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Change in accuracy from reducing pre-hit distance?

I’ve been trying to reduce CMM runtime in our QC department and I’ve found that using fly mode and reducing the pre-hit/retract distance by half, it cuts an average of 13% off the runtime for our product. I’m trying to make this a standard, so I want to show my time studies to management. Before I do, I wanted to make sure there were not any changes in accuracy.

From what I know, the only downfall to shortening the pre-hit distance from .1 to .05 is if measuring a non-consistent part like a cast part, the probe might move to close before taking a hit and throw an error when it touches the part. I also know it shortens the distance it will search past the theoretical point, but that can be adjusted by setting the check distance, right? So, is there any other reason you wouldn’t want to shorten the pre-hit distance?
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  • Just another thing to consider. The type of probe you use can be a factor for the prehit distance. A touch trigger probe like a TP20 will register the hit while approaching the part, so a little distance is needed to reach the proper speed and stabilize. However, analog probes (like the SP25) touch the part and then slowly back off until the trigger force is reached before registering the hit then retracting at full speed. For those probes the prehit distance doesn't matter for accuracy - unless you use Fastprobemode which makes it take hits on the approach, like a touch trigger probe.
  • Thanks! All of our current probes are LSP’s. We don’t use anything else.
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