I constructed this gantry router mill from 80/20 aluminum extrusion. My design intentions here were to keep things as simple as possible. I wanted a machine that I could simply bolt together and expand as needed.

The entire machine has a footprint of 4' x 4'. The cutting area is a little over 30" x 30". The mill was designed to use standard 4' lengths of 3" 15 series extrusion. I kept the entire structure of the machine purely 80/20 parts, except for the 1/2"-10 lead screws and the Z-axis. There are only 4 different types of 80/20 parts on this machine, the 3" extrusions, the "L" brackets, the custom stepper mounts, and the 80/20 linear slides.

I run this mill with a jog speed of 300 inches per minute. I run a cutting feed rate of around 50-60 inches per minute depending on the material and bit. I primarily use this machine to mill hard woods and MDF, as well as some nylon, polycarbonate, and acrylic plastics.

I kept the cutting bed as struts to allow for a variety of clamping setups. It is very simple to add a fence to this setup as well.

The router's power is controlled by an large external kickbox switch for safety and ease of use.

I installed the joystick package as well as QJoyPad on the Ubuntu control box so I could use the wireless USB Xbox360 controller to move the machine. QJoyPad is used to map the buttons on the controller to keys on the keyboard.

X and Z axis

The the Z-axis and spindle mount for the router was purchased from K2CNC.

dual drive Y-axis

For the Y-axis I ran two lead screws with two stepper motors wired in parallel. This is a solid setup. I had previously run a center fed lead screw with a single stepper and it was racking (twisting at the center) too much. The design of this machine proved versatile enough to try both setups.

linear bearings (slides)

I decided to go ahead and experiment using the double flange linear bearings that 80/20 offers. These have proven to be a nice cost effective solution to other linear bearings and linear support shafts, and also reduces the number of parts and complexity. These linear slides are somewhat fickle to setup, but once the slide inserts are appropriately shimmed on the inside, the machine is very smooth.

These slides are not designed to be side loaded the way I have them set up, but it works for me and has proven sufficient. You must be patient with these linear slides, I had to assemble and disassemble them multiple times until the shimming was just right. Warning: You will get annoyed with these.

A piece of red 1/4" thick fiberglass was used to bump out the linear slides so everything would line up on center. A 7/8" bore was drilled and tapped to fit the plastic lead nut.

For the lead screw ends, I push fit a flanged ball bearing into the mount. I used a clamping shaft collar for the thrust action of the lead screw.

stepper motors

For the stepper motor mounts I had 80/20inc machine a NEMA 23 bolt hole pattern and 3" extrusion bolt hole pattern into a blank extrusion they sell.

I used four wire DIN connectors on the steppers and created some male / female cable assemblies

frame:	Nema 23
wiring:	4 wire bipolar
step angle:	1.8 degrees
rated current:	3 Amps
rated voltage:	12-48 Volts
phase resistance:	1 ohm
phase inductance:	3.5 mH
holding torque:	254.88 oz/in
detent torque:	8.5 oz/in
rotor inertia:	2.411 oz/in2
motor weight:	2.31 lbs.

light

I hot glued a circular LED array to the bottom of the router so I could see the cutter better. Time will tell how long it will stay attached after the constant banging of a wrench to change the bit. I wired it directly to the power supply in my control box, so that when I boot the control box the light turns on.

The 80/20 allows for a variety of configurations, is easy to adjust, and is vastly expandable.

Fine adjustment is the key in a machine of this nature. A 1/32" of slop, a couple of degrees out of square, or over tightening in one place may cause unexpected consequences somewhere else in the machine.

I have found this to be very solid, stiff, and precise for a DIY machine, although working out the quirks took a while.

If you are thinking of building a gantry type mill, I highly recommend modelling it in a computer first. 80/20 part models and many other parts can be downloaded from 3dContentCentral.com. If this is your first build, I would also recommend starting small and experimenting with the mechanics first to get a feel for things, especially the torsional forces involved in such a machine. Another great resource to get your CNC blood pumping is CNCZone.