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The increasing social demand for sustainable material use leads to new process strategies as well as to the use of new materials in nearly all industries. In light of this demand, paperboard shows potential to substitute polymer-based components while also exhibiting improved ecological properties. However, in contrast to polymer-based products, the forming limits of paperboard are relatively low. Therefore, three dimensional forming of paperboard is subject of current research. One area of research focuses on the control of the fiber orientation dependent anisotropic material behavior of industrial paperboard in forming processes. For an examined industrial paperboard, an average elongation at break of 1.2 % in the so called machine direction (fiber preferential direction, MD) has been determined at standard climate conditions. In contrast, in cross-direction (orthogonal to the machine direction, CD) a value of 2.6 % was observed. With increased moisture content of the specimens the difference between the mechanical properties in MD and CD even increases. As a result of the various fiber-orientation dependent mechanical properties, forming with symmetric tools leads to asymmetrically shaped final parts. Within this article, an approach to reduce the asymmetric shape of threedimensional formed paperboard by using single point incremental forming technology is presented. For a free spatial processing strategy the 3D Servo Press Technology, which enables circular as well as free processing strategies, is used. Based on reference tests with a circular processing strategy, it is shown that by using an adapted, elliptical tool path, an almost symmetric shaped part can be formed. [ABSTRACT FROM AUTHOR]

Single point incremental forming (SPIF) is a manufacturing process to produce complex shaped parts by the CNC controlled movement of a hemispherical forming tool. The poor geometrical accuracy is one of the dominant process limits in SPIF. Several references deal with approaches to improve the geometrical accuracy in SPIF, especially for sheet metal forming. However, forming thermoplastic materials with high geometrical accuracy is even more difficult due to the large elastic recovery upon unloading. As already shown for SPIF of metal sheets, overbending the workpiece is one opportunity to improve the geometrical accuracy. The aim of this research is to investigate how SPIF process parameters effect the resulting geometry and bulging of thermoplastic sheets. The research is done experimentally using Polyvinylchloride (PVC) and high density Polyethylene (PE-HD). It includes a strategy to reduce bulging effects by overbending the material. The experiments were performed on a CNC milling machine equipped with a single point forming tool and a simple support to fix the workpiece. To investigate the influence of the process parameters on the geometrical accuracy, linear grooves were manufactured into thermoplastic sheets. The geometric quality of the formed thermoplastic parts was evaluated by means of three-dimensional optical measurement. Tool radius, initial sheet thickness and workpiece material showed a strong correlation with the bulge height of the final part. Depending on the considered process parameter, the bulge height can be reduced up to 98%. [ABSTRACT FROM AUTHOR]

Incremental forming is an innovative sheet metal forming technology. It is a promising flexible and inexpensive method to form sheet products in small batches. One technique within this technology is single point incremental forming which allows producing complex shape using a computer numerical control machine. It is a new sheet metal forming process which achieves higher formability, greater process flexibility and reduced forming forces compared to conventional sheet forming operations due to its characteristic of localized deformation. In this paper, an experiment was conducted to study the effects of several parameters (tool diameter, feed rate, step size and sheet thickness) on forming forces to provide a better understanding of the process parameters leading to achieve a successful product. Experiments were performed based on a full factorial design of experiment technique. The formed sheets were made of AA1050-H14 aluminum alloy. [ABSTRACT FROM AUTHOR]