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Compression MoldingNeslihan Yamur

11/12/2012

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Compression Molding

ProcessThe process of molding a material ina confined shape by applying

pressure and usually heat.Compression molding process is followed

by two step first one preheating and

pressurizing.

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Process Description

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Process DescriptionCharge is placed in cavity ofmatched mold in the open position,

Mold is closed by bring the twohalves together,

Pressure is exerted to squeeze the

resin so that it fills the mold cavity,While under pressure the mold isheated which cures the resin.

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Process Description

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Stages in Compression molding cycle

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Stages in Compression molding

cycleThe various stages of thecompression molding cycle time can

be represented as a function of theforce required to close the old at aconstant rate.

In the plastication stage the forceincreases rapidly as the polymerfeed is compressed and heated.

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Stages in Compression molding

cycleThe second stage flow commences,once the yield stress of the

elastomer is exceeded.tcis the point at which the moldfills and compression of the melt

occurs.Mold filling the majority of chemicalreaction should take place after tc.

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Parameters1.The quantity of molding material

2.Pressure of the molding process

Range of pressure 2000-3000 psi13.!-20." #Pa$

3.Mold temperature

%emperature range 300F to 375F (149C- 191C)

&.Cure time variables.

%'e period re(uired to 'arden t'ermosetting material to partial and

complete polymeri)ation is called cure time

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Types of compression molding Sheet molding compound(SMC)

Sheet molding process involves placing areinforcement, such as a glass mat, betweensandwiching layers of a thermoplastic andheating the materials to produce a single sheetof material.

Bul molding compound(BMC)

Bulk molding compounds by producing a billetof molten material that is placed into acompression molding press which molds themolten material into a part.

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Materials used in this process

%'ermosetting polymers

*iber reinforced composite %'ermoplastic+

-,ltra ig' #olecular eig't Polyet'ylene

,#P/$

- ong *iber reinforced %'ermoplastics

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Material properties affected by the process

Density

Strengt'

nisotropic property fiber orientation$

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!dvantages

ow cost

,niform density

,niform s'rinage due to uniform flowmpro4ed impact strengt'

Dimensional accuracy

nternal stress and warping are minimi)edS'ort cycle time

ig' 4olume production

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"isadvantages

Curing time large

,ne4en parting lines present Scrap cannot be reprocessed

ig' initial capital in4estment

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!pplications # products

Dinnerware

5uttons

6nobs

ppliance ousings

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!pplications # products

Radio Cases

utomoti4e

as' trays 7 electrical parts

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ReferencesPolymer Processing Fundamentals, A.Tim, Carl Hanser Verlag, Munich, 1998

Effect of Molding Parameter onCompression Molded Sheet MoldingCompounds Part, Jin-Ho Jeong,Journalof Materials Processing , 1997

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