JPH0569697B

PURPOSE:To offer the thickness controlling die which is capable of corresponding to requirement of high thickness accuracy by improving a response time and adjusting accuracy, by a method wherein a lip adjusting mechanism possesses constitution to be obtained by making use of a piezo-electric element whose length is varied according to voltage. CONSTITUTION:Thermoplastic resin molten by an extruder 1 is entered into a die 2 through a duct 25 and extruded through a lip. The extruded resin 26 in molten state is cooled and cured by a cooling device such as a cooling roll 3 and turned into a film and a sheet 27. As for the film and the sheet 27, thickness of the same in the direction of web is measured by either a beta-ray thickness gauge or an infrared ray thickness gauge 28, which is treated operationally by a computor 29, voltage for a part wherein the thickness is thicker is increased, a flexible lip 17 is made to deform by lengthening a length of a piezo-electric element 18 and the thickness of the film is thinned by making a quantity of the resin, to be extruded by making a gap of the lip part small, reduce. As for a part wherein thickness is thin, the voltage is reduced on the contrary. The film and the sheet are made finally into ones having uniform thickness by repeating the above action.