3D printer head for CNC 3020
Having got my CNC router working decently, an obvious next step was to add a 3D printer head to it. As it already has all the mechanics needed for the 3-axis movement, I only needed to add an extruder and hotend to make it print.
At first I thought the speed might be an issue, as the leadscrew-driven machine needs many more steps per mm than a typical belt-driven 3d printer. However, I can get 40 mm/s travel and 300 mm/s2 acceleration, which is a quite typical speed for a printer. Perimeter and infill print speeds I have currently limited to around 20-30 mm/s due to quality and adhesion issues.
The most limiting factor is the 50 mm Z travel, which limits the height of largest printable objects. By remounting the hotend in the spindle holder in the middle of a print, I could theoretically print up to 7 cm high, but above that the moving carriage comes in the way.
I decided to go with 1.75 mm filament with a Bowden cable extruder. This allows placing the extruder together with the filament spool, and only the hotend needs to move around. To make thing simple, I integrated the extruder motor with the spool holder, producing a neat little stand that is easy to put away in a closet when I'm using the CNC for milling.
The CNC3020 original spindle has a diameter of 52 mm and mounts into a screw-tighened bracket. To be able to easily replace it with the 3d printer hotend, I made an adapter out of steel pipe of the same diameter.