Gas traps result when the air inside a part forming cavity has nowhere to escape as the molten polymer fills the cavity. The trapped air can create both cosmetic and mechanical flaws in the molded part. Compression of the trapped air by the high pressure of the injection process can cause a significant temperature rise that can easily burn the surrounding polymer and even damage the mold steel. Gas traps can generally be avoided by proper gate positioning, allowing the air to exist through vents along the parting line of the mold. If venting along the normal parting line is not possible, vacuum venting or special internal cavity venting may be attempted.
