In this paper, a 3D printer-like data interface is proposed for the machining robot. The 3D data interface enables to control the machining robot directly using STL data without conducting any CAM process. This is done by developing a robotic preprocessor that helps to remove the need for the conventional CAM process by converting directly the STL data into CL data. The STL originally means Stereolithography which is a file format proposed by 3D Systems, and recently is supported by many CAD/CAM softwares. The STL is widely used for rapid prototyping with a 3D printer which is a typical additive manufacturing system. The STL deals with a triangular representation for a curved surface geometry. The developed interface allows to control the machining robot through a zigzag path generated according to the information included in STL data. The effectiveness and potential of the developed approach are demonstrated through actual experimental machining results.