Heaven help me - I've just bought a delta kit :-)

[curious aardvark]

nah just a k200 clone.
The extruder is in entirely the wrong place and the filament placement makes no sense at all given where the extruder is.
The 4020 is interesting, but think I'll stick to the 3030. it's the cheapest I've yet seen.

The marble machine - bb size is 64mm by 54 high. 2.5 inch diameter by just over 2 inches tall.
Printing the spiral screw is going to be interesting.
Assuming the track actually works :-) Slicing looks fine.

Oh yeah if you print this - do the spiral screw by itself. Even little spiderweb bits of filament give it issues - at the smaller sizes anyway.