CNC PCB Drilling Machine using GRBL

Prototype PCBs are stuck between two bad options: chemical etching is messy, imprecise for fine holes and unpleasant in a college lab, while ordering fabricated boards takes days and adds cost to every design iteration. A small CNC drilling machine closes that loop — it reads the same Gerber and Excellon drill data a fab house uses and drills the through-holes on a copper-clad board in the lab. This project is that machine plus the workflow: a 2020-aluminum-extrusion gantry with three NEMA 17 steppers, an Arduino Uno + CNC shield running GRBL v1.1 for real-time G-code interpretation, and a DC spindle with an ER11 collet holding tungsten-carbide bits. Students learn feed, speed and peck drilling on real FR4, set work coordinates, home the machine, and understand how acceleration planning turns G-code into smooth motion. The documented KiCad-to-FlatCAM chain takes a student from schematic to a drilled board in one sitting.

1. The PCB is designed in KiCad (or Eagle) and Gerber plus Excellon drill files are exported.
2. The drill file is loaded into FlatCAM, where tool diameter, feed rate and peck depth are set and drill G-code is generated.
3. The copper-clad board is clamped on the spoil bed and all axes are homed with the GRBL homing cycle.
4. Work zero is set at the board corner (G92/G10) using the jog controls in the G-code sender.
5. The G-code streams over USB; GRBL plans acceleration and pulses the steppers through the A4988 drivers.
6. The spindle spins the carbide bit while the Z axis pecks each hole to depth, retracting to clear FR4 dust.
7. Holes are inspected; for double-sided boards the work zero is re-established and the second side is drilled.

Tech stack:

• Arduino Uno + CNC Shield V3 running GRBL v1.1 firmware
• NEMA 17 stepper motors with A4988 drivers (1/16 microstepping)
• 775 DC spindle motor with ER11 collet
• 2020 aluminum-extrusion frame, 8 mm linear rods with LM8UU bearings
• FlatCAM for drill G-code generation; Universal Gcode Sender for streaming
• 24 V DC power supply; mechanical endstops on all axes

• GRBL Motion Control: an Arduino Uno + CNC Shield V3 runs GRBL v1.1, interpreting G-code in real time with trapezoidal acceleration planning.
• 3-Axis Gantry: X/Y gantry on 2020 aluminum extrusion with linear rods and bearings; Z axis on a lead screw for controlled plunge depth.
• NEMA 17 Stepper Drive: three 1.7 A-class steppers on A4988 drivers at 1/16 microstepping for smooth, quiet motion.
• ER11 Spindle: a DC spindle motor with an ER11 collet chuck holds 0.6–3.175 mm tungsten-carbide drill bits with low runout.
• Homing and Limit Switches: mechanical endstops on all three axes; the GRBL homing cycle establishes a repeatable machine zero.
• G-Code Workflow: a documented KiCad → Gerber → FlatCAM → G-code-sender chain; drill files stream to the machine over USB.
• PCB Clamping Bed: a sacrificial MDF spoil board with clamps holds single- and double-sided copper-clad boards flat during drilling.
• Emergency Stop: a panel E-stop cuts spindle and stepper power independently of the firmware.

• Assembled and motion-tested 3-axis PCB drilling machine
• GRBL firmware pre-flashed with the machine configuration ($ settings documented)
• Wiring diagram, mechanical assembly drawings and full bill of materials
• FlatCAM drill-G-code workflow guide with screenshots
• Sample drill files and a test PCB layout for the first run
• Project report PDF, PPT presentation and viva Q&A document

• Positioning repeatability is a design target (±0.1 mm) checked with dial-indicator motion tests during your build — it is not a certified machine-tool specification.
• This is a drilling machine: it drills through-holes. Trace isolation milling with a V-bit is possible but slower, and is treated as an optional extension rather than the base claim.
• FR4 dust is abrasive and unhealthy to breathe — drilling needs ventilation or dust extraction plus eye protection; the safety guide covers this.
• Carbide bits are brittle and snap under side loads; the workflow guide uses conservative feeds, and breaking a bit while learning is normal — spares are listed in the BOM.
• Feed and speed must suit the bit diameter; aggressive settings stall the 775 spindle — the guide gives starting values per bit size.
• G-code streams over USB from a PC, so long jobs need a stable connection and should not run unattended.