AVID PRO Acceleration/Plunge issue

Hi Team,

I have an inconsistent issue with my Avid Pro 60120 with Nema 34’s. I’ve had the machine built for over a year and this error happens every 8th-10th run on the same g code.

The error: my z axis will finish a pass, arrive at the .25 plunge z, try to move to safe z, but overloads the motor, motor makes a “I’m trying to move” buzz while losing the 2.75 inches of steps, moves over and tries to plunge the 2.75 inches to the .25 plunge z point through the table!

My Z acceleration is set at 6in/sec^2, the feed rate is 20, and my connections are secure. Like, I ran 10 RV panels back to back with no issues.

What could possibly be going wrong? I can’t do anything but watch it run, hoping that it won’t error out and I’m burning time.

I don’t have my dust collection grounded, but I doubt that’s the issue.


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Update: the machine did start to move towards safe z, did not make it and lost steps, and then plunged into the table.

I’m thinking the wire could be compromised, but testing them now. Swapping the Z and X motor wires - shot in the dark.

Have you considered the issues and suggestions in this thread:


Here’s another one:

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Thank you Steven. I’m checking the coupling, the brake, grounding the dust collection, ensuring the connection cables are connected and not touched during use.

The issue did not occur on x axis, so wires are good.

What is the plunge rate, and what is the accel setting for X and Y axis? I have heard of issues if the Axis’ are very different. your feed and Z accel are pretty slow, so I was just checking to see that X and Y were in the same accel ballpark and Z plunge is similar to 20 as well.

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Thank you. My x & y are much different than my Z.

I’m taking the motor off and checking the coupling/axis brake ASAP. I think the brake could be failing - the z is easy to pull down, but extremely difficult to lift with the motors off. Like way too difficult, since my 60 year old dad can push his up with ease.

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Ya, that doesn’t sound right.

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If the brake for the ball screw is going to fail they tend to fail quickly (as in new as oppose to old). It will result in losing steps but only in the positive direction. So the Z will plunge deeper and deeper.

Also make sure the coupling is tight for the motor to ball screw (both halves). Sometimes just one side has worked itself loose and it starts binding because of misalignment. The rubber spider will get all twisted up and wreck the motor. I have only destroyed one stepper motor in my 30+ years of CNC operation and 22 years of DIY CNC work and it was on the AvidCNC and the NEMA34 for the Z axis.

Be glad you don’t have an ATC yet. This sort of problem gets really expensive in that situation. #1 reason I use a tool setter going out and coming back in. These machines are prone to lose steps in the Z and that can break things.

(wow, I am getting old! I am stuck in 2012 :rofl: )


I tried to do a air pass of surfacing my table with no bits and 4 inches above the table by the time I reached the last two passes the router was rubbing the table does this sound like what’s happening to you?