method for controlling thickness of the extrusion (manufacture), long articles made of thermoplastic materials, such as films, tubes, pipes, cable sheathing, plates, profiles and measurements and device for extruder, extruding od. etc. for elongated objects

摘要

The invention relates to a process for producing elongated objects from thermoplastics having constant lateral profile, for example films, tubes or the like, by extrusion or extrusion pressing. In the process the weight per metre (kp/m) is determined from the weight of the thermoplastics fed especially in individual charges to the extruder or the extrusion press and from the length of the object produced. The average absolute thickness of the object, calculated taking into account the width, is compared with the average, relative thickness of the object, which is determined from several measurements of the thickness taken over the width of the object. The error calculated from this comparison is used as a correction factor for determining the absolute value for the thickness of the thinnest point. The thickness control of the object in the longitudinal direction is carried out after the thickness profile with the absolute value of the thickness for the thinnest point has been shifted to the lower permissible tolerance limit. With a measurement and control process of this kind it is possible to produce an area unit of the object with a minimum of material consumption whilst complying with the lower permissible tolerance limit, without measurement devices matched to the respective material being required.