Definition
A manufacturing process used to form hollow plastic parts. A heated tube of softened thermoplastic material, called a parison, is placed inside a mold. Compressed air is then blown into the parison, expanding it outward against the inner walls of the mold. The plastic cools and hardens in the shape of the mold cavity, producing a one-piece hollow part.
Plain English
A way of making hollow plastic parts by blowing air into a soft plastic tube inside a mold so the plastic puffs out and takes the shape of the mold.
Context Anchor
Seen in aircraft maintenance and materials discussions for hollow plastic parts such as reservoirs, bottles, ducts, or covers.
Derivation
Named directly for the process: a mold is used, and air is blown into the plastic to shape it. The term describes what physically happens during manufacture.
Why Pilots Care
A pilot or mechanic may see this term in parts descriptions or maintenance information. It helps explain why a plastic aircraft part is hollow, lightweight, and shaped as one piece.
Analogy
Similar to how a glassblower inflates molten glass inside a form to shape a bottle, except the material is hot plastic and the shape is set by a mold rather than by hand.
Intuition Check
Blow molding is not an airflow effect in flight. Here, “blow” means using air pressure to shape softened plastic during manufacturing.
Example Sentence 1
The hydraulic fluid reservoir was produced by blow molding, giving it a seamless one-piece body.
Example Sentence 2
Replacement fluid reservoirs on the aircraft were made by blow molding for consistent wall thickness.