Page 22 - Parquet International december 2014

ON FIELD
22
This latest edition
of the Xylexpo
showed that all today’s woodworking systems and machines have been computerized and computers can control production rapidly with flexibility
raceways. Both laths and the smaller boards can be sized with tool-holders positioned at the end of the cutting module with up to 0.05 mm precision. Wood laths can be cut to a minimum 3 mm thickness using 1.1 mm tools in satellite (a cobalt-chromium alloy) for sig- nificant increases in productivity.
Whereas bladed cutting unit feed speeds can reach 2 m/min., disk cutters can reach 36 m/min. with 1.2 mm thickness and the possibility to have a lower engraver of just 1.1 mm. This results in a 20% higher output in the production of multilayer parquet, and the machine tools used by now all pos- sess planing work centers capable of sizing the boards on all four sides with the possi- bility to obviously insert unworked smaller boards in the line.
The lath technique
Automated processes are capable of begin- ning the working of the solid wood board by planing it and transforming it into laths, and then pairing, pressing, and drying them continuously. The boards are dried in vacu- um cells with or without heating plates. The former technology is used in cylindrical vacuum cells in which the vacuum not only dries but also applies 10 ton sq m pressure on the solid wood boards for further advantages to the quality and speed of the process. The process without heating plates is adopt- ed both in cylindrical cells and parallelepiped cells with continuous or discontinuous vac- uum and with hot air ventilation; this system is best suited to making stacks of strips of wood. The market offers vertical saws de- signed for the top layer of multilayer parquet that can be inserted in production lines composed of a lath loading area (with oblig- atory identical width, whereas the length may be variable), followed by composition and subsequent gluing areas. In the final step, an assembly and drying area provides one single and continuous plank from which compositions of plank of equal size can be ob- tained from laths in two, three, or four rows
as required by the model of machine utilized. The new lines for the gluing of the single lay- ers of the multi-layer element to be laid in two or three layers utilize polyurethane adhesives spread at 120/140 °C or vinyl-based adhe- sives (70-80 °C) in order to assembly solid and not invulnerable to environmental defor- mation. The adhesive is applied in molten form on the layers to be pressed together, while the production of the three-layer ele- ment can also use melaminic adhesive due to its better resistance to chemicals and water. The bonded layers consist of obviously the noble wood top layer (3 - 6 mm thickness) and the other two or three layers of less no- ble wood species or strips of plywood (from 5 - 10 mm thickness). The adhesive be- tween the solid wood multilayer element’s layers can be made to dry quickly using a high-frequency system by adjusting the power in successive stages (12 positions) and with ceramic triodes.
Not only the finish
Most worthy of note among the profiling ma- chines and squaring machines that have by now become totally automated are those (whether with traditional tongue-and-groove or on-edge snap fit) with 110 mm tool-hold- er shaft length and feed speeds of up to 70 m/min. suited for the production of parquet with variable width of from 65 to 400 mm and lengths of up to 4 m. There are also com- bined planing-sanding units that permit the dead times that usually occur between these traditional processing phases to be eliminated. As regards parquet logistic equipment, various automatic feeders, load- ers, and unloaders capable of forms packs of strips for subsequent working could be ad- mired at Xylexpo 2014.
The alternative to varnish that consists in the heated coating of the multilayer laying ele- ment surfaces in just one single passage per- formed continuously eliminates a number of stages in the traditional process (puttying, sanding, application of the primer and sand-
TECHNOLOGY