Mumbai University > Mechanical Engineering > Sem 5 > Production process 3

Marks: 5 M

Year: Dec 2014

Plastic injection molds

• Plastic injection molding is the preferred process for manufacturing plastic parts.
• Injection molding is used to create many things such as electronic housings, containers, bottle caps, automotive interiors, combs, and most other plastic products available today.
• It is ideal for producing high volumes of plastic parts due to the fact that several parts can be produced in each cycle by using multi-cavity injection molds.
• Some advantages of injection molding are high tolerance precision, repeatability, large material selection, low labor cost, minimal scrap losses, and little need to finish parts after molding.
• Some disadvantages of this process are expensive upfront tooling investment and process limitations.

Reasons why Plastic injection moulds are preferred

• Most polymers may be used, including all thermoplastics, some thermosets, and some elastomers.
• There are tens of thousands of different materials available for injection molding.
• The available materials mixed with alloys or blends of previously developed materials means that product designers can choose from a vast selection of materials to find the one that has exactly the right properties.
• Materials are chosen based on the strength and function required for the final part; but also each material has different parameters for molding that must be considered.
• Common polymers like Epoxy and phenolic are examples of thermosetting plastics while nylon, polyethylene, and polystyrene are thermoplastic.

Pin ejection method

• Cylindrical pins are used for ejection purpose, in case of square and rectangular components minimum four pins at the four corners are required and in case of cylindrical component minimum three pins at 120° apart is required based on the component profile, size and area of ejection the number of pins to be increased. Visible ejection marks will be there on component