View source for Industrial Plastics Moulding

[[File:Www.GIFCreator.me scf30H.gif|Plastic Injection Moulding Injection Phase|400px|right|link=https://commons.wikimedia.org/wiki/File:Plastic_Injection_Moulding_Injection_Phase.gif]]
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=====Description=====

Although there are ways of modelling almost all methods of moulding plastics in schools ''(e.g. '''[[Injection Moulding]]''' and small '''[[Injection Moulding|Injection Moulders]]''' for example are available)'', most working with plastics in '''[[Design and Technology]]''' involves '''[[Thermoforming Plastics|Thermoforming]]''' ''(i.e. forming of heated flat sheets of plastics)''.


The processes listed below generally involve much more expensive plant than is normally only available in industry.


=====Injection Moulding=====

'''[[Injection Moulding]]''' is the most commonly used manufacturing process for the production of a great variety plastics products and components.
[[File:Principe moulage injection polymere.svg|300px|right]]


In industry, plastics granules are drawn into an [https://en.wikipedia.org/wiki/Injection_molding_machine '''Injection Moulder'''] cylinder, or barrel, via a rotating screw to a point where they are heated and melted. The screw then operates as a piston and forces the melted plastics into a mould to create the products as shown:

# Reciprocating screw;
# Hopper;
# Granules;
# Barrel;
# Heaters;
# Mould.

As a consequence, most injection moulded products can be identified by the presence of a small ''‘pip’'' or [https://en.wikipedia.org/wiki/Sprue_%28manufacturing%29 '''sprue'''] where the melted plastics entered the mould.


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=====Extrusion=====

[[File:Extruder section.jpg|400px|right|Extruder section]]
[https://en.wikipedia.org/wiki/Plastics_extrusion '''Extrusion'''].is an industrial process, usually continuous, which can be likened to squeezing toothpaste out of a tube. Small beads of a '''[[Plastics|Thermoplastics]]''' are fed into a hopper from which they feed into the barrel of the '''Extruder'''. 


The heated '''Extruder''' contains a rotating screw which forces the softening plastics through a '''Die''' at the end which produces the extruded profile.


The general process of '''Extrusion''' can also be used to produce aluminium sections for example, and can be a hot or cold process.for metals such as [https://en.wikipedia.org/wiki/Aluminium '''Aluminium''']


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=====Calendering=====

[[File:Inverted L Calender.png|250px|right]]
[http://www.appropedia.org/Polymer_calendering '''Calendering'''] is used to manufacture thin film or sheet in either plastics or paper - or both by laminating films together. The process takes heated and softened plastics and squeezes it through rollers until the required thickness is achieved. It has some superficlal similarities with that used in [https://en.wikipedia.org/wiki/Rolling_(metalworking) '''Steel Rolling Mills'''] and was developed originally for the production of rubber sheet.


'''Calendars''' exert immense pressure on the material which results in lower temperatures being needed. This make the process very suitable for materials which may be sensitive to heat damage and for materials such as [https://en.wikipedia.org/wiki/Polyvinyl_chloride '''PVC'''] for which there is some concern regarding fume emissions.


The last set of rollers determines the final thickness of sheet and can also impart a textured surface finish if required.


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=====Rotational Moulding=====

[[File:Rotational Molding Process.svg|300px|right]]
[https://en.wikipedia.org/wiki/Rotational_molding '''Rotational Moulding'''] is an industrial process in which a hollow mould is loaded with a measured amount of .'''[[Plastics|Thermoplastics]]''' then heated and rotated about two axes such that the plastics forms a coating around the inside of the mould.


Rotation continues throughout both the heating and cooling phases to avoid deformation of the finished product. This makes for a long cycle times but it is still a cost-effective and easy way to produce large hollow pieces such as storage tanks.


The moulds for 
[https://en.wikipedia.org/wiki/Rotational_molding '''Rotational Moulding'''] are either fabricated from welded sheet steel or cast and are significantly cheaper than some other types of mould.

  
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=====Compression Moulding=====

[[File:Compression molding.svg|300px|right]]
[https://en.wikipedia.org/wiki/Compression_molding '''Compression Moulding'''] is used to create products by placing a measured amount of '''[[Plastics|Thermoset Resin]]''' into a heated mould cavity then applying the top of the mould, or plug, with heat and pressure until the resin is cured.


[https://en.wikipedia.org/wiki/Compression_molding '''Compression Moulding'''] is  a high volume process at a lower cost than '''Injection Moulding''' but not as consistent, and it is difficult to control '''''flashing'''''. It is useful also however  for moulding '''''composite''''' products such as when [https://en.wikipedia.org/wiki/Fiberglass '''Fibreglass ''(GRP)'''''] reinforcement is needed.


{{Thermoforming Buyers Guide}}

[[Category:Skills and Processes]]
[[Category:Working Plastics]]