Air valves are fitted to mould tools to aid component ejection. A small burst of air is blown into the mould cavity to break the vacuum created when moulding deep draw parts for example containers, buckets or thin walled moulded parts.
Sometimes these air vents can stick, and then fill with plastics during the injection cycle, resulting in expensive downtime whilst the mould tool and valves are stripped down and cleaned.
The Italian mould components company Ermanno Balzi are aware of this problem and have developed a safe closing valve that can take the place of conventional conical type valves.
1) In the ejection phase the Balzi VABA air valve introduces air into the mould cavity. First in limited quantity through the space between the valve body and the convex poppet, then in larger quantity via the internal bleeds.
2) In the closure phase of the moulding process, If the valve was to jam forward or solenoid malfunction, the push of the matrix guarantees the first closing of the convex poppet that moves into an anti-filling position.
3) During the injection phase the plastic flows between the convex poppet and the matrix, bringing the convex poppet back to the correct position.
These air valves are available in the UK and Ireland through Ermanno Balzi distributor CyTec Systems UK Ltd.