Method of controlling the film thickness at a blown film installation

• Main Authors: KLINGE; GERD, WINKLER; GERHARD, UPMEIER; HARTMUT
• Format: Patent
• Language: English
• Published: 07.08.1984
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; CONTROLLING; PERFORMING OPERATIONS; PHYSICS; REGULATING; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

A nozzle ring of an extruder for blowing tubular plastics film is divided into cooling sectors provided with adjusting elements. The thicknesses of the blown film are measured over the circumference thereof and a number of film sectors of equal circumferential length corresponding to the number of cooling sectors is established from the measured thicknesses. Assuming that the film sector of maximum or minimum thickness has been extruded in the correct position for the purpose of determining the cooling sector associated with the film sector, the subsequent film sectors are in turn allocated to successive cooling sectors. From the measurements, the mean thickness distributions are determined over the individual film sectors. These values of mean thickness distribution define a measure for the correcting command for the adjusting elements of the cooling sectors that are associated with the respective film sectors.