The mold hole heating process is one of the most common and oldest molding methods for plastic materials, and is one of the most commonly used methods for studying material properties. It has the characteristics of simple molding device, small equipment investment, simple mold structure, etc. It is still one of the most popular production methods in today's highly developed mechanized and automated production. However, there are some key skills in the design of the die hole heating tube.
The heating, holding and cooling of the mold and the clamping structure are an integral part of the composite mold design. The structural design directly affects the appearance and inherent quality uniformity of the product, and also affects the molding efficiency of the product.
1. Design requirements for heating tubes
Stainless steel heating tube is the heating method that must be used in almost all plastic molding die design. It can be designed as one-way wiring and two-way wiring. The material can be used with seamed pipe and seamless pipe. It features low heat loss and high thermal efficiency. The cable is simple, and can be designed as 220V or 380V according to the needs. The 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 in the mold design.
(l) The heating tube usually has a long cold end at both ends and does not function as a heating.
(2) The power design of the heating section should not exceed the limit of 10 watts/cm. For example, a 20 cm long heating tube should not exceed 200 watts of power. If the design power exceeds this limit, the surface load of the heating pipe is high, and the steel pipe is easily oxidized and corroded, causing a short circuit. Yancheng Feiyu adopts the imitation import method, and the power can be slightly larger than the ordinary heating tube.
(3) For mold design with temperature higher than 250 °C, it is difficult to use the heating tube. I used the electric heating tube to raise the temperature to 420 ° C, but this molding temperature requires high quality of the heating tube, and it is necessary to check the smoothness and short circuit of the circuit frequently. Because of this condition, the medium such as the heating tube, the terminal block, and the copper wire for connection is very easily oxidized, resulting in an open circuit. Therefore, special treatment is required for the electric transmission medium, and the conductive wires are exposed to the air as much as possible to prolong the service life of the wires.
Safety measures such as insurance and air switch are indispensable in the design. The operation should be kept clean and tidy, and the insulation should be good. During operation, the electrical fault should be checked to prevent unnecessary danger.
2. Heating pipe installation drilling
From the perspective of heat transfer, the installation of the heating tube should be as close as possible to the surface of the mold, so that the heat of the heating tube can be transferred to the mold as soon as possible. For example, the diameter of the die hole is 18 mm, and the diameter of the heating pipe is set to 17.8 mm. Actually, the heating pipe and the die do not have much contact area. The essence of heat transfer is radiation, and conduction is secondary.