Temp Control Do you use it or Not?

[Paul Sarrach]

If so, what type of tolerances are you holding.

[djayne]

We've seen changes of up to .006mm holding +/-0.013mm tolerances on parts we run through 243° parts washer. (Ferris parts)

[STANLEY]

I don't know to much about it. Can someone explain it.

[RussL]

We have just had a new machine installed,
we have been told we must use it on the new machine.
Temp Comp does not just compensate for temperature of part,
it compensates for temperature of machine.
Our new machine is calibrated with it on, we must use it that way.

On the old machines, we leave it off.

[Johnson]

using temp comp

We use it on all the CMMs here. More because of the room changing temp a few degrees. I do not put one on the part but have a pyrometer to check that it is stable to the room environment before I run it. Tolerance ranges from +/-.60mm to +/-.007mm..

My understanding of it though is that it is not updating every second. Not sure how often it checks the temp of all the axis'.

[cmmguy]

I wouldn't call temp comp useless, but rather missused. It is not for temperature unstable parts such as parts just out of a washer or just brought into the lab.

There are usually two places where temp comp is applied. One is to the machine and the second is to the part. If you are in a temperature stable and temperature normal (68deg) room with Temperature stable parts, you need neither.

If your cmm is temp comped it has to be live and it had to have been calibrated with it turned on. Most CMMs with temp comp on the cmm have it turned on all of the time. Your cmm is comped back to 68deg.

When you move from temp normal is where it kicks in. Your cmm is comping itself back to normal. That is why temp stable is critical for it to work.

Then you get to the part. the part probe is to determine the temp of the part, I guess if the part is stable(and it should be) you could put the probe anywhere and not on the part. The only reason for the temp comping the part is because the part has different expansion rates from the cmm and the temp comp command should ask for the coeficient of expansion because the cmm at 75deg and an aluminum part at 75deg will check differently at 69deg. due to the different rate of change.

If used on plastic parts then you need to look up the coefficient for your material.

[Paul Sarrach]

Well put Guy. I wonder If any of the users ever did a co-alation study using the Probe. The things that make you go HMMMMMMMMm!