What are the heating methods of hot runner systems?

There are several main heating methods for hot runner systems:
Electric heating
Heating coil heating
Principle: By installing a resistance heating coil on the runner plate, nozzle and other parts of the hot runner, the heating coil generates heat after power is turned on, and transfers the heat to the heated parts by heat conduction, thereby achieving heating of the hot runner system.
Features: simple structure, easy installation, low cost, can quickly increase the temperature, wide power adjustment range, and can flexibly adjust the heating power according to needs. However, the heating uniformity is relatively poor, and local overheating or overcooling is prone to occur, and the heating coil is prone to aging and damage, and needs to be replaced regularly.
Heating rod heating
Principle: Insert the heating rod into the specific heating hole of the hot runner, and the resistance wire inside the heating rod is powered on to heat up, and the surrounding runner material is heated by heat conduction.
Features: High heating efficiency, can reach a higher temperature in a shorter time, concentrated heat, and can effectively reduce heat loss. However, it has high requirements for installation position and accuracy. If it is not installed properly, it may affect the heating effect or even damage the hot runner components.
Thermal fluid heating
Hot oil heating
Principle: Use a circulating pump to make hot oil flow in the heating channel of the hot runner system. The heat carried by the hot oil is transferred to the flow channel through the channel wall to achieve uniform heating.
Features: Uniform and stable heating, high temperature control accuracy, can effectively avoid local overheating, can provide higher heat at lower pressure, and has relatively low material requirements for the hot runner system. However, it is necessary to equip a special hot oil heating device and circulation system, the equipment investment is large, the system maintenance is more complicated, and there is a risk of hot oil leakage.
Steam heating
Principle: Steam is passed into the heating chamber of the hot runner system, the steam condenses in the chamber to release heat, and the heat is transferred to the flow channel through the chamber wall for heating.
Features: Fast heating speed, high heat transfer efficiency, and can quickly increase the temperature. Steam has a wide range of sources and relatively low cost. However, the steam heating system requires good sealing, otherwise steam leakage is prone to occur. At the same time, the pressure resistance of the system is high, and the problem of condensed water freezing may occur in low temperature environments.
Other heating methods
Electromagnetic induction heating
Principle: Using the principle of electromagnetic induction, an induction coil is set around the metal parts of the hot runner. When an alternating current is passed through the coil, an alternating magnetic field will be generated inside the metal parts, and then eddy currents will be generated in the metal body. The heat generated by the eddy currents will heat up the metal parts and achieve heating of the hot runner.
Features: High heating efficiency, low energy loss, fast heating speed, precise temperature control, and good heating uniformity. At the same time, electromagnetic induction heating is relatively environmentally friendly and will not produce open flames and harmful gases. However, the equipment cost is high, and there are certain requirements for the materials and structures of the hot runner components. Metal materials with good magnetic conductivity need to be used.
Infrared heating
Principle: Infrared rays are emitted by infrared heating elements installed around the hot runner. The infrared rays are irradiated to the surface of the hot runner, absorbed by the surface and converted into heat, thereby achieving heating.
Features: Infrared heating has the advantages of non-contact heating, will not cause mechanical damage to the hot runner components, has a fast heating speed, and can quickly increase the surface temperature of the hot runner. In addition, infrared heating can be locally heated as needed, with high flexibility. However, infrared heating has limited penetration ability and mainly acts on the surface of the hot runner. The internal heating effect is relatively poor, and the heating effect is greatly affected by distance and angle.