A temperature control unit is a machine dedicated to regulating the temperature of the heat transfer fluid (such as water, oil, or glycol) used to maintain precise thermal conditions in the machine or downstream process.
Temperature control units are key components in the plastics processing industry for applications such as injection molding, extrusion, thermoforming, and blow molding, where the thermal stability of the fluid ensures dimensional uniformity, surface finish, and optimal cycle times.
Requirements:
Requirement:
Thermoregulation
Temperature control units are used to maintain the temperature of molds, tools, or circuits in plastic transformation processes within well-defined limits, using water or diathermic oil as the heat transfer fluid.
Thermal stability is essential to ensure repeatable process conditions, reduce deformation, and optimize cycle times. The system must be able to heat the fluid quickly and compensate for heat loss, reacting dynamically to load variations.
Solution:
Gefran technology for the thermal control of extruders is based on static relays, PID controllers and thermocouples:
- Each heating element is managed in a closed loop via PID control, integrated into the PLC or entrusted to dedicated controllers such as the 1850, which allows the temperature to be maintained within ±0.5°C of the setpoint
- The compact GRP-H solid state relay with integrated heat sink ensures precise current control up to 120 A. IO-Link communication also reduces the number of I/O cards required, thanks to the integrated management of commands, alarms, and current consumption
The solution is scalable and compatible with PIDs integrated in PLCs or remote modules. Recipe storage and historical trend functions support rapid production changes and continuous quality improvement.
Requirement:
Heat transfer fluid pressure control
Inside a temperature control unit, the heat transfer fluid is circulated in a closed circuit to molds, tools, or process equipment.
Circuit pressure control is essential to verify the correct operation of the pump, the absence of obstructions, leaks, or cavitation, and to ensure uniform fluid distribution. Abnormal pressure variations can indicate incorrect operating conditions and compromise the effectiveness of temperature control, as well as posing a potential risk to the machine and the process.
Solution:
KS pressure sensors are ideal for monitoring pressure in temperature control units heat transfer fluid circuits, thanks to their compact design and reliable performance over time. Continuous pressure measurement allows control thresholds to be associated with machine logic, improving system protection and operational stability.
Main features:
- Wide measuring range: from 4 to 1000 bar, suitable for various hydraulic and thermal circuits
- Thick Film technology: stainless steel membrane for high strength and durability
- Integrated snubber: mechanical structure integrated into the sensor to prevent water hammer from damaging the instrument
- Safety and diagnostic functions: SIL2 certification and IO-Link version (KS-I) for advanced circuit monitoring
Thanks to these features, KS sensors effectively complement temperature control units control, ensuring reliability, safety, and process continuity.
Operating principle:
The temperature control unit maintains the required temperature by circulating a heat transfer fluid through a closed circuit that feeds the main machine or process circuits. Inside, the temperature control units integrates a circulation pump, a heating module (usually consisting of immersed or band electric heaters), and an electronic control system that constantly compares the value measured by the temperature sensors with the desired setpoint.
When the fluid temperature falls below the set value, the controller activates the heating elements, increasing the energy supplied to the fluid; when the temperature exceeds the setpoint, the system can reduce the heating power or, in advanced units, activate secondary cooling modules or heat exchangers. Closed-loop control based on PID logic allows the system to react to changes in thermal load, maintaining the temperature within tight tolerances and ensuring that the energy supply is proportionate to the process requirements.
Requirements and technology:
In temperature control units, process quality and operational reliability depend on the coordinated control of the temperature and pressure of the heat transfer fluid that feeds molds, tools, or process utilities. The thermal stability of the fluid, whether water or diathermic oil, is essential to ensure repeatable process conditions, reduce product deformation, and optimize cycle times. The system must be able to react quickly to changes in thermal load, compensating for losses and maintaining the setpoint within tight tolerances.
At the same time, monitoring the pressure in the circuit is key to ensuring the correct operation of the circulation pump, uniform fluid distribution, and the absence of critical conditions such as leaks, obstructions, or cavitation. Abnormal pressure variations can compromisethe effectiveness of temperature control and reducethe overall reliability of the temperature control units, as well as generate potential risks for the machine and the process.
The integration of PID control, solid-state relays for resistance management, and reliable pressure sensors allows for the creation of stable, scalable control systems that can be easily integrated with PLCs and automation systems.
Gefran meets these requirements by providing complete solutions for thermal control and monitoring of temperature control units circuits, designed to ensure precision, safety, and process continuity.