Plate (platform) of the local error is the plate (platform) face processing quality of local flatness, including micro-processing of face and face a small range of quality local distortion so-called micro-machining is the machining surface quality and minimum spacing small valley roughness, that is, the surface roughness of the surface micro-quality, wear-resistant, flat-panel high life while the face of local small-scale distortion is machined surface is not flat, there is distortion here talking face small range, the small plate (platform), which account for a local position, the large plate (platform) is the local area. flatness reflecting plate (platform) local errors plate stiffness is an important indicator to measure the quality of flat panel in use to withstand a certain load, if the plate stiffness is poor, resulting from the deflection under load, causing a flatness tolerance, will no longer play its due role in the base plane and therefore affect the use of flat-panel stiffness is an important factor in accuracy, requires flat design must ensure that the plate has sufficient stiffness so that the quality of flat panel stiffness is a measure of the important indicators in China and abroad have the indicators included in the flat standard quality assessment project. 
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