Z Axis not moving properly

5295 Views 29 Replies 12 Participants Last post by Albert Z, Dec 20, 2021

willkoenig

Discussion Starter · Jul 17, 2021

I recently built a cnc and everything works fine except the z axis isn't moving how it should. When milling the z axis will get lower every time it retracts as if it is loosing steps. Also when I jog the machine it can't jog more than about 7mm in the z without stopping for a second then moving again almost as if it is binding. I connected the x plug to the z motor and the z works perfect and doesn't bind but the x axis does exactly what the z did when connected to the z plug and driver. I've tried a different driver, checked wiring, as well as changed voltages on the driver. The only way the z axis movies smoothly for more than 7mm is if the feed rate is turned down considerably. All other axis work great. Any help would be greatly appreciated.

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difalkner

· #2 · Jul 17, 2021

Welcome to the forum! Got any photos of your build? Photos always help with getting good replies.

First question 1) is it a router or spindle? 2) if you take the router/spindle out of its mount does Z act normally? 3) if you switch cables with X, for instance, and jog X does the router/spindle raise and lower as it should? 4) what stepper motor are you using (oz. in. rating)?

Obviously what I'm getting at is the weight of the router/spindle as opposed to the stepper's ability to raise and lower it on its bearing system.

willkoenig

Discussion Starter · #3 · Jul 17, 2021

difalkner said:
Welcome to the forum! Got any photos of your build? Photos always help with getting good replies.

First question 1) is it a router or spindle? 2) if you take the router/spindle out of its mount does Z act normally? 3) if you switch cables with X, for instance, and jog X does the router/spindle raise and lower as it should? 4) what stepper motor are you using (oz. in. rating)?

Obviously what I'm getting at is the weight of the router/spindle as opposed to the stepper's ability to raise and lower it on its bearing system.

Thanks for responding so quick. It’s a spindle that I bought off of Banggood a while ago. Z does the same thing regardless of spindle. I did try switching cables with x and spindle raises and lowers perfect when I jog x. When I do plug in z to x axis and jog z, the x movies with the same problems that the z axis had.

difalkner

· #4 · Jul 17, 2021

What controller software are you using?

willkoenig

Discussion Starter · #5 · Jul 17, 2021

difalkner said:
What controller software are you using?

I’m using the newest version of grbl on a sainsmart board. I’ve been using easel as a post processor but I’ve had the same problems jogging with UGS

difalkner

· #6 · Jul 17, 2021

Same steppers on each axis?

willkoenig

Discussion Starter · #7 · Jul 17, 2021

difalkner said:
Same steppers on each axis?

Yep I’m using Nema 17 on each axis

old55

· #8 · Jul 18, 2021

Welcome to the forum.

BalloonEngineer

· #9 · Jul 18, 2021

Easel will change the Z-axis settings in GRBL. Unless you have an X-Carve, do not use easel as a sender, change to UGS, Candle or one of the numerous other GRBL sender programs. Check your $102 settings and reset it to the value correct for your machine.

Reactions: 3

jw2170

· #10 · Jul 18, 2021

G'day @willkoenig Welcome to the forum.

ger21

· #11 · Jul 18, 2021

A Nema 17 is pretty weak for a Z axis. If there's no binding anywhere, it may just be underpowered.

TimPa

· #12 · Jul 19, 2021

just guessing here...

willkoenig said:
I connected the x plug to the z motor and the z works perfect and doesn't bind but the x axis does exactly what the z did when connected to the z plug and driver.

how did you test for the Z operation here, jogging it around may not have been enough of a test? unless you can get the original configuration to fail by doing the same thing.

another option, is there any lift assistance being used on the size unit you built? like a gas cylinder or air cylinder? it could be as simple as allowing the spingle/carriage to (freely) fall onto a scale, measure the weight, and install a gas cylinder of an egual pound pressure and length.

hats off to you for building your own cnc!

difalkner

· #13 · Jul 19, 2021

I don't think it's a weight issue as I initially suggested. He switched cables with the X axis and X performs the same way as Z with the switched cables. See Post #3.

4DThinker

· #14 · Jul 21, 2021

Stuttering behavior, traced down to the driver as it follows the cable no matter which axis plugged into it. Not much left to check but the cable itself for shorts, the plug ends, or the driver in the controller box. You can test the cable itself by switching it with another. Once you know the cable is good then the problem lies in your controller box.

Reactions: 2

maddog

· #15 · Jul 21, 2021

One thing that no one has mentioned is to check your coupler and make sure it isn't slipping. I've had this happen to a few clients as they used a small allen wrench. Use a T-handle style allen wrench to tighten the coupler.

wyzarddoc

· #16 · Jul 21, 2021

willkoenig said:
I recently built a cnc and everything works fine except the z axis isn't moving how it should. When milling the z axis will get lower every time it retracts as if it is loosing steps. Also when I jog the machine it can't jog more than about 7mm in the z without stopping for a second then moving again almost as if it is binding. I connected the x plug to the z motor and the z works perfect and doesn't bind but the x axis does exactly what the z did when connected to the z plug and driver. I've tried a different driver, checked wiring, as well as changed voltages on the driver. The only way the z axis movies smoothly for more than 7mm is if the feed rate is turned down considerably. All other axis work great. Any help would be greatly appreciated.

Just a shot in the dark but maybe some 3 in 1 oil???

maddog

· #17 · Jul 21, 2021

You could try, but that shouldn't cause it to get lower. Sounds like slippage of the coupler either on the motor side or the screw side.

wyzarddoc

· #18 · Jul 21, 2021

I agree with the other posts Nema 17 unless they have gear reduction are really too small for CNC. Another thing to try is the the pulse rate on your drivers if they are set too high you will skip pulses. You are asking a lot of a Nema 17 to lift any type of router that weighs more than a few oz. Check and you could possibly use a Nema 23 with the drivers and power supply you have. But you might need to rebuild the motor mount and buy a new motor connector.

difalkner

· #19 · Jul 22, 2021

maddog said:
One thing that no one has mentioned is to check your coupler and make sure it isn't slipping. I've had this happen to a few clients as they used a small allen wrench. Use a T-handle style allen wrench to tighten the coupler.

maddog said:
You could try, but that shouldn't cause it to get lower. Sounds like slippage of the coupler either on the motor side or the screw side.

wyzarddoc said:
I agree with the other posts Nema 17 unless they have gear reduction are really too small for CNC. Another thing to try is the the pulse rate on your drivers if they are set too high you will skip pulses. You are asking a lot of a Nema 17 to lift any type of router that weighs more than a few oz. Check and you could possibly use a Nema 23 with the drivers and power supply you have. But you might need to rebuild the motor mount and buy a new motor connector.

Read Post #3 again - he switched cables with X and X performs like Z did but now Z works with X axis cabling. So that sort of rules out the NEMA 17 stepper being too weak, coupling loose, oil, weight of spindle, etc.

The OP hasn't checked back in since he posted this so maybe he got it working; either way I hope he sticks around.

Reactions: 1

wyzarddoc

· #20 · Jul 22, 2021

I hope he solves his problem and posts the solution. And also would like to see more posts from newer members. I agree with the slipping couplings since I have been the victim of that problem and wasted a nice piece of wood.

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