The third axis of my DIY plotter is the one that moves the pen up and down while the other two axes move the pen around.
While playing Lego with my daughters I tried to figure out a possible solution based on Lego, and I quickly came out with this design:
It uses a large rubber wheel to transfer the rotation (demultiplying it) to a steering component that converts rotation into the up/down movement. The movement is not perfectly linear, but the approximation is fully acceptable, since the pen needs just a millimeter of vertical motion to detach itself from the paper.
The stepper is firmly held in position just by bricks.
The pen holder is made of the plastic part of two wheels and a rubber band. It is pretty solid and the rubber band helps to keep some pressure between the pen and the paper, when the pen is down.
While it is perfectly working I’m not going to use it in the plotter, because (i) it is not compact, (ii) it does not blend with the rest of the plotter (it is better fit for a completely Lego-based project), and (iii) I don’t want to steal “forever” these bricks from my daughters’ constructions.
I’m working on a solution based on a floppy disk drive that seems promising.



Il Malvaldi (Marco) io non lo conosco, lo conosce il