The document discusses various aspects of plastics manufacturing processes. It describes how plastics are formed and shaped through molding, cutting, forming, machining and joining. Some key plastics manufacturing processes discussed include injection molding, blow molding, compression molding, transfer molding, reaction injection molding, extrusion, and thermoforming. The properties of plastic parts are influenced by the manufacturing method and processing parameters used. Large, complex shapes can often be formed as a single unit through these plastic fabrication processes.

1. PLASTICS
MANUFACTURING-
“forming and shaping plastics.”

2. INTRODUCTION
2
 The processing of plastics involves operations
similar to those used to form and shape metals.
 Plastics can be molded,cut,formed,machined &
joined.
 Plastics are usually shipped to manufacturing
plants as pallets or powders & are melted just
before the shaping process.
 Plastics are available as sheets,plate,rod,and
tubing,which may be formed into a variety of
products.

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 The properties of plastic parts are influenced greatly
by the method of maufacturing and by the processing
parameters . Materials in these classes can often
provide integral & variable color.
 The processes used to manufacture the shape can
frequently produce the desired finish and precision.
 The joining and fastening operations also tend to be
different from those used with metals.
 Large , complex shapes can often be formed as a
single unit.

4. PLASTICS
4
- Plastic is a material consisting of any of a wide range
of synthetic or semi-synthetic organics that are
malleable and can be molded into solid objects of
diverse shapes.Plastics are typically organic polymers
of high molecular mass, but they often contain other
substances.
- They are usually synthetic, most commonly derived
from petrochemicals, but many are partially natural.
- PLASTICITY:-
Plasticity is the general property of all
materials that are able to irreversibly deform without
breaking

5. TYPES OF PLASTICS
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-:COMMON PLASTICS:-
 Polyester (PES)
 Polyethylene terephthalate (PET)
 Polyethylene (PE)
 High-density polyethylede (HDPE)
 Polyvinyl chloride (PVC)
 Polyvinylidene chloride (PVDC) (Saran)
 Low-density polyethylene (LDPE)
 Polypropylene (PP)

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 Polystyrene (PS)
 High impact polystyrene (HIPS)
 Polyamides (PA) (Nylons)
 Acrylonitrile butadiene styrene (ABS)
 Polyethylene/Acrylonitrile Butadiene Styrene (PE/ABS)
 Polycarbonate (PC)
 Polycarbonate/Acrylonitrile Butadiene Styrene
(PC/ABS)
 Polyurethanes (PU)

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-:SPECIAL PURPOSE PLASTICS :-
 Maleimide/Bismaleimide
 Melamine formaldehyde (MF)
 Plastarch material
 Phenolics (PF) or (phenol formaldehydes)
 Polyepoxide (Epoxy)
 Polyetheretherketone (PEEK)
 Polyetherimide (PEI) (Ultem)

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 Polyimide
 Polylactic acid (PLA)
 Polymethyl methacrylate (PMMA) (Acrylic)
 Polytetrafluoroethylene (PTFE)
 Urea-formaldehyde (UF)
 Furan
 Silicone
 Polysulfone

9. PROPERTIES OF PLASTICS
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Following are the general properties of plastics.
1. STRENGTH:-
The plastics are sufficiently strong and can be used for
load bearing structural members. The strength of plastics can further be
increased by reinforcing them with various fibrous materials.
2. WEATHER RESISTANCE:-
The plastics, prepared from phenolic resins,
are only good in resisting weather effects. Certain plastics are seriously
affected by ultraviolet light.
3. FIRE RESISTANCE:-
Plastics, being organic in nature, are
combustible. But the resistance to fire temperatue depends upon the
plastic structure.
 Cellulose acetale plastics burn slowly.
Polyvinyl chloride (PVC) plastics are non-inflammable.

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4. DURABILITY:-
Plastics generally possess sufficient
durability, provided they offer sufficient surface
hardness. Thermoplastic varieties are found to be
attacked by termites and rodents.
5. DIMENSIONAL STABILITY:-
Plastics easily maintain its
shape and do not go under plastic deformations.
6. CHEMICAL RESISTANCE:-
Plastics offer great resistance
to moisture, chemicals and solvents. Many plastics are
found to possess excellent corrosion resistance.
Plastics are used to convey chemicals.
7. THERMAL RESISTANCE:-
The plastics have low thermal
conductivity and therefore foamed or expanded
varieties of plastics are used as thermal insulators.

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9. MOISTURE RESISTANCE:-
This property depends upon variety of
plastics used, for example, cellulose plastics are considerably affected
by the presence of moisture, whereas polyvinyl chloride plastics offer
high resistance to moisture.
10. DUCTILITY:-
Plastics, generally, have low ductility and hence
plastic structural members may fail without prior warning.
11. MISCELLANEOUS PROPERTIES:-
 Plastics are available in variety of colors,
both opaque and transparent.
 Plastics possess excellent insulating
property, so used as electric insulators.
 Plastics are clean, light and shining, so they
need not be given any finish such as

12. RESIN
12
 In polymer chemistry and material science, resin is a
"solid or highly viscous substance," which are typically
convertible into polymers. Such viscous substances
can be plant-derived or synthetic in origin. They are
often mixtures of organic compounds.

13. -:RESIN:-
13

14. THERMOPLASTIC RESIN
14
Thermoplastic resin is a polymer compound that becomes
soft or fluid when heated and then returns to its original
solid state when cooled. This compound is used in molding
processes like injection molding, which requires the raw
material to be in a liquid or plastic state to fill the mold
completely. When cooled, the resin or polymer solidifies to
form the finished product, which is then ejected or dropped
out of the mold. The resin is used to manufacture many
consumer products.

15. THERMOSETTING RESIN
15
 Thermosetting resins are rigid
polymeric materials that are
resistant to higher temperatures
than ordinary thermoplastics.
These materials are normally
made up of lines of polymers,
which are highly cross-linked.
 The heavily cross-linked structure
produced by chemical bonds in
thermoset materials is directly
responsible for the high
mechanical and physical strength
compared with thermoplastics or

16. Synthetic Resin And Their Raw
Materials
16

17. ELASTOMERS
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 An elastomer is a polymer with viscoelasticity (having
both viscosity and elasticity) and very weak inter-
molecular forces, generally having low Young's
modulus and high failurestrain compared with other
materials.
 Elastomers are amorphous polymers existing above
their glass transition temperature, so that considerable
segmental motion is possible.
 Elastomer is a big fancy word, and all it means is "rubber".
Some polymers which are elastomersinclude polyisoprene
or natural rubber, polybutadiene, polyisobutylene, and
polyurethanes.

18. (A) is an unstressed polymer; (B) is the same polymer
under stress. When the stress is removed, it will return to
the A configuration. (The dots represent cross-links)
18

19. STRUCTURE OF Thermoplastic ,
Elastomer & Thermoset
19

20. FABRICATIONS OF PLASTICS
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 Plastic fabrication is the
design, manufacture, or
assembly of plastic
products through one of a
number of methods.
Some manufacturers
prefer plastic fabrication
over working with other
materials (such as metal
or glass) due to the
process’s advantages in
certain applications.
Plastic's malleability and
cost-effectiveness can
make it a versatile and
durable material for a

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 Casting , Blow Molding , Compression Molding , Transfer
Molding , Cold Molding , Injection Molding, Reaction
Injection Molding , Extrusion, Thermoforming, Rotational
Molding and Foam Molding are all processes that are used
to shape polymers.
 Each has its distinct set of advantages and limitatioms that
relate to part design , compatible materials,and producion
cost.

22. PLASTICS,ELASTOMERS AND COMPOSITE
MATERIALS
22

23. 1. CASTING
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 Casting is the simplest of the shape forming processes
because no fillers are used and no pressure is required.
 While not all plastics can be cast, there are a number of
castable thermoplastics, including acrylics, nylons,
urethanes, and PVC plastisols.
 Since cast plastics contain no fillers, they have a distinctly
lustrous appearance, and a wide range of transparent and
translucent colors are available.
 Some thermosets (such as phenolics, polyesters, epoxies,
silicones, and urethanes) can also be cast, as well as any
resin that will polymerize at low temperatures and
atmospheric pressure.

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 A steel pattern is dipped into molten lead,withdrawn, and
allowed to cool. A thin lead sheath is produced when the
pattern is removed, and this becomes the mold for the
plastic resin .Curing occurs ,either at room temperature or
by heating for long times at temperatures in the range of
65° to 95° C. After curing, the product is removed, and the
lead sheath can be reused
fig:- steps in the casting of thermoset plastic parts
using a lead sell mold.

25. 2. BLOW MOLDING
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 Blow molding is the process of inflating a hot, hollow,
thermoplastic preform or parison( a tube-like piece of plastic
with a hole in one end through which compressed air can pass.)
inside a closed mold so its shape conforms to that of
the mold cavity. A wide variety of hollow parts, including plastic
bottles, can be produced from many different plastics using this
process.
 In general, there are three main types of blow molding:
extrusion blow molding, injection blow molding, and injection
stretch blow molding.
 A variety of blow molding processes have been developed, the
most common being used to convert thermoplastic
polyethylene,polyvinyl chloride(PVC), polypropylene, and

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A solid bottom ,hollow –tube preform, known as parison, is
made from heated plastic by either extrusion or injection
molding. The heated preform is then positioned between the
halves of a split mold,the mold closes,and the preform is
expanded against the mold by air or gas pressure. The mold
is then cooled, the halves separated and the product is
removed.

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B L O W M O L D I N G

28. 3. COMPRESSION MOLDING OR HOT-
COMPRESSION MOLDING
28
Compression molding is a forming process in which a
plastic material is placed directly into a heated metal mold,
then is softened by the heat, and forced to conform to the
shape of the mold as the mold closes.
The process employs thermosetting resins in a partially
cured stage, either in the form of granules, putty-like
masses, or preforms.
Compression molding is a high-volume, high-pressure
method suitable for molding complex, high-
strength fiberglass reinforcements.
However, compression molding often provides poor

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 The compression molding starts, with an allotted amount of
plastic or gelatin placed over or inserted into a mold. Afterward
the material is heated to a pliable state in and by the mold.
Shortly there after the hydraulic press compresses the pliable
plastic against the mold, resulting in a perfectly molded piece,
retaining the shape of the inside surface of the mold. After the
hydraulic press releases, an ejector pin in the bottom of the
mold quickly ejects the finished piece out of the mold and then
the process is finished

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COMPRESSION MOLDING PRESS

31. 4. TRANSFER MOLDING
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 Transfer molding is a process where the amount of material
is measured and inserted before the molding process takes
place. The material is then preheated and loaded into a pot
and a plunger is then used to force the material from the pot
through the runner system into themold cavities.
 Transfer molding is different from compression molding in
that the mold is enclosed [Hayward] rather than open to the
fill plunger resulting in higher dimensional tolerances and less
environmental impact.
 The material most commonly used for transfer molding is a
thermoset polymer.
 Defects known as voids and dry resin (in the case of resin

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 The fill material ( preheated solid or a liquid) is loaded into a
chamber known as the pot. A ram or plunger forces material
from the pot into the heated mold cavity. If feed-stock is initially
solid, the forcing pressure and mold temperature melt it.
Standard mold features such as sprue channels, a flow gate
and ejector pins may be used. The heated mold ensures that
the flow remains liquid for complete filling. Once filled the mold
can be cooled at a controlled rate for optimal thermoset curing.

33. SCHEMATIC PROCESS OF TRANSFER MOLDING
33

34. 5. COLD MOLDING
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 In cold molding, the uncured thermosetting materials is pressed
to shape while cold and Is then removed from the mold and
cured in a separate oven.
 While the process is faster and more economical, the resulting
products generally lack good surface finish and dimensional
precision.
 In general, advantages of these materials include high arc
resistance, heat resistance, good dielectric properties,
comparatively low cost, rapid molding cycles, high production
with single-cavity molds (thus low tool cost), and no need for
heating of molds.

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 On the other hand, they are relatively heavy, cannot be
produced to highly accurate dimensions, are limited in
color, and can be produced only with a relatively dull
finish.

36. 6. INJECTION MOLDING
36
 Injection moulding can be performed with a host of materials,
including metals, (for which the process is
called diecasting), glasses,elastomers, confections, and most
commonly thermoplastic and thermosetting polymers. Material
for the part is fed into a heated barrel, mixed, and forced into a
mould cavity, where it cools and hardens to the configuration
of the cavity.
 Granules of raw materials are fed by gravity from a hopper into
a cavity that lies ahead of a moving plunger. As the plunger
advances, the material is forced through a preheating
chamber and on through a topedo section, where it is mixed,
melted, and superheated.

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 The superheated material is then driven through a nozzle that
seats against a mold.
 Other types of injection units control the flow of material and
generate the injection pressure with screws that have both
rotational and axial movements, or combinations of screws and
plungers.

38. Defects And Disadvantages Of INJECTION
MOLDING
38

39. Injection Molding Machine Work Flow.
39

40. 7. REACTION INJECTION MOLDING
40
 Reaction injection molding (RIM) is similar to injection
moldingexcept thermosetting polymers are used, which
requires a curingreaction to occur within the mold. Common
items made via RIM include automotive bumpers, air spoilers,
and fenders.
 In this process two or more liquid reactants are metered into
a unit where they are intimately mixed by the impingement of
liquid streams that have been pressurized to a value between
13 and 20 MPa. The combined materials flows through a
pressure –reducing chamber and exits the mix-head directly
into a mold.
 An exothermic chemical reaction takes place between the two
components, resulting in thermoset polymerisation.

41. Schematic Diagram Of Reaction
Injection Molding
41

42. High Pressure Reaction Injection Molding
Equipment
42

43. Defects in reaction injection molding
43

44. 8. EXTRUSION
44
Plastics extrusion is a high-volume manufacturing process
in which raw plastic is melted and formed into a continuous
profile.
Extrusion produces items such as pipe/tubing
, weatherstripping, fencing,deck railings,window
frames, plastic films and sheeting, thermoplastic coatings,
and wire insulation.
This process starts by feeding plastic material (pellets,
granules, flakes or powders) from a hopper into the barrel of
the extruder. The material is gradually melted by the
mechanical energy generated by turning screws and by
heaters arranged along the barrel. The molten polymer is

45. Schematic Diagram Of Extrusion
Process
45

46. Typical Shapes Of Polymer Extrusions
46

47. 9. THERMOFORMING
47
 Thermoforming is a manufacturing process where a plastic
sheet is heated to a pliable forming temperature, formed to a
specific shape in a mold, and trimmed to create a usable
product.
 Thin-gauge thermoforming is primarily the manufacture of
disposable cups, containers, lids, trays, blisters, clamshells,
and other products for the food, medical, and
general retail industries. Thick-gauge thermoforming includes
parts as diverse as vehicle door and dash panels, refrigerator
liners, utility vehicle beds, and plastic pallets.

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 The heated sheet indexes into a form station where a mating
mold and pressure-box close on the sheet, with vacuum then
applied to remove trapped air and to pull the material into or
onto the mold along with pressurized air to form the plastic to
the detailed shape of the mold.
 After a short form cycle, a burst of reverse air pressure is
actuated from the vacuum side of the mold as the form tooling
opens, commonly referred to as air-eject, to break the vacuum
and assist the formed parts off of, or out of, the mold.
 Its simplified version is VACUUM FORMING.

49. Process Showing Thermoforming
49
Fig:-A type of thermoforming where thermoplastic sheets
are shaped using a combination of heat and vacuum

50. 10. ROTATIONAL MOLDING
50
 Rotational Molding, also called rotomolding or rotocast, is
a thermoplastic process for producing hollow parts by
placing powder or liquid resin into a hollow mold and then
rotating that tool bi-axially in an oven until the resin melts
and coats the inside of the mold cavity.
 Rotational Molding involves a heated hollow mold which
is filled with a charge or shot weight of material. It is then
slowly rotated (usually around two perpendicular axes)
causing the softened material to disperse and stick to the
walls of the mold.

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 In order to maintain even thickness throughout the part,
the mold continues to rotate at all times during the heating
phase and to avoid sagging or deformation also during the
cooling phase.
 Process is shown below by simple animation :-

52. Schematic Process Of Rotational
Molding
52

53. Advantages And Diadvantages Of
Rotational Molding
53

54. 11. FOAM MOLDING
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 In foam molding, a foaming agent is mixed with the plastic
resin and releases gas or volatilizes when the material is
heated during molding.
 The materials expand to 2 to 50 times their original
size,resulting in products with densities ranging from 32 to
640 g/L.
 Open-cell foams have interconnected pores that permit the
permeability of gas or liquid.
 Closed-cell foams have the property of being gas-or liquid-
tight.
 Prefoamed polystyrene beads can be expanded and fused to

55. Process Of Foam Molding
55

56. OTHER PLASTIC- FORMING
PROCESSES
56
CALENDERING:- A mass of dough like thermoplastic is
forced between and over two or more counter-
rotating rolls to produce thin sheets or films of
polymer, which are then cooled to induce hardening.
DRAWING:- Conventional drawing can be used to
produce fibres.

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ROLLING:- Rolling can be performed to change the shape
of thermoplastic extrusions.
SPINNING:- Filaments, fibres, and yarns can be produced
by spinning, a modified form of extrusion in which
molten thermoplastic polymer is forced through a die
containing many small holes called a spinneret.

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