There’s a significant and unique development underway at SWG Produktion’s HQ, signalling capacity increase in its Waldenburg base for more screws, made in Germany, explains Dipl.-Ing (FH) Susanne Jacob-Freitag…
A new production hall is currently being built at the company headquarters of SWG Produktion Schrauben-werk Gaisbach in Waldenburg (Baden-Württemburg, Germany) with an attached office and exhibition building.
Founded in 1967 and part of the Würth Group, the company is one of the largest screw manufacturers in Europe. With around 230 employees, SWG Produktion produces up to 12 million screws per day – and the number is rising. In the past, this increase has led the company to consider future expansion of its production capacities and build a new production hall as well as reorganise the company headquarters.
New production hall with a flagship visitor pavilion – with an environmental message
What was formerly under consideration is now to become a reality: With gigantic dimensions of just under 96.50 m x 114 m and height of around 12 m, a production hall is currently growing from the ground of the company premises over an area of 12,800 m². The hall is divided up with 70% for production and logistics and 20% dedicated for tools and tool manufacture as well as a storage area for raw materials such as wire, etc. As a kind of annex, a three-storey side building will be built next to it for offices, conference and exhibition rooms. This is connected to the hall via a bridge. The hall, like the visitor pavilion, is built of wood.
The group of buildings was designed by Hermann kaufmann from Schwarzach (Vorarlberg, Austria), known worldwide as an architect of stringently thought-out wooden architecture with a good deal of timeless simplicity. For the elegant roof structure of the hall, he has even chosen a special wood, namely beech veneer plywood, so-called BauBuche (from Pollmeier).
The choice of wood as the material for the supporting structure or sheet metal and metal for the facade on the one hand reflects SWG Produktion’s specialism and the areas of application of the screws for the wood and metal sector. On the other hand, sustainability was an important aspect in the choice of renewable raw materials: Due to the high use of hardwood or softwood for the visitor pavilion , the company wants to contribute to the reduction of CO2 output. With BauBuche not only could the architectural design be optimally implemented, but the amount of wood required could be efficiently used, keeping resources to a minimum. In total, about 1,800 m³ of wood will be installed. this means that compared to a conventional construction there have been CO2 savings of around 3,600 tonnes – related to a useful life of 50 years. Finally, the use of local woods brings with it the effect of local value creation.
With the construction of the new hall, production capacity can now increase, but the new visitor pavilion also exhibits the in-house products that will be produced in the new hall, as application examples, so illustrating the full timber construction. Screw connections for wood-concrete composite ceilings, developed by SWG Produktion, will be shown there as well as the implementation of classic wood connections, including those with high-performance construction material BauBuche. The best example of which will be the hall itself.
Wood architecture for elegant simplicity
The hall is designed with five aisles and is spanned by a comb-shaped roof. The aisles are just under 20 m wide each. Their roofs project down at the longitudinal sides at regular intervals, where they continue for a few metres at this height, and then go back to the original height. On the one hand, these regular projections divide the large hall, on the other hand, they have to same function as shed roofs: They provide plenty of natural light in the hall interior.
The roof structure is made up of truss girders from the aforementioned high-load-capacity BauBuche. they sometimes bridge enormous spans, such as the 82m long and 3.80 m high mean trusses in the longitudinal direction of the aisles, only supported on a BauBuche column, as tow-section girders the y span a 40 m and a 42 m section. The secondary truss girders stretch across almost 19m and are based on these main trusses. BauBuche was the material of choice here, in order to obtain as narrow as possible cross sections despite large bridging widths. The planners from the in-house engineering firm, SWG Engineering, made maximum use of the load-bearing capacity of the girders in order to be as material-efficient as possible. At the end. around 420 m³ of special hardwood will be installed.
BauBuche needs BauBuche-compatible screws
The use of BauBuche also requires the use of special screws and steel fasteners approved for the material. The half-timbered factories of the production hall therefore use the approprite approved connectors produced by SWG Produktion itself; particularly ASSY® fully threaded screws – or more precisely the ETA (European Technical Assessment) of BauBuche from Pollmeier (ETA-14/0354) in combination with the ETA of ASSY® fully threaded screws from Würth (ETA-11/0190). The crucial factor for safe use is the linking of the two ETAs, i.e. the relation that the respective ETA has on the other. By coordinating these two products, the manufacturers give the user and structural engineer the legal certainty of being able to use them together. however, ASSY® full thread screws can also be used for softwood.
ASSY® self-tapping screws are made of special hardened carbon steel or stainless steel with anti-friction coating and corrosion protection. The previously available external thread diameters are between 3 mm and 14 mm, and the total length of the screws is between 13 mm and two metres. Due to the large dimensional variability, this type of screw could be used with all truss girders, i.e. the main, secondary and stiffening trusses.
Special tool for hardwood processing
Special, material-specific tools are also required for the processing and assembly of hardwood components, such as for pre-drilling and screwing in the screws. ASSY® are, however, self-tapping screws that do not require pre-drilling. For BauBuche components, pre-drilling makes sense due to the high material density. Apart from the fact that this defines the screw positions, which is helpful (especially with a large number of screws as with the joints of the production hall) they do not have to be marked out on the construction site. This saves time and helps to avoid mistakes. Pre-drilling also enables the screws to be screwed into the components according to plan and accurately. Due to the high material density of the BauBuche, it should also be ensured that shorter screws with larger diameters are used rather than long thin ones. And last but not least, you need a screwdriver with high torque to screw in the screws.
Numerous carpentry connections as nodal joints
Many of the junctions have been designed by the structural engineers as carpentry joints, but they have been adapted and optimised to suit the BauBuche material. This also arose from the fact that the simple geometries of these proven wood joints set well and allow the components to be joined without jamming – while at the same time providing optimum force transmission in the joints.
Production starts at the beginning of 2020 under Germany’s largest BauBuche roof
SWG Produktion commissioned Schlosser in Jagstzell (Germany) with the prefabrication, delivery and assembly of the timber construction. The assembly of the timber construction is to start in May. Four to six weeks of assembly time are planned and completion is scheduled for end of 2019. Production is schedule to start at beginning of 2020, under Germany’s largest BauBuche roof structure.