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FORMING METHODS FOR POLYMER - Coggle Diagram
FORMING METHODS FOR POLYMER
Simple Working Principles of The Forming Method
Determine the materials whether it is thermoset or thermoplastic.
If thermoplastics; the temperature at which it softens.
The atmospheric stability of the materials being formed.
Geometry and size of the finished products.
3. Compression Molding
Common working principle
;
The mould is held between the heated platens of the hydraulic press.
A prepared quantity of molding compound is placed in the mould.
The platen closes with sufficient pressure to minimize flash at mould parts line.
The compounds softens and flows to shape, chemical cure then occurs as the internal mould temperature becomes high enough.
The press is opened and the molding removed.
Type of products;
Granules
Putty-like masses
Preforms
1. Calendering
A machine equipped with two, three or more heavy internal heated heated or cooled rollers which usually placed above each other.
Common steps;
The rollers rotate in opposite directions.
Operate at even/uneven speeds based on applications requires.
Produce
rubber sheets of various lengths and thickness.
Type of products;
Skin coating of fabrics
Curtains
Tablecloths
Laminating film
2. Extrusion
Type of products;
Tubes
Sheet and film
Structural parts
Steps
;
Materials fed into hopper, falls through a 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.
Die gives shape to molten plastics.
Cooled in water tank.
Continuous semi-finished product with uniform cross section.
7. Blow Molding
Manufacture of
bottles and hollow-shaped parts.
Common steps;
The tube called parison is either extruded or injection molded and is then clamped in a split mold with a blow pin inside.
Air inflates the polymers until it conforms to the shape of the mold.
The polymer cools on contact with cold mold walls.
The mold is then open and the part is ejected
Consists 3 types;
Extrusion blow molding
Injection blow molding
Stretch blow molding
10.Filament Winding
Process to produce
a hollow (usually cylindrical) shape
.
Products
;
Pressure vessel
Storage tanks
Aerospace parts such as helicopter blades.
Steps;
The fibers are passed through the resin bath.
Then continuously wound onto the mandrel.
After number of layers, curing is carried out in an oven or room temperature.
Mandrel is removed.
4. Transfer Molding
Producing many
small parts.
Development of compression molding in which reservoir of the molding compound is located in the mold and upon closure is transferred via runner to the cavities.
6. Blown Film Extrusion
Produce relatively
thin film and bag.
Common steps;
A continuous tube is extruded clamped between rollers at one end and blown with compressed air to form large hollow tube having a very thin wall.
The tube continuously flattened and placed on a roll for bag production or it can split opened and used for film.
8. Rotational Molding
Steps
;
A predetermined 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, so that the powder impinges on all internal surfaces of the mold, gradually forming a fused layer of uniform thickness.
While still rotating, the mold is cooled so that the plastic skin solidifies.
The mold is opened, and the part is unloaded. Rotational speeds used in the process are relatively slow. It is gravity, not centrifugal force, that causes uniform coating of the mold surfaces.
11.Pultrusion
Manufacture components with continuous
lengths and constants cross-sectional shape.
Products
;
Rod
Tubes
Beam
Steps
;
Continuous rovings of the reinforcement are impregnated with the resins (passing through a bath of resin).
Then pulled through the heated die (compact & give shape to the composites).
Curing takes place in the heated die & oven.
Puller used to pull the whole system with certain speed. (Pultrusion - pulling action)
5. Injection Molding
Common working principles;
Inject 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.
9. Thermoforming
Manufacturing process for;
Utilize thermoplastic sheet or film.
Used on large scale for the manufacture of packaging.
For large parts such as swimming pool or motor vehicle parts.
Common working principles;
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 mold and allow to cool, and plastics retains its shape.
Reshaping of plastics under
the influence of heat and pressure or vacuum.