UV-LED based curing of lacquers on furniture parts
SC Freda, Lithuania’s oldest furniture manufacturer, has started operating its new high-speed painting line for finished furniture parts.
The company specializes in the production of ready-made self-assembly furniture made of chipboard, MDF and cellular lightweight boards. In order to expand its production capacity, SC Freda has expanded its production with a new plant. It includes the new high-speed UV varnishing line, which was developed together with the partner Efsen UV & EB Technology. The planning of the highly efficient and intelligent UV production line started in 2017 with the aim of implementing a modern, efficient and environmentally friendly production process. Efsen wanted to go a step further, compared to existing setups. The goal was that the use of UV LEDs would not be limited to the intermediate curing process. Partnering with AkzoNobel from paint side, the course was set to make the new process possible. A new curing process was developed in which UV LED technology replaces conventional UV lamps. The only exception is the end of the line where an Hg system used.
In this kind wood coating process, two clearcoat layers are applied to seal of the surface. Thereon, several base coats are applied for coloring. The final step is the application of a top coat system. The challenge was to develop a process adapted to the UV LED applying a target production speed of approx. 50 m/min. On the one hand, the focus was the complete drying of the clear coat in front of the sanding station to avoid clogging the belt, on the other hand processing both light and dark base coats. The solution was to define an individual wavelength for each station. A height-adjustable UV LED is used for the final curing in order to specifically influence the gloss level in the finish. The low temperatures of a UV LED process in connection with the control of the radiation homogeneity by the “ICAD”-technology of Efsen allows an extreme stability of the gloss level in the finish. Furthermore, the low temperature process prevents melting problems of the edge band glue.
Compared to conventional systems, the new development is expected to save approx. 55% of energy. In addition, the UV LED systems have a longer service life and minimum maintenance requirements. A further advantage results from the fact that conventional systems remain in stand-by mode when production is interrupted. W-LED systems, on the other hand, can be switched off completely without any problems.
“WoodCure” arc lamp systems are also installed for the final cure. Among other things, these have optimized temperature controls, which improve the homogeneity, output and service life of the UV bulb.
In order to guarantee long-term process stability, the “ICAD” system is used in the plant. This is an inline measurement device that continuously measures the UV power emitted to the substrate. Local deviations are detected and corrected by the power control of the smallest LED segments. This generates a homogeneous radiation characteristic with <5% deviation over the entire width of the LED. The measurement data can also be transferred to external systems in order to create a complete documentation of the radiation output over the production period.
Further information: www.efsen.dk