Z-Axis layer error

[JohnFox 25]

I'm pretty sure the problem is with the bearings. Unless the rods are very marked and dented, they should be OK.

If you can undo the bearings, ( it's a real pain to do this ) and slide them up and down the rods, they should run smoothly with a slight 'whirring' sound. If the balls in the bearing get out of position they will suddenly lock and the whole thing jams. A slight twist and it will run again. In my experience, the more oil on the pillars, the more times the bearings lock.

Not sure of the advantage of the roller bearings over the slide bearings used on the X and Y axes, any mechanical engineers out there? This banding problem seems to be a pretty common fault.

Hi Markus,

yep, thats the one. Default 16,7mm/s. Just checked again, I changed it to 30mm/s not 60mm/s.

Try that and it should be OK.

Update on my case. I explained this behavior to igo3d and they want me to send the printer back. It is on its way there now.

I will keep you posted.

Thanks. But I wonder if this has any implication for the hardware? The help tooltip says

"Rapid movement speed for Z-axis when machine is not printing, should match actual Z-axis movement speed between layers for accurate print times"

[markusmaker 2]

I'm pretty sure the problem is with the bearings. Unless the rods are very marked and dented, they should be OK.

If you can undo the bearings, ( it's a real pain to do this ) and slide them up and down the rods, they should run smoothly with a slight 'whirring' sound. If the balls in the bearing get out of position they will suddenly lock and the whole thing jams. A slight twist and it will run again. In my experience, the more oil on the pillars, the more times the bearings lock.

Not sure of the advantage of the roller bearings over the slide bearings used on the X and Y axes, any mechanical engineers out there? This banding problem seems to be a pretty common fault.

Hi John,

thanks for your reply. I will sent the printer to iGo3D for checking/changing the bearings.

Kind regards,

Markus

[markusmaker 2]

Short update:

Before sending the printer to iGo3D for new bearings, I cleaned the guidances with soft cloth multiple times. I did a number of prints - no gap or bed drop so far...

[gr5 2,167]

Were you joking about the print times thing? If you your actual print time is 10 seconds faster than predicted by Cura (which assumes slower Z movement) is that going to be a problem for you?

It may seem like 2 or even 10 people on the forums having a problem with the Z is "common" in reality it may be only one person in a thousand. I suspect it's pretty rare. I've used easily 10 different UM2 printers, probably 20, and none of them had Z banding issues.

[markusmaker 2]

I was glad to early... printed a wind wheel multiple times.

First try in red PLA worked out:

https://www.dropbox.com/s/v1x2zgaw82sz5ec/windwheel-1-rot-ok-04PLA025L_20151128003256.mpg?dl=0

Second try blue PLA (bed drop) with layer gap:

https://www.dropbox.com/s/bcb7079m50852w2/windwheel-2-blau-fehler-04PLA025L_20151128092526.mpg?dl=0

Third try blue PLA worked out:

https://www.dropbox.com/s/ar0ixhfgplmp6yl/windwheel-3-blau-ok-04PLA025L_20151128120412.mpg?dl=0

Watch the front edge closely in all timelapses as you can see the bed drop clearly.

Red PLA was from spool. Blue PLA was loose sample material. Always printed with same layer height and same temps.

Printer is packed now and I send it to iGo3D on Monday.

[Wolverineairsoft 0]

Add me to the list. Brand new U2 banding at 10-15mm. Definite binding at that height from the linear ball bearings. Any known solutions?

[gr5 2,167]

Sorry I don't know if my video player is terrible or if it's just hard to see. I can't tell if the Z axis speeds up or if it underextrudes.

If the Z axis drops suddenly it might have nothing to do with the bearings - it could be the Z stepper controller - that is a similar problem but different. In that problem it doesn't always occur at the exact same height although typically with printing the same part it does happen close to the same spot. But different parts will happen at different heights (small 1cm by 1cm tower will happen higher as you can print much faster and so the problem occurs higher up).

[markusmaker 2]

Hi Gr5,

when you watch the flow of the bed you can see it is a little jumpy when then layer gap happens.

The height varies slightly but always in the first 15mm of the print. I also did a 20cm tall vase with no problems at all.

I already tried to decrease and increase the Z stepper current. Lowering it to 1150 seemed to make the problem occur more often, increasing it to 1350 it happend less. But could also be pure coincidence as it is not easy to reproduce.

As you can see here:

https://www.dropbox.com/s/4qmhl1r04pra0b4/beddrop2.mp4?dl=0

the filament is coming but only sticks to the outer points of the previous layer making a little cobweb out and in. Does not look like underextrusion.

So should iGo3D also change the motor and stepper controller of the z axis additionally to the bearings? As it is the second time I send the printer there and I am not keen on sending it a third time again :-)

Thanks,

Markus

[Tomty 4]

Hi,

I've had the same problem and i'm pretty sure i've now fixed it without sending my printer back. Here's a link to my post with a detailed description of what i did to solve it. https://ultimaker.com/en/community/17753-um-2-skipping-layers?page=1&amp%3Bsort=#reply-125974 .

I would be very interested to know if it solves your problem too. And it may save you the hassle of having to send it back.

[markusmaker 2]

Hi,

I've had the same problem and i'm pretty sure i've now fixed it without sending my printer back. Here's a link to my post with a detailed description of what i did to solve it. https://ultimaker.com/en/community/17753-um-2-skipping-layers?page=1&amp%3Bsort=#reply-125974 .

I would be very interested to know if it solves your problem too. And it may save you the hassle of having to send it back.

 

Hi Tomty,

thanks for your tip. Would it be sufficient to use WD-40 on the rods and let the bed slide up and down? Will the WD40 "get into" the bearings then? Or do I need to remove the bearings from the rod?

Kind regards,

Markus

[markusmaker 2]

Sorry missed one question:

If I turn off the UM2 I cannot move the bed by hand - I need to turn the z-axis manually to move it. I read quite often that it should be possible to move it by hand easily. I feel quite some resistance so I did not dare to move it up.

[gr5 2,167]

You need quite a bit of force to raise the bed - about the same amount of force required to lift the printer off the table. Grip the bed using BOTH hands with your fingers under the bed near the very back where it attaches. Once it starts moving it doesn't take much friction to keep ti going.

WD40 has powerful cleaners in it that are very bad to leave in/on the bearings/rods. WD40 should only be used to clean - not lubricate. You need to wipe most of it off after you are done. So only use WD40 if you take the two linear bearings completely off the rods out and you can get it pretty dry before putting it back together.

[markusmaker 2]

You need quite a bit of force to raise the bed - about the same amount of force required to lift the printer off the table.  Grip the bed using BOTH hands with your fingers under the bed near the very back where it attaches.  Once it starts moving it doesn't take much friction to keep ti going.

WD40 has powerful cleaners in it that are very bad to leave in/on the bearings/rods.  WD40 should only be used to clean - not lubricate. You need to wipe most of it off after you are done.  So only use WD40 if you take the two linear bearings completely off the rods out and you can get it pretty dry before putting it back together.

 

Ok understood. Then I was to gentle :-) Thanks.

[Tomty 4]

Hi Markus,

You will need to remove the bearings from the rods as they are sealed (this unfortunately means removing the rods too.) You have to take the rods out from the underside which is a pain. It's definitely worth it though. I used to have nearly half my prints failing and since doing this I have printed about 15 things and all turned out perfectly so I believe this has solved the problem.

[markusmaker 2]

Hi Markus,

You will need to remove the bearings from the rods as they are sealed (this unfortunately means removing the rods too.) You have to take the rods out from the underside which is a pain. It's definitely worth it though. I used to have nearly half my prints failing and since doing this I have printed about 15 things and all turned out perfectly so I believe this has solved the problem.

 

Thanks, when the printer is back and the problem still exists I will definitely give it a try.

[stanimal 0]

hello i made a feedback

for me the solution is change the strong of the table spring

for me it's ok

[neotko 1,417]

I had today this problem as I was going to finally finish the setup of one of my umo+ and it was solved by using a bike grease remover spray on the z rod to clean it and the applying some grease for bike chains. Now it doesn't jump while going down/up.

[WTFockewulf 21]

Ok guys, I am starting to lose it... Sent the UM to igo3d. They serviced the printer and sent it back. Because of an adress mixup this took over three weeks.

Delivered today, checked the service note which said "PTFE changed, test print OK".

They did not check my z-axis Problem. Testprint today and guess what...

Same problem again, missing layers @ 18mm

This is getting really really really annoying.

[WTFockewulf 21]

FWIW, I tried all my test files again.

The ones with CURA 15.04.02 and CURA 15.06.01 BOTH have the fault at the same height.

I tried the files from slimplify3d with the 30mm/s Z Axis speed with one and two perimeters and one with one perimeter and absolutely no infill. All three turned out fine.

I will contact igo3d again but will print using simplify to get the most important prints done before the holidays.

Edited December 19, 2015 by Guest

[markusmaker 2]

Hi WTFockewulf,

my printer came back from igo3d and they exchanged to bearings. Can you please send me your testfiles? And which material / temps you used?

Thanks.

[gr5 2,167]

Tell them you'll change the parts yourself and then you won't have to wait a few days for it to get fixed and it will save them lots of money on shipping.

[WTFockewulf 21]

ok guys, thanks again for all the input. Although its not really fixed, I am at peace with my UM2. Using GCode with adapted Z Axis speeds eradicates the fault completely. I just have to accept that I cannot use CURA (unless they introduce custom Z Speeds anytime soon).

The UM has been printing for almost 100h nonstop since returning from igo3d and I have not had a single failed print. If someone is interested in a working gcode generated by S3D to check their printer let me know.

...and who said you can't print any proper christmas tree decorations on the UM?!

[neotko 1,417]

I'm interested on that gcode s3d. After cleanning the z rod, realigning the hole bed two times, I thought that I got rid of the problem but there's a point where it still fails at certain speeds.

[neotko 1,417]

Hi... Maybe someone can give me their input to my bed problem. At first I though was fixed but nowayjose

 

Every 'tick' it's the Ulticontroller going down 0.1mm, when the bed it's about to jump the sound 'chokes' and then it jumps.

The bed consistently jumps down after passing from 6-7mm and sometimes, mostly always at 10-12mm.

Thinks I have tried:

- Grease chain removed the Z axis (the one of the motor) to fully clean it and then reapplied the grease.

- Disassembly the linear bearings and do the full align procedure. This one I have do it three times (not counting the first when I assembled it)

- Took out the Z lead screw and did spray it with grease cleaner. After fully dried reapplied some grease.

The most weird think it's that the Z lead screw (the brass thingy) 'woobles'. Check the end of the video, that's what happens when pushing the bed from the bottom with the motor lock.

My other 2 umo+ work perfect, no problem, so I'm confident on my assembly skills about the bed... Also the other two umo+ beds don't show that 'wobble' when pushing them from the bottom, their z nuts don't show that much movement at all.

I know this posts are about um2, but since umo+ uses the same bed...

Edited December 27, 2015 by Guest

[gr5 2,167]

that last part - I think that's the main problem! Do the other to printers have "play" like that? I think you can fix this printer by adding a heavy weight - maybe a brick - to the back of the bed. Suspended below. That will eliminate that play.