my circles arnt round

[seonhog]

when milling circles with my 1996 fadal 4020 in the top and bottom there are flat spots like something is wrong with my y axis it has been getting worse started with a small bump or line you could barely feel but is now worse and my machine alarmed out and now my y axis when homed out is about half an inch off!

[Delw]

You need to tune your drives, Fadals always had a problem with perfectly round holes. Roundness of about .001-.002 is normal.
This is providing your using the proper endmill for the material your cutting.
How big of a hole are you circular interpulating? what size endmil? what type of material.

does your y axis alarm out when cutting a straight line or do you have a weird finish when feeding in the y axis?
I am guessing the alarm is a seperate issue as well as your home being off.


Delw

[seonhog]

it doesnt seem to matter hole size just tried doing a 2inch hole with a half inch endmill in 1/4 inch steel and it looks more like a funny egg!

[S Woods]

Are you by any chance using a new or different file for posting? I had a similar issue a few years ago and needed to tweak the file I was using to post.

[Neal]

The issue could be :
1. Servo tuning
2. Resolver (DC) Encoder (AC)
3. Loose Gibbs and/or Straps
4. Weak amplifier
5. Weak motor

Any combination of the above can cause the axes to not be syncronized therefore producing a bad result.
Check the electronic and mechanical adjustments and then re-test.

Neal

[Delw]

Call up the program O5815 if you dont have it in there type in ta,7

this program will allow you to tune the amps while the machine is running,
look at the X Y and Z following errors when the program is running they should all read the same in both positive and negitive numbers.
if they all read the same then your drives are tuned. if they dont you will need to tune them.
Heres a thread that May help you there is a picture on what pots get tuned also.
I have a few more problems that we were disscusng in that thread so dont worry about them only the tuneing first

Some problem I need to get fixed.

make sure you dont have any fixtures or tools in the way when running this program.

[mniadna]

Backlash should also be checked. After you do the AMP Tune, you should also do the Angle Test. This is done to sync your X and Y closer than can be achieved during the AMP Tune.
I agree with Delw! The closest I could get my machine with DC motors was within .001" on average. That was with a tuning, replacing, adjusting, some more tuning, some cursing, some more replacing, some more cursing, and some more tuning.

[metalworkz]

I don't know about Fadals, but my small mill had a similar problem and it was a lose motor connector. Connector gives enough at the 90º intervals to cause flat spots and then grips enough to drive the axis.