Tuesday, November 8, 2011

J-Head Nozzle Feedback

I received an e-mail, from "Dazed" this evening, providing feedback on his experience with the J-Head hot-end.  I appreciate any feedback anybody would like to supply as it really helps me to make improvements to the hot-end. 

After receiving permission to post his e-mail, here it is:

I've been using your J-head hot end for a few days now. For what its worth, here
is my input:
Huge kudos for having it pre-assembled. Probably the only issue I had with hybrid
insulators is getting the PTFE to brass junction tight but not too tight. It
either allowed a plug to form or I was clamping down on the filament via
over-compressed PTFE. All I had to do here was install a resistor and thermistor.
That was pretty cool.
My past experience with resistor based heaters has not been too great. They
always burned out after a couple of weeks. Yours is a bit different from what I
had been using, so maybe it holds up better. It fits much more snugly too, so it
should dissipate the heat better. I'm really interested in seeing what kind of
lifespan it gets. If it only lasts as long as my other resistors, I'll probably
be hunting for a heater cartridge to replace it or at the very least finding a
way to wrap nichrome around the heater block.
The PTFE insert has been a really awesome improvement so far. Again, I'm not sure
what to expect as far as life span but yesterday I wanted to use a new groove
mount holder. Normally I would have had to heat up the filament before it would
back out. Without even really meaning to, the cold plug actually popped out while
I was changing the holder piece. I thought that was a pretty impressive display
of the difference in friction. I'm not sure if the camera really captured it
well, but I thought it was impressive enough that I took a picture of it. I
assume this has to do with the fact that the PTFE feeds further into the hot end
than normal?
The tip on this hot end is much more blunt than what I have seen before. I'm not
sure yet if this is a good or a bad thing. In theory, as the extrusion is pressed
flat, the wider tip would keep it more evenly pressed flat against the previous
layer. This presumably would lead to better layer adhesion. However, I had a lot
of difficulty yesterday printing a 110mm fan cover. There was just a hair too
much plastic being extruded, I think my Z endstop slipped a little and let the
extruder drop lower than normal which caused the extrusion to widen out too much.
After a while, little balls of excess plastic started forming. My other extruder
tip would have plowed right through them no problem, but the wider tip on this
one seemed to snag more and eventually caused skipped steps. Extruder tips with a
sharp cone point seem to handle plowing through excess plastic better which makes
it less difficult to reach "usable" printer settings.

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