If air trapped inside the cavity or gases released by the plastic cannot escape during the filling process, defects such as bubbles, burn marks (caused by high-temperature compressed air igniting the plastic), or short shots (incomplete filling) may occur. Venting systems typically consist of narrow channels located at the point where the cavity fills last:
Dimensional parameters: Depth of 0.01–0.03 mm (adjusted based on plastic fluidity; lower values are used for resins with high fluidity to prevent flash) and width of 5–10 mm;
Special designs: For complex cavities, venting inserts (with a 0.01 mm gap) may be added to ensure smooth gas evacuation; for instance, corners in automotive bumper molds often require multiple venting channels working in conjunction.