It is a method of shaping flat thermoplastic sheet which includes two stages. Softening the sheet by heating, followed by forming it in the mold cavity.
Elastomers and Thermosets cannot be formed by the Thermoforming methods because of their cross linked structure they do not soften when heated.
Thermoplastics that can be processed by the thermoforming technique are Polypropylene, Polystyrene, Polyvinyl Chloride, Low Density Polyethylene, High Density Polyethylene, Polymethyl methacrylate.
There are three thermoforming methods. These are
Vacuum Thermoforming
Pressure Thermoforming
Mechanical Thermoforming
VACUUM THERMOFORMING
The process involves shaping a preheated thermoplastic sheet by suggests that of vacuum made in the mold cavity space.
The atmospheric pressure forces the soft sheet to deform in conformity with the cavity shape.
Once the plastic comes into the contact with the mold surface it cools down and hardens.
PRESSURE THERMOFORMING
The process involves shaping a preheated thermoplastic sheet by suggest that of air pressure.
The air pressure forces the soft sheet to deform in conformity with the cavity shape.
Once the plastic comes into the contact with the mold surface it cools down and hardens.
MECHANICAL THERMOFORMING
The process involves shaping a preheated thermoplastic sheet by suggests that of a direct mechanical force.
A core plug forces the soft sheet to fill the space between the plug and therefore the negative mold.
The process provides precis dimensional tolerance and surface detailing.
APPLICATIONS :
It is widely used in the food packaging industry for manufacturing ice cream and margarine tubs, meat trays microwave containers, snack tubs, sandwich packs.
It is also used for manufacturing some pharmaceutical, small tools, fasteners, toys, boat hulls, blister and skin packs.
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