UM2 — Terrible Prints — Don't know where to start

[crudo 0]

I am new to home 3d printing.

 

I've inherited a rundown UM2 from my work. It had not been used in a few years, dusty and miss-aligned. I tried my best to bring it back to its former glory but so far I have not managed to get high-quality prints that have fine details.

 

The work that I have performed so far:

• tightened up all case screws
• cleaned up and reassembled feeder
• cleaned up and reassembled hot-end
• tensioned long and short belts
• aligned axis with alignment tool
• greased rods and z-screw

 

My setup:

• Cura 4.1
• Olsson Block
• E3D 0.6 Nozzle
• esun black PLA 3mm

 

If I print simple shapes the prints come out pretty good. When I print things that have fine detail I get what I think is a lot of ghosting or ringing. I am also having major retraction issues.

 

Below are a few test prints — any guidance on how to troubleshoot my issues would be greatly appreciated.

 

 

 

 

Edited June 4, 2019 by crudo

[crudo 0]

I've changed to a new spool of PLA from MatterHackers, I remembered that I had no idea how old the black PLA that I was printing was. I just printed a benchy with very mediocre results. I am also attaching my GCODE in case there are clues in there. 

 

Thanks for your help!

 

UM2_3DBenchy.gcode

[gr5 2,265]

Well first of all make your walls thicker - I see the infill showing through so assuming you have a 0.4mm nozzle then set line widths (all of them!) to 0.4mm and make the shell/wall 0.8 or 1.2mm thick.  This looks like the walls is only 0.4 thick.  Then if the infill still shows through there is a parameter to make it print the outside first (not the default).  This can help quite a bit also.

 

Most issues, 90% of issues, get better with slower speed so also try printing at 1/3 the speed you did for this print - just to see what happens.  Think of it as an experiment.  Most printers let you adjust print speed aka "feedrate %" on the fly while printing so you don't have to print an entire benchy if you are impatient.

 

Finally I see some bad horizontal layers.  This could be many thnings including a crappy quality printer or a dirty Z screw.  For these types of printers quality usually improves if you make the layers thicker so if you were printing 0.1 then try 0.2.  This will also cut your print time by the same ratio (e.g. 2X faster).

 

[crudo 0]

Thanks gr5 — i just finished a print slowing down speed by 50% and acceleration by 50% and this is the result. As you suggested the thicker walls make a big difference. 

 

I am still seeing uneven z issues, as well as ringing. Any other suggestions?

 

I am printing on an Ultimaker 2.

[geert_2 558]

If it is an old standard UM2, chances are that the white teflon coupler on the nozzle is also worn out. If you do a cold pull ("atomic pull"), and it has a huge blob at the seam between nozzle and teflon coupler, it is worn out and needs replacement.

 

See the blob in the white cone below, which shouldn't be there at all.

 

 

It should look straight like the orange cone at the bottom. Obviously, I did these atomic pulls while changing filament color, so they have both orange and white. Yours should have only one color, and no black dirt. If it has black dirt, do multiple cold pulls until the black is removed.

 

I don't know how familiar you are with nozzle cleaning and cold pulls or "atomic pulls"? If not, first search on the Ultimaker site for more info.

 

Next, you could try the alternative and softer method I use on my machines: this doesn't require hard pulling, but only very gentle handling, but it also works well for me. See the manual here (and then scroll down a bit until you find "atomic pull"):

https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

 

 

Also, while on that same page, I would recommend you download and print a couple of these horseshoe clips: they are much easier to handle than the standard clips. These are in PET, but I have also used them in PLA.

 

 

[crudo 0]

Thanks geert_2,

 

I've visually inspected the coupler and it's looks clean and undeformed. But I'll try your method to see what comes up. 

 

Are you suggesting a these steps because you are recognizing something in my prints? Do you have an idea of what's wrong?

 

Thanks!

[geert_2 558]

2 hours ago, crudo said:

Thanks geert_2,

 

I've visually inspected the coupler and it's looks clean and undeformed. But I'll try your method to see what comes up. 

 

Are you suggesting a these steps because you are recognizing something in my prints? Do you have an idea of what's wrong?

 

Thanks!

 

No, it's based on my experience with my own printers. The teflon couplers tended to wear out quite fast if the printer was running on higher temperatures (above 220...230°C). And that resulted in irregular prints and underextrusion. From the outside it can be difficult to see if the coupler is worn out, because that is only at the inside.

 

But there can be other causes of irregularities: irregular friction in the feeding traject also has a lot of influence on these printers. For example, an irregularly wound spool, kinks in the filament, or a spool nearly empty (=bending radius too tight). And also too much play on the Z-axis screw, or dirt. Or a worn out nozzle (=the conic top being grinded off by abrasive filament, or the inner opening got too wide).

 

Further, overhangs often tend to curl up and cause very ugly walls, especially in thin layers. This is far less if you print at 0.2mm or 0.3mm.

 

For me, usually printing slow and cool improves quality, as gr5 also said. This reduces "ringing" and expansion at sharp corners, reduces strings and hairs, reduces the risk of underextrusion.

 

Also, sudden changes in "layer printing time" do often show up as horizontal lines in the side-walls. Maybe this is what you get when it starts printing the deck of the boat? It seems around that height?

 

But in general, although not perfect, your last white boat doesn't look too bad to me.

 

[crudo 0]

Thanks again geert_2 — tonight I will be getting a new Bowden tube and clips. I'll try to install that, and try your cold pull method.

 

I inspected the teflon coupler when I took apart my hot end, and it was still perfectly white and looked undeformed — I'll check again.

 

 

There seems to be some regularity in terms of Z issues — perhaps my axis and screw need deeper cleaning...

[crudo 0]

One more print for reference in case they provide new clues. I printed this PLA at 205C, 50mm/s speed, 1500mm/s acceleration, 12mm/s jerk.

 

 

 

[gr5 2,265]

1500 is pretty damn slow.  I like 5000mm/sec/sec for acceleration and 20mm/sec for jerk.  The lower jerk and acceleration can mess up corners on things like cubes - it slows down too long on corners and leaves a blob.

 

But lower accel and jerk usually help ringing - that much is true.

[crudo 0]

Gotcha. I think the default values on my ultimaker 2 are 3000 for acceleration and 20 for jerk. 

[crudo 0]

What do you think think banding near the sharp corner is about?

[geert_2 558]

That vertical banding is the "ringing" gr5 referred to: the mechanical oscillations of the print head after taking a sharp corner at high speed, due to its weight, play in the bearings, and the rubber drive belts. So, printing slower reduces this effect. You could also try the opposite: printed a lot faster, and see how the effect changes.

 

For the best settings, you need to ask gr5, as I never experimented with these settings.

 

You can also see the effect in the red print below, due to the light-reflections which exagerrate it. For size-reference: the nylon screw is an M4, and filament is 2.85mm. Printed on an UM2 with factory default settings for this, and 0.4mm nozzle.

 

 

Instead of printing whole boats, you could also test these effects on small cubes of 15mm, and then change settings (speed, flow, temp) on the fly via the printer knob, to test the effect. That would cost you less time and less filament.