Plastic mold knowledge

Plastic mold knowledge

First, plastic mold common sense - injection molding

Thermoplastic injection molding is a process in which plastic material is melted and then injected into a membrane cavity. Once the molten plastic is in the mold, it is cooled and moulded into a certain shape according to the mold cavity. The resulting shape is often the final product and no additional processing is required before installation or use as a final product. Many details, such as protrusions, ribs, and threads, can be molded in a single injection molding operation.

An injection molding machine has two basic components: an injection device for melting and feeding plastic into the mold, and a die closing device. The function of the and mold device is: 1. Make the mold close under the condition of bearing the injection pressure; 2. 2. Take out the product The injection device melts the plastic before it is injected into the mold, and then controls the pressure and speed to inject the melt into the mold. There are two designs for injection devices currently in use: screw preplasticizer or two-stage device and reciprocating screw. The screw preplasticizer uses a preplasticizer screw (first stage) to feed the molten plastic into a feed rod (second stage).

The advantages of screw preplasticizers are constant melt mass, high pressure and speed, and precise 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 rates. Disadvantages include uneven residence time (resulting in material degradation), high equipment costs and maintenance costs.

Reciprocating screw injection devices, the most common, do not require a plunger to melt and inject the plastic.

A. Extrusion and blow molding

Extrusion blow molding is a method of making hollow thermoplastic parts. The widely used blow moulding objects are bottles, barrels, cans, boxes, and all containers for food, beverages, cosmetics, medicines, and daily necessities. Large blow - moulded containers are commonly used for packaging of chemicals, lubricants and bulk materials. Other blow moulds are balls, bellows, and toys. For the automotive industry, fuel tanks, car shock absorbers, seat backs, center brackets, and armrests and headrest claddings are blow moulded. For machinery and furniture manufacturing, blow moulded parts may be casings, door frames, frames, pottery POTS, or boxes with an open side.

polymer

The most common blow moulding material is high-density polyethylene, the polymer from which most milk is made. Other polyolefins are also often processed by blow molding. Styrene polymers, polyvinyl chloride, polyesters, polyurethane, polycarbonate and other thermoplastics can also be used for blow molding, depending on their use.

Engineered plastics have recently gained widespread acceptance in the automotive industry. Material selection is based on mechanical strength, weather resistance, electrical, optical and other properties.

process

Three-fourths of blow molding products are made by the extrusion blow molding method. The extrusion process is to force the material through a hole or die to make a product.

Extrusion and blow molding process consists of five steps: 1. Plastic embryo (hollow plastic tube extrusion); 2. 2. Close the flap closing mold on the mold, clamp the mold and cut off the mold; 3. Blow the mold to the cold wall of the mold cavity, adjust the opening and maintain a certain pressure during cooling, open the mold, and write down the blown parts;

5. Trim the flaps to get the finished product.

Mold Manufacturing Information