Back when I was studying in polytechnic I did a course on Design and Fabrication, it teaches several designing and fabrication techniques (duh) from 3D printing, mold and casting to creating your own circuit boards. The best part about this course is that you are allowed to create anything you want for the final project as long as it meets several requirements. From there I decided I could make the Rina-chan auto emotion convert board.
Note that this was back in 2021, before Bandai announced their own Rina-chan board.
Prologue - The School Assignment
While I was allowed to make anything, in order to get Rina-Chan board to score during grading I had to
fulfill several requirements:
- Project must use the following fabrication techniques: 3D printing, CNC cutting, mold and casting
- Electronics must have an input and output, micro controller board must be made and programmed from scratch.
As a Tennoji Rina oshi the idea of creating Rina-chan board sparked and I went straight into researching on how to achieve this without the instructor approving this project, just because I know I could make it work, and also I don't know how to explain Rina-chan board to the instructor.
Nevertheless Rina-chan board got approved by the instructor and eventually scored me an A in the course : D
Alot of the images shown below were not the final design, some had their design changed at the last minute to make my life easier, and I ended up not updating the pictures of the changes, so I will try to explain the last minute changes I did in words.
Designing Rina-chan board
During research there were many attempts to create Rina-chan board, however one that stood out the most was from the Japanese YouTuber hamabeseaside.
Hamabeseaside's design was the closest to the actual one used on stage, furthermore he has a whole
Youtube video documenting the process along with 3 blogs about it. It was seriously helpful in visualizing how I wanted to make mine.
In his design, the emotions are controlled by a button panel, the best part is his attempts to make the board translucent so you still have visibility when wearing, which is something not even the official Rina-chan board worn on stage has.
From there I came up with my design specifications, and design brief which I had to show my lecturer before I can start fabricating:
Project Title: Neopixel mood-screen (a.k.a Auto Emotion Convert Rina-chan Board)
Functions:
- A screen made out of NeoPixel LED's that displays faces using pixel art.
- To be controlled remotely using Bluetooth.
Structure: - Head gear to comprise of 3D printed, CNC machined and Mold and casted parts.
Electronics:
- Screen to be made out of Neopixel LEDs, controlled via Bluetooth from an iPhone.
- ATTINY1614 board to be used for the program.
- Entire control circuit to be concealed inside the screen body.
What makes this slightly different from the other designs I found back then is that the design of Rina-chan board is not restricted to the size of an Arduino, as I am to custom design and fabricate my own 'Arduino board' so I am able to squeeze everything into the screen, and one thing I decided not to pursue is the visibility when wearing.
From here the process will be split into design, fabrication and electronics.
Designing Rina-chan board
I have decided that Rina-chan board will be comprised of 2 parts: the Screen and the Headgear. The screen is responsible for housing all the electronics and the headgear is mostly for aesthetics and allowing me to wear Rina-chan board.
I started off with the important part, the screen.
Initial sketches
The screen will be made up of the main frame and a panel with the LED lights, this makes it easier to assemble and I can print them in different colours.
The panel should be printed thin enough so the lights are visible when pasted on it. Back then I did not know I could buy such small neopixel lights so as a countermeasure I would need to bend the strips in a way not to crease it and cut off the connections.
The layout of the neopixel is inspired by hamabeseaside, in a creeper formation. I plotted the neopixel map on google sheets. This will come in handy when programming the different faces.
This more or less completes the ideation, now comes the challenging part of designing on CAD. For this project I used Fusion 360.
CAD design
I started with getting rough dimensions by measuring my own head. From there I started designing the front screen. The picture below is a phone screenshot of the initial design.
The screen comprises of 3 parts. The top screen where the LEDs will be stuck on and the frame will be 3D printed. The thickness of the top screen is thin so the lights can be seen through the screen when the LEDs is stuck on it.
For the back of the screen, I decided to machine it using a CNC cutter. The design is later changed to be a flat board so its easier to cut. This also fulfills the CNC machining requirement.
The picture above is the closest to the final design, this time with colour! The only changes is the imprint on the LED screen is removed and just a flat board. While the back board has a wood decal used on it, I used an acrylic board for it in the end.
Next is the headgear. Using the measurements of my head as a starting point, I started with creating a sketch.
From here I slowly extruded the different parts. I decided to make the head gear out of multiple parts instead of printing everything in a single piece so instead of painting I can just print out the parts with the colour I want. The image below shows one side of the head gear.
While everything can be 3D printed, I decided to make the flower piece out of resin to fulfill the mold and casting requirement.
Heres the final headgear design.
With that the full Rina-chan board design is complete! Now its hoping that everything actually fits together...
Fabrication
Here is a summary of the parts and what they are made of:
Screen (3 parts)
- LED panel - 3D printed
- Frame - 3D printed
- Back - Laser cut (acrylic sheet)
Headgear (3 parts)
- Cat Headband - 3D printed
- Headgear sides - 3D printed
- Headgear flower cap- Resin (mold and cast)
3D Printing
I started with fabricating the headgear. I thought 3D printing the parts would be easy but I forgot to add clearance between parts before printing so I ended up wasting time sanding and cutting the parts to fit.
The red and blue pieces were annoying and didn't fit at all no matter how much I sand, so I gave up and went back to include a 0.6mm clearance and printed them out again.
I ended up cutting the ring on the headgear frame so I can widen it to fit the parts.
One thing I little to no planning is how to fit the parts together. For whole parts I used super glue to fix them together, but for adjustable parts I left a hole there so I can attach them with screws and nuts.
For the cat headband and ear cups I spray painted them as the lab did not have the filament colour I wanted.
The screen was the easiest to print, learning from past mistakes I added clearance before printing them, and they were good to go fresh out of the printer.
For the LED screen I printed it as thin as possible as I was afraid the lights from the LED not being able to be seen on the other side, while it still holds the shape, for better or worse I realise It was too thin, but this problem is for future me to fix.
Molding and Casting
This part being made from mold and casting is not important at all, you could just 3D print the piece and be done with it, I had to do this to meet my school project requirements, but because it took a painful lot of time to do this I will just document this.
The process summary is making the reusable mold out of silicone, following by molding the actual part out of resin. The first step is to make the mold design.
This is the initial design of the flower cap for the headset.
and here is the final mold design.
This design is to be cut out of Styrofoam using a CNC machine. I generated the g-code using fusion360 and went to machine it. The final piece is shown below.
Silicone is then poured and left to cure. After a few days I broke it free from the Styrofoam.
The casting process is simply mixing the resin parts, removing air from the mixture using a vacuum chamber and pouring it into the cast and letting it rest.
I attempted the casting process multiple times and the picture above is the final time I attempted, all other attempts resulted in the mold bubbling out while setting, for this final version I left the mixture in the vacuum chamber longer and the result turned out beautiful, but I ended up making 1 good one, so the other side ended up being one of the failed result. Nevertheless it fits perfectly into the mask.
I
would have spray painted it white to match the original, but I got
lazy, and I was also under the impression that I will replace this with
3D printed versions after grading.
In the end both the Screen and Headgear are complete.
This concludes the designing and fabrication of Rina-chan Board, in the next part I will go through the process of designing the electronics (yes I had to fabricate the micro controller board) and programming.
Also I got bored and shrunk the entire modelo print a mini Rina-chan board! Though the lab only had red filament at that time so I ended up printing it in red, still cute though.
Part 2 (soon :tm:)
