ABSTRACT The introduction of robot-assisted automation, such as in machine tending systems for the automated operation of CNC machine tools, is being actively carried out at many industrial sites. The most important part of this intelligent system is the installation of a machine tending system that involves interface programming between the CNC machine tools and the industrial robot. Despite this importance, however, the machine tending system has many setup problems. It must be reprogrammed for both controllers whenever a new CNC machine tool or robot is introduced. Owing to the complex structure of the machine tending system, external engineers are required even though trivial changes have been made. To solve and remove inconveniences, there is a need to introduce a standardized and integrated system of the interface between multi-vendor CNC machine tools and industrial robots. In addition, the digital twin implemented inside the machine tool controller enables external engineers to easily change robot programming. To implement this system, an integrated development environment for: an intelligent platform that provides ISO 21919 interfaces to multi-vendors CNC machine tools, a robot platform developing application software of various robots, has been established.