1. Plastic concept
Definition of plastics (American Plastics Industry Association)
Plastics are mainly composed of carbon, oxygen, hydrogen, nitrogen and other organic or inorganic elements. The finished product is a solid. In the manufacturing process, it is a molten liquid. Therefore, it can be melted by heating, forced to flow, cooled and solidified to form various shapes. This large and diverse group of materials is called plastics.
Plastic parts (hereinafter referred to as plastic parts, the same below) are widely used in every field of modern life, such as home appliances, instruments, wires and cables, building equipment, communication electronics, automobile industry, aerospace, daily hardware, etc.
In recent years, with the rapid development of plastic industry and the continuous improvement of plastic properties, plastic parts have been more widely used. Plastic parts are replacing traditional metal parts in different fields. A reasonably designed plastic part can often replace multiple traditional metal parts, so as to simplify product structure and save manufacturing cost.
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2. Brief introduction to molding process of various plastic parts
There are many processing methods of plastic parts, including injection molding, extrusion molding, calendering molding, blow molding, suction molding and compression molding.
Plastics, a high polymer, can be treated in a variety of ways. Each method has its advantages and disadvantages, and is more suitable for specific applications.
Next, let's see how they are processed through the relevant moving pictures!
2.1 injection (injection)
Injection Molding
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Injection molding is a manufacturing method of manufacturing parts by injecting materials into the mold. The main method of processing plastics is injection molding. In this process, the plastic is placed in the hopper, which then heats and injects the plastic, which is pushed through a long chamber and a reciprocating screw. After that, it is softened into a fluid state. The nozzle is located at the end of the chamber, and the fluid plastic is forced to cool through the nozzle to close the mold. When the plastic cools and solidifies, the semi-finished product exits from the press.
Dynamic drawing is an injection molding process. Its principle is very similar to the syringe in the hospital (so sometimes injection molding is also called injection). In the injection molding machine, the plastic particles are melted, extruded into the mold, and the products are obtained after cooling.
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2.2 plastic extrusion
Plastic Extrusion
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Plastic extrusion is a method of mass production in which the plastic raw material is melted to form a continuous profile. The extrusion process is usually used to manufacture films, continuous sheets, tubes, profiles, bars, sheaths, filaments, wires, and cables. Together with the injection molding machine, the dried plastic is placed in a hopper and fed into a long heating chamber. At the end of the chamber, the material is pressed out with a small opening, or die in the desired shape of the final product. After the plastic leaves the mold, it is placed on a conveyor belt to cool. Blowers are sometimes used in this process to help cool them.
Similarly, although most of the raw materials used in the extrusion process are rubber, there are also cases of plastic extrusion, such as TPV.
2.3 blow molding
Blow Molding
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Blow molding is a molding method for manufacturing hollow plastic products. It is a secondary molding technology that the rubber like parison closed in the mold cavity is inflated into hollow products by means of gas pressure.
Photo 2.4 thermoforming
Thermoforming
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A special plastic processing method for processing thermoplastic sheet into various products. The sheet clamp is heated to the softened state on the frame, and under the action of external force, it is close to the mold surface to obtain the shape similar to the mold surface. After cooling and shaping, the product is finished by trimming. This process is also used for rubber processing. In recent years, thermoforming has made new progress, such as continuous production technology from extruded sheet to hot forming.
The second animation shows the two-piece thermoforming process.
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2.5 compression molding
Compression Molding
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Compression molding is the most commonly used method in thermosetting materials and is not usually used in thermoplastic materials. In this process, the material is extruded into the desired shape. Plastic molding powder and other materials are added to the mixture to produce special qualities. When the mold is closed and heated, the material is hardened to form its desired shape. Temperature, pressure and the length of time used in the process depend on the desired results.
This is actually the rubber process, molding.
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2.6 calendering
Calendering
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Also known as calendering. The last step in heavy leather finishing. It is a finishing process in which the fabric surface is flattened or rolled out with parallel fine and dense diagonal lines according to the plasticity of fibers under mixed heat conditions, so as to improve the luster of the fabric.
2.7 calendering
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What is calendering: a process in which materials are extruded and extended into plastic films and sheets with certain specifications and shapes by special calendering equipment.
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Plastics can also be calendered. The plastic material is fed in, heated and melted, then formed into sheets or films, then cooled and rolled up. The most commonly used calendering material is PVC.
2.8 extrusion molding
Pultrusion
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Extrusion molding is a processing method of blank. Under the action of three-dimensional non-uniform compressive stress, the blank is extruded from the hole or gap of the die to reduce its cross-sectional area and increase its length to become the required product.
2.9 vacuum molding (blister)
Vacuum Forming
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Vacuum forming is often called suction molding, which is a kind of plastic processing technology. The main principle is to heat and soften the flat plastic hard sheet, then vacuum adsorb on the mold surface, and then form after cooling. It is widely used in plastic packaging, lighting, advertising and packaging