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I had a friend help me out with a design I wanted to try. I kept having problems with the filament getting too hot and not feeding. So we are trying something just a bit different. I still need a new nozzle but I hope this makes it easier to keep it cool.

I saw on another forum that they are using brass tip with a small melt zone and stainless steel tube. no peek at all. Surprisingly its stays cool to the touch without a fan must have something to do with dissimilar metals; I don't know, but it seems to work. jgr hotend made in austraila. trinity labs testing one in the video. Supposed to be able to print with most filament without problem. Model for the delta (rostock) styles printers coming soon.

http://www.youtube.com/watch?v=hxsQ0dmW2N0 google groups discussion https://groups.google.com/forum/?fromgr ... Bt6T0TYRCY

heres a picture of him holding one in his hand at 562 degrees celcuis https://www.dropbox.com/s/wfwnef1vlt2iz ... 8569.JPG?m

Just thought I'd throw that out there to give you some ideas

cambo3d wrote:I saw on another forum that they are using brass tip with a small melt zone and stainless steel tube. no peek at all. Surprisingly its stays cool to the touch without a fan must have something to do with dissimilar metals; I don't know, but it seems to work. jgr hotend made in austraila. trinity labs testing one in the video. Supposed to be able to print with most filament without problem. Model for the delta (rostock) styles printers coming soon.

http://www.youtube.com/watch?v=hxsQ0dmW2N0 google groups discussion https://groups.google.com/forum/?fromgr ... Bt6T0TYRCY

heres a picture of him holding one in his hand at 562 degrees celcuis https://www.dropbox.com/s/wfwnef1vlt2iz ... 8569.JPG?m

Just thought I'd throw that out there to give you some ideas

No Stainless is an excellent insulator if you make the wall thin enough, apparently the magic number is ~0.5mm
It's interesting only because Nophead tried a stainless extruder over 3 years ago and couldn't get it to work reliably without using a tapered bore, but there are now a few all stainless hot ends with bo peek or PTFE.
Jolly Grim Reaper is selling one, Joseph Prusa has one.

Yeah, but prusa's are unobtanium Hopefully, when I pick him up next Wed. for MRRF, he'll have some hiding in his bag!

johnoly99 wrote:Yeah, but prusa's are unobtanium Hopefully, when I pick him up next Wed. for MRRF, he'll have some hiding in his bag!

Yeah they are both pretty much unobtanium at this point, I was tempted to try machining one, but I hate machining stainless.
If they work as well as their creators claim, we'll see plenty of copies, not only can they print hotter without issues but they have less parts and are probably cheaper to make.

maybe seemecnc will make there own version too. Id buy one.

Those are pretty neat. I may see if I can find some stainless tube to try out. I found some smaller fans as well so maybe one front and one back?

Just a teaser - I've been working on an all stainless hotend myself for a few months off and on. I started with the original patents and some of the even earlier patent literature. I used to do research in the area of ceramic composites and we used injection molding technology to inject a moldable ceramic polymer precursor (that was my work) into a mold. We had a very early 3D printer to prototype the complex airfoils like in this photo. Who would have thought I'd build my own 3D printers someday!
I spent a lot of time with extruders and managing heat since my polymers would thermally decompose. Stainless injection nozzles are surprisingly low heat conductivity - especially when compared to the thermal conductivity of aluminum and brass. Most (all?) stainless alloys have fairly low thermal conductivities. Adding mechanical cooling features like vents and fins allowed us to heat and cool the injector nozzles very quickly yet the stainless steel has enough mass to maintain an constant temperature once reached. Pretty cool stuff actually!

Cheers,
Michael

Dang, That sounds like it was fun. Spring Break is next week so I am going to be trying again. Ellen, my wife is really excited about having the printer working correctly so she can design shoe lasts, and I just love to play. When you get a sdesign ready please let us know!