Wednesday, February 29, 2012

Tom's one piece nozzle

Over the last few months, I've been having a look into the various hot ends in the 3D printer community and the availability to those of us in Australia. They all seemed reasonably expensive at nearly $100 inc delivery (wont mention any in particular), and being a stingy uni student, it wasn't something I could justify for what was a few dollars in material.

Thereafter, I began prototyping a few designs and ideas I had with the intent of doing small production runs to reduce the cost. I particularly like the elegance of the J-head nozzle - a one piece design - and designed a derivative from this. Credit goes to Reifsnyderb and the excellent information on the reprap wiki (link). Many of the fundamental features were kept including Teflon sleeve, Peek insulator.

Changes I made to the J-head design were;
  • Dimensions in metric.
  • Through hole thermistor
  • Enlarged insulator hole (loose fit) to accommodate expansion of filament to prevent jamming.
  • Long thread for greater seal with insulator and to allow adjustable total length on nozzle. (incase you run to this problem (link)
  • Trapped PTFE tube in the insulator to prevent tube from reversing out of the hot-end.

Excuse the poor design work. Funnily enough, metric brass bar is not all that common here in Australia so I proceeded with the initial sizing of 5/8"x3/8" brass bar. Tolerance is to DIN ISO 2768 (fine). So an order was placed at a CNC manufacturer for a small run of these.

It was like xmas when these arrived and I quickly gave the finishing touches on my lathe to test them out. Machining the nozzle tip to 0.5mm and also the Peek insulator.

The PTFE sleeve/tube is standard 4mmOD/3mmID. The loose fit of this tube allows for expansion of both the filament and the tube. I see the direction most people have gone is to cool their insulator to prevent jamming. My personal experience with the loose fit tube has thus far, never produced the jamming effect of the filament. I'm probably one of the lucky ones that have never experienced it. **touch wood


I then increased the shoulder on the Peek insulator to reduce the heat being transferred to the mount. These fender washer can accommodate the 30mm spacing mount. Overall length of the nozzle is 54.5mm with a 40mm insulator.
Here it is mounted to my Prusa...

Initial impressions on the characteristics of the hot end are the heat ramp times are very short compared to my old V2 nozzle. It was able to reach stabilised printing temperature for PLA in  1min30. Extrusion speeds have also increase from before.

Also with the small diameter flat at the end of the nozzle, it'll require some tweaking for the w/t ratio as I found out from the 50% Yoda print.
I was quite pleased with it being the first print from the nozzle. As you probably can tell, the photos are straight from the printer. I will test with smaller diameter nozzles once settings for the 0.5mm nozzle is perfected.

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