Process comparison

Injection Molding vs Rotational Molding: Large Hollow Parts vs Production Detail

Rotational molding tumbles resin powder in a heated mold to make large hollow parts. Injection molding makes detailed parts fast from a hardened steel tool.

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Process choice

Big hollow shapes versus fast, detailed parts

Rotational molding wins on size and hollow volume. Molding wins on detail and cycle.

Rotational molding loads resin powder into a mold that heats and rotates on two axes, coating the inside until a hollow part forms. It suits tanks, bins, and large hollow housings.

NetProto does not offer rotational molding. This guide helps decide which parts of a program belong in an injection mold instead.

Side by side

How the processes differ

Part size, cycle, and material range usually decide.

Rotational molding (typical)

Very large hollow parts in one piece
Low-pressure tooling with lower investment
Long heating and cooling cycles and a narrower material range

Injection molding (NetProto)

Short cycles for repeating production
Wide range of engineering resins and fillers
Fine features, tight fits, and molded-in threads

Routing table

Which process fits the part

Qualitative only.

Signal	Rotational molding tends to fit	Injection molding tends to fit
Size	Larger than a molding press can hold	Fits a production press
Shape	Closed hollow body	Solid or open parts with detail
Volume	Low to moderate quantity	Repeating production orders
Material	Commodity polyethylene grades	Engineering resins and filled grades