3D printers... When all you have is hammer, everything looks like a nail.
Spoken like someone who has never used a 3D printer. I have probably more tools than I should and I print more stuff than any other method. It just takes less time and the results are generally better due to part geometry freedoms. It's just all about the balance of tradeoffs and 3D printing has the least tradeoffs for more applications.
Sure the laser cutter is faster but you only get 2D and then design time goes up with lots of limitations to assembling things from flat sheets.
Fabricating from metal can be fast but only if you have enough of the right types of metal shapes and you are still limited to combining those into your final shape. You also have to spend the same amount of time on each part and the precision is limited by your skills.
CNC milling is great but not only do I still have to design the part in CAD, then I have more design limitations due to tool access, work holding, multiple operations. And then I have do to the CAM which not so bad but still takes a fair bit of time. Then I have to do all the setup with stock prep, work holding, tool setups, zeroing, etc, etc.
Casting/composites have good properties but I have to 3D print the molds/mold masters anyway plus the shape limitations and labor.
Rant over back to tires:
When looking at using foam vs fins for airless tires I can't see either getting around the weight. The pressurized foam of a mousse does sort of give foam that extra compression to weight ratio to help but then they have a shelf life even before you start working them and I bet many interested in airless tires want a tire that lasts a long time. When I was looking into making some airless fat tires there are some unpressurized (normal) foams that have impressive compression "firmness" per mass and they wouldn't actually be very much heavier than a standard tube but that only applies if your target is very low pressure.
Using foams with tubes in the hybrid approach like a tannus insert (what I'm using now) does have some up and downsides. You don't get full puncture protection but you do basically get full pinch flat protection. The pressure control is a bit problematic because as they are stock even at very low pressure in the tube you compress the foam a fair bit and so you don't have the two stage compression you would like. You can sort of resolve this by constraining the tube but it's tricky and I would say my results are OK but not amazing.
Some fin materials I think can have good lifespans. I've always liked the fin design because it offers an interesting advantage that you can make a tire really soft radially but axially resist motion. So you get a tire that has lots of grip and comfort but isn't squirrely and that's a pretty cool trick.
Maybe for a bike tire a fin approach of two layers of stiffness or material could be ideal and even work for road going higher pressure applications. So something like a stiff nylon PA6 section against the rim and a softer TPU section behind the tread. The stiff section only deforms under impacts while the soft TPU section provides that bit of squish for traction, small bumps, etc. Idea being you can use a stiff but less fatigue resistant material for lower mass and because you only deform it much under occasional impacts it lasts. Then the softer and high fatigue material for the part that gets deformed constantly.
