1. Feeder Gob weight too high   1. Feeder Reduce gob weight   2. Machine Setup and Operation Plunger too late in loading position allowing glass to flow between plunger and neck ring Dirty thimble or guide ring preventing plunger from making complete stroke Plunger mechanism is set too low (blow and blow) Plunger loading screw too long (press and blow) Dirt on top of plunger cylinder Glass under invert barrel at the stop blocks   2. Machine Setup and Operation Correct timing between feeder and machine for correct loading position Change thimble, guide ring and neck ring Adjust plunger mechanism height Use correct loading screw length Clean the top of the plunger cylinder   3. Mold Equipment Plunger diameter is too small Plunger body too short (press and blow) Parison volume too small Plunger match with neck ring too loose 3. Mold Equipment Check for correct clearance between plunger and guide ring Check for correct design of plunger Redesign parison