A trio of parts that will allow you to suspend your spool on a 80x12.7x12.7mm load cell for processing remaining filament in an Arduino MCU with an OLED display and interface buttons.
This was designed to fit into the stock Ender 3 bracket in place of the hollow filament holder, and for the load cell to be attached to both bracket and spool with the appropriate M4/M5 hardware for the load cell.
I printed the bracket at 100% infill, as it will be supporting the entire weight of the system, but that may be overkill. You're welcome to experiment. The rest I printed at a lower, but still pretty high, infill. I tend to overbuild things, as you can probably tell from this design.
The spool holder is designed to take 4 10mmOD x 5mmID bearings for the spool to roll upon, and should press fit into place with little trouble. If they are too loose and threaten to fall off, a little dab of adhesive on the inner race should secure them in place.
This panel will fit an Arduino Nano, as well as an HX711 Amplifier board on the rear portion, and a trio of long tac buttons, beeper, and 0.96" I2C OLED display on the front.
I printed the front at 80-100% infill, as it is quite thin and should be as strong as possible. The rear can be done as full as you like, but I tend to err on the side of strength over weight, since even at 100% infill, its less than 20 grams.
10kg Load Cell and HX711 Amplifier
0.96" I2C OLED
Also requires some tact switches (I used 12x12x10mm switches, but you could use any switches that protrude from the case, if you resize the button holes. Also used is a simple piezo buzzer and three 10K resistors.
The buttons are glued into place. The Nano sits over the pegs and the pegs can be melt-flared to hold the Nano in place if desired. The HX711 is secured with double sided tape to the ceiling of the rear of the box, because they come in various form factors, making placing mounting points difficult. The OLED display can be placed on its mounting location and secured with short M2 screws, or simply a dab of hot glue in the mount holes.
This is not the final version, as I don't actually have the load cell to ensure it works yet. However, the code for driving the I2C OLED display, as well as taking button input functions. I will soon create the wiring diagrams for the buttons and other items, but they are based on the Arduino documentation examples for buttons and the like using external pull-down resistors.