[Sray]

Hey guys,
I have been running my CNC now for quite some time with no issues at all. The other day I started it up and when Homing it I noticed some high pitch whining sound coming from one/some of the motors. I was not sure what it was. I proceeded to manually move the machine around the table in all directions and at slow to rapid speeds and it seemed to work fine with no strange noises. So I setup my job and started cutting. Instantly the machine started chattering/vibrating quite violently. I immediately turned the speed all the way down to like 10% of the job speed (80 in/min). Even at 8 in/min it was chattering/vibrating, just not violently. I decided to mess around with feeds and speeds but nothing helped. At the time I was just cutting out a test piece from a 1/4 piece of plywood at a depth of .1 inches with the router at 16000 rpm and using a 1/8" straight bit (new). I have ran many jobs at much deeper depths and higher speeds with amazing success. This boggled me. While it was running I was feeling/observing/checking every single part/connection on the machine to see if I could find where it was coming from, but I couldn't.

Because I was able to move the machine manually all around the table at any speed/direction with no sign of vibration or noise I starting to think it may be a bit/collet issue. I checked the runout on the first bit I used and it came to .007". This seemed a little high. So I chucked up another new bit and that one came to .006". Then I started to think that maybe it was the Dewalt collet. I was thinking that maybe I need to upgrade to a precision grade collet but wanted to be sure it was a collet issue. Today I decided to see if the machine would vibrate even with no load. So I ran a job with no wood or bit chucked. I was going to put slight pressure on the router as it was running to see if that caused the vibration. Well as soon as I started the job it started vibrating throughout the entire movement. There does not seem to be any direction that it does not vibrate. So that tells it is not the router at all.

Next I disconnected the X/Y ballscrews from the gantry and Z axis assembly to see if maybe one/both are binding somehow. Once I disconnected I was able to easily slide the gantry and Z axis assembly back and forth. So that tells me it was not that, but I decided to run the job with them disconnected anyway just to see what is up. Well as expected the vibration started immediately. I can visibly see the ballscrews struggling/chattering (X/Y axes, not sure about Z though) accompanied by a whine that fluctuates. You can hear them struggling.

This ONLY happens while running jobs, not while manually moving around. I have done nothing what-so-ever to the machine. It literally just happened overnight. I am not sure if there is something in my g-code that could be causing this? I am using the same software (Carbide Create Pro) I always use. I do not see anything visibly wrong/going on in my cabinet.

Here is a link to a video I took. You cannot really see much in the video. I was mainly trying to capture the sound it was making. At times it almost sounds like grinding. This was taken under no load at all and disconnected from the gantry and Z axis assembly.

https://drive.google.com/file/d/1IM0...ew?usp=sharing

I have no idea even where to start. I am really hoping you guys can help and that there is a simple fix here.

Thanks

[mcphill]

Did you try an old program that worked fine before? Is it now stuttering?

[RCaffin]

Most likely (I think) your servo drive is oscillating. Have you changed ANY parameters in any of the drives recently?
Or, perish the thought, there could be a component failure in the drive in the PID section.
Or (there are many possibilities!) the coupling between the motor and the rest of the drive has become loose.
Or the motor has become loose.

That will do for a start.

Cheers
Roger

[Sray]

After much testing I think I was able to narrow the problem down to a bad 30A breaker in my shop sub-panel. I am now back up and running strong.

Thanks for jumping in and the suggestions guys! Luckily it appears to be an easy fix. Fingers Crossed!

[RCaffin]

Which only goes to show just how many causes there can be for 'problems'.
And how really difficult it can be to diagnose things when one have only half (or less) of the info one needs and would get be being there watching.

Oh well, Congrats.
Cheers
Roger

[Sray]

I wanted to jump back in and update the cause and solution.

Everything seemed to point to the breaker but the chattering came back. It turns out that it was caused by the G61 code that I added to the beginning of my files just before the chattering started. I started using G61 because once I would reach a certain speed my sharp corners would start rounding. From my research G61 was one of the options to eliminate this. Well once I realized that the chattering only happened on arcs it made me wonder if there is a connection. Apparently there is.

From my research G61 is used for exact stops which can help at higher speeds, especially at sharp turns like corners. It now makes sense why it chatters on arcs. From what I learned G61 causes an exact stop check after EVERY move the machine makes before moving onto the next move. Well an arc is made up of many nodes/moves so the machine would stop at each node causing a chattering?

Anyway, hope this helps someone else at some point.

Thanks for all the input!

[RCaffin]

Yes, G61 would do that.

Cheers
Roger