Position Error Readout Ranges

[jon_fallon]

What are the normal range of position error values for a circular interpolation about a 1.00" diameter boss at 10 ipm?

When the part is measured, there is a difference in circularity between 5ipm & 15ipm. Is there a test that can be performed to determine when the ball screws need to be replaced?

Thanks in advance.

[Neal]

It sounds like you need to have a Ballbar test run. It is a great diagnostic tool. The issues could be machine level, backlash, couplers, machine squareness, etc... or any combination of the above.

Neal

[jon_fallon]

A Ballbar test would be in order, and am investigating getting it done.

But in the meantime, what type of position error is normal while the circulation interpolation is being run? The x & y readout error varies as it traverses the circular path from a low of near zero to a high of 30-40 at the maximum velocity of each axis. For a new machine, what values would one expect to encounter and would they be speed dependent?

Thanks.

[Neal]

Assuming that EVERYTHING is up to snuff with mechanical and electronics settings and adjustments, you should have location accuracy or plus/minus .0002".
Circularity will depend strictly on these adjustments as well as tool and fixture influences.

Neal

[alex gitzel]

You will want to check the gibs on x,y,and z any of these being loose can effect the circle accuracy at different speeds.also check backlash,and amp tune.level+ squareness can also have an effect.

[jon_fallon]

There were a few interesting papers on the ball bar test on the web (http://www.machinetoolhelp.com/Preve...ranalysis.html) that indicates potential error sources given a ball bar test. A quote was received for a new Renishaw Ballbar unit, but is out of my price range and will look at putting something together in the shop to measure and record the circularity.

Are there any procedures on how to set the servo gain? Procedures were located for adjusting the gibs, checking backlash and checking squareness.

Thanks,

[Delw]

Jon
fadal tech docs are right here.
http://www.fadalcnc.com/
they have everything in the books almost.
you can call Fadal direct as well and they will help you out and sometimes fax your Prints and pages on stuff you may need.