Well, this was a fun one! Sometimes it's really evident that different manufacturing methods have different capabilities and limitations, especially when trying to replicate something for 3D FDM printing!
So, this part, which is a rotating rubber brush that had broken in my vacuum cleaner, has a rigid core, a metal pin that sits inside a bearing and suspension bushing, and flexible rubber fins on the outside. Not the most obvious target for a 3D printed alternative, but we can't let that get in the way, right?!
Most importantly, this spare part needed to be easily printable, without supports, and without requiring any particular printer fanciness beyond being able to print flexible filament for the blades themselves.
A few design considerations:
* The rod core needs to be designed to print such that the layers run parallel to the long axis, for strength.
* The flexible blades need to be designed to print such that the layers run perpendicular to the long axis, also for strength.
* Blades need to be held in place such that they can't move with respect to the rod core, or else they'll shift under load during operation.
After a few changes of approach, the design ended up like so:
* Hexagonal central core, for easy printing on its side
* Sleeve-style blades, to be printed in flexible filament, and slipped onto the rod.
* Blades designed as segments, for easier printing.
* Tight press-fit flange end-pieces, printed separately. Where the original had sharp steps, the flanges in this model have graduations and vertical steps, for printability without supports, while still functionally appropriate.
* Incorporation of a cavity for an 10mm M3 bolt. Screwing this bolt all the way into the bearing flange will leave it protruding exactly the right length to take the bearing.
So, there we go, more amazing things we can do with 3D printers!