[Ke...] Posted February 14, 2020 Share Posted February 14, 2020 Task: Measure the pitch diameter of 1 "Good" sample part (no issues with performance), and compare to a "Suspect" sample part (meets print specifications, but has issues with performance). Notes: I do not have a probe size that matches the Pin Diameter required for Over-Pin (3-wire) measurements, so I am using the probe diameter that is closest to the required Pin Diameter. Initial thought: 1- Measure the pitch diameter using a cylinder, with a self-centering helical path (No Stylus Radius Correction) 2- Recall measured points into a 3D Curve(No Stylus Radius Correction) 3- Export measured Actual as VDA file (Actuals + Normal Vectors; No Deviations??, Center Points) 4- In new program: Recall the Actuals as Nominals to measure I'm having a hard time getting the Nominal points to be identical to the Actual results. Has anyone had experience doing this type of evaluation? Link to comment Share on other sites More sharing options...
[Jo...] Posted February 14, 2020 Share Posted February 14, 2020 If you are referring to thread, there are a lot of assumptions made when using pin over wire. It doesn't account for thread angle ,symmetry, pitch, or root clearance. First thing I would do is put on comparator if external and look at them. I had an instance where wrong thread insert was used, and pitch diameter could be met but part was not right. Another instance when lead was rounded off in cnc program and the pitch error finally accumulated at the fourth revolution and thread gage would stop. That parts would be "good" over wires or using gagemaker measurement. Link to comment Share on other sites More sharing options...
[Ma...] Posted February 14, 2020 Share Posted February 14, 2020 Why work so hard? Why not just measure self centering points in a single plane and recall to a circle? You can measure multiple circles to cover the face width of the gear. The nominal values for your circle measurements would have to be recalculated to account for the difference in diameter between your probe and the specified measuring pins. Also, keep in mind that if you have an odd number of teeth the distance specified for diameter over pins is less than double the radius of the circle you measure on the CMM because the chordal distance doesn't pass through the center point of the gear. Unless your part is a difficult configuration or you don't have the correct gages, it may be easier and more accurate to just measure the dimension over actual pins without the CMM. Link to comment Share on other sites More sharing options...
[Ma...] Posted February 14, 2020 Share Posted February 14, 2020 I was assuming the part was a gear. 😮 Link to comment Share on other sites More sharing options...
[Ke...] Posted February 14, 2020 Author Share Posted February 14, 2020 Please sign in to view this quote. I didn't specify, but totally measuring a screw 😃 Link to comment Share on other sites More sharing options...
[Ke...] Posted February 14, 2020 Author Share Posted February 14, 2020 Please sign in to view this quote. Looks good on the comparator, too. Right now, I'm exporting the "Good" & "Suspect" samples in VDA, and they are trying to pull them into CAD, to compare them. I'm still trying to define a "Nominal" spline, and do a direct comparison on the CMM. I may have to resort to calling the genius' @ Zeiss. Link to comment Share on other sites More sharing options...
[Jo...] Posted February 14, 2020 Share Posted February 14, 2020 What diameter and type of thread ? Could it be a form issue ? Link to comment Share on other sites More sharing options...
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