An injection mold with locking device comprises a fixed backing plate and a fixed mold part plate which are connected to each other by four tie rods. A movable mold part plate is connected to the fixed backing plate through a drive and locking mechanism which is capable of moving the movable mold part plate into a mold position with the fixed mold part plate. A thermal force control apparatus is associated with one or more of the tie rods for changing the temperature of the tie rods and thereby causing the tie rods either to expand or contract. By such expansion or contraction, the exact force applied between the fixed and movable mold part plates can be adjusted to a desired level.