Week 08 | Electronics Production
Group Assignment
This week's group assignment consisted of characterizing the PCB fabrication process using the equipment available in the laboratory. The objective was to understand the workflow for producing printed circuit boards, including milling the copper traces with a CNC machine, drilling the component holes with a bench drill, and cutting the board using a manual shear cutter. The activity was carried out in the Electronic Laboratory of the Pontificia Universidad Católica del Perú (PUCP).
The complete documentation of the group work can be found in the following page:
Group assignment documentation
Individual Assignment — Week 08
During this week the complete process of fabricating, assembling, and testing a printed circuit board (PCB) was carried out in the electronic laboratory of the Universidad Católica del Perú - PUCP. The objective was to understand the full digital fabrication workflow for electronics, from the design files to the final functional board.
1. Preparing the PCB Design in KiCad
The first step consisted of preparing the PCB design previously created in KiCad. Before exporting the file, the PCB was reviewed considering the limitations of the CNC milling process. Since the board would be fabricated using a subtractive method, the design parameters had to ensure that the milling tool could physically reproduce the geometry.
The trace width was set to 0.4 mm, with a clearance of 0.4 mm between traces. These values were defined based on the limitations of the CNC milling process, ensuring that enough material could be removed between traces to achieve proper electrical isolation.
Design rules configuration in KiCad showing trace width and clearance values used for CNC milling.
In addition to the trace width, several design parameters were defined in KiCad to ensure compatibility with the CNC milling process. The clearance between traces was set to 0.4 mm. Although vias were not used in this single-sided design, default values were configured to maintain consistency in the rule set.
The PCB was designed as a single-sided board, avoiding vias and minimizing the complexity of the routing. In this design, the ground was not routed as a separate trace because the copper surface of the board was used as a ground plane.
After completing the PCB layout in KiCad, the design was exported as an SVG file. This vector format allows the circuit traces to be directly processed and converted into toolpaths.
PCB layout prepared in KiCad before exporting the design as an SVG file.
3D visualization of the PCB showing component placement and board configuration before fabrication.
2. Refining the Design in Inkscape
The SVG file was opened in Inkscape to prepare the geometry for fabrication. In this stage, the circuit traces are represented as vector shapes that define the areas to be preserved during the milling process.
First, the image was mirrored to ensure that the circuit would be correctly oriented when milled on the copper board. Additionally, some circuit paths were slightly opened so that the ground connections could properly merge with the rest of the copper surface.
SVG file edited in Inkscape showing mirrored design and adjusted paths for proper ground connection.
This step was essential because it refined the vector geometry and ensured that the design was correctly prepared for toolpath generation.
3. Generating the G-code
After refining the design in Inkscape, the next step was to generate the G-code, which contains the instructions required for the CNC milling process. This step translates the vector geometry of the PCB into toolpaths that define how the milling tool will move to remove copper and isolate the traces.
The toolpaths were generated based on the contours of the traces, following an isolation strategy. In this approach, the milling tool moves around the edges of the conductive paths, removing the surrounding copper while preserving the areas that form the circuit.
This process was carried out using a toolpath generation workflow within the Inkscape environment, where the vector design was interpreted to define the machining paths. Parameters such as tool diameter, cutting depth, and feed rate were considered to ensure that the generated paths were compatible with the physical characteristics of the CNC machine and the milling tool.
The resulting G-code defines the precise movements of the tool, including the regions where material must be removed to achieve electrical isolation between traces. Once generated, the file was prepared for visualization and execution in the CNC control software.
4. PCB Milling
To fabricate the board, a Genmitsu CNC milling machine was used.
Tool Geometry and Its Impact on Design
The milling process was performed using a V-bit engraving tool. This tool does not have a constant diameter; instead, its effective cutting width depends on the cutting depth.
This makes Z-axis calibration critical, since small variations directly affect the width of the cut and the isolation between traces.
For this reason, the selected design rules (0.4 mm clearance) provide a safety margin to ensure proper isolation.
Candle Configuration and Machine Setup
The PCB board was fixed to the machine bed using double-sided tape to ensure stability. A V-bit tool was installed, and the Z-axis was calibrated manually.
- X and Y axes: positioned at the lower-left corner of the PCB.
- Z axis: calibrated manually by touching the copper surface.
Toolpath visualization in Candle used to verify the milling paths before executing the cut.
Milling Parameters
- Machine: Genmitsu CNC
- Software: Candle
- Tool: V-bit engraving tool (~0.1 mm tip)
- Feed rate: ~100 mm/min
- Plunge rate: ~50 mm/min
- Cutting depth: ~0.1 mm
These parameters were selected to ensure precise material removal and proper trace isolation.
During milling, the CNC removed copper around the traces, transforming the digital design into a functional circuit.
PCB milling process showing copper removal and trace isolation.
5. Drilling and Cutting the Board
After the milling process was completed, the board was removed from the CNC machine and the required holes for the electronic components were drilled. A bench drill was used for this task in order to achieve precise and controlled holes for the component leads. Once the drilling process was finished, the board was cut to its final shape using a manual shear cutter. In this case, the PCB was trimmed into a hexagonal shape, which is part of the visual design of the electronic module.
Drilling process of the PCB using a vertical drill press, where through-holes for electronic components are manually created after the milling stage.
Milled PCB showing trace isolation and perimeter cut, where the copper has been removed around the traces to create the electrical circuit.
PCB cutting process using a manual shear cutter to define the final board dimensions and separate the piece from the larger copper sheet.
6. Component Assembly and Soldering
The next step was the assembly of the electronic components. The components used in this board include resistors, pin headers, LEDs, buttons, and the Seeed Studio XIAO ESP32-C3 microcontroller, which serves as the main controller of the circuit.
All components were soldered manually using a soldering station, solder wire, and cutting tools to trim the excess leads.
During the soldering process, special care was taken to control the temperature of the soldering iron and apply the correct amount of solder in order to avoid cold joints or unwanted bridges between traces.
7. Cleaning the PCB
Before assembling the components, the PCB was cleaned using isopropyl alcohol and a brush. This step removes copper dust, grease, and residues from the milling process, ensuring good electrical contact during soldering.
8. Electrical Verification
After completing the assembly, the circuit was tested using a digital multimeter and a power supply.
The verification process included checking the continuity of the traces, verifying the correct voltage supply, and ensuring that no short circuits were present. These tests confirm that the PCB was correctly fabricated and assembled before running the microcontroller program.
Reflection
This activity provided a complete understanding of the PCB production workflow in a digital fabrication laboratory. The process integrates several stages including electronic design, vector file preparation, CNC milling, manual assembly, and electrical testing. Working through each of these steps helped develop practical skills in digital fabrication, electronics manufacturing, and safe machine operation.
Download Files
The design files used in this assignment can be downloaded below.
