they actually aren't made of the same plastic. I was trying to cut the bad sockets off an old broken Bionicle part and glue the Hero Factory joints in it's place, did this with a broken original Bionicle joint and with one from a Glatorian, and my hot knife could cut through both Bionicle parts without too much effort, while the Hero Factory joint seems to have a higher melting point. my hot knife isn't adjustable, so at the same temp, it was harder to cut. I've 3D printed a couple parts trying to mimic the shape, and they are indeed sufficiently strong, but I think they did more than just change the shape.
