The temperature of the injection mold has great influence on the filling flow of the plastic melt, the curing setting, the production efficiency, and the shape and dimensional accuracy of the plastic parts. Each type of plastic injection molding has a reasonable mold temperature area, so that the melt fluid is easy to fill the cavity, plastic parts after the mold shrinkage and warping deformation, dimensional stability, mechanical properties and surface quality is also high. In order to control the temperature of the mold, a temperature adjustment system must be designed. Generally, the method of cooling or heating the mold is used. When necessary, both types are used, and more cooling devices are used in the mold of the mobile phone housing.
1. The necessity of temperature adjustment The mold temperature has a great influence on the molding quality and forming efficiency of the plastic parts. In the mold with higher temperature, the fluidity of the molten rubber is better, which is favorable for filling the cavity with the rubber material and obtaining a high-quality appearance surface of the plastic piece. However, the curing time of the rubber material is prolonged, and the plastic material is easily deformed when ejected. For crystalline compounds, it is more conducive to the crystallization process, to avoid changes in the size of the plastic parts during storage and use; in lower temperature molds, the molten rubber is difficult to fill the cavity, resulting in increased internal stress, matt surface , resulting in silver lines, weld marks and other defects.
Different rubber materials have different processing properties, and the surface requirements and structures of various plastic parts are different. In order to produce plastic parts that meet quality requirements in the most efficient time, this requires the molds to maintain a certain temperature. The more stable, the more consistent the requirements of the plastic parts produced in terms of size, shape, and appearance quality of the plastic parts. Therefore, in addition to the factors of mold manufacturing, the mold temperature is an important factor in controlling the quality of the plastic parts, mold design should fully consider the mold temperature control method.2. The principle of mold temperature control In order to ensure that the plastic parts with high appearance quality, dimensional stability, and small deformation are produced in the most effective time, the basic principles of mold temperature control should be clearly understood during design.
different plastic materials require different mold temperatures.
Different surface quality, different structure of the mold requires different mold temperature, which requires the design of the temperature control system is targeted.
The temperature of the front mold is higher than the temperature of the rear mold. Under normal circumstances, the temperature difference is about 2~3o.
The temperature of the front mold required by the fire pattern is higher than the temperature of the front mold required by the general smooth surface. When the current mold must be hot water or hot oil, the general temperature difference is about 40°.
When the actual mold temperature can not reach the required mold temperature, the mold should be heated. Therefore, the mold design should fully consider whether the heat brought by the rubber into the mold can meet the mold temperature requirements.
In addition to the heat consumed by heat radiation and heat conduction, the majority of the heat brought into the mold by the rubber material needs to be brought out of the mold by the circulating heat transfer medium.
The mold temperature should be balanced and there should be no local overheating or cold.