INJECTION MOLDING by BUNGAs

By FatyngNadyrah | Updated: Sept. 26, 2024, 10:58 a.m.

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Chapter 5

polymeric process
FATIN NADHIRAH BINTI ISHAK (2018243702)
SITI NUR ATIRAH BINTI AWANG (2018678472)
NURUL AMIRAH SYAFIQAH BINTI YA'ACOB (2018443228)
WHAT IS POLYMER?
Polymers are large molecules made by bonding (chemically linking) a series of building blocks
APPLICATION OF POLYMER
commercial
engineering
TOYS
BEESWAX
POLYMER CAN BE DIVIDED BY TWO categories!
chemical structure remains unchanged during heating and shaping

more important commercially

comprising more than 70% of total plastic tonnage

THERMOPLASTICS
undergo curing process during heating and shaping

causing a permanent change in molecular structure

once cured, they cannot be remelted

THERMOSETS
INJECTION MOULDING
WHAT IS INJECTION MOULDING?
> injection moulding is a method of manufacture of parts by injecting molten material into mould.
> for producing parts in a large volume.
> most widely use moulding process for thermoplastics.
> some thermosets and elastomer are injection moulded.
> commonly used in mass production processes where the same parts are made thousand and even millions of times in a row.
TWO PRINCIPLE COMPONENTS
CLAMPING UNIT
INJECTION UNIT
melts and deliver polymer melt, operate much like an extruder
opens and closes mould each injection cycle
and now its PROCESSES!!!
INJECTION MOULDING
1. THE MOULD CLOSES 
the injection mould closes and two halves of the injection mould are clamped together and the process timer begins
2. INJECTION
the heated plastic is injected into the mold while the air is moved out along the seperator line and through the hole in the injection pin. Runners, hole designs and entrances ensure the mold is properly filled
3. COOLING PERIOD
once the mould has been filled, the parts are cooled. The piece is given the exact cooling time required to harden the material used.
4. THE RESIN IS PLASTICISED
during cooling, the barrel screws and pulls the new plastic resin into the barrel. this plastic resin is extracted from hopper material. heather band maintains the required barrel temperature for the type of resin used.
5. EJECTION
the mould opens while the shaft of the ejector pushes the pin forward. this step causes the component to fall below the mould into the bin. unused hooks and runners can be recycled for future use.
and now let's take a look at advantages and disadvantages of the process
1. fast production
2. high repeatability
3. precision
Advantages
INJECTION MOULDING
1. high initial tooling cost
2. large part size limitations
3. careful design needed
Disadvantages
DEFECTS
FLOW LINES
1. appear as a wavy pattern often a slightly different colour than the surrounding area and generally on narrower sections of the moulded component.
2. also appears as ring-shaped bands.
BURN MARKS
typically appear as black or rusted-coloured dicoloration on an edge or surface of a moulded plastic part
WARPING
deformation that can occur in injection moulded products when different parts of a component shrink unevenly
WELD LINES
appear on the surface of a moulded part where the molten material has converged after splitting off into two or more directions in a mould.
HAVE A NICE DAY
THANK YOU FOR WATCHING

INJECTION MOLDING by BUNGAs

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