Flexible automation and robots for the production of multilayer parquet elements.
Avisit to the latest edition of the “Xylexpo
2014” Show dedicated to the
woodworking machinery sector last
May at the Rho Trade Fair Grounds in Milan
provided ample demonstration that the
time has come to go beyond rigid, fossilized
processes in the direction of newproductive
structures that have higher flexibility in
mind. The final blow to Traditionalism was
recently given by many companies, especially
those based in Asia who have made
Just in time programming their winning
card. The market has changed radically
again, even in just the last fewyears, and the
merciless competition fromcompanies producers
in the developing world has obliged
many parquet producers to choose systems
that are capable of providing rapid response
to variations in client demands.
Reducing times and costs seem to be the factors to bear in mind in the newtechnological processes, and multilayer parquet (erroneously often referred to as pre-finished) is not excepted from these new commercial dictates, and for this reason products now tend to be completed only at the moment of shipment to the client. The advantages derived are excellent because reduced stock levels require lower capital investment.
This latest edition of the XylexpoShowalso demonstrated thatmostwoodworking systems and machines have been computerized by nowand computers permit the management with rapid flexibility of more economical production lots controlled by programs with such simple instructions that they can be programmed by anyone with a minimum amount of training. The robotizing of certain processing phases bywork centers and logistic systems has also rendered processes for both solid single-layer andmulti-layer parquetmuchmore flexible and economical. Robots are mechanisms that repeat a number of elementary operations and therefore raise output. Their widespread use has played a key role in increasing industrial automation.
The Cartesian, hybrid, and anthropomorphic robots presented at Xylexpo 2014 by many Italian and international companies vaunt a reliability that has by now been guaranteed by international regulations. The “automatic factory” is already on the horizon in the foreseeable future, and nowmany companies even in the Orient can offer CIM (Computer Integrated Manufacturing).
The advantages of automatic cutting-off machines
The multi-layer parquet adventure begins
with the planning and cutting-off of the solidwood
performed on high-quality systems
appropriate to every productive need. Automatic
cutting-offmachines comewith optimizers
that reduce scrap to aminimum, and
companies with high productions use excellent
cutting-off lines with ideal optimizers
that are quick and easy to use (less than
0.002 seconds for all cutting calculations).
The conveyor reaches elevated speedswith
extremely rapid accelerations and cutting
times, while the possibility to obtain different
sizes by means of a simple selector
suits the cutting-off machines to any need
the client may have. There are also cuttingoff
machines at the technological vanguard
for optimized cuts with translation rollers
suited to every size (unworked or deformed) with advance speeds of up to 240 m/min. and width/length readers that provide a
summary of the volumes cut.
The choice of the cutting-off machine depends on the maximum section of the solid wood to be cut. Automatic lines require no specialized operators and offer constant output, whereas optimized lines ensure higher efficiency (less scrap and higher productivity) than automatic lines.
Cutting-off machines with optimizers are commonly used to eliminate waste and accelerate the cutting of the more valuable species of woods, but their exceptionally high speed and output permit their use also with types of wood of lesser value.
Defects are displayed either by automatic scanners or by lasers maneuvered by the operator, and can by driven by roller, by belt, and by pusher bar. Disks of 550 mm diameter can be used for cut-offs on solid wood up to 800 mm wide and 25mmthick.
For productive cutting Lathsor fingers formultilayer parquet can be cut by disk or by blade on multi-blade sawing machines, whereas the topandbottomsurfaces of the lath are already suited for immediate gluing.The cuttingunit has centralized electronic control that ensuresperfect cuttingprecisionwith aminimum amount of play (0.1 mm) andfeedspeeds of up to 20m/min.
The use of hacksaw blades provides higher output (20%) than traditional processes, and even permits the cutting of laths from moist wood that is required when two or three layersmust be glued togetherwith high frequency.
The laths and boards for parquet to be cut with boxed blades can be obtained from boards that have been cut-off andworked on three surfaces (using a lateral or central ruler) or on four sides (with guides in the raceways. Both laths and the smaller boards can be sizedwith tool-holders positioned at the end of the cuttingmodulewith up to 0.05 mm precision. Wood laths can be cut to a minimum3mmthickness using 1.1mmtools in satellite (a cobalt-chromiumalloy) for significant 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 possess planing work centers capable of sizing the boards on all four sides with the possibility to obviously insert unworked smaller boards in the line.
The lath technique
Automated processes are capable of beginning
theworking of the solidwood board by
planing it and transforming it into laths, and
then pairing, pressing, and drying them
continuously. The boards are dried in vacuum
cells with or without heating plates.
The former technology is used in cylindrical
vacuumcells in which the vacuumnot only
dries but also applies 10 ton sqmpressure on
the solidwood boards for further advantages
to the quality and speed of the process.
The processwithout heating plates is adopted
both in cylindrical cells and parallelepiped
cells with continuous or discontinuous vacuumandwith
hot air ventilation; this system
is best suited to making stacks of strips of
wood. The market offers vertical saws designed
for the top layer ofmultilayer parquet
that can be inserted in production lines
composed of a lath loading area (with obligatory
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 obtained
fromlaths in two, three, or four rows
as required by themodel ofmachine utilized.
The newlines for the gluing of the single layers of themulti-layer element to be laid in two or three layers utilize polyurethane adhesives spread at 120/140 °C or vinyl-based adhesives (70-80 °C) in order to assembly solid and not invulnerable to environmental deformation.
The adhesive is applied in molten form on the layers to be pressed together, while the production of the three-layer element can also usemelaminic 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 noblewood species or strips of plywood (from 5 - 10 mm thickness). The adhesive between 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
Mostworthy of note among the profilingmachines
and squaring machines that have by
now become totally automated are those
(whetherwith traditional tongue-and-groove
or on-edge snap fit)with 110mmtool-holder
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 4m. There are also combined
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, loaders,
and unloaders capable of forms packs of
strips for subsequent working could be admired
at Xylexpo 2014.
The alternative to varnish that consists in the heated coating of the multilayer laying element surfaces in just one single passage performed continuously eliminates a number of stages in the traditional process (puttying, sanding, application of the primer and sand ing), thereby shortening finishing times enormously.Many products by nowhave elevated UV radiation stability, excellent impact strength, optimumhardness, and good chemical resistance. These products are applied liquid using a pre-heater and then solidify at roomtemperature. These short narrowstrips require three or four days of storage before they can be profiled, however.
The world of varnish
For those who use traditional processes,
water-based varnishes – the only ones with
respect for the environment
– have been
available in themarket
for quite some time
now, even if they have
often been overshadowed
products that are easier
to sell. Painting systems
are designed on
the basis of the type of
paint and finish desired
by parquet producerswhile
in mind the possibility
for light or heavy
Despite the fact that application and drying systems and cycles vary widely, there are also versatile polyvalent machines capable of being quickly and easily set up for the desired type of finish. One multilayer parquet element varnishing process that is being adopted all around theworld utilizes three coats of primer applied by roller, each of 10 g/sq m thickness.
The process consists of an intermediate semi-polymerization, a final polymerization with a subsequent intermediate sanding followed by two finishing coats applied by roller of 10 g/sq m each,with an intermediate semi-polymerization and a final UV polymerization. The system can have minimumwidths of 30 cm.
and the machines used include: lacquering machinewith standard rollers (providedwith applicator roller and dosing roller with three separate commands that permit the dosing roller to rotate in opposite direction whenever minimum applications are required), UV-module driers (that polymerize varnishing products in just a fewseconds, to which photoinitiators are added) and intermediate sanding machines (used to smoothen the surface with primer and prepare it for the application of the finish). The technology behind UV paint products permits elevated output and permit the use of minimumweight formats with noteworthy savings of material.
Paint and varnish producers have by now specialized and diversified their products by type of finish and by cycle. This means that acrylic- and UV polyester-base primers and finish coats formulated for extremely short cycleswith high abrasion resistance and excellent adherence and elasticity can now be found in the market.
The productive process future, which will
most likely be based on automatic fabrication
and CIM (Computer Integrated Manufacturing)
management keeps getting closer and
closer. It is also an accepted fact that robotizing
certain processing phases, innovative
work centers and logistic systems combined
with more and more flexible and personalized
productive cycles and processes will
provide considerable advantages in both productive
(shorter and shorter fabrication
timeswith higher and higher output and efficiency)
and economic (lower overheads and
rationalized resources) terms, in addition to
greater abundance of the offer. In my opinion,
all this should not lead to standardization
but rather the contrary: the objective and
real possibility of access tomore innovative
single devices, machines and production
lines should stimulate entrepreneurs to improve
the quality of their products.
Even if they are elementary in form, the above is always the result of a specific project that through a precise and analytical technical-productive procedure that permits the discovery of personalized solutions by involving the company first and foremost of all. These are the forms of personalization that characterizemultilayer parquet andwood flooring elements thanks to the quality of the tools, equipment, machines, systems, and lines that permit the fabrication ofmillions andmillions of laths, boards, planks, and maxiplanks for every taste, every day.