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`Blow Molding Plastics - Engineer's Handbook
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`Manufacturing Processes - Blow Molding Plastics
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`Manufacturing: Plastic Molding & Forming
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`Plastic Molding
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`http://www.engineershandbook.com/MfgMethods/blowmolding.htm
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`Mattel Ex. 2004
`Dynacraft v. Mattel
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`Albright
`Silicone
`Molding
`- Boston
`Medical
`Silicone
`Molder
`Silicone
`Production-
`Prototype -
`Molded
`Parts Fast
`Delivery
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`albrightsilicone.c…
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`Blow Molding
`
`Blow Molding is a highly developed molding
`technology developed back in the late 1800's to
`produce celluloid baby rattles. It is best suited for
`basically hollow parts (such as plastic bottles)
`with uniform wall thicknesses, where the outside
`shape is a major consideration.
`
`The first polyethylene bottle was manufactured
`using the blow molding process in December of
`1942. This was the real beginning of a huge
`industry which currently produces 30 to 40
`billion plastic bottles per year in the U.S. alone.
`
`The Basic Process
`
`1. A thermoplastic resin is heated to a
`molten state
`2. It is then extruded through a die head to
`form a hollow tube called a parison.
`3. The parison is dropped between two
`mold halves, which close around it.
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`4. The parison is inflated.
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`5. The plastic solidifies as it is cooled inside
`1
`the mold.
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`Blow Molding Plastics - Engineer's Handbook
`6. The mold opens and the finished
`component is removed.
`
`Albright Silicone
`Molding - Boston
`Medical Silicone Molder
`Silicone Production-Prototype -
`Molded Parts Fast Delivery
`
`Variations
`
`There are basically four types of blow molding
`used in the production of plastic bottles, jugs and
`jars. These four types are:
`
`1. Extrusion blow molding
`2. Injection blow molding
`3. Stretch blow molding
`4. Reheat and blow molding.
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`albrightsilicone.com
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`Extrusion blow molding is perhaps the simplest
`type of blow molding. A hot tube of plastic
`material 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; just as if one were blowing up a balloon. When the hot plastic material is blown up and touches the
`walls of the mold the material "freezes" and the container now maintains its rigid shape.
`
`Injection blow molding is part injection molding and part blow molding. With injection blow molding, the hot
`plastic material is first injected into a cavity where it encircles the blow stem, which is used to create the neck and
`establish the gram weight. The injected material is then carried to the next station on the machine, where it is
`blown up into the finished container as in the extrusion blow molding process above. Injection blow molding is
`generally suitable for smaller containers and absolutely no handleware.
`
`Extrusion blow molding allows for a wide variety of container shapes, sizes and neck openings, as well as the
`production of handleware. Extrusion blown containers can also have their gram weights adjusted through an
`extremely wide range, whereas injection blown containers usually have a set gram weight which cannot be
`changed unless a whole new set of blow stems are built. Extrusion blow molds are generally much less expensive
`than injection blow molds and can be produced in a much shorter period of time.
`
`Stretch blow molding is perhaps best known for producing P.E.T. bottles commonly used for water, juice and a
`variety of other products. There are two processes for stretch blow molded P.E.T. containers. In one process, the
`machinery involved injection molds a preform, which is then transferred within the machine to another station
`where it is blown and then ejected from the machine. This type of machinery is generally called injection stretch
`blow molding (ISBM) and usually requires large runs to justify the very large expense for the injection molds to
`create the preform and then the blow molds to finish the blowing of the container. This process is used for
`extremely high volume (multi-million) runs of items such as wide mouth peanut butter jars, narrow mouth water
`bottles, liquor bottles etc.
`
`The reheat and blow molding process (RHB) is a type of stretch blow process. In this process, a preform is
`injection molded by an outside vendor. There are a number of companies who produce these "stock" preforms on a
`commercial basis. Factories buy the preforms and put them into a relatively simple machine which reheats it so
`that it can be blown. The value of this process is primarily that the blowing company does not have to purchase the
`injection molding equipment to blow a particular container, so long as a preform is available from a stock preform
`manufacturer. This process also allows access to a large catalog of existing preforms. Therefore, the major expense
`is now for the blow molds, which are much less expensive than the injection molds required for preforms.
`
`There are, however, some drawbacks to this process. If you are unable to find a stock preform which will blow the
`container you want, you must either purchase injection molds and have your own private mold preforms injection
`molded, or you will have to forego this process. For either type of stretch blow molding, handleware is not a
`possibility at this stage of development. The stretch blow molding process does offer the ability to produce fairly
`lightweight containers with very high impact resistance and, in some cases, superior chemical resistance.
`
`Whether using the injection stretch blow molding process or the reheat and blow process, an important part of the
`process is the mechanical stretching of the preform during the molding process. The preform is stretched with a
`"stretch rod." This stretching helps to increase the impact resistance of the container and also helps to produce a
`very thin walled container.
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`Blow Molding Plastics - Engineer's Handbook
`The extrusion blow molding process allows for the production of bottles in a wide variety of materials, including
`but not limited to: HDPE, LDPE, PP, PVC, BAREX®, P.E.T., K Resin, P.E.T.G., and Polycarbonate. As noted
`above, a wide variety of shapes (including handleware), sizes and necks are available. Injection blow molding
`allows for the production of bottles in a variety of materials, including but not limited to: HDPE, LDPE, PP, PVC,
`BAREX®, P.E.T., and Polycarbonate.
`
`Besides the P.E.T. noted above for stretch blow molding, a number of other materials have been stretch blown,
`including polypropylene. As time goes on and technology moves forward, more materials will lend themselves to
`stretch blow molding as their molecular structures are altered to suit this process.
`
`Blow Molding Machine Manufacturers -
`
`For shuttle extrusion type machines Bekum, Battenfeld/Fischer, and Hayssen are probably the best known in the
`United States. For injection blow molding machines JOMAR is a well known brand. For stretch blow and reheat
`and blow type machines there are Sidel, Nissei and other machines produced by Johnson Controls and others. For
`wheel machines you might wish to contact Johnson Controls or Wilmington Machinery.
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`Blow Molding
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`AdChoices
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`Polycarbonate
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`Plastic Sheets
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`Blow Moulding
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