Pressing

Pressing is used for widened containers (plates, cups and glasses) and also for producing thicker cross-sections for automotive lenses. The gob of molten glass is loaded in a mould, the plunger is lowered and forces the glass to spread and fill the mould. Pressing can be performed with free sides (without a ring) when dimension tolerance is acceptable. The size of the plate or glass is then determined by the parison temperature and the pressing force. Patterns on the mould surface allow for imprinting the glass object and make it look more attractive and more expensive than it is.

For more dimensional control, the mould is closed by a ring allowing for production of automotive headlight lenses with high-precision shape. An automatic machine comprises 6 to 16 different moulds allowingfor high production yield.

Fibre Process

Glass fibre production tools are very different when considering optical fibres, rovings or glass wool. Processes differ in the way drawing force is applied and three drawing modes are distinguished: tensile drawing, gas friction drawing, and centrifugal drawing.

Nowadays, processes employ either tensile or centrifugal drawing gas friction being combined with centrifugal drawing.

(Fibre drawing process)