Probe keep dying

[Ralph Barrier]

I am checking the diameter of a steel ring, 22" in diameter and around .5 thick.
I am using a B&S One with a TP20 and a 4mm x 10mm long shank. I am doing a
DCC alignment taking 4 hits on the surface and then taking 4 hits around a section of the diameter going .147 below Z0to get my location. Then I am running the auto circle to take 10 hits around diameter.

I ran this 6 times yesterday with no problem. I ran another one this morning. On my second piece today, when I was doing the DCC circle hits, the probe did not beep when it hit the surface, but wanted to keep on going. I stopped it and backed off and touch the probe with my finger. It was dead. I manually went up to 4" above and it worked. I came down to 0 and touched it with my finger and also down to -.15. It seemed to work ok, but when I went in an tried to touch the part, it did not work again.

Can any one explain why it worked on 7 parts then decided to quit working?

I have the part flat on the table and I thought at first I might be coming down to low, but it did work before.

Any help would be appreciated. Thanks.

[craiger_ny]

Are you holding it with a maganet? Or is the part maganatized (if it is off the grinder it may very well be).

Craig

[JamesMannes]

Just a quick thought..
Have you shutdown totally and re-booted and re-homed the machine? Could be the answer.

[Wes Cisco]

WCS

It sure sounds like a magnetized part to me.

[Ralph Barrier]

Thanks for the replies.

I started thinking about it being magnetized, so I went anc checked. And guess what? Part of the ring seems to be. Not the whole thing but just so happens the area that I was checking was.
Would using a longer probe shank help, say 20mm or more? It doesn't seem to be a real strong magnetization. How sensitive is the probe head to such magnetic parts?

[#2#]

Thanks for the replies.

I started thinking about it being magnetized, so I went anc checked. And guess what? Part of the ring seems to be. Not the whole thing but just so happens the area that I was checking was.
Would using a longer probe shank help, say 20mm or more? It doesn't seem to be a real strong magnetization. How sensitive is the probe head to such magnetic parts?

A longer tip might help but I'd try to de-magnetize the part first.

[Wes Cisco]

WGS

To solve the problem you might need a 100mm tip or more, depending on how strongly the part is magnetized. Do you have a tp2 you could use for this job? If you are going to try the longer tip route, I would start with 50mm and if that doesn't do the trick I would go with 100mm. By the way, Renishaw say 50mm is max for tp20 but I use a 1.5x90 with 70mm of that being graphite and a 5x100 all graphite on extended force modules and they work ok, but you have to move slow or you get airtriggers out the wazoo. (technical term) HTH

[#2#]

WGS

I would start with 50mm and...

Or you could position the probe high above your part and put in a move point. Then position the probe close to the part (where it won't trigger) and execute the move point with the speed set very very low. Then gently tap the probe with a pencil as it moves up until it registers a hit. Distance from tp20 module to part is about how long a probe you would need.

[djayne]

Thanks for the replies.

I started thinking about it being magnetized, so I went anc checked. And guess what? Part of the ring seems to be. Not the whole thing but just so happens the area that I was checking was.
Would using a longer probe shank help, say 20mm or more? It doesn't seem to be a real strong magnetization. How sensitive is the probe head to such magnetic parts?

Move it up 20mm and see if the probe takes hits.

[dwade]

You can also demag your probe module and your probe set up. If you have a demag unit, just use it on your parts before you run them on the CMM.

[jon_dav_uk]

We had this problem all the time with parts being magnetized in certain areas, now use non inhibit TP20's. We service exchanged all out standard TP20's for a minimal fee and now have no problems