Extra-Large Plant for Just-In-Time Discontinuous Production of Wall and Roof Insulated Panels Robert Verbruggen Max Taverna Cannon Group, Cannon Group, Rijksweg 15 Via Resistenza, 12 B-2880 Bornem, Belgium I-20068 Peschiera Borromeo, Milano, Italy ABSTRACT The request for large foam -insulated sandwich panels is on the rise in Europe, and Polyurethane s characteristics perfectly match the processing difficulties linked with these huge elements. A Cannon - Manni foaming plant has just been delivered in Europe to produce very large building panels in a just in time sequence, according to the method used to assemble the final building. THE REQUEST The Cannon Group received a request, from a major European producer of insulated sandwich panels, to build a complete line for the manufacture of very large sandwich panels for building applications: the maximum requested dimension was up to 20m (66ft) of length by 4.2m (14ft) of width. The line had to be able to produce both roof and wall panels, in a very large number of different sizes. The PUR-filled panels had to be foamed in one shot, without any compartment inside the cavity. Wooden beams had to be used as side-containment elements, while the facings had to be steel sheets, corrugated with a Greek key trapezoidal profile for the roof and a flat design for the walls. These specifications made it probably the largest single-shot PUR panel production plant in the World, a true challenge for Cannon and Manni not only because of the panels dimensions but also because of the variety and complexity of the panels to be produced. Logistics for steel sheets centering in the press was one the major aspects to be considered during the designing phase, not to forget the requested clamping force for the polymerization press and the metering system s output. Due to material s reactivity and to the proposed laydown method an open-mold pouring system the dosing equipment had to be huge, in order to supply the whole lot of PUR foam well within the cream time of the formulation and an appropriate solution had to be found for a splash-free mixing and dispensing operation. THE CANNON SOLUTION Cannon and Manni have a very long experience in the production of large panels made with open-mold pouring. For example this line located in Germany consist of five large presses and produces each 30 min all the panels needed to assemble one insulated trailer (Pictures 1&2, next page).
Pictures 1&2- Complete foaming line (left) for the manufacture of two insulated trucks (right) per hour But what is an open-mold discontinuous production system? It generally consists of: (Picture 3) One polymerization press with an up-stroking lower platen that lifts properly designed trolleys placed on rails that hold the components of the panel. One heated service trolley, positioned on the left side of the press, designed to load the upper metal facing of the panel and fix it onto the upper platen of the press. Two movable lower platens of the press platens, placed on the opposite side, on the right of the press, where the panel, composed by a lower metal facing, some inserts, the side elements (and their containing molds) is placed, ready to be filled with PUR foam. These lower platens compose a shuttling system: while one platen is curing inside the press, the other stands outside in a working station, where the preparation of the next panel occurs in masked time. Picture 3 Scheme of a Cannon Manni open-mold discontinuous foaming production system for sandwich panels Let s follow the standard production cycle, starting from the end of one panel s production. At the end of the curing time, the press opens and the trolley with a finished panel shifts out, on the right side. (Picture 4 ) Press Upper sheet trolley Open mould platen 1 Open mould platen 2 Picture 4 Phase 1: Press opening
Simultaneously the trolley carrying a new upper metal facing enters from the left into the polymerization cavity. (Pict. 5) Press Upper sheet trolley Open mold platen 1 Open mold platen 2 Picture 5 Phase 2: extraction of finished panel on mold platen 1 and upper sheet introduction The press closes and the upper facing, a metal sheet, is picked up and held firmly in position by a number of vacuum suckers distributed all over the upper press platen. (Picture 6 ) Press Upper sheet trolley Open mold platen 1 Open mold platen 2 Picture 6 - Phase 3: upper sheet positioning on the upper platen finished panel unloading from mold platen 1 In the meantime, on the platen on the right, that now stands outside the press with the finished panel, the unloading operations can be automatically performed with an overhead crane provided with a large number of vacuum suckers. Once the upper sheet is loaded, the press reopens and in the meantime the bar holding the three mixing heads comes down and stops just over the edge of the new panel, ready for starting the foaming operation. The trolley that held the upper facing sheet rolls out of the press, leftwards: simultaneously, the next trolley containing the new panel to be foamed enters in the press from the right. The dosing operation of the chemicals starts. Two types of PUR foam can be used in this specific case, a standard type and a fire-resistant one that needs a pour-in-place production technique: an open-mold pouring system is mandatory. ( Picture 7 ) Press Upper sheet trolley Open mold platen 1 Open mold platen 2 Picture 7 - Phase 4: Foaming and introduction of mold platen 2 in the press
The mixing heads dispense a huge amount of PUR through a set of three hollow plastic pipes mounted on their nose. (Picture 8 ) The liquid is evenly deposited throughout the whole length of the panel, covering the surface of the lower facing metal sheet. In this way the foam must only rise vertically, avoiding long runs across the panel and all the involved problems of air entrapment and cell structure deformation. This pouring system is similar to that normally used in continuous lines. Picture 8 High-pressure, high-output delivery of PUR foam over the moving mold platen while it enters in the press It is crucial that the introduction of the new panel in the press is done at high speed (normally at 1 m/sec, or 2 mph) so that the press can be closed before the full rise of the foam, to avoid leaks of material or, even worse, the compression and crushing of portions of foam already risen. Over 300 kg of foam for the largest panel of the discussed case must be deposited in less than 30 seconds: this means that a high-output dosing machine is required for the wet end of the plant. For this large plant the PUR output is more than 1,000 Kg/min, or 37 lb/sec, dispensed by three large mixing heads. More on this in the following paragraphs. When the press closes the curing can start. The curing and total cycle time will depend on the thickness and type of the used foam. (Picture 9) Press Upper sheet trolley Open mold platen 2 Open mold platen 1 Picture 9 Phase 5: Polymerization, positioning of new upper sheet and preparation of new panel on mold platen 1 Typical cycle time for the largest panel in the discussed case averages 50 minutes. This gives the operators ample time for the preparation in masked time of the next panel to be foamed. Thanks to the double-shuttle system used to feed the press, the lost time - or open-press time is only a couple of minutes per cycle.
An overhead crane picks a number of pre-bent metal sheet elements, constituting the lower panel s facing, and lay them on the lower shuttling trolley. Once the preformed sheet is dropped on the platens, the four wood bars constituting the sides of the panel are positioned around the metal lower facing, without further fixing operations. It is interesting to notice that there are no compartments or special reinforcements within the panels. This on one side makes life easier from the point of view of foaming, since it avoids to pour over an uneven base creating areas of foam with different density from the nearby one, but on the other excludes any possible mechanical help to the wide structure of these panels. The whole system must be perfectly tuned to produce a dimensionally-stable panel, avoiding deformations, twisting, markings on the facings. The upper sheet trolley is used to introduce and fix the upper-facing metal sheet in the press before foaming. Here another complication arises: even if the quality of these sheet is sometimes poor, in terms of waving, the panel must be perfectly flat and without marks. (Picture 10 ) Picture 10 Metal sheets used as facings are often irregular in terms of surface ( waving ) and of dimensions: but the finished panels are expected to be perfectly flat and equal in size! Foaming at the right temperature is crucial to obtain a good adhesion of the foam to the metal sheets: all the five platens are provided with a circuit for thermo-conditioned water, whose circulation occurs all the time, when the trolleys are inside as well as outside the press. This permits a perfect preheating of the sheets. Metal supports are used to press firmly the sheet against the vacuum suckers in the press until it s safely held in position. Reference angle-spacers permit a relative alignment of the upper and the lower sheet better than 1 mm. (Picture 11) Picture 11 Metal supports hold the upper lining sheet during the positioning on the upper press platen.
PANEL CHARACTERISTICS AND SPECIAL REQUESTS One of the most difficult aspects in this project has been the need to cope with a very wide mix of products to be made without major adjustments of the tooling. Let us see the main characteristics of these large panels. Roof Panels The roof panels are of the dual-pitched type with trapeizodal greek key upper sheet and a flat steel sheet on the bottom. (Picture 12) Picture 12 30 mm pitches characterise the profile of a part of the roof panels. For reasons linked with the correct expansion of the foam and with the most rational method of tool adjustments, the panels are produced upside down, with the flat side upwards. The molds are adapted for two different widths and a lot of different lengths: as of now up to ninety measures have been specified. Their thickness very around 180 mm. Special compensation plates and side molds have been developed to provide the widest compatibility for the existing and the possible future panel models. (Picture 13 ) Picture 13 - Special compensation plates and side molds provide compatibility for existing and possible future models
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 molds must also compensate for these defects. 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 tools for the roof panels include mobile sides, transversal mobile sides to allow for the easy demolding, side molds and spacers. To allow also for the production of intermediate dimensions a scissor system was installed on the longer sides of the lower platen, so that infinite step-less width settings are possible. (Picture 14 ) Picture 14 The lateral scissor system allows for the production of intermediate dimensions The platen must be converted easily from wall to roof models, so a loading manipulator with zero-weight handling features is installed to allow for an effort-less change of molds. This lifting device is also used for metal sheets handling and easy positioning in situ. This device runs over the entire length of the platens. (Picture 15) Picture 15 - a loading manipulator with zero-weight handling features allows for an effort-less change of molds
Wall Panels The wall panels are flat on the inner side of the building (the one positioned on the upper side of the press) but have horizontal and vertical seams on the outer side. There are more than 1,000 different sizes to be produced as standard. Their thickness is constant for all models: 100 mm. All around the panels, wall and roof, there is a peripheral wooden beam, but no beams are foreseen inside the panel. This frame is neither fixed nor nailed: loose beams are just pushed by the foam against the mold all around the panel and this mechanical operation must produce a perfectly repetitive size of panel, with an accuracy better than 1 mm! Here the most difficult thing is to guarantee perfect flatness to these huge, aesthetic parts. (Picture 16) Picture 16 - a 20m long perfectly flat panel looks impressive! A HUGE DRY SIDE The dry side of the line, supplied by the Italian specialist Manni, is composed by a polymerization press 20,2 m long and 4.4m wide, fitted with a platform to hold the wet end. (Picture 17 next page ) On the left we can see the trolley used to heat up the upper sheet and to introduce it in the press On the right we have the shuttling lower platens, used to build up the next panel in masked time and as pouring platens. There is a platen dedicated for walls, one for roofs and a flexible one to permit the production of roof or wall according to the production planning. In the second position a lifting table guarantees the same working level for all the platens.
Press with platform for wet end Wall platen Roof or wall platen Roof platen Upper sheet trolley No-weight handling trolley Picture 17- Scheme of the complete, 120m-long, Cannon Manni foaming plant The total length of the line is about 120m. The most important feature for an open mold pouring system is to enter in the press at high speed while foaming, so that the press can be closed quickly before the foam starts rising too high. The two trolleys (sized 20,2 m by 4.4 m and weighing 50 ton) run at 1 m per sec (over 2 mph) and are built to accelerate and brake over a very short distance. Obviously the planning system must inform the wet side in order to foam exactly where required by the size of panel currently present on the lower trolley. 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 material. A GENEROUS WET SIDE The installed Cannon wet end allows for a maximum total output of more than 1,000 l/min, given by three high-pressure, pump-driven dispensers (Picture 18- next page) feeding three large, new Cannon JL32 mixing heads. Allowing for a single output of more than 6 Kg/sec, this head is a new concept of high-pressure, self-cleaning mixing head without injection nozzles. Besides its high output, this head provides a better mixing efficiency than the classic L-shaped head. This provides a more uniform foam distribution which requires less overpacking to perfectly fill the mold: as a welcome consequence, this provides some chemical s savings. Its special design eliminates the use of pressure-adjustment nozzles: mixing occurs by high speed, generated by reducing the available section of duct during the transit from a primary mixing area to the true mixing chamber.
Picture 18 & 19 The high-pressure metering unit (left) is able to dispense more than 1,000 kg of PUR components in one minute. The Cannon JL 32 mixing head (right) features a mixing chamber s geometry without nozzles, for simpler operations and easy change of output during production. It is particularly suitable for gaseous blowing agents. Eliminating nozzles means that a major adjustment operation is no more required, and also means that output variations can occur, even on-the-fly during the pouring or injection phase without any negative effect on the mixing efficiency, provided that the final pressure does not drop below 70-80 bar. (Picture 19) The three mixing heads are fixed on an automatic portal placed over the entrance of the mold cavity, on one of the short sides of the press. (Picture 20) Picture 20 Three Cannon JL 32 during the open-mold dispensing phase, with a pour-in-place device that distributes the reacting liquid over the entire surface of the panel, for more uniform foam density distribution across the panel and better adhesion to the metal facings. The heads can be used 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 pipes are 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 fully integrated with the factory central control system. (Picture 21) Picture 21 Complete Data logging and Production Downloading software allows for full integration of this plant with the factory computers network A library system was also supplied, containing all the characteristic and dimensions of the panels that can be produced; this library is recalled from the production planning department. A 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 PC text file. If needed, this flexible system allows also for an easy modification to the pre-set program, according to the effective production requests. At the end of the shift all the used parameters are collected and stored in a PC language for the individual panel s records and for possible later check. CONCLUSIONS This fully-automated, huge sandwich panel production line has been a real challenge for Cannon and Manni. With a good cooperation, especially with the customer, the results have been very positive since the very first foamed panels. The plant is fully operational in Europe since beginning of 2012. Its maximum productivity can reach 720 m²/8-hour shift, depending on the panel sizes. Extra-large panels, characterized by a simple structure and a wide variety of sizes can be produced with this discontinuous foaming method using an highly-automated manufacturing system. Thank you for your attention!
AUTHORS Robert Verbruggen Bob was born in Brussels, Belgium, in 1948 and obtained his PhD in Sciences (Organic Chemistry) in 1974 at the University of Leuven (Belgium). He worked several years in water analyses and treatment. Since 1980 he cooperated with the Cannon Group. In 1998 he joined the Insulation Group and is the reference within the Cannon Group for all Sandwich Panels matters. Max Taverna Max was born in Buenos Aires, Argentina, in 1949 and has an education background in Industrial Chemistry. He worked for Upjohn's Polyurethanes Division in Italy and joined Cannon Afros in 1982 as the European Sales Manager. From 1986 to 2009 he served as Corporate Director of Communications & IT. Currently retired, Max cooperates with Cannon (www.cannon.com) for editorial and content-related projects.