Spiders - useful helpers in timber construction

The forests of the Black Forest provide a variety of wood species such as spruce, fir, beech and oak, which are used in construction, furniture production, paper production and other industrial applications. HolzBauWerk Schwarzwald, founded in Seewald in 2021, specializes in cross-laminated timber (CLT). On 15,000 square meters of covered area, the company manufactures 20,000 cubic meters of CLT per year and shift from local spruce and Black Forest silver fir wood. Clients use the products to realize timber construction projects throughout Germany, Switzerland, France and the Benelux countries.

HolzBauWerk started production in September 2022 and currently employs around 40 employees. The operation uses a fully automated system to produce solid wood sheets from at least three layers of softwood boards laid crosswise and bonded together flat. They are between six and 32 centimetres thick, up to 3.5 meters wide and a maximum length of 16 meters. The sheets are suitable for the flat and solid manufacture of wall, ceiling and roof elements. Invented in the 1990s, the sheets have become increasingly popular in modern timber construction since the 2010s thanks to their advantages such as sustainability, stability, fire protection, thermal efficiency and earthquake safety.

To ensure a high and consistent quality, the company dries all the wood itself. In the next step, employees sort the sawn timber according to visual and technical criteria. The SSP suction spider from Schmalz then lifts a layer of boards with five FMHD area grippers and stacks them slightly offset in four places in a buffer store. An external vacuum generator supplies the robust gripping system with the necessary vacuum. Thanks to the integrated system monitoring and sensor technology, the suction spider works reliably. The five FMHDs handle heavy and rough workpieces with ease thanks to the sealing foam, and even knotholes, warping, unevenness and cracks do not disrupt the gripping process. The integrated vacuum reservoir and the maintenance-friendly design ensure low energy requirements and smooth processes.

For the subsequent CLT production, another suction spider with four FMHD grippers first destacks the board layers. The manufacture is fully digitalized and produces wooden boards with different thicknesses and areas in batch size 1. "In the first step, defects such as resin pockets, cracks and knots are cut out depending on the quality requirements. Then a finger-jointing line connects the sawn timber to form a so-called continuously cut board, which a saw cuts to the target length. The shortened strips are then glued together on the narrow side to form single-layer boards," explains Andreas Bauer. He is Head of Design and Joinery at HolzBauWerk. This process guarantees closed visible surfaces, a high level of airtightness, good fire protection properties and optimum strength.

A third suction spider with FMHD grippers then places several single-layer panels alternately as length and cross layers on top of each other in a buffer store. Another, identical suction spider is responsible for feeding the CLT press. After each single-layer sheet has been placed, a glue applicator applies a layer of glue that ensures the necessary cohesion in the end product before the suction spider places the next sheet on top. "We use PU glue that is harmless to health, which does not release any ingredients after curing and is therefore well suited for use in house and apartment construction," explains Bauer.

The hydraulic CLT press joins the single-layer panels made of lengthwise and crosswise lamellas, the so-called press cakes, under high pressure to form the actual cross laminated timber. This process guarantees a perfect, very thin glue joint and absolutely dimensionally accurate and straight sheets. The CLT sheets are handled after the block press by two suction spiders that are attached to an overhead crane. They feed a reversing table, a wide belt sander and the CNC machining center with the raw panels, which produce ready-to-install house construction elements from them.

After processing in the machine center, the fifth SSP-HD vacuum suction spider picks up the cut sheets. The special feature: This rather small and handy suction spider is designed for heavy loads (HD: heavy duty) and can carry 2.5 tons. This is made possible by the SPU suction plates. They are ideal for handling flat, smooth workpieces, but also those with slightly rough surfaces, as they offer high suction forces with small dimensions. The SSP-HD uses them to lift the cut elements and the resulting cut-outs from the machine thanks to vacuum. Individual suction cups can be selected or switched off as required. Suction cups that are not in use are automatically inactive to prevent leakage.

Schmalz has designed all vacuum gripping systems individually for the different handling tasks at HolzBauWerk. The low weight of the basic aluminum components and the high holding forces allow for fast cycles. "When planning the complete systems, we can draw on many years of experience and many systems in Germany and abroad," emphasizes Philipp Bohnet. He is Head of Sales Systems at Schmalz and supported HolzBauWerk and the machine suppliers involved in the design of the vacuum technology. "At our test center in Glatten, we also use suction tests with customer samples to identify potential weak points immediately and work out suitable solutions. This allows us to guarantee process reliability and quick and easy integration right from the start," he supplements.

The wood processing company has been using vacuum technology from Schmalz since September 2022. "Everything went smoothly from the first contact in spring 2021, the preparation of the quotation, project planning and start of operations to live operation," emphasizes Jörg Kübler, Managing Director of HolzBauWerk Schwarzwald GmbH. "Our employees also really enjoy working with the vacuum gripping systems, as they ensure automated and trouble-free processes. The systems have even been given names," he adds with a wink. And there's something else Kübler likes - the proximity to the vacuum experts. "The company is practically around the corner, so we can count on support very quickly in case of problems," he says.