Comparative evaluation of three-way mortise-and-tenon joint designs considering mechanical strength and machinability

It is still a challenge to manufacture traditional three-way Zongjiao mortise-and-tenon joints using modern CNC-based machines. This study aimed to improve the structure of the Zongjiao mortise-and-tenon joint, a commonly used three-way corner joint in wood furniture, to better align with modern manufacturing practices. First, four improved mortise-and-tenon joint types were designed, and their appearances were evaluated. Secondly, mechanical tests and numerical analyses were conducted to compare the four improved types and two previous types using bending strength and load difference ratio (DR) between the two horizontal members of the joint. Subsequently, the machinability of all types of joints was evaluated through processing time (PT), cutting force (CF), and number of effective programs (NEP). The results showed that the maximum bending strength of the Zongjiao M-T joint was observed in Type D, and the load DR between the two horizontal members was 13,79. The improved Type D has the lowest milling CF of 182 N and the minimum PT of 32 minutes with the least NEP. Through a comprehensive analysis of all the above indices evaluated, it was found that the improved Type D of Zongjiao mortise-and-tenon joint was superior to others, considering appearance, mechanical strength, and machinability. This study provided a paradigm for optimizing wood furniture joints, which can also be applied to other wood products.