The position of the gas needle (or pin) is critical to the gas-assist process. The gas needle should penetrate the cavity from 1/3 to 1/2 of the gas channel thickness, unless a boss configuration is utilized. The plastic must seal around the gas needle prior to gas injection, or the gas will leak between the part and the cavity wall, through the vent to atmosphere. This will not only cause quality problems, but will be a waste of the nitrogen gas. The gas needle should be removable from the face of the mold, in order to avoid dismantling the mold, if a gas needles plugs. The diameter of the gas needle and the size of the supply hose are also a concern. They affect the volume of gas entering the gas channel and the response time of the gas injection. Below are examples of some gas injection pins.