8. Electronic Production

Files

Overview

This week I learned how to mill a PCB board and how to solder componets onto it that worked

Group Work

This week, our team focused on electronics production, specifically characterizing the design rules for in-house PCB milling and submitting PCB designs to a board house. Noah handled submitting a PCB design, while I worked on characterizing the bits used for milling. Submitting a PCB to a board house, such as JLCPCB, allows for higher precision, multilayer designs, and professional features like solder masks and silkscreens. The process involves exporting Gerber files, configuring settings, and ordering the boards, with JLCPCB offering cost-effective prototyping options and efficient shipping.

For in-house milling, I characterized the cutting bits used, focusing on three flat end mills: 1/16”, 1/32”, and 1/64”. Each bit required specific feed rates, spindle speeds, and max pass depths to ensure clean and precise cuts. The 1/16” and 1/32” bits operated at 16,400 RPM with a feed rate of 59 in/min, while the smaller 1/64” bit had a reduced feed rate of 15 in/min to accommodate its finer cutting capability. These parameters were crucial in optimizing our milling process for accuracy and efficiency.

KiCAD

The first step to designing the PCB I was going to be using was making it in KiCAD. For my board, I wanted to starting testing out my final project so I desinged a board where a ESP32C3 would connect to pinheaders that I would have a servo connect to. The design was very simple since all I needed to do was wire the pinouts of the servo to the corrolating parts of the ESP. Those pinouts were 5 volt, GND, and control and I knew where to put what based off this image:

Once that was done I spaced out the componets in the schematic editor so that the line cuts would go well and not cut into each other. Once that was done I selected edge cuts and made a box around my design so that the board would cut and heres what it looks like:

Milling

To mill the board I first needed to learn how to use the Bantam Machine that we had in the lab. To do this I learned from my friend Tyler how to opperate the machine. After that the first thing I did was:

Setup

  1. Find a blank or slightly used PCB board that your design could fit on and mesure it using callipers. You needed to find the length, width, and height and input them each into the bantam software on the computer that is connected to the machine your using.

  2. Next you need to find the double sided tape and mesure the height of it without the cover on it and input that as your value for the offset. To get the bed to the front of the machine go onto the bantam software find the button that says jog and then press load and then the bed will move to the front of the machine. After that cover the bottom of the board (the non-copper side) with enough that it won’t move while its being cut and place the end covered onto the bed of the machine.

  3. With the values of the board set you can select the bit you are using to mill. The most common one for PCBs in my lab is the 1/32. If the bit you desire isnt on the machine then grab the two wrenches ontop of the machine and put one on the tube right above the bit and the other on the bigger tube that goes to the top of the machine. Whith the wrench thats on the smaller tube push it left to get the bit out while holding the other tube in place. Once its lossened you can remove the wrench on the bottom and with your fingers turn the tube the rest of the way while once again keeping the other wrench exactly where it is. Once thats doen you can put the new bit in and follow these steps in reverse by puting in the new bit in and screwing it with your fingers and then the wrench so that its tight.

  4. Then you can import your jobs into Bantam. Make sure that each job has the settings corerct and that the tool your using for them is selected correctly

  5. The cuts are going to start at the origin and so they need to be moved so that they fit on the board. Make sure the space you move the cuts to hasnt been cut before

  6. Once this is all done you go down to the bottom and press mill all if your confident or you can mill one file first to see if its in the right spot.

My first one failed since I used the wrong bit but the my second try worked

Clean Up

After it finished cutting, used a vaccum to clean up the scraps, removed the bit I was using and removed the board I made.

Soldering

Soldering on PCBs can be difficult since every part of the copper board could accidently make a bridge causing the circuit not to work. Thankfully for my design in was simple enough that it wasn’t something I worried about.

Testing

To test to see if my design worked I had ChatGPT write me a code that would make a web server where I could move the servo with the help of a digital joystick.

Reflection

This week wasnt that difficult for me since during the electronics design week I had milled a board before but I still had one area of difficulty. I had to make two boards since on the first one I was worried that the lines were to close so I also put the 1/64th bit as one for the track cuts. When it came time for the 1/64th bit, I accidently put the 1/16th bit in and it made the board unusable. Thankfully this was early in the week so I was able to mill again later and got it right.