Guys....I am updating the v3.1 internals. The change does not have any effect on operation, assembly or fit with other existing printed parts.
The only part on the hardware list that will change is the magnet. Currently, its a 1/4" magnet, it now will be a 3/16". It doesnt effect any of the function of the device, just the amount of pull required to get the top cap off (slightly less pull required). If you have the 3.1 internals already, use the 1/4" magnet.
K&J Magnetics - Products
After today, this is the magnet to use.
K&J Magnetics - Products
The new internals are less complex and will have less thinner walled structures and the three internal parts will assemble more easily. I am making this change at this time because Shapeways went to new system and every time a print of this part is made, they send out annoying emails that the dimensions are at the threshold of their guaranteed spec, etc...
Here is what the new center frame looks like:
Older center frame with posts and larger magnet hole: