LEITZ 866 PMM MACH HOME ISSUE

[RICHIE RICH]

We have a 4 slot probe changer
We are using a B&S analog probe head
I have screwed the master sphere directly to our granite table
I have calibrated all of our probes at the same time to the master sphere
When i need to add another probe I can say that the master sphere has not moved. This is all well n good however.....................

When i need to shut down the mach and restart it.Then i restart PC "DEMONS" "o" sorry PC DMIS it homes out the pmm.Would you believe that
when I go back and measure the master sphere "which has not moved"It reports the "X" is of on average of .00230

This means if i have to calibrate any new probes they will be off to all the other probes i have calibrated by that amount

It is a waste of time to have to recalibrate all the probes again.

Any suggestions: Thanks

[Matthew D. Hoedeman]

EVERY time you home the machine, your actual home position is a little different. Not 100% sure what you have for the encoders, but on my machine, there is a little magnet on the encoder strip that triggers something in the reader head. When that triggers, it sets the home position. It will never come out exactly the same as before.

As for any ideas about adding probes, yep, I think you are bumming because if you calibrate all the probe build-ups, then the tool 'moves' from the re-home of the machine, then you only calibrate one build-up, then the relationship between the build-ups will not match, so you could NOT change probes in the middle of a program UNLESS the first thing the new probe did was to align your part, if there isn't an alignment after the change, then both build-ups HAVE to have been measured with the tool in the same place. With a new alignment, you can, like I said, go on, without the tips being calibrated to the same tool position since each probe is calibrated to itself, so if the new one re-aligns, the numbers will be good.

[Jeffrey Lovely]

Should tips be recalibrated after homing?

[Schrocknroll]

Never calibrate just a few of your angles/tips after homing an expect them to be dead nuts relative to angles/tips calibrated before homing. As Matt said no CMM rehomes perfectly. It may be only a few tenths or a few thou but it's never perfect.

So no you don't necessarily have to calibrate after homing, but just don't do a partial calibration.

If you have something extremely critical, then recalibrate even if you haven't homed, but that's another thread.

[ag162]

Just my 2 cents:
I cal the probe in the beginning of my shift, due to shutdown and temp variance. I also cal prior to any programming with a different styli. While it may not be neccessary, it's just a little cya on my part. Even if you just cal the angles you estimate using for the prg.]

A.Gore

[RICHIE RICH]

Thanks for the help

[RICHIE RICH]

By the way Matt I like your profile pic very cool

[STANLEY]

I calibrate probes used in each program daily, because of the different inspectors that use my machine on 2nd and 3rd shifts. Once a week i calibrate all my probes. I only home the machine on Monday mornings usually.

[Don Ruggieri]

What about???

You should be able to calibrate as many probes as you want, then re-home the machine. BUT, the next time you go to calibrate you would have to tell it that the sphere HAS MOVED. Now, if you start by calibrating with a known (previously calibrated) tip, the sole function here is to identify where the sphere is. Then, you can go on and calibrate the new tip(s) and it/they will be related to the old tips.

[RICHIE RICH]

thanks for the suggestion

Thanks for the suggestion Don

I just got back from our medical division and will be back on the pmm
gonna try it out sounds like it might be a winner

[John Kugler]

Do you have a program set-up just for calibration??

I have a program that I run through that calibrates everything in one shot.

Very helpful.

[Paul Sarrach]

Richie, I worked with one of the last Lietz PMM made, prior to B&S taking over the company and refusing to pay for the naming rights. That is one sweet machine. Did it not come with Quindos? I hated Quindos, but it the best software when it comes to algorythms. I wish every programmer out there gets a chance to see on of those Lietz PMM's they are defintly the Rolls Royce of CMM's. Sorry do not remember having problem with it when running Quindos. Just wanted you to know you are working with the best and some of usr are working with Pinto's and Gremlins. enjoy

[John Kugler]

Could not agree more. Ours is the Brown and Sharpe flavor, but holy man it is one sweet machine.

I hate to say it, but I could not imagine using anything else.



We have Quindos also, NOT very user friendly, but I can hack through it..

[Paul Sarrach]

I have a Arm style CMM here, There acuracy is crap compared to a Bridge stlye. But to have a air leveling, movable dove tail table, 1 axis stationary bridge, and 60000 dollars probe head that is a mini CMM in itself now that what I am talking about acuracy. And I know you have it in a 1/2 million dollar envirmentally controled Lab.

[John Kugler]

Yes sir we do. 68° year round. Except when the air takes a crap and it takes a week to get a part in. Then it hits 91°.


Yes, we stopped measuring....