Building a CNC machine

The final machine is supposed to look something like this:

Click here for plans in PDF format.

Current progress

Linear guides, ball screws, ball nuts and bearings; all brand new. I like to use socket screws because they look good and you can tighten them easily.	(big)	(big)
Most of the aluminium was cut by the supplier. The main frame has been drilled and tapped and bolted together. The Y base rail and X cross rail are in place and seem to be solid and perpendicular enough.	(big)	(big)
The motors and ball screws need to be mounted next. (Dated 27/2/2007)	(big)

The electronics are the next thing on the list. I make circuit boards from scratch using the laser printer toner transfer method. I find this method works very well and is relatively easy.

Stepper motor controller, based on the A3977 chip. Design printed on glossy photo paper, ready to transfer with a hot iron.	(big)
Iron on the design, then etch! The small tracks are 0.4 mm thick. The large ones around the edge are 2 mm thick.	(big)	(big)
The main micro-controller board, based on an Atmel mega-324p.	(big)	(big)
The USB interface, based on a CP2102. I couldn't solder the CP2102 it its proper place (it is 5 mm square!) so wires had to be used. It still works fine.	(big)	(big)
Completed electronics box. Red switch is kill switch for the stepper motors. LED is power indicator. LCD is for general information, and feedback when you control the machine with the joystick.	(big)
Inside are three motor controllers, Atmel controller, power distribution, USB interface, 60W switch mode power supply. Lots of cables.	(big)
Connectors are (left to right): stepper motors out, joystick in, power in (240v AC), USB.	(big)

The machine with motors and ball screws mounted, and the control box. (Dated 17/1/2008)	(big)	(big)
The machine with drill mounted. And first tests drilling a grid of holes in some wood. Holes have 2mm spacing. (Dated 7/9/2008)	(big)	(big) (movie 3MB)
The drill is now wired to a solid state relay that is used to turn the drill on and off in software. There is also a red emergency stop button (which turns the drill off, holds the x- and y-axis at their current position, and pulls the z-axis up about 0.25mm) and an extra mechanical safety switch for the drill.	(big)

In its current state, the machine can only barely mill aluminium. The movie shows a very slow and shallow pass cutting out a shape. Pass depth: 0.1mm, milling speed: 2mm/s, mill bit diameter: 1.6mm, drill speed: about 12000 RPM. Basically the machine is not rigid enough to mill even soft metal. There is too much play in the stepper motor to ball screw couplings, in the backlash of the ball nuts, and in the thin aluminium mounts used for the y- and z-axis. (Dated 3/11/2008)

(movie 3.5MB)

Mechanically etching a printed circuit board. Parameters: depth: 0.18mm, feed speed: 8mm/s, isolation width: about 0.4mm, drill speed: about 30000 RPM.	(big)	(big)	(movie 4MB)
Improved aluminium milling. Parameters: pass depth: 0.1mm, milling speed: 4mm/s, mill bit diameter: 1.6mm, drill speed: about 10000 RPM. (Dated 6/11/2008)	(big)	(big)	(movie 5.5MB)

Milling slots and holes for a table clamp. It is easier to make large cuts with a hacksaw than use the machine, so I milled shallow guide lines for the saw.	(big)	(big)
Milling the edges of the four clamps flat. The drill is not perfectly perpendicular to the table, so the finish leaves tiny ribs on the surface. The finished clamp is shown on the right. The dimensions of the support grooves are 3mm wide by 1mm deep and are able to clamp wood, PCB and aluminium. (Dated 16/11/2008)	(big)	(big)