1. Blowing pressure

There are two functions of compressed air in blow molding: blowing and cooling. Low pressure should be used for low viscosity, small volume or thick wall parts; high pressure should be used for high viscosity, large volume or thin wall parts.

2. Blowing speed

In order to shorten the blowing time, so as to obtain a more uniform thickness and a better surface of the product, the inflation speed should be as high as possible, but if the inflation speed is too fast, it is easy to produce the following phenomena: (1) a vacuum is created at the air inlet, which makes the blank of this part sink in, and when the blank is fully inflated, the concave part will form a diaphragm; (2) the blank of the die part may be broken by the extremely fast air flow.

3. Blow up ratio

It is usually controlled at 2-4 times. If the blowing ratio is too large, the shape stability of the product is poor, and if it is too small, it is easy to cause uneven wall thickness.

4. Mold temperature and cooling time

If the mold temperature is too low, the elongation of the plastic at the clamp will be reduced, and it is not easy to blow, and the part will be thickened, and it is difficult to form; if the mold temperature is too high, the cooling time will be prolonged, and the production cycle will be long. If the cooling time is too short, the cooling is not sufficient, it will easily lead to the deformation, shrinkage increase, and the surface will be dull

5. Molding cycle

It includes the process of extruding, cutting, closing, blowing, cooling, venting, opening and taking out the product. The selection principle of forming cycle is to shorten as much as possible on the premise of ensuring the product can be shaped.