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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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  • you will likely see a more significant time savings by increasing movespeed and touchspeed.
    do a study using the cal sphere.
    write a routine that has assigns for movespeed, touchspeed prehit and retract distances.
    then loop the routine by altering one of the assigns within the loop.
    IE: touchspeed loop study

    assign/touchsppedvalue= 2
    measure circle of cal sphere at standard touch speed.
    loop starts
    assign touchspeedvalue = touchspeedvalue+0.1
    measure circle
    loop until circle stddev is beyond your reproducibility limits.
    this determines your fastest permissible touchspeed for that probe.

    you can do the same for prehit/retract distance as well as other variables.

    in my humble opinion movespeed should always be at max, unless your programs, fixture methods, or operators are shoddy.
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  • you will likely see a more significant time savings by increasing movespeed and touchspeed.
    do a study using the cal sphere.
    write a routine that has assigns for movespeed, touchspeed prehit and retract distances.
    then loop the routine by altering one of the assigns within the loop.
    IE: touchspeed loop study

    assign/touchsppedvalue= 2
    measure circle of cal sphere at standard touch speed.
    loop starts
    assign touchspeedvalue = touchspeedvalue+0.1
    measure circle
    loop until circle stddev is beyond your reproducibility limits.
    this determines your fastest permissible touchspeed for that probe.

    you can do the same for prehit/retract distance as well as other variables.

    in my humble opinion movespeed should always be at max, unless your programs, fixture methods, or operators are shoddy.
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