I am a PCB designer by trade with 3D modelling experience in design of small enclosures. Creating physical 3D models on the cheap is something that I've been interested in for a while. Building a scaled down CNC machine to learn how stepper motors, 3D axis controllers and CNC software works at a minimal cost was my goal. I've managed to do this for only $45 and a few evenings.
Things you will need:
A electronics recycle depot. After a few trips to the location near my place I found a pc with two dvd burners a floppy drive that looked undamaged. These parts with give you your X, Y and Z axis.
It may take a few trips to the recycle depot but get as many DVD or CD Roms as you can. You will need to find ones that use 4 wire stepper motors to move the laser head, not the two wire DC motor type.
Plastic pieces needed to make the base. BusyBee tools sells assorted pieces for $10. The package I grabbed had a few black sheets of 1/4" plastic.
A three axis controller. A quick search on Ebay will turn up this type for $35 or so. Just do a search for 3 axis stepper motor controller and look for one of these.
A desktop pc running Windows XP with a parallel port. I hear laptops and USB to parallel ports adapters can be trouble.
Mach3 software that is free of charge.
Ace DXF to CNC converter that is free of charge. Lazycam beta that comes with Mach3 is also free but I have not tried this yet.
Solidworks is what I use drawing the DXF designs. They were offering free eval copies a while ago. A demo version may also be possible. Solidworks just released Draftsight for free as well that creates 2D drawings.
A 12 volt power supply. The bipolar stepper motors in the cd or dvd roms are designed to run at 5 volts. I've set the dip switches on the controller to the lowest current output and set the power supply to 10 volts. The motors do get very warm when run for a few minutes but are still working fine.
-you need an X and a Y axis so remove and open the dvd or cdrom to identify if a two wire dc or four wire stepper motor moves the laser head. The four wire stepper is what you want. Measure with and ohm meter the four motor pins two at a time. You need to find each of the two coils that measure only a few ohms and solder two feet of wire onto each coil.
-strip off all parts except for the slider. You have to machine off the high bits to have the standoffs sit flush.
-remove the floppy drive and with a dremel tool cut away most of the frame. I machined a round plastic tube so it would sit on the floppy drive head with a hole in the middle to hold a pen.
-cut the plastic pieces to make the base large enough to hold the X and Y axis. Send me a message if you want my base dimensions in .dxf format.
-mount the lower Y axis table with standoffs and attach small square table surface.
-mount floppy Z axis to the upper X axis.
-data sheet for the driver: https://docs.google.com/viewer?a=v&pid=explorer&chrome=true&srcid=0B8fmR4_OV084MDNiYjNjYjktOTRkMC00ZjNkLTg1ZTMtYmU3YjQwZWE5MDNm&hl=en&authkey=CM2715MI
-Solidworks files: https://docs.google.com/leaf?id=0B8fmR4_OV084NDgxYmVkYjgtNGUyZS00NzIyLTk5YzAtMzU4ZGEzZTM2YjZm&hl=en&authkey=CLGFhdgF