spring corner design FFCPV3

2019-12-9: The PETG version works ok for printing with a 70C bed, but not for 100C bed when printing ABS. So print these in ABS.

Update: I made a new corner piece from scratch, but basically copying the previous design. I made two versions in PETG to have higher temperature tolerance. Both versions have narrower channels for the screw (M3) and a smaller channel for the square nut, so they stay aligned better.

The thick base (7mm thick) version V2 has a round channel for the spring that is below the channel for the square nut which holds the heated late to the FFCP base plate. That's why its 2mm thicker base, to accomodate the .160" dia spring. You have to force the spring into the channel a lttle at a time, but then it stays there without flying out when you install these onto the bottom of the build plate (using all of the old screws and springs from below).

The thin base (5mm thick) version V3 uses the channel of the square nut, plus a little more rounded cutout under the s