3D Printer Filament Scale

It is handy to be able to check the weight of filament on a spool to make sure that the filament does not run out while printing something that will take many hours to print.

I found this very clever design on cults3d https://cults3d.com/en/3d-model/tool/filament-holder-and-scales which I decided to build, here are some pictures of the build.

This is the front panel of the Scale using a 1.8″ TFT colour screen the button below it is the Tare button.

Just behind the screen on the top there is an HX711 module to amplify the signal from the load cell and digitize it. At the bottom is the micro-controller an Arduino Nano to process the weight from the load cell and prepare it for display.

This is an exploded picture of a strain gauge it actually measures 10mm x 5mm and the substrate is a flexible plastic, as the gauge flexes the resistance of the thin lines change.

Above is a picture of the load cell it has two holes drilled in the centre from left to right to make it more susceptible to bending. There are four strain gauges mounted on the load cell one on each side of the square rod near where the rod will bend the most when weighted.

These gauges are arranged as a Wheatstone Bridge as in the picture above, the two gauges on the sides will only balance the bridge, while the top and bottom gauges will respond to to a weight being placed on the rod top one positive response the bottom a negative response.

Front panel with bezel fitted.

Filament holder fitted to the Load Cell with the two hex screws.

Completed Project!!