A milling instead of grinding method and processing tool for rectangular spline of gear part

Abstract

This invention provides a milling method and fixture for machining rectangular splines on gear parts, replacing grinding. Step 1: Complete the bevel gear machining. Step 2: Place the gear positioning fixture onto the gear part. Step 3: Install a cylindrical pin on the gear positioning fixture; ensure the cylindrical pin is tangent to the arc of the adjacent tooth groove of the bevel gear, thus securing the bevel gear and defining the position of the gear part, determining the starting position of the rectangular spline. Step 4: Level the gear positioning fixture, align the cutting tool and center it, then rotate it by a certain angle. This rotation angle corresponds to the positional relationship between the rectangular spline and the bevel gear tooth tip groove. Then, begin milling the rectangular spline. This invention ensures the positional relationship between the bevel gear tooth tip groove and the outer rectangular spline while achieving low-cost, high-precision machining of the outer rectangular spline to meet design requirements. The fixture structure is simple, the machining process is good, effectively improving the product qualification rate and controlling and reducing the machining cost of the outer rectangular spline on gear parts.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, specifically relating to a milling method and machining fixture for machining rectangular splines of gear parts instead of grinding. Background Technology

[0002] Rectangular splines are a very common design feature in shaft-type parts. Because rectangular splines offer advantages such as high centering accuracy and good centering stability, grinding is a conventional method that can meet both diameter and positional tolerances and achieve high precision.

[0003] With societal progress, rectangular spline structures have become increasingly common in the connection and fastening of various components. Our company currently has a large order for gears, with diverse varieties and short delivery times. This batch of gear parts includes many rectangular spline structures, both internal and external. Based on our existing equipment, internal spline structures can be machined using wire EDM to ensure the required precision. External spline structures are conventionally machined using a spline grinder. However, since our company lacks spline grinders, this grinding process needs to be outsourced. Outsourcing not only results in long lead times and unpredictable delivery times, but also in high costs, exceeding 1000 RMB per part for the spline grinding process alone. Furthermore, the grinding process is limited by the size of the grinding wheel; even a wheel with a minimum outer diameter of 50mm can damage the area near the outer diameter of the part, failing to meet customer requirements. In addition, this batch of parts requires a specific positional relationship between the bevel gear teeth and the external rectangular spline, but current external spline grinding processes cannot guarantee this relative positional relationship. To address the above problems, the following technical solution is proposed. Summary of the Invention

[0004] The technical problem solved by this invention is to provide a milling method and tooling for machining rectangular splines of gear parts, which solves the problem of how to ensure the positional relationship between the tooth tip groove of the bevel gear and the outer rectangular spline, while achieving low-cost, high-precision machining of the outer rectangular spline of the bevel gear to meet the design requirements.

[0005] The technical solution adopted in this invention is a method for milling rectangular splines on gear parts instead of grinding, comprising the following steps:

[0006] Step 1: Complete the bevel gear machining of the gear parts.

[0007] Step 2: Fit the tooth positioning fixture onto the optical shaft of the gear part with an interference fit to ensure that after the tooth positioning fixture is assembled, its core diameter B0 fits the optical shaft diameter A0 of the gear part without any gap; and make the front end face of the tooth positioning fixture tightly against the rear end face of the bevel tooth of the gear part.

[0008] Step 3: Install cylindrical pins in the symmetrical cylindrical pin holes on the upper and lower sides of the gear positioning fixture; make the front ends of the two cylindrical pins extend out of the gear positioning fixture, and make the extended ends of the cylindrical pins tangent to the arc of the tooth groove of the adjacent tooth of the bevel tooth, so that the cylindrical pins hold the bevel tooth and thus limit the position of the gear part, and use this position to determine the starting position of the rectangular spline of the gear part.

[0009] Step 4: Level the tooth positioning fixture, align the boring and milling forming tool and center it, then rotate the tooth positioning fixture and gear parts by a certain angle. The rotation angle is used to correspond to the positional relationship between the rectangular spline and the bevel tooth tip groove, and then start the milling of the rectangular spline.

[0010] In the above technical solution, further: step 4 is divided into two steps, rough milling and finish milling, to complete the machining of the rectangular spline; during rough milling, the minor diameter φd and key width L of the rectangular spline are guaranteed; during finish milling, the tolerance grade of the minor diameter φd is at least G7 and the tolerance grade of the key width L is at least F9.

[0011] In the above technical solution, further: the cutting edge size of the boring and milling forming tool matches the size of the rectangular spline; the tool holder of the boring and milling forming tool does not interfere with the outer circle near the rectangular spline.

[0012] In the above technical solution, further: the gear positioning fixture is a disc structure with horizontal cross-sections on the upper and lower parts and a central hole; the upper and lower center positions of the disc body are respectively provided with axially symmetrical cylindrical pin holes; the center distance B1 between the upper and lower cylindrical pin holes matches the number of teeth and module of the gear part, so as to ensure that the cylindrical pin and the adjacent tooth groove of the bevel tooth are tangent to the arc; the outer diameter B3 of the disc body matches the size of the tip circle of the bevel tooth of the gear part; the axial thickness B4 of the disc body is smaller than the axial length A2 of the optical axis boss.

[0013] This invention also claims protection for a milling fixture for machining rectangular splines of gear parts instead of grinding, wherein the machining fixture is the same as the machining fixture used in any of the claims.

[0014] Advantages of this invention compared to existing technologies:

[0015] 1. The processing method and tooling of this invention effectively ensure the position of the bevel tooth tip groove and the outer rectangular spline. The boring and milling forming tool is reasonably designed, and the tooth positioning tooling is convenient and easy to use for positioning the bevel tooth. The tooling structure is simple, the processing technology is good, and it can effectively improve the product processing qualification rate, thereby controlling and reducing the processing cost of the outer rectangular spline of the gear parts.

[0016] 2. The boring and milling forming tool of the present invention ensures the accuracy requirements of the rectangular spline of the gear part through boring and milling. Its deformation can be controlled through multiple machining processes. The machining is completed in two steps: rough milling and finish milling. The tool wear and sharpening effects are minimized, and the tool shank does not interfere with the outer circle near the rectangular spline. The structure is relatively simple, easy to implement, and the machining accuracy meets the requirements.

[0017] 3. This invention replaces spline grinding with boring and milling. Milling rectangular splines is faster, involving two steps: roughing and finishing, resulting in high machining accuracy that meets customer requirements for precision and relative positional relationships. The total time for milling a rectangular spline on one gear part is approximately 2 hours. More than 800 gear parts have already been processed. Based on the outsourced grinding cost of 1,000 yuan per piece for rectangular splines, the boring and milling method of this invention costs only about 100 yuan per piece. Milling 800 products can save the company approximately 720,000 yuan in costs.

[0018] 4. The boring and milling processing technology of this invention is stable and has good processability in the mass production of parts, making it suitable for widespread application. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the gear component structure of the present invention;

[0020] Figure 2 For invention Figure 1 Side view of the gear part;

[0021] Figure 3 This is a front view of the boring and milling forming tool of the present invention;

[0022] Figure 4 For the present invention Figure 3 Side view of a boring and milling tool;

[0023] Figure 5 This is a schematic diagram of the tooth positioning tooling structure of the present invention;

[0024] Figure 6 For the present invention Figure 5 Side view of the tooth positioning fixture;

[0025] Figure 7 This is a schematic diagram of the milled gear parts of the present invention in use.

[0026] Figure 8 For the present invention Figure 7 Side view of a milled gear part in its service state;

[0027] Figure 9 This is a flowchart of the steps of the present invention;

[0028] In the diagram: 1-Gear part, 101-Bevel tooth, 102-Optical shaft, 103-Rectangular spline, 2-Gear positioning fixture, 201-Core hole, 202-Cylindrical pin hole, 3-Cylindrical pin, 4-Milling tool. Detailed Implementation

[0029] The following will refer to the appendices in the embodiments of the present invention. Figure 1-8 The technical solutions in the embodiments of the present invention are clearly and completely described herein. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] A method for machining rectangular splines on gear parts using milling instead of grinding, it should be noted that:

[0031] This invention provides a representative gear part 1, which is a bevel gear. The positional relationship between the tooth tip and tooth groove of the bevel gear and the rectangular spline 103 is shown in the figure. Figure 1 , Figure 2 As shown.

[0032] A method for machining rectangular splines on gear parts by milling instead of grinding includes the following steps:

[0033] Step 1: Complete the machining of the bevel gear 101 of gear part 1. The reason for completing the machining of the bevel gear 101 first is that the milling of the rectangular spline 103 is performed only after the bevel gear 101 is completed. This is because the milling process must ensure the relative positional relationship between the bevel gear 101 and the rectangular spline 103, while the bevel gear 101 cannot guarantee the relative positional relationship between the bevel gear 101 and the rectangular spline 103 during the bevel gear planing process. Therefore, the machining of the bevel gear 101 must be performed first.

[0034] Step 2 (e.g.) Figure 5 , Figure 6 , Figure 7 As shown): The tooth positioning fixture 2 is fitted onto the optical shaft 102 of the gear part 1 with an interference fit to ensure that after the tooth positioning fixture 2 is assembled, the diameter B0 of the core hole 201 of the tooth positioning fixture 2 and the diameter A0 of the optical shaft 102 of the gear part 1 are fitted without gap, i.e., an interference fit; and the front end face of the tooth positioning fixture 2 is made to be in close contact with the rear end face of the bevel tooth 101 of the gear part 1, thereby positioning the assembly position of the tooth positioning fixture 2.

[0035] Step 3: Install cylindrical pins 3 into the symmetrical cylindrical pin holes 202 on the upper and lower sides of the tooth positioning fixture 2; and make the front ends of the two cylindrical pins 3 extend out of the tooth positioning fixture 2, with the extended ends of the cylindrical pins 3 respectively tangent to the arc of the tooth groove of the adjacent tooth of the bevel tooth 101, so that the cylindrical pins 3 symmetrically hook the tooth of the bevel tooth 101 on the upper and lower axes, thereby defining the position of the gear part 1, and using this position to determine the starting position of the rectangular spline 103 of the gear part 1. It should be noted that the extension length of the cylindrical pins 3 should be determined according to the size of the bevel tooth 101 and the axial dimension A2 of the optical shaft 102, and the length of the cylindrical pins 3 extending out of the end face of the fixture should not be too much.

[0036] Step 4: After leveling the gear positioning fixture 2 and aligning the boring and milling forming tool 4 with the center, rotate the gear positioning fixture 2 along with the gear part 1 by a certain angle. The rotation angle corresponds to the positional relationship between the rectangular spline 103 and the tooth tip groove of the bevel gear 101. Then, begin the milling process of the rectangular spline 103. Specifically: After rotating by a certain angle A4 and A5, start milling. The size of angles A4 and A5 needs to be calculated based on the number of teeth of the bevel gear and the number of rectangular splines. In this way, the positional relationship between the milled rectangular spline 103 and the bevel gear 101 will meet the design requirements of the drawing.

[0037] In the above embodiment, further: step 4 involves two milling steps, rough milling and finish milling, to complete the machining of the rectangular spline 103. During rough milling, the minor diameter φd and key width L of the rectangular spline 103 are guaranteed; during finish milling, the tolerance grade of the minor diameter φd is at least G7, and the tolerance grade of the key width L is at least F9.

[0038] Specifically, the precision requirements of the rectangular spline 103 in gear part 1 are ensured through boring and milling. This can be achieved by controlling deformation through multiple machining operations, specifically a rough milling followed by a finish milling process. During rough milling, the minor diameter φd and key width L are ensured before finish milling to achieve the required dimensions and positional requirements. The rectangular spline 103, after being machined in two steps (rough and finish milling), has the same shape and positional relationship as required in the attached diagram.

[0039] (like Figure 3 , Figure 4 As shown in the above embodiment, further: the cutting edge size of the boring and milling forming tool 4 matches the size of the rectangular spline 103. The tool holder of the boring and milling forming tool 4 does not interfere with the outer circle near the rectangular spline 103.

[0040] The dimensions of the other cutting edges of the boring and milling forming tool 4 are also matched with the dimensions of the rectangular spline 103 to be machined; and tool wear and cutting edge wear are also taken into consideration to the greatest extent possible, and the φ12 dimension of the tool shank is designed to avoid interference with the outer circle near the rectangular spline 103.

[0041] It also includes a tooth positioning fixture 2, which is used to ensure that the relative positional relationship between the tooth tip and tooth groove of the bevel tooth 101 and the machined rectangular spline 103 is consistent with the requirements of the attached drawing.

[0042] (like Figure 5 , Figure 6 As shown in the above embodiment, the tooth positioning fixture 2 is further described as a disc structure with horizontal cross-sections on the upper and lower parts and a central hole 201. The disc structure has upper and lower horizontal cross-sections, which are used to avoid interference between the tooth positioning fixture 2 and the gear part 1. The central hole 201 of the disc is used for concentric positioning and assembly between the tooth positioning fixture 2 and the gear part 1.

[0043] Furthermore, in the tooth positioning fixture 2, the size of the core hole B0 in the tooth positioning fixture 2 and the A0 in the gear part 1 must be designed to be an interference fit. This fit requirement serves as the positioning reference for mating with the gear part 1. The upper and lower center positions of the disc body are respectively provided with symmetrical cylindrical pin holes 202. The center distance B1 between the upper and lower cylindrical pin holes 202 matches the number of teeth and module of the gear part 1, ensuring that the cylindrical pin 3 is tangent to the arc at the tooth groove of the adjacent tooth of the bevel tooth 101. The size of the cylindrical pin hole 202 (B2) is also determined by the number of teeth and module of gear part 1. The size of the cylindrical pin hole 202 (B2) must ensure that the cylindrical pin 3 is tangent to the arc of the adjacent tooth groove of the bevel gear 101. When milling the rectangular spline 103, two cylindrical pins 3 need to be inserted here. The extension length of the front end of the cylindrical pin 3 must be able to catch the large end tooth of the bevel gear, thereby limiting the position of the bevel gear. This position is used to determine the starting position of the rectangular spline 103, so that the relative positional relationship between the rectangular spline 103 and the bevel gear 101 meets the design requirements of the drawing. The outer diameter B3 of the disc body matches the size of the tip circle of the bevel gear 101 of gear part 1. The size must take into account the position of the cylindrical pin 3, the size of the longitudinal height B5 of the disc body, and the machinability. Therefore, the outer diameter B3 of the disc body is designed to be 50mm, which is just right. The axial thickness B4 of the disc body is smaller than the axial length A2 of the optical axis 102 boss. The optimal design for B4 is 14mm.

[0044] The aforementioned tooth positioning fixture 2 can be reused, thereby improving the processing efficiency of fixture production.

[0045] The present invention also claims protection for a milling fixture for machining rectangular splines of gear parts instead of grinding, wherein the machining fixture is the machining fixture used in any of the aforementioned machining methods.

[0046] As can be seen from the above description, the processing method and tooling of the present invention effectively ensure the positions of the top groove of the bevel tooth 101 and the outer rectangular spline 103. The boring and milling forming tool 4 is reasonably designed, and the tooth positioning tooling 2 is convenient and easy to use for positioning the bevel tooth 101. The tooling structure is simple, the processing technology is good, and it can effectively improve the product processing qualification rate, thereby controlling and reducing the processing cost of the outer rectangular spline 103 of the gear part 1.

[0047] The boring and milling forming tool 4 of this invention ensures the accuracy requirements of the rectangular spline 103 of the gear part 1 through boring and milling. Its deformation can be controlled through multiple machining processes. The machining is completed in two steps: rough milling and finish milling. The tool wear and sharpening effects are minimized. The tool shank does not interfere with the outer circle near the rectangular spline. The structure is relatively simple, easy to implement, and the machining accuracy meets the requirements.

[0048] This invention replaces spline grinding with boring and milling. Milling the rectangular spline 103 is quick, involving two steps: roughing and finishing. It achieves high machining accuracy, meeting customer requirements for precision and relative positional relationships. The total time for milling the rectangular spline of one gear part is approximately 2 hours. More than 800 gear parts have already been processed. Based on the outsourced grinding cost of 1,000 yuan per piece for the rectangular spline 103, the boring and milling method of this invention costs only about 100 yuan per piece. Processing 800 products can save the company approximately 720,000 yuan in costs.

[0049] In summary, the boring and milling machining technology of this invention is stable and has good manufacturability in the mass production of parts; while ensuring the positional relationship between the top tooth groove of the bevel gear 101 and the outer rectangular spline 103, it achieves the low-cost, high-precision machining requirements of the outer rectangular spline 103 of the bevel gear 101 to meet the design requirements.

[0050] The various embodiments in this specification are described in a related manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A method for milling rectangular splines on gear parts instead of grinding, characterized in that: Includes the following steps: Step 1: Complete the machining of the bevel teeth (101) of the gear part (1); Step 2: Fit the tooth positioning fixture (2) onto the optical shaft (102) of the gear part (1) with an interference fit to ensure that after the tooth positioning fixture (2) is assembled, the diameter B0 of its core hole (201) and the diameter A0 of the optical shaft (102) of the gear part (1) fit without gap; and make the front end face of the tooth positioning fixture (2) fit tightly against the rear end face of the bevel tooth (101) of the gear part (1); Step 3: Install cylindrical pins (3) in the symmetrical cylindrical pin holes (202) of the tooth positioning fixture (2); and make the front ends of the two cylindrical pins (3) extend out of the tooth positioning fixture (2), and make the front end of the cylindrical pins (3) tangent to the arc of the tooth groove of the adjacent tooth of the bevel tooth (101), so that the cylindrical pins (3) hook the bevel tooth (101) tooth to limit the position of the gear part (1), and use this position to determine the starting position of the rectangular spline (103) of the gear part (1); Step 4: Level the tooth positioning fixture (2), align the boring and milling forming tool (4) and center it, then rotate the tooth positioning fixture (2) together with the gear part (1) by a certain angle. The angle of rotation is used to correspond to the positional relationship between the rectangular spline (103) and the tooth tip groove of the bevel tooth (101), and then start the milling of the rectangular spline (103). The tooth positioning fixture (2) is a disc structure with horizontal cross-sections on the upper and lower parts and a central hole (201) in the center; the upper and lower center positions of the disc body are respectively provided with axially symmetrical cylindrical pin holes (202); the center distance B1 of the upper and lower cylindrical pin holes (202) matches the number of teeth and module of the gear part (1) to ensure that the circular arcs at the tooth grooves of the cylindrical pin (3) and the bevel tooth (101) are tangent; the outer diameter B3 of the disc body matches the size of the tip circle of the bevel tooth (101) of the gear part (1); the axial thickness B4 of the disc body is smaller than the axial length A2 of the boss of the optical axis (102).

2. The processing method according to claim 1, characterized in that: Step 4 is divided into two steps: rough milling and finish milling to complete the machining of the rectangular spline (103). During rough milling, ensure the minor diameter φd and key width L of the rectangular spline (103). During finish milling, the tolerance grade of the minor diameter φd is at least G7 and the tolerance grade of the key width L is at least F9.

3. The processing method according to claim 1, characterized in that: The cutting edge size of the boring and milling forming tool (4) matches the size of the rectangular spline (103); the shank of the boring and milling forming tool (4) does not interfere with the outer circle near the rectangular spline (103).

4. A milling fixture for machining rectangular splines on gear parts instead of grinding, characterized in that: The machining fixture is the tooth positioning fixture (2) used in the machining method of any one of claims 1-3.

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