Thursday, April 19, 2012
Here is Myles's latest mixer extruder. On top is a 12V geared-down DC motor turning a vertical PEEK drive shaft. The brass hot end is shrouded in insulating glassfibre. Inside it is a cylindrical cavity with a length of brass hex rod that is turned by the motor. This is the stirrer. It is sealed by a silicone O ring. Bowden feeds are routed in at the sides near the top of the hex rod.
The hex rod is about 0.2mm less across the corners than the diameter of the cylinder in which it turns.
And here is a much clearer picture of the results with the input colours either side:
This is with no stirrer control - it is simply on all the time the end is hot. We think we will get less dribble if we turn it off when no extrusion is required.
The obvious way to use the device will be to have a purge bucket (maybe with a nozzle wiper) and to set a new colour then run the device over that till the colour runs true. Slightly wasteful, but the purge volume shouldn't be more than the volume of the void in the device, which is not great.