Week 08 – Electronics Production

Assignment and Learning Outcomes

The weekly assignment is:

• Group assignment:
  • Characterize the design rules for your in-house PCB production process.
  • Submit a PCB design to a board house.
• Individual assignment:
  • Make and test an embedded microcontroller system that you designed.
  • Extra credit: make it with another process.

Checklist

In this page I answer the required questions:

• Linked to the group assignment page.
• Documented how I made the toolpath.
• Documented how I made the board: milled, stuffed and soldered.
• Documented that my board is functional.
• Explained the problems and how I fixed them.
• Uploaded my source code.
• Included a hero shot of the board.

You can see the group documentation here:

• Group assignment – Electronics Production

Group Assignment – Characterizing the PCB Production Process

For the group assignment we characterized the design rules of our in-house PCB production workflow. The objective was to understand the real limitations of the milling process and identify the minimum trace width, spacing, tool diameter, and machine settings that produce reliable PCB results.

In our lab we worked with the PCB milling machine and used Mods CE to generate the toolpaths. In León the workflow is prepared for the MDX mill, while in Ponferrada the process is adapted to the Mono Fab workflow and VPanel.

Test Files

We used the standard Fab Academy test files to evaluate the milling limits:

• linetest.traces.png
• linetest.interior.png

Machine and Tool

In our case we used a milling bit configured by default as 0.4 mm, which is an important reference for the trace width and clearance that can be manufactured safely.

• Software: Mods CE (mods.cba.mit.edu)
• Default milling diameter: 0.4 mm
• Important checks: machine origin, Z zero, speed, fixing of the tool, bed leveling

Roland MONO FAB SRM-20 – PCB Milling Workflow

In our lab the PCB boards are milled using the Roland MONO FAB SRM-20. The workflow combines the use of Mods CE to generate the toolpaths and the VPanel SRM-20 software to control the machine. The following guide summarizes the process used to produce the PCB.

1. Connection and Initial Check

• Open the VPanel SRM-20 software.
• Verify that the computer detects the machine.
• Test the movement of the axes using the cursor controls.
• Move X or Y slightly to confirm the machine is responding.
• Important: be careful with the step value (Step x10).

2. Computer Setup (Mods CE Project)

1. Open the web browser and access Mods CE.
2. Load the program:
   • Right click → Programs
   • Open Program → Machines → Roland → Mono Fab → SRM-20 → Mill 2D PCB
3. Import the PCB file (PNG or SVG).
4. Image interpretation:
   • White: copper
   • Black: no copper
5. Trace configuration:
   • Select PCB Defaults.
   • Use a 0.4 mm milling bit (Mill Traces 1/64).
   • Reduce the cutting speed to 2 mm/s (default value is higher).

3. Milling Parameters

The cutting speed depends on the milling tool diameter:

• 0.8 mm bit: 2 mm/s
• 0.4 mm bit: 1.5 mm/s
• 0.3 mm bit: 1 mm/s

The machine parameters must also define:

• Origin coordinates (X,Y,Z)
• Jog height
• Home position

4. Generating the .RML File

1. Activate the ON/OFF selectors in the output module.
2. In the Mill Raster 2D module press Calculate.
3. A preview window appears showing the milling toolpath.
4. Check the path carefully.
5. Save the generated .rml file.

5. Exterior Cut (Outline)

1. Import the PNG file corresponding to the board outline.
2. Interpretation:
   • White: material that remains
   • Black: cutting path
3. Select Mill Outline (1/32).
4. Adjust the speed to 2 mm/s.
5. Repeat the process: Calculate → Save .rml file.

6. Preparing the Machine

• Fix the PCB board on the sacrificial layer using double-sided tape.
• Insert the 0.4 mm milling bit and tighten the screw.
• Only one person should manipulate the tool.

Setting the X and Y Origin

• Move the tool using the cursor.
• Press Set Origin Point.

Setting the Z Origin

1. Lower the Z axis close to the PCB surface.
2. Loosen the screw slightly.
3. Let the milling bit gently touch the board.
4. Tighten the screw again.
5. Press Set Origin Point Z.
6. Raise the Z axis about 3 mm before starting.

Pics of the process

Initial web

Select machine

Charge png file

Set the cutting tool

Set the cutting speed

Results

7. Milling Process

1. Go to Setup → RML-1 → Millimeters.
2. Click Cut and load the .rml file.
3. Start with 20% speed for safety.
4. Press Output to start the spindle.
5. If everything is correct, increase to 100% speed.

Once the traces are finished, clean the dust and change the tool to the 0.8 mm bit for the outline cut. The Z origin must be adjusted again, but the X and Y origin remain the same.

What We Learned

• The real milling limits are not only defined by the design software, but also by tool wear, machine calibration, and bed leveling.
• The 0.4 mm tool sets practical limits for trace width and clearance.
• A correct Z origin is critical: if it is too low, the copper is overmilled; if it is too high, traces are not isolated correctly.
• Bed leveling strongly affects the quality of PCB isolation.
• Open pins and accessible headers are very useful for later debugging and for future assignments.

I also learned that PCB production requires attention not only in the design stage, but also in the manufacturing setup. Small errors in tool height, origin or tool fixing can easily ruin a board.

Individual Assignment – Embedded Microcontroller System

For the individual assignment I designed and fabricated my own embedded microcontroller board. The board was created in KiCad, prepared for milling, manufactured on the PCB mill, populated with components, soldered by hand, and finally tested to confirm that it works correctly.

Before finalizing the design, I checked that the PCB was ready for milling:

• Trace width prepared for the in-house process.
• Minimum spacing adapted to the milling limitations.
• Open pins / headers added for debugging and future assignments.
• Component placement reviewed to simplify soldering.

The goal was not only to draw a PCB, but to complete the full workflow: design + export + toolpath + milling + stuffing + soldering + programming + testing.

PCB Design in KiCad

Schematic Design

I started by creating the schematic of the board in KiCad. The design includes the microcontroller, programming connections, power routing, and the input/output elements required for my board functionality.

• Microcontroller: XIAO RP2040
• Power section: USB
• Input-output: button, connectors
• Open headers: added for future connections and debugging

PCB Layout

After the schematic, I moved to the PCB editor to place the components and route all traces. During this step I paid special attention to the trace width and spacing required by our in-house milling process.

• I kept the routing as clear and simple as possible.
• I checked that no traces were too close for the 0.4 mm milling process.
• I left enough space around pads to improve soldering reliability.
• I included accessible pins for future testing and expansions.

Preparing the Manufacturing Files

For the in-house milling workflow, I exported the PCB project from KiCad and converted it into PNG files suitable for Mods CE.

Gerber to PNG

I used the Gerber to PNG workflow to obtain the monochrome files needed by Mods:

• Traces PNG for copper isolation
• Outline PNG for cutting the final board contour

The conversion can be done using: Gerber 2 PNG by Kerala Team

1. Export Gerbers from KiCad.
2. Import the Gerber files into the converter.
3. Generate black and white traces and outline PNG files.
4. Download the generated images.

I documented it previously in Gropu assignement

Toolpath Generation in Mods CE

Once I had the PNG files, I imported them into Mods CE to create the toolpaths for PCB milling. This is the stage where the machine instructions are generated based on the traces and outline images.

Toolpath Workflow

1. Open Mods CE.
2. Load the traces PNG.
3. Select the proper machine program.
4. Configure the milling parameters.
5. Generate the toolpath for the traces.
6. Repeat the process for the outline PNG.
7. Export the files for the milling machine.

Important Parameters

• Tool diameter: 0.4 mm
• Cut depth: adjusted for copper isolation
• Max depth: adapted for board cutting
• Offsets: defined to isolate traces correctly
• Origin: checked carefully before milling

This part was very important because a correct toolpath determines whether the board can be milled successfully or not.

PCB Milling Process

After preparing the toolpaths, I moved to the milling machine to fabricate the PCB. I first milled the traces and then cut the outline.

Machine Setup

1. Fix the PCB material on the machine bed.
2. Insert and tighten the milling bit carefully.
3. Set the X, Y and Z origin.
4. Check the bed leveling.
5. Load the traces file and start milling.
6. Change to the outline process after checking the traces.

Important Notes

• Special care is needed when setting the Z height.
• The tool must be fixed correctly to avoid breakage.
• The machine should be controlled by only one person.
• In Ponferrada, I used a small vacuum cleaner and brush to clean the board and remove debris.
• A small ruler helped me check positioning during setup.

Stuffing and Soldering the Board

Once the board was milled, I prepared all the electronic components and soldered them manually. This was a delicate step because the board contains small pads and components, so clean soldering technique was important.

Tools and Materials

• Fine tip soldering iron
• Thin solder wire
• Flux
• Tweezers
• Brush and cleaning tools

I used the Fab Academy soldering references and debugging slides to improve the assembly process.

• Soldering basics
• Debugging slides

Assembly Process

1. Clean the PCB after milling.
2. Organize the components by value and package.
3. Solder the smallest SMD components first.
4. Continue with connectors, headers and larger parts.
5. Check component orientation carefully, especially LED polarity.
6. Inspect the board for shorts, cold joints or missing connections.

Testing and Functionality

After soldering, I tested the board to confirm that the microcontroller system was functional. I checked power continuity, programming connection, and the operation of the board features.

• I visually inspected all solder joints.
• I checked for shorts between power and ground.
• I connected the board to the programmer.
• I uploaded the firmware successfully.
• I verified that the board performs the intended function.

The board is functional because [describe here what it does: for example, “the LED blinks”, “the button changes the LED state”, “the sensor is read correctly”, etc.].

Problems and Fixes

Problem 1 – Incorrect Milling Depth

• Problem: At first, the traces were not isolated correctly because the Z origin was not set properly.
• Fix: I recalibrated the Z height carefully and repeated the milling process.

Problem 2 – Solder Bridges

• Problem: Some pins were accidentally bridged during soldering because the pads were small.
• Fix: I used flux, cleaned the tip, and removed excess solder until the pins were separated correctly.

Problem 3 – Component Orientation

• Problem: One component orientation needed special attention, especially the LED polarity.
• Fix: I checked the datasheet and corrected the placement before final testing.

These issues helped me understand that electronics production depends on both good PCB design and careful manufacturing and assembly. Small mistakes in milling setup or soldering can prevent the board from working, but systematic debugging helps to solve them.

Design Files, Source Code and Hero Shot

Design Files

• Schematic file – KiCad
• PCB file – KiCad
• Gerber files – ZIP
• Traces PNG
• Outline PNG

Source Code

• Source code

Hero Shot

This is the final result: my own fabricated and tested embedded microcontroller board, designed in KiCad, milled in-house, soldered manually and programmed successfully.

Summary and Reflection

This week helped me understand the complete workflow of electronics production, from PCB design in KiCad to file export, toolpath generation, milling, soldering, programming and testing.

I learned that the quality of a PCB depends on several connected factors: design rules, trace width, machine calibration, bed leveling, tool condition, soldering technique and debugging process.

I also learned the importance of designing with manufacturing in mind. A PCB is not only a digital drawing: it must be possible to mill it correctly, solder it reliably, and test it easily. That is why open pins, clear routing, and good component placement are so important.

The final result was a functional microcontroller board, and this assignment gave me much more confidence in producing my own custom electronics for future Fab Academy work.