Though the Othermill is wonderful for a wide range of 2.5 and 3D applications, it still remains true to its roots as a very fine method to build and protoype circuit boards. We have a few trips and tricks we’ve discovered in milling boards that make the board-cutting process on the Othermill even more pleasant.
1. Radius your corners!
Since you’re cutting boards, and not using chemicals to etch them, you have to be careful about designing your board so your tool fits between traces. Radiusing your corners — or rounding them to fit your tool — will not only cut down on milling time, but it’ll cut down on smaller tool wear and make the boards more graceful.
Where the board has tight corners, set the curvature of the wire to be slightly larger than the diameter of the largest tool the mill is using.
For example, if you’re using EagleCAD, you can set corner radii when you use the routing tool, the miter tool, and the wire tool. If you’re using a 1/32" as one of the larger tools, just set the radius value to be 0.033" (0.081mm) or so. The 1/32" end mill will fit the corners, and if you’re using a smaller end mill for fine detail, you’ll save time that might otherwise be taken up with the smaller end mill making the corner perfect.
2. Edit your fine-pitch footprints in your parts library.
Make sure your tool can fit between SMD pads and components by adjusting the pads themselves. You’ll have to make sure there’ll still be enough contact between the part and the pads for the part to function. This is for more intermediate to advanced board designers. SparkFun has a nice couple of tutorials on this for EagleCAD users; however, it should also be possible in other PCB CAD software as well. Consult the documentation for your favorite package.
3. Try out BitBreaker Mode.
Otherplan has a nifty feature that provides more control for users, called BitBreaker Mode. BitBreaker Mode allows the user to adjust speeds, feeds, and trace clearance on circuit boards, as well as a host of other useful things. Be aware that if you’re not comfortable using the mill in default mode, or if you’re not experienced with how speeds and feeds work, BitBreaker Mode will most assuredly live up to its name and could break your bits.
To activate BitBreaker Mode, go to Otherplan > Preferences and check the BitBreaker Mode box. You’ll now see a button labeled “Advanced” in your plan file window. Click on this button to bring up the settings dialog.
4. Widen your trace clearance to clear excess copper off your board.
Does your board have an antenna? Do you want to get rid of extra copper to lessen interference? Are there small surface-mount parts on your board that would benefit from some extra space for soldering? BitBreaker Mode can help!
After turning on BitBreaker and clicking on the “Advanced” button, adjust your trace clearance to something really wide — 1" (25.4mm) usually does it. This will remove all copper that isn’t traces or pads from your board.
If you only need a small area on your board cleared, save tool life and machining time by creating a ground plane in your PCB software that excludes the area you want to clear. The ground plane, aside from efficiently connecting the ground on your PCB, will preserve the interstitial copper inside of it and let the machine remove everything outside of it.
We’re always happy to help. If you have tricks of your own or questions about any of these tips, contact us at firstname.lastname@example.org!