It is tricky a bit to pair two filaments in one spool. And the result is not ideal. As you can see in the first photo, the yellow part is wider. That's because I reeled it first. However, this is a working solution.

As for now, this separator applies only to BestFilament spools with dimensions ID = 73mm, OD = 190mm, inner width = 56mm.

If you're familiar with OnShape it will easy to you customize this thing to your dimensions.

The source is here.

Printing disclaimer

You must have a well calibrated printer including correct flow setting for the filament which you suppose to use. The printing tolerance - 0.15mm.

If you're not sure or didn't understand what I'm talking about - don't waste the time to make this thing. Or don't blame me after all that your printed parts don't fit together.

Also in some cases you'll need to use the tools (needle files for corners, drill bits for holes and etc.) to reach the best result from the printed model. Especially if use don't use Junction Deviation or Linear Advance. You shouldn't expect that the model will be fine immediately from the printer. At least not always :)

How to use my configurable models in OnShape

To get an access to the thing source you'll need an account in OnShape. It can be free, so made it for yourself.

Go to the document by the specified link.

Go to the tab "print setup". There should be a few configurable values in the upper-left corner. Change what you need. Wait while rendering finished then export parts from this tab (see in the bottom-left corner). They already oriented in the best printing position.

Creality

Ender 3

No

Yes

0.4/0.2

20% gyroid