Finger joints make it possible to manufacture glulam boards and solid timber products of any desired length from short boards or solid timber pieces. The finger joint creates a high-strength longitudinal bond between shorts to yield a high-quality semi-finished timber product that can either be used directly in construction or further processed into engineered wood products such as glued laminated timber, etc.

PURBOND adhesives are the ideal solution for manufacturing finger joints of high strength and durability. Customers have a wide choice of application methods that meet the specific conditions and requirements of their operation. PURBOND adhesives used for finger joints are high-performance systems that react rapidly and lend themselves to fully-automatic, continuous production under a broad range of manufacturing concepts.

Applications of finger-jointed timber include:

• Boards for the production of glued laminated beams as well as duo and trio beams
• SST (finger-jointed solid sawn timber)
• Flanges in I-joists and formwork joists
• Finger-jointed components for wood construction (e.g. posts, studs, rafters, and joists)

In the manufacture of finger joints, two fundamentally different application methods can be used:

• Comb application
• Contactless application KEBA (KEilzinken Berührungsloser Auftrag)

KEBA was initiated by Purbond and developed in co-operation with application system manufacturers with the aim of offering the user greater precision, cleanliness, flexibility and process reliability in production environments.

Today, KEBA is used in a variety of versions (depending on the manufacturing process), some of which include integrated continuous application monitoring. Application monitoring is based either on an opto-electronic system (camera solution) or on the PSS (Purbond-Safety-System). The PSS currently represents the state of the art in adhesive process monitoring.

The new PSS provides the greatest possible process reliability in finger joint production at the lowest possible expenditure.

Surface gluing refers to the joining of wood pieces and boards either on the broadside or the edge to manufacture multi-layer laminated timber products.

Edge gluing is used among other applications in the manufacture of single-ply panels that are subsequently processed into cross-laminated timber products.

PURBOND adhesives are applied in a suitable application process. After application of the adhesive, the adhesive-coated parts are pressed for a defined period of time in a cold process - no additional energy (heat) is required.

The following products can be manufactured with the surface application process:

Broadside

• Glued laminated timber
• Duo and trio beams
• Cross beams
• Cross-laminated timber
• Special structural elements
• Log beams

Edge

• Semis for cross-laminated timber
• Box beams
• Edge beams

I-Joists or I-Beams are used as formwork joists in concrete construction and as rafters or posts in wood construction. Due to the particular process conditions, adhesives in the production of I-joists must meet stringent requirements. The production of an I-joist basically involves three gluing steps:

• Bottom and top flange finger joints
• Web-to-web joint
• Flange-to-web joint

In the specific production process, adhesive application at each individual gluing station (finger joints, web-to-web, flange-to-web) is accomplished either via a needle-valve or a comb system. The use of PURBOND adhesives makes it possible not only to reduce cycle times but also to achieve very high strengths.

Many years of comparison and experience have consistently demonstrated the excellent performance of PURBOND adhesives in this field of application.