Development Of On-Machine Measurement Software Based On Sinumerik 840D

The machining center as an important role in the modern manufacturing industry,only has the rich processing function has been unable to meet the needs of modern production,which has functions of measurement has become a development trend of modern machining center.The traditional measurement method will lead to the second fixture positioning errors,and the efficiency is low.Therefore,on machine measurement technology is put forward,in which the workpiece is installed on the worktable,and the tool is replaced by the probe to measure.It not only makes use of the automation and high precision of NC machining center,but also avoids the influence of non-coincident datum on measuring accuracy.Moreover,on machine measurement is convenient to measure the process,detect the error in the process in time and amend it quickly.The machining center integrated with on machine measurement function can reduce waste,save cost and shorten machining cycle.Aiming at the five axis milling machining center equipped with SIEMENS 840D CNC system and infrared trigger probe,the overall scheme of the measurement system is confirmed.Analysis of the machining center working range,motion error and data acquisition frequency of NC system and other parameters,and the principle of trigger probe was studied,determined the measurement project.According to the working characteristics of trigger probe,the general principle and influencing factors of sampling point selection in triggered measurement are summarized.The deficiency of equal parameter method in the sampling point selection of free-form surface is analyzed emphatically,and the sampling strategy based on surface quality is proposed.It lays a theoretical foundation for automatic generation of machine measurement code.The architecture and related interface of SIEMENS 840D CNC system are studied.Based on the previous theoretical research and on sequential control principle and dynamic data interaction protocol,,using VB6.0 and VC++6.0,on machine measurement software was completed in SIEMENS OEM-HMI development environment.The automatic generation of measurement program,the mutual communication with NC system,the post-processing of data and the output of measurement report are realized.In order to further improve the accuracy of computer measurement,the formation principle and compensation algorithm of errors in computer measurement are studied.According to the structural characteristics of the trigger probe and the process of the measurement in the machine,the formation principle of the pre-trip error and the probe radius compensation error in the machine measurement is analyzed.According to the probe radius compensation error of the regular surface and the free surface,the corresponding compensation algorithm is given.The steel pipe straightness on machine measurement experiment,free surface profile on machine measurement experiment and Butterfly model processing and measurement experiment,to compare OMM data with the three coordinate measuring data verify the accuracy of the machine measurement results and practical value.And the machine measurement software has been modified and transplanted to the three coordinate measuring machine,which broadens the application scope of computer measurement software.