Study of ultrasonically welded thermoplastic dowel-wood board assembly

Abstract

• Ultrasonic welding is a fast joining of thermoplastic dowel-wood board assembly. • Density of wood board plays an important role in ultrasonic welding. • Dowel pulling force inversely proportional to the depth of the drilled hole. • Ultrasonic thermoplastic dowel welding is not suitable for wet wood boards. This study reports on an ultrasonic welding application for the assembly of a thermoplastic dowel and a wood board. Three types of medium density particleboards (MDP) and fiberboards (MDF) were used to indicate applicability of ultrasonic welding to fix a plastic wedge dowel into the wood boards: light-weight, standard, and heavy. Plastic wedge dowels made of resin nylon thermoplastic polyamide PA66 were used to compose ultrasonically welded wood boards’ joints. Ultrasonic welding is a joining technique without any additional substances, such as adhesives or solvents. It possesses local heating of only the joint area, short cycle times in the range of just a few seconds, and comparatively low cost-efficiency. During the ultrasonic consolidation process, energy generated from an ultrasonic transducer is transferred to the joint components (dowel – wood board) in the form of ultrasonic oscillation. The quality of the welded joint is mainly influenced by the density of the wood board, the quality of wood particles bonding, the depth and diameter of the drilled hole. The size of the contact area of the drilled hole (hole geometry, density and the size of hole walls) is also very important because the molten thermoplastic requires enough space to penetrate and settle to form a solid assembly.