The Circuit Graver Is a Desktop CNC That Can Etch PCBs with Precision - Hackster.io

In commercial printed circuit board (PCB) manufacturing, most boards start out as a piece of copper-cladded fiberglass. From here, the traces and pads from the design files are printed onto a mask, which is then applied before the boards are submerged into an acid bath. Although this allows for fine details and is more efficient, smaller batches tend to be more expensive and require the safe disposal of hazardous byproducts.

Zach Fredin wanted to go the alternate route of milling, wherein a rotating spindle carves paths into the board. The drawback here is that traces tend to be less precise and copious amounts of dust are created. To solve this problem, Fredin was able to build a machine, dubbed the Circuit Graver, which engraves traces into the copper without the need for a spinning bit.

The unique nature of an engraving machine like this required several changes from more traditional 3+1-axis milling machines. First, the tool's shape meant it had to be used directionally. Second, carving without the aid of rotation necessitates the addition of variable pressure on the bit to achieve consistent depths and trace widths. And finally, keeping the tool sharp throughout multiple runs would be paramount.

Starting in CAD, Fredin arranged the blade, a springloaded mount/holder, and a servo motor along a single, vertical axis. In this configuration, the servo is able to apply a variable amount of pressure while a stepper motor behind the entire assembly can rotate the holder to get the correct cutting angle.

After verifying the engraving concept was feasible, the rest of the machine soon took form. A pair of stepper motors, one for each axis, were then added to the base and attached to lead screws via timing belts and pulleys that gives the machine incredible resolution when carving fine details.

Unlike most other CNC machines that rely on a central control board to handle both communication with the host and driving the motors, the Circuit Graver leverages the Modular-Things project. This way, a small control board can be directly connected to each stepper motor and then wired together over USB to form a network of devices.

Once some quick calibrations had been run using paper and a pen, Fredin made a simple shift register-based LED circuit and watched how the machine was able to carve the thin traces between the IC's pads. The next challenge involved cutting a series of fine, curved lines which terminated at LEDs on one side and dual DFN HC595 shift registers on the other. Once all was said-and-done, the entire circuit was able to function exactly as intended.

To read Fredin's amazing write-up in more detail, you can visit the Circuit Graver project's page here.