How is an Aluminium ROPP cap made?

ROPP closures are made from a flat sheet of aluminium which then goes into a punching machine to give it its shape. Depending on the length of the closure it could go through several punching machines to make a pre-form known as a shell? (The shell of the closure is then side printed if required). The shell is then taken to another machine to have all the details put on it. Then another machine will insert the liner.

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Closure characteristic

Retaining ring – this is at the top of the cap and is used to hold the liner inside the closure.

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Strengthening ring – this to ensure the shell remains in its correct shape between manufacture to application.

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Bridges – these are cuts into the side of the closures which break during the removal of the closure after application, this is the PP or pilfer proof part of the closure.

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Posted in: Aluminium ROPP FAQs