A method for measuring the parallelism of a reference plane and the fixture base used therein.

Abstract

This invention relates to the field of geometric tolerance inspection technology for aerospace parts, specifically to a method for measuring the parallelism of a reference plane and the fixture base used therein. Combined with auxiliary fixture positioning, it can directly measure the parallelism to a reference plane with high accuracy, improving measurement efficiency and reducing measurement errors caused by coordinate measuring machines and other measurement methods, making the measurement of the parallelism of the reference plane more precise and the inspection more efficient. The measurement method of this invention uses an auxiliary adjustment fixture, using two arc-shaped protrusions on the part as positioning references. Part holes one and two are installed on positioning pins, and the height of the lower support screw of the part is adjusted to level the reference plane of the part in the horizontal and vertical directions. A clamping nut is installed to fix the part, and a lever dial indicator is used to detect the parallelism of the measured plane one and the measured plane two. The dial indicator reading is the parallelism of the measured plane to the reference plane.

Description

Technical Field

[0001] This invention relates to the field of geometric tolerance inspection technology for aerospace parts, specifically to a method for measuring the parallelism of a reference plane and the fixture base used therein. Background Technology

[0002] Parallelism of a part to a reference plane is usually measured using a coordinate measuring machine (CMM) to establish a reference. CMM is generally used for measuring regular planes. However, when the shape is irregular, there are through holes in the central area, and there are many line segments and arcs that make up the shape, CMM establishes a reference plane and checks the parallelism of the measured plane to the reference. This method is time-consuming, inefficient, and has a large measurement error.

[0003] Therefore, in order to measure the parallelism of a part to a reference plane, this invention proposes an efficient and accurate measurement scheme. Summary of the Invention

[0004] In view of this, the present invention provides a method for measuring the parallelism of a reference plane and a fixture base used therein. With the help of an auxiliary fixture for positioning, it can directly measure the parallelism of the reference plane, with high measurement accuracy, improved measurement efficiency, and reduced measurement errors caused by coordinate measuring machines and other measurement methods, making the measurement of the parallelism of the reference plane more accurate and the detection more efficient.

[0005] To address the problems existing in the prior art, the technical solution of the present invention is: a method for measuring the parallelism of a reference plane, characterized in that: the steps of the measurement method are as follows:

[0006] 1) Place the fixture base on the measuring platform, position it using the locating pin, and install the support screws on the fixture base;

[0007] 2) Install the part with the reference plane facing up. Place the part hole 2 and the part hole 1 on the positioning pin and make the lower right positioning surface of the part fit with the upper positioning surface of the fixture base. Adjust the height of the support screw so that the upper end of the support screw is in slight contact with the outer circle of the part.

[0008] 3) Place the dial indicator head on the reference plane of the part and check the flatness of the reference plane along the test track. Based on the display of the indicator needle along the test track, adjust the height of the support screw to make the reference plane level within 0.005 mm. That is, after the dial indicator measures along the test track of the reference plane, the indicator needle fluctuation should be ≤0.005 mm.

[0009] 4) Tighten the upper right end face of the part with the clamping nut to fix the part on the fixture base. Use a lever dial indicator to re-inspect the flatness of the reference plane. Observe the dial indicator needle fluctuation display ≤0.005mm to ensure that the reference plane does not change after the clamping nut is installed.

[0010] 5) Place the dial indicator head on the second plane to be measured, and measure the parallelism of the second plane to the reference plane. The dial indicator measures along the second test track and observes the pointer indication. The fluctuation range of the pointer along the second test track is the parallelism of the second plane to the reference plane.

[0011] 6) Reverse the dial indicator and place it on the plane being measured. Measure the parallelism between the plane being measured and a pair of reference planes. The dial indicator is used to measure along the third measurement track. Observe the pointer indication. The fluctuation range of the pointer along the third measurement track is the parallelism between the plane being measured and a pair of reference planes.

[0012] Furthermore, the fixture base is shaped like a "7", with threaded hole one and threaded hole two respectively provided on the two stepped surfaces. A support screw is provided on threaded hole one, and a positioning pin is provided on threaded hole two.

[0013] Compared with the prior art, the advantages of the present invention are as follows:

[0014] 1) This invention uses a clamp base to complete the measurement. The clamp base has a simple structure and is easy to install and use.

[0015] 2) When installing parts according to the present invention, the reference plane of the parts faces upward, and the second part hole and the first part hole are installed on the positioning pin in sequence. The lower positioning surface of the parts fits with the upper positioning surface of the fixture base, making the parts installation simple and quick.

[0016] 3) This invention uses a support screw to manually adjust the support height. By rotating the screw, the screw can move up and down in a direction perpendicular to the base. The upper end of the support screw fits against the outer circle of the part, thereby adjusting the support height of the tail of the part. After measuring along the detection trajectory of the lever dial indicator on the reference plane, the needle fluctuation is ≤0.005mm, which meets the measurement requirements.

[0017] 4) The present invention uses a clamping nut to fix the part. Since the lower end of the clamping nut is in contact with the upper end plane of the part, the nut is tightened manually. The part can be fixed with a small clamping force and has no significant impact on the deformation of the part.

[0018] 5) When measuring parallelism to a reference, coordinate measuring machine (CMM) or dial indicator measurement is generally used. For CMM, a reference plane needs to be established by sampling points for each part, and then the measured plane is established by sampling points again. The parallelism to the reference is evaluated by software fitting. Due to the different sampling points for each part, CMM measurement and evaluation take a long time. For dial indicator measurement, the placement of the part is critical; it is impossible to accurately establish a reference plane manually, and therefore, it is impossible to accurately measure the parallelism to the reference. In this invention, after fixing the part, steps 1 to 4 are used to install the part on the measuring fixture. A measurement reference can be quickly and accurately established using support screws. Then, a dial indicator is used to measure the measured plane 1 and the measured plane 2. The dial indicator measures along detection tracks 2 and 3. The fluctuation range of the indicator needle along the measurement tracks represents the parallelism of the measured plane 1 and the measured plane 2 to the reference plane. The method described in this invention is accurate and reliable, and can significantly improve the efficiency of part inspection. Attached Figure Description

[0019] Figure 1 This is an exploded view of the fixture and parts of the present invention;

[0020] Figure 2 yes Figure 1 A combination diagram;

[0021] Figure 3 This is a schematic diagram of establishing a reference plane;

[0022] Figure 4 It is the parallelism of the measured plane to the reference plane;

[0023] Figure 5 It is the parallelism between the measured plane and a pair of reference planes;

[0024] Explanation of reference numerals in the attached drawings: 1-Clamp base, 2-Threaded hole two, 3-Positioning pin, 4-Clamping nut, 5-Threaded hole one, 6-Support screw, 7-Part, 8-Part hole one, 9-Part hole two, 10-Reference plane, 11-Measured plane one, 12-Measured plane two, 13-Lever dial indicator, 14-Detection trajectory one (detection trajectory of reference plane 10), 15-Detection trajectory two (detection trajectory of measured plane two 12), 16-Detection trajectory three (detection trajectory of measured plane one 11). Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the 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 merely illustrative and not intended to limit the invention.

[0026] The fixture base used in the method for measuring the parallelism of a reference plane according to the present invention is a "7" type fixture base 1. Threaded holes 5 and 2 are respectively provided on the two stepped surfaces of the "7" type. A support screw 6 is provided on the threaded hole 5, and a positioning pin 3 is provided on the threaded hole 2.

[0027] The steps of a method for measuring the parallelism of a reference plane are as follows:

[0028] 1. Place the fixture base 1 on the measuring platform, install the support screw 6, and install the support screw 6 in the threaded hole 5 of the fixture base 1; install the positioning pin 3, and install the positioning pin 3 in the threaded hole 2 of the fixture base 1.

[0029] 2. Install part 7 with the reference plane 10 of part 7 facing upwards. Then, put part hole 2 9 and part hole 1 8 onto the positioning pin 3 in sequence, and make the lower right positioning surface of part 7 fit with the upper positioning surface of the fixture base.

[0030] 3. Adjust the height of the support screw 6 so that the upper end of the support screw 6 is in slight contact with the outer circle of the part 7. Place the dial indicator 13 on the reference plane 10 of the part and check the flatness of the reference plane along the detection trajectory 14. Based on the display of the dial indicator along the detection trajectory 14, adjust the height of the support screw 6 again so that the reference plane is leveled within 0.005 mm, that is: after the dial indicator measures along the detection trajectory 14 of the reference plane, the dial indicator fluctuation is ≤0.005 mm.

[0031] 4. Install the clamping nut 4 to fix part 7 on the fixture base 1. After part 7 is fixed, use the lever dial indicator 13 to re-inspect the flatness of the reference plane 10. Observe the needle fluctuation display ≤0.005mm to ensure that the reference plane 10 does not change after the clamping nut 4 is installed.

[0032] 5. After part 7 is fixed, begin measuring the parallelism between the measured plane 2 12 and the reference plane 10. Place the dial indicator 13 on the measured plane 2 12, and measure along the measurement trajectory 2 15. Observe the indicator needle. The fluctuation range of the needle along the measurement trajectory 2 15 is the parallelism between the measured plane 2 12 and the reference plane 10.

[0033] 6) Method for measuring the parallelism between the measured plane 11 and the reference plane 10: Reverse the dial indicator 13 and place it on the measured plane 11. The dial indicator 13 is then used to measure along the measurement trajectory 3 16. Observe the pointer indication. The fluctuation range of the pointer along the measurement trajectory 3 16 is the parallelism between the measured plane 11 and the reference plane 10.

[0034] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for measuring the parallelism of a reference plane, characterized in that: The steps of the measurement method are as follows: 1) Place the fixture base (1) on the measuring platform, position it by the positioning pin (3), and install the support screw (6) on the fixture base (1); 2) Install part (7), with the reference plane (10) of part (7) facing upward, put part hole 2 (9) and part hole 1 (8) of part (7) onto the positioning pin (3), and make the lower right positioning surface of part (7) fit with the upper positioning surface of the fixture base (1), adjust the height of the support screw (6) so that the upper end of the support screw (6) is in slight contact with the outer circle of part (7); 3) Place the dial indicator (13) on the reference plane (10) of the part and check the flatness of the reference plane along the first detection track (14). Adjust the height of the support screw (6) according to the display of the dial indicator along the first detection track (14) so ​​that the reference plane is leveled within 0.005 mm. That is, after the dial indicator measures along the first detection track (14) of the reference plane, the dial indicator shows a fluctuation of ≤0.005 mm. 4) Press the upper right end face of part (7) with the clamping nut (4) to fix part (7) on the fixture base (1). Use a lever dial indicator (13) to re-inspect the flatness of the reference plane (10). Observe the dial indicator needle fluctuation display ≤0.005mm to ensure that the reference plane (10) does not change after the clamping nut (4) is installed. 5) Place the dial indicator (13) on the plane to be measured (12) and measure the parallelism of the plane to be measured (12) to the reference plane (10). The dial indicator (13) measures along the detection trajectory (15) and observe the pointer indication. The fluctuation range of the pointer along the measurement trajectory (15) is the parallelism of the plane to be measured (12) to the reference plane (10). 6) Reverse the dial indicator (13) and place it on the measured plane (11). Measure the parallelism of the measured plane (11) to the reference plane (10). The dial indicator (13) is measured along the test track (16). Observe the pointer indication. The fluctuation range of the pointer along the test track (16) is the parallelism of the measured plane (11) to the reference plane (10).

2. The fixture base used in the method for measuring the parallelism of a reference plane according to claim 1, characterized in that: The fixture base (1) is "7" shaped, with threaded hole one (5) and threaded hole two (2) respectively provided on the two stepped surfaces. A support screw (6) is provided on threaded hole one (5), and a positioning pin (3) is provided on threaded hole two (2).

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