Studies on Manufacturing of Wooden Flat Pallet by Staggered Connection Using Sugi Compressed–dowel and its Process

Abstract

In this study, we manufactured three types of the wooden flat pallet with different in the number of sheets of the top board of the backside. First type (7–7 type); the number of sheets of the top board of the backside was seven pieces. Second type (7–5 type); the number of that was five pieces. Third type (7–3 type); the number of that was three pieces. The number of the surface of three types was all seven pieces. In the manufacturing, the staggered connections using sugi (Cryptomeria japonica D. Don) compressed– dowel were applied to the pallet, and the evaluation test in accordance with Japanese Industrial Standard (JIS Z 0602) was performed. The main results are summarized as follows: The pallet weight became small in decreasing the number of sheets of the top board and the difference of the weight was about 6 kgf (20%). The bend rate in the bending test for each type pallet was smaller than 2.5% of the standard value of JIS. The residual bend rate in the bending test for each type pallet was also smaller than 0.5% of the standard value of JIS. Therefore, it was confirmed that the condition as the pallet of both the bend rate and the residual bend rate was cleared. In each type pallet, the condition as the pallet in the change rate of the diagonal length in the fall down test was cleared because the change rate of the each value was smaller than 3% of the standard value of JIS. The remarkable difference of the withdrawal strength of each type pallet in the pull–out test for the staggered connections using sugi compressed dowel was not recognized. Moreover, it became clear that approximately 56 minutes in manufacturing process of one pallet can be shortened and the manufacturing cost can be decreased because four top boards of the backside of the pallet were decreased.