PLA not coming out of the nozzle

[carlose_martin 0]

Good day.

I'm having a strange problem with my ultimaker 2 printer.

Yesterday, after replacing a broken heat sensor, I started printing to see if everything was ok.

First print came out beautifully, no problems at all.

Then I left the printer doing an overnight job, only to find out this morning that the printer stopped shortly after finishing the rafts. I retracted the material to see if the nozzle was clogged, but it appears to be ok - I can insert an acupunture needle without problems.

However, I had to cut part of the PLA filament, as it looked like this:

 

The tension indicator is somewhere near a third of the box:

 

The coils of the filament are loose, and if I heat up the nozzle I can make it extrude by pushing the filament manually.

 

However, as soon as I send something to print, the head moves but no material comes out. The third fan is working correctly.

 

I've tried tightening the tension screw, as well as loosening it, but the problem is still there, and I'm at a loss as to what else I can try.

 

Any suggestions?

 

Thanks in advance

 

[kris 29]

Have you tried cleaning the nozzle? It might appear to be OK, but maybe it isn't. I would try that first.

Maybe using the atomic method?

 

[carlose_martin 0]

Kris: yes, I've cleaned the nozzle using the atomic method. I'm not sure what other methods I can use to clean the nozzle. Acetone, maybe?

 

[donmilne 2]

Acetone won't really help - it isn't a solvent for PLA.

What printing speed are you using, and what temperature? A slower print speed and/or a slightly higher temperature may reduce the back pressure from the printhead and reduce the risk of grinding.

Also, it may be necessary to open the feeder to clean out all the grinding debris. Particularly make sure the grooves on the motor drive isn't filled with gunk.

Also, when you can get the printer working again, I highly recommend printing out a copy of IRobertL's replacement feeder. It is so much simpler to tune and to keep clean of debris. It is also easier to see what's going on when something like this happens.

A final thought that occurs is that, once the filament started grinding, the printhead may have overheated. The PLA cooks and causes obstructions, and the PTFE spacer can distort or be plugged.

Take heart: there's a heater at one end, a motor at the other end, and a tube in between. Whatever the problem is, it must be simple.

 

[carlose_martin 0]

I'm currently printing at 50 mm/s, with a temperature of 210º.

The printer is working again. I withdrew all the material and tightened the tension screw until the indicator was in the middle. I'm currently printing the leveling circles, but as soon as that works, I'll print the new feeder system as per your suggestion.

Thanks!

 

[gr5 2,173]

DonMilne has great advice! Read it twice!

 

I'm currently printing at 50 mm/s, with a temperature of 210º.

 

It matters on layer height also. With .2mm layer height that is 50*.4*.2 or 4mm^3/sec which is fine at 230C but too fast at 210C. I have a graph of max speeds and I never print faster than half the speed of this graph. Also keep in mind that the lower layers print slower and it speeds up as you go so that's probably why it was fine at the lower layers. I recommend you keep the speed at 50mm/sec but raise the temp to 240C. Or pick some other speed/temp position on that graph and cut the speed in half.

 

The important line on the graph is the dark blue line and note that it is for .2mm layers only. For .1mm layers you can print twice as fast:

http://umforum.ultimaker.com/index.php?/topic/4127-um2-extrusion-rates-revisited/

 

[carlose_martin 0]

Thanks for the graph, gr5, I've bookmarked it to keep in handy for future references :cool:

It's indeed good advice, I'm currently printing the replacement, it'll finish in 2 hours.

I'm currently using 0.1mm layer height for most projects. I have a batch of minis waiting to be printed, which I plan to print at 0.05 for high quality and see how it works out.