# Z axis not returning to zero?



## WoodWiddler (Jan 5, 2021)

Hi everyone, first post here. I have a DIY built cnc machine, been using it for 6 months now, it work great from the beginning but now noticing the z axis is not returning to zero when I send it home position, when I do a big job that requires a lot of up and down and many passes with a v bit carving the z axis drops more and more so when you send it back to home after a job the z axis drop quit a bit, I have check my motor coupler and set screws and they were tit. Is it possible that my z motor is not strong enough? I am using a 
*Nema23 23HS5628 4 Lead Nema 23 Stepper Motor 57 165 Oz-in 56mm 2.8A 6.35mm/8mm TB6600 CNC*























Has anyone ever encounter this problem? Thanks for any suggestions!


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## difalkner (Jan 3, 2012)

Welcome to the forum! That doesn't seem like a very strong stepper; if you disconnect the screw can you raise and lower the carriage assembly without much effort? In other words, is it mechanically binding anywhere, sufficiently lubricated, etc.? If you take the router out and dry run it through a job does it raise and lower correctly?

David


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## WoodWiddler (Jan 5, 2021)

difalkner said:


> Welcome to the forum! That doesn't seem like a very strong stepper; if you disconnect the screw can you raise and lower the carriage assembly without much effort? In other words, is it mechanically binding anywhere, sufficiently lubricated, etc.? If you take the router out and dry run it through a job does it raise and lower correctly?
> 
> David


Yes when I disconnect the screws it's very smooth no resentence, I lube my rail glides often but I will try to take the router and do a dry run. Thanks will let you know.


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## breezy (Nov 4, 2011)

Classic example of acceleration overload resulting in lost steps.
The load of lifting the Z axis is greater than moving down.
If your controller allows looping run this code and check that it returns to the start point. L100 on M30 is the number of loops to run.
Set G54 Z zero to the middle of the Z axis travel. Numbers are in millimetres.

G54
G00
Z20
Z0
Z-20
Z0
M30 L100

If Z zero shifts down you are loosing steps on the up travel.
Reduce your acceleration rate to half and try again if the results are OK then increase by 10% and repeat until you are loosing steps. The last setting is the one that is best for your machine.

Regards, Arie.


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## MEBCWD (Jan 14, 2012)

Welcome to the Router Forums.

You might check to see if running a different file will cause the same problem, If so then it is not a gcode problem like using the wrong post processor. One problem that would be gcode based that can cause the Z-axis drop would be any call that tops out the Z-axis but those are usually large drops in Z height.

Check your calibration for your Z axis and make sure it did not get changed accidentally. That could cause it to carve deeper but it would also be a consistent drop through the entire project.

If it is not one of these problems then you are probably overdriving that stepper like breezy suggests.


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## WoodWiddler (Jan 5, 2021)

difalkner said:


> Welcome to the forum! That doesn't seem like a very strong stepper; if you disconnect the screw can you raise and lower the carriage assembly without much effort? In other words, is it mechanically binding anywhere, sufficiently lubricated, etc.? If you take the router out and dry run it through a job does it raise and lower correctly?
> 
> David


I tried a dry run no luck I still get a drop.


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## WoodWiddler (Jan 5, 2021)

breezy said:


> Classic example of acceleration overload resulting in lost steps.
> The load of lifting the Z axis is greater than moving down.
> If your controller allows looping run this code and check that it returns to the start point. L100 on M30 is the number of loops to run.
> Set G54 Z zero to the middle of the Z axis travel. Numbers are in millimetres.
> ...


I've ran the gcodes but my controller don't recognize M30 L100 I get error. Tried dropping the acceleration also no luck. I've swap the motor no luck. Thinking of swapping the motor driver for the z axis.


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## ger21 (Feb 10, 2019)

Try decreasing the Z axis acceleration by 40-50% and see if it helps.


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## MEBCWD (Jan 14, 2012)

You say you have been running it for 6 months before this problem came up. Did you try running a file that you have run before that ran without any problems? That might tell you if it is possibly a problem in the gcode file.

I did re-read the specs for your driver and stepper and that driver/stepper combo might be underpowered somewhat. What power supply are you running for the 4 drivers/steppers and control card? It might not be adequate to power everything and could be getting weak.


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## old55 (Aug 11, 2013)

Welcome to the forum @WoodWiddler


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## WoodWiddler (Jan 5, 2021)

MEBCWD said:


> You say you have been running it for 6 months before this problem came up. Did you try running a file that you have run before that ran without any problems? That might tell you if it is possibly a problem in the gcode file.
> 
> I did re-read the specs for your driver and stepper and that driver/stepper combo might be underpowered somewhat. What power supply are you running for the 4 drivers/steppers and control card? It might not be adequate to power everything and could be getting weak.


Yes I've ran other files and still get z axis drop. I am running a 12V 15A 180W power supply, 6 small cooling fans I think they are 0.18A each, and also a small led strip light witch I don't know the amp but I'm sure it's not mush and Arduino Uno with CNC Shield.


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## marecat3 (Nov 30, 2010)

Welcome to the forum


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## breezy (Nov 4, 2011)

WoodWiddler said:


> Yes I've ran other files and still get z axis drop. I am running a 12V 15A 180W power supply, 6 small cooling fans I think they are 0.18A each, and also a small led strip light witch I don't know the amp but I'm sure it's not mush and Arduino Uno with CNC Shield.


You are loosing steps because driver voltage is too low. 
TB6600 can have a input voltage of 42v.
Rearrange your wiring so that the drivers are on their own 42v power supply, leave all other ancillary items on the 12v supply.
The higher the voltage the more power/torque available from the steppers. When you have done that you will be able to adjust your acceleration and rapid feed rate to improve the performance.


Sent from my iPad using Tapatalk


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## TimPa (Jan 4, 2011)

is the digital read out for z position accurate when the z axis is dropping? in other words, is it reading where the z axis should be, or is it reading where it actually/physically is.

have you tried running a program with little to no x azis activity, like a spoil board resurface program, does it still drop?

you may aslo try running one of the programs which exhibits the failure, with the router removed. less weight and mass will be less load on the stepper, indicating an underpowered motor/driver.


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## WoodWiddler (Jan 5, 2021)

breezy said:


> You are loosing steps because driver voltage is too low.
> TB6600 can have a input voltage of 42v.
> Rearrange your wiring so that the drivers are on their own 42v power supply, leave all other ancillary items on the 12v supply.
> The higher the voltage the more power/torque available from the steppers. When you have done that you will be able to adjust your acceleration and rapid feed rate to improve the performance.
> ...


I've replace my power supply with a 12V 30A 260W but no change I still get z axis drop when doing any kind of v carving.


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## WoodWiddler (Jan 5, 2021)

TimPa said:


> is the digital read out for z position accurate when the z axis is dropping? in other words, is it reading where the z axis should be, or is it reading where it actually/physically is.
> 
> have you tried running a program with little to no x azis activity, like a spoil board resurface program, does it still drop?
> 
> you may aslo try running one of the programs which exhibits the failure, with the router removed. less weight and mass will be less load on the stepper, indicating an underpowered motor/driver.


Yes my digital reading goes back to 0000 when I send it back home but when I take a measurement of the router on the z axis it dropped so it lost some steps on the up during the program and I've tried running different programs I get the same thing. resurface something is find no drop at all goes back home ok. I ran it without the router in on a v carve program and still get a drop z axis.


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## ger21 (Feb 10, 2019)

Did you see my earlier post about decreasing acceleration?
Also, have you lubricated your ballscrew and bearings?

You want at least a 36V power supply. Powering steppers with 12V will give very, very poor performance.


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## WoodWiddler (Jan 5, 2021)

ger21 said:


> Did you see my earlier post about decreasing acceleration?
> Also, have you lubricated your ballscrew and bearings?
> 
> You want at least a 36V power supply. Powering steppers with 12V will give very, very poor performance.


Yes thanks I did try decreasing acceleration but no change, also checked all ballscrew and bearing I lube them often and all running smooth, as far as my power supply I followed the plans I got and called for power supply 12V 15A 260W and I've been running it for 6 mounts from the start with no problem this just started, I will order a new power supply and try that thanks.


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## breezy (Nov 4, 2011)

It’s not the amperage that is the problem, you need to up the voltage, get a 36 volt power supply!!
Regards, Arie.


Sent from my iPad using Tapatalk


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## WoodWiddler (Jan 5, 2021)

breezy said:


> It’s not the amperage that is the problem, you need to up the voltage, get a 36 volt power supply!!
> Regards, Arie.
> 
> 
> Sent from my iPad using Tapatalk


I had a spare 24V 15A 360W power supply put that one in, replace all my TB6600 stepper motor to DM542T stepper motor and wow!! will never by sheep stuff again so quiet and smooth back in business. Thanks guys for all your help.


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## old55 (Aug 11, 2013)

Great result.


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