Utilization of Production-scale Machine in Experimental Fiber Material Convertibility Testing Using a Novel Press-forming Tool Set

Abstract

The convertibility of paperboard in a press-forming process was studied using a novel type of tool set that allows forming of small substrates such as laboratory handsheets (i.e. experimental materials) to investigate the role of mold design on substrate-press-tool interaction. The tool set makes it possible to prepare rectangular trays in both sliding and fixed blank modes in a pilot-scale press-forming machine. The tests showed that the fixed-blank mode makes it possible to estimate the elongation of the substrate in the forming process by determining the maximum forming depth for rupture-free samples. A more detailed inspection with an optical microscope of grid-patterned materials revealed that elongation took place mostly on the rim area in addition to the tray wall, and that the outer dimensions of the blank remained practically unchanged. The behavior of the material in press forming process was evaluated in addition to the novel tool set in a bigger, production-scale mold, and results showed good agreement between the small tool set and the standard mold, in spite of the dimensional differences. The smaller size of the mold did not require a compromise in any aspect of the press-forming process.

Influence of pulp type on the three-dimensional thermomechanical convertibility of paperboard

“…The experiments were carried out in fixedblank mode, which made it possible to determine the 3D material elongation based on the maximum forming depth without ruptures. The press-forming method and the elongation calculation are described in detail elsewhere (Tanninen et al 2017b). The experiments were carried out at female tool temperature of 80°C.…”

“…Ö stlund et al (2011) reported that the strain-at-break values of commercial paperboards vary within the range 1.1-4.2%, but according to Tanninen et al (2017a), a complex multilayered structure with several fiber and polymer layers may result in higher extensibility. Tanninen et al (2017b) found that a paperboard with a machine-directional strain-at-break value of 1.7% (RH 50%) had an elongation of approximately 6% (RH 80%) in press-forming. It was suggested that the observed difference was due to higher sample moisture content, different velocity during straining, and a different length-to-width ratio of the sample.…”

The effects of pretreatment and coating on the formability of extrusion‐coated multilayer paperboard–plastic composites

“…Similar to the approaches in Tanninen et al, 27 forming tests on an industrial forming machine were performed to transfer the material characterisation from laboratory scale to industrial processes and show the effect of different treatments in industrial applications. For these tests, a press forming tool set with rectangular geometry was used (Figure 5).…”

Three-dimensional thermomechanical converting of CTMP substrates: effect of bio-based strengthening agents and new mineral filling concept

“…3D elongation of a material was determined to be the maximum forming depth without ruptures detected visually. The equipment and methods are described in more detail by Tanninen et al (2017b). The 3D elongation is given as the average of the measured elongation at the two temperatures, as the 3D elongation rarely differed between the different temperatures.…”

“…In the Mini-Mould system used, the 3D elongation indicated by the maximum depth without rupture is known to correspond to the 3D elongation defined based on the surface area increase of the elongating part of the substrate during forming. A more detailed description of the 3D elongation is given by Tanninen et al (2017b).…”