Custom Keyboard

Concept 

At the core of the project, I want to make a printed circuit board which is a bunch of tiny wires on a plate of fiberglass that connects the components together such as between the microchip, switches, and the usb port. The microchip can detect when each switch is pressed and will tell the computer that. 

I did a lot of research at the beginning regarding how to design the pcb, particularly the layout of the switches and electrical components. For the layout of the switches, I will place them in a standard QWERTY layout that most people are used to with the keys 19mm apart which is what the keycaps I used specified. I also did research on how the microchip needed to be wired, I learnt that I need components such as capacitors to clean the signals, a quartz chip to clock the chip, and resistors to tell the usb connector how much power the keyboard needs.

I will start off with trying to implement basic features and add more features such as more switches and adding more components throughout my iteration. Throughout the iterations, I also focused on changing the manufacturing method such as adding auto leveling and changing feed rates.

Iteration 1

For my first iteration, I made a small 2 by 2 macro pad in order to test and learn several things, I learnt how to operate the CNC machine, I learnt the software to design PCBs, and I was able to test the fitment of parts. This iteration had several traces cut off because the bit I used was broken and dull which I will fix by getting new tips. However I got the fitment of the components such as diodes and switches correctly which is a bonus. 

My eventual goal is to make a keyboard that incorporates a microchip however this needs a lot of room for wiring, dual sided pcbs give me double the room to do wiring. I tested dual sided milling in this iteration, the main thing I tested was realigning the pcb after flipping it, I did this successfully by drilling pocket holes into the pcb and base board where I can then use dowels to realign it after.

Iteration 2

Now I want to make a bigger version, I chose 42% this time because it is the smallest while meeting the criteria with all the letters. However this keyboard size is still bigger than the area the cnc can cut, what I found out is that, we can cut it once, move the pcb, then cut a second time however the issue is the software, most software only allows me to tile linearly in the y axis which is what most machines allow to push stock into but what I wanted was to rotate the pcb as there was a area on the cnc where the pcb could overhang. I overcame this by manually tiling by drawing rectangles and merging them diferentially which was tedious but worked, and then aligned them when spinning using the previously mentioned dowels.

A issue I encountered was leveling, cutting too deep resulted in rough burrs and broken paths because the V-shaped bit widens as it goes deeper, when I set it too high, only half of the pcb gets cut. Through experimentation, I discovered that a cutting depth of 0.06 mm create the best results. However, this depth is not achievable on larger PCBs because of variations in the surface level, leading to incomplete traces in some areas. I knew that most 3d printers also have this issue and they solve it by probing multiple points. My initial idea was to buy a dial indicator to measure the height of the pcb at various points manual and then put that into a algorithm to modify my gcode. I then realized that the CNC has a free input port on the controller board which I wired to the stock and the tip, so that the tip will lower until it is electrically connected to the pcb which the software can recognize as the zero in Y axis at that point, it repeats this at many points to get a height map and then uses the bi-linear interpolation algorithm to compensate in the g-code / movements.