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Week 8 Assignments - Electronics Production

Group Assignment

The group assignment for this week was to:

  • Characterize the design rules for your in-house PCB production process: document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling.
  • Document the workflow for sending a PCB to a boardhouse
  • Document your work to the group work page and reflect on your individual page what you learned

Outcomes

The group assignment page for this week is on the 2025 Charlotte Super Fab Lab group site for Week 8 - Electronics Production.

What Was Learned

In the group assignment, we considered the use of the Roland Monofab SRM-20 milling machine for PCB manufacturing. We conducted trace width testing using the Mods environment for toolpath creation. More specifically, we explored the parameter settings for a 1/64 inch end mill as part of the process for both trace milling and through cutting. This involved both toolpath generation and milling with the SRM-20.

In addition, we went through the process for exporting Gerber files and uploading a PCB design to a board house.

This provided us the experience on:

  • How to use toolpath generation software such as Modes to prepare designs for milling
  • How to mill both traces and through cuts for milled PCB fabrication
  • How to send a design for board house fabrication

Individual Assignment

The individual assignment for this week was to:

  • Make and test a microcontroller development board that you designed

Outcomes

For the microcontroller board production, I planned to produce and test the board design from Week 6.

KiCad Trace Routing for XIAO ESP32C3 Development Board from Week 6

The board production process involved three primary steps:

  • Exporting SVG files from KiCad design
  • Exporting PNG files from Inkscape
  • Creating toolpaths using Mods
  • Milling the board

Exporting Design Files from KiCad

In order to export the PCB design from KiCad, I used the File > Plot... menu option to bring up the export dialog window.

KiCad Plot - Layer Export for Production

I selected the two primary layers in the Include Layers list:

  • F.Cu - for the copper traces on the front of the board
  • Edge.Cuts - for the outline of the board

I also selected the following optons:

  • Plot Format - SVG as the output format
  • General Options - Negative plot, so traces will be in white and background in black

The export produced the following SVG files:

  • week06-F_Cu.svg - SVG for the copper traces
  • week06-Edge_Cuts.svg - SVG for the board edge cuts

Using Inkscape to Touch Up Design Files and Export PNG

I opened the exported copper traces SVG file from KiCad into Inkscape.

SVG for Copper Traces Design in Inkscape

The standard footprint for the XIAO ESP32C3 includes a set of connectors on the back of the board for battery and other connections. These will not be used on the development board - the back of the board will be covered with insulating tape for production. Since it is not necessary to mill these connection points, they are manually removed from the design in Inkscape.

Revised SVG for Copper Traces Design in Inkscape

I used the Inkscape export functionality File > Export... to export the design in PNG format. To ensure good resolution for toolpath generation, the DPI setting for the export was set to 1000.

The same process was used for the edge cuts. I opened the exported edge cuts SVG file from KiCad into Inkscape.

SVG for Edge Cuts Design in Inkscape

The exported design showed only the edge of the board outline. To support creating the toolpaths around the board as a whole, I used the paintbucket tool in Inkscape to fill in the entire board shape.

Revised SVG for Edge Cuts Design in Inkscape

I again used the Inkscape export functionality to export the design in PNG format with a DPI setting of 1000.

Using Mods to Create Toolpath for Copper Traces

In order to create the toolpaths for trace milling and board cutting, I used the Mods environment.

I opened a workflow to create a toolpath targeting our Roland SRM-20 milling machine: programs > open program > machines > Roland > SRM-20 mill > mill 2D PCB.

Mods base workflow for Roland SRM-20 PCB Milling

In the read png component, I used the select png file option to select the PNG file for the copper traces. This updated a number of components in the Mods workflow.

In the set PCB defaults component, I used the mill traces (1/64) option in order to set the tool properties of the mill raster 2D component for trace milling with a 1/64 inch end mill.

Mods Components for Roland SRM-20 Setup with 1/64 End Mill

Mods Workflow with Copper Trace PNG Selected

In order to generate the toolpath, I first updated the Roland SRM-20 milling machine component to change the origin settings from x: 10, y: 10, z: 10 to x: 0, y: 0, z: 0, as we will manually set the origin for milling.

In order to enable file generation, I turned on the on/off component connecting the Roland SRM-20 milling machine component to the save file component.

With all of the settings in place, in order to generate the toolpath, I used the calculate option in the mill raster 2D component.

Mods Components for Copper Trace Toolpath Generation

The Mods workflow generated the toolpath for the given settings. The toolpath was viewable in the browser interface and also downloaded a .rml format toolpath file for the Roland SRM-20 Mill.

Toolpath Generated for Copper Trace Milling

Using Mods to Create Toolpath for Edge Cuts

I followed the same process for the board edge cuts. The two primary differences were:

  • Selecting the edge cuts PNG for input in the read png component
  • Using the mill outline (1/32) setting in the set PCB defaults component to update the settings in the mill raster 2D component

Mods Components for Roland SRM-20 Setup with 1/32 End Mill

Toolpath Generated for Edge Cuts Milling

Milling the Board

To mill the PCB development board, I used the Roland SRM-20 mill.

Roland SRM-20 Mill

To begin, I removed the previously used copper blank from the machine. I used double-sided tape to secure a new copper blank in the milling area.

Double Sided Tape to Secure FR1 Blank for Milling

FR1 Blank Secured in Place for Milling

For milling the copper traces, I used a 1/64 inch end mill.

1/64 Inch End Mill

I placed the end mill into the spindle and secured it with the hex wrench. In order to calibrate the start position, I moved the end mill into a starting X/Y position using the VPanel software controls. To calibrate the Z starting position, I released the end mill to allow for positioning, used the Vpanel software to adjust the spindle height, and finally re-secured the end mill.

Positioning for X/Y and Z axis calibration

Roland VPanel Software for SRM-20 Control

Set X/Y and Z Home Positions

In order to make the cut, I opened the Cut option for the SRM-20. I deleted the previous file that was in the listing. I added the copper trace toolpath file that was creatd using Mods. I started the job with the Output control.

Load Toolpath File and Start Milling

The SRM-20 began the copper trace milling process.

Milling PCB Traces Start

Milling continued to about the halfway point.

Milling PCB Traces Mid

Final milling at the end of the design.

Milling PCB Traces End

Once the milling process was complete, there was a lot of dust from the milling process. Clearing the debris from the board, the copper trace milling process seemed to be complete.

Milled PCB

In order to cut out the board edges, I changed to a 1/32 inch end mill, and followed the same Z-calibration process as for the 1/64. I left the X/Y calibration at the same position.

1/32 Inch End Mill

In order to start the edge cut milling, I followed the same process as for the copper trace milling in the VPanel software - removing the previous file, adding the edge cut toolpath file that had been created in Mods, and started the milling process.

Load Toolpath File for Edge Cuts and Start Milling

Milling Edge Cuts for the Board

Final Milled PCB

Soldering the Board Components

With the board ready, I began the process of surface mount soldering the components in place. The components to be soldered included:

  • XIAO ESP32C3 Board
  • 4 Position Connector for general I/O (D0-D3)
  • 2 Position Connector for I2C (SDA, SCL) and general I/O (D4-D5)
  • 2 Position Connector for 5V power output
  • 2 Position Connector for GND
  • 2 Position Connector for 3.3V power output
  • Pushbutton
  • Pulldown resistor for pushbutton
  • Orange LED
  • Resistor in series with Orange LED

I used the lab soldering station with magnifier for the soldering process

Soldering Station

I began the soldering process with the external connectors, in order to get some additional practice before connecting the operational components. Soldering took quite some time and there were a number of joints that needed to be re-done, using solder wick to clear.

Overall, the solder joints wound up mostly shiny, with some looking nicely formed and some on the lumpy side. I will need some additinal practice to refine the soldering technique, but the connections seemed to be solid. I tested each connection with the continuity testing function of the lab multimeter.

Completed Microcontroller Development Board

In order to test the board, I connected it with a USB-C cable to my computer. The power light came on, and the onboard LED was on constantly (it seems the default level for pin D6 is HIGH). But these were good signs.

In order to test the board, I needed to set up for connection and programming. I followed the software setup instructions on the Seeed Studio page for Getting Started with Seeed Studio XIAO ESP32C3. This involved:

  • Launching the Arduino IDE (this was already installed on my system)
  • Adding the ESP32 board package to the Arduino IDE
  • Selecting the XIAO_ESP32C3 Board and Port in the Arduino IDE

To test basic board function and programming, I used the example Blink program available in the Arduino IDE. I needed to adapt the LED pin in the example to be the XIAO D6 pin connected to the onboard LED.

Basic Blink
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// the setup function runs once when you press reset or power the board
void setup() {
  // initialize digital pin LED_BUILTIN as an output.
  pinMode(D6, OUTPUT);
}

// the loop function runs over and over again forever
void loop() {
  digitalWrite(D6, HIGH);  // turn the LED on (HIGH is the voltage level)
  delay(1000);                      // wait for a second
  digitalWrite(D6, LOW);   // turn the LED off by making the voltage LOW
  delay(1000);                      // wait for a second
}

I clicked the run button in the Arduino IDE to compile and load the program. There were initially some errors in connecting. A few adjustments were needed to make sure the correct port was selected along with the XIAO board. Once these were adjusted in the IDE for connecting, I was able to compile and run the program. The output was as follows:

Arduino IDE Connecting to XIAO ESP32C3 Development Board
Sketch uses 277730 bytes (21%) of program storage space. Maximum is 1310720 bytes.
Global variables use 11848 bytes (3%) of dynamic memory, leaving 315832 bytes for local variables. Maximum is 327680 bytes.
esptool.py v4.8.1
Serial port /dev/cu.usbmodem101
Connecting...
Chip is ESP32-C3 (QFN32) (revision v0.4)
Features: WiFi, BLE, Embedded Flash 4MB (XMC)
Crystal is 40MHz
MAC: 24:ec:4a:c9:9d:c4
Uploading stub...
Running stub...
Stub running...
Changing baud rate to 921600
Changed.
Configuring flash size...
Flash will be erased from 0x00000000 to 0x00004fff...
Flash will be erased from 0x00008000 to 0x00008fff...
Flash will be erased from 0x0000e000 to 0x0000ffff...
Flash will be erased from 0x00010000 to 0x00053fff...
Compressed 19440 bytes to 12467...
Writing at 0x00000000... (100 %)
Wrote 19440 bytes (12467 compressed) at 0x00000000 in 0.3 seconds (effective 523.7 kbit/s)...
Hash of data verified.
Compressed 3072 bytes to 146...
Writing at 0x00008000... (100 %)
Wrote 3072 bytes (146 compressed) at 0x00008000 in 0.1 seconds (effective 416.6 kbit/s)...
Hash of data verified.
Compressed 8192 bytes to 47...
Writing at 0x0000e000... (100 %)
Wrote 8192 bytes (47 compressed) at 0x0000e000 in 0.1 seconds (effective 655.7 kbit/s)...
Hash of data verified.
Compressed 277840 bytes to 153707...
Writing at 0x00010000... (10 %)
Writing at 0x0001ba60... (20 %)
Writing at 0x00023d6e... (30 %)
Writing at 0x00029fcf... (40 %)
Writing at 0x00030424... (50 %)
Writing at 0x000369e9... (60 %)
Writing at 0x0003d011... (70 %)
Writing at 0x00044e59... (80 %)
Writing at 0x0004b00b... (90 %)
Writing at 0x00051380... (100 %)
Wrote 277840 bytes (153707 compressed) at 0x00010000 in 2.1 seconds (effective 1037.7 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting with RTC WDT...

Finally, the board came to life with the basic blink program.

Development Board First Program - Basic Blink

Design Files

KiCad Exported SVG

Inkscape Exported PNG

Mods Exported Toolpath