Z axis Problems

Seems one or some times both sides of Z do not hold position they droop or descend. Sometimes I can just manually screw Z by hand or just spins of its own weight down. Also the Z motors seem warm in comparison to X or Y motors with generate no or very little heat even after cutting fo a couple minutes at a single depth.

Can you share some info about your build? Which controller do you have? Which way do you have it wired? What firmware is on the controller? Maybe a picture or two will help us get our bearings.

When it is powered off, it is normal for it to drop. More than half do. So you should park it before unpowering it. The motors will disable after a few minutes (I can’t remember how long but more than five, less than thirty).

The motor temperature is proportional to the current setting, usually. So if they sit still or move, they should be about the same temp. Since the Z is warmer, that might mean your current isn’t set right. Some info on which controller (and maybe a picture of the controller wired up) will help.

We’ll figure this out.

Jeff, first, this thing would be firewood if you were not out there!!! and I will post pictures when I figure out how to do that. I have Rambo 1.4 (three weeks ago from V1) with what firmware provided (Marlin 509 no suffix like D or S) I did not do anything with the 4 switches provided.

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Possible I was not careful enough when turning off and on and then trying to run an engrave. Will fool with it some more here are pictures I hope.board


The controller looks good. You have the serial firmware. Your screen is upside down :slightly_smiling_face:. The rambo sets the current itself, so unless there is a wiring issue, or the motors are different, they should all be close to the same temperature. Do you have the wiring harness from V1 or did you make it yourself?

Can you describe the issue a little more? Is it falling while milling? Does it finish the test crown without falling?

More info, I tried another Guess you call it “Milling” (engraving?)seemed like all was going well then I noticed when the project was done and the spindle moved to its start position as soon as it got there the left side descended to the bottom , right side maintained its height, then looked at completed milling below and you can see left side is cut deeper than right side, Table is level, thoughts?

The two motors should always move in lock step. But they need to start the same height from the table and the table needs to be parallel to the gantry. My guess is that either the gantry did not start flat, or that the left side lost some steps before getting started.

The falling when the gcode is done might be caused by an M84 turning off the motors.

Lost some steps before getting started? why ? How to fix? I think you may be right code may have an M84 at end will check,

My procedure is drop Z to bottom (printed parts touching, run them up to clear workpiece, maneuver spindle over to start point, drop z to just above start location hit run print in RH

It is not normal for them to skip steps and it is usually pretty obvious.

So the left side only drops after returning to the start point of the project and have noticed that when I try to level the two sides per my procedure above that the left side does not always move up the same amount as the right side did I get a bad motor?

The motors are pretty stupid, and rarely break. The wiring is the problem much more often. Or even more often, the connection to the leadscrew. The grub screws often loosen up.

That’s interesting!
Kevin I am wondering if my problem is exactly the same as yours? I have the SKR Pro 2209 hardware with v509 unedited firmware instead of the rambo. My Left Z axis is solid! That motor only moves when the controller tells it to move. Power On or job or off! However, my Right Z axis as you say, droops or descends. Power on or job or off. However, if falls less when on or doing a job. like yours, when a job is done it falls right away. Which is annoying when I need to setup a tool change.

Like Jeff said; Wiring could be bad… That’s why i trashed all my wiring and bought extensions. I couldn’t make a reliable wire! But even with Extensions I find there are wiring/connector problems. I have also had grub screw problems on my pulleys. I ended up buying a box of grub screws from McMaster Carr to replace the junky ones that came with the pulley. which was pretty hard to find the correct grubs to work with my pulleys. No one tells you what size those things are! 2mm, 2.5mm, 3mm or 4mm?

I noticed I can pull my Right Z axis up or push it down very easily! I tried to do the same with the Left side and i broke my 3d printed part right off… pushed a little too hard… my printed part was pretty weak. (new prints!)

I am going to do a couple troubleshooting things.
First I am going to move that motor to a Y axis as it doesn’t have to hold up the gantry.
If the new z motor still falls I will switch a driver.
If it still falls I will know that everything is working but its still a problem for me. (Jeff, could it be a lead screw nut issue? like a worn out nut?)
So, I have a couple 94ozin motors but I will have to make connectors (eww). As well as edit marlin code to use more current (eww). I have been reading that a larger motor turns less but it’s also heavier.
Jeff, would these be good steps to take to try to resolve drooping, if possible?

Unless the larger motor is 0.9deg or something like that, they move the same amount. The larger motors can handle a little more current, and provide more torque. There aren’t any gears, so it isn’t the same kind of trade off.

As for swapping out the motors and the drivers, those are good steps to take to isolate the problem. But I have been burned by thinking the issue was the motor before. It often follows the motor, and ends up being a wiring issue or something. But, motors are cheap, and if you’d like to replace it, go ahead.

Regarding the lead nut. They can add a lot of friction if they are too constrained, which may make it skip steps while moving, but not while stationary. I would try hard to not just use hands to try things out. Our meat wrenches are much stronger than the machine needs to be. But trying to make it lift a little weight is a nice, comparable test. If you have a bottle of water or something, then we can compare between machines.

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This is the Best quote i have heard today!
Sadly, my meat wrench was trying to help out the Right z motor vs crushing the Left z motor. :slight_smile: While cutting a job the Right starts to lower. So I go over there and lightly raise it back up to about level with the other side. It was only yesterday when I wondered. Does the other side do this too? Crushed it! LOL
Note to self: use a water bottle first.

I am questioning the Left side! Now that i have to replace the plastic parts, I will flip the lead screw nuts first. Always by one change at a time for troubleshooting accuracy.

Thank you for the Motor advice! Before anything I will check my connections.

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Dytoractor sound like we do have a very similar program let me know how the troubleshooting goes…

Robert, I thought these were relevant questions?

I didn’t buy my motors from V1 Engineering but I have the same model: KL17H248-15-4A from Automation Technology. (I already have way way way too many motors because of a 3d printer build. :frowning: )
Kevin, did you buy the kit from V1?

Normal gauge for these motors are 22 awg. Thats what comes on the motor itself. Looks like V1 uses 26 awg for the Y-connections and 22 awg for single lines. (is that because of the length? 1m doesn’t need as thick of wire?)

I was using telephone wire… whatever that is. But my JX-1601 crimper just killed the connector and when they looked right, they would pop off easy. So I gave up and bought 3d printer extension wires. However, I need an adapter between cables and the table is too big for just one cable… so I have two 1m cables and the motor wire to make it to the other side!
Fun fact: that motor works perfectly on that side. Its the motor that just plugs right into the SKR PRO that is the problem. :slight_smile:
Why would different length wires make a difference?

I think I am going to revisite wiring… Have you seen Larry Wimbles machine!!! That is a work of art. If my machine doesn’t look like a bug ball then I will be happy!

My machine is all in parts right now as I am replacing the Y axis mounts. For fun I have flipped the lead screw nuts. My brain also keeps telling me to flip the bad Z axis with the Y axis. It’s just right there and easy to get too! But troubleshooting experience tells me its a bad idea.

When I asked those questions, I was thinking that additional resistance due to the wiring or due to a bad connection would make a differential difference between the two motors. It would if they were wired in parallel or each had its own driver, but in thinking about series wiring, it would not make a differential difference. That is any loss of power would be shared equally by both motors. And since you are wiring your two motors in series, it cannot be a problem with the current settings of the driver either.

Looks like V1 uses 26 awg for the Y-connections and 22 awg for single lines.

I did some rough calculations to see if wire resistance would make a difference last night, and it just did not pan out. I explored one stepper motor having 6 feet of additional 26 gauge wire and found that only added 0.25 ohms to that leg. And as above, it would only have an impact if each stepper had its own driver. Your steppers have 2.8 ohms per phase, so 0.25 ohms would not have the kind of impact you are seeing even if they had separate drivers.

The only thing you might check is resistance of each coil in both motors. If one motor has higher resistance for one or both coils, it would result in one motor being weaker than the other, but I’m thinking this is unlikely.

Edit: In the case where one motor has coil resistance that does not match the other, the motor with the lesser resistance might be the stronger one. So it is possible that the stronger motor is the “bad” one that needs to be changed. Again, I doubt the stepper motors are the problem.

Robert, I am using parallel wires. The Dual Endstop LR profile. Where each motor gets its own driver. Not sure what Kevin is using???
I was just referencing data on the V1 shop.

Differential Difference is going to be a new bug ball in learning in about an hour. :slight_smile:

How would you even check the resistance? I use my meat wrenches and that’s not very accurate!

Oh, the bad motor would be the one with more resistance. mind boggling! I don’t know very much about motors.

I’m talking about electrical resistance as measured by a multi-meter.

Differential Difference

Just some (probably poor) English I made up to talk about the two motors having different strengths (or not).

the bad motor would be the one with more resistance

The bad motor could be the stronger one which has less electrical resistance, and therefore draws more current. But if there is less resistance, then either the steppers are not matched or there is something wrong with it meaning the extra current may not result in extra strength. Again, all this only applies to series wiring, and it is just my theory on how a mismatched set of steppers would behave. There nothing here to help you solve your problem if you are using one driver for each stepper.

Not sure what Kevin is using

He only has three stepper drivers wired up in his picture, so he is using series wiring. If your issue is electrical (and there is a good chance it is not), then it will not be the same issue as Kevin’s issue.


So for your issue, if you’ve exhausted the mechanical possibilities and want to look at electrical ones, the first thing I would do is swap the Z wires going to the drivers at the control board. You will probably have to rotate the connections so the steppers spin the correct direction. Then test your system. If the weakness travels to the new motor, then the issue will be driver related. If it does not, then it is potentially stepper related or possibly wiring related (again assuming the issue is electrical).

P.S. This confusion about the issue and the unlikeness that my theory had merit is the reason I deleted my original post.

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