Research And Development Of CNC Lathe-oriented On-line Inspection System

An automatic on-line inspection system is one of the key technologies to improve the efficiency and accuracy of digitally controlled machining processes. Although the coordinate measuring machine is widely used to improve the measuring accuracy of the manufacture parts, it is however a time consuming process and additional errors are incurred during the additional fixing operations.Developing an on-line inspection system that can be used in practical situations, such as the workshops of manufacturing companies, has been the focus of international research in CNC technology for several years. In this paper, the structure, functions and critical technology of an automatic on-line inspection system for a NC lathe using AutoCAD are discussed. The content is divided into 5 different sections:1. Based on the current development of on-line inspection techniques, the key problems in this field are discussed and the target objectives of automatic on-line inspecting system on NC lathe are presented.2. To meet the requirements of the machining accuracy inspection on a NC lathe, this paper presents a method of how to generate the NC code and plan the inspection paths for simple geometric shapes and free-form curved parts.3. Based on the analysis of the measurement error, the method of how to install and calibrate the probe are described. The problems of thermal deformation and its compensation, where the shape factor are taken into consideration, are described. To work out the straightness error of the motion stage, the method of "Sequential-Two-Points" is also tested during the inspection process.4. On the basis of these studies, a macrocode for outputting the measurement results for the FANUC series of NC machines is developed. Using the secondary development software ObjectARX for AutoCAD, an automatic on-line inspecting system for the NC lathe is developed. The important modules of this system are:the module to generate the NC code, to output the measurements by generated by the macro program, communicating with NC lathe at real time.5. Finally, this system was tested by measuring the coaxial tolerance and flatness error of multi-diameter shaft and free-form curved parts. These measurements where then compared to those obtained by using a CMM. The results show that the system is efficient and accurate.The work described in this paper will be very useful in the further development of an on-line inspection that can be used in practical situations, such as the machine workshops of manufacturing companies.