Micro Mini CNC Plotter - Part 2 - Testing Hardware and Software

A micro-mini CNC plotter built from 2 DVD drive stepper motors and one camera stepper motor. It has a 36mm by 36mm drawing area (that's the size of the big square you see being drawn).

It uses a cartridge from a ball-point pen to draw. Not the best for plotting, but small enough to fit in the print head. I'm looking for a felt-tip pen cartridge to replace it, but haven't found one small enough.

In terms of hardware, I made it from parts I had sitting around. As you can see, there are a lot of salvage parts as well as some fabricated parts. Most of the small metal parts you see were made (bent up) from pieces of a floppy drive case and some hold downs from inside DVD drives. All the screws came from DVD drives. All the rods came from DVD drives. The wire is from USB mouse cords. The spring is from a DVD door flap.

As for electronics, I'm using a generic USB serial adapter to talk to three pic12f675 micros from a Linux desktop. The PICs each control an SN754410 quad half bridge to run the X, Y, and Z axes (motors). Basically I'm sending the pin-out serially to each motor on a master-slave network. Not much else going on.

The software is is a series of stacked Python 3 classes. The lowest level class handles talking to the microcontrollers. On top of that is a stepper class that tracks the motor locations and does the math necessary to make the movements efficient. On top of that is a g-code interpreter, and at the very top is a class specific to this mini-plotter that handles zeroing and the up-down of the pen. The top class also includes the single font definition and the functions that scale and center. I like how the software is stacking up (pun intended), but it needs a lot of refinement still.

This has been a good way to learn the fundamentals of NC and g-code. I think I'm going to make a PCB milling/drilling machine next. Maybe.

Code:
http://claytondarwin.com/cgi-bin/down...