The end distance effect of knock-down furniture fasteners on bending moment resistance of corner joints

SIMEK, M., HAVIAROVA E., ECKELMAN C.: The end distance eff ect of knock-down furniture fasteners on bending moment resistance of corner joints. Acta univ. agric. et silvic. Mendel. Brun., 2008, LVI, No. 2, pp. 203–210 The goal of this paper is to investigate the eff ect of the end distance of cam lock fasteners on the bending moment resistance of knock-down corner joints. The preliminary study of knock-down furniture assembly plans was done in order to discover the manufacturers’ fastener typical usage in case construction. Laminated particleboard, cam fasteners and wooden dowels were used for specimen construction. L-shaped joint specimens 760 mm in length were tested by pressing the joint members together – also called a compression test in the angle plane. The study results showed that cam fasteners with end distance of 60 mm from the member edges perform the best. bending moment resistance, corner joint, end distance, cam fastener, wooden dowel The joinery for knock-down furniture has been developed and used for almost half century. A large variety of connectors for knock-down furniture exists, including cam locking types, screw in types (e.g. confi rmat, trapez), bolt tightening types (e.g. cross dowels), bracket types, hook types, and dowels used without glue. The mechanical strength of furniture depends mostly on the strength of the joints. Several investigations have been carried out on knock-down fastener joint strength. Among the most important ones are following studies. Smardzewski and Prekrad (2002) studied the stress distribution in knock-down furniture joints by means of experimental testing along with numerical simulation. They tested three diff erent joints (one cam type – VB36M/19 and two trapez types – TZ28 and TZ32S) in combination with two non-glued beech dowels (8x32mm). Their joint corner samples were made out of particleboard. The trapez joints performed the best in the tests. Results showed that the non-glued dowels played an important role in supporting the joint. Numerical simulations determined the distribution of stress in the joints and the bending moment carried by each fastener. Joscak and Cernok (2002) tested the load ca paci ty of knock-down furniture joints made from laminated particleboard (18mm thick). Four types of corner joints (confi rmat type, cam type Rafi x, trapez type, and Stabilofi x) were tested in angle plane by pressing the members of the joint together, Fig. 4, and by pulling them apart. The confi rmat type joint performed the best when pressed together. Joints constructed with the Rafi x cam type connector had the lowest moment in compression. Burdurlu et al. (2006) determined the most suitable type of fi tting for the assembly of knock down panel furniture. In his study he used six knockdown furniture fi ttings (two cam types, metal locking type, trapez type, bracket type and pipe type). The direct labor, direct material, direct energy cost, and stopwatch assembly work time in construction of the furniture were observed. Cam fasteners were determined to be the best for knock-down furniture assembly because of the shortest assembly time. Even though cam fasteners cost more, they save labor time in the assembly process, which is one of the cost liest operations in furniture factories. For this reason, cam fasteners are the most used by knock-down furniture manufacturers. The advantage of cam fas te ners for customers is easy assembly without the use of special tools. The low load ca pacit y of cam fas te ners is augmented by the use of non204 M. Simek, E. Haviarova, C. Eckelman glued dowels because unglued wooden dowels can greatly increase joint load capacity at a lower cost than the addition of cams.