In the process of blowing mold processing, the factors that will affect the product mainly include blowing pressure, blowing speed, blowing ratio and blowing mold temperature.
Blow molding mold processing
1. In the process of blowing, the compressed air has two functions: one is to use the pressure of the compressed air to make the semi-molten tube billet blow and cling to the mold cavity wall to form the desired shape; Second, it plays a cooling role in Dongguan blow molding products. Air pressure depends on the type of plastic and the billet temperature, generally controlled in 0.2 ~ 1.0mpa. For plastics with low melt viscosity and easy deformation (such as PA and HDPE), take a lower value; For plastics with higher melt viscosity (such as PC), higher values are taken, and so is the wall thickness of the billet. Blowing pressure is also related to the volume of products, large volume products should use higher blowing pressure, small volume products should use smaller blowing pressure. The most suitable blowing pressure should be able to make the appearance and pattern of the product clear after forming.
2, blowing speed in order to shorten the blowing time, so that it is conducive to the product to obtain a more uniform thickness and better appearance, the requirements of low flow speed into the large flow of air, to ensure that the billet in the mold cavity can be uniform, fast expansion, shorten the cooling time in the mold cavity, and is conducive to improve the performance of the product. The low airflow velocity can also avoid a kind of Venduri effect in the billet and the formation of local vacuum, so that the billet deflated phenomenon. This can be ensured by the use of a larger blowing pipe.
3, blowing ratio when the size and quality of the billet is certain, the larger the size of the product, the larger the billet blowing ratio, but the thinner the thickness of the product. Usually according to the type of plastic, nature, shape and size of the product, and the size of the billet to determine the size of the blowing ratio. With the increase of blowing ratio, the thickness of the product becomes thinner, and the strength and stiffness decrease. It also becomes difficult to form. Generally, the blowing ratio is controlled in l 
2-4) or so.
4. The temperature of blow molding mold has a great influence on the quality of products (especially the appearance quality). Usually the mold temperature distribution should be uniform, as far as possible to make the product uniform cooling. The mold temperature is related to the type of plastic, the thickness and size of products. For different kinds of plastic, there are a few plastic (PC blow molding bottle) mold temperature should be controlled in sections.
Production practice has proved that the mold temperature is too low, then the elongation of the plastic at the clip is reduced, it is not easy to blow, so that the product is thickened in this part, and it is difficult to form, and the contour and pattern of the product surface are not clear; The mold temperature is too high, the cooling time is prolonged, the production cycle is increased, and the productivity is decreased. At this time, if the cooling is not enough, it will also cause the product demoulding deformation, the shrinkage rate is increased, and the surface luster is worse. Generally for plastics with larger molecular chain rigidity, the mold temperature should be higher; For plastics with larger flexible molecular chains, the mold temperature should be reduced.
Hollow blow molding products in the mold cooling time is long, the purpose is to ensure that the product fully cooled, demoulding without deformation. The cooling time generally depends on the thickness, size and shape of the plastic, as well as the type of plastic. The thicker the wall, the longer the cooling time. The cooling time of 61PE products with large specific heat capacity is longer than that of PP products with small specific heat capacity of the same wall thickness.
5. Molding cycle Blow molding production cycle includes extrusion billet, die closing, cut billet, blowing, deflating, opening mold, taking out products and other processes. The principle of this cycle selection is to shorten as far as possible under the premise of ensuring that the product can be shaped without deformation, so as to improve production efficiency.
Post time: Aug-31-2022