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Injection mold heating, insulation and cooling analysis

The heating, insulation and cooling of the mold and the clamping structure are an integral part of the design of the composite mold. The structural design directly affects the appearance and inherent quality uniformity of the product, and also affects the forming efficiency of the product.

Molding process is one of the most common and oldest molding methods for plastic materials, and it is one of the most commonly used techniques for studying material properties. It has the advantages of simple molding device, small equipment investment and simple mold structure. It is still one of the most popular production methods in today's highly developed mechanized and automated production. However, for the mold design of compression molding, few sums up the key skills in mold design. This article will explain heating, insulation and cooling design.

Heat pipe design requirements

Steel heating is a heating method that must be adopted for almost all plastic molding die designs. It can be designed as one-way wiring, two-way wiring, and other forms. The material can be used for seam pipe, seamless pipe, stainless steel pipe, etc. It is characterized by heat loss. Small, high thermal efficiency, simple line, can be designed as 220V or 380V, wiring is flexible and diverse. However, due to the limitations of its materials and processing technology, it is necessary to pay attention to its characteristics when designing molds.

1.Heating tubes usually have longer cold ends at both ends and do not function as heating

2.The power design of the heating section should not exceed the limit of 10 watts/cm. For a 30 cm long heating tube, the power should not exceed 300 watts. If the designed power exceeds this limit, the surface load of the heating tube is high, and the steel tube is easily oxidized and corroded, resulting in a short circuit

3.For mold designs with temperatures above 250°C, the use of heated tubes can be difficult. I once used a heating tube to heat up to 420°C, but this molding temperature has a high quality requirement for the heating tube and it is necessary to check the circuit smoothness and short circuit frequently. Because under such conditions, the heating pipes, terminal blocks, copper wires for connection and steel sheets are very apt to be oxidized, resulting in disconnection. Therefore, special treatment is required for the electric transmission medium, so as to avoid exposing the conductive wires to the air and extend the service life of the wires

The soldering iron core is also usually used as a type of mold heating tube. It features high power per unit length (usually 10 mm in diameter and 8 cm in length can achieve a power output of 150 watts). It is durable, safe, and hard to break down. It can be buried by drilling a blind hole. The disadvantage is that it is difficult to customize the design. It is fragile and broken when it is replaced. The circuit design is indispensable for insurance, air switch and other insurance measures. The operation site should be kept clean and tidy, well insulated, and diligent in checking electrical faults during operation to prevent unnecessary dangers.

Heating pipe installation drilling

From the perspective of heat transfer, the installation of the heating pipe should be as close as possible to the surface of the mold to facilitate the heat transfer to the mold as quickly as possible. In fact, there is not much contact area between the heating tube and the mold. The heat transfer is essentially radiation and conduction is secondary. Therefore, most of the surface of the heating tube used for mold installation is coated with an infrared radiation-enhanced coating, and the design power (10 watts/cm) is also used to increase the service life of the heating tube.

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