Extrusion-blow molding process in hollow blow molding technology
Extrusion _ blow molding is the use of an extruder to extrude a tubular parison, and then the parison is fed into the blow mold while hot, and the compressed air is blown through it to make it closely adhere to the wall surface of the mold cavity to obtain the mold cavity shape. , In the case of maintaining a certain pressure, after cooling stereotypes, open mold release and get the blow molding products. Extrusion blow molding has the advantages of high billet production efficiency, relatively uniform parison temperature, reduced product breakdown, higher strength, the ability to produce large containers, less equipment investment, and less welding seams, allowing for the shape, size and wall thickness of the container. The advantages such as larger range, therefore, still have an advantage in the current production of hollow products.
The entire process of extrusion blow molding generally includes the following five steps:
1 The polymer is melted by an extruder and the melt is formed into a tubular parison by a handpiece;
When the parison reaches a predetermined length, the blow mold is closed, the parison is clamped between the mold halves, and cut off and moved to another station;
3 Inject the compressed air into the parison, inflate the parison, and mold it closely to the mold cavity;
5 mold, remove the molded product.
According to different ways of discharging, extrusion blow molding can be divided into two categories: direct extrusion blow molding and extrusion storage, extrusion molding and blow molding. The advantages of direct extrusion blow molding are: simple equipment, low investment, easy operation, suitable for blow molding of various plastics. However, the product wall thickness uniformity is poor. The process of extruding a stock material and extruding a blow-molding process is characterized in that a large container can be produced with a small apparatus; the desired parison length can be obtained within a short period of time and the uniformity of wall thickness of the product can be ensured. The disadvantages are: the equipment is complex, the design and maintenance of the hydraulic system is difficult, and the investment is large.
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