Electronic
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At Fab Lab Ulima we use the Roland Modela Pro II MDX-540, a precision CNC milling machine used for rapid prototyping through subtractive manufacturing processes. Subtractive manufacturing works by removing material from a solid surface using cutting tools, following paths generated by digital fabrication software.

The machine allows us to:

Different milling tools are used depending on the type of operation during the PCB fabrication process.

Different materials can be used to fabricate printed circuit boards, each with different mechanical and thermal properties.

For this process, we used the Roland Modela Pro MDX-540 to machine FR1 (Phenolic Paper) PCB boards following a precise step-by-step workflow to ensure accurate engraving and clean board cutting.

During Week 6, I designed my first PCB — but it wasn't good enough. For the Week 8 assignment, I decided to completely redesign the board. In the first version, I integrated many components directly on the PCB. After analyzing the circuit more carefully, I realized that several of these components could instead be connected using available free pins through headers.

Including them directly on the board was unnecessary and caused copper traces to cross each other, which could lead to fabrication problems during the milling process.

Before & After

Before — Version 1 (Week 6)

After — Redesigned (Week 8)

To redesign the PCB, I analyzed all the components and classified them according to their type and signal. The microcontroller used is the XIAO ESP32.

Pin Requirement Summary

The same procedure was followed to create three SMD pin connectors: 1×3, 1×4 and 1×6. Each one went through the same four steps described below.

1

Configure Component Properties

The component editor opens where the Name and Prefix fields are filled in on the right panel. The Añadir símbolo button is pressed to link an existing symbol and Nueva huella to create the footprint.

2

Verify Symbol and Associate the Footprint

The left panel shows the component structure in three levels: component, symbol and footprint. Each part can be edited separately by clicking on it.

3

Edit the Footprint in the Footprint Editor

Fusion 360 automatically switches to the HUELLA tab, where the 6 SMD pads are visible, numbered 1 to 6, vertically aligned on the top copper layer.

4

Link Pins to Pads

The Connect 1X06SMD window opens showing three columns: Pin, Platform and Connection. The Conectar button is pressed six times — once per pin — to complete the mapping. Finally Aceptar is pressed and the component is ready to use in the PCB design.

In Autodesk Fusion 360, go to the Manufacture tab and select the CAM Processor. From there, click on "Generate Gerber Files".

Save the files in an empty folder. Automatically, all the necessary files are generated. The most important ones are:

Since the PCB design was created in Autodesk Fusion 360, the files were exported as Gerber files. For the individual assignment, I used FlatCAM to generate the G-code for the CNC milling machine.

Then, I simulated the G-code using NC Viewer at ncviewer.com, which allowed me to visualize the cutting layers and verify that there were no extra paths or unwanted dots in the design.

For this individual assignment, I fabricated the PCB using the following specifications:

The PCB milling process consists of two main steps: engraving the copper traces and cutting the board outline. Both operations were performed on FR1 (Phenolic Paper) using the Roland Modela Pro II MDX-540 using the G-code files generated in FlatCAM.

1

Board Preparation & Setup

Clean the FR4 copper board with alcohol and secure it to the sacrificial layer using double-sided tape. Ensure the board is flat and well-aligned on the machine bed.

2

Machine Calibration

Set the X and Y origin at the corner of the board. Use the Z0 SENSE function to calibrate the Z-axis height accurately — this is critical for consistent trace width during engraving.

3

Engraving the Traces

Load the engraving G-code (copper top layer) into VPanel and start the machine. The V-bit tool traces all circuit paths into the copper, creating isolated signal lines. This step took approximately 15–20 minutes.

4

Cutting the Board Outline

After engraving completes, load the cutting G-code (profile/outline) and run the flat end mill tool. This separates the PCB from the sacrificial layer, creating clean edges.

5

Removing the Board

Once milling is complete, carefully remove the board using a spatula, being careful not to bend or damage the freshly milled traces.

In the ceramic test, the traces ended up being too thin. This happened because we used a very sharp milling bit, and during the Z-axis calibration, since the material is brittle, the tool went slightly deeper than expected and removed more material from the traces. Because of this, some of the paths became too narrow, which could affect the connectivity of the circuit.

The fiberglass test had a better finish with cleaner, more consistent trace widths.

After successfully milling the PCB, the next step was to populate the board with components and solder them securely. All components were soldered by hand using a traditional soldering iron.

• XIAO ESP32-C3 microcontroller
• Power button with pull-down resistor (10kΩ)
• Status LED with current-limiting resistor (330Ω)
• Decoupling capacitor (100µF) for stable power supply
• Multiple header connectors (1×3, 1×4, 1×5, 1×6) for external sensors and modules

Each component pad was heated with the soldering iron tip, and solder was applied to create a strong mechanical and electrical bond. Care was taken to:

• Avoid cold solder joints (which break easily)
• Keep solder away from adjacent traces to prevent shorts
• Ensure proper heat distribution to avoid damaging components

The final soldered board features all essential components neatly arranged and securely attached. The headers are clearly visible and ready to accept external sensor modules.

Before uploading code, the board was tested to ensure all solder joints were good and there were no shorts or broken connections.

A multimeter was used to check continuity of critical traces and verify proper electrical connections between components.

The following code was uploaded to the board to test the basic LED + sensor functionality. The code reads a distance sensor and controls the onboard LED.

#include <Adafruit_TinyUSB.h>

// HC-SR04 Ultrasonic Sensor Pins
const int TRIG = D9;
const int ECHO = D10;

// Onboard Status LED
const int MY_LED = 8;

void setup() {
  pinMode(TRIG, OUTPUT);
  pinMode(ECHO, INPUT);
  pinMode(MY_LED, OUTPUT);
  digitalWrite(MY_LED, LOW);  // LED off at startup
}

void loop() {
  // Trigger ultrasonic pulse
  digitalWrite(TRIG, LOW);
  delayMicroseconds(2);
  digitalWrite(TRIG, HIGH);
  delayMicroseconds(10);
  digitalWrite(TRIG, LOW);

  // Measure echo time
  long duration = pulseIn(ECHO, HIGH);
  float distanceCM = (duration * 0.034) / 2;

  // LED logic: ON if object detected close
  if (distanceCM < 10) {
    digitalWrite(MY_LED, HIGH);  // Hand close — LED ON
  } else {
    digitalWrite(MY_LED, LOW);   // No detection — LED OFF
  }

  delay(100);
}

✅ Board is fully functional! The LED responds correctly to object proximity:

• When an object (hand) is brought within 10cm, the LED illuminates
• When the object moves away, the LED turns off
• Response time is immediate with no latency

Below is a video showing the completed board with the status LED responding to proximity sensor input: