3D printing systems and methods avoid build-compromising misalignments through the use of a self-leveling assembly that maintains a constant and typically fully parallel orientation between a build platform and the bottom surface of a resin tank. The present invention eliminates many of the problems associated with malleable tissue obstruction during surgery by providing the ability to deploy and retract a guard to create an area free of tissue interference. A call connection processing unit translates the home area identification number and the roaming area identification number into each other for call connection processing. Disclosed embodiments describe a collapsible support structure in which the rails are pivotally mounted to the beams. Bulk lifetime of the substrate is determined from the decay. Furthermore, some embodiments of the awning and shutter may feature a third position, substantially reducing the projection of the awning when in the opened position.