All-metal hot end clogs, need help

Hi everyone

I followed the design here: [forums.reprap.org] to make my own all metal hot end.

1.95mm hypodermic tubes and heat sink: [www.box.com]
Assembled hot end with nozzle off: [www.box.com]
Nozzle assembled: [www.box.com]

I'm trying to extrude PLA at 200*C and it has this problem: after I simulate the back and froth movement of the fillament, the filament would build up in the tube near the transition section between the hot and cold area of the tube. Once it build up, the filament becomes the size of the tube and it's not possible to extrude any more. If I pull the filament out then cut the budge part away and put it in, I can extrude again until I do the back and forth movement. All these tests are done by hand with the nozzle removed.

The cold section of the tube is really cold if I have a small fan blowing at it. If I don't use the fan, the whole PLA filament becomes soft and it's not possible to extrude either.

The inside of the stainless steel tube is looking pretty smooth, but I don't know if it is really smooth enough or not. The ID of the tube is about 1.95mm.

Anyone has any solution/ / suggestion for me?


Thank you,

-Thanh

Edited 2 time(s). Last edit at 06/05/2013 05:33AM by ThanhTran.

What's the thinking behind having such a large gap between the hot and cold blocks? I would wager that you'd get a shorter and sharper transition zone by having the cold block right next to but not touching the hot block.

Hi Billy,

Thanks very much for the response. I was trying to reduce the lost of heat which results in inefficiency in power usage.

My heat sink can slide up and down and thus I can adjust the gap. I was testing it with 4.22mm last night. Didn't work well. Just now I reduce the gap to 3mm, and it makes quite a difference. I can now actually make some small back & forth movement and can still push a long string of filament out without it getting stuck. Will try printing something next This is my first time ever using PLA (I've been using ABS for several weeks with PTFE tube and liner)

Thanks again
-Thanh

What is the length of gap that people are using in their all-metal hot ends?

Thanks

My new hit end seems working fine with PLA so far. Thanks for the helps I've gotten. But my PLA prints keepchanging colors. The filament is ppurple, but it looks like the attached photo. Does that look like I have too much water in the filament? Do I need to cook my PLA filament to dry it?

Thanks