Week 8: Electronics Production

I) Group Assignment

Roland MonoFab SRM-20

I carried out Characterize the design rules for your in-house PCB production process: document the settings for your machine and Document the workflow for sending a PCB to a boardhouse with my classmates, but virtually, since I am in Madre de Dios and it was difficult for me to travel to Lima. So I connected virtually with my classmates and then replicated the same process at the FAB LAB of IESTP Jorge Basadre Grohman.

General description and use

The Roland MonoFab SRM-20 is a compact desktop milling machine widely used in digital fabrication laboratories such as Fab Labs. It is designed for precision milling of small objects, including printed circuit boards (PCBs), wax molds, plastics, and soft metals. In the context of electronics production, the SRM-20 is mainly used for: PCB milling (traces and outlines), electronic board prototyping, engraving fine details on flat surfaces, and small-scale digital fabrication projects. Its high precision and ease of use make it an ideal machine for educational environments and rapid prototyping.

a) Main characteristics

The SRM-20 stands out for its precision, compact size, and intuitive interface. It operates through numerical control (CNC) and is compatible with software such as MODS and VPanel.

• High-precision milling (ideal for PCB fabrication)
• Compact desktop design
• USB connectivity for direct control
• Compatible with the RML-1 command language
• Allows working with various materials such as FR1, wax, acrylic, and plastics
• Easy setup and operation for beginners
• The machine allows control of parameters such as spindle speed, feed rate, and cutting depth, which are essential for obtaining precise results

c) Disadvantages and limitations

Despite its advantages, the SRM-20 also presents some limitations:

• Limited working area, which restricts the size of projects.
• Low power compared to industrial CNC machines.
• Requires manual calibration of the origin (X, Y, Z), which can cause errors if not done correctly.
• It is sensitive to incorrect parameter settings, which may cause tool breakage.
• Milling time can be relatively slow for complex designs.
• Requires flat and well-fixed material to ensure precision.

b) Technical specifications

Specification	Detail
Model	Roland MonoFab SRM-20
Machine type	Desktop CNC milling machine
Working area (X × Y × Z)	203 × 152 × 60 mm
Maximum spindle speed	~7,000 – 8,000 rpm
Resolution	0.01 mm/step
Control system	RML-1
Connectivity	USB
Compatible materials	FR1, wax, plastics, acrylic, soft metals
Power supply	AC 100–240 V
Dimensions	Approx. 451 × 364 × 402 mm
Weight	~19 kg

To begin with the Characterize the design rules for your in-house PCB production process, I first downloaded the files. First, the engraving of the traces must be done, and finally the cutting of the board, in order to prevent the material from moving and causing an incorrect engraving. The line test files can be downloaded here:
https://fabacademy.org/2026/classes/electronics_production/index.html

During the manufacturing process of the printed circuit board (PCB) on the Roland MonoFab SRM-20, two end mills were used. The first was a 1/64" (0.4 mm) end mill, used to engrave and isolate the copper traces due to its small diameter and greater precision. The second was a 1/16" (1.59 mm) end mill, used to cut the outline of the PCB because it is stronger and suitable for making deeper passes through the board material.

Then the fixation of the XYZ axes is carried out, and the end mills are placed. This tutorial helped me a lot for this:
https://www.youtube.com/watch?v=rFRuc0VPWDM&t=3s

ROLAND WORKFLOW

The following shows the workflow that we followed in the Fab Lab when using the milling machine. We start from the basis that the trace files (files.rml) have already been generated previously.

VERY IMPORTANT: The milling machine must always be operated by only one person at a time, to avoid the spindle starting due to a command from one person while another person is manipulating it.

1. We turn on the milling machine using the power button located on the top of the machine and start the VPanel SRM-20 application on the computer.
2. We verify the connection between the milling machine and the computer, and check that the machine moves correctly by manually moving the head along the X, Y, and Z axes. At this stage, it is essential to be very careful with the movement scale to avoid the spindle crashing into any object.

There are three movement scales: x1, x10, and x100, where each click moves the head by the indicated number of steps, with 100 steps being equivalent to 1 mm. There is also a continuous mode, in which the head moves while the button is held down. This option is not recommended for the Z axis, since it moves too fast.

3. We prepare the working material by fixing the copper board to the sacrificial layer of the base using double-sided adhesive tape.
4. We place the end mill in the spindle and fix it with the corresponding adjustment screw. At this point, we have two types of end mills to choose from:
   • 0.4 mm for milling, which is the one we selected in this case.
   • 1.59 mm for cutting.
5. We adjust the X and Y origin position and save it by pressing Set XY Origin Point.

6. We lower the drill carefully, as close as possible to the material, without touching it.
7. We manually adjust the height of the drill by loosening the spindle fixing screw and lowering the drill by hand until it touches the material, then tightening the screw again.
8. We save the Z origin position by pressing Set Z Origin.
9. We raise the Z axis 3 mm by pressing the manual movement button of the Z axis three times at x100 scale.
10. Once the origin is established on all axes, we proceed to configure the Setup software.

11. We press CUT. Important: the milling machine cover must be closed; otherwise, this step cannot be carried out.
12. We delete any file that may already be loaded and import our traces.rml file.

13. We press the Output button and the milling machine starts working.
14. At this point, it is recommended to reduce the spindle speed to 20% to check that everything is going well and, if everything looks correct, increase it back to 100%.
15. Once the milling machine has finished and stopped, we can press the "View" button so that the spindle moves away and the bed moves toward us, after opening the machine cover. With a vacuum cleaner, we remove the copper dust deposited on the printed circuit board and check that the result is correct.
16. To perform the exterior cut, we raise the spindle and change the drill for the 0.8 mm one, repeating the Z axis adjustment in the same way as before, but being very careful not to change the XY origin.
17. We raise the Z axis 3 mm again, close the cover, and return to the CUT menu.
18. We delete the previous file and import the cutting file (file.rml).
19. We press the Output button and the milling machine starts again. In the same way, we can initially reduce the spindle speed to 50% to make sure that everything works correctly, and then increase it again to 100%.
20. Once the process is finished, we press View again and, after vacuuming the area, we can remove the printed circuit board.

PROBLEMS

To transform the PNG image into RML I used MODS: MODS (Modular Open-Source Digital Fabrication System) is a web-based tool developed by the MIT Center for Bits and Atoms that allows controlling digital fabrication machines such as CNC milling machines. It works through connected modules that transform design files into instructions for the machine, such as RML or G-code. In the case of PCB fabrication, it is used to convert images into cutting paths, allowing the traces and the board outline to be machined precisely.

For this, first you enter this link:
https://modsproject.org/

You click on programs: then in the search bar you type SRM-20 mill and select mill 2D PCB.

Blocks appear that must be configured. The main parts are:

1. Read png or svg, in my case I loaded the file into read png.

2. The other point is to choose the milling tool, in my case it was selecting 1/64 or 1/16 depending on whether it was engraving or cutting.

3. Then comes configuring the mill raster 2 block, here I changed the offset from 4 to 1.

4. My problem came in this part in the Roland SRM-20 milling machine block, because I fixed my coordinates at 0,0,0 but it always started on the z axis at 60.5, until I changed it to 0.1, as shown in the image, and it worked, but it only accepts that value; any other value I enter makes the start at 60.5. Even with this configuration, the engraving stayed too high above the board and the engraving was barely noticeable, so I had to lower the end mill an extra millimeter so that it could perform the engraving.

5. And finally the on/off button must be turned on so that when we press calculate the file that will be taken to VPanel can be downloaded.

6.

And here are the images of all the tests that I carried out.

I met virtually with instructor Vanezza Caycho to see the problem, but it could not be solved.

And how the engravings turned out in the various tests.

SOLDERING

Once the boards were milled, it was time to solder the components one by one. This was a very complicated task for me, since it was the first time I had soldered. I watched several videos and followed the instructions provided by my instructor Roberto Delgado.

You can review the PDF here.

Then I carried out the inventory and search for the electronic components. In my case, these were:

• A XIAO ESP32-C3 microcontroller
• Pin connectors to mount and remove the controller.
• A push button
• Three 1 kΩ resistors
• Two LEDs
• Four horizontal female connectors

The soldering process was difficult for me. It is a tin soldering process in which, after cleaning the surfaces to be soldered and applying a small amount of flux to prepare them, both parts are heated with the soldering iron. Once hot, the solder (tin) is applied, observing how it flows and joins both surfaces. After this, the soldering iron is removed and it is left to cool so that the solder solidifies and the two parts remain joined. Soldering while holding the component with tweezers and using a magnifying glass was quite a challenge for me.

But after practicing on other boards, I think I managed it and I was excited to see if it would work.

FUNCTIONAL TEST

Once I had the finished printed circuit board in my hands, it was time to check its operation. First, using the multimeter in continuity mode, I checked track by track to ensure that there was continuity where it should be. At the same time, I also verified that there was no continuity between the different tracks, which means that no unwanted bridges had been created during soldering.

Once the "cold test" was completed, the moment of truth arrived: the RP2040 was connected to a power source through its USB-C port to see whether it worked or whether the only microcontroller I had would burn; it was all or nothing.

The next step was to create a program for Arduino, upload it to the controller, and check whether the rest of the board also worked. In my case, since I still do not have enough experience to write the code completely on my own, I asked ChatGPT to generate it for me. The command I used was:

“I have a printed circuit board with a Xiao ESP32-C3 controller. Please provide me with an Arduino code to make the LEDs turn on and off when the button is pressed. I am attaching the schematic of my design in KiCAD.”

ChatGPT gave me the following code, which did work.

const int BOTON = 8;
int led1 = 9;
int led2 = 10;

void setup() {
  Serial.begin(115200);
  pinMode(BOTON, INPUT);
  pinMode(led1,OUTPUT);
  pinMode(led2, OUTPUT);
  Serial.println("Press the button...");
}

void loop() {
  int estado = digitalRead(BOTON);
  
  if (estado == HIGH) {
    Serial.println("leds on");
    digitalWrite(led1, HIGH);
    digitalWrite(led2, HIGH);
  } else {
    Serial.println("leds off");
    digitalWrite(led1, LOW);
    digitalWrite(led2, LOW);
  } 
  delay(200);
}
    

Once the program was compiled, I was able to verify that the LED turned on and off every time I pressed the button.

Reflection

During this week of electronic production, I better understood the entire PCB fabrication process, from design to assembly. One of the main challenges was correctly adjusting the milling parameters and understanding the limitations of the machine, such as axis errors, which forced me to be more precise in the origin calibration and in the Z-axis configuration.

I also learned the importance of considering the real available components from the design stage (such as resistors and packages), since this can directly affect the final assembly. The soldering process was key to improving my manual skills and understanding how small details influence the operation of the circuit.

In general, this week helped me connect theory with practice and develop better judgment to solve fabrication problems in real time.

Conclusions

• It is essential to correctly adjust the machine parameters (speed, depth, and origin) to obtain good milling results.
• Mechanical errors can be compensated with proper calibration and previous tests.
• The design must adapt to the available components to avoid problems during assembly.
• Soldering requires practice and temperature control to achieve clean and functional connections.
• Validating the circuit (connections, pins, resistors) is key to ensuring that the system works correctly.
• The integration of design, fabrication, and programming makes it possible to obtain a complete and functional electronic system.

Files

Here you can upload the related files for this week: