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Comparison of advantages and disadvantages of several major processing methods of plastic raw materials

Injection Molding
The principle of injection molding is to add granular or powdered material into the hopper of the injection machine. The material is heated and melted and becomes active. Under the advancement of the screw or piston of the injection machine, it enters the mold cavity through the nozzle and the casting system of the mold. , It is hardened and shaped in the mold cavity. Factors affecting the quality of injection molding: injection pressure, injection time, injection temperature.

1. Short molding cycle, high production efficiency, and easy automation.
2. Plastic parts with messy shapes, accurate dimensions, and metal or non-metal inserts can be formed.
3. Product quality is stable.
4. Wide range of habits.

1. The price of injection molding equipment is higher.
2. The structure of the injection mold is messy.
3. High production cost, long production cycle, not suitable for single and small batch production of plastic parts.

Among industrial products, injection molded products include: kitchen supplies (trash cans, bowls, buckets, pots, tableware, and various containers), shells of electrical equipment (hair dryers, vacuum cleaners, food mixers, etc.), toys and games, automobiles Various industrial products, parts of many other products, etc.
Extrusion molding
Extrusion molding: also known as extrusion molding, it is mainly suitable for the molding of thermoplastics, but also suitable for the molding of some thermosetting and reinforced plastics with better mobility. The molding process is to use a rotating screw to extrude the heated and melted thermoplastic material from the die with the required cross-sectional shape, and then it is shaped by the sizing device, and then passed through the cooler to make it hard and solidify to become the required cross-sectional shape. product.

Process Characteristics
1. Low equipment cost;
2. the operation is simple, the process is simple to control, and it is easy to complete successive automated production;
3. High production efficiency; uniform and fine product quality;
4. After changing the die of the machine head, products or semi-finished products with various cross-sectional shapes can be formed.

In the area of ​​product planning, extrusion molding has strong applicability. Extruded products include pipes, films, rods, monofilaments, flat belts, nets, hollow containers, windows, door frames, plates, cable cladding, monofilaments and other profiled materials.

Blow Molding
The molten thermoplastic material extruded from the extruder is clamped into the mold, and then air is blown into the material. The molten material expands under the effect of air pressure and adheres to the wall of the mold cavity. Cooling and solidification become the method of the desired product shape. Blow molding is divided into two types: film blowing and hollow blowing.

Film blowing
Film blowing is the process of extruding molten plastic into a cylindrical thin tube from the circular gap of the die of the extruder, and blowing compressed air into the inner cavity of the thin tube from the center hole of the die to inflate the thin tube to a diameter. Larger tubular film (commonly known as bubble tube) is rolled up after cooling.

Hollow blow molding:
Hollow blow molding is a secondary molding technique that uses gas pressure to inflate the rubber-like parison closed in the mold cavity into a hollow product. It is a way to produce hollow plastic products. According to different manufacturing methods of parisons, hollow blow molding includes extrusion blow molding, injection blow molding, and stretch blow molding.
(1) Extrusion blow molding: Extrusion blow molding is to use an extruder to extrude a tubular parison, clamp it in the mold cavity and seal the bottom while it is hot, and then blow compressed air into the inner cavity of the tube blank for inflation molding .
(2) Injection blow molding: The parison used is formed by injection molding. The parison is left on the core mold of the mold. After closing the mold with a blow mold, compressed air is introduced from the core mold to inflate the parison, cool, and demold the product to obtain the product.
(3) Stretch blow molding: Place the parison that has been heated to the stretching temperature in a blow mold, stretch it longitudinally with a stretch rod, and stretch and inflate it with compressed air in the transverse direction to obtain Product approach.

The product has uniform wall thickness, low weight, less post-processing, and small waste corners; it is suitable for the production of large-scale small precision products.
Film blow molding is mainly used to manufacture thin plastic molds; hollow blow molding is mainly used to manufacture hollow plastic products (bottles, packaging barrels, spray cans, fuel tanks, cans, toys, etc.). To

The article is reproduced from Lailiqi Plastic Industry. The URL of this article: http://www.lailiqi.net/chuisuzixun/548.html

Post time: Aug-15-2021