An important industrial and most successful and widely used method of producing articles of thermoplastics is Injection moulding. It is a manufacturing process for producing parts by injecting material into a mould. A wide variety of products are manufactured using injection molding, which vary greatly in their size, complexity, and application.The process is essentially as follows.
Plastic Injection moulding process :-
The moulding material is loaded into the hopper from which it is transferred to a heating section by a feeding device, where the temperature is raised to 150°C to 370°C and pressure is built up. The material melts and is forced by a injection ram at high pressure through a nozzle and sprue into a closed mould which forms the parts.
The mould is in at least two sections, so that it may be split in order to eject the finished component. For the process to be competitive, the mould must be fairly cool and consequently the mould must be cooled by circulating water. Injection moulding machines have a high production capacity some can produce from 12 to 16 thousand parts per shift. This method is suitable for making parts with complex threads and intricate shapes, thin-walled parts etc., Typical parts include: Cups, containers, housings, tool, toys, knobs, communication components such as telephone receivers etc.,
Limitations of the process :- Equipment of cylinder should be non-corrosive Also reliable temperature control are essential. Injection moulding machines range in size from an injection capacity of 12,000mm³ to 2.2×10^6 mm³. The locking forces are applied to the mould usually by hydraulic means, and may vary from 0.1MN to 80MN or even more. The injection pressure may range from 100Mpa to 150Mpa.
Applications:
- Injection moulding is used to create many things such as Cups, Containers, tools, Mechanical parts (Including gears).
- Injection moulding is the most common modern method of manufacturing parts. It is ideal for producing high volumes of the same object.
Advantages:
- Injection moulding allows for high production output rates.
- Often times parts do not need additional finishing process.
- You may also use fillers for added strength.
- More than one-material may be used at the same time when utilizing co-injection moulding.
- Full automation is possible with injection moulding.
- All scrap may be reground to be reused , therefore there is very little waste.
Disadvantages:
- The main disadvantage is cost of tooling and cost of operation.
- In order to be particle, large production runs are necessary.
- Initial tooling costs are higher than other methods.
- There are some design restrictions , so not all compounds are suitable for injection moulding.
