Aluminum platform arms for Duplicator4 3d printer

This design replaces the original plastic arms and acryllic plates. All aluminum, except the BuildPlateCorners, PlateClamps and TrimKnobs are printed parts, ABS. The original linear bearings are re-used in this design, as are the heated buildplate parts, springs, bolts and nuts. The springs and long bolts are moved to the corners of the buildplate, giving more accurate levelling compared to the original design and... No more warping of the arms when the buildplate heats.