moulding is a manufacturing process in which molten plastics are injected
into a steel mould with a hollow cavity at high pressure. The plastics
fill up the cavity and solidify after cooling. A moulded plastic part
is then ejected from the mould after mould open. This is a mass production
process in which plastic parts are made in low cost and high speed.
The steel mould is
vital in this process; therefore mould making is a very challenging job
and is hi-tech.
2. TECHNICAL OUTLINE
Generally, a plastic
mould consists of the following parts:
- Mould base
The mould base is a standard part purchased from the mould base suppliers.
It holds all the other mould components together. Trainees are required
to open up pockets for the mould inserts by CNC machining.
- Cavity and Core
The core and cavity are the main part of the mould. The trainees are
required to decide the parting line of the product and machine the mould
cavities into these two steel blocks. Trainees are required to used
different machining methods that they had learnt in the training to
produce the parts. It includes, basic machining, EDM, wire-cut, CNC
machining, High speed machining, hand fitting and mould polishing.
- Cooling system
Trainees are required to design and make a suitable cooling system to
cool down the mould during moulding.
- Running and gate
Suitable runner and gate system is required to feed the plastic material
into the mould. Trainees can make use of the flow simulation software
to facilitate the design of the gate location.
- Ejection system
Trainees are required to design and make a suitable ejection system
to remove the molded parts from the mould.
The mould produced will be trail run in an injection-moulding machine
in the Plastic workshop. It is required to complete 10 good shots from
the moulds, otherwise, modifications will be required until a satisfactory
result is obtained.
In this project,
the trainees are required to design and manufacture a plastic mould for
a new product. The design must bear the identity of the PolyU. The size
of the product should not larger than 150 mm x 150 mm and should be within
the capacity of the injection moulding machine.
Trainees are required
- Design and manufacture
the plastic mould based on the given outline and specifications;
- Schedule the manufacturing
- Prepare a bill
of materials and a budget estimation for the whole project; and
- Conduct commissioning
Upon completion of
the project, a group presentation and a group report are also required.