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adam-behringer

Extruder failures after 4-5 hours

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Hello, we have been using our Ultimaker 1 for several months. The printer is working on smaller parts but failing on parts that take more than 4-5 hours.

Usually, the part prints well for a few hours, then we start to see inconsistent feeding. Sometimes the filament is too thin for a layer or two. This gets worse and worse until the PLA completely fails to extrude.

We have tried different brands of filament, different temperatures, different layer settings. It seems that whatever we do, the behavior is similar. It prints well for 4-5 hours, gets thin, then clogs completely. We have had about 8 parts fail in this way and it is frustrating!

After it clogs, we stop the part, then turn the hot end up to 250 to drain out the clog. After doing that, we are good for another few hours before it fails again.

The photo attached illustrated the problem. You can see that the part starts well, gets worse, and then failed.

If you have any advice, please share. We'd love to get our printer working for large parts.

Thanks!

Adam

fail1.JPG

 

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I've got black PLA (from ProtoParadigm via qu-bd.com) that will be matte if printed rather cool and glossy if printed hot. It's not easily controllable, but I've always used it to determine the optimal print temperature; guessing that matte isn't quite what it's supposed to be.

Layer adhesion is also considerably worse if the particular brand stuff that I use is turning out matte.

Maybe your temperature setting is a little too low? (Need to know what setting you use first...)

 

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How old is the Ultimaker 1? What temperature, speed and layer height are you printing at?

Can you post some photos of your nozzle and heater assembly, and your extruder drive unit on the back of the printer?

 

Adam and I work together, so I am replying to the question from his original post. The machine is two months old. We have printed numerous successful parts on it for the past two month, including successful large parts. The problem seems to be getting worse. As Adam said, we have tried four different types of PLA.

In the print above, we used the following settings:

Temp: 195

Speed: 65

Layer height: 0.15

Shell thickness: 0.8

Retraction: on

Fill density: 50%

2.9 mm diameter on the filament at 100% flow

I will attached a photo of the hot end in the next post.

Regarding the questions on the type of PLA. It is the UltiMachine black PLA.

 

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Well, there are two issues most likely. Firstly, I'd print a lot hotter than that - the matt finish on the plastic shows that you are basically smearing it out as a paste, rather than allowing it to flow in a more liquid form. 0.15mm layers at 65mm/s isn't lightning fast - it's about 4mm³/s; which is about in the middle of the operating range for the UM1. However, I'd be inclined to print those sort of speeds at 220 or 230ºC. The plastic will flow much better.

Secondly, it looks like your head is mis-assembled. There should be an exposed neck of bare metal tube between the brown peek part and the aluminum block. This is to help with cooling and prevent thermal creep. Without it, over time, heat can travel up into the colder parts of the assembly and begin to soften the PLA enough to cause feed problems.

So you need to back the brass tube out of the top heater block a bit more, and then screw the nozzle further in, so that the nozzle and the brass tube still meet inside the block, but the block is further away from the PEEK insulator.

 

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Thank you, Illuminarti. I just increased the temp and will let you know the outcome. What is the cubic mm/s range we should shoot for in the future? Do you have any suggested guidelines for temps vs volume of PLA per second?

I'm also attaching a new photo of our hot end. There is a little more distance between the heating block and the PEEK than it appeared in the first photo. That said, there is less than there was. We adjusted it after these issues starting happening. Originally, our nozzle was screwed completely into the heater block, and the brass tube was screwed in as far as it could be to contact the nozzle. There were no threads showing on the brass tube, as stipulated in the assembly instructions.

Hot End 2

 

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See this:

http://www.extrudable.me/2013/04/18/exploring-extrusion-variability-and-limits/

You'll need to adjust for the larger nozzle that I had on the printer when I did the tests, but in general you can just scale everything proportionately. The upper limit with the standard nozzle and high temps is somewhere around 8-10 cubic mm per second.

Unless you're printing very detailed parts with lots of overhangs and separate islands on each layer, I'd be inclined to just set the temp to 230, and only bother going lower if you experience a lot of stringing or blobs on a particular print. I pretty much always print at 230.

 

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It's ok to have a tiny gap between nozzle and block, so that you have room to tighten it against the end of the brass tube to get a good seal; but it should be as small as possible. the airgap above the block is critical to getting consistent results.

Mostly, though, I just think you're printing too cold.

The other thing you might check is that your fan isn't blowing on the tip of the nozzle - perhaps because the fan shroud slipped/melted/broke.

 

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The other thing you might check is that your fan isn't blowing on the tip of the nozzle - perhaps because the fan shroud slipped/melted/broke.

 

You are good! I found yesterday when I took the hot end apart that the fan had cracked, so I rotated it around to ensure the long thumb-screw rods are going through solid holes. The part is printing now and looks much better already at the higher temp, so I think you are right on about our printing temps. The fan may have been a contributing factor...

 

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I think you've got a solution, but I'll throw this in just in case you need it: I had similar problems a while back, but the head was getting blocked almost every print. I was about to throw the bloomin' thing out the window, but thankfully I didn't.

I found that you can get a sort of partial blockage in the head (where PLA gets between the bowden and the hot end, and then cools down). I was finding that it seemed to cause so much friction that molten PLA wouldn't move so well and prints would sometime go really thin and recover, or just stop extruding altogether.

The V1 head suffers from the 'popping' problem where the junction between bowden and hot end gets material forced into it, which eventually pushes the bowden out of it's clamp. It doesn't sound like you're quite there yet, but it could be contributory (and raising the temperature will help stop the material hardening when it gets pushed through the junction).

If you do find yourself with popping problems, then you can print your way out of trouble with a Pop-Stop (https://www.youmagine.com/designs/ultimaker-bowden-pop-stop). This allows you to get a really tight seal between bowden and hot end without needing some super-strong bowden clamp. I think this is sort of the same design used in the V2 hot end (although I've yet to buy one, so can't say for sure!).

 

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