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November 21, 2022
Difference among blister, blow molding and injection molding blister
It is a plastic processing technology. The main principle is to heat and soften the flat plastic hard sheet, and then use vacuum to adsorb it on the surface of the mold. It is formed after cooling. It is widely used in plastic packaging, lighting, advertising, decoration and other industries.
Blister packaging: refers to the general term for plastic products produced by Blister process and packaged with corresponding equipment.
Blister packaging products include: blister shell, tray, blister box, and synonyms include: vacuum cover, blister cover, etc. The main advantages of blister packaging are: saving raw and auxiliary materials, light weight, convenient transportation, good sealing performance, and meeting the requirements of environmental protection and green packaging; It can pack any special-shaped products without additional cushioning materials; The packaged products are transparent and visible, beautiful in appearance, convenient for sales, and suitable for mechanized and automatic packaging, convenient for modern management, manpower saving, and efficiency improvement.
Blister packaging equipment mainly includes: Blister molding machine, punch, sealing machine, high-frequency machine, folding machine. The packaging products formed by packaging can be divided into: card inserting, card absorbing, double bubble shell, half bubble shell, double fold bubble shell, triple fold bubble shell, etc.
Injection molding, that is, thermoplastic injection molding. This method is to melt the plastic material and then inject it into the membrane cavity. Once the molten plastic enters the mold, it will be cooled to form a certain shape according to the mold cavity sample.
The shape obtained is often the final product, and no other processing is required before installation or use as the final product. Many details, such as bulges, ribs, and threads, can be molded in one step by injection molding.
The injection molding machine has two basic components: an injection device and a clamping device for melting and feeding plastics into the mold. The functions of the mold mixing device are: 1. to close the mold under the condition of bearing the injection pressure; 2. Take the product out of the injection device to melt the plastic before it is injected into the mold, and then control the pressure and speed to inject the melt into the mold. At present, there are two designs of injection devices: screw type pre plasticizer or two-stage device, and reciprocating screw. The screw type preplasticizer uses a preplasticizing screw (first stage) to inject molten plastic into the injection rod (second stage).
The screw preplasticizer has the advantages of constant molten mass, high pressure and speed, and accurate injection volume control (using mechanical thrust devices at both ends of the piston stroke). These advantages are required for transparent, thin-walled products and high production rate. Its disadvantages include uneven residence time (leading to material degradation), high equipment costs and maintenance costs.
The most commonly used reciprocating screw injection device does not need a plunger to melt and inject the plastic. Blow molding
Also known as hollow blow molding, a rapidly developing plastic processing method. The tubular plastic parison produced by extrusion or injection molding of thermoplastic resin is placed in the split die while it is hot (or heated to a softened state), and compressed air is introduced into the parison immediately after the die is closed, so that the plastic parison is blown and stuck to the inner wall of the die. After cooling and demoulding, various hollow products are obtained. In principle, the manufacturing process of blown film is very similar to that of hollow products, but it does not use molds. From the perspective of plastic processing technology classification, the molding process of blown film is usually included in extrusion. Blow molding process began to be used to produce low-density polyethylene vials during the Second World War. In the late 1950s, with the birth of high-density polyethylene and the development of blow molding machines, blow molding technology has been widely used.
The volume of hollow containers can reach thousands of liters, and some production has been controlled by computers. Plastics suitable for blow molding include polyethylene, polyvinyl chloride, polypropylene, polyester, etc. The hollow containers obtained are widely used as industrial packaging containers.
According to the parison production method, blow molding can be divided into extrusion blow molding and injection blow molding. The new development includes multi-layer blow molding and tensile blow molding.
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