A boring method for a trumpet hole

Abstract

This invention discloses a boring method for flared holes, mainly including the following steps: Step 1, refining the product coordinate points of the flared hole line shape. Using MATLAB software, the coordinate points of each product required for the flared hole line shape are smoothly connected, fitting the flared hole lines on both sides and the middle straight line segment into a smooth transition curve. The resulting coordinate points are used as theoretical coordinate points. Step 2, combining the theoretical coordinate points with the initial position of the tool during the actual boring process, the actual coordinate points for boring on the machine tool are obtained. The actual coordinate points are input into the machine tool's control system to achieve the boring of the circular flared hole using a point-to-point control method. Step 3, using a cylindricity gauge to detect the straightness of the flared hole. Step 4, adjusting and optimizing the boring coordinate points. Based on the straightness detection results from the cylindricity gauge, the actual coordinate points are optimized. This boring method can greatly improve the machining accuracy of the flared hole, and the profile of the machined flared hole can meet 0.004mm.

Description

Technical Field

[0001] This invention relates to the field of engine connecting rods, and more particularly to a boring method for a flared hole. Background Technology

[0002] like Figure 1 and 2 As shown, the circular horn hole at the small end of the connecting rod of an automobile engine includes a straight area in the middle and horn hole areas on both sides. In the traditional machining method, the horizontal coordinate displacement value is used as the independent variable and the vertical coordinate compensation value is used as the dependent variable. That is, the shape of the horn hole is optimized by adjusting and optimizing the horizontal coordinate displacement value. During the boring process, due to the different spacing of the horizontal coordinate displacement value setting, the machined horn hole shape is a multi-segment line connection rather than a smooth transition, resulting in low machining accuracy of the circular horn hole at the small end of the connecting rod. Summary of the Invention

[0003] Based on the above problems, the purpose of this invention is to provide a boring method for horn holes. The invention adopts the following technical solution:

[0004] This invention provides a boring method for a flared hole, comprising the following steps:

[0005] Step 1: Refine the product coordinate points of the horn hole line shape on both sides. Use MATLAB mathematical software to smoothly connect the product coordinate points required for the circular horn hole line shape. Fit the horn hole line shape on both sides and the middle straight line segment into a smooth transition curve. The coordinate points derived from this are used as theoretical coordinate points.

[0006] Step 2: Based on the theoretical coordinate points of the circular horn hole linear boring obtained in Step 1, and combined with the initial position of the tool during the actual boring process, the actual coordinate points of the machine tool boring are obtained.

[0007] The actual coordinate points are input into the machine tool's control system to achieve the boring of the circular flared hole in a point-to-point control manner; the boring of the circular flared hole is carried out in two steps: semi-finish boring and finish boring.

[0008] Step 3: Linearity inspection of the circular horn hole. Use a cylindricity tester to check the straightness of the horn hole, and use a profile meter or coordinate measuring machine to check and confirm the profile.

[0009] Step 4: Adjust and optimize the boring coordinate points. Based on the straightness graphic detection results from the cylindricity tester, optimize the actual coordinate points.

[0010] Preferably, in step one, when using MATLAB mathematical software for fitting, it is necessary to perform fitting from second order to N order (N≥3) respectively to confirm the optimal order of the smooth transition between the two sides of the horn hole line shape and the middle straight line segment, and output the coordinate points derived from this order as the theoretical coordinate points.

[0011] When outputting theoretical coordinate points using MATLAB mathematical software, the vertical coordinate compensation value is used as the independent variable, and the horizontal coordinate displacement value is used as the dependent variable; the vertical coordinate compensation value is taken as the minimum compensation unit of the tool compensation system, and the vertical coordinate compensation value is ≤0.5μm.

[0012] Preferably, in step two, the initial position of the tool includes the actual tool compensation value at the straight segment of the initial position of the tool from the horn hole, and the displacement value of the initial position of the tool from the infeed side of the horn hole.

[0013] Preferably, in step two, the tool compensation system of the machine tool adopts a mechanical shift fork; the tool compensation system of the mechanical shift fork sets a reverse clearance tool compensation zero point at the position of the tool reaching the middle straight section of the horn hole line on the horn hole inlet side.

[0014] Preferably, in step two, when boring the circular flared hole, a continuous transition area of ​​1 mm or more for the tool compensation system should be left on both sides of the flared hole.

[0015] Preferably, in step two, the semi-finish boring and finish boring steps are performed on the same positioning datum; the semi-finish boring and finish boring steps use special cutting tools, which are equipped with two sets of inserts to complete the semi-finish boring and finish boring respectively; wherein the machining allowance of the semi-finish boring is 0.25~0.35mm, and two fixed inserts are used; the finish boring uses an adjustable diameter insert, which is a single insert.

[0016] Preferably, in step three, the straightness graph of the horn hole line shape detected by the cylindricity tester is very intuitive and is used as the adjustment benchmark for optimizing the actual coordinate points; at the same time, the straightness graph and the profile inspection report issued by the profile meter or coordinate measuring machine are checked, and the profile inspection report is used as the basis for the final report.

[0017] Preferably, in step four, when adjusting and optimizing the actual coordinate point position of the machine tool boring, only the vertical coordinate compensation value is adjusted, while the horizontal coordinate displacement value remains unchanged.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0019] This boring method can greatly improve the machining accuracy of the horn hole, is easy to adjust, has low machining cost, is suitable for mass production, and the profile of the machined horn hole can meet 0.004mm. Attached Figure Description

[0020] The present invention will be further described below with reference to the accompanying drawings.

[0021] Figure 1 A schematic diagram of the main view structure of the circular horn hole at the small end of the existing connecting rod;

[0022] Figure 2 This is a longitudinal sectional view of the circular flared hole at the small end of the existing connecting rod.

[0023] Figure 3 The product coordinates are the lower linear shape of the circular horn hole in this invention;

[0024] Figure 4 This is a schematic diagram of the boring of the circular horn hole in this invention;

[0025] Figure 5 This illustrates the initial position of the cutting tool in this invention and its relationship to the position of the circular horn hole.

[0026] Figure 6 This is a schematic diagram of the tool structure of the present invention. Detailed Implementation

[0027] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. "Several" means one or more, unless otherwise explicitly specified.

[0029] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", 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 element 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.

[0030] like Figures 1 to 4 As shown, this embodiment discloses a boring method for a horn hole. Taking the machining of a circular horn hole at the small end of an automotive engine connecting rod as an example, the method includes the following steps:

[0031] Step 1: Refine the product coordinate points of the horn hole line shape on both sides. Use MATLAB mathematical software to smoothly connect the product coordinate points required by the circular horn hole line shape, and fit the horn hole line shape on both sides with the middle straight line segment into a smooth transition curve. The coordinate points derived from this are used as theoretical coordinate points.

[0032] When using MATLAB mathematical software for fitting, it is necessary to perform fitting from second order to N order (N≥3) to determine the optimal order for the smooth transition between the two sides of the horn hole line shape and the middle straight line segment. The coordinate points derived from this order are then used as the theoretical coordinate points for output.

[0033] When outputting theoretical coordinate points using MATLAB mathematical software, the vertical coordinate compensation value is used as the independent variable, and the horizontal coordinate displacement value is used as the dependent variable; the vertical coordinate compensation value is taken as the minimum compensation unit of the tool compensation system, and the vertical coordinate compensation value is ≤0.5μm.

[0034] Step 2: Based on the theoretical coordinate points of the circular horn hole linear boring obtained in Step 1, and combined with the initial position of the tool during the actual boring process, the actual coordinate points of the machine tool boring are obtained. The actual coordinate points are then input into the machine tool's control system to achieve the boring of the circular horn hole in a point-to-point control manner.

[0035] It is important to note that, such as Figure 5 As shown, the initial position of the tool includes the actual tool compensation value at the straight segment from the initial position of the tool to the horn hole, and the displacement value of the initial position of the tool from the infeed side of the horn hole.

[0036] The machine tool performs boring operations, and the boring of the circular trumpet-shaped hole is carried out in two steps: semi-finish boring and finish boring. Because the tool compensation mechanism needs to perform real-time compensation during the boring of the trumpet-shaped holes on both sides, and because the boring entry and exit points are intermittent cuts, the rigidity requirements of the machine tool's tool compensation system are extremely high. Therefore, a machine tool with a mechanical shift fork rigid compensation mechanism is selected, rather than a hydraulic compensation mechanism. The machine tool's tool compensation system can be controlled by a PLC to achieve continuous point-to-point control.

[0037] The tool compensation system is a mechanical shift fork type. Because the compensation is bidirectional (positive and negative) on both sides of the flared hole, the actual boring coordinate point needs to be set with a backlash tool compensation zero point due to the influence of the backlash in the compensation mechanism. That is, the tool compensation system sets a backlash tool compensation zero point at the position where the tool reaches the flared hole inlet side of the flared hole line to the middle straight section. In this embodiment, it is... Figure 3 After the 13th product coordinate point of the lower part of the horn hole, the actual boring coordinate point is adjusted according to the test results.

[0038] To ensure a smooth transition between the linear inlet and outlet of the flared holes on both sides, a continuous transition area of ​​1mm or more for the tool compensation system must be left on both sides of the circular flared hole during the actual boring process.

[0039] Due to the limitations of the boring hole diameter, the tool holder may suffer from insufficient rigidity. To avoid surface delamination caused by uneven stress at the infeed and exit positions during boring of flared holes, the boring process reduces the machining allowance in the finish boring step to lower the overall rigidity requirements of the tool. Semi-finish boring and finish boring steps are performed on the same positioning datum. For example... Figure 6 As shown, the semi-finish boring and finish boring steps each employ specialized cutting tools, each equipped with two sets of inserts to complete the semi-finish boring and finish boring respectively. The semi-finish boring machining allowance is 0.25–0.35 mm, using two fixed inserts. Finish boring uses a single adjustable diameter insert. The finish boring allowance varies depending on the material being machined. For example, when machining alloy steel or copper alloy, the finish boring allowance for alloy steel is 0.1–0.15 mm, while for copper alloy it is 0.15–0.2 mm. This machining method significantly improves processing efficiency and better ensures product quality.

[0040] Step 3: Linearity inspection of the circular horn hole. Use a cylindricity meter to check the straightness of the horn hole, and use a profile meter or coordinate measuring machine to check and confirm the profile.

[0041] The straightness graph obtained by the cylindricity tester for the horn hole line shape is very intuitive and can be used as the adjustment benchmark for optimizing the actual coordinate points. At the same time, the straightness graph is checked against the profile inspection report issued by the profile meter or coordinate measuring machine, and the profile inspection report is used as the basis for the final report.

[0042] Step four: Adjust and optimize the boring coordinate points. Based on the straightness graph detection results from the cylindricity tester, optimize the actual coordinate points. When adjusting and optimizing the actual boring coordinate point positions, only adjust the vertical coordinate compensation value, while keeping the horizontal coordinate displacement value unchanged.

[0043] The following example illustrates the coordinate conversion between theoretical and actual coordinate points in steps one and two:

[0044] Theoretical coordinate point format: {point(offset Yμm, displacement Xmm)}

[0045] Example: Theoretical coordinate points of the infeed side curve (taking a compensation value interval of 1μm as an example, the theoretical horn hole curve offset changes by 0.5μm on one side, and the hole diameter changes by 1μm): 1(10,0), 2(9.5,0.14), 3(9,0.29), 4(8.5,0.43), 5(8,0.58), 6(7.5,0.73), 7(7,0.88), 8(6.5,1.03) , 9(6,1.2), 10(5.5,1.39), 11(5,1.58), 12(4.5,1.78), 13(4,2), 14(3.5,2.24), 15(3,2.5), 16(2.5,2.76), 17(2,3.07), 18(1.5,3.5), 19(1,3.90), 20(0.5,4.5), 21(0,6)

[0046] The actual coordinates of the machine tool boring: The coordinate transformation of the machine tool input point (the compensation value of the machine tool input is the change in hole diameter) is as follows: If the actual tool compensation value at the straight section of the flared hole is 100μm, and the actual displacement value of the flared hole infeed side position is 100mm, then the coordinates of the machine tool input point are: 1(120,100), 2(119,100.14), 3(118,100.29), 4(117,100.43), 5(116,100.58), 6(115,100.73), 7(114,100.88), 8(113, 101.03),9(112,101.2),10(111,101.39),11(110,101.58),12(109,101.78),13(108,102),14(107,102.24),15(106,102.5),16(105,102.76),17(104,103.07),18(103,103.5),19(102,103.9),20(101,104.5),21(100,106).

[0047] It should be noted that when converting theoretical coordinate points into actual coordinate points for machine tool boring, the longitudinal coordinate Y-axis value needs to be multiplied by 2 before adding the tool compensation value.

[0048] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for boring a trumpet-shaped hole, characterized in that: Includes the following steps: Step 1: Refine the product coordinate points of the horn hole line shape on both sides. Use MATLAB mathematical software to smoothly connect the product coordinate points required for the circular horn hole line shape. Fit the horn hole line shape on both sides and the middle straight line segment into a smooth transition curve. The coordinate points derived from this are used as theoretical coordinate points. In step one, when using MATLAB mathematical software for fitting, it is necessary to fit from second order to N order (N≥3) to confirm the optimal order for the smooth transition between the two sides of the horn hole line shape and the middle straight line segment. The coordinate points derived from this order are used as theoretical coordinate points for output. When using MATLAB mathematical software to output theoretical coordinate points, the vertical coordinate compensation value is used as the independent variable and the horizontal coordinate displacement value is used as the dependent variable. Step 2: Based on the theoretical coordinate points of the circular horn hole linear boring obtained in Step 1, and combined with the initial position of the tool during the actual boring process, the actual coordinate points of the machine tool boring are obtained. The actual coordinate points are input into the machine tool's control system to achieve the boring of the circular flared hole in a point-to-point control manner; the boring of the circular flared hole is carried out in two steps: semi-finish boring and finish boring. Step 3: Linearity inspection of the circular horn hole. Use a cylindricity tester to check the straightness of the horn hole, and use a profile meter or coordinate measuring machine to check and confirm the profile. Step 4: Adjust and optimize the boring coordinate points. Based on the straightness graphic detection results from the cylindricity tester, optimize the actual coordinate points.

2. The boring method for the trumpet hole as described in claim 1, characterized in that: The vertical coordinate compensation value is taken as the minimum compensation unit of the tool compensation system, and the vertical coordinate compensation value is ≤0.5μm.

3. The boring method for the trumpet hole as described in claim 2, characterized in that: In step two, the initial position of the tool includes the actual tool compensation value at the straight segment of the initial position of the tool from the horn hole, and the displacement value of the initial position of the tool from the infeed side of the horn hole.

4. The boring method for the trumpet hole as described in claim 3, characterized in that: In step two, the machine tool's tool compensation system adopts a mechanical shift fork method; the tool compensation system of the mechanical shift fork method sets a reverse backlash tool compensation zero point at the position where the tool reaches the position of the straight section from the middle of the horn hole line on the horn hole inlet side.

5. The boring method for the trumpet hole as described in claim 4, characterized in that: In step two, when boring the circular flared hole, a continuous transition area of ​​1 mm or more for the tool compensation system must be left on both sides of the flared hole.

6. The boring method for the trumpet hole as described in claim 1, characterized in that: In step two, the semi-finish boring and finish boring steps are performed on the same positioning datum. The semi-finish boring and finish boring steps use special cutting tools with two sets of inserts, one in front and one behind, to complete the semi-finish boring and finish boring respectively. The semi-finish boring machining allowance is 0.25-0.35mm, and two fixed inserts are used. The finish boring uses an adjustable diameter insert, which is a single insert.

7. The boring method for the trumpet hole as described in claim 1, characterized in that: In step three, the straightness graph of the cylindricity tester for the horn hole line shape is very intuitive and is used as the adjustment benchmark for optimizing the actual coordinate points. At the same time, the straightness graph and the profile test report issued by the profile meter or coordinate measuring machine are checked, and the profile test report is used as the basis for the final report.

8. The boring method for the trumpet hole as described in claim 1, characterized in that: In step four, when adjusting and optimizing the actual coordinate point position of the machine tool boring, only the vertical coordinate compensation value is adjusted, while the horizontal coordinate displacement value remains unchanged.

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