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Ultimaker 2 z-axis pops and jumps layers, ruining almost all of my prints

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Hi! ;)

I'm experiencing an issue a month now with my UM2 that's that is ruining almost all my prints. The z-axis begins to pop and jump layers. Just take a look at the video below:


Curiously, the pops remain even after stopping the printing job. Sometimes I have to turn off and on or in some cases reset to factory settings to stop the problem.

In this other video, you can listen to a loud pop at 0:06 and 0:36 (the interval between the pops can vary from one print to another).



The problem happens in about 2 of each 3 prints and it's almost impossible to detect the conditions under which it appears. No matter the layer height, temperature, speed or filament I use, the issue persists.

Here's an example of the print result (In this case, using the UM original PLA blue filament).

Ultimaker 2 z-axis pops and jumps layers

(Owl statue from Thingiverse: http://www.thingiverse.com/thing:18218)

I've bought my UM2 at the Maker Faire NYC, in september. Maybe it's one of the pre-production units, right?

Can anyone help me to solve it?


I have a couple more issues with my UM but... one at a time.

This one is driving me crazy! :(


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Are you sure that it's the Z-axis making the noise, and not just the extruder skipping steps, and clicking backwards?


I'm sure it comes from the z-axis. Sometimes when it pops louder, the buildplate goes down about 3 or 4 mm and the UM begins to extrude material "in the air". In the first video, at 0:43 I interrupt the print job and the pops remain.

I also have the underextrusion issue (I managed to isolate the problems) and it prevents me from printing at speeds faster than 50mm/s (even with .1mm layer, 220C and UM original filament, for example), with the tension on the filament set to the minimum. But, while I don't have time to solve, I can cope with this by printing slower. Probably it's something related to the spring tension inside the extruder drive.


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Did you look at the z screw? Is it rotating when this happens?

I have 10 theories that might cause this. I'm not excited about any of them. Lets try to eliminate some things. For example the Z stepper might be too weak to hold the bed up. If so you should be able to see it rotate on every "pop".

Or the linear bearings might be defective. Or the vertical friction might be extreme and the Z axis might move in a mixture of small and large steps. Or there could be a cura bug that is moving the Z on purpose or many other things. Or the Z nut might be loose and rotating.

Try to get some video of the z axis to see if it is rotating. Try to get some video of one of those 2 vertical rods that shows the movement when the "pop" happens.

for the rotation of the z axis it might be better to video from below the bed but don't let your phone or hands get crushed!

Also it would be good to show the extruder motor in a video while the popping occurs. I suspect the popping is caused by 2 different things:

1) Extruder motor

2) Something to do with the Z axis

And the videos you posted only showed #1 possibly. #1 could possibly continue after printing is stopped but only 2 or 3 times.


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There should be a little pack of green grease that came with your UM2. With the blue tape and screwdriver. If you don't already have lots and lots of grease on the z-screw then add it! If you touch the Z screw the grease should get all over your fingers. A "pea" sized drop is good, then move the bed up and down 3 times to spread it around.


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Moving the bed by hand might help to feel if there's something mechanically off (if it binds). With the power off it's easy to push the bed down by just placing your hand gently on it.

You can move it up as well but it requires more force. To make sure you don't damage anything make sure that you put the pressure in the very back on the printer, as close to the back wall as you can. If you just grab the bed and lift you're going to put a lot of force on it and it might bend.

You can also spin the screw of course but it gets messy :)


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Folks, I think I've caught the problem!

It's overheating ;)

Yesterday I began my print day at 9:00 AM and managed to print two owls in sequence without any issue (aprox. 4 hours of printing job). But at the third print, the problem came back and very marked. I've killed the job and observed the following 15 minutes after. The noises were decreasing in intensity and frequency until stops completely.

I googled the issue and found some similar cases from other brands' customers. Most of them reported the same symptoms and the cause as overheating in the z step motor.

I realized that at night problem occurred less frequently. My wife raised an hypothesis: "When the ambient temperature drops". At this time, the temperature in Brazil is about 35C during the day and about 20C at night.

So, I found this page at UM Wiki:



"Tuning the stepper motor drivers


  • On the little stepper driver boards (see picture on the right) that are inserted into the electronics, there are trimpot's that can be screwed clockwise or counter-clockwise.
  • The pre-mounted Ultimaker stepper drivers come pre-configured with a sane setting, but you might want to tune it to work better in your climate. Below are some instructions.
  • If a stepper board overheats, it will shut down for a short while, leaving the motor alternating bewteen a powered and unpowered state. This means they are overpowered and/or undercooled. You should lower the power setting by turning it counter-clockwise, slightly. For the extruder motor, you might experience this as a clicking or ticking sound, like in an old antique clock.
  • To know exactly how much you've turned it up, please turn it counter clockwise first. It will go until about 7:30 O'Clock, where it reaches a stop. The top is half-way"


Just to test the hypothesis, I managed to reproduce the issue by printing non-stop again. When the pops came again, I put the printer, while it was working, on a table support and a fan below it. I've also I took off the electronics cover:

A Fan below my UM2 to reduce z-axis overheating and stop the "popping" issue


Today, my UM2 worked for about 10 hours straight, with the fan below and...

BINGO! No pops or layer skips at all. :D

I'll keep an eye on it and maintain this topic updated but the problem seems to have been solved.

Thank you, guys, for all the help!


BTW, i'm thinking to make a fan mount to cool the z motor.


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The UM2 has software controlled stepper current. There is a way to control it but you would have to add a special gcode command to your gcode file before copying it to the SD card.


Do you mean M906? http://reprap.org/wiki/G-code#M906:_Set_motor_currents

What are the default values?

// Thanks, that the hint.


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Much discussion here:


But no, M907 as in:

M907 Z255 is full current THIS IS WRONG - 255 WILL DO 255MA

M907 Z166 is default (1.3 amps) ALSO WRONG - USE Z1300 TO GET 1.3A

Actually I think M908 will work also:

M908 P2 S127 (or maybe P3???) should set Z to 1.0 amps

Now I tested these commands a while back as you can see in the link above but they didn't work. But Daid said he would enable this feature in a future version of Marlin so maybe these work now.

Edited by Guest

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Yes, I have enabled the M907 command for future versions, but your description is wrong.

It is M907 Z[mA], so

M907 Z1300 sets the current to 1.3A, which is the default.

I just had a quick talk with our electronics guy, and he finds it odd, as the UM2 was tested up to 45C ambient temperature. And we had UM2's running here in the Netherlands this summer, in a room that most certainly got over 35C. (Not saying that it could not happen, just that we did tests and that this problem did not come across in those tests)

However, you could try keeping the electronics cover off, to see if that helps in losing some heat. If that does not fix it, there is also a 24V fan connector on the board. The disadvantage is that fans make noise, and there currently is not really a place to properly fit the fan in the casing.


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(Not saying that it could not happen, just that we did tests and that this problem did not come across in those tests)


Can confirm OP's exact problems on the UM1+. Sorry to drag up an old topic but OP's solution pretty much saved me from giving up on this printer. I ended up using a holesaw on the electronics cover and mounting a small cpu fan to it.


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