This document discusses different types of plastics used in manufacturing. It describes thermoplastics, which can be reshaped when heated, and thermosets, which cannot be reshaped once formed. Common thermoplastics used in injection molding include ABS and PETE. Injection molding involves injecting molten plastic into a mold cavity to form solid parts. Important considerations for plastic component design include adding ribs for stiffness and strength, designing bosses for mounting, and creating holes using core pins. Maintaining a uniform wall thickness can help avoid defects during the molding process. The document also outlines the SPI plastic identification coding system.
2. PLASTICS
TYPES OF PLASTIC
Classifications of plastics:-
Thermoplastics
A polymer that softens and melts gradually
when heated and it can be reshaped when
still warm.
Thermo sets
A polymer that can’t be reshaped after
manufacture
3. WHY USE THERMOPLASTICS
1.Thermoplastics don’t release gases or
water, vapour if they are correctly dried
after they processing
2.The softening or melting by heating
allows welding and thermoforming
3.The processing cycles are very short
because of the absence of the chemical
reaction of cross linking
6. INJECTION MOULDING
What is Injection Moulding
Injection moulding is a manufacturing process for
making parts from thermoplastic materials
Makes solid parts
A part’s thickness is influenced by the mould and
core relationship
8. TYPES OF INJECTION MOULDING
1. Reaction injection moulding:-A mixture of two to four
components in the proper chemical ratio is accomplished by a high-pressure
2.Rapid injection moulding:-Rapid Injection Moulding allows us to
make prototype injection moulded parts in a production thermoplastic
3. fusible core injection moulding:-it is used in the manufacture
of moulded components with cavities or undercuts, which would not be possible with
tools having demandable cores.
11. • ABS is a terpolymer made by
polymerizing styrene and acrylonitrile in the presence
of polybutadiene.
Acrilonitrile butadiene styrene
12. ADVANTAGES
• High impact strength
• Good stiffness
• Good colourability
• Excellent surface quality
• High diamentional stability at elevated
temperature
• Good chemical resistance
• Good stress cracking resistance
16. IMPORTANT OF DRAFT ANGLE
1. The boundaries between mould parts
become visible on the plastic part.
2. There will be flashes between the mould
parts.
3.The heat regulation of the mould becomes
difficult because separate cooling circuits are
necessary for moving parts. Necessarily it is
not always even possible.
17. DESIGN CONSIDERATIONS
FOR PLASTIC COMPONENTS
•When it comes to plastic product development, there are
certain design aspects that are to be taken into consideration.
1. Ribs
•Many times, product design specialists need to increase the
stiffness of a particular component as it needs to withstand
substantial load that is applied to its design
18. During plastic components designing there are many
critical parameters that should be maintained, these could
be the drafting angle, parting line, maintaining a uniform
wall thickness and so on, so that by maintaining these
parameters stress in mould, sink marks, warpage, and
tolerances during the moulding of the part can be avoided.
To maintain uniform thickness across the radius and
horizontal & vertical walls
To provide ribs to strengthen the boss
To create ribs for uniform flow of mold and weight
reduction
20. 3. Holes
Holes are usually made in the moulded
parts. The core pins that are inserted
into mould cavity give rise to the holes
when that part gets moulded
22. •Avoid designs with thin areas surrounded
by thick perimeter sections as they are
prone to gas entrapment problems
•Maintain uniform nominal wall thickness
•Avoid wall thickness variations that result
in filling from thin to thick sections
24. THERMOPLASTICS TYPES SPI
NUMBERS
Today, manufacturers follow a coding system and place a
number, or SPI code, on each plastic product, usually moulded
into the bottom.
SPI code of 1 PETE:- polyethylene terephthalate
Items made from this plastic are commonly recycled.
PETE plastic is used to make many common
household items like beverage bottles, medicine jars,
peanut butter jars, combs, bean bags, and rope.
Recycled PETE is used
25. SPI code2: plastic made with high-density
polyethylene, products are commonly recycled. Items
made from this plastic include containers for milk,
motor oil, shampoos and conditioners, soap bottles
SPI code 3: made with low-density polyethylene,
SPI code4: is made with polyvinyl chloridePVC
is used for all kinds of pipes and tiles, but it's most
commonly found in plumbing pipes.
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