| Summary: | In order to meet the needs of CNC machine tools for small industrial workshops or for media learning in educational institutions, a prototype of small 3-axis CNC milling machine using an open loop control system was developed. Because it is an opened loop, the control system is easily affected by outside interference originating from the controller, the disadvantage of the mechanical construction of the machine as well as the effects of the cutting process, so the accuracy of the movement was also affected. The compensation method was developed in this study, to improve the accuracy of the movement system.
Inaccuracy of CNC machining processes caused by a combination of various sources of error and the magnitude can only be known after the machining process done. The experiment is conducted by testing the machining process on the aluminum workpiece with some variation of machining conditions (cutting depth, cutting width and feeding), to identify and modeling the dimensional deviations. Modeling data is used as a reference to compensate the next machining processes, so the error can be reduced, or in other word, the accuracy of system is increased. The results showed that the major source of the error from the disadvantage of the mechanical construction of the machine due to inaccuracy in the design and manufacturing process. The largest error on the machining process proceeds is -0.129 mm for X-axis and +0.042 mm for Y-axis. Compensation method given by modification CNC part program (G-code) and by setting the number of steps per unit stepper motor, can minimize error in X-axis and Y-axis to less than 0.020 mm.
|
|---|