A method and special fixture for improving the tool life of hard turning parts such as dial heads

Abstract

This invention discloses a method and a special fixture for improving the tool life of hard turning of dial-type parts. Step 1: Before heat treatment: A frustum is milled on the mating surface of the dial-type part and its mating component, with the axis of the unmachined threaded hole as the center. The diameter of the frustum is ΦD. Step 2: Anti-seepage treatment: Before entering the furnace for heat treatment, an anti-nitriding coating is applied to the end face and periphery of the frustum to reduce surface hardness. Step 3: Heat treatment: The dial-type part is nitrided. Step 4: Hard turning: Using a CNC lathe and a hydraulic chuck, and with special jaws to clamp the dial-type part, the threaded hole of the dial-type part is hard turned, and the frustum is hard turned. This invention reduces the intermittent cutting area on the hard-turned end face after nitriding, thus improving tool life. The special jaws used to clamp the dial reduce vibration caused by intermittent cutting, further improving the tool life of hard turning.

Description

Technical Field

[0001] This invention relates to the field of turning tool life improvement technology, specifically a method and special fixture for improving the tool life of hard turning tools for turner-type parts. Background Technology

[0002] Appendix Figure 1 The dial indicator shown is one of the core components of an axial piston hydraulic pump. It is commonly made of 38CrMoAl nitrided steel. The spherical surface requires nitriding heat treatment to improve its hardness and wear resistance. However, after nitriding, the stress concentration at the root of the thread causes thread breakage or fracture when tightening torque. The common method to solve this problem is to hard turn after nitriding. After nitriding, the surface hardness of the dial indicator is greater than 900HV10, which is high and requires intermittent cutting. Hard turning results in low tool life, high machining difficulty, and high manufacturing cost. Summary of the Invention

[0003] In view of the above-mentioned defects in the existing technology, the purpose of this invention is to provide a method and special fixture for improving the tool life of hard turning of dial head parts, to solve the difficulties in the existing technology, reduce the machining difficulty, increase tool life and reduce manufacturing costs.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A method for improving the tool life in hard turning of dial-type parts includes the following steps:

[0006] Step 1, before heat treatment: On the mating surface of the head part and the mating part, a frustum is milled with the axis of the unmachined threaded hole as the center. The diameter of the frustum is ΦD. The diameter of the frustum ΦD is 0.5-1mm larger than the diameter of the mating part, and the height of the frustum is 0.5-1mm.

[0007] Step 2, anti-seepage treatment: Before entering the furnace for heat treatment, anti-nitriding coating needs to be applied to the end face and surrounding area of ​​the truncated cone to reduce surface hardness. The anti-nitriding coating should be stirred evenly before use and allowed to dry naturally in ventilation.

[0008] Step 3, Heat treatment: Nitriding treatment is performed on the head parts;

[0009] Step 4, Hard turning: Using a CNC lathe and a hydraulic chuck, and using special jaws to hold the dial head parts, after clamping, hard turn the threaded hole of the dial head and hard turn the frustum.

[0010] The puller part includes a cylindrical body, a conical body, and a rectangular body; the cylindrical body is located at the upper end of the conical body, and the rectangular body is located at the lower end of the conical body.

[0011] The jaws include a first jaw, a second jaw, and a third jaw; the first jaw is provided with a cylindrical groove, the diameter of which is larger than the diameter of the cylinder; the second jaw is provided with a first rectangular single-corner groove and a second rectangular single-corner groove.

[0012] The first rectangular body has a first corner protection groove in its single-corner recess, and the second rectangular body has a second corner protection groove in its single-corner recess.

[0013] The first jaw, the second jaw, and the third jaw are mounted to the hydraulic chuck by the first bolt, and the hydraulic chuck is mounted to the CNC lathe by the second bolt.

[0014] Step 4: When installing the puller part, place the cylindrical body into the cylindrical groove of the first claw, so that the first claw holds the upper end face of the rectangle, the second claw holds the left end face and the lower end face of the rectangle, and the third claw holds the right end face and the lower end face of the rectangle; the lower left corner of the rectangle is suspended in the first corner protection groove, and the lower right corner of the rectangle is suspended in the second corner protection groove.

[0015] A special fixture for hard turning of dial-type parts includes a first jaw, a second jaw, and a third jaw;

[0016] The first claw is provided with a cylindrical groove, the diameter of which is larger than the diameter of the cylinder; the second claw is provided with a first rectangular single-corner groove; the second claw is provided with a second rectangular single-corner groove.

[0017] The first rectangular body has a first corner protection groove in its single-corner recess, and the second rectangular body has a second corner protection groove in its single-corner recess.

[0018] The first jaw, the second jaw, and the third jaw are mounted to the hydraulic chuck by the first bolt, and the hydraulic chuck is mounted to the CNC lathe by the second bolt.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] Before heat treatment, the periphery of the mating surface between the dial head and the mating part is milled off to reduce the intermittent cutting area on the hard-turned end face after nitriding, thereby improving tool life. Anti-nitriding coating is applied to the hard-turned end face and periphery to reduce surface hardness, and special chucks are made to hold the dial head to reduce vibration caused by intermittent cutting, thus improving the tool life for hard-turning of dial head parts. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the external structure of common dial-type parts in axial piston hydraulic pumps;

[0022] Figure 2This is a schematic diagram of the frustum machined in step 1 of the method for improving the tool life of hard turning of dial-type parts according to the present invention.

[0023] Figure 3 This is a schematic diagram of the structure of a special fixture for hard turning tools of dial head type parts according to the present invention;

[0024] In the diagram: 1. Hydraulic chuck; 2. First jaw; 3. Second jaw; 4. Third jaw; 5. Pulling head part; 6. First bolt; 7. Second bolt. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] This invention provides a method for improving the tool life of hard turning parts, which is implemented according to the following steps:

[0027] Step 1, before heat treatment:

[0028] The mating surfaces of the head part 5 and the mating parts are milled as shown in the attached figure. Figure 2 As shown, a frustum of a circle with the axis of the unmachined threaded hole as its center has a diameter of ΦD, which is 0.5-1mm larger than the diameter of the mating part, and a height of 0.5-1mm. The purpose is to reduce the intermittent cutting area of ​​the hard-turned end face after nitriding to improve tool life.

[0029] Step 2, seepage prevention treatment:

[0030] Before entering the furnace for heat treatment, an anti-nitriding coating needs to be applied to the end face and perimeter of the frustum to reduce surface hardness. The anti-nitriding coating should be stirred evenly before use and allowed to dry naturally in a ventilated environment. The anti-nitriding coating can be purchased from the market, as those skilled in the art will know.

[0031] Step 3, Heat Treatment:

[0032] Nitriding treatment is performed on the head part 5;

[0033] Step 4, Hard Car:

[0034] Use as per attached. Figure 3 The hydraulic chuck used on the CNC lathe is shown, and special jaws are used to hold the dial head part 5. This jaw holding the dial head can reduce the vibration caused by intermittent cutting, improve the rigidity of the dial head, and thus improve the tool life of hard turning.

[0035] After clamping, the threaded hole of the head is hard-machined, and the mating surface of the mating parts is hard-machined into a frustum.

[0036] The head-pulling component 5 includes a cylindrical body, a conical body, and a rectangular body; the cylindrical body is located at the upper end of the conical body, and the rectangular body is located at the lower end of the conical body.

[0037] The jaws include a first jaw 2, a second jaw 3, and a third jaw 4; the first jaw 2 is provided with a cylindrical groove, the diameter of which is larger than the diameter of the cylinder; the second jaw is provided with a first rectangular single-corner groove and a second rectangular single-corner groove; the first rectangular single-corner groove is provided with a first corner protection groove and the second rectangular single-corner groove is provided with a second corner protection groove.

[0038] The first jaw 2, the second jaw 3, and the third jaw 4 are mounted to the hydraulic chuck 1 by a first bolt, and the hydraulic chuck 1 is mounted to the CNC lathe by a second bolt. Both the hydraulic chuck 1 and the CNC lathe are existing technologies, as will be clear to those skilled in the art.

[0039] Step 4: When installing the puller part 5, place the cylindrical body into the cylindrical groove of the first claw 2, so that the first claw 2 holds the upper end face of the rectangular body, the second claw 3 holds the left end face and the lower end face of the rectangular body, and the third claw holds the right end face and the lower end face of the rectangular body; the lower left corner of the rectangular body is suspended in the first corner protection groove, and the lower right corner of the rectangular body is suspended in the second corner protection groove.

[0040] All components not discussed in detail in this application, as well as the connection methods of these components, are well-known technologies in this field. They can be directly applied and will not be elaborated further.

[0041] In this invention, the term "multiple" refers to two or more unless otherwise explicitly defined. The terms "install," "connect," "link," and "fix" should be interpreted broadly. For example, "connect" can be a fixed connection, a detachable connection, or an integral connection; "link" can be a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0042] In the description of this invention, it should be understood that the terms "upper," "lower," "left," "right," "front," "rear," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or unit referred to must have a specific orientation or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving the tool life of hard turning parts of the dial head type, characterized in that, Includes the following steps: Step 1, before heat treatment: On the mating surface of the dial part and the mating part, a frustum is milled with the axis of the unmachined threaded hole as the center. The diameter of the frustum is ΦD. Step 2, anti-seepage treatment: Before entering the furnace for heat treatment, anti-nitriding coating needs to be applied to the end face and surrounding area of ​​the truncated cone to reduce surface hardness. The anti-nitriding coating should be stirred evenly before use and allowed to dry naturally in ventilation. Step 3, Heat treatment: Nitriding treatment is performed on the dial head parts; Step 4, Hard turning: Using a CNC lathe and a hydraulic chuck, and using special jaws to hold the dial head part, after clamping, hard turn the threaded hole of the dial head and hard turn the frustum. The dial component includes a cylindrical body, a conical body, and a rectangular body; the cylindrical body is disposed at the upper end of the conical body, and the rectangular body is disposed at the lower end of the conical body; The jaws include a first jaw, a second jaw, and a third jaw; the first jaw is provided with a cylindrical groove, the diameter of which is larger than the diameter of the cylindrical body; the second jaw is provided with a first rectangular single-corner groove; and the third jaw is provided with a second rectangular single-corner groove. The first rectangular body has a first corner protection groove in its single-corner recess, and the second rectangular body has a second corner protection groove in its single-corner recess.

2. The method for improving the tool life of hard turning parts for dial head components according to claim 1, characterized in that, The diameter ΦD of the frustum is 0.5-1mm larger than the diameter of the pair, and the height of the frustum is 0.5-1mm.

3. The method for improving the tool life of hard turning parts for dial head type parts according to claim 1, characterized in that, The first jaw, the second jaw, and the third jaw are mounted to the hydraulic chuck by the first bolt, and the hydraulic chuck is mounted to the CNC lathe by the second bolt.

4. The method for improving the tool life of hard turning parts for dial head type parts according to claim 3, characterized in that, Step 4: When installing the dial head parts, place the cylindrical body into the cylindrical groove of the first claw, so that the first claw holds the upper end face of the rectangular body, the second claw holds the left end face and the lower end face of the rectangular body, and the third claw holds the right end face and the lower end face of the rectangular body; the lower left corner of the rectangular body is suspended in the first corner protection groove, and the lower right corner of the rectangular body is suspended in the second corner protection groove.

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