Basque Country, Spain
The overall goal of the project called Woodwork is the detection of composite materials consisting of cellulosic fibers and resins, having physical-mechanical characteristics suitable to ensure a high dimensional stability and duration in order to replace the existing materials in the realization of work plates of CNC machines and cutting machines.
The work tables of these two types of machines for working wood (and plastic materials), have different characteristics because the functions that must accomplish are fundamentally different.
The main characteristics to be obtained on the materials to be developed, indicated by the project specifications, are mainly the improvement of dimensional stability to have a high precision on the working tolerances, a good resistance to wear by friction in order to extend the working life of plates, an increase of the resistance to scratching, chipping and flame and, finally, the optimization of distribution ducts of vacuum for the clamping of the work pieces in order to reduce the consumption of the pumps and a more flexible positioning of the pieces themselves and the selection of the areas to be activated.
The final result of the project Woodwork consists of work tables, developed for both machines, of higher quality than currently offered by the market, in terms of hardness and wear resistance, dimensional stability and surface homogeneity.
Starting from a series of different materials available in the market have been selected 18 products on which were made tests for dimensional stability under controlled climatic conditions. The results of these measurements have indicated in particular two composites that have been used in the further subsequent activities.
Some impregnating agents have been developed which, when applied by spraying, confer to the surfaces of tables a better hardness, greater resistance to flame and, above all, render them impermeable to water, oil and steam. The machined and impregnated plates have shown in tests of dimensional stability in various climatic conditions a net decrease of deformation below the defined range of tolerance of ± 0.10 of the nominal size. Also as part of the treatment of coatings, have been developed flame retardant resins which, when applied on the plates and made suitably lattice, inhibit the spread of the flame and the bulging of the piece due to the detachment of the individual layers of fibers.
A careful study of the air ducts, allowed to maximize the yield of the aspirators that, by creating a vacuum on the support surface, secure the work pieces in the correct position.
The milling of such channels have been obtained with specially selected tools for the machining of these types of composites, with cutting edges that reduce the “tearing” of cellulosic fibers from the “body” of the material.
Finally, plates have been produced to scale for both CNC machines and cutting machines, with the materials that have provided the best performance during testing. They have also been treated superficially and installed in actually working machines. Based on the observations of the behavior of the treated surface for cutting machines, it was possible to calculate an average length of the flame retardant coating, approximately 6-10 months depending on workload and type of load of the machine.
This coating is still recoverable using normal spraying with paint guns.
Similarly to what was done for the cutting machines, was chosen a CNC machine on which were mounted the plates to be tested in order to have constant conditions.
Once the plates have been set on the structure, have been smoothed with a finishing tool, to clear any errors of misalignment between the guide head tool holder and the bank itself. After having fixed the plate, we proceeded to the preparation of polymer impregnation. Once the process is finished, at room temperature, has begun the phase of real use of the plate by resuming routine production activities.
To check that the measures of planarity and dimensions fall within the tolerances defined in terms of the project, monthly, at the end of the shift, were measured with the comparator some points on the plate as laboratory tests, and it has allowed to verify as these measures have never deviated from the target cross-tolerance of 0.10%. In the same manner were also identified external measures of the bank which were also defined within 0.05% as a result attained by the end of the project.