Installation of MK8 Extruder
1) The extruder comes with a Nema 17 bracket providing various mounting options. For example, it can be mounted on a typical i3 printer Y carriage as shown at right. Install the bracket first with two screws holding it in place. It is also possible to drill additional holes on the X carriage, though two screws should be sufficient.
2) Next, unscrew the two M3x45mm screws on the MK8 extruder and reassemble it with the bracket. The bracket will be in between the heat sink and hot end.
Firmware setup
The perimeter of the center gear is about 33.5 mm. Thus, by rotating the stepper shaft one revolution, there will be 33.5 mm of filament extruded. Without microstepping, it’s 200 steps per revolution. As a result, steps per unit setting for extruder is 6 (no microstepping), 12 (1/2 microstepping), and 96 (1/16 microstepping).
The corresponding code in the firmware can be found by searching #define DEFAULT_AXIS_STEPS_PER_UNIT #define DEFAULT_AXIS_STEPS_PER_UNIT {x,y,z,96} //x,y,z are the steps per unit depending on the printer you have The number (96) may need to be calibrated to get better results
A simple calibration can be done by following these steps:
- Open Printrun (or other control software.) Set nozzle temperature to 190°C and extrusion length to 100 mm.
- Or run command M302 S0 to allow extrusion at any temperature.
- Cut a section of filament ( about 250-300 mm) and feed it into the extruder.
- Click extrude once. When it’s finished, measure the remaining length from entrance of extruder. For this example, we'll assume the result is 175mm.
- Click extrude one more time. When it’s finished, measure the remaining length again. Continuing our example, assume this result is 85.
- The length of the extruded filament should be 100mm but the actual measurement is 175-85=90mm. Thus the calibrated steps per unit should be 96*(100/90)=106.7
Further calibration and fine tuning could be done by a test print. In most of the cases, this calibration is sufficient.