Basic production methods and problems of plastic hollow products Blow molding is the basic method of producing plastic hollow products, among which extrusion blow molding is a commonly used production method. At present, plastic bottles, cans, boxes and other hollow containers and hollow industrial parts are mostly produced by extrusion blow molding. The world's first plastic extrusion blow molding machine came out in 1939, then the blowing equipment is very simple, only intermittent production, with the development of science and technology, plastic blowing equipment mechanical structure, function and automation control level has been greatly developed. At the end of 60's, there is a simple programmable adjustment of the billet controller, improve the processing of hollow forming, product performance has been greatly improved. 
After entering the 1990s, with the rapid development of computer technology, blow molding began to enter the era of computer control, improve the level of production automation. The large plastic hollow products industry began to develop in the 1930s. After a number of development periods, gradually into the rapid development of large plastic hollow products. Large plastic hollow products are widely used in sports and sports equipment, auto parts, commercial and office supplies, household appliances, medical supplies, equipment and instrument packaging, tool bags and many other industries. The development of blow molding technology has promoted the development and progress of large plastic hollow products, and the automatic control hollow blow molding machine has been more research and development. The rapid development of blow molding products and blow molding equipment has also promoted the research and application of various plastic polymers, plastic alloys and plastic formulation technology, which has made rapid progress and development. 
Compared with small and medium-sized industrial plastic blow molding technology, the blow molding technology of large industrial plastic blow molding parts is developed in the past 20 years. In the past 20 years, large hollow products have been widely used in automobile parts, petrochemical industry, freight logistics, chemical products, railway transportation, tourism, aquaculture, tourism and many other industries, especially in recent years to the rapid development. With the increase of product types and output of large industrial plastic blow molding parts, large plastic hollow molding machines and plastic raw materials have been rapidly developed. Together, they have turned many products from imagination into reality. Blow molding is a basic method used to produce plastic hollow products, among which extrusion blow molding is one of the commonly used production methods. The production process of large hollow products is as follows: the tubular plastic billet obtained by extrusion of thermoplastic resin is placed in a split die while hot, and compressed air is poured into the billet immediately after the mold is closed, so that the plastic billet is blown and close to the inner wall of the mold. After cooling and demoulding, various hollow products are obtained. 
With the development of blow molding industry and the continuous improvement of the quality requirements of plastic container products, the main problems existing in the automatic hollow blow molding machine on the market at present are: 1. Low production efficiency and high labor intensity; 2. When the automatic work is put into operation, the coordination and adjustment of the automatic double station are tedious. Once abnormal conditions occur in the working process, the machine needs to be stopped for processing and then started, and the material length of the left and right rack will be inconsistent and cannot be matched; 3. The time control of each action process cannot be adjusted at will; 4. Model billet wall thickness mainly depends on manual adjustment; 5. The extrusion screw motor is controlled by electromagnetic speed regulation, and often the extrusion speed is adjusted to the upper limit and cannot keep up with the blown working cycle, thus reducing the production efficiency.
In order to overcome the above shortcomings, further shorten the forming cycle to improve productivity. In recent years, the design of blow molding control system has become the focus of attention of blow molding manufacturers. On the basis of automatic hollow blow molding machine, through the analysis of extrusion hollow blow molding process, the blow molding control system is designed and studied, in order to solve the problems existing in the current market of automatic double-station blow molding machine, and truly realize the requirements of "high reliability, high adaptability". | 
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