Machinery News

Venting system for blow moulds

As the mould closes around the parison and is inflated and pressed to the cavity wall by air blown into it, air is trapped between the parison and the two mould halves. This trapped air must be removed. In order to expedite this venting process, conventional moulds are often equipped with vents at the parting line for expelling any trapped air, sometimes with the help of vacuum. The downside of this method is the fact that air can only be removed locally and the introduction of a vacuum leaves small marks on the finished part.

The firm's new solution is used in the extrusion mould for a 20 litre jerry can and is now vented in all four corners of the mould with vacuum used to increase the ventilation effect. The vent is cut across the entire height of the mould corner so as to eliminate the occurrence of marks on the finished part. This way, trapped air can be removed quickly and effectively.