Finally got over the flu that I brought back from LinuxConf 2010. Mendelssohn is now printing properly with a stepper-driven extruder and a new heating element/barrel design. This is essentially the old hack using a radio aerial and a heatsink. The M4 nozzle (not shown) fits inside the feed tube, so increased pressure forces the nozzle into a shoulder at the end of the tube. So the more pressure, the better the nozzle seal. The shoulder is created by slowly cutting the tube with a pipe cutter.
I'm dip-coating the 3/16" brass tube in fire cement slurry, drying this, and then wrapping the dry ceramic in Kapton to protect it while I wind on about 6 ohms of nichrome. If the Kapton gets vapourised, the heater element will not then short out on the brass tube. The heatsink traps the extruder as well as cooling the end of it, and also acts as an anchor point for connecting the extruder assembly to the X carriage.
Works so far. No lathe needed, no PTFE, no creep, no leaks.
Vik :v)
Great stuff Vik. How does the nozzle go exactly? Can you put up an extra close-up pic?
ReplyDeleteCould you do the same thing with stainless rather than brass tube and buy yourself another tiny increment of heat shielding?
ReplyDeleteAwesomely simple! Think i'll try putting a stainless one on this:
ReplyDeletehttp://objects.reprap.org/wiki/Development:Geared_Nema17_Extruder
Let us know how fast it extrudes!
Also, what's the ID on your tube?
ReplyDeleteOK, here we go..
ReplyDeleteAdrian, there is a full blog article on the nozzle here http://blog.reprap.org/2009/05/no-lathe-barrel-nozzle.html . I also discovered that you can turn a 0.8mm nozzle into a 0.5mm nozzle by whacking it smartly with a pein hammer! More practically, the "lemon-squeezer" bit on my dremmel does a great job of reaming a parabolic cavity behind the exit hole.
Can't use grub screws - the steel is too hard.
I guess you could use stainless tube. I had brass...
The ID on the tube is pretty much 4mm!
It's K&S Engineering 3/16" Round Brass, stock #1147. Available from most hobby shops.
With a 0.5mm nozzle it can easily do twice what my Ponoko threaded extruder could do. With a 0.8mm nozzle this thing will go like the proverbial clappers. I'm only running the heater at 25% currently because the nozzle I installed doesn't have the ceramic slip on it.
An experiment with a completely slip-coated one would be fun. Trapping the wires inside the ceramic.
Vik :v)
post a video please :) !
ReplyDeleteWade, I'm using it with a NEMA17 already. Hand-cut splines - freehand even!
ReplyDeleteWould do videos but busy redesigning the X motor bracket to a one-piece design that only has 2 belt rollers. Then I'm going to do a new lasercut template for the deposition bed board and breadboard area. I might try doing a side panel in acrylic too, just for kicks & giggles.
Vik :v)
"Adrian, there is a full blog article..."
ReplyDeleteI see that the first comment on that is by one Adrian Bowyer...