Study On The Theory Of Compress-bending Wood And Equipments

Long time ago, people found that timber could be bended with the fire shining. With the development of living condition, the bending woods were applied to the furniture and windows, its processes were filled with more technology. It was applied to the bending wood making that manual bending, mechanical bending and NC bending, and the development of computer technology promoted the bending wood process.In wood bending, the raw material must be selected at first, which was the foundation to the next softening procedure, softening means the timbers were put into the container with high temperature and press ion. After a long time, the timber was plastic; sometimes the ammonia could be used to enhance the plasticizing affection. The high frequency and microwave softening are the new research fields in the science and technology advancement.The bending method was multiplex. It is necessary to multi direction wood bending that partial heating, partial compressing and partial bended, which reduced the trouble of joint and agglutination, enhanced the appearance quality and duration. To the presser all the world, the precession in bundles was the process tendency, which eliminated press unbalance caused by the defection of single timber. The distribution and press ion in bundles could provide the theory foundation in the industrial production.Whether manual bending or mechanical bending, the tools and jigs were necessary, and the steel strap was the key tool in the bending procedure, it made the unchanged layer moving outside, decrease the possibility of outside wood fiber split. In the same condition, the steel strap made the bending radius smaller got great curvature. In this paper, the smallest bending radius of rectangle cross section and round stick were anal sized with the figure, form its variety scope, it was showed that the bending with adjustable end stop could get smaller bending radius than fixed end stop in the steel strap using.With the analysis of bending theory, the position of unchanged layer is the key to bending success. In the analysis of simple bending and compound bending, the position of simple bending's unchanged layer was described; it is connected with two vital parameters, the ultimate tensile strength and ultimate press strength. The great productive ratio was illustrated caused by unchanged layer moving outside with the steel strap. From the analysis of compound bending, it was showed that the density and strength was heightened. During the research of compound bending, traditional compound bending was not fit to the components without certain rotary center or with great various curvatures. The NC compound bending was illustrated to solve this question, and it could connect wood bending with NC technology, which would promote the development bending wood industrial greatly. The mechanical hands bending was combine equipment too, which solved the forming question of multi direction bending wood. It is creative for the multi direction bending wood making. The track design and feed calculation were introduced with example, but the steel strap technology couldn't be applied to the mechanical hands bending, so the smallest bending radius was limited. The mechanical hands were controlled by computer, so the Finite Element Method could be used to analyze the bending shape and stress in the certain condition, which conduced to synthesize the effect of moisture, elasticity and wood species.Contrasting bending and milling to the curve components' process, the bending component was with greater strength than milled component with mathematic description, and the difference in recovery ratio was illustrated too. All above should be valuable to the technology advancement and wood further utilizing in the wood bending corporations.The typical equipment, wood bending hands was initialized in structure. Control system was designed, and illuminated the system's function and characteristics.This thesis comes from the national forestry bureau's "948" project "The Technics and Equipments Importation of Bending Wood with Compressing" and national "863" plan "Robot Product Line for Wood Bending", and supported by them.