Analysis on Temperature Control Methods and Influencing Factors of Injection Molding Mould

Many molds, especially thermoplastics for molding engineering, operate at relatively high temperatures, such as 80 degrees Celsius or 176 degrees Fahrenheit. If the mold is not insulated, the heat lost to the air and the Injection Molding Machine can easily be as much as the injection cylinder.

Therefore, the mold should be insulated with a skeleton board, and if possible, the surface of the mold should be insulated. If you consider using a hot runner mold, try to reduce the heat exchange between the hot runner portion and the cooled molded part. This method reduces energy loss and warm-up time.

What are the effects of mold temperature on injection molding?

Mold temperature is the most important variable in injection molding. No matter what kind of plastic is injected, it is necessary to ensure that the basic wetness of the mold surface is formed. A hot mold surface keeps the plastic surface liquid for a long time, enough to build up pressure in the cavity.

If the cavity is filled and the cavity pressure presses the soft plastic against the metal before the frozen skin hardens, then the reproduction of the cavity surface is high. On the other hand, if the plastic entering the cavity at low pressure is suspended, no matter how short, then its slight contact with the metal will cause a stain, sometimes referred to as a gate stain.

For each type of plastic and plastic part, there is a limit of mold surface temperature beyond which one or more adverse effects may occur (for example, components may spill out of burrs). Higher mold temperatures mean less flow resistance.

On many injection molding machines, this naturally means faster flow through the gate and cavity, because the injection molding flow control valve used does not correct this change, and faster filling causes a higher effective pressure in the runner and cavity, which may lead to overflowing raw edges.

Since the hotter mold cavity does not freeze the plastic that enters the overflow area before the high pressure builds up, the melt can overflow (the raw edge) around the ejector rod and spill into the gap between the dividing lines. This indicates the need for good injection rate control, and some modern flow control programmers can indeed do this.

Generally, the increase in mold temperature will reduce the condensation layer of the plastic in the cavity, making it easier for the molten material to flow in the cavity, thereby obtaining greater part weight and better surface quality. At the same time, the increase in mold temperature will also increase the tensile strength of the parts.