Verifying backlash master


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Hello all. We have a machine that checks plunging force and backlash on CV joints by clamping around the outsides of the joint while having an expandable collet connected to a load cell come up through the middle and engage. It then plunges up and down 2-3 times and collects the measurement data. It then twists side to side to measure the backlash in the joint which is measured by a long bar that interacts with an LVDT probe to measure that distance. This machine came with a backlash master that you set in the machine and let it clamp, and then the collet comes up through the middle and engages, and then twists. The master has built in clearance that should match the backlash result of the machine. Some of the issues I am having are:

1) Because we dont know of a way to measure this, we have been having to send it overseas to get it verified by the manufacturer for annual calibration, and that process takes up to 2 months.

2) The company overseas is using the same machine that we have here to verify the master. Imagine the confusion when you see that machine listed as a reference standard, and its the same machine you have on your production floor.

3) The results from the company's report come out in degrees (0.25° to be exact). Unsure how to measure this.

After looking back through the calibration certificates, it looks like the dimensions and tolerances kept moving. My guess is that this could essentially be just an ROV calibration because you are trying to match a known value from the master to the machine. If the value is way out, we will know that something is likely wrong with the machine causing the backlash to be off and investigate accordingly. Having said all this, I have attached a snippet to give an idea of what it looks like and how the clearance is present in the master. I am looking for a way to measure this and still be conforming to ISO 17025 but not having to keep shipping it overseas. If I have a way I can define and use any sort of calibrated reference standard in house to achieve this measurement, I should be able to get by, but the question We dont get the machine itself "calibrated" but we do check the plunge force and backlash with calibrated masters. Anyone have any ideas?


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