EXTRUSION BLOW MOLDING

PRESENTED BY

Fahad Rafiq

Reg #2014-UET-KIT-Mech-21

D.R AQ Khan Instetute Mianwali

Subject Code : 241

Name Of Subject : Manufacturing Technology

Name of Unit : Molding

Topic : Extrusion Blow Molding

BLOW MOLDING:

What Is Blow Molding?“Blow molding, also known as blow forming, is a

manufacturing process by which hollow plastic parts are formed.”

It is used to made hollow parts such as plastic bottles. vido

Blow Molding Process The blow molding process begins with melting down the

plastic and forming it into a parison . The parison is a tube-like piece of plastic with a hole in one end in which compressed air can pass through. The parison is then clamped into a mold and air is pumped into it. The air pressure then pushes the plastic out to match the mold. Once the plastic has cooled and hardened the mold opens up and the part is ejected.

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COMPNENTS FOR BLOW MOLDING:

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Historical Development

Year Development

1930 The first applications for blow molding were for cellulose nitrate

1940 Introduction of LDPE (Low Density Polyethylene ). With LDPE, the plastic industry growth rapidly

1942 The first polyethylene bottle was manufactured using the blow molding process

1950 The demand for blow molding increases by the mass production of High Density Polyethylene (HDPE) and Polypropylene (PP) for various applications

The principle of blow molding

A simple explanation of the principle of blow molding is similar to inflating a balloon

BASIC PROCESS

TWO MAIN PROCESSESTO preform (or parison) of hot plastic resin in a

somewhat tubular shape is created.A pressurized gas, usually air, is used to expand the

hot preform and press it against a mold cavity. The pressure is held. until the plastic cools.

Blow molding processes

Blow molding processes

Extrusion blow molding Injection blow molding Stretch blow molding

( Classification based on parison/preform formation )

What is Extrusion?Extrusion is the process by which a block/billet of metal is reduced in cross section by forcing it to flow through a die orifice under high pressure. Vido

Extrusion blow molding

(Courtesy : http://www.et.byu.edu/groups/mfg355/pages/lectures/powerpoint_ppt/13%20blow%20molding.ppt)

EXTRUSION BLOW MOLDING: In Extrusion blow molding (EBM), plastic is melted and

extruded into a hollow tube (a parison). This parison is then captured by closing it into a cooled metal mold. Air is then blown into the parison, inflating it into the shape of the hollow bottle, container or part. After the plastic has cooled sufficiently, the mould is opened and the part is ejected.

1)Reciprocating screw. 2)Compressed air.3)Hopper. 4)Granules.5)Barrel. 6)Heaters.7)Grinding, Mixing. 8)Actuator's hydraulic generator.9)Draw plate. 10)Core/Punch.

N eck ring insert

P inch -o ff insert

F lash pocke t

M o ld cav ity

M old gu ide p ins

C oolingchannels

Extrusion Blow Mold

(Courtesy : http://industrialblowmolding.com/?page_id=22)

Extrusion Blow Mold

1. Neck-ring insert

2. Cooling water ports

3. Cut-off insert

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2

3

1

3

2

(Courtesy : http://industrialblowmolding.com/?page_id=22)

Extrusion blow molding:

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2 3

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Blow molding

Two important terms: Parison and preform : Parison is the part that is used in blow molding where air is inflated to from the desired shape. It is closed on one end. Here the preform is same as parison but there is thread in the open end in preform. Preform is mostly used in bottles .

Figure: Parison Figure :Preform

Step 1

Step 2

Step 3

Step 4

(Courtesy : http://www.et.byu.edu/groups/mfg355/pages/lectures/powerpoint_ppt/13%20blow%20molding.ppt)

Blow Molding

Blow Molding

Blow Molding

Blow Molding

Types of Extrusion blow molding:

Continuous Extrusion molding:In extrusion molding, plastics is continuously extruded and the individual parts are

cut off by knife. vido

Intermittent extrusion molding:In straight intermittent extrusion, extruder screw run ,stops and pushes melt out. Here, accumulator is used to gather the mold.

Extrusion blow molding

Continuous extrusion moldingIntermittent extrusion

molding

CLASSIFICATION OF EXTRUSION PROCESSES

Extrusion

By Direction By Equipment

By Operating Temperature

Indirect / Backward

Direct / Forward

Hot Cold Horizontal Vertical

Process Parameters

Parison characteristics size, shape, straightness, wall thickness, mechanical properties

Inflation pressureMold design

cooling, ventingBlow ratio= Mold diameter/Parison Diameter (1.5 to 3 are common

Most thermoplastics can be blow molded

Some typical applications are

HDPE : High Density Polyethylene (stiff bottle, toys, cases, drum) LDPE : Low Density Polyethylene (flexible bottle)PP : Polypropylene (higher temperature bottle)PVC : Polyvinyl Chloride (clear bottle, oil resistant containers)PET : Polyethylene terephthalate (soda pop bottle)

Application

(Courtesy : http://industrialblowmolding.com/?page_id=22)

Extrusion blow molding: Advantage: Low molding cost resulting from lower pressure used Low tool cost due to simple structure Fast production due to small processing cycle Ability to mold complex part

Disadvantage: Limited to hollow parts Low strength of the product

Materials used in blow molding: Most thermoplastics can be blow molded

Some typical applications are

HDPE : High Density Polyethylene (stiff bottle, toys, cases, drum) LDPE : Low Density Polyethylene (flexible bottle) PP : Polypropylene (higher temperature bottle) PVC : Polyvinyl Chloride (clear bottle, oil resistant containers) PET : Polyethylene terephthalate (soda pop bottle)

Mitchel Plamondon

Materials Considerations

One critical requirement is that the

polymer must have good meltstrength.

The common blow molded plastics are:

• Polyolefins– HDPE– LDPE– Polypropylene (PP)

• PVC• PET

December 09, 2006

http://upload.wikimedia.org/wikipedia/en/2/2a/Soft_drink_shelf.JPG

PET bottles are excellent barrier materials and are widely used for soft drinks

Factor effecting blow molding:• Parison characteristics: Size, shape, straightness, wall thickness, mechanical strength.• Inflation pressure: Pressure will be set according to the process. • Mold design : Size of the mold, the material the mold is made with.

• Blow ratio

Here, the blow ratio must be 1.5 to 3

Mold diameter

Parison diameter

Process Material Blow molded parts can be formed from a variety of

thermoplastic materials, including the following: Low Density Polyethylene (LDPE) High Density Polyethylene (HDPE) Polyethylene Terephtalate (PET) Polypropylene (PP) Polyvinyl Chloride (PVC)

ADVANTAGES OF Blow Molding

• Well suited to low and high production rates.• Quick product revisions for increased flexibility.• Tooling is less expensive than other molding. • Each part price is less than Rotational Molding.

• Trim and flash reusable into finished parts.

DISADVANTAGES OF Blow Molding • Environmental Disadvantages effecting.• Process and Material Limitations.• Inability to produce bottles with calibrated neck

finishes.• Machines typically dedicated to a narrow range of

sizes.• Trimming required

Blow Molding Applications

• Milk bottles • Pharmaceutical bottles • Antifreeze bottles • Polypropylene bottles • Coliseum seats • One-piece chair • Ice chests and coolers • Double-wall player case • Garbage cans • Drums • Fuel tanks

Application In Pakistan IndustriesTabraiz mold engineering Lahore Pakistan. ( products:

pet blow mold, machine parts, labeling parts)Thermosole industries (pvt) ltd. Kotlakhpat. (covering

90% of blow molding automotive market in Pakistan) Kalson engineering in Lahore. (services in mold

making)

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Any question?

The end