US Patent 10308038 Universal part holder with conformable membranes

An apparatus for holding three-dimensional parts for printing includes a frame with sides and a solid bottom and a part gripping membrane mounted across the face of the frame. A biasing membrane is mounted at the midpoint of the frame height to form an air chamber between the frame bottom and the biasing membrane and a vacuum chamber between the biasing membrane and the part gripping membrane positioned on the face of the frame. To grip a part, the gripping membrane is stretched over the part, positive pressure is applied to the air chamber to compress the granular material within the air chamber and further stretch the gripping membrane over the part, and then vacuum is applied to the vacuum chamber between the two membranes to maintain the granular material compression and grip on the part when air pressure is relieved from the air chamber.