Mold temperature is not just a setpoint on a machine screen—it is the decisive factor in plastic part appearance and dimensional stability. For ABS, the recommended mold surface temperature range is 40–80°C; for PC, it jumps to 80–120°C. Drop below these windows, and you will see short shots, flow marks, or worse, internal voids in thick-wall sections. Many experienced operators still rely solely on the temperature readout from the injection unit, overlooking the actual temperature difference between the inlet and outlet of the mold temperature controller. That delta can be 10–15°C in production, which directly leads to uneven cooling and hidden shrinkage. A practical fix is to embed thermocouples on the moving half of the mold, directly measuring the cavity surface temperature rather than trusting the oil temperature setpoint. This is especially critical for molds with complex cooling channels or deep ribs, where the thermal gradient across the steel is significant. In my experience, a simple K-type thermocouple placed 2–3 mm behind the cavity surface can reduce scrap rates by up to 30% on high-gloss PC parts. It also helps in fine-tuning the cooling time, because you are now reacting to actual steel temperature, not a lagging hydraulic oil reading. For mold designers, this means planning for sensor placement early—drilling holes for thermocouples during the mold build, not retrofitting later. Also, consider using multi-zone temperature control for large molds, where the core and cavity may require different setpoints to balance cooling. The data from these sensors also feeds into process validation and can be logged for quality audits. If you are sourcing molds or upgrading your temperature control systems, visit MoldWorld (www.moldw.com) for reliable suppliers and practical tooling insights.