Thermal insulation method of injection mold

Thermal insulation method of injection mold

Mold temperature is the most important variable in injection molding - no matter what kind of plastic is injected, it must ensure that the mold surface is basically wet. A hot mold surface keeps the plastic surface liquid for a long time, enough to form pressure in the mold cavity. If the cavity is filled and the cavity pressure can press the soft plastic against the metal before the frozen skin hardens, the replication 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 the time, its slight contact with the metal will cause stains, sometimes called gate stains.
For each kind of plastic and plastic parts, there is a limit of mold surface temperature, beyond which one or more adverse effects may occur (for example, the component can overflow the burr). Higher die temperature means less flow resistance.
On many injection molding machines, this naturally means faster flow through the gate and cavity, because the injection flow control valve used does not correct this change, and faster filling will cause higher effective pressure in the gate and cavity.
It may cause material overflow and burr. Since the hotter model does not freeze the plastic that enters the overflow edge area before the high pressure is formed, the molten material can overflow the burr around the ejector rod and overflow into the gap of the dividing line. This shows that good injection rate control is needed, and some modern flow control programmers can do this.
Generally, the increase of mold temperature will reduce the condensation layer of plastic in the mold cavity, making the molten material easier to flow in the mold cavity, so as to obtain greater part weight and better surface quality. At the same time, the increase of die temperature will also increase the tensile strength of parts.
Heat preservation method of mould
Many molds, especially engineering thermoplastics, 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 injection molding machine can easily be as much as that lost by the injection cylinder.
Therefore, a framework plate of the mold shall be insulated, and if possible, the surface of the mold shall be insulated. If a hot runner mold is considered, try to reduce the heat exchange between the hot runner part and the cooled injection molded part. This method can reduce energy loss and preheating time.