Working principle and characteristics of injection molding machine heating ring

Resistive Heating Coils

Currently, most injection molding machines on the market still use resistive heating coils. Resistive heating coils generate heat based on the resistive heating effect of current. Specifically, when current flows through a conductor, the conductor's resistance hinders the current flow. The current then overcomes this resistance by performing work, converting electrical energy into heat. This heat is then transferred via contact conduction. Therefore, the inner wall of the heating coil must be in close and reliable contact with the outer wall of the barrel to transfer the heat.

Resistive heating coils offer advantages such as low price, simple structure, and a low failure rate. However, they also have significant disadvantages. Because they utilize contact heat transfer, the vibrations of high-speed injection molding machines can affect the heating efficiency of conventional heating coils, resulting in increased energy consumption.

Electromagnetic Induction Heating Coils

Electromagnetic induction heating coils operate based on the principle of eddy current heating induced by a magnetic field. The input 50Hz/220V AC power is converted to 315V DC through a rectifier circuit. This is then converted to a high-frequency current with a frequency of 20-35kHz by a control circuit. When this high-frequency current passes through the coil, it generates a rapidly fluctuating magnetic field. When the magnetic lines of force within this field pass through metal, they generate countless small eddy currents within the metal, causing the metal to heat rapidly.

Electromagnetic induction technology began to be used in heating coils for plastic molding machines in the early 2000s. After nearly a decade of development, electromagnetic induction technology has gradually become synonymous with energy-saving heating coils. This fundamental change occurred with the emergence of infrared energy-saving heating coils. Over the past century, improvements in heating coils have gradually kept pace with global economic development.