Vertical walls are wobbly

[relmendorp 0]

Hi all,

Hope you guys can help, I don't get it. There are two recent threads that show similar faults, but neither of those situations are exactly the same as far as I can tell.

I have an Ultimaker 2 that has about 900 printing-hours on it. It's on its second nylon spacer and nozzle since about 200 or 300 hours.

Over the past few days vertical walls have become very ugly. I've greased everything, cleaned the nozzle, leveled, etc. Different filament does not seem to make a change and I use good quality filament. I have been using this feeder for the past 500 hours without problems: https://www.youmagine.com//designs/alternative-um2-feeder-version-two .

PLA, .2mm, 50 mm/s at 220 degrees. There is some slight underextrusion visible on some parts.

Dropping to 210 degrees gives more severe underextrusion:

Help!

Thanks.

Edited October 19, 2015 by Guest

[gr5 2,167]

You are getting over extrusion on some layers and under on others. It could be a bunch of things:

1) feeder issues that change but slow enough that a whole layer is under/over extruded.

2) Temp issues where the temp is oscillating chaotically by at least 20C. You get underextrsusion when cold and over when hot.

3) Z movement issues where the bed isn't moving a consistent distance so you get over extrusion when it doesn't move far enough and underextrusion when it moves too far.

It really could be any of these 3 so you need to eliminate 2 of them. #2 is the easiest to eliminate - you can just look at the temp reading. The actual temp may be 10C off of the reading but if it's oscillating then the reading should do sudden jumps in temp by more than 1C - in other words it might read 210C and then 212C skipping over 211C. This should never happen and indicates the sensor path has a loose/bad connection (usually inside the sensor).

#1 seems the least likely so if you can elminate temp issues that leaves Z issues. Something would be making the Z table misbehave - grab the bed with power off and slide it up firmly (grab with 2 hands near the back on either side). and down. repeat many times trying to feel for stickiness or something weird.

when you say you "greased everything" I hope you only greased the Z screw and oiled the rest. If not remove any grease from the Z rods with wd40 and then re-oil them.

[relmendorp 0]

You are getting over extrusion on some layers and under on others.  It could be a bunch of things:

1) feeder issues that change but slow enough that a whole layer is under/over extruded.

2) Temp issues where the temp is oscillating chaotically by at least 20C.  You get underextrsusion when cold and over when hot.

3) Z movement issues where the bed isn't moving a consistent distance so you get over extrusion when it doesn't move far enough and underextrusion when it moves too far.

It really could be any of these 3 so you need to eliminate 2 of them.  #2 is the easiest to eliminate - you can just look at the temp reading.  The actual temp may be 10C off of the reading but if it's oscillating then the reading should do sudden jumps in temp by more than 1C - in other words it might read 210C and then 212C skipping over 211C.  This should never happen and indicates the sensor path has a loose/bad connection (usually inside the sensor).

#1 seems the least likely so if you can elminate temp issues that leaves Z issues.  Something would be making the Z table misbehave - grab the bed with power off and slide it up firmly (grab with 2 hands near the back on either side).  and down.  repeat many times trying to feel for stickiness or something weird.

when you say you "greased everything" I hope you only greased the Z screw and oiled the rest.  If not remove any grease from the Z rods with wd40 and then re-oil them.

 

Thanks for the extensive response. The under-over extrusion seems logical.

#1 - Does seem the least likely - when I (rarely) run into feeder problems it grinds the filament so that it stops extruding.

#2 - Temperature does fluctuate a bit but within 1 degree C (so 220-219-220-221-220). I have a little door for the front opening to eliminate big drafts.

#3 - I tried this and it does not feel very smooth, but it's more a constant friction than stick-slip. No other Ultimaker 2 around to feel for a difference, but I'll look at it more closely.

Only greased the Z screw and oiled the rest with a drop of sewing machine oil.

The effect seems worse with larger layer heights. 0.1mm seems to print OK-ish on small objects.

[gr5 2,167]

Well it could also be filament that varies in diameter by quite a bit. But I guess it would have to vary by so much that you would see it visually (30% thinner or thicker).

So try cleaning the Z screw - especially where it is inside the nut when the bed is within 5cm from the nozzle - in otherwords especially the top 1/3 of the z screw. Try cleaning it with wd-40 maybe and a rag and maybe a toothbrush or paint brush. Try to get it completely clean and then grease it back up - just one drop of grease should be fine. You use the green grease that came with it? I think any grease is fine.

Does the platform rub anywhere else? check that the platform doesn't touch the spool holder - actually just remove the Damn spool holder - it causes more trouble than it's worth I think. check all around above/below the glass - the entire stage - check to see if it touches something that would make it bounce or jiggle or hang up.

The z stepper controller might be overheating and causing it to be weaker than desired such that some of the microsteps are ignored until it gets to a full step. Maybe remove the bottom cover and put a fan blowing on the printer - it can print upside down just fine so tilt it over a bit so a window fan can blow some air under there for a test print.

[relmendorp 0]

I've removed the Z motor, screw and bolt in the platform. Cleaned it and greased it, but that did not help.

I noticed that the platform did not move entirely smoothly with the Z screw removed. One of the two bearings seems damaged, it does not move smoothly over the axle and tends to jam.

Problem found.

Thanks again!

I'll contact UM support.

[neotko 1,417]

Maybe the calibration of the bed isn't done properly (or the screws ain't tight enough and overtime they went a bit loose) on assembly and that's why it fells hard to move.

Is described on page 34 step C3 of the um2 assembly manual. That could explain the bed to have resistance while going up and down. Ofc it might be just the z screw.

https://github.com/Ultimaker/Ultimaker2/blob/master/um2%20assembly%20manual%20V1.1%20_english.pdf

Edited October 9, 2015 by Guest

[relmendorp 0]

That's a nice manual! Did not know it existed.

Unfortunately it's not just assembly, taken apart, the bearing does not operate smoothly.

These bearings are not expensive.

http://www.ebay.com/itm/LMK12LUU-Square-Flange-Mounted-Linear-Motion-Ball-Bearing-12mm-/141075812645

Edited October 9, 2015 by Guest

[gr5 2,167]

That's great! I set that answer as "best answer". If I'm wrong let me know and I'll remove it as best answer and you can pick something else some day.

[relmendorp 0]

Bearings have been replaced, ordered them through UM support.

Quality of walls have increased greatly. Still not perfect, but quite good. I think this print was a bit too warm.

0.1mm layer height.

[peetersm 124]

Yes big improvement.