Abstract:
Productivity and precision in machining is normally limited by the forces emanating from the cutting process.
Due to the inherent varying nature of the work piece in terms of geometry and material composition, the peak
cutting forces vary from point to point during machining process. In order to increase productivity without
compromising on machining accuracy, it is important to control these cutting forces. In this paper a fuzzy logic
control algorithm is developed that can be used to limit maximum peak forces in milling of spherical surfaces
using ball end mills. The controller can adaptively maximise the feedrate subject to allowable cutting force on
the tool, which is very beneficial for a time consuming complex shape machining. This control algorithm is
implemented in computer numerical control (CNC) machine. To demonstrate constant peak force control, the
radial depth of cut was abruptly changed from 1.0 to 1.5 mm. As a result, the peak cutting forces increased. In
order to counteract this increase and maintain a constant peak force, the pre-programmed table feed was
decreased by assigning the appropriate override. For the above change in depth of cut, the override was found
to be about 78%, which is a drop of table feed from 30 mm/min to 23.4 mm/min. It has also been
demonstrated that the controller developed can provide stable machining and improve the performance of
the CNC milling process by varying feedrate in real-time.
