How much precision is enough ?

[scyan]

Hey guys, being new to this, I have a question.

We have corrected the backlash that was plaguing our machine and came out with this mechanical backlash
X 0.0015
Y 0.0022
Z 0.0020

We corrected it through mach 3 but I Was wondering how this mechanical backlash stands up to the competition... ?

Also, when doing a circle now.. the fluctuation is always within 0.001 of an inch, plus or minus depending on where we take the reading. Should it be better than that ?

Thank !!

[SyilAmerica]

You should be able to get that deviation to within .0005". Sounds like you are getting closer, just a little more tuning.

Backlash looks ok, but I'd check it again. I'm going to bet it's less than that.

[SyilAmerica]

If you compare the backlash to much anything else, you'll have a good sized grin.

[Syil_Australia]

Hello..

It may be worth checking your Axis motor tuning to ensure that the Steps/unit are absolutely correct down to the 0.001". If either axis is not set correctly you will have minor errors that could appear as backlash. Consult the Mach3 manual for the procedure.


cheers

Frans
Syil Australia

[InspirationTool]

Sycan, coming from a mini mill style machine with acme screws, those seems like pretty good numbers.

Question though.... is this on a Syil with the double ballnuts? I would think you could get the mechanical backlash below .0005"?

Also, what did you do to adjust the backlash? Did you have to monkey with the axis bearing pre-load?

Thanks!

-Jeff

[scyan]

No, our mechanical backlash was pretty bad at
X 0.015, Y 0.0218, Z 0.020

This is with the backlash adjustemnts done in mach 3...

I dont think we can adjust the preload on the nuts, maybe Richard or someone else can correct me. As thats what i would like to do to get the best out of it.. Then finetune with mach 3...

Scy

[InspirationTool]

Scyan....

Something is *wrong* with those numbers.

It would seem to me that the problem would be in the ball nuts system or the end thrust bearings. Check your couplings as well.

-Jeff

[SyilAmerica]

Something is very wrong with those measurements. We measure every machine before it leaves. We haven't had any over .0002" on the X and Y axis.

Maybe you could tell us how you are measuring?

Have you made sure your steps are correct in your motor tuning? (referring to Frans)

Everything is preloaded. No adjustment is needed.

[InspirationTool]

Sycan...

Are you testing with a dial or test indicator?

-Jeff

[scyan]

To my knowledge its a dial, what is a test indicator ?

Also, just to make things clear. When wanting to test mechanical backlash, one must remove all the numbers in mach 3 (backlash) and make sure backlash is not enabled or do i leave backlash enabled but at 0 ?

And then, where exactly do you put the dial indicator ? We have a magnetic base and an arm to locate it... Do you test backlash on the spindle vs the tables ?

Thanks !

[InspirationTool]

A "test" indicator has a small dial and a small swinging arm with a small amount of travel.

A "dial" indicator has a sliding arm and a large dial and large travel. The test indicator is generally more accurate.

I use a magnetic base to attach the indicator to the table, and indicate against the head of the mill.

Turn off backlash compensation, and then jog by .001" amounts. Count the number of jogs required to get the dial to move the other way when switching directions.

-Jeff

[david_geng]

Sycan, have you sorted out the blacklash? Which part casued this problem?