Method of press-forming corrugated paperboard as substrate of curved trim board
 In the production of a trim board such as an automobile roof trim board using a corrugated paperboard substrate which is bulged or dented in a comparatively small area and has an aperture in this area for the installation of a separate article, at least one linear notch is formed in a flat board of corrugated paperboard so as to extend transversal to the ridges of the corrugated medium and be entirely included in the area of the aperture as a preparatory procedure to press-forming of the corrugated paperboard. The presence of the notch allows some deformation of a tensioned liner also in the same direction as the ridges and hence precludes the appearance of cracks in the bulged or dented area. The notched region of the shaped board is thoroughly cut away as the result of the formation of the intended aperture. 
Nissan Motor Company, Ltd.
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Toshihiko
Fujii