Various embodiments provide a timing belt tensioner for a 3D printer and the 3D printer. In those embodiments, the timing belt tensioner includes: a mounting frame, an idler and an elastic member, where the idler is connected to the mounting frame, and a timing belt of the 3D printer is wound around the idler, and is configured to drive a movement mechanism of the 3D printer to move on an XY plane; and the elastic member is configured to connect the mounting frame and a base of the 3D printer such that the mounting frame drives the idler to slide to a balance position relative to the base under an elastic force of the elastic member. When at the balance position, a balance is reached between the elastic force of the elastic member and a tensile force of the timing belt acting on the idler.

A tensioning apparatus for a belt including a pulley defining an outer surface to receive the belt and a trolley including a mount configured to support the pulley for rotation, a first bushing, a second bushing, and an interior cavity. The tensioning apparatus includes a biasing member disposed within the interior cavity and an adjustable length arm assembly including a fixed-length portion and an adjuster portion. The fixed-length portion includes a pivot mount for rotatably mounting the tensioning apparatus. The adjuster portion includes a fastener threaded to the fixed-length portion and an engagement member that engages and deforms the biasing member in response to adjustment of the fastener. The first bushing and the second bushing establish a sliding interface along an outer surface of the adjustable length arm assembly for movement of the trolley.

A shuttling mechanical tensioner for control of chain drives with alternating tight and slack chain strands. The shuttling mechanical tensioner allows for chain control on an outside face of the chain strand or an inside face of the chain strand.