# Z Axis not moving properly



## willkoenig (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 (Jan 3, 2012)

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.


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## willkoenig (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.


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## difalkner (Jan 3, 2012)

What controller software are you using?


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## willkoenig (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


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## difalkner (Jan 3, 2012)

Same steppers on each axis?


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## willkoenig (Jul 17, 2021)

difalkner said:


> Same steppers on each axis?


Yep I’m using Nema 17 on each axis


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## old55 (Aug 11, 2013)

Welcome to the forum.


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## BalloonEngineer (Mar 27, 2009)

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.


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## jw2170 (Jan 24, 2008)

G'day @willkoenig Welcome to the forum.


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## ger21 (Feb 10, 2019)

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


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## TimPa (Jan 4, 2011)

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!


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## difalkner (Jan 3, 2012)

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.


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## 4DThinker (Feb 16, 2014)

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.


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## maddog (Feb 28, 2010)

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.


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## wyzarddoc (Dec 31, 2006)

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???


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## maddog (Feb 28, 2010)

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.


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## wyzarddoc (Dec 31, 2006)

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.


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## difalkner (Jan 3, 2012)

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.


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## wyzarddoc (Dec 31, 2006)

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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## wyzarddoc (Dec 31, 2006)

I re-read the post 3 again and from that it seems the pulse tuning on the z-axis is incorrect since when it's plugged into the x axis the problem now occurs on the x axis if I am reading post #3 correctly.?


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## difalkner (Jan 3, 2012)

I read #3 to be when the cabling from Z is connected to the X axis then the X axis takes on the issues he's having with the Z axis, and that Z now works just fine with the X axis cabling and driver. So even though he's been through the cabling and driver setup for Z it sounds to me like that's where his problem resides.


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## wyzarddoc (Dec 31, 2006)

I agree. Do we know what CAM software he is using to execute the G-code? If mach 3 then you can go to I think Alt-6 page just above the reset button and do a calibration based on distance. Otherwise it's hit and miss on tuning with things like grbl packages.


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## difalkner (Jan 3, 2012)

In Post #5 he talks about his software.


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## Rev. A (Jan 29, 2021)

Stepper motors are more trouble than they are worth. Any dirt or grit can cause them to loose track of where they are. I've ben a machine tool guru for most of my long life and am convinced that scales or absolute position encoders are the better alternatives, although expensive.


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## difalkner (Jan 3, 2012)

Rev. A said:


> expensive


And that's why most every hobby shop or light duty commercial shop uses steppers. Most can't afford servos or other more expensive options.


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## willkoenig (Jul 17, 2021)

BalloonEngineer said:


> 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.


I will try this and get back on whether it worked


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## willkoenig (Jul 17, 2021)

difalkner said:


> 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.


I haven’t solved the problem yet. I have been living in a different area for the last few months and haven’t been able to work on the cnc. I’m back to testing and will try your suggestions. Thank you!


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## willkoenig (Jul 17, 2021)

I have tried replacing the stepper driver, changing wires, checking $102, but nothing seems to change. Whatever motor/axis is connected to the z port on my controller will act as if it is skipping steps, making a whining noise and not moving the full distance at any feed rate above 500. At this point I am thinking maybe a bad controller?


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## Albert Z (Oct 23, 2021)

Hello Will

I'm a relative newcomer to the forum but I would like to jump into this discussion. I know a thing or two about stepper motor drivers having designed a few from scratch. I am sure I can help you solve your problem, but I need lots more info.

So here we go with a series of questions that could help me zero in on the problem. Some of them may not be relevant, but we won't know until we step back and look at the big picture.

What is the current and torque rating rating for your stepper motors? Do you have a data sheet? NEMA 17 tells us nothing except the motors are physically smaller than NEMA 23.

What size power supply are you using to power the drivers? (Voltage & Current Rating) Is it linear or switching?

How do you set the current limit on your drivers?

Are the drivers integrated into your controller or separate?

Do your drivers have microstep capability?

It would be great if you could post some photos of your setup including the Z-axis arrangement and drivers and associated wiring.

Albert


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