Copy of Rotational Molding

8/2/2019 Copy of Rotational Molding

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A SEMINAR ON ROTATIONAL

MOLDING


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What is Rotational Molding?

Is a Casting process used to

make hollow Plastic Products

Also called RotoMolding,

Spin Casting, Slush Casting


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Rotational molding is applied to a much wider

range of applications with an ever-increasingdegree of sophistication

Rotational molding also has few competitors forthe production of large (> 2 m3) hollow objects in

one piece Best known for tanks, but can be used for wide

range of medical products, toys, leisure craft, andhighly aesthetic point-of-sale products

Not Centrifugal Casting


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The Principle

Mold Charging

Mold Heating

Mold Cooling

Part Ejection


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Equipment and Tooling

They normally consist of

Molds

Oven

Cooling chamber Mold spindles

The spindles are mounted on a rotatingaxis, which provides a uniform coating of

the plastic inside each mold


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Rotational molding machines

They usually operate in 4 Stations.

Loading Heating Oven

Cooling Chamber

Unloading


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Rock n Roll Machine


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Carousel type machines


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Shuttle types machines


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Different Process Variables

A measured amount of powder or liquid plasticis introduced

rotational speeds being infinitely variable,usually ranging up to 50 rpm on the minoraxes and 12 rpm on the major axes

A 4:1 rotation ratio generally is used forsymmetrically shaped parts.

A wide variety of ratios are necessary formolding unusual and complex shapes

Cycle time range from 10-45 min


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Materials

PVC

Polycarbonate

Polyester

Nylon Polyethylene

ABS

Phenolic


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Agriculture: storage tanks, spraying equipment tanks

Automotive: interior panels, fuel tanks, ductwork, air-

intake systems, door armrests, wheel arches.

Buildingconstruction: water tanks, septic tanks, highway

barriers

Electricalelectronic: aboveground pedestals,

belowground chambers

Industrial: chemical tanks, cases, shrouds and housings,

control equipment parts


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Marine products: dock floats, hulls, fuel tanks,

seating, fenders, live wells

Material handling: tanks, drums, barrels, hoppers,

IBCs, pallets

Medical equipment: spine boards, anatomical figures,

inflatable masks, implants

Playground equipment: slides, climbing frames,

outdoor furniture

Sports and recreation: toys, kayaks, canoes, helmet

linings, pet products

Transportation: road traffic barriers, cones


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Advantages:1) Manufacturing large, hollow parts such as oil tanks

is much easier by rotational molding than any othermethod

2) Rotational molds are significantly cheaper than

other types of mold

3) Very little material is wasted using this process, and

excess material can often be re-used

4) Consistent wall thickness and strong outside

corners that are virtually stress free

5) Color changes can be made quickly and easily


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Disadvantages:1) Long cycle times-only one or two cycles an hour

can typically occur2) As it is a low pressure process, sometimes

designers face hard to reach areas in the mold

3) Entire mold must be cooled

4) Some plastics will degrade with the long heatingcycles or in the process of turning them into a

powder to be melted.

5) The number of materials that are available for

rotational molding is limited in comparison to

other processes

6) Material costs are higher, due to the need for

grinding pellets of raw material to a fine powder

for molding

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