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PLASTIC FORMING TECHNIQUES - Coggle Diagram
PLASTIC FORMING TECHNIQUES
Extrusion
Overview
The process comprises the forcing of molten material
through a shaped die by means of pressure.
For example: Melting of plastic resin + adding mixing fillers.
It is an important process to produce tubes, sheets, and film too complicated profiles.
In this process, screws are used to progress the polymer in the molten or rubbery state along the barrel of the machine.
Method
The materials fed into a hopper falls through a hole in the hole in the top the extruder (feed throat) onto the screw
The screw moves the molten plastic forward until the end of the extruder barrel to which die has been attached.
Then the die gives shape to molten plastics, then cooled in water tanks.
Injection Molding
Overview
The injected molten polymer into a closed mold where it is solidifies to give the product
The molding is recovered by opening the mold to release it.
Method
The mold is closed when a short of the melt is ready in the injection unit.
The injection occurs when the valve opens and the screw acting as a plunger forces the melt through the nozzle into the mold.
The valves close and screw relation starts.
The molding in the mold has continued to cool when ready the press and the mold opens and the molding is closed.
Compression Molding
Overview
- The process employs thermosetting resins in a partially cured atage in the form of granules, putty-like masses or preforms.
Method
The mold is held between the heated platens of the hydraulic press.
A prepared quantity of molding compound is placed in the mold.
The platen closes with the sufficient pressure to minimize flash at mold parts line.
The compound softens and flows to shape, chemical temperatures become high enough.
Next, the press is opened and the molding removed.
Transfer Molding
Overview
The development of the compression molding in which the reservoir of the molding compound is located in the mold and upon closure is transferred via runner to cavities.
It is used to give many small parts easily, to reduce the risk of damage or movement of thin or delicate mold parts and it is claimed to be faster due to better heat transfer through runners.
Blow Molding
Overview
The plastic formation process-manufacture of bottles and hollow-shaped parts.
The processes that utilize air to shape softened polymer tubes.
The three types of blow molding are Extrusion Blow Molding, Injection Blow Molding, and Stretch Blow Molding.
Method
The resin melting process is done in the extruder.
It will form the molten resin into a cylinder or tube. This tube is called a parison.
The parison is placed inside a mold and inflated so that the plastic is pushed outward against the cavity wall.
The part is allowed to cool in the mold and is then ejected. Then the part is trimmed.
Rotational Molding
Overview
It is used principally for the thermoplastic polymers, but can also be used for thermosets and elastomers which is common now.
It is an alternative to blow molding for making shapes.
To favor more complex external geometries, larger parts, and lower production quantities than blow molding.
Method
The pre-determined amount of polymer powder is loaded into the cavity of a split mold.
The mold is then heated and simultaneously rotated on two perpendicular axes.
While still rotating, the mold is cooled so that the plastics skin solidifies.
The mold is opened and the part is unloaded. The rotational speeds used in the process and slow it to cause the uniform coating of the mold surfaces.
Thermoforming
Overview
The thermoforming is the process of reshaping of plastics under the influence of heat and pressure or vacuum.
The use of compressed air and/or vacuum has become the preferred method for reshaping the thermoplastics.
Thermoforming is a manufacturing process for
Utilize a thermoplastic sheet or film.
Used on a large scale for the manufacture of packaging.
For the large parts such as swimming pool or motor vehicle parts.
It differs from the other plastics processing because the material is not melted, lower pressure is required for thermoforming.
Method
First, heat a thermoplastic sheet until it softens.
Force the hot and pliable material against the contours of a mold by using either mechanical, air, or vacuum pressure.
Held against the mold and allow to cool, and plastics will retain its shapes.
Filament Winding
Overview
The process to produce a hollow shape is usually in a cylindrical shape.
The fibers may be impregnated with resin before winding and pre-impregnated.
For example The end product such as pressure vessel, storage tanks.
Method
The fibers are passed through the resin bath.
Then, continuously wound onto the mandrel.
After the number of layers, curing is carried out in an oven or room temperature.
Then, the mandrel is removed.
Pultrusion
Overview
It used to manufacture components with continuous length and constant cross-sectional shape.
It is a continuous process and also easily automated, variety of shape
Method
The continuous rovings of the reinforcement are impregnated with the resins.
Then, pulled through the treated die.
The curing takes place in the heated die and oven.
The puller is used to pull the whole system with a certain speed.
Calendaring
Overview
The machine equipped with two, three, or more - heavy internally heated or cooled rollers and the rollers rotate in opposite direction.
It is used for skin coating of fabrics and laminating film.
It is used essentially for producing rubber sheets of various lengths and thickness.
Method
In this process, the extrudate is extruded directly into the nip area between two rolls.
The rollers have a small gap between them and plastics is forced through the gaps by the counter-rotating of the rollers between two rolls.
Blown Film Extrusion
Overview
The processes that utillize air to shape a softened polymer tubes.
To produce relatively thin film and bag.
No mold is required.
Method
The extruded materials flow through a tubular die.
The melt flows around a mandrel and exist the die as a tube.
A cooling ring is placed at the exit of the die to give the tube some dimensional stability.
The air is introduced through the back of the die and flows upwards inside the middle of the tube of materials.
The tube or bubbles, continues to expand, cool and crystallize until the radial (tensile) strength of the plastics equals the pressure of the air inside.
The bubble is then forced into a flat sheet by the collapsing guides, and moved into the nips rolls.
Then it travels down over some rollers and it was sealed.
