07/18/2012

www.gupta-verlag.de/polyurethanes

New Cannon-Manni solution for the flexible production of very large building panels

Featuring two thin steel facings on both larger sides and a wooden frame around, these wide panels are characterised by the fact that the wood beams, about 3 - 4 m long, and are not fixed, glued or nailed to the facing sheets. The pressure of the foam from the core keeps them in place at the edge of the panel, against the side shoulders of the mould. A dimensional accuracy better than 1 mm is requested for the finished panel. The requested product mix is quite vast: wall and roof panels of different dimensions are mixed during production. There are about 100 lengths, each in 10 different widths, for the walls, while the roofs are made in about 50 lengths, each in two widths. When the shorter panels are produced, up to four of them are laid side-by-side on the same press' platen. Provision must also be made to occasionally produce tailor-made sizes. The wall panels are flat, with some architectonic design for the outside of the building, while the roof panels are of the pitched roof type and the outside facing is a trapezoidal commercial sheet. Specific moulds, that can be removed easily when switching model on the same platen, are necessary. It is also well known that commercial facing sheets are not at all accurate (discrepancies of 5 mm are not an exception) and this inaccuracy is cumulative over the 20 m length. The moulds must also compensate for these defects. Two types of polyurethane foam can be used, a standard type and a fire resistant one, that need a pour-in-place production technique: an open-mould pouring system is mandatory. All these variables obviously made the design of side moulds and setting tools a nightmare.[image_0] The largest Manni press ever built The press, an open-mould type with platens of 20,200 x 4,400 mm, is the largest ever built by Manni in their long history. It has one fixed upper platen with vacuum suckers to load in advance the upper sheet of the panel. Four extractable motorized lower platens are used as respectively service trolley to load the upper sheet, one trolley dedicated for wall panels, one for roof panel and one flexible that can be used for both types. All the platens are water-heated, inside as outside the press, for a precise temperature control. A trolley, with a zero-weight balancing system and a vacuum frame, runs over the platen to allow for a quick change of moulds. All of this means that the production line is about 115 m long. To allow for the panel's demoulding an hydraulic movable system, giving a 50 mm vertical stroke, is used. The complete moulds system has an accuracy of a fraction of a millimetre. The foam deposition, in open mould, is done while the movable platens enter in the press. An accurate position system gives the signal for the start and stop of the pouring, taking into account not only the variable speed of the platen but also the inertia of the dropping foam to obtain an exact laydown of the requested foam. A very generous "wet end” In an open-mould pouring system the most critical point is to get a fast movement of the platen, linked with a high-enough components output, so that the press is surely closed before the foam reaches the edge of the mould. The installed Cannon "wet end” allows for a maximum total output of more than 1,000 l/min, given by three dispensers with three large, new Cannon JL 32 mixing heads. Allowing for a single output of more than 6 kg/s, this head is a new concept of high-pressure, self-cleaning mixing head without injection nozzles (JL = JetLess).Besides its high output, this head provides a better mixing efficiency than the classical "L-shaped” head at this output level. This provides less foam overpacking and, as a welcome consequence, some chemical's savings. The three mixing heads are fixed on an automatic portal placed over the entrance of the mould cavity, on one of the short sides of the press. The heads can be used as to pour three individual streams of foam or, equipped with perforated pipes, to pour in place over the whole panel width. At the end of the foaming operation the holed pipe is automatically dropped inside or outside of the panel. One or the other pouring system can be used according to the output or to the type of foam used. Controls The whole line is highly automated and can be fully integrated with the factory central control system. A library system, containing all the characteristic and dimensions of the panels that can be produced, is recalled from the production planning department. This list of mixed wall and roof panels is sent to the production department, which collects the information they need to set up the panel and automatically downloads the foaming and press settings to the line, via a simple text file. Modifications to this pre-set program can easily be made according to the effective production needs. At the end of the shift all the used parameters are collected and stored for the individual panel's records and for possible later check.

www.gupta-verlag.de/polyurethanes