The vacuum forming process was known as early as the beginning of the 20th century, but its application in industrial production was only after the 1940s, but it was only
developed in the 1960s. In the past 20 years, it has developed into one of the most important methods of processing packaging materials. The rapid development of this technology is due to the continuous innovation of vacuum forming processes and equipment, as well as the development of new sheets with forming properties; it is also determined by the development of the packaging industry and the characteristics of the vacuum forming packaging itself.
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Vacuum forming is one of the most common forming methods for plastic packaging containers. It is an overmolding technology that uses thermoplastic sheets as a molding object. In foreign countries, vacuum forming is an old molding process. Due to continuous development and changes, it has been highly automated and mechanized, and has achieved no waste material, and 100% of raw and auxiliary materials have become products. Forming system engineering for full-line production.Metal Shield
Vacuum blistering differs in the following conditions:
·Remolding temperature required to heat the molding material to a high elastic state
·Forming molds commonly used in plastic forming
· Cool the product to a cooling temperature where it does not change in size
·The part is demoulded after the size is stable
In most cases, post-treatment of blister molding is also necessary, such as:
· Trimming, welding, bonding, heat sealing, coating, metallization, flocking, printing
Vacuum blistering has now become a commonly accepted term in the field of processing: "vacuumforming". And "pressureforming" refers to some special processes that use air pressure processing. "Thermoforming" is a general term for various thermoplastic moldings, including vacuum and pressure, or hybrid molding.
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First, the advantages and disadvantages of vacuum plastic molding
Judging whether any of the processing and production processes are successful, whether the cost of the products produced by the method is appropriate compared to another processing method; or the cost of the products produced by the two methods is the same, but using this method The quality of the products produced is improved. In many applications, injection molding or blow molding competes with vacuum forming.
But in terms of packaging technology, vacuum forming technology has no other processing methods to compete with unless it is made of cardboard. The main advantage of vacuum forming is its engineering economy. The composite sheet, the foamed sheet, and the printed sheet are molded to replace the changing vacuum forming machine with a suitable mold change. Thin-walled articles can be vacuum formed from sheets of high melt viscosity, while pellets with the same wall thickness require low melt viscosity pellets. For a small number of plastic parts, the favorable mold cost is another advantage of vacuum forming, and for large quantities of parts, it is very advantageous to achieve a very thin wall thickness and a high output ratio of the vacuum forming machine. .
The smallest part that can be produced by vacuum forming is the packaging material of the tablet or the battery for the watch. It can also produce very large products, such as a garden pool of 3 to 5 m in length. The thickness of the molding material can be from 0.05 to 15 mm, and for the foamed material, the thickness can be up to 60 mm. Any thermoplastic or similar material can be vacuum formed.
The material used for vacuum forming is a sheet having a thickness of 0.05 to 15 mm, and these sheets are semi-finished products obtained by using pellets or powders. Therefore, vacuum forming raw materials add additional cost compared to injection molding.
The sheet needs to be cut during vacuum forming, which will produce scrap. These scraps are pulverized and mixed with the original material to form a sheet again.
In vacuum forming, only one surface of the sheet is in contact with the vacuum forming mold, so that only one surface conforms to the geometry of the vacuum forming mold, and the contour of the other surface of the product is drawn by drawing.
In the field of plastic processing, vacuum forming is considered to be a processing method with great development potential. It is molded and suitable for all areas of plastic packaging. Vacuum forming is also a processing method that requires skilled operation and experience. Today, vacuum molding has evolved into a technically controllable and repeatable process by simulating the process and the necessary expertise.
In recent years, the recycling of scrap produced during the vacuum forming process has become increasingly important. Nowadays, a process has been formed in which the scrap is recycled by mixing with the original material. Waste plastic molded products, such as packaging materials, and even engineering parts, are likely to be recycled under many conditions, but some still need to be developed. The current recoverable substances are mainly chemical materials and energy materials. In order to make breakthroughs in recycling, we must work hard on the ecological and economical nature of the processing.
Vacuum blister products have the advantages of low price, high production efficiency, free choice of shapes and colors, corrosion resistance, light weight and electrical insulation properties, etc., in stationery, toys, daily necessities, Wujinjiaodian, electronic products, food The packaging of cosmetics and other products has been developed into the application of billboards, automobiles, industrial parts, building materials, helmets, washing machines and freezer linings, turnover boxes and agricultural products.
Second, vacuum plastic molding has its own limitations
·Vacuum plastic forming can only produce half-shell products with simple structure, and the wall thickness of the products should be relatively uniform (generally the chamfer is slightly thin), and plastic products with different wall thickness can not be obtained.
·The depth of vacuum forming products is limited. In general, the depth to diameter ratio (H/D) of the container does not exceed one.
· The forming accuracy of the parts is poor, and the relative error is generally above 1%. It is not only difficult to obtain the consistency of the configuration or size of different parts by vacuum forming, and the uniformity of the wall thickness of each part of the same part is difficult to ensure. In addition, some details of the mold during the vacuum forming process are difficult. It is not fully reflected in the product.
