Blow molding

1. Blow molding
By Sunil Mor

2. Principle
• Blow of air into a plastic tube that is closed on all sides except
the point at which the air enters, the tube will expand and
take the shape of the mold that is around the tube.

3. Working
• A hot, softened plastic material tube known as parison is
properly placed inside a two plate cavity mold.
• When the two part of the mold are closed, it pinches and
closes one end of the parison and encloses a blowing pin at
the other end.
• Now, the parsion is blown by pressuring from within by
blowing compressed air through the blowing pin.
• The hot parison is inflated like a balloon and goes on
expanding until it comes in intimate contact with the
relatively cold interior surface of the cavity mold.

4. Working
• Under pressure, the parison is ultimately assumes the shape
of the cavity of the mold.
• The mold is allowed to cool and the article formed is removed
by opening the mold.
• https://youtu.be/QCuIUy7r6Ik

5. Working

6. Example
• Bottles, containers, jerry cans, etc.

7. References
• Plastic engineering handbook by Joel Frados.
• Polymer extrusion by hanser publication.
• Polymer processing by DH Morton Jones.
• Hand book of plastic technology by W.S. Allen/ P.N. Baker.
• SPI Plastics Engineering Handbook by Michael L. Berins.
• SBP Handbook of Plastics.