The necessity of temperature regulation of injection mold

The temperature of injection mold has a great influence on the filling flow, curing and setting of plastic melt, production efficiency and the shape and dimensional accuracy of plastic parts.

Each kind of plastic injection molding has a reasonable mold temperature area, which makes the melt flow well and easy to fill the mold cavity. After demoulding, the plastic parts have small shrinkage and warpage deformation, stable size, and high mechanical properties and surface quality. In order to control the temperature of the mold, the temperature regulation system must be designed. Generally, the mold cooling or heating method is used. If necessary, both methods are used. There are many cooling devices in the mold of mobile phone shell.

1. Necessity of temperature regulation

Mold temperature has a great influence on the forming quality and efficiency of rubber parts. In the mold with higher temperature, the melt fluidity is better, which is conducive to the filling cavity of the rubber, obtaining the surface appearance of the high quality glue piece, but it will make the curing time of the rubber become longer and easy to deform when ejecting.

For crystalline rubber, it is more conducive to the crystallization process and avoid the change of rubber part size during storage and use; In the mold with low temperature, the molten rubber is difficult to fill the cavity, resulting in increased internal stress, dull surface, crazing, fusion marks and other defects.

Different rubber materials have different processing technology, and the surface requirements and structures of various rubber parts are different. In order to produce rubber parts that meet the quality requirements in an effective time, the mold is required to maintain a certain temperature. The more stable the mold temperature is, the more consistent the requirements of the produced rubber parts in terms of size, shape, appearance quality, etc.

Therefore, in addition to the factors of mold manufacturing, mold temperature is an important factor to control the quality of rubber parts. The control method of mold temperature should be fully considered in mold design.

2. Principle of mold temperature control

In order to ensure the production of rubber parts with high appearance quality requirements, stable size and small deformation in an effective time, the basic principles of mold temperature control should be clearly understood in the design.

① Different compounds require different mold temperatures.

② The molds with different surface quality and different structure require different mold temperature, which requires pertinence in the design of temperature control system.

③ The temperature of the front mold is higher than that of the rear mold. Generally, the temperature difference is about 2 ~ 3 ℃.

④ The temperature of the front die with spark pattern is higher than that required by the general smooth surface. When the front die needs hot water or hot oil, the general temperature difference is about 40 ℃.

⑤ When the actual mold temperature cannot reach the required mold temperature, the mold shall be heated. Therefore, during the mold design, full consideration shall be given to whether the heat brought into the mold by the rubber can meet the mold temperature requirements.

⑥ The heat brought into the mold by the rubber is consumed by heat radiation and heat conduction, and most of the heat needs to be brought out of the mold by the circulating heat transfer medium.

⑦ The mold temperature shall be balanced without local overheating and supercooling.