In many labs the quality of the film is checked by cutting and measuring circular areas. The measured values of the circular areas from a sample must not exceed a specified tolerance band. The new function Sheet Weight, which is now included in the Filmtest 3G Software Quality Analyzer, calculates these values graphimetrically according to ISO standard 4591.
This film sample has a length of 920mm and a thickness of 32µm. The software calculates with the selected settings the following measuring values for 8 circular areas:
The number of circular areas can be specified according to the sample length, or the software automatically determines as many circular areas as possible from the respective film sample.
The harmonic analysis can help to identify problems in the extrusion process. The following graph shows a thickness profile measured with the Filmtest 3G and analyzed with the Profile Genius feature:
This chart shows clearly that the biggest disturbance in the profile is the first harmonic, represented by the purple graph. The profile tolerances could be significantly reduced by centering the die.
This example shows a large influence of the 6th harmonic. Possible reasons could be: an air ring that does not distribute the air evenly, or a calibration cage that pushes too much into the bubble.
created with
Nicepage .