Adam Kemp made this low cost extruder project from scratch made from aluminum and automotive glow spark as heat source. You will need to cut some aluminum parts, but the design looks solid.
From project description:
Thingiverse page:
http://www.thingiverse.com/thing:153464
Detailed making instructions are at:
http://makezine.com/projects/guide-to-3d-printing-2014/glow-plug-3d-printer-extruder/
From project description:
I love 3D printing, so I decided to build my own printer. After playing around with commercial machines like MakerBot’s Cupcake and Thing-O-Matic, it hit me that I could make my own for free, or very near it.
So, off I headed down the long and winding road to design and build a small 3D printer (or as my son likes to call it, the Toy Machine). After a great deal of dumpster diving, I scavenged enough stepper motors, linear rails, and drive belts for the mechanical parts, but I was stumped when it came to the heart of the printer: the extruder. The internet turned up a slew of fancy designs, but all possessed one design flaw: they required 3D printed parts, so you’d need to have a 3D printer to make a 3D printer!
My solution was to build this robust extruder using a handful of tools, one online parts order, and a trip to the auto-parts store. For a heater, it uses a $10 glow plug from a diesel engine, and it performs as well as commercially available extruders.
Thingiverse page:
http://www.thingiverse.com/thing:153464
Detailed making instructions are at:
http://makezine.com/projects/guide-to-3d-printing-2014/glow-plug-3d-printer-extruder/
