Creative Works of Tom McGuire

Easy PC Board Mill

Years ago I posted a design for a desk top CNC milling machine on Instructables.  It was popular and lots of people built variations of it. Since then I’ve always wanted to make a similar design that was specifically made to mill PC boards.  This summer (2012) I had my chance and decided to go for it.

Designed for making PC boards

The main variation from the Instructables design is that the Z axis (up/down motion) is a precision linear ball guide. Unfortunately there is no cheap source for ball guides that I can find. I’ll keep working on an economical solution. Along with the solid vertical frame the guide holds the bit firmly in position as the material moves on the X and Y axis’s. Now we are able to do the tiny stuff. Make circuit boards for surface mount devices like: resistors and capacitors in 1206 and 0803 packages and integrated circuits in SOIC packages.

Here’s an example.

Tiny PCB

And here’s the circuit that it made…

Tiny circuit

 

Ease of use is another big thing. You can adjust the depth of the tool on the fly by twisting the  stop nut on the Z axis lead screw.

Depth Adjust

So all together the proccess of making a PC board is:

1. Layout your board in Eagle Layout Editor or other (preferred design software)

2. Export the top and bottom layers as Gerber 247. Make sure to mirror the bottom layer.

3. Export the drill pattern as Excellon.

4. Then open KCAM to import the files and run them on the machine.

If your doing a double sided board you can run the gerber top side milling, and excellon drilling. Then flip the board and move the tool to the center of a pad and align the material with the corresponding hole(do this for two holes). Then mill the bottom side. KCAM allows you to stop in the middle of a job and make adjustments if you need to without having to restart the project all over again.

Details:

The base of the machine is an old Mac+ external hard drive. It had a switcher power supply and a fan, which I used, and then I just stuck a solderless bread board in there and wired everything to it. I used Pololu stepper driver adapters to interface the PC parallel port to the stepper motors.

Rear View (open)

Here’s a schematic of the circuit on the bread board.

For Eagle Layout Editor (Right click and SaveLink as….) PololuDrive3AxisCNC.sch

Or here’s a generic format  PololuDrive_3AxisCNC.pdf

 

PS:  ask for more details and I’ll add to the page…

2 Comments



2 responses so far ↓

  •   Christian // Jul 22nd 2012 at 9:45 am

    This is awesome. It looks like it does a better job than the Modela. Are you using the same drive circuit that’s in the instructable?

  •   Tom McGuire // Jul 22nd 2012 at 2:35 pm

    I added some details about the drive circuit. I used the Pololu Stepper Drivers.

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