Creality-Compatible Filament Spool Load Cell Bracket and Spindle by erudioCAD

Last crawled date: 3 years ago

This is an adapter to carry an HX711 breakout board and a (relatively) standard 5 kg load cell that you can get for <$10 on Amazon on the standard T-slot top bar on Creality printers. It needs some fasteners, and you'll have to crimp on some connectors to the leads from the load cell if you want to be able to swap things out, but by and large it's pretty easy to set up. Additionally, you will need this Octoprint plugin, or at least that's what I use, to read this data.
Requires
I assumed using standard SHCS or Socket Head Cap Screws for all fasteners here.
M[fastener diameter]-[fastener length], both in millimeters and assuming you're using the standard rather than the fine pitch for the given size.
Fasteners to attach spindle to load cell
a. 2x M4-20
b. 2x M4 washers (to make sure you don't break the printed spindle)
Fasteners to attach load cell to bracket
a. 2x M5-14 (max length 16 mm)
b. 2x M5 washers (probably not necessary but spreads out the load nicely, this area is high load too so why not)
Fasteners to attach HX711 to bracket
a. 2x M3-12 (10 mm also acceptable, but any shorter and you won't get enough thread engagement)
b. 2x M3 nuts (sit in the pockets inside the bracket, no printed threads or interference fit holes here!)
Fasteners to attach the bracket to the frame
a. M4-10 (12 mm might work here, but it's cutting it close with the spacing inside to make sure the bolt doesn't run into the T-slot extrusion)
b. M4 washers (keep stress on the printed bracket low)
c. M4 T-nuts (lock the bracket into the T-slot extrusion, might not be necessary but definitely a good idea)
Bearings for the Spindle (probably not necessary but I like them and I designed for them so why not)
a. 2x 608 bearings
Dupont pin headers and connectors
a. 1x 6-pin straight header (board-side load cell connection)
b. 1x 6-pin connector (attaches to load cell wires)
c. 1x 4-pin right-angle header (nicety, keeps the wires close to the back of the board as shown in the images above)
d. 1x 4-pin connector (connector to load cell from Raspberry Pi)
e. 2x 2-pin connector (connector to Raspberry Pi pairs of pins for power and data from load cell amplifier)
If you don't have T-nuts handy (and I know I didn't) you can print pretty much anyone's design and it should work well enough.
Features
It has an interference fit with the t-slot thanks to those little tabs on the interior side so it might not even need fasteners to attach it, but I use them anyway to make sure stuff doesn't fall apart. There are crush ribs in the cavity where the load cell fits as well to keep the fit fairly loose but tight enough to keep things from sliding around too much while installing fasteners. I think having the amplifier attached is a nice touch, keeps things nice and tidy. The spindle has integrated bearing mounts of course, and that's been designed to be friendly to printers (no curved bottoms: flat faces have been cut to make it work nicely with supports). Really, the biggest upside is that you don't have to use those startlingly unreliable filament runout sensors. I always wondered what the advantage was of your printer stopping when it ran out of filament when... it was already going to do that anyway? Maybe if you want to swap in a new spool, but I've never had luck with that. Better I think to know exactly how much filament you have left.
However, do note that my load cell might be malfunctioning in the screenshot above, whoops!