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calimero

UM2 : Partially clogged nozzle ?

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Hi everyone,

A few days ago the nozzle of my UM2 got completely clogged halfway through a 18-hour print.

When I woke up and went to check how the print was going (approximately 3 hours from the estimated end), print head was hovering approximately 3 or 4 cm above the print.

It looked like extrusion had just been disabled with the print looking very decent.

Anyway I decided to try the heat up/cool down/pull out filament method to clear the nozzle. I then tried using a small 0.30mm drill bit (smooth end, not the drilling side) and ended up with PLA oozing around the drill bit. But the nozzle would still not clear. Moved to a 0.40mm drill bit with no better luck.

I then decided to take the printing head apart. I left everything connected so that I ended up with the fans, head "frame" and nozzle dangling around. I headed the head up to 200° and using a bronze brush I managed to clear the nozzle by getting one or two bristles in the nozzle. I could now see through the nozzle.

Once everything was put back together, bed was leveled (the type of paper I use is probably on the thick side because I need to have the nozzle almost scrape it to get some decent first layer adhesion)

I printed for 15 minutes a 260° to try and clear leftover gunk.

But it seemed the nozzle was not completely clean. When extruding (using the "Move material" feature from the maintenance menu), PLA would curl right when exiting nozzle. I read somewhere that this is typical of partially clogged (or unclean) nozzles.

Anyway I decided to try again my 18 hour print. Actually more like a 23 hour print. I decided to use meshmixher to generate support structures. While meshmixer's light "tree" would help cut printing time I decided to print with 0.1mm layers and 100% infill which increased printing time overall.

Here's what I got after 23 hours:

spaghetti.jpg

Some of meshmixer's support "trees" just collapsed. I suspect the "curling" caused such failures ?

As you can see there's a lot of "spaghetti extrusion".

Surprisingly the print itself ended up very decent even with the failed support structures. I'm pleased with meshmixer even if the print failed to some extend. I was able to just snap the support "trees". Some minor sanding will clean things up.

Before the clogging I had been able to print some decent "bridges" which I suspect would now fail.

- Is this caused by a partially clogged/dirty nozzle ?

- Should I try a few more head/cool/pull cycles to try and get the nozzle clean ?

- How can I take the nozzle completely apart (disconnect it from the print head) so that could completely clean up the nozzle ? (burn gunk away with my gas kitchen stove ?)

Thanks for your help.

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1) Be aware that you can continue a failed print even after many hours. Just don't let the heated bed cool or the part will pop off:

http://umforum.ultimaker.com/index.php?/topic/4213-ideas-for-recovering-failed-prints/?p=34788

2) With normal curling, when you do "move material" the first bit of material curls and touches the nozzle. This is normal. With severe curling, you pull that material (maybe 50mm worth) and force it to hang down, but when you extrude a little more it curls again! In other words 50mm of .4mm diameter hanging filament should be enough weight to prevent curling. If not you should clean your nozzle tip.

The easiest way to clean the nozzle tip is with a steel needle. I recommend purchasing either hypodermic needles (check the diameter before ordering) or acupuncture needles. You scrape the inside of the nozzle tip around in a few circles while the filament is at 180C or hotter.

The hard way is it to take it apart and put it in a glass flame and burn away all the PLA and ABS (powder from the black feeder that ends up in your print head) and dust. Then soak in acetone for an hour. Don't heat it so much that the nozzle melts.

Please add your country to your profile location in case someone is in your country and has a supplier suggestion (france?)

 

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1) Be aware that you can continue a failed print even after many hours. Just don't let the heated bed cool or the part will pop off

 

Will try that some day. So far I don't have a huge volume of parts to print so I can start over from scratch. I also updated a few things in the model (the lower half of the print let me test a few things).

 

 

2) With normal curling, when you do "move material" the first bit of material curls and touches the nozzle. This is normal. With severe curling, you pull that material (maybe 50mm worth) and force it to hang down, but when you extrude a little more it curls again! In other words 50mm of .4mm diameter hanging filament should be enough weight to prevent curling. If not you should clean your nozzle tip.

 

What you describe is what I had when the printer was new. Now, after unclogging it tends to curl much more.

 

 

The easiest way to clean the nozzle tip is with a steel needle. I recommend purchasing either hypodermic needles (check the diameter before ordering) or acupuncture needles. You scrape the inside of the nozzle tip around in a few circles while the filament is at 180C or hotter.

 

I'll try again with my bronze brush. And maybe some more heat/cool/pull.

 

 

The hard way is it to take it apart and put it in a glass flame and burn away all the PLA and ABS (powder from the black feeder that ends up in your print head) and dust. Then soak in acetone for an hour. Don't heat it so much that the nozzle melts.

 

There are two wires coming from the nozzle assembly. I assume one is power the other is the temp sensor ?

How do I disconnect them ? Are connectors higher in the mesh ? I didn't see anything after I had unscrewed the nozzle assembly from the frame.

 

 

Please add your country to your profile location in case someone is in your country and has a supplier suggestion (france?)

 

France indeed.

I'm googling needles. I've found some acupuncture 0.3mm needles.

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Well I still have a lot of curling, more than I remember when I first got the printer.

I'll try a few more passes of "AtomicBob unclogging" but it looks like I'll have to take the hot end off the printer and "burn" out any partial clog. Or worst case scenario try and get a replacement unit from UM.

How can I disconnected the nozzle ? Last time I disassembled the printing head I let the hot end just dangle. Is it connected somewhat higher in the mesh among other cables ?

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