Laser-assisted joining process using the example of edge banding
Summary
Narrow surface coating is one of the main operations in machine furniture production. Corresponding systems are used in industry and trade and are standard equipment. Hot-melt adhesives are predominantly used, which are applied to the narrow panel surface or the coating material with a roller in a hot state in order to subsequently bond them together.
The aim of the research project was to realize this adhesive heating process using a laser and to integrate the laser technology into the production process.
The temperature behavior of the hot melt adhesives under the influence of the laser results from the optical behavior of the adhesives. For this reason, basic investigations into the heating and softening of hot melt adhesives using lasers were initially carried out. For these investigations, adhesive films were produced from the adhesives commonly used for narrow-surface coating. Different lasers were used and relevant parameters were varied with a view to optimizing the process. As a result of these tests, the possibility of softening hot melt adhesives using lasers was proven in principle. As a result of these fundamental investigations, the laser and the working parameters of the laser were specified for further tests.
The second focus of the work was on adapting the laser technology to the edge banding machine and integrating it into the narrow surface coating process. Narrow surface coating using the new process was carried out on a Homag Optimat KL77 edge banding machine under production conditions. The tests have shown that all narrow surface coating materials, adhesive types and substrate materials can be processed using the new method. In addition to process optimization, this also leaves scope for design when selecting materials. Feed speeds of up to 50 m/min were realized.
The strength and water absorption capacity of the joint were tested to assess the quality of the joint. A new test method was developed to evaluate the strength, which better reflects the stress of use than the current standard roll peel tests or the test to determine the lift-off strength. Both the strength and the moisture resistance of the narrow surface bonding are significantly improved compared to the conventional method for narrow surface coating.
Finally, a cost-effectiveness analysis was carried out. The conventional joining process was compared with the laser-assisted joining process. Various production strategies and utilization rates of an edge banding machine were considered for this assessment of economic efficiency. The comparison showed that the laser-assisted joining process is slightly more expensive than the conventional process, although it must be emphasized that the qualitative advantages in particular are not backed by a financial value and therefore cannot be included in the economic analysis.
The research project (No. 13970 BR) was financially supported by the German Federation of Industrial Research Associations "Otto von Guericke" e. V. (AiF).