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 the 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 depth. 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 different springback depending on the fiber direction. The targeted use of steam allows to reduce different effects of anisotropy.

Motivation

Industry, politics as well as society demand a growing usage of sustainable packaging. The high usage 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 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.

Aim

The objective of the research project is the local application of steam to critical zones of non-rotationally symmetric deep drawn packaging products during the manufacturing process and thereby obtaining a higher drawing depth. Packagings as shown on the left side in figure 1 shall be replaced by paper packagings like the one in the middle. The packaging shown on the right displays a paper deep drawn in two stages to enlarge the maximum packaging volume.

Figure 1: Left: to be substituted plastic packaging; middle: deep drawn paper packaging; right: paper packaging deep drawn in two stages

Approach

The two-year project begins by collecting data and analyzing it to better predict the formability of different paper types. Thereupon, the development of an FE model follows to compare the FE data with experimental data of the steam usage whilst deep drawing. The process will be further optimized by numerical simulation and adjustment of the control system in order to then realize single-stage forming in a specially developed deep drawing tool. The blank holder of the deep drawing tool is used to direct the steam into the paper (figure 2). Different geometries of the steam injection can be tested due to the modular construction of the blank holder. Later on a second deep drawing stage is to be implemented, to enlarge the volume of the product. The project will be completed by deriving guidelines for the processes of deep drawing of paper from the new research insights.

Figure 2: Steam injection through the blank holder of the deep drawing tool

Acknowledgements

This research project is funded by the AiF within the support program “industrielle Gemeinschaftsforschung” (iGF) by the Federal Ministry of Economic Affairs and Energy (BMWi). Thanks are also directed to the industrial partners promoting the research proposal as part of the committee accompanying the project.