How to Make Your Own PCB with a CNC Machine Using CircuitMill

A step-by-step guide to PCB milling, isolation routing, drilling, and board cutting

Making your own printed circuit boards doesn't have to involve messy chemicals, expensive equipment, or waiting for a PCB manufacturer to deliver your boards. With a small CNC machine and CircuitMill, you can turn your PCB designs into physical boards right in your workshop.

Whether you're building a prototype, experimenting with electronics, or developing a custom circuit, CNC PCB milling gives you direct control over the manufacturing process. You can design a circuit in the morning and have a working PCB the same day.

In this guide, we'll walk through the process of preparing your design, generating CNC toolpaths, milling copper traces, drilling holes, and cutting your finished PCB.

1. What Is CNC PCB Milling?

CNC PCB milling is a subtractive manufacturing process. Instead of using chemicals to etch away unwanted copper, a CNC machine uses a small cutting tool to physically remove copper from a copper-clad board.

The machine follows precisely calculated toolpaths, creating electrical isolation between traces, pads, and copper-filled areas.

There are three essential operations:

  • Isolation routing: A small engraving bit removes copper around traces and pads, leaving the electrical connections intact.
  • Drilling: The CNC machine drills holes for through-hole components, mounting hardware, and vias.
  • Board cutting: Finally, the machine follows the board's outline to separate your finished PCB from the surrounding material.

CNC milling is particularly useful for rapid prototyping, custom electronics, educational projects, and one-off designs. Unlike traditional chemical etching, it requires no etching chemicals and can be performed with an affordable desktop CNC router.

2. What You'll Need

Before getting started, gather the following equipment and materials:

  • A desktop CNC machine, preferably with a sufficiently rigid spindle and accurate Z-axis control.
  • A copper-clad PCB blank, such as FR-1 or FR-4.
  • PCB engraving bits, small drill bits, and an end mill for cutting the board outline.
  • A computer with your preferred PCB design software, such as KiCad.
  • CircuitMill to prepare your PCB manufacturing toolpaths.
  • A PCB fixture, double-sided tape, or another reliable workholding method.
  • A suitable dust-extraction system and protective equipment.

For beginners, FR-1 is a practical choice because it is generally easier to mill and produces less abrasive dust than fiberglass-based FR-4. Always use appropriate dust extraction, particularly when cutting FR-4.

3. Design Your PCB

Start by creating your circuit board in KiCad or another PCB design application.

For your first CNC-milled board, consider a simple, single-sided design with relatively wide copper traces, generous spacing, and through-hole components. These characteristics make the board easier to manufacture and reduce the risk of broken traces or incomplete isolation.

Before exporting your design, check that all traces are properly connected, that your board outline is complete, and that your design-rule checks pass.

Keep in mind that a typical CNC-milled board doesn't have plated through-holes. For double-sided designs, you'll need to connect the two sides manually, for example with soldered wires or copper rivets.

4. Prepare Your PCB with CircuitMill

CircuitMill is designed around the three essential operations needed to manufacture a PCB with a CNC machine:

  1. Drilling — component and mounting holes.
  2. Isolation routing — copper trace separation.
  3. Board outline — cutting the finished board.

Export the fabrication data from your PCB editor, including the copper-layer Gerber files, Excellon drill files, and board outline. Use the supported input format in CircuitMill to prepare the manufacturing operations.

Isolation routing

Choose a suitable cutting tool and generate paths that remove copper around your circuit's traces and pads. A wider isolation gap provides more electrical clearance, while a narrower gap allows denser layouts.

Drilling

Prepare the drill operations for your components and mounting holes. Different hole sizes may require different drill bits and tool changes.

Board outline

Generate the cutting path around your PCB. Configure the cutting depth and consider leaving tabs to hold the board in place until machining is complete.

Preview each operation carefully before running it on your CNC machine. Check that the traces, holes, and board outline are aligned and that no necessary copper has been removed.

5. Set Up Your CNC Machine

PCB milling requires relatively shallow cuts, so accurately positioning the board is essential.

Secure your copper-clad blank to the CNC bed. Make sure it lies flat and cannot shift or vibrate during machining. Even a small variation in the board's surface height can significantly change the width of a V-bit isolation cut.

Install your engraving bit, establish the machine's work origin, and accurately set the Z-axis zero relative to the copper surface. If your machine supports surface probing and height compensation, these can improve results on boards that aren't perfectly flat.

Before starting the spindle, perform a dry run with the tool safely above the board to verify the toolpaths and work coordinates.

6. Mill the Copper Traces

Isolation routing removes a narrow channel of copper around every trace and pad. Once the surrounding copper is separated, each trace becomes an electrically isolated conductor.

Use a sharp engraving bit and a conservative cutting depth. The goal is to remove the copper and just enough substrate to ensure reliable isolation, not to excavate deep grooves in the board.

For a typical copper-clad board with 35 µm copper, a shallow initial cut is generally preferable. The precise depth depends on your bit's geometry, spindle runout, board flatness, and machine accuracy.

After milling, inspect the traces for incomplete isolation, copper burrs, and damaged pads. A multimeter in continuity mode can help detect unintended connections.

7. Drill the Holes and Cut the Board

Once isolation milling is complete, switch to the appropriate drill bits and machine the component and mounting holes.

Use the hole sizes specified in your PCB design. Make sure to maintain the same work origin between operations so the drilled holes remain correctly aligned with the copper pads.

Next, install your board-cutting end mill and execute the outline operation. If the board is small, leave holding tabs or otherwise ensure it cannot move during the final pass.

After cutting, remove the PCB, clean up the edges, and carefully deburr any rough areas. Remove machining dust using appropriate extraction and cleaning methods.

8. Inspect and Assemble Your PCB

Your board is now ready for electrical inspection and assembly.

Check for shorts between adjacent traces, verify continuity along important connections, and inspect the drilled holes. Pay particular attention to fine-pitch footprints and areas where copper clearances are small.

Clean the board before soldering. Solder your components, taking care not to overheat or lift the exposed copper pads.

Since CNC-milled boards typically lack a solder mask, avoid accidentally bridging nearby traces with solder. For double-sided designs, install and solder any required via connections on both sides.

With these checks complete, you can power up and test your circuit.

Tips for Getting Better Results

Start with generous clearances. Wider traces and larger gaps are easier to mill reliably, especially on an entry-level CNC machine.

Keep your PCB perfectly flat. Board flatness is one of the most important factors in successful isolation routing. Use a properly surfaced spoilboard and reliable workholding.

Calibrate your machine and tools. Test your spindle speed, feed rate, and cutting depth on a scrap board before attempting a complicated design.

Always inspect your toolpaths. A toolpath preview can help you catch missing holes, incorrect board outlines, and routing mistakes before they become wasted material.

Why Use CircuitMill?

Turning a PCB design into machine-ready instructions involves more than simply exporting a drawing. Isolation routing requires accounting for cutter geometry, drilling requires accurate hole placement, and outline cutting must leave the final board with the correct dimensions.

CircuitMill focuses on simplifying these manufacturing operations so you can spend less time preparing toolpaths and more time building electronics.

Whether you're creating your first homemade circuit board or regularly prototyping new designs, the goal is the same: a straightforward path from your PCB layout to a finished board.