A heavy duty hydraulic positioner has headstock and tailstock carriages to support large and heavy work pieces to be processed in a manufacturing operation, such as robotic welding. Each carriage is independently movable along a column, and has a hard stop associated with each pre-program workpiece position, thereby providing accurate repeatability. Repeatability is further enhanced by linear, noncontact absolute encoders for the elevation axes of the headstock and tailstock, and rotary, noncontact absolute encoders for the rotary axes of the headstock and tailstock.