Concerns about carbon footprints and the increased cost of raw materials have made gauge variation in film blowing a hot topic.

Less gauge variation and changeover time translates into more raw material savings (RMS).Automatic gauge controls are assumed to have the largest effect on RMS. However, tests have shown that there can be considerable differences in performance—ranging from 4-12% RMS—among various automatic gauge controls.

The same tests showed a direct relationship between the number of control zones and the resolution (Resolution = 360 degrees divided by the number of control zones).

Manually adjustable (MA) air rings and special die designs have a lesser effect on RMS, between 2% and 3% RMS with the MA air ring depending on the operators’ willingness to make adjustments. Changeover times are reduced with internal bubble cooling (IBC) controls and range from 1-12% RMS. The best results are given by 100% digital IBC controls equipped with software that can foresee any possible variation in bubble shape, in conjunction with a high speed valve.

Other, lesser RMS contributors are continuous gravimetric blenders (as opposed to gravimetric batch blenders) tied in with the extruders’ screw and the line’s take-off speeds as well as vector drives on the primary nip rolls.