Sometimes in the manufacture of wooden structuresit is necessary to bend the workpiece (usually a board), giving it curved. Do this in the usual way by means of the application of mechanical force will not succeed, because the possible fracture of wood in the intended place of the fold.
To bend the board will have to consider some tricks.
For the manufacture of the curved partswood used two main ways: cutting out the pattern and pre-steamed wood gnutё using a template on a special machine. The first way leads to cutting of fibers and reducing the strength of parts. Gnutё also provides a high percentage of useful output of parts and considerable strength. Bent parts can finish with high quality and are subjected to various machining (profiling, forming studs, eyelets, etc).
The ability of a wooden plank to Bentdefined plasticity of wood depends on the wood species. Beech, birch, oak, pine and spruce have the greatest plasticity. But you can control the properties of the plastic blanks, carrying its hydrothermal treatment.
At a temperature of 100C and a humidity of 30% proportionsubstances contained in the material cells becomes gel state, wherein the cell walls and wood fibers are flexible and soft. This wood is easy to bend. After drying, the board retains bent to give it shape, as colloidal substances solidify.
workpiece handling it is provarivaniyain hot water or steaming with saturated steam of low pressure. Steaming is more common, because in such a treatment timber warms evenly, there is no excessive moisture of the wood.
When treated in this way the board is bentpatterns on or in a special jig, the material having internal stresses. Wood is stretched on the convex side and compressed on the concave. The medial layer of neutral voltage is zero.
The outer layer is under tensilereceive elongation stress and the inner become shorter. amount of deformation depends on the thickness and bending radius docks. To limit extension of wood fibers and their possible to prevent a gap with the convex side of the bent parts of the splint applied to steel 2.5 mm thick. The preform is bent together with the tire. In this neutral line goes in the direction of the fibers stretched beyond the board, and the bending occurs only due to compression.