group 4 - mat tech presentation

8/3/2019 group 4 - mat tech presentation

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BLOW MOULDING


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Blow molding (also known as blowmoulding or blow forming) is a manufacturingprocess by which hollow plastic parts are formed. Ingeneral, there are three main types of blow molding:extrusion blow molding, injection blow molding,and stretch blow molding. The blow molding

process begins with melting down the plastic andforming it into a parison or preform. The parison is atube-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 ispumped into it. The air pressure then pushes the

plastic out to match the mold. Once the plastic hascooled and hardened the mold opens up and thepart is ejected.
http://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Plastichttp://en.wikipedia.org/wiki/Molding_(process)http://en.wikipedia.org/wiki/Molding_(process)http://en.wikipedia.org/wiki/Plastic


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DIAGRAM OF BLOW MOULDING WITH LABELS


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HISTORY OF BLOW MOULDING There has been evidence found suggesting that Egyptians and

Babylonians blew plastic materials, but Enoch Ferngren andWilliam Kopitke were the first verified people who used the blowmolding process. The process principle comes from the idea

ofglassblowing. Ferngren and Kopitke produced a blow moldingmachine and sold it to Hartford Empire Company in 1937. Thiswas the beginning of the commercial blow molding process.During the 1940s the variety and amount of products were still

very limited and therefore blow molding did not take off untillater. Once the variety and production rates went up the amount

of products created followed soon afterwards. In the UnitedStates soft drink industry, the amount of plastic containers wentfrom zero in 1977 to ten billion pieces in 1999. Today, even agreater amount of products are blown and it is expected to keepincreasing.
http://en.wikipedia.org/wiki/Glassblowinghttp://en.wikipedia.org/wiki/Glassblowinghttp://en.wikipedia.org/wiki/Glassblowing


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MATERIALS The most widely used materials for Blow Molding are:

Low Density Polyethylene (LDPE)

High Density Polyethylene (HDPE) Polypropylene (PP)

Polyvinyl Chloride (PVC)

Polyethylene Terephtalate (PET)


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EXTRUSION BLOW MOULDING The extrusion blow molding process begins with the

conventional extrusion of a parison or tube, using a diesimilar to that used for making plastic pipe.

The parison is commonly extruded downward between thetwo halves of an open blow mold. When the parisonreaches the proper length, the mold closes, catching andholding the neck end open and pinching the bottom endclosed. A rod-like blow pin is inserted into the neck end ofthe hot parison to simultaneously form the threaded

opening and to inflate the parison inside the mold cavity.After the bottle cools, the mold opens to eject the bottle.The excess plastic is trimmed from the neck and bottompinch-off areas.


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Extrusion blow molding:

Can be used to process many different plastics,

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

Requires relatively small capital investment inequipment;

Is suitable for small production runs. Eastman products sold into the extrusion blow

molding market are Eastar copolyester GN046, Eastarcopolyester 6763, Eastar copolyester GN077 and Eastar

copolyester GN071.


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EXTRUSION BLOW MOULDINGDIAGRAM


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INJECTION BLOW MOULDING In the injection blow molding process, the material is injection

molded. The hot material, still on the core pin, is then indexedto the blow molding station where it is blown into a bottle andallowed to cool. For processing PET it is critical that this core pinbe cooled. The bottle is then indexed to the next station andejected. Injection blow molding allows more precise detail in theneck and finish (threaded) area than extrusion blow molding.Little, if any, improvement in physical properties is realized inthe injection blow molding process since very little orientation

occurs. Further, the injection blow molding process is normallylimited to the production of relatively small bottles, i.e., 180 mL(6 fluid oz) or less. Eastapak polymer 9921 has been successfullyused in the injection stretch blow molded process.


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INJECTION BLOW MOULDING DIAGRAM


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STRETCH BLOW MOULDING This process involves the production of hollow objects, such as bottles,

having biaxial molecular orientation. Biaxial orientation providesenhanced physical properties, clarity, and gas barrier properties, whichare all important in products such as bottles for carbonated beverages.

There are two distinct stretch blow molding techniques. In the one-stage process, preforms are injection molded, conditioned to theproper temperature, and blown into containersall in one continuousprocess. This technique is most effective in specialty applications, suchas wide-mouthed jars, where very high production rates are not arequirement.

In the two-stage process, preforms are injection molded, stored for ashort period of time (typically 1 to 4 days), and blown into containersusing a reheat-blow (RHB) machine. Because of the relatively high costof molding and RHB equipment, this is the best technique forproducing high volume items such as carbonated beverage bottles.


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STRETCH BLOW MOULDING DIAGRAM


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COMPARISON BETWEEN EXTRUSION AND

INJECTION BLOW MOULDING Extrusion blow molding

It is best suited for bottle over 200g in weight, shorterruns and quick tool changeover

Machine costs are comparable to injection blow molding Tooling costs are 50% to 75% less than injection

machine It requires sprue and head trimming Total cycle is shorter than injection (since the parison

and blowing can be done using the same machine) Wider choice of resin Final part design flexibility


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Injection blow molding

Best suited for long runs and smaller bottles

No trim scrap

Higher accuracy in final part

Uniform wall thickness Better transparencies with injection blow

molding, because crystallization can be better

controlled Can lead to improve mechanical properties

from improved parison design


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ADVANTAGES & DISADVANTAGES Advantages of blow molding include: low tool and die cost; fast

production rates; ability to mold complex part; producesrecyclable parts

Blow Molding Automation - The Placo X-Y machine wasdeveloped in Japan and has given rise to three-dimensional blowmolding, an automated production method that allows forseamless part incorporation, minimal flash (excess polymer)around the object and increased production speed due to theprecision of the receptacle created.


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Disadvantages of blow molding include: limited tohollow parts, wall thickness is hard to control.

Limited Uses - Low molding is limited to hollowforms, such as plastic containers and bottles, as airpressure is an integral component of the process. Wallthickness is also hard to control, as the larger theproduct being built gets, the thinner the polymer hasto be stretched.


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THE APPLICATIONS IN INDUSTRY The products manufactured by blow molding,

although limited to hollow shaped plastics, are

widely used in many industrial fields and everydaylives. The following are the products that see a lotof blow molded parts:


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Automobile Consumer Electronics Fuel oil tanks Furniture Health & safety Lawn & garden

Marine Medical Packaging Point of sale displays Recreational Seating Sporting goods Toys


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EXTRA APPLICATIONS


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VIDEO


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As a conclusion, blow moulding process is proven tobe a very important process in the indusry. Hence,with the presence of this process, many kinds ofapplication gets the benefit. We hope that blowmoulding can get better and more efficient in future.


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group 4 - mat tech presentation