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Influence Of Mould Temperature On Injection Molding
Dec 08, 2018

A hot mold surface keeps the plastic surface liquid long enough to create pressure in the mold cavity. If the cavity is filled and the soft plastic is pressed against the metal before the frozen epidermis hardens, the surface of the cavity is duplicated higher. On the other hand, if the plastic entering the mold cavity at low pressure is suspended, no matter how short the time, the slight contact with the metal will cause stains, sometimes called gate stains.

For each type of plastic and plastic parts, there is a limit of mold surface temperature beyond which one or more adverse effects may occur (e.g., components may overflow rough edges). Higher mold temperature means less flow resistance. On many injection molding machines this naturally means faster flow through the gates, gates and cavities as the injection flow control valves used do not correct this change and faster filling causes higher effective pressure in the runner and cavities.

May cause overflows of rough edges. Since the hotter model does not freeze the plastic that enters the overflow edge area before high pressure is formed, the melt can overflow the rough edges around the ejector rod and spill into the parting line gap. This indicates the need for good injection rate control, and some modern flow control programmers can do just that.

Generally, the rise in mold temperature will reduce the plastic in the cavity morning condensation layer, so that the molten material in the cavity more easily flow, so as to obtain greater parts weight and better surface quality. At the same time, the temperature of the mold will increase the tension strength of the parts. Many molds, especially engineering thermoplastics, operate at relatively high temperatures, and if the molds are not insulated, the heat lost to the air and the injection molding machine can easily be as much lost as the jet cylinder.

So the mold and the plate heat insulation, if possible, the surface of the mold heat insulation. If a hot runner mold is considered, try to reduce the heat exchange between the hot runner portion and the cooled injection parts. This method can reduce energy loss and heating time

Necessity of temperature control

(1) purpose and action of temperature control on formability

The appearance of forming products, physical properties of materials and forming cycle are significantly affected by the temperature of mold kernel. In general, it is desirable to keep the temperature of the molds at a low level to increase the injection frequency. However, the forming cycle related to the shape of the molds (the structure of the molds) and the type of finished materials also depends on the need to increase the temperature of the filling of the molds.

(2) temperature control is conducted to prevent stress

This is the material problem of forming products. The only requirement is ※ cooling speed. Short cooling time, even if part of the hardening and part of the soft occasions, still can avoid uneven shrinkage caused by stress. That is, proper temperature control can improve the cooling stress properties.

(3) temperature control of crystallization degree adjustment of forming materials

Polythiamine (nylon), polyacetic acid lipid, polypropylene and other crystalline materials to adjust the degree of crystallization, and improve the mechanical properties, generally requires a higher temperature mold kernel.