216
8
8.1.5 Injection Moulding
5 Processing Technology—Injection moulding is the workhorse of
the plastic industries but has limited application in the
composite industry due to its limited use to produce short
fibre- reinforced composite products. However, short fibres
could become long staples, depending upon the mould design
and injection pressure. The injection moulding process is
shown schematically in . Fig. 8.9.
The injection moulding machine has the following important parts:
5 Clamp unit that decides the tonnage of the machine, closes
the mould, and withstands the high injection pressure.
5 Injection unit that injects the molten plastic at a very high
pressure in order to fill the mould cavity.
5 Heating unit that heats the plastic material before the
injection.
5 Control unit that controls all of the processing parameters.
This process uses a specialized mould where the mould deign is
quite complex, including runner gates and multiple cavities. While
injection moulds are costly because they are used in the continuous
process, their durability is an important factor. The mould has two
parts: a mould base and mould cavities.
The important processing parameters for injection moulding are the following:
5 Temperature from feeder zone to injection nozzle
5 Injection pressure
5 Hold time
5 Locking force
5 Mould temperature
Point to Ponder…
High heat capacity of a material
causes a long time to heat or cool it.
Low heat capacity is preferred in
mould materials so that it can be
heated and cooled fast.
Hopper
Ram
H ydraulic
fluid
Motor
Heater
Heater
Screw
Mould
. Fig. 8.9 Injection moulding process [14]
Chapter 8 · Processability in Closed Mould Processing of Polymeric Composites
8
8.1.5 Injection Moulding
5 Processing Technology—Injection moulding is the workhorse of
the plastic industries but has limited application in the
composite industry due to its limited use to produce short
fibre- reinforced composite products. However, short fibres
could become long staples, depending upon the mould design
and injection pressure. The injection moulding process is
shown schematically in . Fig. 8.9.
The injection moulding machine has the following important parts:
5 Clamp unit that decides the tonnage of the machine, closes
the mould, and withstands the high injection pressure.
5 Injection unit that injects the molten plastic at a very high
pressure in order to fill the mould cavity.
5 Heating unit that heats the plastic material before the
injection.
5 Control unit that controls all of the processing parameters.
This process uses a specialized mould where the mould deign is
quite complex, including runner gates and multiple cavities. While
injection moulds are costly because they are used in the continuous
process, their durability is an important factor. The mould has two
parts: a mould base and mould cavities.
The important processing parameters for injection moulding are the following:
5 Temperature from feeder zone to injection nozzle
5 Injection pressure
5 Hold time
5 Locking force
5 Mould temperature
Point to Ponder…
High heat capacity of a material
causes a long time to heat or cool it.
Low heat capacity is preferred in
mould materials so that it can be
heated and cooled fast.
Hopper
Ram
H ydraulic
fluid
Motor
Heater
Heater
Screw
Mould
. Fig. 8.9 Injection moulding process [14]
Chapter 8 · Processability in Closed Mould Processing of Polymeric Composites