Fiber Reinforced Plastic

Composite Material Processing

Mechanics of Composites (ME 4129)

Content*

Pulforming

Thermo-forming

Injection Molding

Blow Molding

* Only remaining topics are included here.

Pulforming

It is the subsequent step to make semicircular profile

from length and to change cross section at one or more location.

This process is used to manufacture components of irregular shapes.

The long parts that are curved instead of being and whose cross section vary throughout length.

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Pulforming

2 Source: counterpointmagazine.org

Fig. 1: Pultrution Process

Pulforming

3 Source: Fundamental of modern Manufacturing, M.P. Groover, 4ed.

Fig. 2: Pulforming Process

Applications

Beams and girders used in roof structures

Bridges

Ladders

Frameworks

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Thermo-Forming

Thermoforming is a manufacturing process in which

a composite sheet is heated to a pliable forming temperature,

formed to a specific shape in a mold.

Thermoforming is a plastic processing technique, so it is a

polymer processing technique in which the thermoplastic

sheets are formed with the application of heat and pressure

in a mold.

The components manufactured are thin sheets and thin walled

sections.

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Keywords Thin Sheets

Heat

Pressure

Mould

Thermoplastic sheets

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Classification

Vaccum Thermoforming

Pressure Thermoforming

Matched Die Thermoforming

Vacuum Thermoforming

7 Source: techminy.com

Fig. 3: Vaccum Thermoforming

Vacuum Thermoforming

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Vaccum is applied to form the heated thermoplastic sheet.

The thermoplastic sheet is clamped with help of claming unit.

Sheet is heated till it is soften and then vaccum is applied

quickly.

Air is pulled out quickly between mold cavity and sheet

Vaccum is created and sheet takes the shape of mold cavity.

The formed product is cooled and ejected from mold cavity.

Steps:

Pressure Thermoforming

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It is similar to vaccum thermoforming.

The air pressure required is higher as same

compared to vaccum thermoforming.

The heated plastic sheet is placed on the mold

surface and then air-pressure is applied instantly on

the sheet.

A high pressure is developed between soft steel and

pressure box.

Steps:

Pressure Thermoforming

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Due to high pressure the preheated plastic sheet

deforms instantly and takes the shape of mould

cavity.

The deformed plastic sheet is allowed to cool for

some time.

The formed part upon solidification is ejected.

The appendages are trim and polished for end use

Pressure Thermoforming

11 Source: https://bioplasticsnews.com/

Fig. 4: Mechanical Thermoforming

Fig. 5: Pressure Thermoforming

Matched Die-forming

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It is also named as mechanical forming.

Mold comprises of two parts i.e. die and punch.

Themoplastic sheet is soften by application of heat.

Preheated sheet is placed on die and mechanical

pressure is applied through punch.

Matched Die-forming

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Air between die and sheet is removed using vaccum

pump.

Subsequently sheet takes the shape of mould.

The formed part upon cooling takes shape of mold.

The appendages are trim and polished for end use

ABS Plastics

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A common thermoformed plastic, ABS is comprised of

acrylonitrile, styrene and butadiene.

Applications

Protective headgear

Golf club heads

Musical instruments, like recorders

Toys

HIPS Plastics

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Applications

Packing peanuts

Food and drink Items

Bottles and disposable cutlery

HIPS plastic are also known as polystyrene.

Characteristics

Clear and Brittle

Used for protective packaging

HDPE Plastics

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Applications

Plastic bags and bottles

Water Pipes

Cable installation

HDPE (high-density) polyethylene is a stronger

thermoformed plastic comprised of petroleum

Characteristics

Exceptional strength to density ratio.

PVC Plastics

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Applications

Sewage pipes

Electric cables

Flooring

Faux leather clothing

polyvinyl chloride is created with suspension

polymerization

Characteristics

Strong, hard structure and rigid plastic.

Can withstand extreme temp. and pressure

PET Plastics

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Applications

Synthetic Fibers

Bottle Production

polyethylene terephthalate is dried to increase its

resistance.

Characteristics

Have great resistance and barriers

Most recycled types of plastics

Advantages

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Initial cost of setup is low

Production cost is low

Thermal stresses are low

Posses good dimensional stability

Flexibility in design

Rapid prototyping

Disadvantages

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Finishing in terms of trimming is required

Surface finish is of poor quality.

Products may not have uniform thickness

Few materials can be used

Limited to thin plastic sheets

Injection Molding

It is a manufacturing process for producing parts by

injecting molten material into a mold.

Injection molding can be performed using wide range of materials as metals, glasses, thermoplastic , thermosetting polymers etc.

The general process includes heating of material and feeding the same into a heated barrel, mixing then injecting into a mold cavity.

The charge is then cooled and hardened to the configuration of the cavity.

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Injection Molding

22 Source: ecomolding.com

Fig. 6: Steps in Injection Molding Process

Injection Molding

23 Source: injectionmouldingworld.com

Fig. 7: Steps in Injection Molding Process

Types of Injection Molding

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Reciprocating screw type injection molding

Plunger type injection molding

Hand injection molding

Hand Injection Molding

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Hand level is used to move plunger.

Plunger then applies the pressure to molten plastic.

Molten plastic is pushed in mold cavity and takes the shape of die.

Manu. of Small plastic buttons for shirts.

Fig. 8: Hand Injection Molding Machine

Source: plastictoday.com

Plunger type injection molding

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Fig. 9: Plunger type injection molding Machine

Source: argomold.com

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Powder or the raw material comes from hopper.

The raw material enters into cylinder.

Same is heated through cylinders through entire length of cylinder.

The heated plastic then melts and same is pushed by piston in the molds.

Plunger type injection molding

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Mold consist two parts movable and fixed

Fixed part is attached to nozzle and movable part can slide in longitudinal direction.

The cooling of finished product can be liquid or air.

The plunger force is regulated by hydraulic means.

Plunger type injection molding

Reciprocating Screw Inj. Molding

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Fig. 10: Reciprocating injection molding Machine

Source: adplastics.co.uk/

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Rotating screw pushes molten plastic through

nozzle into the mold.

Movable platen slides over the tie rods and

moves in longitudinal direction.

Raw material comes from the feed hooper and

is heated and melted in barel.

Reciprocating Screw Inj. Molding

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The difference between plunger type and

screw type injection molding is through which

molten metal is pushed in mold cavity.

In plunger type injection mechanism we use

piston or plunger.

In screw type injection molding we use

rotating screw.

Reciprocating Screw Inj. Molding

Advantages

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Detailed Features and Complex Geometry

High Efficiency

Enhanced strength

Ability to use multiple material simultaneously

Automation to save manufacturing cost

Advantages

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Wide range of material can be used.

Low scrap rates

Good Color Control

Reduced finishing requirement

Product consistency

Enhanced Strength

Disadvantages

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High tooling costs and long set up lead times

Part design restrictions

Small runs of parts can be costly

Rapid cooling is often required

Experienced operator

Applications

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Wire Spools

Packaging

Bottle caps

Automotive Dashboards

Pocket Combs

Toys, Musical Instruments, One Piece Chairs

Blow Molding

Blow molding is a molding process used to create

hollow objects made of plastic. Like other molding processes, it involves the use of heated, liquid material that’s forced into a mold cavity under pressure.

Blow molding, also known as blow moulding, is a molding process in which heated plastic is blown into a mold cavity to create a hollow object.

The defining characteristic of a blow molding is that it’s used to create hollow objects.

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Blow Molding

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Fig. 11: Blow molding process

Source: https://in.pinterest.com/

Blow Molding Vs Injection Molding

Blow molding is used to create hollow objects,

whereas injection molding is used to create solid objects.

For hollow objects, only blow molding offers a fast and effective solution.

For injection, the plastic is sealed in the injection chamber and mold throughout the entire process.

The blow mold begins when the mold is removed from the plastic, which gives some more freedom for the blowing to expand the product.

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Types of Blow Molding

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Extrusion blow molding

Injection blow molding

Extrusion blow molding

It is simple blow molding process.

A hot tube of plastic material, called a parison, is dropped from an extruder and captured in a water cooled mold.

Once the molds are closed, air is injected through the top or the neck of the container, similar to blowing up a ballon.

The hot plastic material is blown up and touches the

walls of the mold the material "freezes"

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EBM-Advantages

Lower mold cost

It is simple blow molding process.

Multi layer capability

Window stripe on bottles, angled and offset necks,

handleware, and multiple necks

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EBM-Disadvantages

With increase in dia. of mold, the corners and areas

with the thinnest walls have close tolerance.

Extrusion molding has longer cooling times than

injection molding.

It is not possible to mold in holes except after the

molding.

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EBM-Applications

Plastic bottles, jars, and Jugs

Plastics, including HDPE, PVC, PC, PP, and PETG

Bottles requiring multi-layer technologies

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Injection blow molding(IBM)

It is process of inflating a hot, hollow thermoplastic

parison inside a closed mold so that it takes shape of

mold cavity.

Injecting the plastic into tube to form a plastic tube.

Blow the tube into a cavity mold to form the hollow

part.

Ejecting the part

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IBM-Advantages

Exact neck dimension.

Thick even walls.

Invisible parting lines.

No scrap, No trimming and No waste.

Not much auxiliary equipment required.

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IBM-Disadvantages

The process is more expensive than extrusion blow

molding.

There is a compromise between preform wall

thickness and blow up ratio.

The process is not suitable for manufacturing of

bottles with handles.

Prior design is required before any process can

begin. 46

IBM-Application

Medical devices such as surgical syringes.

Open container like buckets.

Plastic housing of different tools.

Daily use products such as tooth brushes.

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