5. Electronics production¶
Group assignment:
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 your work (in a group or individually) Document your work to the group work page and reflect on your individual page what you learned
Individual assignment:
Make an in-circuit programmer that includes a microcontroller by milling and stuffing the PCB, test it to verify that it works.
Group assignment¶
The objective of the group assignment was to Characterize the design rules for our PCB production process: document feeds, speeds, plunge rate, depth of cut (traces and outline) and tooling, and document our work (in a group or individually). To begin, I will start with describing the hardware. The machine we used for our work is a mini cnc 1610 pro
the first part of the group assignment was to learn how to use the machine, this included loading the cutting piece, working with the software, changing the bit, and starting a carve.
To perform our first tests, we used the Flatcam software with different parameters to make observations. FlatCAM is an open source CAM-software specifically meant for PCB routing.
The thickness of the wick used for these tests has a size of 0.1 mm and the feed rate is 60mm/min we will observe three settings for the depth of cut, the first at -0.05mm the second at -0.07mm and the third at -0.1
During these tests, we learned a lot about the process by making many mistakes.
We started our tests by zeroing the z-axis by eye, which gave us no accuracy for the depth of cut. So our instructor showed us a simple technique with a piece of paper. The idea is to put the paper on the pad and move it back and forth across the flat surface while lowering the z-axis until the piece of paper can’t really move anymore.
V-bits, degrees, tip width, depth of cut and width of cut¶
There are different types of v-bits. It is therefore important to understand that the cutting width of the copper will depend on certain elements to be taken into account.
Looking at the picture below, we understand that the width of cut depends on the depth of cut, the tip diameter and the tool angle.
Some calculations were made to find the depth of cut
To make the calculations easier you can use this calculator
Milling¶
We used Mods to generate the .nc file needed for the milling machine. Then we used Grblcontrole-candle for the communication. Here are the procedures to generate the file and send the file to the machine.
Step 1: Open Mods > Right click > programs > open server program > G-code: mill 2D PCB png¶
Step 2: Select the image, and change the settings to you wanted or the machine needed, like tool diameter, cut depth, speed, offset… After all settings done, click calculate¶
Step 3: After saving the .nc file, open Grblcontrole-candle¶
The finished mill of the test traces
IDEAL SETTINGS FOR PCB V-BIT¶
Bit type: V-bit
Bit size: Select 0.3 mm
cut depth: 0.1
max depth: 0.1
cut speed: 2.5 mm/s
Plunge speed: 2.5 mm/s
IDEAL SETTING FOR PCB END-MILL¶
Bit type: end-mill
Bit size: 1 mm
cut depth: 0.5
max depth:1.5
cut speed: 2.5 mm/s
Plunge speed: 2.5 mm/s
Individual assignment¶
Once the materials were prepared as described above in the Materials section of the group assignment, I began working on my individual task of creating an FTDI board.
Milling¶
To make the traces
I used the following settings for milling my UPDI boards
Bit type: V-bit, Bit size: Select 0.3 mm, cut depth: 0.1, max depth: 0.1, cut speed: 2.5 mm/s, Plunge speed: 2.5 mm/s
For cut
Bit type: end-mill, Bit size: 1 mm, cut depth: 0.5, max depth:1.5, cut speed: 2.5 mm/s, Plunge speed: 2.5 mm/s
After cutting the copper, I put the board in alcohol to clean the remaining copper fragments
Assembling/Soldering¶
The next step was to build the UPDI board. The components needed for the board are listed below:
The Samsout 858D hotair soldering station and the klaryma soldering kit will be used for all my soldering task for this and the rest of the assignments for Fabacademy 2022. The hotair station was operating at 285 degress celcius. I used it to solder the microchip onto the board, the soldering iron from the Klaryma kit was used to solder any other component to the board and waws operating at 300 degrees celcius.
After soldering the components on the board, this is what it looks like.
Now we can connect the board to the computer to see if it works correctly. In my case I connected my board to a USB extension cable which is then connected to my computer
Programming/debugging¶
The first step in the process is to download and ensure that you have installed the FTDI driver onto your computer so that it will recognize it as a USB device. You can do this by going to ftdichip.com/drivers/vcp-drivers and downloading the driver for your OS.
After extracting the files to a folder, open the device manager and add the driver
Unfortunately after installing the driver, I realize that the board does not show up in the device manager, which means that there is a problem with the board.
I took the time to research the problem and fix it. The problem was that the copper traces were being lost during the soldering process and the depth of cut was a little too deep, resulting in a deeper cut width.
To repair, I used a jumper to connect the pins that lost their traces.
Now we can see that the usb device is showing correctly.
What went wrong/What went wel¶
Overall I was very pleased with this assignment, especially since electronics is one of my core areas of expertise but yet I had never had the experience of producing an electronic board from a mini cnc and a copper board 😅.
However one of the things that did not go well was the fact that the board I produced did not work. After taking the time to test all the circuits and components, I was finally able to identify the problem and fix it💪.