JPS6490724A - Bending method of plastic substance - Google Patents

Abstract

PURPOSE:To enable the title substance to be bent at a sharp bent angle without causing deterioration in strength of the substance, by a method wherein simple bending of a sheet material is performed at the bend angle of 45 deg. or less along a bending line and the sheet material is bent centering around an inside point of the bending line while applying buckling stress to the sheet material by facing to a rotary center side from the bending line. CONSTITUTION:Plastic substance is of an uncured cement molded product forming mainly a sheetlike state or a plastic molded product which is in a softened state. A bending angle of the plastic substance where cracks are not generated is almost 45 deg. or less. When the title method is constituted so that tensile stress is not applied to a bent outer face, there is no fear of generating the cracks in making the bending angle close to 90 deg.. The plastic substance 3 is bent simply by making use of a top and bottom forces 1, 2 which have been made into a bent angle theta of 45 deg. or less and a product is bent by facing on in the direction of the center point P from a bending line 3A by making the point P, which is more inside than the bending line 3A, into the center point while applying buckling stress (arrow A). With this construction, buckling is apt to generate easily on the plastic substance and bending force does not act upon the outside of the bending part at all, therefore, bending in a state of an acute angle becomes possible without generating the cracks.