??The method of the three-dimensional measurement inspection fixture is different from the measurement of stamping parts. We need to use the CAD data of the corresponding product of the inspection fixture, that is, the product's digital model as a standard to compare and measure the inspection fixture. This is also a necessary condition for the final acceptance of the inspection fixture. Coordinate measurement for stamping parts
It is more difficult to measure. Generally, we will not use the processing digital model of the fixture to verify the fixture.
Below we take the upper right cover test fixture of the side member of a certain model as an example:
1. Establishing coordinate system
Place the fixture on the measuring machine platform and fix it. Manually measure three circles. Operate the software according to the relationship between the direction of the workpiece coordinate system and the machine coordinate system of the measuring machine. Use the center of circle 2 as the origin of the workpiece coordinate system To complete the establishment of the coordinate system.
2.Measurement method of positioning hole
The fixture usually has two positioning holes, which are the main positioning hole and the auxiliary positioning hole, corresponding to a round pin and an edge pin, and these two positioning holes are sunken holes, because we use the product model, and The actual fixture is different. In order for the measuring machine to measure,
We must set the software, the specific operation is: insert → feature → automatic → circle (the difference from measuring stamping parts is to make up the thickness based on the actual situation based on the theoretical value).
3, the measurement method of the mounting hole
The measurement method of the mounting hole is almost the same as the positioning hole, except that the sleeve surface of the mounting hole is basically the same as the surface of the fixture body, so the depth value can be smaller.
4.Measurement method of clamping block
The clamping block corresponds to the RPS point of the stamped part, and at the same time, it fits with the lower surface of the stamped part to support the stamped part. Therefore, the theoretical value of the clamping block is also the numerical model of the lower surface of the stamped part. For theoretical positions, compensation is required in the software,
The compensation value is the material thickness of the stamping part (the material thickness of the upper right cover of the stringer is 1mm). There are two methods for PC-DMIS software to measure the clamping block, namely manual point measurement and automatic measuring point measurement by the measuring machine. The measurement method of manual point picking is to manually pick points on the surface of the clamping block. The software obtains the actual measured value and compares it with the digital model. The closest point is obtained as the theoretical point. Select the corresponding position on the digital model to generate a vector point, and then make the measuring machine run automatically to measure the corresponding position of the clamping block.
5, measuring method of profile
The profile includes the zero and five planes. PC-DMIS software can measure the zero and five planes at one time by measuring the edge points, but this method is only applicable to the zero and five planes. When the included angle of the surface is 90 °, the specific operation is as follows: Insert → Feature → Automatic → Point → Edge.
6.Measurement feature evaluation and test report
After the measurement is completed, the size of the measured element needs to be evaluated, and the content of the evaluation is different according to the element type. Generally, the hole type needs to evaluate the hole center position and the hole diameter, the vector point needs to evaluate the position and the normal deviation T, and the edge point only needs to evaluate the position deviation. The tolerance standards for Brilliance China Gage final acceptance are usually positioning holes ± 0.05mm, other holes ± 0.1mm, clamping points ± 0.1mm, and profile points ± 0.2mm.
After performing the feature evaluation according to the tolerance requirements, a final acceptance inspection report needs to be issued, and the PC-DMIS software will generate a graphical report.