The company’s latest thin board line is designed to run at up to 120m per minute. In order to feed the right quality of fibre to the press at these speeds, Siempelkamp’s StarFormer has been modified, starting with the bin filling system. Fibre decelerating rollers have been installed between the double screw and the bin to achieve a low falling height and speed, to prevent clotting/compaction of the fibres, explained Mr Sebastian. "We have also minimised the distance between the discharge point of the bin and the forming head and reduced the spacing between the spreading rollers to achieve more accurate distribution," he said. At the same time, all oversize glue lumps are discharged, while smaller ones will be dealt with by the next innovation – the compacter.
The thin board line has a conventional textile belt pre-press but this is then followed by a second ‘pre-press’ which is the compacter. This has three tasks to perform: To further pre-press the fibre mat to the required density to suit the high-speed entry into the hot press; to further squeeze air from the mat; and to crush any glue or fibre lumps. When a normal mat needs to be rejected, such as when metal contamination is detected, a trash gate opens and the mat falls down to be taken away. However, when the mat is highly compacted, as in this new line, it would not simply break off when the gate was opened. Hence there is an extra cross-cut saw before the ContiRoll entrance. "This ensures proper mat separation and generates a well-defined front edge – another prerequisite for trouble-free mat transfer into the press at high line speed," said Mr Sebastian.
Key to the pressing of thin boards is the flexible infeed section of the press. "Siempelkamp invented the flexible infeed and it is unique in our presses," he said. "The upper platen is continuously flexible, not just in one or two ‘segments’ and the infeed can be adjusted to any requirement of the customer on every ContiRoll built for the last five years. It is a patented system. "The most important benefit of this system is in de-gassing the mat. It allows more progressive, smoother de-gassing, particularly when you have a fast-moving mat." New for the thin board line is the directly-heated large diameter infeed drum. "Thin board mats have to be heated very fast as they enter the press," explained Mr Sebastian. "The heating capacity of the infeed drum in this press is set accordingly. After that, the temperature has to be maintained to cure the resin."
The stainless steel press belts used are quite thick, at up to 3.5mm, to enable them to store heat to maintain the required pressing temperatures. "Boards of only 1mm thickness are very easily damaged by temperature and pressure variations and an even, homogeneous, surface is vital as they are often liquid- or thin-paper covered," explained Mr Sebastian. "Thus heat and pressure must be very evenly distributed. "This means the infeed drum is of a very special design and we also installed one extra row of cylinders in the press to ensure even pressure distribution across the belt, while in the longitudinal direction, pressure is distributed in an even curve." To assist in achieving this precision, firstly there is a thickness gauge at the press exit which controls the cylinders in the calibration section. This measuring device has several tracks across the press width – one for each pressure cylinder. Secondly there is an automatic density control system at the press infeed and press adjustments are made accordingly, automatically.
The first of these high-speed thin board lines was sold to Pfleiderer for its Grajewo, Poland, plant. The second was sold to Fantoni for its Lesonit plant in Slovenia and the third to SFC in Turkey. The latter two lines will be slightly different because they are required to produce from 1mm to 25mm boards. With respect to the closed-loop feedback control for the infeed adjustment, the ‘prototype’ press was installed at Egger’s Brilon plant in Germany, where an existing press was extensively modified. Apparently this was to Egger’s delight, which refers to it as its ‘autopilot line’. A second major new line concept for the Siempelkamp group is the lightweight, frameless, paper honeycomb-cored continuous panel production line developed by SHS (Siempelkamp Handling Systems). This line employs a continuous press originally developed by SHS for other markets, which is nothing like the ContiRoll, except that it is a double-belt press. But its role is more calibration than hard pressing and the ‘belts’ are made up of stainless steel sections, like a tank track, rather than a continuous belt like the ContiRoll.
The first line, running at Egger’s St Johann factory in Austria since September 1st this year, uses 3mm particleboard or MDF faces, although other panel types and thicknesses could be used. The complete sandwich panels are from 16 to 100mm thick. German machinery maker Homag developed the system to insert and laminate an edging in the frameless panels as a separate continuous process after the SHS press. Egger developed special jointing techniques between these panels. A third new Siempelkamp concept was the wood fibre insulation board line supplied to Gutex of Germany, which started production last February. These panels are made, crucially, in a dry process rather than the traditional wet process, and in thicknesses of 20 to 240mm. Such thick boards were previously only obtainable by gluing multiple boards together, said Mr Sebastian. After a special dry resination and forming system and pre-pressing, the glued fibre mat is steam pre-heated in a version of Siempelkamp’s ContiTherm unit which acts as a calibration and hardening unit.
In addition to these three major new developments, Siempelkamp’s ‘conventional’ wood based panel business has also been doing well. The company reports 10 major orders for its existing technologies this year up to September, worldwide – eight of them involving ContiRoll continuous presses. For the future, Mr Sebastian sees a continuing trend towards thin board, with presses getting shorter and extremely fast. The company does also have enquiries for presses up to 80m long for thicker board production and is preparing a new heavy-duty chain drive system, further developing that already designed for the 70m-plus Tolko OSB line in Canada. Presses may get shorter in future, agreed Mr Sebastian, but that will depend at least partly on external factors, such as the development of faster-curing resins.
