An injection molding apparatus, comprising: a mold comprising mold cavities; a ram arranged to form a shot of molten thermoplastic material; a system nozzle arranged to inject a shot of molten thermoplastic material through a hot runner manifold (74, 77); a plurality of hot runner nozzles (80, 90) adapted to receive molten thermoplastic material from the hot runner manifold (74, 77) and inject the molten thermoplastic material into a plurality of mold cavities, each mold cavity connected to one hot runner nozzle (80, 90); a plurality of temperature zones, each temperature zone associated with one of the plurality of mold cavities and including at least a portion of the hot runner manifold (74, 77), the associated mold cavity, and the hot runner nozzle (74, 77) connected to the associated mold cavity; a plurality of heaters (72, 75, 78, 81), each heater (72, 75, 78, 81) connected to a hot runner controller (91, 300), each temperature zone including at least one heater; characterized by a plurality of strain gauges (52, 83, 100), each strain gauge (52, 83, 100) in communication with the hot runner controller (91, 300) and each temperature zone provided with at least one strain gauge (52, 83, 100), wherein the hot runner control comprises a set of instructions that are stored on a non-transitory machine-readable medium to create a target strain profile, to detect deviations from the target strain profile in any temperature zone based on the strain readings provided by the strain gauges (52, 83, 100) in each temperature zone, and to instruct correction of deviations from the target strain profile in the deviating temperature zone by adjusting the heat produced by the at least one heater (72, 75, 78, 81) in the deviating temperature zone, wherein the at least one strain gauge (52, 83, 100) provided for each temperature zone is located at least one of: in the portion of the hot runner manifold (74, 77) associated with the temperature zone and in the hot runner nozzle (80, 90) connected to the mold cavity associated with the temperature zone. a mold comprising mold cavities; a ram arranged to form a shot of molten thermoplastic material; a system nozzle arranged to inject a shot of molten thermoplastic material through a hot runner manifold (74, 77); a plurality of hot runner nozzles (80, 90) adapted to receive molten thermoplastic material from the hot runner manifold (74, 77) and inject the molten thermoplastic material into a plurality of mold cavities, each mold cavity connected to one hot runner nozzle (80, 90); a plurality of temperature zones, each temperature zone associated with one of the plurality of mold cavities and including at least a portion of the hot runner manifold (74, 77), the associated mold cavity, and the hot runner nozzle (74, 77) connected to the associated mold cavity; a plurality of heaters (72, 75, 78, 81), each heater (72, 75, 78, 81) connected to a hot runner controller (91, 300), each temperature zone including at least one heater; characterized by a plurality of strain gauges (52, 83, 100), each strain gauge (52, 83, 100) in communication with the hot runner controller (91, 300) and each temperature zone provided with at least one strain gauge (52, 83, 100), wherein the hot runner control comprises a set of instructions that are stored on a non-transitory machine-readable medium to create a target strain profile, to detect deviations from the target strain profile in any temperature zone based on the strain readings provided by the strain gauges (52, 83, 100) in each temperature zone, and to instruct correction of deviations from the target strain profile in the deviating temperature zone by adjusting the heat produced by the at least one heater (72, 75, 78, 81) in the deviating temperature zone, wherein the at least one strain gauge (52, 83, 100) provided for each temperature zone is located at least one of: in the portion of the hot runner manifold (74, 77) associated with the temperature zone and in the hot runner nozzle (80, 90) connected to the mold cavity associated with the temperature zone.