A hot mold surface keeps the liquid in a long time in the form of a plastic surface, which is sufficient to form a pressure in the cavity. If the cavity is filled and before the freeze occurs, the cavity pressure can be soft plastic pressed on the metal, and the cavity surface is reproduced high. On the other hand, if in low pressure into the cavity of the plastic suspended, for however short a time, then it with a light metallic contact will cause stains, sometimes referred to as gate stain.
For each kind of plastic and plastic parts, there is a mold surface temperature limit, beyond this limit may appear one or more adverse effects (e.g., assembly can overflow edges).Higher mold temperature means less flow resistance. In many of the injection molding machine, which naturally means faster through pouring sprue and cavity, because the injection flow control valve does not correct for this change, fill faster will cause higher effective pressure in the sprue and cavity. May cause overflow. Due to more heat model are not frozen those formed on a high voltage before entering the overflow edge material plastic zone, the melt can be at the top of the bar around overflow material edges and overflow into the segmentation line clearance. This suggests the need for good injection rate control, and some modern flow control programmer did do this.
Usually, the increase of mold temperature can reduce the plastic in the cavity morning have a condensation layer, so that molten material in the cavity more easy to flow, so as to get more weight and better surface quality of the parts. At the same time, the increase of the mold temperature will increase the tension strength of the parts. Many die, especially for engineering thermoplastics, at relatively higher temperature operation, if the mold without insulation that drain to heat air and injection molding machine can easily with material ejection cylinder drain as much. So the mold and the machine plate heat insulation, if possible, will die surface heat. If you consider using hot runner mold, try to reduce the heat channel parts and cooling the heat exchange between the injection parts. Such a method can reduce energy loss and preheating time..
Temperature control necessity
(1) temperature control for the purpose of forming and as
The appearance of the forming material, the physical properties of the material, the forming cycle, etc., are significantly influenced by the temperature of the mold kernel.. General molding, the mold kernel temperature maintained in the lower, can increase the injection times more ideal, but and forming shape (mold insert structure) and finished product kinds of material forming cycle is also send Lai in it is necessary to improve the mold kernel filling temperature.
(2) to prevent stress temperature control
This is the molding material, this requirement only the cooling speed. The time of the cold is short, even though some of the hardening part is still soft, it can avoid the stress caused by the uneven shrinkage. That is, appropriate temperature control can improve the cooling stress..
(3) temperature control of the degree of crystallization of the forming material
Poly (ammonia), poly acetic acid number fat, polypropylene and other crystalline materials for crystallization of the degree of adjustment, and mechanical properties of the modified, generally need higher mold temperature.