Rotational Molding

SUMMARY
Advantages:
Low tooling costs
Uniform wall thickness
Hollow parts or open-ended
Short lead times
Excellent durability and impact resistance
Disadvantages
Slow production cycle times
Heavy weight compared to other molding processes for the same application
Not suitable for small intricate parts
Some secondary work may be necessary
TYPICAL APPLICATIONS
Commercial containers and dunnage
Toys
Agricultural products
Automotive under hood applications and fuel tanks
Recreational products

Rotational molding is a forming process in which melted plastic is distributed over the inside surface of a rotating mold, resulting in a hollow enclosed or open-ended part. Several molds may be placed on a machine at the same time, lowering part cost. Pre-measured plastic resin is loaded into each mold, then the molds are moved into an oven where they are slowly rotated on both the vertical and horizontal axis. The melting resin adheres to the hot mold and coats every surface uniformly. The mold continues to rotate during the cooling process so the parts retain an even wall thickness. With proper part design, parts that are assembled from several pieces may be molded as one part, eliminating expensive secondary assembly costs. The uniform wall thickness, and very low molded in stress within the part itself, results in very durable parts useful for industrial applications. Due to the low molding stress within the mold, the molds are very inexpensive and may be produced with short lead times.

Compared to alternative plastic forming processes, rotational molding can be uneconomical. The wall thickness is uniform but may be unnecessarily thick for some applications; for these applications Blow Molding may be more appropriate. Small intricate parts are also not suited for rotational molding; injection molding would be more appropriate for these applications.

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