In a case of SL50 CNC lathe,the work of the plastic coated guide rail on the inclined bed is analyzed. A variety of factors affecting straightness of the plastic coated guide rail on inclined bed are analyzed. The past and now known or unknown the information of straightness of the plastic coated guide rail is regarded as a GreySystem. Regular testing straightness error value by laser interferometer is constituted as an original data series at equal intervals. The mathematical model of gray system is establ...