Thursday, July 31, 2008


An affordable alternative to JB-Weld and BBQ paint?

Cheaper alternatives to Cerastil for securing nichrome heater wire to extruder barrels may be in the offing... read more

Hi, Forest:

Kudos to you for all your work. I was looking for an alternative for a while, and found something that also might work. I have a different extruder design that uses a catridge heater now, but I almost bought this stuff :*ITPD&PMITEM=00322834&PMCTLG=00

(bottom right of page)-- there are two choices. Intrestingly there are two versions-- both are electric insulators, but one is designed for low heat conduction and one is designed for high heat conduction.

MSCDirect is one of my "default" sources for "hobby" supplies :)
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I used a cartridge heater for a powder filament extruder that built over a year ago. Darned thing looked like a blasting cap. It worked like a champ, though.

Maybe you'd better post your resistor cement find on the forums and somebody can try it out. I'm stocked for the next couple of years unless this stuff fails.

Tell me, though. My cartridge heater came in a pretty high thermal rating and used 110 v AC. Can you blog some more about your design? Sounds really interesting. :-D
While at my local NAPA Auto Parts, I noticed a substance by the name of "Heatweld". It said it gained heat with strength and withstands up to 2,400F. It was $6 for enough to cover several barrels. Might be worth a look.
Hi, Forrest:

thanks for asking :)

first, pictures:

I've not posted the design anywhere because i've noticed most reprappers dont want to use line current because it limits portability.

the cartridge heater is 1/4" diameter and 2" long, and uses 110V power.

Anyway, I use a K-type tcouple, 110V cartridge heater, and a PIC 18F4331 to do PID control for the temperature. and the extruder drive. The heater is controlled via a triac and MOC3031 triac driver.

The motor uses an AS3040 magnetic encoder for position feedback. A PID look provides closed loop control

The barrel what's was most difficult. I use a two-part barrel-- the extruder end is brass, but then i have a stainless steel entry tube to keep the material from melting on entry. They are both threaded, with an aluminum heat sink that helps cooling

The filament is fed using two roller skate bearings with custom-made v-groove rings affixed. This dramatically lowers friction.

I use the standard acorn-nut nozzle arrangement, taht works ok so far.
Wow! Cool!

About the only potential problem that I can see in the design is the distance from that roller bearing nearest the extruder barrel to the barrel itself. Don't you think that the filament might want to bend rather than transfer all that force straight into the barrel?
Dave! Why the hell aren't you blogging this in the builders blog? Ask Adrian for permission to blog if you haven't already. :-)
Seems to work ok, but this is kind of a lashup, and I think you are right that a shorter distance would be ideal.

For a while there was a longer distance, and the filament was buckling then.

Once i get the design finalized, ( which probably wont happen till later on since this actually extrudes ) i'll adjust to make it as compact as possible.

I'll ask Adrian for permission to write to builder's blog. I hadnt dont that in the past because i'm not really trying to build a reprap, just an extruder to add to my 3-axis mill. But, I'll see what he thinks.
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