Week 8 — Electronics production

Group assignment

Guangzhou (Chaihuo) — group documentation: in-house PCB fabrication on the lab CNC mill (operating notes and safety).

In-house PCB fabrication, CNC milling: operating notes

Equipment: Lab PCB CNC mill / engraver (single- or double-sided copper-clad stock, isolation routing plus outline cutting; exact model per nameplate and local training).
Use case: Quick-turn prototypes, coursework boards, small batches; not a substitute for a professional fab’s plating, solder mask, or surface finish.

Overview: The process uses a small-diameter end mill to cut isolation channels in copper, defining traces, and can cut the board outline. Design data must match tool diameter, cut depth, and work zero; mismatches often cause opens, shorts, or dimensional errors. Minimum trace width, spacing, and tool specs are defined by your lab’s published rules.

I. Recommended operating sequence (aligned with on-site steps)

Typical lab workflow: secure stock and tool, set zeros, then run the toolpath.

1. Prepare machining data and verify

1. Finish schematic and PCB layout in an EDA tool (e.g. KiCad, Altium, Eagle), then export Gerber (copper, outline, drill layers as required) and drill files; if the lab uses dedicated CAM software, merge layers and set the origin per its instructions.
2. In CAM, confirm units (mm), mirroring (top copper on a single-sided board is usually not mirrored; bottom copper per software guidance), and trace-width compensation against the actual tool diameter.
3. Check that the outline is closed and does not conflict with fixture keep-out zones.

(This step is done at the computer; no floor photo.)

2. Load and secure the copper-clad board

1. Clean the table and the underside of the stock so chips do not cause warp or uneven thickness.
2. Place the board within the machine’s usable travel, with clearance for clamps and the toolpath; for double-sided work, plan dowel or optical alignment if the lab provides it.
3. Clamp with lab-approved fixturing with enough holding force, and ensure clamps / bolts stay outside the toolpath envelope.

3. Change the tool (end mill, V-bit)

1. Install or remove tools only with the spindle fully stopped and the machine in a safe state (per lab procedure).
2. Seat the tool for the collet type and tighten to the specified torque; check flute length and stick-out for enough reach without excess overhang that causes chatter.
3. Match the tool diameter to the CAM settings (common isolation milling uses roughly 0.1 mm to 0.2 mm cylindrical end mills; confirm against lab inventory).

4. Position the cutter

1. Jog the tool to a safe height above the board so rapid moves cannot hit the stock or clamps.
2. Align the tool roughly with the programmed origin (board corner or locating feature) to match the CAM work coordinate system.
3. Confirm the dust shoe, guards, tool length, and clamps do not interfere.

5. Touch off and set work zero

1. XY zero is often a board corner or locating feature and must match the CAM origin definition.
2. Z zero is often on the top of the copper-clad surface or a lab-defined reference; Z error yields shallow cuts (copper not fully cleared) or deep cuts (substrate damage, broken tool).
3. The two images below show the initial state before touch-off and zero-related steps; the exact method (touch plate, shim, paper drag, etc.) follows on-site training.

6. Test cut and production run

1. For a new file, use a reduced feed override or single-block mode first and watch whether the first isolation pass fully clears copper and whether the sound is normal.
2. The operator must stay at the machine; on any fault, hit emergency stop immediately.
3. After the run, inspect for residual copper and burrs between traces; deburr if needed and spot-check continuity with a multimeter.

II. Safety and precautions

1. Personnel and motion: Do not clear chips by hand near a running spindle; do not wear gloves on rotating parts; tie back long hair; know where the emergency stop is.
2. Tool and workholding: A loose tool or loose board can eject; after each load or tool change, push gently to verify the board cannot shift.
3. Dust and copper swarf: Use dust collection; avoid inhaling copper dust; stop the machine before cleanup.
4. Electrical: Do not touch electrical parts with wet hands; route cables away from moving parts.
5. Program and coordinates: Mismatched zero, tool diameter, stock thickness, and CAM data is a common cause of shorts, opens, and crashes; after a board change or tool change, re-touch off or re-verify Z.