Blow molding originated in the 1830, and it wasn't until 1979 that blow molding entered the stage of wide application. The application of blow molding products involves various aspects of life such as automobiles, office equipment, household appliances, and medical treatment. Blow molding is a method of inflating a hot-melt parson closed in a mold to form a hollow product by means of gas pressure, and is one of the most commonly used plastic processing methods.
Hollow blow molding is divided into injection blow molding, extrusion blow molding and stretch blow molding. This article focuses on the extrusion blow molding suitable for large and complex blow molding products. In the extrusion blow molding process, the tube blank is directly extruded by the extrude and hanged in a pre-divided cavity installed directly under the head; when the sagged parson reaches the specified length, the mold is closed immediately and close The cutout of the equipment die cuts the tube blank; compressed air is introduced from the blow pin of the mold to blow the parson against the mold wall to form; the pressure is maintained, and the product is opened after the product is cooled and shaped in the cavity.
1. Opportunities and challenges facing the two-dimensional blow molding industry
Blow molding technology is constantly developing with various technological advances in the plastics industry and machinery manufacturing. In the design and production of blow molding products, modern design ideas and design tools are constantly incorporated into it. Engineering and technical personnel should make full use of advanced The design concept, combined with human experience, improves the efficiency of all aspects of product design and manufacturing, thereby improving the quality and market competitiveness of blow molded products. With the changes in market demand, the blow molding industry has ushered in great development opportunities in raw materials, machinery and equipment, auxiliary production, etc.
1.1 Raw materials
In order to further meet the functional and performance requirements of blow molded products, especially some special needs, such as the environmental protection and safety requirements of industries such as medicine and food packaging, the variety of raw materials for blow molding grades is more abundant and diverse, and the processing performance tends to be better. Various characteristics such as corrosion resistance, UV resistance, and wear resistance are available; on the other hand, the development of materials with lower cost, easy processing, low density, and recycle ability has brought a wider application market to blow molding.
1.2 Mechanical equipment
Blow molding machinery and equipment are more precise, efficient and intelligent. Multi-head co-extrusion, multi-layer co-extrusion, multi-point wall thickness control, high temperature and high strength wear-resistant screws are emerging in an endless stream, which further meets the needs of the blow molding process; blow molding machinery The equipment has been greatly improved, the precision and efficiency of blow molding machinery and equipment blow molding machinery, and assist the automation of production (operation) equipment. "Precision and high efficiency" not only means that the mechanical equipment has higher speed and higher pressure in the production molding process, but also requires that the products produced can achieve higher stability in terms of appearance size fluctuation and part weight fluctuation, that is, It is said that the size and shape of each part of the manufactured product have high precision, small deformation and shrinkage, and the appearance, internal quality and production efficiency of the product must reach a high level. The newer results have the following aspects.
(1) Re-blow molding using improved infrared heating technology.
(2) Very high-speed rotary extrusion pressure, mainly used in the production of milk bottles.
(3) The mold is attached to the shuttle press to compensate the jet flow phenomenon.
(4) Multi-layer continuous extrusion blow molding impermeable container.
(5) Continuously heat-set PET bottles are produced through strict control of oriented crystallization and thermal crystallization, preform and mold temperature, blowing pressure, and residence time of the parson in the mold cavity.
(6) The storage cylinder head is improved so that it can extrude heat-sensitive plastics such as ABS-R, modified PPD and PVC. Moreover, the redesigned hand piece can be quickly assembled and disassembled during production to facilitate the cleaning of plastics. At the same time, streamlined flow channels can be designed for the analysis of plastic theological characteristics and computer flow channel analysis to facilitate the formation of heat-sensitive plastics.
1.3 Auxiliary production
Automatic gripping parts, automatic raw material drying and matching equipment, automatic debarring, cutting, weighing, drilling, leak detection, etc., have gradually become mature and localized, and low cost.
Product packaging containers and industrial products will have greater growth, and injection blow molding and multi-layer blow molding will have rapid development.
At the same time, under the new situation, it also faces greater challenges to the traditional industry of blow molding, as follows.
(1) Plastic processing technology is more intelligent and diversified: 3D printing technology has replaced part of the injection molding and blow molding processing market, and advanced welding technology (infrared, hot air, etc.) helped injection molding to complete structures that could not be completed before, replacing part of the blow molding structure. design.
(2) Energy saving and emission reduction: The blow molding industry itself is of high energy consumption, low blank utilization rate, large energy consumption for processing and recycling, and serious heat loss.
(3) Cost reduction: Now the labor cost in the industrial market is getting higher and higher, and the automation of blow molding products is relatively difficult. It is difficult for people to recruit and stay. How to reduce costs and increase efficiency is already imminent in the increasingly competitive market environment .
2. How to improve the efficiency of two-dimensional blow molding production, how to effectively improve the competitiveness of blow molding, the current market mainly has the following aspects:
(1) Three-dimensional blow molding replaces two-dimensional blow molding, mainly to reduce the proportion of product flash blanks, reduce the energy consumption of repeated heating of plastic recycling, and increase the bursting strength of the product, and the local control is more accurate; the current mainstream Cortes, ST Etc. have been widely introduced into the Chinese market.
(2) Multi-station co-extrusion: one die head, two dies, the die can be moved, the blanks are continuously extruded through the die head, which increases the production efficiency. Generally, small products and dies are suitable for use.
(3) Multi-die co-extrusion: multiple die heads, multiple dies, simultaneous extrusion production, greatly improve production efficiency, the efficiency can be doubled, some domestic better blow molding equipment companies have mature models in Sale.