Page 113 - Module DMV20173

6.0 POLYMER PROCESSING

6.2 INJECTION MOLDING

1. Injection Molding is a manufacturing technique for making parts from thermoplastic
material.

2. In some circumstances, thermoses plastics can also be used with injection molding.
Molten plastic is injected at high pressure into a mold, which is the inverse of the
product's shape.
3. The mold is made by a moldmaker (or toolmaker) from metal, usually either steel or

aluminium, and precision-machined to form the features of the desired part.
4. Injection molding is very widely used for manufacturing a variety of parts, from the
smallest component to entire body panels of cars.
5. Injection Molding is the most common method of production, with some commonly made
items including bottle caps and outdoor furniture.

6. Figure 6.2 shows the schematic illustration of a typical injection molding component.

6.2.1 ADVANTAGES

1. Injection molding is a very economical method of producing large quantities of a complex
component very rapidly that is finished in one operation.
2. Sprues and runners can be reground and reused.

3. Generally mold costs are expensive and to amortise these high tooling costs require
reasonable production runs to be economic.

Example 6.1

Briefly describe the injection molding process.

Solution:

Injection molding is a process in which a polymer is heated to a highly plastic state and
forced to flow under high pressure into a mold cavity, where it solidifies. The molding is
then removed from the cavity.

BPLK 145 DMV 20173