Plastic Forming Techniques: Injection, Extrusion & Molding
Plastic Molding Techniques: High Pressure Molding
High pressure molding was introduced in plastics with the advent of pressure. There are three types:
Compression
In this process, the plastic material (powder) is introduced into the open mold, which is heated and typed as a initial state. After that, the press closes the mold and presses the plastic material. The plastic is the result of the CVID company, which obtains the molded part due to the first and second conformed time, and may be removed from the mold.
Connectors, electrical insulators, Bakelite, etc., are molded products.
Extrusion
In extrusion, the material is properly fed through an endless screw that travels through a cylinder to produce a nozzle that is indefinite. Combining long strips of the molded parts, the nozzle produces bars that are perfect.
Two types of extrusion processes are used to make tubes, fabrics, and air injection. Pressure is applied to the screw through an orifice in the head of the press. By regulating the air, it is possible to achieve tubes of different and precise dimensions.
Injection
Injection consists of introducing plastic from a hopper into the cylinder, where it is heated and sent to the mold. Inside the cylinder is an endless screw that is actuated by the piston of a syringe. When enough heat is applied, the endless screw pushes the molten plastic into a steel mold.
The injected plastic is cooled by means of water circulating through channels in the mold. The injection process is well suited for the production of large series of parts.
Press Forming Processes
Press forming is used to form laminates for the application of plastics by heat and pressure to adapt them to a mold.
Thermoforming with Vacuum
Vacuum thermoforming consists of removing the air between the foil and the mold it is placed on. It is used to obtain consumer products such as food packaging and embossed items.
Thermoforming with Blowing
This consists of applying air pressure against a plastic laminate until it adapts to the mold. It is used for cup fabrication and hollow parts.
Mechanical Thermoforming
Mechanical thermoforming involves no direct application of force on the laminate. The laminate sits in the spacing between the male part and the female cavity part.
Other Processes
Casting
Casting consists of pouring molten plastic material into a liquid mold, where it solidifies. Due to its shrinkage and cost, it is little used, although the process is useful for producing large series of parts.
Foaming
Foaming consists of introducing air or another gas into the mass of plastic, forming permanent bubbles.
Design of Plastic Parts
Objective: To reduce the number of components in our manufactured parts, reduce the cost of parts, reduce assembly work, reduce control costs, increase product life, guarantee good operation, add value to the product by adding new characteristics, and increase commercial appeal.
Shape of the Part Depends On:
The function to be performed, the expected operating conditions, the selected material, and the method employed. The design ultimately consists of creating a part that is as light as possible, as compact as possible, and as adapted to the required conditions as possible.