Decorative Finger of Valuable

Nikolay Skuratov Anatoliy Vojakin Moscow State Forest University Decorative Finger Jointing of Valuable Wood • Finger jointing is effective method of utilizing short pieces of and reducing wood waste. • Defect free finger-jointed lumber is raw material for many of wood products for structural and non-structural purposes and for transparent or non-transparent finishes.

WEINIG GROUP Decorative Finger Jointing of Valuable Wood • Strength of properly made finger joints is close to the strength of clear wood. General requirements for glued finger joints are described in many standards. • ASTM D4688-99: 2005. Standard Test Method for Evaluating Structural for Finger Jointing Lumber. • EN 386: 2001. Finger jointed structural timber. • GOST 19414-90: 1991. Solid glued wood. General requirements for glued finger joints. • ISO 10983: 1999. Timber structures – solid timber finger-jointing – Production requirements. • NLGA. 2002. Special products standard for fingerjointed structural lumber. Decorative Finger Jointing of Valuable Wood

• The appearance of the joints in structural products is not the most important property. • Conventional finger joint forms a zigzag or a straight line on the surface of the bonded parts which may be easy-to-see. • Such joints are not always suitable for valuable wood products having a transparent finish. Monotone joints catch the eye, bring aesthetic damage to the product and reduce its cost. Decorative Finger Jointing of Valuable Wood • The objective of the project was to develop the aesthetically acceptable finger joint profile for decorative jointing of valuable wood. • To hide the actual finger joint effectively and to make it almost invisible, curved profile of the joint was selected.

• To get away from the monotony fingers in the jointing are of different heights and the line that bends around their tops is the curve. But all fingers have the same slope. Decorative Finger Jointing of Valuable Wood • Curve profile depends on the texture of and may be a periodic function such as a sinusoid. Its parameters should match a texture of wood. • When tangential texture profile of the envelope line of larger amplitude, period, and height of fingers is more suitable. • For radial wood texture which has finer and more monotonous pattern amplitude and period can be reduced without changing of the fingers height. Decorative Finger Jointing of Valuable Wood • Most of expert evaluations showed that curvilinear splice better masks joints and improves the aesthetic perception of glued products. If sinusoidal profile of joint is symmetrical with respect to the longitudinal axis X and the midpoint 0, one cutter of such profile for simultaneous processing the ends of adjacent short pieces may be utilized. • For joining pieces into a single line every second of them should be deployed around the axis X on angle of 180°. Decorative Finger Jointing of Valuable Wood Technological line of finger jointing consists of 5 work bays: 1 – selection of wood pieces by color and fiber direction; 2 – trimming and removal of wood defects; 3 – finger cutting work bay (there are three variants); 4 – longitudinal gluing workpieces in the press; 5 – processing defect free glued details by a planer. Decorative Finger Jointing of Valuable Wood

• Work bay 1 is for matching of blanks for color, texture and the cross-section. • The ends of workpieces are processed at work bay 2 where wood defects are removed by means of CNC band machine. This machine makes curved cuts on the line along the envelope of the finger tops.

• Next workpieces are moved to work bay 3 for cutting fingers by one of three ways. Decorative Finger Jointing of Valuable Wood

• In a conventional batch line with two cutting units (work bay 3a) fingers on the package of blanks are formed successively. The first unit forms the forward profile on the front ends of blanks and the second unit forms the reverse profile on opposite ends. Decorative Finger Jointing of Valuable Wood • More productive line (work bay 3b) is designed for the simultaneous formation of the forward and reverse profiles at the ends of each blank.

• For the formation of the centrally symmetric finger joints one cutting unit is needed (work bay 3c). Decorative Finger Jointing of Valuable Wood

• Cutter forms simultaneously forward and reverse profiles on adjacent ends of two pieces. After turning over direct profile at the end of the first workpiece is transformed into reverse profile for the front end of the second workpiece (Fig. 5). To prevent chipping wood along the ends of the workpieces when the profiled supporting plates are to be used. Decorative Finger Jointing of Valuable Wood

• Also, the latter method is applicable for batch cutting fingers. Before entering the press every second workpiece must be turned over. • Further the workpiece comes in press (work bay 4), where after applying the , they are compressed in the longitudinal direction to obtain long finger jointed lumber. Then the lumber is cut by into the details of a given length, which are moved on the accumulation table for curing of glue. • At the final stage (work bay 5) defect free details are processed by means of a planer machine to form a cross-section of given shape and dimensions. Decorative Finger Jointing of Valuable Wood • As a cutting the set of wing-finger jointing cutters of different diameters can be used. Each cutter in finger joint head processes one . Decorative Finger Jointing of Valuable Wood • Cutters are mounted on the through spacer rings of different thicknesses which is fixed on the machine . • To reduce the dynamic loads when cutting the teeth of cutters are placed on a mandrel along a spiral line. Decorative Finger Jointing of Valuable Wood • Quality of finger jointing does not depend on the method of finger cutting. • Correctly selected for the specific wood texture the curvilinear finger-joint profile better hides joints and improves the aesthetic perception of glued products including details of high profile. Decorative Finger Jointing of Valuable Wood

Conclusions • The proposed method can be used for finger joining short pieces of expensive timber. • Its application will improve the appearance and increase the utility value of products made of glued wood. • In the future finger jointing geometrical parameters and design of the cutting tool are going to be optimized and strength tests will be carried out. Thank you for your attention