Three real-world case studies show how processors solved common problems in blown film via the mapping technique. In blown film, bubble management is essential to achieve consistent film quality, physical properties and successful winding. When diagnosing winding or quality defects, the bubble “speaks.” Reflect on a time when your blown-film line was new or newly upgraded, or had just gone through a complete preventive-maintenance program. The line is clean, calibrated and aligned. It starts up, and the process team has it tuned and running the best product ever. The bubble is perfect. It is a “happy bubble,” locked into the air ring and with the frost line at the perfect height; level, straight, no dips, no spikes and no bubble flares. Perfect. Burn that image into your mind. From that image, the discerning eye will easily spot an “unhappy bubble” from across the factory to diagnose quality defects. The intent of this article is not to enumerate every defect and every known cause. It is to demonstrate how mapping can be used to properly define a defect and narrow down, as quickly as possible, the list of suspects causing the issue. When addressing blown-film quality defects, i...