Hosokawa Alpine: Recognising and Reproducing an Optimum Bubble Shape

Hosokawa Alpine has developed a solution for identifying and reproducing an optimum bubble geometry in blown film production. This is made possible by a permanently installed camera that photographs the bubble every 0.5 seconds. Once the optimum bubble geometry for a given application has been achieved, the settings are saved with the corresponding film recipe. "The desired bubble contour can then be automatically called up again any time once it has been saved for the first time," explains Bernd Bayer, Director R&D Blown Film Extrusion at Hosokawa Alpine.

Critical bubble formation zone is precisely monitored

A permanently installed camera photographs the bubble every 0.5 seconds and recognises when the optimum bubble contour for the respective application has been reached

After exiting the die head, the material changes from a melted state to a solid state in what is known as the bubble formation zone. At this critical point, the bubble contour must be monitored precisely whenever the operating point is changed. Minor deviations at this point have a direct effect on the quality and properties of the film. "Previously, the width of the bubble was measured and regulated above the bubble formation zone," explains Bayer. With Alpine's bubble contour detection, it is now also possible to make statements about necessary cooling ring adjustments, such as height positioning and air lip setting.

Translation of the bubble contour into a mathematical formula

Technically, bubble contour detection works as follows: the contour of the film bubble is converted into a mathematical formula and a mask is created. Measurements of the behaviour of the film bubble under various control conditions are collected in a database so that conclusions can be drawn for the ideal contour of the film bubble. It can be easily imagined that this is of great value to the operator to ensure an optimum product quality.

Reproducible adjustment for maximum productivity

With bubble contour detection, Hosokawa Alpine enables customers to take a further step towards automating their blown film lies - both when changing the product and when restarting production. To ensure that the operating point can be set perfectly, the bubble contour parameters can be set reproducibly at any time. This allows the operator to quickly and easily reach the optimum production point and achieve maximum productivity. "Last but not least, customers benefit from software updates for further developments without any additional investment in hardware," concludes Bayer.