Method for machining hob end face

Abstract

The present invention relates to the field of tool processing and discloses a method for machining hob end faces. This method utilizes the wall of one side of the hob's inner bore to grind the front and rear end faces of a carbide hob. This method provides a relatively simple and accurate detection method. After two clamping and grinding passes, the front and rear hob end faces are symmetrical about the perpendicular plane of the inner bore axis. By measuring the angle between the front and rear hob end faces, half of this angle represents the effect of the shaft's bending deformation on the hob end faces.

Description

Technical Field

[0001] The invention relates to the field of tool processing, and in particular to a method for processing a hob end face. Background Art

[0002] Hobs are gear cutting tools with teeth arranged in a spiral pattern along a cylinder or cone. The quality of the hob end face machining is a crucial quality parameter. Patented invention No. 2017106991656, "Ultra-precision Carbide Small-Modulus Hob and Its Manufacturing Process," describes a method for grinding the hob end face using a precision CNC cylindrical grinder. This invention improves the rigidity of the process system and the precision of the hob spindle and center mounting on a CNC cylindrical grinder. The preferred method involves mounting the hob on a 1:20,000 taper spindle or hydraulic spindle, and grinding the hob's outer diameter and end face on a precision CNC cylindrical grinder. This method achieves geometric and positional tolerances of 0.002mm end runout and 0.003mm diameter runout on the end face of the spindle. However, the technology of this invention has the following problems: 1. The production cost of 1:20000 tapered mandrel or hydraulic mandrel is high and the scrap rate is high; 2. The mandrel is easily worn by assembling the tapered mandrel and the carbide inner hole, and it is difficult to ensure the accuracy and quality of the product after wear; 3. The matching position of the tapered mandrel and the carbide inner hole on the tapered mandrel will change when the force is different. On the one hand, it is difficult to ensure the quality of the product when the grinding force is too large. On the other hand, the matching position of the tapered mandrel is more prone to wear and abrasion when a large force is applied; 4. The grinding process of the CNC external cylindrical grinder puts forward higher shape and parameter requirements on the end face and circumference of the grinding wheel, which leads to increased costs in the grinding process. Summary of the Invention

[0003] The present invention aims to provide a method for machining a hob end face, so as to solve the problems in the prior art of machining a hob end face using a tapered mandrel assembly, which results in difficulty in ensuring machining quality and easy wear of the mandrel.

[0004] To achieve the above object, the present invention adopts the following technical solution: a method for machining a hob end face, comprising the following steps:

[0005] A. Clamp the hob cutter blank on a fixture. Use the fixture to apply four coplanar support points to the wall of the inner hole of the hob cutter blank. Apply pressure between the four support points to the outer circle of the hob cutter blank, so that the hob cutter blank and the fixture as a whole are tilted at an angle α along the pressure direction in a plane passing through the support points and formed by the pressure direction and the axis direction of the hob inner hole.

[0006] B. Use a grinding tool to grind the end face of the hob blank, control the grinding tool path in the hob blank workpiece coordinate system, and make the normal direction of the grinding end face form an angle α1 with the axis of the inner hole of the hob blank;

[0007] C. Remove the hob blank from the fixture and clamp it in reverse, ensuring that the hob blank rotates 180° around the center of the four support points;

[0008] D. Grind the other end face of the hob blank with a grinding tool. Control the grinding tool to use the same grinding path as in step B. The normal direction of the ground end face forms an angle α2 with the axis of the inner hole of the hob blank. From steps A, B, and C, it can be seen that α2=α1.

[0009] E. Detect the angle between the two end faces of the hob blank as 2α'. From steps A, B, C, and D, we know that 2α'=α2+α1. If 2α' meets the hob end face requirements, the end face is qualified. If 2α' does not meet the hob end face requirements, return to steps B and D, control and adjust the grinding tool path in the hob blank workpiece coordinate system, so that the angles α1' and α2' formed by the end face normal obtained after adjustment and the hob blank inner hole axis meet the hob end face requirements.

[0010] Alternatively, the actual angles α1' and α2' between the front and rear end faces after grinding in step B and step D and the inner hole axis can be separately detected. If α1' and α2' meet the hob end face requirements, the end face is qualified. If α1' and α2' do not meet the hob end face requirements, return to step B and step D, control and adjust the grinding tool path of the grinding tool in the hob blank workpiece coordinate system, so that the angles α1' and α2' between the end face normal obtained after adjustment and the hob blank inner hole axis meet the hob end face requirements.

[0011] Preferably, as an improvement, the fixture used in step A includes a shaft, a sleeve and a pressure plate, the front end of the shaft is a support part, and the rear end is a standard straight handle, two support rings are provided side by side on the support part, each support ring has at least two support points, the sleeve is fixed on the standard straight handle, the pressure plate is U-shaped, the middle part of the pressure plate is connected to the sleeve, one end of the pressure plate is against the sleeve, and the other end is located between the two support rings, in step A, the hob blank is sleeved on the support part, and four coplanar support points are provided for the inner hole of the hob blank through the two support rings, and pressure is applied to the outer circle of the hob blank between the two support rings through the pressure plate.

[0012] Preferably, as an improvement, the support ring is a square raised bar with an axially symmetrical structure, the cross-sectional shape of the support ring is a rectangle consisting of a group of parallel straight edges above and below and a group of parallel straight edges left and right, and the adjacent straight edges of the support ring are connected by two sections of circular arc transitions of unequal diameters. In step A, support is provided to the inner hole of the hob blank only through the circular arc transition connection between the adjacent straight edges of the support ring.

[0013] Preferably, as an improvement, a gap plane parallel to the straight edge of the support ring is provided on the support portion between the support rings, and a gap arc surface is provided between adjacent gap planes. A positioning plane parallel to the gap plane is processed on the standard straight shank, and three sleeve planes and a clamping plane parallel to the positioning plane are processed on the outer wall of the sleeve. In step A, the pressure plate is positioned by the clamping plane, and the sleeve plane is aligned with the normal of the gap plane to control the radial force applied along the hob blank after the pressure plate is clamped.

[0014] Preferably, as an improvement, the support portion is provided with a front cylindrical surface and a rear cylindrical surface located outside the support ring. In step A, the fixture is clamped on the machine tool handle, and the position deviation of the fixture on the machine tool handle is checked by the front cylindrical surface, the rear cylindrical surface and the positioning plane.

[0015] Preferably, as an improvement, a threaded hole and a guide groove along the axial direction of the sleeve are processed on the clamping plane, a guide block is provided at one end of the pressure plate that abuts against the sleeve, the guide block is inserted into the guide groove, a through hole is opened in the middle of the pressure plate, and a bolt connected to the threaded hole is passed through the through hole.

[0016] Preferably, as an improvement, one end of the pressure plate located between the two support rings is a pressure plate top block, and in step A, the pressure plate top block is controlled to be located between the two support rings by adjusting the relative distance between the sleeve end face and the shaft end face.

[0017] The principles and advantages of this solution are as follows: In actual application, the front and rear end faces of the carbide hob are ground by repeatedly utilizing the wall of one side of the hob's inner bore. To ensure stability during end face grinding, the hob's inner bore must be a straight hole that complies with the JB / T 7654-2006 standard. The inner bore axis is supported and positioned by two sets of front and rear support rings on a shaft, with each set of support rings having two support points along the circumference of the inner bore. Pressure is applied to the hob's outer diameter on the side of the support point to ensure the hob's stable installation on the shaft support point. Viewed from the direction of the applied pressure, the applied pressure is within the plane formed by the four support points. The applied pressure inevitably causes the shaft to bend and deform. Within a certain range, the deformation and the applied force satisfy the deflection curve equation. During implementation, as long as the applied force remains constant, repeatable bending deformation can be achieved. For shafts that are bent and deformed due to applied pressure, a grinding wheel is used to grind the end face of the hob blank on it along a specific motion path. The positional relationship between the end face and the inner hole axis is obtained by combining the bending deformation of the shaft and the grinding wheel motion path. The pressure is then unloaded, the hob blank is rotated 180°, and reinstalled on the shaft to ensure the circumferential and axial consistency of the contact positions between the two sets of support points and the original hob inner hole wall. The same pressure is applied to clamp the hob, and the original grinding motion path of the grinding wheel is repeated to grind the other end face of the hob. The effect of the bending deformation of the shaft on the hob end face is detected and compensated in the grinding wheel motion path. The above clamping and grinding process is repeated to obtain a hob end face perpendicular to the hob inner hole axis. Conventional end face detection equipment can be used to individually detect the deviation of each hob end face relative to the inner hole axis, thereby calculating the bending deformation of the shaft. This method also provides a relatively simple and accurate detection method. Due to the two clamping and grinding steps, the front and rear hob end faces are symmetrical about the perpendicular plane of the inner bore axis. By measuring the angle between the front and rear hob end faces, half of this angle represents the effect of the shaft's bending deformation on the hob end faces. The fixture used in this method requires a hard surface that is not susceptible to plastic deformation and is easy to manufacture, such as using a carbide standard rod.

[0018] The advantages of the present invention are:

[0019] 1. The shaft fixture of this solution contacts the inner hole of the hob through the support points of the front and rear sets of support rings, exerting reliable pressure in a certain direction. By calculating and controlling the grinding position of the grinding wheel, the control accuracy is high, and the machined hob end face has higher accuracy and better repeatability.

[0020] 2. Since only the contact between the support point and the inner hole of the hob and the repeatability of the pressure applied in a certain direction need to be considered, the shaft tolerance requirement is low and the manufacturing cost is low.

[0021] 3. The shaft rod clamp of this solution can be made of hard alloy material, the manufacturing process is simple, and the shaft rod clamp has little wear.

[0022] 4. The calculation process and data processing and analysis can be integrated into the software program, reducing the complexity of the manufacturing process, alleviating the labor intensity of the operator, and making the operation simpler and easier to get started. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is an oblique view of the shaft rod in Example 1 of the present invention.

[0024] Figure 2 These are the front view and right view of the shaft rod in Example 1 of the present invention.

[0025] Figure 3 This is a front view of the sleeve in Example 1 of the present invention.

[0026] Figure 4 This is a top view of the sleeve in Example 1 of the present invention.

[0027] Figure 5 These are the front view and left view of the pressure plate in Example 1 of the present invention.

[0028] Figure 6 This is an oblique view of the clamp in Example 1 of the present invention.

[0029] Figure 7 This is a side view of the hob blank clamped on the fixture in Example 2 of the present invention.

[0030] Figure 8 This is an oblique view of the hob blank clamped on the fixture in Example 2 of the present invention. DETAILED DESCRIPTION

[0031] The following is further described in detail through specific implementation methods:

[0032] The figure marks in the drawings of the specification include: shaft 1, sleeve 2, pressure plate 3, support part 4, front support ring 5, rear support ring 5', vertical gap plane 6, transverse gap plane 6', gap arc surface 7, front cylindrical surface 8, rear cylindrical surface 8', shaft end face 9, sleeve end face 10, connecting threaded hole 11, guide groove 12, clamping threaded hole 13, guide block 14, through hole 15, pressure block plane 16, pressure plate top block 17, standard straight shank 18, clamping bolt 19, hob blank 20, positioning plane 21, sleeve plane 22, clamping plane 23.

[0033] Example 1, basically as in the attached Figure 6 As shown: A fixture for machining the end face of a hob, comprising a shaft 1, a sleeve 2 and a pressure plate 3, as shown Figure 1 、 Figure 2As shown, the rear end of the shaft 1 is a standard cylindrical straight shank 18, and the front end of the shaft 1 is a support portion 4 with a smaller diameter than the standard straight shank 18. The support portion 4 is machined with a front support ring 5 and a rear support ring 5', both of which are square raised bars. The cross-section of the support rings is a rectangle consisting of a set of parallel straight edges, one set of parallel straight edges, and a set of parallel straight edges, each with two arcs of unequal diameters connecting the adjacent straight edges. The surface of the shaft 1 between the front support ring 5 and the rear support ring 5' is defined by a vertical clearance plane 6, a transverse clearance plane 6', and a clearance arc surface 7 parallel to the support ring arc transition edges. A front cylindrical surface 8 is machined on the support portion 4 in front of the front support ring 5, and a rear cylindrical surface 8' is machined on the support portion 4 behind the rear support ring 5'. Four positioning flats 21 are machined on the standard straight shank 18, parallel to the vertical clearance plane 6 and the transverse clearance plane 6'.

[0034] like Figure 3 、 Figure 4 As shown, the sleeve 2 is cylindrical, and the outer wall of the sleeve 2 is processed with three sleeve planes 22 parallel to the vertical gap plane 6 and the horizontal gap plane 6', and a clamping plane 23 parallel to the vertical gap plane 6. Each sleeve plane 22 is provided with a connecting threaded hole 11, and the clamping plane 23 is provided with a guide groove 12 and a clamping threaded hole 13 side by side. Figure 5 As shown, the pressure plate 3 is U-shaped, the middle part of the pressure plate 3 is a pressure block plane 16, a through hole 15 is opened in the middle of the pressure block plane 16, the front end of the pressure plate 3 is a pressure plate top block 17, the rear end of the pressure plate 3 is a guide block 14, and a bolt connected to the tightening threaded hole 13 on the tightening plane 23 is passed through the through hole 15, and the guide block 14 is inserted into the guide groove 12.

[0035] Example 2, a method for machining a hob end face, the specific implementation process is as follows:

[0036] A. Clamp the standard straight handle 18 of the shaft rod 1 in Example 1 onto the tool holder of the machine tool, as shown in FIG. Figure 7 、 Figure 8As shown, the position deviation on the machine tool handle is checked by the front cylindrical surface 8 and the rear cylindrical surface 8', the sleeve 2 is put on the standard straight handle 18, the sleeve 2 is connected to the shaft 1 through the connecting bolt in the connecting threaded hole 11, and the clamping bolt 19 connected to the clamping threaded hole 13 is passed through the through hole 15 to connect the pressure plate 3 to the sleeve 2. By aligning the sleeve plane 22 with the vertical gap plane 6 and the horizontal gap plane 6' in the normal direction, the clamping plane 23 is aligned with the vertical gap plane 6 in the normal direction, and the force direction of the hob blank 20 after the pressure plate 3 is clamped can be controlled; the hob blank 20 is put on the support part 4, and the pressure plate 3 is fixed to the support part 4. The front support ring 5 and the rear support ring 5' provide four coplanar support points for the inner hole of the hob blank 20 to ensure the accuracy of the inner hole of the fixture and the hob blank 20. It can be ensured that there are only four support points. By adjusting the relative position of the sleeve end face 10 and the shaft end face 9, the pressure plate top block 17 is located between the front support ring 5 and the rear support ring 5', and the tightening bolt 19 is tightened with a torque wrench, so that the pressure plate top block 17 applies a pressure to the hob blank 20, so that the hob blank 20 and the fixture as a whole are inclined at an angle α along the pressure direction in a plane passing through the support points and formed by the pressure direction and the axis direction of the inner hole of the hob blank 20;

[0037] B. Grind the end face of the hob cutter blank 20 clamped on the fixture with a grinding wheel, control the grinding path of the grinding wheel in the workpiece coordinate system of the hob cutter blank 20, and make the normal direction of the ground end face form an angle α1 with the axis of the inner hole of the hob cutter blank 20;

[0038] C. Remove the hob blank 20 from the fixture and clamp it in reverse, ensuring that the hob blank 20 is rotated 180° around the center of the four support points;

[0039] D. Grind the other end face of the hob cutter blank 20 with a grinding wheel. Control the grinding wheel to use the same grinding path as in step B. The normal direction of the ground end face forms an angle α2 with the axis of the inner hole of the hob cutter blank 20. From steps A, B, and C, it can be seen that α2=α1.

[0040] E. Detect the angle between the two end faces of the hob cutter blank 20 as 2α'. From steps A, B, C, and D, we know that 2α'=α2+α1. If 2α' meets the hob end face requirements, the end face is qualified. If 2α' does not meet the hob end face requirements, return to steps B and D, control and adjust the grinding tool path of the grinding tool in the hob cutter blank workpiece coordinate system, so that the angles α1' and α2' formed by the end face normal obtained after adjustment and the hob cutter blank inner hole axis meet the hob end face requirements.

[0041] Alternatively, the actual angles α1' and α2' between the front and rear end faces ground in steps B and D and the inner hole axis can be separately detected. If α1' and α2' meet the hob end face requirements, the end face is qualified. If α1' and α2' do not meet the hob end face requirements, the process returns to steps B and D, controls and adjusts the grinding tool path in the hob blank workpiece coordinate system, and makes the angles α1' and α2' between the end face normal obtained after adjustment and the hob blank inner hole axis meet the hob end face requirements. In this embodiment, meeting the hob end face requirements means that the detected angles meet the end face runout requirements of the corresponding grade after conversion. For example, an AAA-grade hob meets an end face runout of 0.002mm, and an AA-grade hob meets an end face runout of 0.003mm. The conversion process is a conventional technical means known in the art and will not be described in detail here.

[0042] The present invention realizes the grinding of the front and rear end faces of the carbide hob by repeatedly utilizing the hole wall of one side of the inner hole of the hob blank 20. In order to ensure stability when grinding the end face, the inner hole of the hob is required to be a straight hole that complies with the JB / T 7654-2006 standard. The axis of the inner hole is supported and positioned by two sets of front and rear support rings on a shaft 1. Each set of support rings has two support points along the circumferential direction of the inner hole. Pressure is applied to the outer circle of the hob on the side where the support point is located to ensure that the hob is stably installed on the support point of the shaft 1. From the direction of the applied pressure, the applied pressure is within the plane area formed by the four support points. The applied pressure will inevitably cause the shaft 1 to bend and deform. Within a certain range, the deformation and the applied force satisfy the deflection curve equation. During implementation, as long as the applied force is kept constant, repeated bending deformation can be obtained. For shafts 1 that have been bent and deformed due to applied pressure, a grinding wheel is used to grind the end face of the hob blank 20 attached to it along a specific motion path. The positional relationship between the end face and the inner bore axis is determined by the combined effects of the shaft 1's bending deformation and the grinding wheel's motion path. The pressure is then removed, the hob blank 20 is rotated 180°, and reinstalled on the shaft 1, ensuring that the two sets of support points and the original contact points with the hob's inner bore wall are consistent in both the circumferential and axial directions. The same pressure is applied to the hob, and the original grinding wheel path is repeated to grind the other end face of the hob. The effect of the shaft 1's bending deformation on the hob end face is detected and compensated for in the grinding wheel's motion path. Repeating the above clamping and grinding process results in a hob end face that is perpendicular to the hob's inner bore axis. Conventional end face inspection equipment can be used to individually measure the deviation of each hob end face relative to the inner bore axis, thereby calculating the shaft 1's bending deformation α. By compensating for α during the grinding path, a set of hob end faces that are both perpendicular to the hob's inner bore axis and parallel to each other are obtained. This method also provides a relatively simple and accurate detection method. After two clamping and grinding cycles, the front and rear hob end faces are symmetrical about the perpendicular plane of the inner hole axis. By detecting the angle between the front and rear hob end faces, half of which is the effect of the bending deformation of the shaft 1 on the hob end faces, the angle between the two planes is measured by the detection tool as 2α. By compensating α during the grinding process, a set of hob end faces that are both perpendicular to the hob inner hole axis and parallel to each other can be obtained. The fixture used in this method requires a hard surface that is not susceptible to plastic deformation and is easy to manufacture, such as using a carbide standard rod.

[0043] The above is only an embodiment of the present invention, and the common knowledge such as the specific technical solutions and / or characteristics in the solution are not described in detail here. It should be pointed out that for those skilled in the art, without departing from the technical solution of the present invention, several variations and improvements can be made, which should also be regarded as the scope of protection of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the description can be used to interpret the content of the claims.

Claims

1. A method for machining a hob end face, characterized in that: The following steps are involved: A. Clamp the hob cutter blank on a fixture. Use the fixture to apply four coplanar support points to the wall of one side of the inner hole of the hob cutter blank. Apply a pressure between the four support points to the outer circle of the hob cutter blank, so that the hob cutter blank and the fixture as a whole are inclined at an angle α along the pressure direction in a plane passing through the support points and formed by the pressure direction and the axis direction of the inner hole of the hob cutter blank. The clamp used in step A includes a shaft rod, a sleeve and a pressure plate, the front end of the shaft rod is a support part, and the rear end is a standard straight handle, two support rings are arranged side by side on the support part, each support ring has at least two support points, the sleeve is sleeved and fixed on the standard straight handle, the pressure plate is U-shaped, the middle of the pressure plate is connected to the sleeve, one end of the pressure plate is against the sleeve, and the other end is located between the two support rings. In step A, the hob blank is sleeved on the support part, and four coplanar support points are provided for the inner hole of the hob blank through the two support rings, and pressure is applied to the outer circle of the hob blank between the two support rings through the pressure plate; the support ring is a square raised bar with an axially symmetrical structure, and the cross-sectional shape of the support ring is a rectangle composed of a group of parallel straight edges above and below and a group of parallel straight edges left and right, and the adjacent straight edges of the support ring are connected by two sections of unequal diameter arc transitions. In step A, support is provided to the inner hole of the hob blank only through the arc transition connection between the adjacent straight edges of the support ring; B. Use a grinding tool to grind the end face of the hob blank, control the grinding tool path in the hob blank workpiece coordinate system, and make the normal direction of the grinding end face form an angle α1 with the axis of the inner hole of the hob blank; C. Remove the hob blank from the fixture and clamp it in reverse, ensuring that the hob blank rotates 180° around the center of the four support points; D. Grind the other end face of the hob blank with a grinding tool. Control the grinding tool to use the same grinding path as in step B. The normal direction of the ground end face forms an angle α2 with the axis of the inner hole of the hob blank. From steps A, B, and C, it can be seen that α2=α1. E. Detect the angle between the two end faces of the hob blank as 2α'. From steps A, B, C, and D, we know that 2α'=α2+α1. If 2α' meets the hob end face requirement, the end face is qualified. If 2α' does not meet the hob end face requirement, return to steps B and D, control and adjust the grinding tool path of the grinding tool in the hob blank workpiece coordinate system, so that the angles α1' and α2' formed by the end face normal obtained after adjustment and the hob blank inner hole axis meet the hob end face requirement; or, The actual angles α1' and α2' between the front and rear end faces after grinding in step B and step D and the inner hole axis are detected separately. If α1' and α2' meet the requirements of the hob end face, the end face is qualified. If α1' and α2' do not meet the requirements of the hob end face, return to step B and step D, control and adjust the grinding tool path of the grinding tool in the hob blank workpiece coordinate system, so that the angles α1' and α2' between the end face normal obtained after adjustment and the inner hole axis of the hob blank meet the requirements of the hob end face.

2. A method for machining a hob end face according to claim 1, characterized in that: A gap plane parallel to the straight edge of the support ring is provided on the support portion between the support rings, and a gap arc surface is provided between adjacent gap planes. A positioning plane parallel to the gap plane is processed on the standard straight shank, and three sleeve planes and a clamping plane parallel to the positioning plane are processed on the outer wall of the sleeve. In step A, the pressure plate is positioned by the clamping plane, and the sleeve plane is aligned with the normal of the gap plane to control the radial force applied along the hob blank after the pressure plate is clamped.

3. The method for machining a hob end face according to claim 2, characterized in that: The support portion is provided with a front cylindrical surface and a rear cylindrical surface located outside the support ring. In step A, the fixture is clamped on the machine tool handle, and the position deviation of the fixture on the machine tool handle is checked through the front cylindrical surface, the rear cylindrical surface and the positioning plane.

4. The method for machining a hob end face according to claim 3, characterized in that: A threaded hole and a guide groove along the axial direction of the sleeve are processed on the clamping plane. A guide block is provided at one end of the pressure plate that abuts against the sleeve. The guide block is inserted into the guide groove. A through hole is opened in the middle of the pressure plate, and a bolt connected to the threaded hole is passed through the through hole.

5. The method for machining a hob end face according to claim 4, characterized in that: One end of the pressure plate located between the two support rings is a pressure plate top block. In step A, the pressure plate top block is controlled to be located between the two support rings by adjusting the relative distance between the sleeve end face and the shaft end face.

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