Research on life of machine accuracy and precision reliability assessment concerning about a turn-milling combined machine tool

The precision retentivity and reliability of CNC machine tools directly influence the processing quality, productivity and efficiency, and further the market competitiveness and user´s confidences. The machining includes many technological requirements, and any of precision parameters beyond the limit causes the precision fault. The study on precision recession demonstrates that the machine tools in use suffer from mechanical, thermal, chemical energy, and others, via the time varying and uncertain random processes as deformation, abrasion and corrosion, and then the precision worsens gradually. In order to calculate the precision recession theoretically, the machining errors here are divided into manufacturing and installation errors, the deformation errors aroused by load and errors by dynamic vibration in running, the errors by abrasion, the errors by the thermal deformation and so on. All the errors are random variables. Various errors considered, whether the total machining errors surpasses the permissible limit could be measured by the probability. This paper figures out the means and variances of these random errors in some manner, proposes an assessment method for the precision life, and conducts a precession reliability assessment of a turn-milling machine by using this method. Finally, the method gets be compared with application of response surface method.