The principle of injection molding is to add the granular or powdery raw materials into the hopper of the injection machine. The raw materials are heated and melted into a flowing state. Driven by the screw or piston of the injection machine, they enter the mold cavity through the nozzle and the pouring system of the mold, and harden and finalize in the mold cavity. Factors affecting the quality of injection molding: injection pressure, injection time, injection temperature.
advantage:
1. Short molding cycle, high production efficiency, easy to realize automation
2. Plastic parts with complex shape, accurate size and metal or non-metal inserts
3. Stable product quality
4. Wide range of adaptation
Disadvantages:
1. High price of injection equipment
2. Complex structure of injection mold
3. High production cost, long production cycle, not suitable for single piece and small batch production of plastic parts
Application:
Among the industrial products, injection molding products include: kitchen supplies (garbage cans, bowls, buckets, kettles, tableware and various containers), shells of electrical equipment (hair dryer, vacuum cleaner, food mixer, etc.), toys and games, various products of the automobile industry, and parts of many other products.
Extrusion molding
Extrusion molding: also known as extrusion molding, mainly suitable for the molding of thermoplastics, also suitable for the molding of some thermosetting and reinforced plastics with better fluidity. The forming process is to use the rotating screw to extrude the thermoplastic raw materials which are heated and melted from the head with the required cross-section shape, and then set them by the finalizer, and then make them harden and solidify through the cooler to become the products with the required cross-section.
Process characteristics:
1. Low equipment cost;
2. The operation is simple, the process is easy to control, and it is convenient to realize continuous automatic production;
3. High production efficiency; uniform and compact product quality;
4. By changing the die, the products or semi-finished products with various section shapes can be formed.
Application:
In the field of product design, extrusion has a strong applicability. Extrusion products include pipe, film, bar, monofilament, flat belt, net, hollow container, window, door frame, plate, cable cladding, monofilament and other profiles.
Blow molding
Blow molding: it is a method to clamp the melt thermoplastic raw material extruded from the extruder into the mold, then blow air into the raw material, the melted raw material expands under the action of air pressure, fits to the mold cavity wall, and finally cools and solidifies into the required product shape. Blow molding can be divided into film blow molding and hollow blow molding
Film blow molding:
Film blowing is to extrude the molten plastic from the circular gap of the die of the extruder head as a cylindrical thin tube, and at the same time blow compressed air from the center hole of the extruder head to the inner cavity of the thin tube, blow the thin tube into a larger diameter tubular film (commonly known as bubble tube), and roll it after cooling.
Hollow blow molding:
Hollow blow molding is a kind of secondary molding technology, which uses the gas pressure to blow the rubber like blank closed in the mold cavity into hollow products. It is a method to produce hollow plastic products. According to the different manufacturing methods of blank, hollow blow molding includes extrusion blow molding, injection blow molding and stretch blow molding.
1) Extrusion blow molding: the extrusion blow molding is to extrude the tubular blank with an extruder, clamp it in the die cavity while it is hot and seal the bottom, and then inject compressed air into the inner cavity of the tube blank for blow molding.
2) Injection blow molding: the mold used is made by injection molding. The mould blank is left on the core mould of the mould. After the mould is closed by blow molding, compressed air is introduced into the core mould, the mould blank is expanded, cooled and demoulded to obtain the product.
3) Stretch blow molding: place the parison that has been heated to the stretch temperature in the blow molding die, stretch longitudinally with the stretch rod, stretch and blow horizontally with the compressed air blown in, so as to obtain the product.
advantage:
It is suitable for the production of small precision products with large batch.
Application:
Film blow molding is mainly used to make plastic thin mold; hollow blow molding is mainly used to make hollow plastic products (bottles, packaging barrels, watering pots, oil tanks, cans, toys, etc.).
