Development of Half-Blind Dovetail Joint of Laminate Floorings by Computer Aided Analysis

Abstract

As pursuing improvement of life quality interest in raw material and joint system of flooring, which is in contact with the most human of living space, has increased. Wood is prominent sound absorption and beautiful pattern flooring material. Sawn wood is inappropriate for floor heating system because of low heat conductivity and deformation by distortion and cracks. To make up for the weak points, laminate flooring was developed. In early 1990s, click profile joints was developed mechanical locking system which was combined each other without adhesive. Click type laminate flooring has grown significantly in popularity, because it is easier to install and maintain than traditional hardwood flooring. However, the floor heating system caused some problems at laminate floorings. When floor heating is operated, laminate flooring is shrunk. In this case, tensile strength of click-profile flooring becomes weak and then a gap occurs at each joint. Another problem is low heating velocity because of thick floorings. In this study, new design of dovetail joint was developed for minimize thickness of flooring. Lower side of the dovetail joint was designed to be connected apart from 4mm at the bottom. And upper side was designed to form shape of oblique line to prevent sticking out floorings upwards. And every edge of dovetail joint was cut round to assembly angling combination. Tenon and mortise of dovetail joint was connected horizontally and vertically. In comparison with click joint, which is composed of 3 protrusions (two of mortise and one of tenon) dovetail joint is composed of 2 protrusions (one of mortise and one of tenon). So, thickness of dovetail joint could be reduced. Heat performance of flooring was analyzed by computer aided engineering (CAE). Because joint profile was complex experimental, analysis of joint structure was limited. But, CAE (Computer Aided Engineering) makes it possible to predict structural performance of joint. As result of floor heating simulation, surface temperature of dovetail flooring was 41.5℃ and dovetail joint temperature was 40.7℃. Then, surface temperature of click flooring was 40.6℃ and its joint temperature was 36.5℃. Temperature of dovetail flooring was higher than click flooring. The reason was that heated air from heat film was leaked along the click joins in horizontal direction. Heat loss from the part of click joint occurred more than dovetail joint. In experiment, the temperature of dovetail joint was 38℃ and temperature of click joint was 37℃. Temperature of dovetail joint was 1℃ higher than temperature of click joint. Binding force of dovetail joint was higher than click joint. Because thin dovetail joint could be connected each other with strong binding force, which is similar to it of click joint by dovetail joint, thickness of floor could be decrease. This, also, could lead to reduce manufacturing and heating cost as well as reducing heating time.