Enabling feedback of process data by use of STEP-NC

Abstract

Today's computer aided process planning (CAPP) systems are performing NC programming with insufficient consideration of real machine capabilities and resulting workpiece characteristics. Computer numerical controls (CNCs) receive no information about actual workpiece characteristics and applied manufacturing processes. Machine and process observations are not closely coupled to the actual executed machining workingstep. STEP-NC addresses these problems by aiming at the availability of higher information content in CNCs. In this paper, a generic approach to preprocess and feed back process data from servo drives to CNCs and CAPP systems is presented. This approach rests on the application of open digital servo drives in machine tools and the design of application-dependent algorithms to process and exchange drive signals for both, online and offline optimization of machining processes. The effects of the proposed methodology on design characteristics of open servo drives and CNC kernels as well as on the data interfaces and communication protocols between their modules and CAPP systems are focused on in this paper. The methodologies in this paper are exemplified by their application to drive-spanning process force reconstruction.

Keywords:

• CNC
• Servo drives
• Observer theory
• Process force reconstruction