Production of blisters

Blisters are produced using a process named vacuum forming or thermoforming.

A plastic film or sheet is unwound from the reel and guided though a pre-heating station on the thermoforming machine. The temperature of the pre-heating plates (upper and lower plates) is such that the plastic will soften and become formable. The warm plastic will then arrive in a forming station where a large pressure or vacuum (4 to 8 bar) will form the blister cavity into a negative or onto a positive mould. The mould is cooled such that the plastic becomes rigid again and maintains its shape when removed from the mould. In case of difficult shapes, the warm film will be physically pushed down partially into the cavity by a “plug-assist” feature.