You did it! Wasn’t that easy? You now have a super-robust homemade extruder ready to start pumping out plastic for your next project.
But wait! Don’t get ahead of yourself. Rather than throw the extruder straight into your printer, hook it up to a bench power supply and a stand-alone temperature controller and see how it works. I like to play around with scrap filament and use a manually fed stepper controller to test my feed rates and flow rates. This will allow you to tweak alignments, adjust the tensioner, and make sure everything runs smoothly.
The first step to configuring your extruder is to locate the type of control electronics you’ll be using (RAMPS, GRBL Shield, or what have you). If you’re swapping an old extruder out of an existing printer, you might want to consider using that printer’s thermocouple and stepper controller. This will save a lot of the headache of reconfiguring the machine.
If you’re building your own machine, the connections are simple. Connect the temperature sensor, stepper, and motor to your controller and hook the glow plug up to the heater circuit.
CAUTION: You’re using an automotive glow plug that can reach dangerously high temperatures. Make sure you have implemented some order of thermal/circuit protection in order to prevent unintended fire or harm!
Now, for configuring your software. Determining the exact steps/mm at which plastic exits the nozzle requires some pretty heavy math and analysis. Rather than diving too heavy into the books, you can use the following calculation to get you into the ballpark and tweak the numbers as you print test pieces:
steps/mm = R * r / (𝜋 * D)
R = number of steps per revolution of the motor
r = gear ratio (in this case, 24:52 or 2.167)
D = feed wheel diameter (in my build, 6.82mm)
So, when I start configuring my control software (i.e. Teacup, Marlin, etc.) I would start with a steps/mm value of:
(3,200 steps/rev * 2.167) / (3.14 * 6.82mm)
= 323.81 steps/mm
The next bit of information you need pertains to the filament and nozzle part of the extruder. This information is required by ReplicatorG and others for determining proper flow rate and feed rate while printing. This extruder in its stock configuration has the following specifications:
Layer height = 0.3mm (I use this as a general purpose layer height)
Filament diameter = 1.75mm (measure for accuracy)
Nozzle diameter = 0.39mm (measure for accuracy)
You can now plug these metrics into the handy ProfileMaker over at MakerBlock.com and get started printing!