UM2+ Issues not solved after replacing many parts. Would greatly appreciate guidance from the community

[hobe12 0]

Hello,

 

My UM2+ is having issues which seemed to be pointing towards under-extrusion. As such, after working with UM support and consulting countless posts on this forum, I ran through the normal troubleshooting, cleaning and lubing procedures and replaced parts (see below), I regret to say that the problem persists.  My layers are uneven and my edges are not straight (see below). I rely on this machine and it's been down for almost 2 weeks. I would greatly appreciate help from you experts out there. 

 

Replaced parts:

• bowden tube and collets
• nozzle sensor
• tfm coupler
• hot-end isolator
• heater block
• new nozzle 

 

Thank you,

Sam

[gr5 2,002]

This looks like alternating underextrusion and overextrusion.  The lines that stick out - do they go all the way around?  Or are they only on one side - does the same exact line continue all around?  If not then it's probably a issue with play just X or just Y axis.

 

But this looks much more like a Z issue.  If the Z axis (up and down) doesn't move far enough then there isn't enough space for the molten filament and it sticks out like this.  This may happen for one or 2 layers and then suddenly it moves farther (catches up) and you get a layer of underextrusion.

 

One test for this is to put a brick or other heavy weight on the bed.  It should get better.

 

Try cleaning the Z screw.  Just do a quick cleaning to see if it's better.  On the UM2 it's pretty easy to unplug the Z stepper and remove 4 screws and the entire stepper/z-screw assembly all slides out the bottom of the printer.  Then you can clean it much better over newspaper using WD40 and rags.  Then when it's clean and dry, add just one drop of grease.

[hobe12 0]

Thanks for the quick reply. The lines do continue all around so I will try what you suggested and report back.

[hobe12 0]

@gr5 - I'm trying to remove the z stepper motor. Is it possible to remove the wires from the stepper directly or do I need to follow the wire to the main board(s)? They aren't sliding out from the motor easily and I don't want to force it if thats not the correct way. Many thanks!

[fbrc8-erin 267]

1 hour ago, hobe12 said:

@gr5 - I'm trying to remove the z stepper motor. Is it possible to remove the wires from the stepper directly or do I need to follow the wire to the main board(s)? They aren't sliding out from the motor easily and I don't want to force it if thats not the correct way. Many thanks!

 

The wires are permanently attached to the motor. If you want to take the motor out, you'll need to unplug it from the main board. That said, I usually leave the motor in the printer when cleaning the Z-screw unless it's got a lot of debris in it or there was some sort of accident (like broken glass).

[gr5 2,002]

I think it's only 2 screws to remove the cover on the main board.  It's a little tricky removing the connector though without seeing what you are doing but I've done it so many times I leave the board mounted and in place.

 

Erin is the expert so you should try it her way.  She has assembled and repaired a lot of UM printers.

[hobe12 0]

Thank you both for the help. Tried (again) cleaning and oiling/lubing with no luck.

 

Erin, I will be shipping you my printer soon as the box arrives.

[gr5 2,002]

If cleaning doesn't make any difference then it probably wasn't dirt.  There can be many issues with the Z screw, the Z nut, or the 2 Z rods.  My guess is the Z nut.  Or something completely unrelated to Z such as a temperature issue where there's something wrong and the nozzle temperature varies randomly.

[hobe12 0]

I tested the rod bearings and they looked good. Z nut something I can fix/replace? Thank you!!

[Torgeir 212]

Hi hobe12,

 

When I looked at your picture, I'd also think about a Z shaft problem.

However, in the upper part of your print there's some other issues lead me to think that this "might" be a filament issue, a filament that has absorbed some water.

Filament might have sectors that's worse at places, where vapor force molten filament out of nozzle and the outcome of this may differ a little due to temperature used. If printed some hot it makes like a hole, at a little lo temperature just making blobs along a layer etc. To me, it looks very much like the filament is contaminated with water.

Also, often the filament become some brittle if this occur, brake very easy at a certain angle.

 

Just my thoughts.

 

Thanks

Torgeir

[hobe12 0]

Thanks for the tips, @torgeir.

 

I'm using brand new filament and have tried several with no change so I don't think that's the issue. Here are tests print from a g-code file UM sent me. 

[Torgeir 212]

Hi hobe12,

 

Sometimes a picture says a thousand more than a word.. 🙂

This picture of your print really does.

When the printer finished the "big" rectangular block, the remaining the round part improved drastically, the hex one not so much but better, -but better! I'll say this is a heat transfer problem. The heath transfer between the heater/the block might not work very well, or the transfer between nozzle/ block is suffer.

IE. heater hole to wide.. Or bad thermal transition between nozzle and block.

Or a heater that cannot deliver enough heat...

 

@gr5 said temperature problem, sure this match.

 

Well, I am using copper paste when installing heater and sensor. The temperature at my nozzle (see in advanced menu) never change more than 1 deg. C up or down!

 

I am even using a little copper paste on the coil of the nozzle to keep good thermal contact. But do not overdo this!

 

Thanks

 

Good luck

 

Torgeir

 

 

 

 

[gr5 2,002]

I'm skeptical that it's temperature as with this smaller model it looks like it would have to change temperature very fast.  But it's easy to check - watch the temperature on the UM2 while it is printing and make sure it doesn't vary by more than 4 degrees from coldest to hottest.

 

So the other thing that happens when it is only printing the 2 towers is that the printer slows down.  A LOT.  Probably 1/3 the speed.  Because of a feature called "minimum layer time".  I bet if you drop the speed by 3X in Cura the quality will go up a lot.