Glow Plug 3D Printer Extruder

Make an extruder by hand using only a few tools and a diesel glow plug from the auto parts store.

Written and photographed by Adam Kemp

Visit makershed.com to check out Adam's book The Makerspace Workbench

Time Required: A Weekend Cost: $40–$60

ADAM KEMP
directs the Energy Systems Research Laboratory at Thomas Jefferson High School for Science and Technology in Alexandria, Va.

I LOVE 3D PRINTING, SO I DECIDED TO BUILD MY OWN PRINTER. I scavenged the stepper motors, linear rails, and drive belts, but I was stumped when it came to the extruder. The extruder designs I found online all had one flaw: They required 3D-printed parts. So you’d need 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. It uses a $10 glow plug from a diesel engine for a nozzle heater, and it performs very well.

Hobbing a Bolt with a Drill Press

You'll need basic machining skills and tools to cut, drill, and tap aluminum bar stock and steel bolts, thread a steel rod, and bend a little sheet metal before you bolt it all together.

Typically an extruder’s feed wheel is a hobbed bolt (i.e. a bolt with gear teeth cut into it) that’s made using a lathe and a specialty jig. But if you don't have access to a lathe, there's a clever trick for hobbing a bolt with a drill press, a tap, and a couple of 608 skateboard bearings.

Using a DIY Extruder

If you're swapping this into an existing printer, consider using the printer's thermocouple and stepper controller electronics. If you're building a new machine, connect the motor, stepper, and temperature sensor to the controller, and hook the glow plug to the heater circuit.

This extruder has a 0.3mm layer height, 1.75mm filament diameter, and 0.39mm nozzle diameter. To configure your software to use the new extruder, you’ll need to calculate the rate at which plastic exits the nozzle (based on the feed wheel diameter, stepper resolution, and gear ratio). Plug this data into the Profile Maker over at MakerBlock.com to automatically generate Skeinforge settings before you start printing.

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