Extruders Galore

For DIY 3D printing, there seems to be no shortage of extruder designs on the web. In terms of reliability and print quality, these designs seem to be all over the map with no clear indication of which one actually works best. Looking over some of the more popular designs, I've been able to find components of each that I would like to have in my 'ideal' design.

MakerBot Industries is now producing it's 5th generation of thermoplastic extruders so its seemed appropriate to identify the strongest, and weakest attributes of their design. Early thermoplast extruders used Nichrome wire wrapped around hollow all-thread. These designs were clumsy and prone to shorts and uneven heating. MakerBot instead uses surface mount power resisters instead, and a stainless steel thermal block to distribute the heat evenly.

Weaknesses include the dc gear motor, and the tension screw that keeps the filament in contact with drive pulley.

Another site, MakerGear, produces extruders that use a stepper motor to more precisely control the filament feed. The motor is also used in conjunction with a 13:1 gear reduction, resulting in an extremely powerful feed mechanism.

The Brutstruder is another opensource option available on thingiverse.com. This design's most powerful advantage are the spring's it utilizes to keep the filament constantly pressed against the drive pulley. According to its author, the Brutstruder is capable of lifting 27 lbs-

The ideal extruder for my printer will combine all of these elements: geared stepper motor, surface mount power resistors, and spring tensioning.