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Fix your extruder jams - step by step now on the wiki

Posted by jeffpark_ 
Fix your extruder jams - step by step now on the wiki
March 29, 2010 10:14AM
Mendel_User_Manual:_Extruder

Copy/pasted from my blog.

edit:
fixed wiki link
edit 2:
really fixed wiki link

Edited 2 time(s). Last edit at 03/29/2010 10:15AM by jeffpark_.

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Re: Fix your extruder jams - step by step now on the wiki
March 29, 2010 03:20PM
Thanks ;-)


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Jeff -

I made a set of photos of the ABS and PLA melt process (using a glass extruder) - here are links to the photo sets:

ABS Melt Process
PLA Melt Process

Is it possible that some of the backflow you encountered was the result of uneven heating from the torch?

Before trying to alter the melting zone, a simpler approach is to measure the temp at the top of the heater barrel. In scenarios where a large washer is used to hold the hot end in place, it is common for the top of the barrel to have a considerably lower temp than the heater/nozzle area. On a 50mm heater barrel, for example, the temp at the top of the barrel needs to be at least 150C for PLA 4042D not to jam...

Also, when making nozzles I use a 5mm bit and then tap M6. If you drill it out with a 6mm bit, it seems like the nozzle would be ruined. Though I use a torch to loosen/clean nozzles and barrels, I've never had to drill one out.

When someone tells me they have to print ABS at 240C it is usually the result of a thermistor/thermistor table mismatch (at least in regards to mBots).

Rick
Re: Fix your extruder jams - step by step now on the wiki
March 30, 2010 11:02AM
You are correct about the drill size, typo in my haste to get it posted. I fixed it on the wiki. I agree with you on the torch, it helps quite a bit, you should write that up. The main reason I drilled out my nozzle was I ripped a barrel in half and the only way to remove it was to drill out the nozzle. It doesn't take much torque to destroy a 6mm hollow brass rod!

Using an external thermometer the nozzle temp was usually withing 5 degrees C so I never did a recalibration though I probably should. The process of trial/error temp adjustment should still be the same though, exact temp values may not.

The backflow I noticed with the torch was just a quick test to see if I could recreate what was happening with the extruder heated by nichrome, and it did. Since I have a McWire I have to set the filament feed rate very slow, which causes it to melt farther up the barrel than it would in normal operation conditions (Mendel/MakerBot are usually 30mm/s or more X-Y feed rate, McWire maxes out at 5.8mm/s). Using the barrel with the turned zone was the only way I could even get it to print for more that 10 minutes. Yesterday I finished the last part I needed for my Mendel, and it had been printing for nearly 30 hours continuously before that (except when I slept through my alarm a couple times). The thin-section barrel is also the last on my list of things to try as one of the others will probably fix most peoples problems. If not, might as well have that to try too.

Those photos are interesting. What is the ID of the glass? It looks a little larger than the filament. Interesting stuff.

edit..forgot to mention stuff

Edited 1 time(s). Last edit at 03/30/2010 11:10AM by jeffpark_.

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