We originally made this tutorial to help people who needed to mill PCBs using the Otherplan Public Beta before PCB support was implemented, but it’s still useful, so we’re keeping it available. FlatCAM, is free software that converts Gerber and Excellon (Drill) files to G-code, which you can then use in Otherplan. Here’s a screencast we made that shows how to use it, and there’s also a FlatCAM manual.
Things to Be Aware of When Using FlatCAM
You can only use one size of tool for each Gerber file. In contrast, Otherplan automatically uses the largest possible tool and only switches to a smaller tool when the larger one can’t fit. This allows for faster milling because larger tools can remove material faster. With FlatCAM, if any part of your board requires a 1/64 or 1/100 tool, you have to use that tool for your entire board. You could potentially avoid this by making separate Gerber files for parts of the board that require smaller tools, but that’s beyond the scope of this guide.
You can only have square outlines. This means that you can’t have custom board shapes like you can with Otherplan. However, this also means that you don’t need to export Gerber files for the board outline.
FlatCAM only makes one depth pass, so if you’re milling holes or a board outline, keep your feed rate low because you’ll be cutting through the entire board in one pass.
For versions earlier than 8.4, there’s no place to specify spindle speed, so you have to add it in the Prepend section when exporting your G-code. The command is S16400. If you’re using version 8.4, it’s in the same panel as the feed rate.
Not all PCB software programs create Gerbers and Drill files the same way, so you may end up with some misalignment, most likely with Excellon Drill files. If you’re using EAGLE, follow this tutorial to make FlatCAM use Trailing Zeroes with Excellon files. The scale may also be off by a factor of 10, so you can correct this by using the Scale option in the Selected panel for the imported file. If you encounter issues using Gerbers made in Altium, try using the Gerber X2 specification instead of RS274X.
The last issue, which is actually an issue with Otherplan, is that double-sided boards aren’t fully supported yet. But we just implemented support for the alignment bracket, so if you’re dying to mill double-sided PCBs, FlatCAM has a two-sided registration hole feature that may be useful in conjunction with the bracket.
With all that out of the way, we hope you enjoy the video and using FlatCAM!