Method and apparatus for in-machine re-sharpening of twist drills

Abstract

The application provides a method and device for in-situ regrinding of twist drills, wherein the drill bit is fixed to a tool end of a five-axis machine tool, the tool end is fixed to a spindle of the five-axis machine tool, and a polishing device is fixed to a worktable of the five-axis machine tool. The polishing device comprises a grinding wheel with a rotation axis parallel to the spindle. The method comprises: determining the coordinates and vector parameters of any point on a first regrinding curve of the drill bit in a drill bit coordinate system, wherein the vector parameters comprise a normal vector, a tangent vector and a cone generatrix vector, and the drill bit coordinate system is used to calibrate the displacement of the drill bit relative to the grinding wheel; converting the first regrinding curve to a workpiece coordinate system to obtain a second regrinding curve in the workpiece coordinate system, wherein the workpiece coordinate system is used to calibrate the displacement of the worktable relative to the tool end; and controlling the rotation of the grinding wheel and the operation of the five-axis machine tool according to the second regrinding curve to regrind the drill bit. In this way, the twist drill can be polished in the gap of drilling without disassembling the twist drill.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mechanical processing, and particularly relates to a method and device for on-machine regrinding of a twist drill. BACKGROUND

[0002] The twist drill hole forming process is a semi-closed environment, and the chip removal condition is poor and difficult to dissipate heat. The tool is prone to wear, and the hole forming quality rapidly decreases with the aggravation of tool wear, the machining burr increases, the hole roundness deteriorates, and even the chip removal groove is blocked, leading to tool fracture. Therefore, how to control the tool wear within a small range to ensure the processing quality is a problem to be solved in high-quality hole forming processing technology.

[0003] In the related art, the tool is replaced and regrinded before causing serious quality deterioration problems after being used for a certain period of time. In order to reduce the cost of tool regrinding, the tools are usually uniformly collected and regrinded at a tool manufacturing unit.

[0004] However, this method exposes many problems in practical application. First, a large number of spare tools need to be reserved during batch processing, increasing the operating cost of the enterprise. Second, the tool is frequently replaced during finishing to reduce the influence of tool wear on processing quality, but the consistency of the tool, tool clamping errors and the like will cause the processing precision to decrease. SUMMARY

[0005] The present application provides a method and device for on-machine regrinding of a twist drill, aiming at solving the influence of tool wear on processing quality in the prior art.

[0006] To solve the above technical problems, the present application provides a method for on-machine regrinding of a twist drill in a first aspect, the drill head is fixed at a tool end of a five-axis machine tool, the tool end is fixed with a main shaft of the five-axis machine tool, and a polishing device is fixed on a workbench of the five-axis machine tool, the polishing device includes a grinding wheel with a rotation axis parallel to the main shaft, and the method includes:

[0007] In the drill head coordinate system, the coordinates and vector parameters of any point on the first regrinding curve of the drill head are determined, the vector parameters include a normal vector, a tangent vector and a cone generatrix vector, and the drill head coordinate system is used to calibrate the displacement amount of the drill head relative to the grinding wheel;

[0008] The first regrinding curve is converted to a workpiece coordinate system to obtain a second regrinding curve in the workpiece coordinate system, wherein the workpiece coordinate system is used to calibrate the displacement amount of the workbench relative to the tool end;

[0009] The rotation of the grinding wheel is controlled, and the five-axis machine tool is controlled according to the second regrinding curve, so that the drill head is regrinded by the grinding wheel.

[0010] Further, before the controlling the five-axis machine tool to work according to the second grinding curve to grind the drill bit by the grinding wheel, the method further comprises:

[0011] controlling the worktable to move until the straight cutting edge of the drill bit is in parallel abutment with the outer peripheral surface of the grinding wheel;

[0012] the controlling the five-axis machine tool to work according to the second grinding curve to grind the drill bit by the grinding wheel comprises:

[0013] taking the position where the straight cutting edge of the drill bit is in parallel abutment with the outer peripheral surface of the grinding wheel as the origin of the workpiece coordinate system;

[0014] controlling the worktable of the five-axis machine tool to move from the origin of the workpiece coordinate system according to the second grinding curve.

[0015] Further, before the controlling the worktable to move until the straight cutting edge of the drill bit is in parallel abutment with the outer peripheral surface of the grinding wheel, the method further comprises:

[0016] determining the angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system;

[0017] controlling the spindle of the five-axis machine tool to rotate according to the angle, so that the drill bit coordinate system coincides with the three-axis direction of the workpiece coordinate system.

[0018] Further, the worktable is provided with an image acquisition device, and the determining the angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system comprises:

[0019] acquiring a picture of the straight cutting edge of the drill bit by the image acquisition device;

[0020] determining the angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system according to the picture.

[0021] Further, the method further comprises:

[0022] after machining the flank face on one side of the drill bit, rotating the spindle of the five-axis machine tool by 180 degrees, and repeating the controlling the grinding wheel to rotate and the controlling the worktable of the five-axis machine tool to move according to the second grinding curve to grind the drill bit by the grinding wheel while the drill bit is fixed.

[0023] Further, the converting the first grinding curve to the workpiece coordinate system to obtain the second grinding curve in the workpiece coordinate system comprises:

[0024] According to the first grinding curve and a conversion relationship matrix, the second grinding curve is obtained, wherein the conversion relationship matrix T is:

[0025]

[0026] Wherein, e Scx , e Scy , e Scz are components of the unit cone generatrix vector at the point M in the x, y, z axes, e Vcx , e Vcy , e Vcz are components of the unit tangent vector at the point M in the x, y, z axes, e Ncx , e Ncy , e Ncz are components of the unit normal vector at the point M in the x, y, z axes, X c , Y c , Z c are coordinates of the point M.

[0027] Further, the twist drill is a straight line main cutting edge cone rear clearance face twist drill, and the first grinding curve is:

[0028] Wherein,

[0029] is the projection angle between the cone axis and the rotation axis, β is the rotation angle for the straight line cutting edge to coincide with the cone generatrix, d is the distance from the drill tip to the cone top in the Z direction in the cone coordinate system, θ is the half cone angle, S is the distance between the drill axis and the cone axis in the Y direction in the cone coordinate system, and t is the angle parameter of the rotation point of the outer edge of the straight line main cutting edge of the drill bit.

[0030] The second aspect of the present application provides a twist drill in-machine regrinding device, comprising:

[0031] A processor;

[0032] A memory for storing executable instructions of the processor;

[0033] Wherein, the processor is configured to load and execute the executable instructions to realize the steps of the method provided in the first aspect of the present application.

[0034] Through the above technical solution, the twist drill can be polished in the gap of drilling processing without disassembling the twist drill, so that the problems of low tool consistency and large tool mounting error caused by frequent tool mounting and dismounting can be avoided. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments description. Obviously, the drawings described in the following embodiments are some embodiments of the present application, and all other drawings obtained by those skilled in the art without creative effort based on these drawings should fall into the protection scope of the present application.

[0036] Figure 1 is the flow chart of the in-process regrinding of the flower diamond of the present application;

[0037] Figure 2 is the structural schematic diagram of the five-axis machine tool applicable to the present application;

[0038] Figure 3 is the mathematical model of the cone flank surface of the twist drill;

[0039] Figure 4 is the schematic diagram of the regrinding curve obtained by the intersection of the cone surface and the straight cylindrical surface;

[0040] Figure 5 is the definition schematic diagram of the drill bit structure coordinate system and the workpiece coordinate system;

[0041] Figure 6 is the topological structure diagram of the BC double-rotary-table five-axis machine tool. DETAILED DESCRIPTION

[0042] In order to make the objects, technical solutions and advantages of the present disclosure more obvious, the following will describe the example embodiments according to the present disclosure in detail with reference to the drawings. Obviously, the described embodiments are only some of the embodiments of the present disclosure, not all the embodiments of the present disclosure, and it should be understood that the present disclosure is not limited to the example embodiments described here. Based on the embodiments described in the present disclosure, all other embodiments obtained by those skilled in the art without creative effort should fall within the protection scope of the present disclosure.

[0043] With reference to Figure 1 , the first aspect of the present application provides a twist drill in-process regrinding method, the drill bit is fixed at the tool end of the five-axis machine tool, the tool end is fixed with the spindle of the five-axis machine tool, the workbench of the five-axis machine tool is fixed with a polishing device, the polishing device includes a grinding wheel with a rotation axis parallel to the spindle, and the method comprises the following steps:

[0044] Step S11, in the drill bit coordinate system, the coordinates and vector parameters of any point on the first regrinding curve of the drill bit are determined, the vector parameters include normal vector, tangent vector and cone generatrix vector, and the drill bit coordinate system is used to calibrate the displacement amount of the drill bit relative to the grinding wheel;

[0045] Step S12, the first regrinding curve is converted to the workpiece coordinate system to obtain the second regrinding curve in the workpiece coordinate system, wherein the workpiece coordinate system is used to calibrate the displacement amount of the workbench relative to the tool end;

[0046] Step S13, control the rotation of the grinding wheel, and control the five-axis machine tool to work according to the second sharpening curve, so as to sharpen the drill bit through the grinding wheel.

[0047] In this way, the twist drill can be polished in the gap of drilling processing without disassembling the twist drill, so that the problems of low consistency of the tool and large error of tool disassembly caused by frequent tool disassembly can be avoided. Meanwhile, the five-axis machine tool is controlled to work according to the second sharpening curve, for example, the workbench and the spindle of the five-axis machine tool are controlled to move, so as to sharpen the drill bit according to the second sharpening curve.

[0048] The inventor of the present application finds that in the related art, after the grinding wheel is sharpened for a period of time, the grinding wheel is worn out, and the outer diameter of the grinding wheel becomes smaller. In order to avoid the precision of the grinding wheel from being reduced, the wear of the grinding wheel needs to be considered, which greatly increases the difficulty of sharpening calculation.

[0049] In order to solve the above technical problems, in the method of the present application, before the step of controlling the five-axis machine tool to work according to the second sharpening curve, so as to sharpen the drill bit through the grinding wheel, the method further comprises:

[0050] controlling the movement of the workbench until the straight cutting edge of the drill bit is in parallel abutment with the outer periphery of the grinding wheel;

[0051] controlling the movement of the workbench according to the second sharpening curve, so as to sharpen the drill bit through the grinding wheel, comprising: taking the position where the straight cutting edge of the drill bit is in parallel abutment with the outer periphery of the grinding wheel as the origin of the workpiece coordinate system; controlling the workbench to move from the origin of the workpiece coordinate system according to the second sharpening curve.

[0052] It can be understood that when the straight cutting edge of the drill bit is in parallel abutment with the outer periphery of the grinding wheel, the straight cutting edge of the drill bit coincides with the grinding wheel generatrix at this time. In this way, the straight cutting edge of the drill bit is in parallel abutment with the outer periphery of the grinding wheel before each sharpening, which can eliminate the processing error caused by the wear of the outer periphery of the grinding wheel, can perform dynamic calibration before processing, greatly simplifies the calculation method of sharpening, and is convenient for improving the processing efficiency.

[0053] Further, before the step of controlling the movement of the workbench until the straight cutting edge of the drill bit is in parallel abutment with the outer periphery of the grinding wheel, the method further comprises: determining the included angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system; controlling the rotation of the spindle of the five-axis machine tool according to the included angle, so as to make the drill bit coordinate system coincide with the three-axis direction of the workpiece coordinate system.

[0054] In the present scheme, the position of the spindle of the five-axis machine tool in the circumferential direction can be calibrated according to the included angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system, so as to make the drill bit coordinate system coincide with the three-axis direction of the workpiece coordinate system, so as to facilitate coordinate transformation.

[0055] Further, the workbench is provided with an image acquisition device (for example, an industrial camera can be used), and the angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system is determined, including: acquiring a picture of the straight cutting edge of the drill bit through the image acquisition device; and determining the angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system according to the picture.

[0056] In the scheme, the angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system is determined according to the picture. For example, the picture can be denoised and enhanced, the edge of the straight cutting edge is recognized through an algorithm, and the angle between the edge and the x-axis of the workpiece coordinate system in the picture is calculated to determine the angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system.

[0057] Further, the method further includes: after machining the flank face on one side of the drill bit, rotating the spindle of the five-axis machine tool by 180 degrees, and repeatedly executing the step of controlling the rotation of the grinding wheel and the movement of the workbench of the five-axis machine tool according to the second sharpening curve to sharpen the drill bit through the grinding wheel under the condition that the drill bit is fixed.

[0058] Further, the first sharpening curve is converted to the workpiece coordinate system to obtain a second sharpening curve in the workpiece coordinate system, including:

[0059] The second sharpening curve is obtained according to the first sharpening curve and a conversion relationship matrix T, wherein the conversion relationship matrix T is:

[0060]

[0061] wherein e Scx , e Scy , and e Scz are components of a unit cone generatrix vector at the point M on the x, y, and z axes, respectively, e Vcx , e Vcy , and e Vcz are components of a unit tangent vector at the point M on the x, y, and z axes, respectively, e Ncx , e Ncy , and e Ncz are components of a unit normal vector at the point M on the x, y, and z axes, respectively, and X c , Y c , and Z c are position coordinates of the point M. Specific embodiments

[0063] In one specific embodiment of the present application, referring to Figures 2 to 6 , step 1: a BC rotary table five-axis numerical control machining center is used, as shown in Figure 2 , X, Y, and Z are coordinate axes, and B and C are rotary axes. A fixed parallel grinding wheel is installed on the worktable of the five-axis machine tool. When machining the flank face, the five-axis machine tool will process in a linked manner, and the grinding wheel is driven to rotate by an external drive.

[0064] Step 2: Mathematical model of the tapered flank face as follows Figure 3 As shown, the flank face F1 is composed of a portion of a conical surface, O * -X * Y * Z * The coordinate system is a conical surface coordinate system. O1-X1Y1Z1 is the transition coordinate system 1, and O2-X2Y2Z2 is the transition coordinate system 2. O-XYZ is the drill bit structure coordinate system, with the origin O located at the center of the drill tip. The Z-axis coincides with the drill bit axis, and the X-axis direction satisfies the condition that the Y-coordinate at the outer edge turning point M is Y. c = -r0 (2r0 is the core thickness). Conical coordinate system Y * Translation S, Z * Translate by d to transition coordinate system 1. Rotate transition coordinate system 1 around the Y1 axis. An angle is used to obtain transition coordinate system 2. Transition coordinate system 2 is then rotated by an angle β around the Z-axis to obtain the drill bit structure coordinate system. Here, S represents the Y-axis of the drill bit axis and the cone axis in the cone surface coordinate system. * The distance in the direction, d, is the distance from the drill tip to the cone apex in the Z-axis coordinate system. * Distance in direction, β is the angle between the projected axis of the cone and the axis of the drill bit, and β is the rotation angle that makes the straight cutting edge coincide with the generatrix of the cone.

[0065] Step 3: The equation F1 of the conical rake face on the drill bit structural coordinate system O-XYZ is:

[0066]

[0067] in, The general form after expansion is:

[0068] A1X 2 +A2Y 2 +A3Z 2 +A4XY+A5YZ+A6ZX+A7X+A8Y+A9Z=0

[0069] in,

[0070] Step 4: As Figure 4 As shown, the sharpening curve is the intersection of the conical surface and the right cylindrical surface passing through the turning point M of the drill bit's straight cutting edge. Let the angular parameter at the turning point M of the drill bit's straight cutting edge be t, and the drill bit radius be R. Then, the equation L of the sharpening curve in the drill bit's structural coordinate system is:

[0071]

[0072] Step 5: According to the whetting curve equation, the normal vector (N), tangent vector (V) and cone generatrix vector (S) of any point D on the whetting curve are obtained. Where, the tangent vector (V) is obtained by derivation of the whetting curve. The cone apex O * The vector connected with D is the generatrix vector (S). The normal vector N = S x V.

[0073]

[0074] N = S x V

[0075] The three vectors are respectively unitized to obtain the unit tangent vector e V , unit cone generatrix vector e S and unit normal vector e N .

[0076] Step 6: As shown in Figure 5 , the workpiece coordinate system origin is defined as the drill straight blade outer edge turning point M, the Z c axis is coincident with the cone generatrix at the M point, the Y c axis is coincident with the cylinder normal vector at the M point, and the X c axis is coincident with the cone tangent vector at the M point. In order to realize the whetting, the whetting trajectory L g of the grinding wheel and the vector F g of the grinding wheel axis in the workpiece coordinate system are needed. The conversion matrix T of the drill structure coordinate system and the workpiece coordinate system is:

[0077]

[0078] Wherein, e Scx , e Scy , e Scz are the components of the unit cone generatrix vector at the M point in the x, y, z axes, e Vcx , e Vcy , e Vcz are the components of the unit tangent vector at the M point in the x, y, z axes, e Ncx , e Ncy , e Ncz are the components of the unit normal vector at the M point in the x, y, z axes, and X c , Y c , Z c are the coordinates of the M point position.

[0079] The converted whetting trajectory L g of the grinding wheel = TL, and the vector F g of the grinding wheel axis = Te S .

[0080] Step 7: According to Figure 6A five-axis machine tool topology diagram, a rotation angle calculation formula and a coordinate conversion formula of a five-axis machine tool post-processing are derived.

[0081]

[0082] Suppose ideal tool position data is P i =[X, Y, Z] T , tool axis data is Q i =[I, J, K] T , and the ideal tool position data can be represented as:

[0083]

[0084] Step 8: Convert the post-processed data into NC code that can be recognized by the five-axis machine tool for processing. Before processing, the straight blade of the twist drill should be made to coincide with the parallel grinding wheel outer cylindrical generatrix, and during processing, the spindle does not rotate.

[0085] Step 9: After processing one side of the flank face, rotate the five-axis machine tool spindle by 180 degrees to process the other side.

[0086] The application also provides a twist drill in-machine regrinding device, comprising: a processor; a memory for storing executable instructions of the processor; wherein the processor is configured to load and execute the executable instructions to implement the steps of the method provided in the first aspect of the application.

[0087] In the present application, the terms "first", "second", "third" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance; the term "multiple" refers to two or more, unless otherwise explicitly limited. The terms "mounting", "connecting", "connecting", "fixing" and the like should be broadly understood, for example, "connecting" can be fixed connection, or detachable connection, or integral connection; "connected" can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0088] In the description of the present application, it should be understood that the terms "upper", "lower", "left", "right", "front", "back" and the like indicate the orientation or positional relationship shown in the drawings, and are only used for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or units referred to must have a particular direction, be constructed and operated in a particular orientation, therefore, it cannot be understood as a limitation on the present application.

[0089] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "a specific embodiment", and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Also, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0090] The above description is merely a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method of in-machine sharpening of a twist drill, characterized by, A drill bit is fixed on a tool end of a five-axis machine tool, the tool end is fixed with a spindle of the five-axis machine tool, and a workbench of the five-axis machine tool is fixed with a grinding device, the grinding device includes a grinding wheel with a rotation axis parallel to the spindle, and the method comprises: In a drill bit coordinate system, coordinates and vector parameters of any point on a first sharpening curve of the drill bit are determined, the vector parameters include a normal vector, a tangent vector and a cone generatrix vector, and the drill bit coordinate system is used to calibrate a displacement amount of the drill bit relative to the grinding wheel; The first sharpening curve is converted to a workpiece coordinate system to obtain a second sharpening curve in the workpiece coordinate system, wherein the workpiece coordinate system is used to calibrate a displacement amount of the workbench relative to the tool end; The grinding wheel is controlled to rotate, and the five-axis machine tool is controlled according to the second sharpening curve to sharpen the drill bit by the grinding wheel; Before the five-axis machine tool is controlled according to the second sharpening curve to sharpen the drill bit by the grinding wheel, the method further comprises: The workbench is controlled to move until a straight cutting edge of the drill bit is in parallel abutment with an outer peripheral surface of the grinding wheel; The five-axis machine tool is controlled according to the second sharpening curve to sharpen the drill bit by the grinding wheel, comprising: A position where the straight cutting edge of the drill bit is in parallel abutment with the outer peripheral surface of the grinding wheel is taken as an origin of the workpiece coordinate system; According to the second sharpening curve, the workbench of the five-axis machine tool is controlled to move from the origin of the workpiece coordinate system; The first sharpening curve is converted to a workpiece coordinate system to obtain a second sharpening curve in the workpiece coordinate system, comprising: According to the first sharpening curve and a conversion relationship matrix, the second sharpening curve is obtained, wherein the conversion relationship matrix T is: where e Scx , e Scy , e Scz are the components of the unit conical generatrix vector at point M on the x, y, z axes, respectively, e Vcx , e Vcy , e Vcz are the components of the unit tangent vector at point M on the x, y, z axes, respectively, e Ncx , e Ncy , e Ncz are the components of the unit normal vector at point M on the x, y, z axes, respectively, X c , Y c , Z c are the coordinates of the position of point M; converted grinding wheel dressing trajectory L g = TL, grinding wheel axis vector F g = Te S where e S is the unit conical generatrix vector at point M and L is the first dressing curve.

2. The method of re-sharpening a twist drill according to claim 1, wherein, Before the workbench is controlled to move until the straight cutting edge of the drill bit is in parallel abutment with the outer peripheral surface of the grinding wheel, the method further comprises: An included angle between the straight cutting edge of the drill bit and an x-axis of the workpiece coordinate system is determined; According to the included angle, the spindle of the five-axis machine tool is controlled to rotate, so that the drill bit coordinate system coincides with three-axis directions of the workpiece coordinate system.

3. The method of re-sharpening a twist drill according to claim 2, wherein, An image acquisition device is arranged on the workbench, and the included angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system is determined, comprising: A picture of the straight cutting edge of the drill bit is acquired by the image acquisition device; According to the picture, the included angle between the straight cutting edge of the drill bit and the x-axis of the workpiece coordinate system is determined.

4. The method of re-sharpening a twist drill according to claim 1, wherein, The method further comprises: After machining a flank face on one side of the drill bit, the spindle of the five-axis machine tool is rotated by 180 degrees, and the step of controlling the grinding wheel to rotate and controlling the workbench of the five-axis machine tool to move according to the second sharpening curve to sharpen the drill bit by the grinding wheel is repeatedly executed under the condition that the drill bit is fixed.

5. The method of re-sharpening a twist drill according to claim 1, wherein, The twist drill is a straight main cutting edge cone flank face twist drill, and the first sharpening curve is: wherein, is the projection angle between the cone axis and the rotation axis, β is the rotation angle for the straight cutting edge to coincide with the cone generatrix, d is the distance from the drill tip to the Z direction of the cone top in the cone coordinate system, θ is the half cone angle, S is the distance between the drill axis and the cone axis in the Y direction of the cone coordinate system, and t is the angle parameter at the outer turning point of the straight main cutting edge of the drill bit.

6. A machine re-sharpening device for twist drills, characterized in that, Comprise: a processor; a memory for storing executable instructions of the processor; The processor is configured to load and execute the executable instructions to implement the steps of the method of any one of claims 1 to 5.

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