Profile production in multi-veneer sheets by continuous roll forming

Abstract

Roll forming is a rapid operation that employs consecutive roll stations to progressively deform a strip into a desired profile. The continuous nature of the process coupled with its versatility and speed makes it extremely attractive for producing lightweight, structurally efficient components from sheet materials. This paper describes the roll forming of plywood by heated rolls, which is an innovative concept that can increase the range of usage and add value to the end products. Deformation length measurements from static roll bend tests were carried out to determine the roll spacing and the results agree well with the values predicted by a modified theory based on the minimisation of the total deformation energy for a rigid-plastic material. The deformation lengths, such as in metals and composite sheets, depend essentially on the geometric parameters of the profiles produced and are practically independent of the mechanical properties of the work material. Further, the real-time strain measurements by strain gauges bonded on the roll formed specimens show that the strain profiles compare reasonably well with those obtained for metallic and continuous fibre-reinforced thermoplastic sheets. Finally, the macroscopic deformation of veneer sheets due to roll forming has been analysed kinematically by means of grid strain analysis and the geometric conformance of the product has been determined.