Influence of pin floating on repeatability of gauge

When the part is placed on the inspection tool, because there will be a gap between the locating pin and the reference hole of the part, the hole pin floating will occur. How much impact will the hole pin floating have on the measurement of the part?

case analysis

We will take the following assembly as an example. The figure shows RPS points. We will model the features of the fixture and parts, and then select Y-direction measuring points for analysis.

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Modeling analysis

In VSA, the modeling settings are as follows. Monte Carlo algorithm will be used to simulate 5000 times of assembly, in which the diameter of the reference hole is 25.4 ± 0.1mm. The influence of the pin floating on the measuring point when the pin positioning diameter is 25.35mm, 25.3mm and 25.25mm will be evaluated respectively. At this time, the limit distribution is selected for pin assembly.

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simulation result

There will be deviation at the measuring point due to the hole pin floating. By comparison, our company adopts 25.35mm in the value of the gauge pin. The diameter of the pin varies slightly from company to company, but the final criteria are repeatability and reproducibility.

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Of course, in order to reduce the hole pin floating, tapered pin or spring pin can be used to make the parts measured in RFs state. If the part is measured in MMB state, it is necessary to evaluate whether the drawing is reasonable or not. Otherwise, it may not pass the test when making the repeatability and reproducibility of the fixture.