Study On Chip Formation In The Nodal Zone In Bamboo Cutting

Nowadays, with the increasing utilizations of bamboo resources, especially in the means of bamboo composites, the phenomena in machining bamboo are paid more and more attention, in which bamboo cutting is one of the most important parts. Some new problems appear in bamboo cutting, and they are often different from what are met in wood cutting. Therefore it is urgently needed to develop research on the fundamentals of bamboo cutting. In this paper, piezoelectric pressure indicators are applied to measure the cutting forces in bamboo cutting, and the cutting processes are recorded using CCD camera. Then the relation between cutting forces, chip deformation and chip types are analyzed. Test specimens in the nodal zone and the internodal zone are made from both carbonized bamboo and normal bamboo. Experiments are arranged in groups according to the three different cutting directions: 90-0,0-90,90-90(in each direction, experiments are further developed in two different grain directions: tangential and radial direction). In each group, Orthogonal Latin Spare table is used to arrange the experiments, so that the influences of the factors of cutting depth, moisture content of bamboo and rake angle of knife on the chip formation could be studied. In 90-0 and 0-90 cutting, three different chip types can be gained respectively, however, in 90-90 cutting only two chip types can be gained. To explain the principle of the chip formation in the above 3 cutting directions, the model of quasi-equilibrium beam is adopted. The fundamentals of chip formation in the 3 cutting directions are developed to estimate what type of chip will be formed given cutting forces measured in the cutting process. With the same cutting parameters, same chip types can be gained in either the nodal zone or the internodal zone. In other words, the principles of chip formation are entirely the same in these two different zones. However, as the result of the particularity of the arrangement of vascular bundle in the nodal zone, in some cases, the cutting forces, chip form and the quality of the machined surface would be different from the internodal zone. After carbonization, some mechanical properties of bamboo would be weakened, however, this does not influence the chip formation of the treated bamboo. The cutting forces in cutting the carbonized bamboo would be less than cutting the normal one, and the surface quality would become worse in some degree. Most of the mechanical properties of bamboo are almost the same in tangential and radial direction, same chip types can be gained in these two different cutting directions, and there are also no differences in the cutting forces between the two different directions. In the cutting experiments in the 3 different cutting directions (90-0,0-90 and 90-90), cutting depth has the same evident influence on the cutting forces, and the cutting forces will increase with the increase of cutting depth. In the cutting experiments in these 3 different cutting directions, moisture content of bamboo also has the same evident influence on the cutting forces, the cutting forces will increase when the moisture content increase from absolutely dry to equilibrium moisture content, however, cutting forces will decrease when the moisture content increase from equilibrium moisture content to saturated moisture content. In the cutting experiments in the 3 different cutting directions, rake angle of knife does not have notable influence on the cutting forces.