Paper forming – Application of steam in the forming of fiber-based materials
The research project aims to enable the production of marketable packaging products made from paper by direct forming. Deep drawing is one possibility that unites high productivity with profitable flexibility in forming paper. It has already been shown that the application of steam during the deep drawing process can lead to better shape stability, firmer wrinkle compression and enables higher drawing depths. One of the particular challenges when working with paper is the material anisotropy that occurs due to the manufacturing process. The anisotropy causes, among other things, a varying springback depending on the fiber direction. The targeted use of steam allows to reduce different effects of anisotropy.
In the video below, you can watch the motivation as well as the beginnings of the research project at PtU.
Industry, politics as well as society demand a growing usage of sustainable packaging. The high consumption of plastics in packaging cannot withstand the public debate asking to reduce plastic waste. That is why the request for paper packaging increases permanently. Two well-known manufacturing processes for paper packaging are folding and fiber casting, yet both cannot meet the high optical and economical requirements. On the one hand, folded paper packaging provides only very limited geometries and cannot be designed with freeform surfaces. On the other hand, casted fiber packaging is very expensive due to a complicated tool manufacturing and produces mere rough surface structures. In contrast, the production of deep drawn paper packaging provides a cost- and time-efficient production alternative that includes flexible and complex geometries like freeform surfaces.
The two-year project started with the collection and analysis of data to better predict the formability of different paper grades. An FE model was developed from this data and compared with data from experimental investigations of steam injection in a specially designed tool. The steam is introduced into the sample through the blank holder, whose modularity allows experimentation with different geometries (see Fig. 1). The process is to be further optimized by numerical simulation and adjustment of the control system in order to then realize the single-stage forming. Subsequently, the two-stage deep drawing process will be designed and carried out in the same way. At the end of the project, the findings will be compiled in guidelines.
Initial results already show that the optimum steam injection geometry is not only shape-dependent but also material-dependent. The results are at their best when the papers already have an increased moisture content of 10 – 15 % to begin with and steam is additionally introduced during the forming process. This is shown to be the same for all investigated papers. The tests also include papers with a unilateral PET layer. These show particularly clearly that the increased moisture before the tests is important, since the steam does not allow homogenized moisture distribution of the samples in the short time.
The IGF project 21562N of the research association “Kuratorium für Forschung und Technik der Zellstoff- und Papierindustrie im VDP e.V.” (Board of Trustees for Research and Technology of the Pulp and Paper Industry in the VDP e.V.) was funded by the Federal Ministry for Economic Affairs and Climate Action via the AiF within the framework of the program for the promotion of joint industrial research and development (IGF) on the basis of a resolution of the German Bundestag. We would also like to thank the project partners from industry for their support.