A method for measuring the straightness of the inner cavity of long cylindrical parts

Abstract

The present invention discloses a method for measuring the inner cavity straightness of a long cylindrical part, comprising the following steps: the long cylindrical part is positioned on a V-shaped support frame of an auxiliary device with an outer circle, the auxiliary device is pushed to one end of a linear guide rail, a three-dimensional probe enters the inner cavity of the long cylindrical part, and a plurality of cross-sectional circles are collected in sequence from the end surface inward, and a two-dimensional straight line is constructed with the center of the circle; the auxiliary device is pushed to the other end of the linear guide rail, a three-dimensional probe enters the other end of the inner cavity of the long cylindrical part, and a plurality of cross-sectional circles are collected in sequence from the end surface inward, and another two-dimensional straight line is constructed with the center of the circle; the two constructed two-dimensional straight lines are fitted into a three-dimensional straight line, and the straightness of the straight line is evaluated, that is, the inner cavity straightness of the long cylindrical part. The method of the present invention is mainly used for measuring the inner cavity straightness of a cylinder when the length is greater than the measuring range of a three-dimensional measuring machine, and has high measurement accuracy.

Description

Technical Field

[0001] The invention relates to the field of measurement technology, in particular to a method for measuring the straightness of the inner cavity of a long cylindrical part. Background Art

[0002] For the straightness detection of long cylindrical products, commonly used measurement methods include busbar measurement method, axis measurement method, etc., but these conventional methods all take points on the outer circle of the cylinder and use the axis of the outer cylindrical surface to evaluate the straightness of the cylinder. When the coaxiality between the outer circle and the inner hole of the cylinder is not ideal, the axis straightness of the outer circle cannot represent the straightness of the cylinder, and the straightness of the inner cavity needs to be detected and evaluated. The present invention provides a three-coordinate measurement device and method for the straightness of the inner cavity of long cylindrical parts, which can detect the straightness of the inner cavity of a cylinder whose length is greater than the three-coordinate measurement range, and provides a point element fitting and evaluation method to achieve accurate detection of the straightness of the inner cavity of long cylindrical workpieces. Summary of the invention

[0003] The purpose of the present invention is to provide a method for measuring the straightness of the inner cavity of a long cylindrical part in view of the problem that it is inconvenient to measure the straightness of the inner cavity of a long cylindrical part in the prior art.

[0004] The technical solution adopted to achieve the purpose of the present invention is:

[0005] A method for measuring the straightness of the inner cavity of a long cylindrical part comprises the following steps:

[0006] Step 1, assembling the auxiliary device on the three-dimensional coordinate measuring machine; the auxiliary device includes a linear guide rail, a slider slidably connected to the linear guide rail, and a V-shaped support frame fixed on the slider,

[0007] Step 2: After the long cylindrical part is positioned with its outer circle, it is placed on the V-shaped support frame of the auxiliary device, and the auxiliary device is pushed to one end of the linear guide rail. The three-dimensional probe enters the inner cavity of the long cylindrical part, and collects several cross-sectional circles from the end surface inward in sequence, and constructs a two-dimensional straight line with the center of the circle;

[0008] Step 3: Push the auxiliary device to the other end of the linear guide rail, and the three-dimensional probe enters the other end of the inner cavity of the long cylindrical part. Similarly, several cross-sectional circles are collected from the end surface inward in sequence, and another two-dimensional straight line is constructed with the center of the circle;

[0009] Step 4, fitting the two two-dimensional straight lines constructed in steps 2 and 3 into a three-dimensional straight line, and evaluating the straightness of the straight line, that is, the straightness of the inner cavity of the long cylindrical part.

[0010] In the above technical solution, the auxiliary device includes a linear guide rail, a slider, a V-shaped support frame and a connecting rod; the linear guide rail is provided with a guide rail through hole for positioning, and the sliding distance of the linear guide rail is greater than 1 / 3 of the length of the long cylindrical parts; there are two sliders, and each slider is slidably connected to the linear guide rail; a V-shaped support frame is fixed to the top of each slider, and the top surface of the V-shaped support frame is a V-shaped surface for supporting the outer circle of the long cylindrical parts, and the two V-shaped support frames and / or the two sliders are fixedly connected by the connecting rod.

[0011] In the above technical solution, the linear guide is a precision linear guide, and the full-range straightness of the linear guide is less than 0.01 mm.

[0012] In the above technical solution, the V-shaped angle of the V-shaped support frame is 90 to 150°.

[0013] In the above technical solution, screws pass through the guide rail through holes to fix the linear guide rail on the three-coordinate plate of the three-coordinate measuring machine, and the length of the probe system of the three-coordinate measuring machine is not less than 1 / 3 of the length of the long cylindrical part.

[0014] In the above technical solution, the hole spacing of the guide rail through holes is equal to the hole spacing of the three-coordinate plate screw holes, which can improve the assembly precision of the auxiliary device and the three-coordinate measuring machine.

[0015] In the above technical solution, the probe system is a step probe system.

[0016] In the above technical solution, the measuring rod of the step probe system is a step rod, the end of the measuring rod is equipped with a hemispherical measuring head, and the diameter of the hemispherical measuring head is larger than the maximum diameter of the measuring rod.

[0017] In the above technical solution, the step rod is formed by connecting measuring rods of different diameters.

[0018] In the above technical solution, the assembly method of step 1 includes:

[0019] Step S1, firstly, the linear guide is fastened to the three-coordinate plate with screws, and the parallelism is checked by a three-coordinate measuring machine. The checking standard is: the coordinate values ​​at both ends of the linear guide differ within 0.01 mm, which is considered to be qualified for parallelism;

[0020] Step S2, assemble the slider, V-shaped support frame and connecting rod, and assemble them on the linear guide rail, and check that the surface parallelism between the two V-shaped support frames and the parallelism between each side surface and the three-coordinate X axis or Y axis are less than 0.01mm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The present invention uses a three-coordinate measuring machine combined with an auxiliary device (a movable positioning mechanism) to complete the measurement, and uses a spatial axis fitting method for comprehensive evaluation, which can achieve accurate detection of the straightness of the inner cavity of the cylinder.

[0023] 2. The method of the present invention is mainly used to measure the straightness of the inner cavity of a cylinder when the length is greater than the measuring range of a three-coordinate measuring machine. It provides an over-range geometric quantity detection method. The method makes full use of the coordinate measurement characteristics of the three-coordinate measuring machine, designs a slidable positioning mechanism, and uses the coordinate system of the three-coordinate to calibrate its positioning accuracy. The overall positioning accuracy is greater than 0.01mm.

[0024] 3. The segmented point sampling method is used to obtain the straightness of the cylinder through two-dimensional and three-dimensional fitting. Three cross-sectional circles are measured at both ends, and a 2D straight line is constructed with the center of the cross-sectional circle, which is then fitted into a 3D straight line as the inner axis of the cylinder. This method can realize the precise detection of the geometric quantity and form and position tolerance of the over-range cylinder under the condition of limited range of precision measuring instruments. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the overall hardware structure of the device for measuring the inner cavity straightness of a long cylindrical part in Example 2;

[0026] Figure 2 This is a diagram of an auxiliary device (slidable positioning mechanism) for measuring the straightness of the inner cavity of a long cylindrical part in Example 1.

[0027] Figure 3 This is the structural diagram of the step probe system.

[0028] Figure 4 This is a schematic diagram of the Y+ direction sampling points for long cylindrical parts.

[0029] Figure 5 This is a schematic diagram of the Y-axis sampling points for long cylindrical parts.

[0030] Figure 6 (a) is the two-dimensional straight line constructed in step 3 in Example 3, (b) is the two-dimensional straight line constructed in step 4 in Example 3, and (c) is the three-dimensional straight line constructed in step 5 in Example 3.

[0031] In the figure: 1-precision linear guide, 2-slider, 3-V-type support frame, 4-long cylindrical parts, 5-probe system, 6-connecting rod, 7-three-coordinate measuring machine; 5-1-step rod, 5-2-hemispherical probe. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] Example 1

[0034] An auxiliary device for measuring the inner straightness of a long cylindrical part, comprising a linear guide rail 1, a slide block 2, a V-shaped support frame 3 and a connecting rod 6;

[0035] The linear guide rail 1 is provided with a guide rail through hole for positioning, and the sliding distance of the linear guide rail 1 is greater than 1 / 3 of the length of the long cylindrical part 4; there are two sliders 2, and each slider 2 is slidably connected to the linear guide rail 1; a V-shaped support frame 3 is fixed to the top of each slider 2, and the top surface of the V-shaped support frame 3 is a V-shaped surface for supporting the outer circle of the long cylindrical part 4, and the two V-shaped support frames 3 and / or the two sliders 2 are fixedly connected by the connecting rod 6.

[0036] The linear guide 1 is a precision linear guide. The screws passing through the guide holes can realize the assembly of the auxiliary device and the three-coordinate plate. The slider 2 is a matching accessory of the linear guide 1. It adopts a double slider design. The two sliders 2 are connected by a connecting rod 6 and can move synchronously along the guide. The connecting rod 6 is a connecting component of the two V-shaped support frames 3. Its length can be selected according to the length of the long cylindrical part 4 to be measured and the support position.

[0037] Preferably, the linear guide rail 1 has a straightness of less than 0.01 mm over the entire range.

[0038] Preferably, the V-shaped angle of the V-shaped support frame 3 is 90-150°, which can be matched according to the diameter of the long cylindrical part 4 .

[0039] Example 2

[0040] A device for measuring the inner straightness of a long cylindrical part, comprising a three-coordinate measuring machine 7 and the auxiliary device for measuring the inner straightness of a long cylindrical part as described in Example 1, wherein screws pass through the guide rail through holes to fix the linear guide rail 1 on the three-coordinate plate of the three-coordinate measuring machine 7, and the length of the probe system 5 of the three-coordinate measuring machine 7 is not less than 1 / 3 of the length of the long cylindrical part 4.

[0041] The three-coordinate measuring machine 7 is a general precision measuring device with a measuring accuracy better than 3.0+L / 200μm and a straightness evaluation function. The difference between its X or Y axis range and the length of the measured cylinder is not greater than the moving distance of the auxiliary device (movable positioning mechanism) of Example 1.

[0042] Preferably, the hole spacing of the guide rail through holes is equal to the hole spacing of the three-coordinate plate screw holes, so as to improve the assembly precision of the auxiliary device and the three-coordinate measuring machine 7.

[0043] Preferably, the probe system 5 is a step probe system.

[0044] Preferably, the measuring rod of the step probe system is a step rod 5-1, and the end of the measuring rod is equipped with a hemispherical measuring head 5-2, and the diameter of the hemispherical measuring head 5-2 is greater than the maximum diameter of the measuring rod. Reduce the weight of the measuring head system 5 and improve the accuracy of measuring points. The step probe system is a combined probe system. The measuring rod is formed by connecting measuring rods of different diameters. The end is equipped with a hemispherical measuring head 5-2, and the ball diameter is greater than the maximum diameter of the measuring rod. While meeting the maximum measurement depth point, the weight of the measuring head system 5 is minimized.

[0045] Example 3

[0046] The measuring method of the inner cavity straightness measuring device of the long cylindrical parts comprises the following steps:

[0047] Step 1, firstly, fasten the linear guide rail 1 to the three-coordinate plate with screws, and use the three-coordinate measuring machine 7 to check the parallelism. The checking standard is: the coordinate values ​​at both ends of the linear guide rail 1 differ by less than 0.01 mm, which is considered to be qualified for parallelism;

[0048] Step 2, assemble the slider 2, the V-shaped support frame 3 and the connecting rod 6, and assemble them on the linear guide rail 1, and check that the surface parallelism between the two V-shaped support frames 3 and the parallelism of each side surface and the three-coordinate X axis (or Y axis) are less than 0.01 mm;

[0049] Step 3: After the long cylindrical part 4 is positioned with its outer circle on the V-shaped support frame 3, the auxiliary device is pushed to one end of the linear guide rail 1, and the three-dimensional probe enters the inner cavity of the long cylindrical part 4, collects several cross-sectional circles from the end surface inward in sequence, and constructs a two-dimensional straight line with the center of the circle;

[0050] Step 4, push the auxiliary device to the other end of the linear guide rail 1, and the three-dimensional probe enters the other end of the inner cavity of the long cylindrical part 4. Similarly, several cross-sectional circles are collected in sequence from the end surface inward, and another two-dimensional straight line is constructed with the center of the circle.

[0051] Step 5, fitting the two two-dimensional straight lines constructed in step 3 and step 4 into a three-dimensional straight line, and evaluating the straightness of the straight line, that is, the straightness of the inner cavity of the long cylindrical part 4.

[0052] The above description is only a preferred embodiment of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements can be made without departing from the principle of the present invention, and these improvements should also be regarded as the scope of protection of the present invention.

Claims

1. A method for measuring the straightness of the inner cavity of a long cylindrical part, characterized in that: The following steps are involved: Step 1, assembling the auxiliary device on the three-dimensional coordinate measuring machine; the auxiliary device includes a linear guide rail, a slider slidably connected to the linear guide rail, and a V-shaped support frame fixed on the slider, Step 2: After the long cylindrical part is positioned with its outer circle, it is placed on the V-shaped support frame of the auxiliary device, and the auxiliary device is pushed to one end of the linear guide rail. The three-dimensional probe enters the inner cavity of the long cylindrical part, and collects several cross-sectional circles from the end surface inward in sequence, and constructs a two-dimensional straight line with the center of the circle; Step 3: Push the auxiliary device to the other end of the linear guide rail, and the three-dimensional probe enters the other end of the inner cavity of the long cylindrical part. Similarly, several cross-sectional circles are collected from the end surface inward in sequence, and another two-dimensional straight line is constructed with the center of the circle; Step 4, fitting the two two-dimensional straight lines constructed in step 2 and step 3 into a three-dimensional straight line, and evaluating the straightness of the straight line, that is, the straightness of the inner cavity of the long cylindrical part; The auxiliary device includes a linear guide rail, a slider, a V-shaped support frame and a connecting rod; the linear guide rail is provided with a guide rail through hole for positioning, and the sliding distance of the linear guide rail is greater than 1 / 3 of the length of the long cylindrical part; there are two sliders, and each slider is slidably connected to the linear guide rail; a V-shaped support frame is fixed to the top of each slider, and the top surface of the V-shaped support frame is a V-shaped surface for supporting the outer circle of the long cylindrical part, and the two V-shaped support frames and / or the two sliders are fixedly connected by the connecting rod.

2. The method for measuring the inner straightness of a long cylindrical part according to claim 1, characterized in that: The linear guide is a precision linear guide, and the full-range straightness of the linear guide is less than 0.01 mm.

3. The method for measuring the inner straightness of a long cylindrical part according to claim 1, characterized in that: The V-shaped angle of the V-shaped support frame is 90-150°.

4. The method for measuring the inner straightness of a long cylindrical part according to claim 1, characterized in that: The screws pass through the guide rail through holes to fix the linear guide rail on the three-coordinate plate of the three-coordinate measuring machine. The length of the probe system of the three-coordinate measuring machine is not less than 1 / 3 of the length of the long cylindrical part.

5. The method for measuring the inner straightness of a long cylindrical part according to claim 4, characterized in that: The hole spacing of the guide rail through holes is equal to the hole spacing of the three-coordinate plate screw holes.

6. The method for measuring the inner straightness of a long cylindrical part according to claim 1, characterized in that: The probe system of the coordinate measuring machine is a stepped probe system.

7. The method for measuring the inner straightness of a long cylindrical part according to claim 6, characterized in that: The measuring rod of the step probe system is a step rod, the end of the measuring rod is equipped with a hemispherical measuring head, and the diameter of the hemispherical measuring head is larger than the maximum diameter of the measuring rod.

8. The method for measuring the inner straightness of a long cylindrical part according to claim 7, characterized in that: The step rod is formed by connecting measuring rods with different diameters.

9. The method for measuring the inner straightness of a long cylindrical part according to claim 1, characterized in that: The assembly method of step 1 comprises: Step S1, firstly, the linear guide is fastened to the three-coordinate plate with screws, and the parallelism is checked by a three-coordinate measuring machine. The checking standard is: the coordinate values ​​at both ends of the linear guide differ within 0.01mm, which is considered to be qualified for parallelism; Step S2, assemble the slider, V-shaped support frame and connecting rod, and assemble them on the linear guide rail, and check that the surface parallelism between the two V-shaped support frames and the parallelism between each side surface and the three-coordinate X axis or Y axis are less than 0.01mm.

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