Z Axis Slipping

Mostly Printed CNC - MPCNC Troubleshooting
1

Hey all,

When I move the z axis down towards the stock there is a certain point where the tool holder slips noticeably drops and after that point, when I try to move the holder up, the stepper spins but then unwinds back down so no distance was traveled.

It seems like the motor is not strong enough to keep the tool holder in place or raise it up once it gets too far away from the gantry.

I know this should not be the case. I have yet to adjust the current on the stepper drivers, could that be the issue or is there something more obvious?

Thanks,

Mark

2

That is likely your problem

1 Like
3

I have the same problem in the last 4 days.
Who will tell me how to adjust the current if I use the MiniRAMbo board?

4

If you are using all of my stuff, that is not the problem, you have not told us about your steppers so assumptions were made.

The most common problem for the Z axis is a tight build and lack of lube. Look through the Z axis instructions again and see if that is exactly what you did as there are a few lines in there that really help (znut) and the Z axis moves extremely easily with your finger tips alone.

5

Yes, I purchased the mechanical kit from you, but I’m using a cnc v3 shield with the A4988 steppers.

I did leave the z nut loose such that it can freely wiggle around and I lubed the acme screw as well. I can easily move the z axis with my fingertips, this is how I fine tune the starting location.

6

So did you change the step rate and set your drivers accordingly?

Is a 20mm move 20mm, or 40mm, or 10mm?

7

Correct. I am using 1/16 steps and 20mm = 20mm.

Remember, everything is fine during the travel until a certain depth and then it’s like the mechanal load is too great for the motor to hold or lift

In practice, when the machine is actively milling, the only noticeable issue is the tip drags the top of the stock on the way to the first cut

8

If your rapids and plunge rates are okay, then it is Z axis binding.

Some people run 7lb routers and I have put up a video of 20 or 50lbs being lifted on my LR. My recommended hardware has no issues with load.

9

Makes sense

10

Adjusted the current, added more lube, and loosed the acme nut. Still having the same issue. I attached a video of the movement.

 

[attachment file=104987]

 

 

11

From repetier.

G0 Z10 F200

 

What happens?

You video looks like it is trying to move 30x too fast.

If that doe snot work you need to list your board, drivers, settings, control software, exact steps to cause the problem. We are wildly making guess over several days. We need more info to make educated answers please.