Research On The STEP-NC-based CNC System

This contribution has investigated applying STEP-NC standards to open CNC system, and then demonstrated the feasibility of the research turnouts.The open CNC system consists of an upper PC and a lower DSP (Digital Signal Processor). The PC takes charge of the converting STEP-NC into G code and transferring G code to DSP module through USB2.0 interface. The lower DSP (TMS F2812) is used to realize the interpolation and control of three axes for the retrofitted CNC milling machine equipped with SIEMENS servo drive amplifiers and AC servo motors.The main focus of the work is the method of converting STEP-NC code into G code, which includes the analysis of STEP-NC standard file's structure and content, the rules of extraction of important machining information, the recognition of class features, the rules of tool path's generation and the method of final converting to G code. The second part of the research is the method of data transferring based on USB2.0 in CNC system. USB links the upper PC and the lower DSP by programming the windows driver on PC and firmware on DSP. Finally the end-user interface is developed with MFC in VC++ environment, which can transfer data and display the axes locations on-line.The experimental results have demonstrated that the converted G code from STEP-NC can be fully transferred to the retrofitted CNC milling machine for execution. The developed USB driver works well and the human-machine interface is carefully arranged and thus is friendly. All work in the paper forms a sound base for the coming research activities thereafter.