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ScarletImpaler

UM3 dirty/blackened first layers.

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Hello, 

Been having trouble with my UM3 producing nasty first layers, with either some material left from previous filament mixed in, or blackened spots and streaks.Pictures attached. 

I've been using just standard PLA, all ColorFabb. Nozzle and glass bed is completely clean, and the rest of the print comes out perfect. I've tried googling the problem, but nothing was coming up. 

 

What can be causing this? And how do I fix this? 

 

Thank you.

UM3 first layer problem 1.jpg

UM3 first layer problem 2.jpg

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I don't think there's much you can do about this. As you say, this is caused by some old material that's stuck in the nozzle.

 

A few things that can improve this:

  • This probably speaks for itself, but make sure your nozzle is clean on the outside.
  • When switching materials, let it extrude enough material and make sure the color has changed completely. 
  • Use different cores for different color groups (eg have a core for darker colors and one for lighter)

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4 minutes ago, ScarletImpaler said:

Yes, I'm cleaning the nozzles, inside and out, and yes I make sure the extruded plastic becomes the new color when I do filament changes.

I shouldn't have to buy different print core for different color groups, its a $3000+ machine, shouldn't be having this problem to begin with. 

The machine is not the issue. I am willing to bet it is something funky with the nozzles. Not to nitpick, but you say cleaning inside, but to what level? Just hot pulls? Hot and cold pulls? It is possible that the core has some yuck in it from manufacturing.

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Is it possible there's bits of different color filament in your bowden tube? Sometimes a bit of ground filament can end up in there. If you're switching from a dark colored filament to a lighter one, you might want to inspect your bowden tube before you start your print and make sure no ground filament has been carried up. You can clean the bowden tube by removing both ends from the printer, putting a little tissue or paper towel in one end, and pushing it all the way through with a piece of filament. It should basically grab any debris. 

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The big pink/purple blob goes over *multiple* print lines, so it clearly is something that is dropped on the print from the *outside* of the nozzle. Problably some junk from a previous material that was still stuck on the outside. Might have been a bit stuck higher up, outside of direct view? Or some debris picked up by the nozzle while traveling around, then molten, and then deposited? Idem for the S-curved dark spot in the first pic.

 

The tiny dark flakes along print lines, in the second pic, look more like burnt residu from the inside of the nozzle. This would probably require multiple atomic pulls to remove, and a lower printing temp (to prevent the material from burning). Printing temp is very close to burning temp, so you cannot totally avoid burnt residu, but you can reduce it by reducing printing temp and speed.

 

Generally, in my experience (with two Ultimaker2 printers): big blobs, often light brown discolored = accumulated material on the outside of the nozzle that sags and then gets deposited on the model. Tiny, thin black flakes = burnt residu from the inside of the nozzle.

 

To do more gentle atomic pulls, feel free to have a look at my manual (scroll down a bit on that page): https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

 

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On 11/01/2018 at 2:39 PM, ScarletImpaler said:

Yes, I'm cleaning the nozzles, inside and out, and yes I make sure the extruded plastic becomes the new color when I do filament changes.

I shouldn't have to buy different print core for different color groups, its a $3000+ machine, shouldn't be having this problem to begin with. 

No, you don't, but you need to do maintenance like you need to do with any tool. I bet your car was more expensive and I'm pretty sure you still have to change oil and maintain it, right?

 

Cleaning the outside and inside of the nozzle (as well as cleaning the rest of the machine and make sure it's lubricated) is basic maintenance which will prevent this problem.

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9 hours ago, geert_2 said:

The big pink/purple blob goes over *multiple* print lines, so it clearly is something that is dropped on the print from the *outside* of the nozzle. Problably some junk from a previous material that was still stuck on the outside. Might have been a bit stuck higher up, outside of direct view? Or some debris picked up by the nozzle while traveling around, then molten, and then deposited? Idem for the S-curved dark spot in the first pic.

 

The tiny dark flakes along print lines, in the second pic, look more like burnt residu from the inside of the nozzle. This would probably require multiple atomic pulls to remove, and a lower printing temp (to prevent the material from burning). Printing temp is very close to burning temp, so you cannot totally avoid burnt residu, but you can reduce it by reducing printing temp and speed.

 

Generally, in my experience (with two Ultimaker2 printers): big blobs, often light brown discolored = accumulated material on the outside of the nozzle that sags and then gets deposited on the model. Tiny, thin black flakes = burnt residu from the inside of the nozzle.

 

To do more gentle atomic pulls, feel free to have a look at my manual (scroll down a bit on that page): https://www.uantwerpen.be/nl/personeel/geert-keteleer/manuals/

 

But now I wonder, if heat is a problem, and getting close to burning, then why aren't burnt marks on any other place than the first layer(s). But I'll try to reduce first layer heat and see what happens. And I do cold and hot pulls to clean inside, and move cleaning filament around the nozzle when heated to remove anything from there. 

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9 hours ago, IRobertI said:

No, you don't, but you need to do maintenance like you need to do with any tool. I bet your car was more expensive and I'm pretty sure you still have to change oil and maintain it, right?

 

Cleaning the outside and inside of the nozzle (as well as cleaning the rest of the machine and make sure it's lubricated) is basic maintenance which will prevent this problem.

And I do that maintenance, like I said in my posts. Cleaning properly, and its still giving me this problem. Your comments that are ignoring my input are unhelpful.

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19 minutes ago, ScarletImpaler said:

And I do that maintenance, like I said in my posts. Cleaning properly, and its still giving me this problem. Your comments that are ignoring my input are unhelpful.

 

Have you cleaned the inside of the bowden tube and inside of the feeder? I know you mentioned cleaning the nozzle, but the feeder and bowden tube are important too.

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Indeed, if there is burnt residu in the nozzle, usually these flakes come loose when starting a new print, thus on the first layers only. I am not sure why that is, maybe because the cooling cycle between prints dislodges it? But I have often noticed that too.

 

Sometimes I have to do 5 or 6 atomic pulls in a series before the dirt comes off (on my UM2, I don't have an UM3). Some materials work better for atomic pulls than others, for example Ultimaker Pearl PLA works well for me; it's a bit more sticky and glues better to the residu. Try whatever filament you have laying around. And before pulling, let it cool down long enough. If I print full-time, I do a series of atomic pulls once every week as routine maintenance (my gentle version, with rotating but without brute force). And more if necessary, for example when changing colors.

 

Maybe you could also inspect the nozzle under a magnifying glass or microscope, to see if it is defective and leaks from halfway? This could happen on an UM2+ when the nozzle is not screwed-on tightly enough. I don't know if it can happen on an UM3, but if so, it could also explain these things.

 

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On 17/1/2018 at 11:49 PM, ScarletImpaler said:

And I do that maintenance, like I said in my posts. Cleaning properly, and its still giving me this problem. Your comments that are ignoring my input are unhelpful.

 

In my experience with many colors every day is that you need atomic pull after a color change to fully remove the previous color, normal purge doesn’t cut it. 

 

And if you did all, I would check bowden like they said and most importantly:

 

a) Check the feeder bolt of the extruder (it has a small hole to see a bit), if dirty then clean it. 

b) Check the actual filament spool. With faberdashery pink I had 3 spools that had particles of black color inside the filament itself. Ofc they did reimburse me and they send me loose filament to change it. 

 

Last posibility is that the core has something leaking, very rare and improbable but on my um2+ hotends that’s the source of black particles if the coupler is near its end of life. 

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