UM 2 Skipping Layers

[Tomty 4]

Hi,

I recently bought an Ultimaker 2 and i keep getting the same problem, after approx. 10mm it seems to skip layers sometimes and I get gaps in the print however it is random when it happens and never happens in the same place twice. Ive tried various plastics and cleaning the nozzle but still get the same problem. This problem is currently stopping me from being able to print large items due to the fact that 75% of my prints have to be thrown away. I have attached some pictures to show what it looks like. [/media]

Many thanks

-Tom-

Ultimaker 2

Cura 15.06.03 (Mac)

[Labern 775]

This looks like under extrusion.

It can be caused by many things.

Tangles in filament

blocked nozzle

deformed PTFE coupler (prob not this if its a new printer)

Incorrect feeder tension

Wrong size filament or bad roll

along with other causes

If you are a beginner then I would suggest using CURA 15.04.2 for now as it has less bugs.

you could also read through THIS guide.

[DidierKlein 729]

After looking at the link provided by Labern, can you tell us the print settings?

Temp, speeds, layer height etc?

And the material you are using?

[Tomty 4]

Thanks for your response. I have already tried the atomic clean and the filament comes straight off the roll into the printer so i don't think it could be tangled. I will have a play with Cura however and use 15.04.2 for some test prints and try the suggestions on the very helpful link you sent. I will report back once i have tried all of these.

Many Thanks

Tom

[Tomty 4]

Hi,

I'm currently using PLA and the default PLA settings (210 nozzle, 60 bed, 50mm/s, 0.1mm layer height)

[JohnFox 25]

Does this problem only occur after 10mm? It sounds like a problem I had, caused by a problem with the Z axis bearings.

Have you ever put any oil onto the Z axis pillars? If you have, then possibly the balls in the bearings are trying to slide rather than roll. This causes the bearing race to lock up and jam, resulting in the Z axis error.

Try and clean the pillars so there is no oil at all. Then with the power off, raise and lower the print head a few times, trying to feel if there is any sudden friction.

I eventually bought some new bearings, cleaned everything and it fixed the problem.

[Tomty 4]

Hi,

Thanks for your response, yes thats exactly what I get!

I did put some of the green grease on the Z axis screw but none on the pillars.

When I manually raise and lower the bed it seems to move reasonably OK.

I've added a picture to show what I am getting.

[IRobertI 521]

You might also want to look through this part of the guide:

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#z-drop

If it always happens at 10mm I wouldn't expect it's overheating due to excessive current, but if it seems semi-random, that could definitely be the cause and then the fix is simple.

[JohnFox 25]

Looks like a bearing problem to me. That guide that |Robert| refers to is VERY useful. Try the idea of unscrewing a bearing and running it up and down the pillar, maybe the balls have got out of alignment .

[Tomty 4]

Hi,

Thanks for your response, I will definitely try this this weekend (sorry, i've been very busy recently) and hope that that fixes it. I have already lowered the maximum current with no luck. However the guide you have linked will hopefully help solve the problem. I will post my results after testing the different methods.

Many Thanks

[Tomty 4]

Hi,

Thanks for the response, I will definitely be trying that this weekend and hope it works. However the printer is new and only printed approximately 70m of material so i will be annoyed if the bearings have already begun to fail. I will post my results once i've tried everything.

Many Thanks

[Tomty 4]

I printed out a 20mm high bracket last week and again got my ‘missing layers’ problem.  This time it was at 14mm, rather than at the 10mm position as before so the position of these missing layers is showing some variability.  So I decided to take a look at the z-axis bearings.  First of all I manually raised and lowered the bed.  It felt reasonably OK but it is difficult to tell what is ‘normal’ as I have nothing to compare it with and of course you have to back drive the lead screw and stepper motor.  So I set about re-aligning the linear bearings.  Before re-tightening the 8 screws, I removed them all and slid each of the bearings up and down the z-axis rods.  They feel really rather bad to me.  They are rough, notchy and stick/bind at various positions, sometimes needing a noticeable push with my finger to get them to slide further along the rods.  They certainly will not slide down under their own weight.  My printer has had this printing fault since new so maybe I just have a duff pair of bearings in my machine.   I see that the bearings have a shaft seal at each end so I couldn’t add any lubrication to them even if I wanted to (I’ve never added any lubrication to the rods).    I am familiar with how deep groove bearings feel when rough and how smooth they operate when new.  Is this the sort of feel that I should be getting from the linear bearings (ie should they just glide freely along the rod?)  Sure there will be a bit of resistance from the seals but what I am feeling is definitely not from the seals.

John, when you replaced your z-axis bearings with new ones, were they very smooth running on the rods?  Out of interest did you replace the bearings by removing the top of the machine and pulling the rods up or remove the rod ‘stops’ from beneath and drop the rods down?   I think I am going to contact Ultimaker sales as my machine is still in warranty and has never been right since new.

Thanks for your help.

Edited November 15, 2015 by Guest
typo

[JohnFox 25]

When I fitted the new ones they ran very smoothly up and down with hardly any friction. The old ones locked repeatedly.

I removed the top of the machine, ( I think ).

It's worth wiping the pillars from time to time to remove any oil that comes from the bearing themselves.

 

I printed out a 20mm high bracket last week and again got my ‘missing layers’ problem.  This time it was at 14mm, rather than at the 10mm position as before so the position of these missing layers is showing some variability.  So I decided to take a look at the z-axis bearings.  First of all I manually raised and lowered the bed.  It felt reasonably OK but it is difficult to tell what is ‘normal’ as I have nothing to compare it with and of course you have to back drive the lead screw and stepper motor.  So I set about re-aligning the linear bearings.  Before re-tightening the 8 screws, I removed them all and slid each of the bearings up and down the z-axis rods.  They feel really rather bad to me.  They are rough, notchy and stick/bind at various positions, sometimes needing a noticeable push with my finger to get them to slide further along the rods.  They certainly will not slide down under their own weight.  My printer has had this printing fault since new so maybe I just have a duff pair of bearings in my machine.   I see that the bearings have a shaft seal at each end so I couldn’t add any lubrication to them even if I wanted to (I’ve never added any lubrication to the rods).    I am familiar with how deep groove bearings feel when rough and how smooth they operate when new.  Is this the sort of feel that I should be getting from the linear bearings (ie should they just glide freely along the rod?)  Sure there will be a bit of resistance from the seals but what I am feeling is definitely not from the seals.

John, when you replaced your z-axis bearings with new ones, were they very smooth running on the rods?  Out of interest did you replace the bearings by removing the top of the machine and pulling the rods up or remove the rod ‘stops’ from beneath and drop the rods down?   I think I am going to contact Ultimaker sales as my machine is still in warranty and has never been right since new.

Thanks for your help.

 

[Tomty 4]

Thanks for such a quick response.

I'm going to contact Ultimaker and see what they say.

Out of interest did you source replacement bearings from Ultimaker or find them yourself?

Just noticed your location...not to far from me (Perton in Wolverhampton)...small world!!

[Tomty 4]

Many thanks for all the help I received with my 'missing layers' printing issue. I am pretty sure that I have now solved the problem and I understand what the issue has been. I have now printed a fair number of things and all of them without the problem recurring. For anyone else that may experience the same problem (which I have had from day one day of receiving my printer!) I've jotted down a few notes below which may be of some use.

When printing I would regularly find that the print would appear to have a missing layer such that the print could easily be pulled apart. This became a regular issue and was the cause of much frustration as so many of my prints ended up in the bin. JohnFox suggested it could be a sticking z-axis bearing. So I removed the two screws from under the bed and lifted up the cover plate to give me access to the bearings. I removed the four screws securing the first bearing to the bed and slid it up and down the guide rod. It was clearly sticking, binding and jamming - it was not a happy bearing. These are linear bearings filled will many small individual ball bearings that should ensure very smooth linear movement with near zero frictional resistance, so something clearly wasn't right. I then checked the other bearing and it too was just the same. So I contacted Ultimaker and they promptly sent two replacement bearings. Confident that this was the cause of my problem, I removed the first of the two bearings.

Removal of a bearing is done by accessing the underside of the printer. Once the four bearing screws have been removed, all you need to do is to remove the two screws that hold the small black strap over the end of the bearing guide rod. Access to the right hand rod is easy. The left hand rod is a little more tricky as you need to firstly remove the cover for the circuit board and then carefully remove the screws securing the circuit board in place and move it slightly to one side to gain access to the black strap and its two screws. With the black strap removed, the rod can be pushed down through the floor of the printer until the bearing can be slipped over the top of the rod. It is easiest to do one bearing at a time so that the other still supports the bed. Pushing the rod down is a little awkward as there isn't much to grip on to! I put a drop of WD-40 at both ends of the rod and then wrapped a piece of fine wet and dry paper around the rod just above the base hole through which it passes. This provided me with the extra grip needed to get it to move down. Once it starts to move down, the rod can easily be pushed sufficiently through the printer base hole so that the bearing can be removed by sliding it up and off the top of the rod. Don't worry about losing any of the small ball bearings when you remove the linear bearing as they are internally retained and will not fall out!

When I fitted the new bearing, I was very surprised to find that the sticking and binding effect was just as bad. Although I had read that putting grease on the linear bearing rods is not recommended I decided to apply some grease to the balls inside the bearing and try again. Unfortunately this made the sticking and binding effect even worse. I then took the rod completely out from the underside of the printer. I applied a generous amount of WD-40 to the inside of the bearing and repeatedly slid the bearing up and down the length of the shaft. I then slid the bearing off the rod, shook off the excess WD-40 and then repeated this process about 5 or 6 times until the bearing slid freely and easily up and down the shaft. I suspect that the inside of the bearing had some sticky anti-corrosion coating which was preventing the smooth rolling action of the balls. I think that repeatedly applying the WD-40, plus exercising the bearing, flushed out this residue and enabled the bearing to then function as intended. Prior to fitting the bearing and rod back into the printer I applied just a bit more WD-40 to the bearing.

Refitting the bearings and rebuilding the printer is simply reversing the disassembly process. However, the head of one of the fasteners that hold the circuit board in place needed to be restrained in order to tighten it. This meant I had to remove the two screws that hold the vertical cover at the rear left corner of the printer in position. One screw is on the left side of the printer and one at the back near the filament drive unit. The vertical cover can then be lifted up enough to reveal the head of the screw which can now be reached with an Allen key.

So whilst I'm pretty sure now that the cause of my printing problems was to do with the z-axis bearings, I don't think I actually needed new bearings. I just needed to flush out the residue within the bearings with WD-40 a few times until the bearings smoothly traversed up and down the guide rod.

Many thanks for the help I received on this forum, and hopefully I've provided enough information here to help anyone else who is experiencing similar issues.

[UltiChris 1]

 

• I removed the four screws which hold the Z axis' helix bearing on the printing plate. It makes acces and verifying the vertical movement very easy.
  
• To be able to access the last screws holding the circuit board remove the vertical cover in the left corner of the printing cabin.
  
• To unlock a sticky rod I created a "tool" made from a 10 mm nut in which I drilled a 12mm hole. I sawed it in two pieces and sanded the sawing edge:
  
  With the tool and a pair of pliers the rod can be grabbed tight and yet without damaging it.