Why Is the Blown Film Bubble Unstable? | Causes & Troubleshooting

An unstable blown film bubble can cause thickness variation, poor film quality, winding problems, and production waste. In this video, we look at the main causes of blown film bubble instability and practical ways to troubleshoot the process. We cover melt temperature, cooling air, internal bubble pressure, die gap adjustment, uneven film thickness, polyethylene raw materials, extrusion conditions, and other factors that can affect bubble stability. One important point is that bubble instability is not always caused by cooling air alone. If the die gap is poorly adjusted, the melt can exit the die unevenly and the bubble may form off-center. This can also cause uneven cooling around the bubble and make stabilization more difficult. Materials such as LDPE, LLDPE, mLLDPE, MDPE and HDPE can behave differently during blown film extrusion, so material properties and processing conditions must be considered together. A good troubleshooting method is to change one process parameter at a time, allow the process to stabilize, and then observe the result. PolyFilm Lab shares practical knowledge from real polyethylene film production. #BlownFilm #FilmExtrusion #Polyethylene #PlasticFilm #Extrusion