Development and evaluation of the machining performance of a CNC gantry double motion machine tool in different modes

Conventional methods of building CNC machine tools involve using linear motors and ball screw drives to obtain table motion. The double opposite sync motion design is an improvement over traditional CNC machines. In this work, an enhanced CNC gantry machine design is proposed, which exhibits a double motion mechanism. The new design is based on a rack and pinion system such that both the gantry tool and worktable are movable. The gantry's natural frequency was designed at 202 Hz in the first vibration mode, enabling it to work at higher speeds of up to 11,530 rpm, which makes the gantry suitable for both rough cutting and fine finishing. A prototype of the multi-mode motion CNC gantry milling machine was developed to investigate the machining performance and efficiency of the double opposite sync system. Performance analysis was done using ball bar precision tests on the different modes of CNC gantry operation. Validation tests were carried out to determine the effects of the motion of the machine parts on the dimensional accuracy and surface finish of the machined parts. The results indicated that the straightness of the developed machine was reduced from 176.3 to 114.6 μm, which occurred due to the reduced total distance travelled by the tool and worktable. Moreover, the circularity increased from 338.7 to 667.0 μm. This increase could be attributed to the combination of errors arising from both the gantry and table.