Control of injection molding temperature of injection molding machine

Temperature measurement and control are very important in injection molding. Although these measurements are relatively simple, most injection molding machines do not have enough temperature sampling points or circuits. So how is the temperature of the injection molding machine controlled? And what temperature needs to be controlled during the injection molding process? This article will give you a detailed understanding of the principle of temperature control of the injection molding machine and some conventional settings.

The principle of temperature control of injection molding machine

On most injection molding machines, temperature is sensed by thermocouples. Generally, a temperature measuring thermocouple is used as a temperature measuring element, and a temperature measuring millivoltmeter is used as a temperature control device. On the control instrument, set the required temperature, and the display of the sensor will be the same as the temperature generated at the set point Compare. A thermocouple is basically composed of two different wire ends connected together. If one end is hotter than the other, a tiny electrical signal will be generated; the more heated, the stronger the signal. In this simplest system, when the temperature reaches the set point, it will turn off, and the power will turn on again when the temperature drops.

Through the above principles, the on-off of the current of the barrel and the mold electric heating ring can be directed, and the temperature of each section of the barrel and the mold temperature can be selectively fixed. The barrel electric heating ring is generally divided into two stages, three stages or four stages of control. The ammeter on the electrical cabinet respectively shows the size of the current of each section of the electric heating coil. The reading of the ammeter is relatively fixed. If the reading of the ammeter is found to be low for a long time during operation, it may be that the heating coil has malfunctioned, or the wire is in poor contact, or the heating wire is oxidized and thinned, or a certain heating ring is burned out. Both will increase the resistance of the resistors connected in parallel with the circuit and decrease the current.

When the ammeter has a certain reading, you can simply use a plastic strip to wipe the outer wall of the electric heating ring one by one, and see whether the material is melted or not to judge whether a certain electric heating ring is energized or burned out.

Melting temperature and shooting cylinder temperature

Melting temperature is also very important, and the temperature of the injection cylinder used is only a guideline. Melt temperature can be measured at the nozzle or air jet method. The temperature setting of the injection cylinder depends on the melt temperature, screw speed, back pressure, injection volume and injection cycle.

If you do not have experience in processing a specific grade of plastic, please start with the lowest setting. In order to facilitate control, the shooting cylinder is divided into zones, but not all are set to the same temperature. If the operation time is long or the operation is at high temperature, please set the temperature of the first zone to a lower value, which will prevent the plastic from melting and shunting prematurely. Before injection, make sure that the hydraulic oil, hopper closure, mold, and injection cylinder are all at the correct temperature.