Print with PETG or ASA. 
4-5 walls minimum - high infill recommended (especially for “Beam”)

Hardware:
4x M3 hex socket screws (M3*14)
4x M3 nuts

"Top" and "Handle" require supports on the inside. There is a 1mm clearance on there so left over support segments will not interfere with movement of other parts, although i suggest using PVA as a support interface.

Use color painting (or equivalent) for “Top”
 

Intended usage:
 

“Spring Top” contains hole for a spring:

Diameter: 6mm // length 16mm (use a longer spring and pre-compress it)

Nuts are press-fit, but may have to be heat-set if your printer tolerances aren't perfect