Parametric Refill Spool Using Upcycled Cardboard Spools

A couple of caveats:

1. The attached models are examples only. You'll need to take measurements to match the cardboard spool and filament refill you have.
2. This is experimental. For all I know, the damn thing could fall apart after I use it for a while, and spill filament all over the place.

Don't say I didn't warn you.

That said, this design has two advantages over a fully 3D printed spool:

1. It uses less than half the filament and print time.
2. It reuses at least part of your leftover cardboard spools.

Now, to use this, you'll need to adjust the parameters:

• fid: This is the inner diameter of the flange (i.e. hole in the cardboard rim). When measuring this, keep it as close to the actual value as possible.
• fth: This is the thickness of the cardboard rim.
• rw: This is the width of the refill. Better to err on the larger side.
• rid: This is the inner diameter of the refill. Better to err on the larger side.
• wth: This is the wall thickness. The greater the value, the more robust, but the more filament used.
• cl: The clearance gap between the spindle and the locking hubs. The 0.4mm value seems to work well.

The attached STL files worked for me using an Overture refill and an Overture cardboard refill. Chances are you'll need to adjust based on what you've got on hand.

Printing

I printed in PETG for a PLA spool. Depending on what filament you're spooling and how much you need to use a dehydrator, you may need to use a more durable material.

You'll need two hubs and one spindle.

Assembly

The hubs lock into place when rotated 60° clockwise. The rims are sandwiched between the hubs and the spindle. Remove the restraining straps from the refill only after both hubs are locked in place.

Update 2025/8/4

I added a boolean parameter to the code to generate an alignment peg for refills with a notch. I've tested this with an Overture refill and it seems to work well.