CMM Health

I am currently doing my "is the CMM still happy?" checks on the Global.

STEP 1: Using the most common probe build, I calibrate 9 angles, then check the cal-sphere using those same 9 angles, 10 times, and plot it on a run chart. (My build is roughly 6" from pivot of head to probe tip)
STEP 2: Using a home-made ball-bar, I check 29 positions on the machine (I have a map of the locations that I use)
STEP 3: Using a home-made step bar, I check the entire length in X & Y (using a cumulative method, not 24" over and over and over) as well as 24" in Z, every inch
STEP 4: I check the actual table of the machine, 2" grid (almost 1900 points) and report out the Z deviation as well as over-all flatness.

You may think that the table check is a waste of time, but it is not. If the table and ways were all "perfect" to begin with, it will all check "zero", but, if you your table isn't properly supported and correctly supported, that rock will change shape over time. This change WILL show up with this check, and the deviations will be greater for a taller (more Z travel) machine than for a shorter machine.

I actually "fixed" a small amount of error on the Validator when it got moved to the new lab and set back up by getting the support cans placed "more better" than they were before the move. The Validator is a 4-point support for the bridge, so even easier for table issues to show up in a 'flatness' check. I reduced roughly 0.0008" of droop in the right-rear corner of the machine down to 0.0004" over the course of 3 years of the new support. I don't know if it will get any better over the next few years or not. Yes, it takes years for the rock to change shape.

PH10MQ, TP20 STD FORCE, 6" total length results:

Table flatness: +0.00051 to -0.00071 (0.00122 'flatness')
Ball Bar: +0.00020 to -0.00024
(all values are in inch)
starting the step bar runs now

Table flatness: +0.00051 to -0.00071 (0.00122 'flatness')
Ball Bar: +0.00020 to -0.00024
(all values are in inch)
starting the step bar runs now