... only of stand-alone units but also FA systems Therefore, besides the development of special-purpose 392 10 Design of PC-NC and Open CNC systems by modularization of system components and standardization ... provided by CNC makers depend on the CNC makers and are expensive To solve these problems, standardization and openness are required 10.5 Open -CNC Systems 391 of CNC system exists for one kind of machine ... architecture of closed CNC systems could not meet the user’s requirements and improvement of CNC systems was possible, not by MTB (Machine Tool Builders) but CNC makers The limited resources of CNC makers...