Underextrusion - Can't print anything

[aroth 1]

My UM2 has gone from being able to print most things relatively easily to not being able to successfully print anything at all. It seems like there may have been a gradual dropoff in performance, as when I first started noticing issues the printer would start showing progressively worse underextrusion the longer a print ran (initial layers would be fine, but subsequent ones would get worse and worse).

Now, however, the printer can't even get past the first layer of a print. It also seems to have become rather prone to clogging. Here's the first such clog that I encountered:

Clearing that clog didn't fix anything (well okay, the printer want from zero extrusion to some extrusion, but it's still far from usable). I've disassembled the hot end, and can't find any obvious problems (the nozzle itself is not clogged), apart from that the white plastic part looks a bit scorched and deformed:

 

 

Is this normal? If not, could it cause the sort of issues that I'm seeing? And more importantly, how can I fix it?

If it helps, I'm using https://www.youmagine.com/designs/alternative-um2-feeder-version-two, and have tried every possible adjustment with it (from screw fully tightened to fully loosened, at half-turn increments). It makes no difference what settings I use (as opposed to prior to the start of the issues, where there was a wide range of adjustments where I could get a successful print of the 10mm^3/sec extrusion test) or what filament I load. Most of my previous printing was done at 210 degrees, though with the printer in its current state, I find that in order to get any extrusion at all I need to set the temperature to 230. All printing has been done using PLA only.

 

[kris 29]

The PTFE bushing does not look good to me. I would suspect it is not up for the task anymore. Have you considered replacing it? The new ones are glass fiber reinforced and have a much better endurance. In order to get one I think you need to get in touch with customer support.

 

[Dim3nsioneer 557]

The PTFE bushing does not look good to me. I would suspect it is not up for the task anymore. Have you considered replacing it? The new ones are glass fiber reinforced and have a much better endurance. In order to get one I think you need to get in touch with customer support.

 

Or you buy it directly from the UM webstore as some UM2 parts including the PTFE bushing are now listed there...

edit: of course, if you're UM2 is quite new it makes more sense to contact support to get a new PTFE bushing for free....

 

[aroth 1]

edit: of course, if you're UM2 is quite new it makes more sense to contact support to get a new PTFE bushing for free....

 

Yep, new part is on its way.

In the meantime, I removed the excess lip from the PTFE coupler and put it back in the printer. I'm still a bit at a loss with respect to what's going on with it.

When I start a print now, the filament tends to flow quite nicely during the initial 'priming' step (where the printhead is held over the left corner of the buildplate and some material is allowed to extrude). But then the flow tapers off to almost nothing as soon as the print actually gets started. I've checked my buildplate levels several times, and that doesn't seem to be the issue.

If I manually push the material through the feeder while it is printing, I can get better results. This shot is fairly illustrative:

The more-solid part in the middle is from when I was manually pushing the filament through. The areas above and below are what I get when I leave the printer to its own devices.

Is there anything I can try while I wait for the new coupler to arrive? I get the impression that there's probably a more serious issue at work here.

 

[Blizz 53]

aroth: I think you are posting your pictures private, 'cause all I can see here are "image not found" boxes.

 

[aroth 1]

Actually I'm hosting them on my own Apache instance. It runs on a weird port, so maybe that's why they're not visible for you? Here's a direct URL to one of them:

http://aroth.no-ip.org:65534/DSC00540_crop.jpg

Does that work for you?

And also, is there a way to post pictures directly to the forum so that I don't have to drop them on my own webserver? I looked around for such an option to begin with, but wasn't able to find one. There's the 'My Media' button, but when I click it I have no options to actually add/attach anything.

 

[Blizz 53]

Does that work for you?

 

No, unfortunately not.

 

 

And also, is there a way to post pictures directly to the forum so that I don't have to drop them on my own webserver?

 

You can use the forum gallery. Just click on your username at the top and then pick "My gallery" (right bottom).You can add pictures there and then use the My Media button to paste them into your posts.

It's a bit cumbersome, but it is how it is

 

[kris 29]

Aroth, did you clean the nozzle? Even if the PTFE bushing looks bad, you might simply have a clogged nozzle.

 

[aroth 1]

You can use the forum gallery. Just click on your username at the top and then pick "My gallery" (right bottom).You can add pictures there and then use the My Media button to paste them into your posts.

It's a bit cumbersome, but it is how it is

 

Wow, counterintuitive. Even with your instructions it took me a couple of tries to find it. I'm bookmarking your post.

Also I've edited the previous posts to use the gallery images.

 

Aroth, did you clean the nozzle? Even if the PTFE bushing looks bad, you might simply have a clogged nozzle.

 

Not particularly thoroughly (I found a small needle and verified that I could poke it through the hole in the nozzle), as I could always push filament through if I tried.

I'll give this a try now and see if it makes any difference:

https://www.ultimaker.com/spree/uploads/113/original/Ultimaker_2_Atomic_Method.pdf

 

[aroth 1]

I went through several 'atomic method' iterations:

 

...and now the printer works much better:

 

 

That's not the best extrusion test I've ever had, but that run was done fresh after cleaning the nozzle and without attempting to optimize the feeder tension for the green filament. At least the printer is usable again. I was beginning to think I'd never get it back.

 

Now it's back to the more mundane 'trying to get the first layer to extrude perfectly uniformly across the entire buildplate and stick nicely without covering the thing in glue' type issues.

 

Edit: And the next followup question is, I see a number of resources which indicate that it's important to have a small gap between the PTFE coupler and the metal part that it slides into. Like what's shown here:

 

 

However in my printer the PTFE coupler sits flush with the top of the metal part (and I think it has always done so). I cannot force there to be a gap there, as the spring just pushes the parts back together again.

 

Is this an issue, and if so, how do I ensure that the appropriate gap is maintained between the PTFE coupler and the metal bit?

 

[Blizz 53]

That is how it is supposed to be, mine is like that as well.

I do get the impression (but it might be due to the picture) that yours is not entirely parallel to the metal part.

If the path somehow has too much resistance because of that it could also explain the underextrusion...

 

[aroth 1]

After cleaning the nozzle and dialing in the feeder tension:

Welcome back, Ultimaker 2! You're a delicate and yet strangely robust kind of beast.

Edit: And why isn't the gallery image being thumbnailed like normal?

 

[IRobertI 520]

You increase that distance by tightening the metal ring that the PTFE part sits in. You insert a small screwdriver or similar into one of the holes and turn it like a screw (you might need to heat the print head for this to work). This will cause the nozzle to move up or down depending on which way you turn it. This will in turn push the PTFE up. But I wouldn't touch it since it looks like your printer is working fine now. Don't fix what aint broken