This week's focus was primarily on electronics and so did not do much modeling. In addition, I have decided to gamble on the material used for 3D printing the head and try something new. I have also been considering alternatives to the "V" style jaw hing to avoid the Joker-like seam between the head and the jaw.
Electronics
I'm kicking myself at this point because I have focused pretty heavily on getting the electronics done and moved away from 3D design. It would have been wiser to wait and do this while printing and now annealing (see below) That being said, I've gotten to the point where I know exactly what electronics I plan on using and how they will be controlled.
Parts list;
- Arduino Nano - You'll need your own usb cable.
- HM-10 Bluetooth module
- USB to DC cables
- Prototyping Board
- 10,000 mAh Battery Pack - QC3 Compatible
- Charger for Battery Pack - QC3 Compatible
- Cellphone - I have an iPhone8
- Car mount button
- 2x 40mm Noctua NF-A4x10 5v fans
- 100x WS2812B Addressable 5050 smart RGB LED
- Misc (buttons, switches, resistors, DC female plug, KF2510 connectors, socket) breadboard mounts
- Low Impedance 26 AWG Wire - Needed at 5v for longer runs to avoid voltage drops that would cause color changes.
- nail polish and shrink tubing. To water resist the LEDs to prevent corrosion during cleaning.
The prototype worked out nicely, aside from the Bluetooth consistency. I committed this to a long term protoboard with proper pin mounts where the Arduino and Bluetooth module could be removed. I also added switches to turn the Bluetooth and fans on/off separate from everything else.
The car mount button will be used to make a button in the nose. While I have my phone in my pocket it will likely be the only way to change led functions.
The majority of the focus has been getting Bluetooth to work consistently to be completely honest. The best options for controlling the LEDs individually in my opinion is the FastLED library. I also set up the Bluetooth as a second serial communication using the SoftwareSerial library. Turns out that there are some timer/buffer compatibility issues between FastLED and SoftwareSerial.
The only solution I could get to work is moving the pins over for the Bluetooth TX and RX onto the hardware RX and TX pins of the Arduino. The downside to this is that you cant program the Arduino from the computer while the Bluetooth is connected to the Arduino. With the soldered socket adapters this isn't a big deal. The benefit is that I can test commands sent to the Arduino over the Arduino IDE serial monitor while the Bluetooth module is not plugged in.
I set up a simple communication method where letters and numbers would tell the arduino what to do. This loads and sets data into eeprom memory so you can see realtime what settings you are selecting on the LEDs. The best app I found for iphone is "BLE Terminal" which allows you to set up buttons that can labelled and send specific values. I ended up paying for the app (I think it was 5 dollars) so that the ads would stop. The really great thing is that this will continue to run and stay connected while the app is not in use.
At this point I have functional control of the different pattern, color, and mode selections. Moving forward I need to simplify the programming method so I can remove buttons and free them up on the app. You get four rows of five and I have used them all. I want a button that sets the global brightness of the LEDs and dont have a button or room for it at this point.
The color table is pretty basic, but 12 color selections should be fine. I might add more if I can free up enough buttons. I also need to set up more patterns. Currently I have "Black, Fade, Heartbeat, Rainbow and Solid" but I have room for 12 or more.
LW-PLA and VARIOSHORE TPU
Okay, so I have to admit I am not a huge fan of ABS, but I will use it if I have to. I was (and still am) willing to use it for this project because of its weight and strength. I was minding my own business and this video showed up in my feed on YouTube. At first I was like; "Okay, so your parts are lighter". But then I realized CNC kitchen was able to reduce the density of PLA to 44%. This would beat ABS outright ignoring part strength.
The density of ABS is 1.04 g/cm3. The density of normal PLA is 1.23 g/cm3.
Taking the density reduction of 44% for LW-PLA we can assume that the density should be more like 1.23 g/cm3 * .44 = .54 g/cm3. This means that the ratio of the head weight for LW-PLA should be; .54 g/cm3 / 1.04 g/cm3 = 51.9% as light as ABS per the same amount of volume.
From there, the trick will be making sure the parts are mechanically sound. I might need more material for reinforcement, but overall should end up being lighter and more flexible than an ABS print. Even if I end up using twice the filament at its full expanded density, the parts will be roughly the same weight.
Normally I would not consider PLA for mechanical applications due to its relatively low melting point and have reserved it for prototyping. Annealing PLA increases temperature resistance, but also causes warping and expansion/reduction of the material. The ratio of expansion/reduction tends to be different for XY vs Z. Warping on the other hand can be somewhat countered by a stress removing process or placing the part in sand while annealing to counter gravity. The stress removing process is basically bringing the parts up to just barely around glass transition temperature for an extended amount of time.
I had tried basic annealing in the past, but my simple stove at the time did not have the temp control to handle this without melting my prints. I now have a large countertop convection oven and am going to give this a real try.
My plan is to use more perimeters than I would have with ABS and scale the prints based on the expansion/reduction tests. Prints will be de-stressed at ~55 degrees C for 5+ hours and then annealed at ~100 degrees C for 1 hour and then brought back down to room temp slowly. This will all be while the parts are placed in sand.
Most of this info I got from CNC Kitchen as well, although I dont think he took de-stressing as far as he wanted to, and did not combine this with the sand method.
Varioshore TPU's trick is that it changes stiffness based on the temp its printed at. This should be a no brain-er aside from calibrating for how rigid I want the parts I'm going for. The density of TPU (flexible) is closer to normal PLA, but this is unavoidable for parts that need to bend. This will be primarily used for the ears.
Check out both of these filaments here. Remember that the PLA expands up to "3x" its size (44% density), so your actually getting pretty good bang for your buck as far as the amount of prints that can be done with the same length of material.
Jawline and Sculpting
As far as I can tell based on my research, the issue with fursuits where the jaw looks separated from the head is caused by the hinge having to be places too far back on the head. This placement is needed to allow the human jaw to actuate the mask's jaw. If this was placed further towards the nose, the human jaw would be above or behind the pivot point and would not work.
At the moment, I am considering a double hinge mechanism that would allow for the wearer's jaw to move a lever that then moves the mask's jaw at what would be a more natural pivot location for a canine further forward. If this is done correctly, it could potentially solve another issue.
Normal "V" style hinges jaws generally have issues where the movement of the jaw is limited. You have to move your mouth really wide to make good motions (from my understanding). A lever could be made to increase the range of the mask's jaw movement, but at the sacrifice of power. It would take more strength to move the wearer's jaw the same distance.
The other downside is that this mechanism probably would need to be printed in something stronger than PLA, regardless of the points in the previous section. I would likely take the time to print the parts with the actual lever in ABS.
This design work will take more time. I also am not completely happy with the shape of the head as it currently is. I'm hoping that moving the jaw further up will give it a look I am happy with. I also tried putting some teeth in, which look good to me but need to shape them into something that can be mounted with M3 screws/ locking nuts.