Mach 3 has backlash compensation available but it rarely gets used by anyone.
I tried it once before, but it's behavior was so odd that I stopped.
A lot of starting and stopping and slow movement.
I only have about .004 - .006 backlash but it's enough to make circular pockets
eggshaped.
I need to insert bearings into the holes so I need them to actually be round.
I searched and read through a bunch threads on the Mach 3 forum and found a couple of tips
that solved the problem.
Basically just set the Backlash Speed % of Max to 100% and Shuttle Accel to .005. Simple.
Now it runs without hardly any hint that the compensation is active. But work it does.
The pic below shows how eggshaped the pocket ran without comp active and then again
with it active.
NOTE: I only have .004-.006 backlash normally but to demonstrate it for the video
I loosened the ballnut stopblocks to increase the backlash to almost .020 so it would
show up better.
Under my normal operating conditions the comp is almost imperceptible.
I put together a video to show the process here on Youtube.
Hoss

Hoss attached the following image(s):

Awesome vid Hoss. You've just added the finishing touch to my accuracy tweaking with this excellent description of backlash compensation. Cut a small part today over and over, tweaking the settings each time and got a perfect part on my 6th attempt. I'm also doing your "circle" analysis to double check the backlash values I have.

Question: How does your Z backlash compensation compare to your X and Y values? I'm guestimating mine is about half based on today’s trials and visual inspection.

I've read a few posts on other forums from self appointed "experts" on the backlash comp subject.
They give a lot of hot air about why comp DOESN'T work, at least why THEY think it doesn't work.
I wasn't satisfied and did the research myself.
Zero mechanical backlash would be the ideal situation, but it may not be possible with some machines.
I've shown that Mach 3's comp DOES eliminate nearly all the side effects of backlash.
Perfectly? no, but damn close. A hell of a lot better than not using it.
As the pic shows above, the circle is still not perfectly round but nearly.
But even a machine with zero mechanical backlash won't make a perfect circle, that's what boring heads are for.
Hoss

Hey Hoss, I to have the backlash comp in operation and be far your right it makes a big differents for sure. Keep the video come, great job. Oh kind of off topic but i see you have made your own end mill tool holders, would these be something your would sell. I would like to have 3 of them (1/4, 3/8, 1/2) these would do me fine. Also would you have any off those spring washers you used in your power draw bar. I have been looking here in Ontario and no luck. Again great projects and videos.

Mike

Hoss, thanks for the heads up on the tool holders. The spring washers issue i have is McMaster Carr does not ship to Ontario Canada, I'm wondering if you can help a fellow X2 owner out and pick some up for me and i will pay you for them a long with the Shipping of course.

PS, I got my machine up and running now, i can ses i will be extenting the Y in the near future. I'm getting under 4 inches of travel in the Y. That is not enought i would like 7 - 8 now that would be great. Any ways again thanks for all you do for the hobby.

Mike