I received this question today…
A co-worker told me voids are actually not filled with air or gas. Is this true? Could you explain what voids really are?
Your co-worker is correct. Voids are sections in the center of a part where material shrinks away from itself and leaves what appears like a small hole within the part.
Although they often appear to be air bubbles, they are actually vacuums within the part where no gas is present. An increase in packing or holding pressure usually corrects this.
Keep in mind, gas entrapment can often be confused with the presence of voids.