool shank root is reached and then feeding stops.

[0020] With different cutting tools, the hole depth of each tool's diameter is one feed segment.

[0021] In the above technical solution, the depth values ​​of each feed section decrease sequentially.

[0022] Therefore, an intermittent variable cutting parameter method is used during hole machining. When the cutter reaches different set depths, the feed stops, but the spindle continues to rotate at a constant speed. The stopping time is fixed. Then, the feed rate is reduced, but the machine spindle speed remains constant, and drilling continues. This intermittent machining method allows for the removal of residual chips from the hole during intermittent rotation, preventing chip blockage and improving workpiece surface finish. The variable cutting parameter method also reduces the axial force on the tool, thus extending tool life.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The variable helix angle indexable shallow hole drill of the present invention adopts a variable helix angle structure of the tool holder, which can reduce the chip removal distance and increase the axial speed, which helps to remove chips quickly and smoothly, improves the processing efficiency, and effectively reduces the high chatter during drilling, making the drilling process more stable.

[0025] 2) By setting the radial distance of the inner insert, the axial rotation angle and the inclination angle, the inclination angle of the outer insert and the height difference between the inner and outer inserts, the placement of the inserts under these conditions can meet the requirements of reducing cutting force and ensuring radial force balance during machining.

[0026] 3) During hole machining, an intermittent variable cutting parameter method is used. When drilling reaches different set depths, the tool stops feeding but continues to rotate at a constant speed. The stop time is fixed. Then, the feed rate is reduced, but the machine spindle speed remains constant, and drilling continues. Using this intermittent machining method, the intermittent rotation of the tool facilitates the removal of residual chips from the hole, avoids chip clogging, and thus improves the surface finish of the workpiece. The variable cutting parameter method reduces the axial force on the tool, thereby extending the tool's service life.

[0027] 4) Set the feed section according to the matching of the tool diameter multiple and the hole depth to achieve precise machining and reduce energy consumption. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0029] Figure 1 This is a schematic diagram of the overall structure of the variable helix angle indexable shallow hole drill of the present invention.

[0030] Figure 2 This is a schematic diagram of the cross-sectional structure of the variable helix angle indexable shallow hole drill of the present invention (the purpose of selecting the section line perpendicular to the helix is ​​to inspect the dimensions after the tool is manufactured).

[0031] Figure 3 This is a top view of the cutter head structure of the variable helix angle indexable shallow hole drill of the present invention.

[0032] Figure 4 yes Figure 3 A magnified view of a portion of region A.

[0033] Figure 5 This is a side view of the cutter head structure of the variable helix angle indexable shallow hole drill of the present invention.

[0034] Figure 6 This is a schematic diagram of the variable helix structure of the variable helix angle indexable shallow hole drill of the present invention.

[0035] Figure 7This is a schematic diagram of the cooling hole structure of the variable helix angle indexable shallow hole drill of the present invention.

[0036] Figure 8 This is a schematic diagram of the intermittent variable cutting parameter machining method for the variable helix angle indexable shallow hole drill of the present invention.

[0037] Figure 9 This is a simulation result of the axial force during intermittent variable cutting parameter machining of the variable helix angle indexable shallow hole drill of this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0039] Example 1:

[0040] Combination Figure 1-5 As shown, Figure 1 This is a schematic diagram of the overall structure of a variable helix angle indexable shallow hole drill according to an embodiment of the present invention. It includes an inner blade 1 located at the center of the top of the tool holder, an outer blade 2 located at the outer edge of the top of the tool holder, a blade fixing member 3, and a tool holder 4. The inner blade 1 and the outer blade 2 are of the same type and have a cutting edge inclination angle; for example... Figure 3 The inner blade 1 is provided with radial overcenter distance and radial overcenter amount.

[0041] The inner blade 1 is preferably configured with a radial overcenter distance of 0.1mm to 0.3mm and a radial overcenter amount of 0.3mm to 0.4mm.

[0042] Combination Figure 6 As shown, the two chip removal grooves 41 of the tool holder body 4 adopt a variable helix angle structure. The helix angle at the end of the tool holder is the maximum of 15° to 20°, and the helix angle at the root is the minimum of (A-5)°.

[0043] The inner blade 1 is configured to have an axial height difference relative to the outer blade 2; for example... Figure 3 Using the radial surface of the outer blade 2 as a reference surface, an axial rotation angle is provided between the inner blade 1 and the outer blade 2. Preferably, using the radial surface of the outer blade 2 as a reference surface, an axial rotation angle of 3° to 5° is provided between the inner blade 1 and the outer blade 2.

[0044] like Figure 3-5 The inner blade 1 and the outer blade 2 are of the same model and have a blade back angle of 10° to 12° and a blade tip radius of 0.3mm to 0.5mm.

[0045] The inner blade 1 has a radial overcenter of 0.3mm to 0.4mm, an axial rotation angle of 3° to 5°, and a cutting edge inclination angle of 3° to 6°. The outer blade 2 has a cutting edge inclination angle of 2° to 5° and a height difference between the inner and outer blades of 0.17mm to 0.19mm.

[0046] like Figure 7 As shown, the tool holder 4 is provided with a Y-shaped cooling hole 6 inside. The cooling hole 6 gradually divides into two cooling holes from one cooling hole at the tail of the tool to the head of the tool. The angle between the two cooling holes and the axis of the tool body is 14° to 16°.

[0047] The blade holder 3 can be made of a common screw. In this embodiment, the screw type is M2.2.

[0048] In the optimal embodiment, the radial through-center distance of the inner insert of the variable helix angle indexable shallow hole drill is 0.3mm to 0.4mm, the axial rotation angle is 3° to 5°, and the cutting edge inclination angle is 3° to 6°. The cutting edge inclination angle of the outer insert is 2° to 5°, and the height difference between the inner and outer inserts is 0.17mm to 0.19mm. Under these conditions, the placement of the inserts can meet the requirements of reducing cutting force and ensuring radial force balance during machining.

[0049] The variable helix angle structure of this invention is established based on the following gradually changing helix model:

[0050]

[0051] in, ρ(z) represents the rotation angle in degrees; ρ(z) represents the tool radius in mm. β0 is the initial helix angle in degrees; k is the change in helix angle from the end to the root; L is the axial length of the helix in mm; z is the axial length of the current point in mm.

[0052] Meanwhile, the variable helix angle structure of this invention satisfies the generalized helix angle model.

[0053] Where β is the helix angle, in degrees; V a V represents the axial velocity at any point on the helix, in mm / s. r V represents the radial velocity at any point on the helix, in mm / s. t The tangential velocity at any point on the helix is ​​expressed in mm / s. The axial height of any point on the helix is ​​expressed in mm. The radius of tool rotation is in mm. ω is the angular velocity, and its unit is rad / s.

[0054] The helix angle decreases uniformly from the end to the root. This structure can reduce the chip removal distance, increase the axial speed, and increase the chip removal speed, which helps to remove chips quickly and smoothly, and improves the stability and machining accuracy of the cutting process.

[0055] The present invention also provides a feeding method for a variable helix angle indexable shallow hole drill. In the process of drilling the hole, an intermittent machining method and a variable cutting parameter method are combined. When drilling to different set depths, the tool stops feeding, but the tool continues to rotate at a constant speed. The tool stop time is fixed. Then the feed speed is reduced, but the machine tool spindle speed remains unchanged to continue drilling.

[0056] Combination Figure 8 As shown, when the variable helix angle indexable shallow hole drill bit reaches positions a, b, c, and d, the tool stops feeding but continues to rotate at a constant speed. The stopping time is fixed, and then the parameters are changed to continue machining. Specifically, the feed rate for machining stage H1 is f1, and the spindle speed is n; the feed rate for machining stage H2 is f2, and the spindle speed is n; the feed rate for machining stage H3 is f3, and the spindle speed is n; the feed rate for machining stage H4 is f4, and the spindle speed is n; and the feed rate for machining stage H5 is f5, and the spindle speed is n. The order of f1 > f2 > f3 > f4 > f5 is f5, and the spindle speed n remains constant throughout the drilling process. Using an intermittent machining method, the intermittent rotation of the tool facilitates the removal of residual chips from the hole, avoids chip clogging, and thus improves the surface finish of the workpiece. Using variable cutting parameters reduces the axial force on the tool, thereby extending the tool's service life.

[0057] Combination Figure 9 As shown, the variable cutting parameter feed process of a variable helix angle indexable shallow hole drill is simulated and analyzed using ABAQUS software.

[0058] First, create tool and workpiece models in UG software and import them into ABAQUS as SAT format files for assembly. Define the workpiece material as 42CrMo steel and the insert material as cemented carbide. Second, set the analysis step type to "Dynamic, Temperature-Displacement, Explicit", and divide the insert mesh type as "C3D4T: Four-node thermally coupled tetrahedral element" and the workpiece mesh type as "C3D8RT: Eight-node thermally coupled hexahedral element". Then, define the contact property as "Surface to Surface Contact". During the load creation process, the first stage is set to the initial parameter working condition 0.25s before the drilling process, at which time the spindle rotates... The first stage involves a spindle speed (n) of 3200 r / min and a feed rate of 320 mm / min. The second stage, from 0.25 s to 0.3 s, is a tool intermittent process where the tool rotates at 3200 r / min without feeding. The third stage, after 0.3 s, is a variable-parameter drilling process, with the spindle speed (n) at 3200 r / min and the feed rate at 256 mm / min. The job was created and analyzed. The results show that the average peak axial force in the first stage was 1290 N, the axial force in the second stage was almost zero, and the average peak axial force in the third stage decreased to 973 N. Therefore, using variable cutting parameters can effectively reduce axial force and thus improve tool life.

[0059] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A variable helix angle indexable shallow hole drill, characterized in that... include: The tool holder has two helical grooves on its outer circumference. The helical grooves are a variable helical angle structure that gradually decreases from the top of the tool holder to the root of the tool holder. The maximum helix angle at the top of the tool holder is 15° to 20°, and the minimum helix angle at the root of the tool holder is 5° less than the helix angle at the top of the tool holder. The inner blade is fixedly installed at the center of the top of the tool holder and located in one of the spiral grooves. The inner blade has a radial centering distance and a radial centering amount. The radial centering distance of the inner blade is 0.1mm to 0.3mm, and the radial centering amount is 0.3mm to 0.4mm. The outer blade is fixedly mounted on the top edge of the guide rod and located in another spiral groove; the inner and outer blades are of the same model and both have a cutting inclination angle; the inner blade cutting inclination angle is 3° to 6°; the outer blade cutting inclination angle is 2° to 5°. Using the radial surface of the outer blade as a reference surface, the inner blade and the outer blade are set to have an axial rotation angle of 3° to 5°. The inner and outer blades are provided with an axial height difference along the axis of the blade body; The cooling holes extend in a Y-shape from one cooling hole at the end of the cutter to the top of the cutter shank, forming two cooling holes. The cooling hole at the end of the cutter is connected to the two cooling holes at the top of the cutter shank.

2. The variable helix angle indexable shallow hole drill according to claim 1, characterized in that... The two cooling holes at the top of the tool holder are at an angle of 14° to 16° with the axis of the tool body.

3. The variable helix angle indexable shallow hole drill according to claim 1, characterized in that... The radius of the tip arc of each blade is 0.3mm to 0.5mm.

4. The variable helix angle indexable shallow hole drill according to claim 1, characterized in that... The back angle of each blade is 10° to 12°.

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