Tip Calibration Problems

[#2#]

B&S Excel 7-10-7, PC-DMIS 3.7MR3, PH10mq, TP20

This has happened yesterday and today. Haven't seen it before.

Both days, we started the machine up. Then, we went to calibrate the tips used in a program. Upon completion of the calibration we get the error about the std dev. exceeding limits.

Go to results file and the std. dev. is coming in around .0020 inches! So, yesterday, I tried a different probe and the same. Shut down, re-start and everything was fine (std. dev. .0001).

Today, I get the same initially (.0020) shut down, re-start and .0020 still, different probe - .0020. Different module (tp20) - .0020.

I checked to make sure the cal. sphere was defined properly - it was/is.

I created a new probe file - .0020.

Tried creating a new program - .0020.

I tried answering yes and no at various times to the sphere having been moved - .0020.

Suddenly, after switching back to original probe and original probe file - .0001. Now all seems to be good again.

Anybody got any suggestions to try next time this happens?

[bw_bob]

Delete the .0020 probe file & start over & see what happens.

[Underspec]

Clean the sphere & ruby ball real good? I had that problem once . Dimensions were way out of spec. Come to find out there was a piece of lint stuck on the ball.

[#2#]

Clean the sphere & ruby ball real good? I had that problem once . Dimensions were way out of spec. Come to find out there was a piece of lint stuck on the ball.

Forgot to mention that I did that too.

[WScmm]

Check to see if you probe is tighten. I also had this happen, but I was using small probes and if my sphere was just straight enough the shank would hit. I was also having false probe hits until I got my machine worked on. I had to have all my belts, pulleys and bearing replaced on all 3 drives. That fixed all my false hits. Hope this helps.

[Mike N.]

get a loop 10X...check for chips in the ruby or wear marks or aluminum build up

[JoeRZ]

What's the length of the stylus?

If you have stylus extension - check that...I get that same thing if I use stylus longer than 60mm - also the longer the stylus the force on the module should match.

[#2#]

Check to see if you probe is tighten. I also had this happen, but I was using small probes and if my sphere was just straight enough the shank would hit. I was also having false probe hits until I got my machine worked on. I had to have all my belts, pulleys and bearing replaced on all 3 drives. That fixed all my false hits. Hope this helps.

Good tip, I also forgot to mention that I did that.

get a loop 10X...check for chips in the ruby or wear marks or aluminum build up

Good tip, but that won't make a difference as it was giving the problem with any tip and any module attached to the tp20.

What's the length of the stylus?

If you have stylus extension - check that...I get that same thing if I use stylus longer than 60mm - also the longer the stylus the force on the module should match.

4x20mm tip w/ 30mm extension on a med. force tp20 module - but it did it with all probes I checked including a 2x20mm tip on a reg. force tp20 module.

[Gregl]

It is just one of the enhancements to pc-dimis to keep us thinking.

[JoeRZ]

Try increasing the number of probe hits on the artifact and set touch speed no more than 2%.

Then I dunno'...

[than_357]

Check that the TP20 contacts on both probe and fixed module are clean and free of chips. We had one where the lip around the fixed part was dented in towards the center. The probe would seem to seat but the dent was just enough to allow the whole thing to wobble in use.

Being cheap and flogged for budget excess- bent it out with needle nose pliers and back into repeatability.

Tom H

[rerun_lives]

I had very slight loosening of my tooling sphere in the holder once. That was very hard to spot. Tightened it back up and Bingo! Everything was Ok again. Just a thought.

[joe.sha]

I'm having the same problem with a Mistral. I've added a "warm up cycle" to my calibration programs and they are now in spec. I reckon its a worn drive belt or pulley so I've an engineer coming in next month with enough spares to build a new CMM.

[#2#]

Check that the TP20 contacts on both probe and fixed module are clean and free of chips. We had one where the lip around the fixed part was dented in towards the center. The probe would seem to seat but the dent was just enough to allow the whole thing to wobble in use.

Being cheap and flogged for budget excess- bent it out with needle nose pliers and back into repeatability.

Tom H

Good tip, I'll check that. I would guess it would be on the TP20 and not a problem with the module b/c it did it with more than one module. I will double check all of them though.

I had very slight loosening of my tooling sphere in the holder once. That was very hard to spot. Tightened it back up and Bingo! Everything was Ok again. Just a thought.

Another good suggestion. I don't think that is it due to the way my calibration sphere is constructed but I will check it anyway.

Thanks guys.

[JoeRZ]

Hey Goodluck,

Have you tried moving the artifact in a different location? there may be positioning problem in one of the machine axis in the vicinity of the artifact.