1. Objective & Overview

The goal of this group assignment is to characterize the design rules for our in-house desktop CNC PCB production process. We documented the specific settings for our milling machine (such as speeds, feeds, and tooling types) and checked our limits to understand what minimum trace configurations can reliably survive without lifting or breaking.

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2. OpenBuildS CONTROL Software Workflow

To run and monitor our G-code files on the desktop CNC milling machine, we utilized the OpenBuildS environment. If you want to configure this software for your own computer, you can download it directly from the official repository site: OpenBuildS Software Download.

Step-by-Step Installation & Run-through:

• Installation: We downloaded the executable file, agreed to the local conditions, established the directory path, and ran the visual program installer until completion.
• G-code Loading: We launched the software dashboard workspace and used the "Open G-CODE" navigation menu button to fetch our exported .nc file from our computer.
• 3D Simulation: The interface automatically loaded a 3D visual workspace layout previewing all coordinates and cutting lines. We ran an accurate preview simulation tracking the tool movements to ensure total accuracy before spinning up our physical spindle tip.
• Connection Check: We linked our laptop via physical USB cable, selecting the matching active COM port and hitting the green "Connect" button. Tip: If you encounter an "Unknown error code 121", double-check that your hardware connection cord is tightly seated and free of loose vibration!

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3. In-House Machine Settings & Tooling

We finalized and tested the following exact parameter limits for our desktop CNC routing unit to guarantee clean isolation runs without accidental trace shorts:

• Trace Isolation Tool: 0.1mm 30° V-Bit (Engraving cutter tip).
• Outline Cut/Edge Tool: 1.0mm Flat End Mill.
• Bed Preparation: Clean flat sacrificial board bed. We applied heavy-duty double-sided tape tightly across the absolute bottom surface of our copper plate to fight machine tremors and stop board sliding mid-run.
• Z-Zero Calibration: Slowly lowered the router bit tip using micrometer manual jogging increments until it barely scraped into contact with the upper copper layer surface.

Our Critical Design Rule Findings: During our group characterization trials, we noticed that using thin 0.4mm trace width parameters in KiCad made the copper lines delicate and prone to breaking during high-speed routing passes. Under our facilitator's instruction, we updated our laboratory standard rule to a minimum of 0.6mm trace width. This change dramatically decreased board rendering mistakes and stabilized trace routing yields.

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4. Sending a PCB to a Commercial Board House

When our team needs complex multi-layered boards, small footprints, or protective solder masks that are difficult to complete in-house, we utilize industrial board houses. The universal workflow follows these sequential stages:

1. DRC Check: Run the manufacturer's Design Rule Check script inside KiCad to verify track spacings and drill hole sizes match their factory capabilities.
2. Export Gerbers: Generate standard fabrication files, making sure to include Copper Layers (Top/Bottom), Solder Mask, Silkscreen, and the essential Drill file (.drl).
3. Compress & Upload: Package all output files cleanly together into a single compressed .zip or .tar archive folder.
4. Review & Order: Upload the package to the online fabrication portal, use their visual web inspection viewer tool to inspect all layers, choose layer quantities, select color options, and submit for factory processing.