PCNC1100 Chatter When Machining Along X Axis - Loose Table?

Mill
1

Ran into a problem today with my PCNC1100. I’ve seen various threads and various theories around the web on what can cause this, but I figured instead of chasing down those rabbit holes, I’d bring it here where I could get some expert opinions.

Background

I have an 1100S3 that’s got quite a bit of run time on it. I think it’s a Circa-2016’ish era model. Has been running like a champ since then.

I once had a similar issue to this that ended up requiring a gib adjustment, but tried that again here today, and didn’t seem to do the trick.

Symptoms

When milling straight across the X-axis, I get chatter on 6061. Using a 3 Flute 0.375" Endmill running feeds and speeds that are pretty conservative and have generally worked before in the past. In fact, they still work fine as long as the motion is in Y, or includes helical motion, etc. It’s the straight cut along X that causes the grief.

Observations

This happened to me a couple years back, and it ended up being that my X gib was a bit sloppy, probably just from wear and tear. I tightened it up using the documented procedure and seemed to be back in business.

I went back to that today, and I found that I did have very little lost motion in X, so I suspected it might be the case again. I tightened things up to have around 0.001" in lost motion (which is a bit tighter than I ran before) and it didn’t seem to help.

The other thing I noticed, which I think is probably significant, is that with an indicator on, I can grab the table and move it around 0.0015" in Y by pushing and pulling on it. It seems tighter in X - I didn’t seem to be able to move the needle appreciably in the X axis by hand.

Questions

  1. Is it normal for the table to move that much? Obviously the whole system has to float a little for things to be able to move at all, but is that excessive? I feel like that’s probably enough slop to allow the cutter to oscillate/chatter under load.

  2. If so, other than the gibs, what coupling might be lose which would allow the table to move that much, and how can it be accessed?

Thanks for your help!

2

Generally, if you have chatter in a single direction, I would check the opposite gib. So, in this case, Y. Gib/ACB Adjustment and Backlash Compensation

I would probably look at opening a ticket, if going through this document doesn’t fix things for you: Tormach Customer Service Portal