Dynamic Modeling and Stability Studies on a Retrofitted Drill Spindle Using a Sensor-Based System

For the past decade, very few research had been carried out for the utilization of in-house machines such as the drilling, milling for several applications. For simple machining operations like slotting, grooving, etc., the use of CNC end-milling is a costly concern. This paper presents an optimized modeling concept for drill spindles employed for economical milling practices. To this end, a realistic spindle tool unit of a bench drilling machine is first analyzed to obtain the tool-tip frequency responses by both analytical and experimental approaches. To enhance the use of the drill spindles effectively for end-milling operation, its geometrical topology is modified by adding an additional bearing with a collar system, which improves its dynamic rigidity during the milling operation. Using the Timoshenko beam theory with the rotational and shear deformation affects the tool-tip frequency responses are arrived both numerically and experimentally. Further, a portable X–Y table is also fabricated as per the existing dimensions of the drilling machine to carry out the cutting tests for assessing the stability. Analytical stability lobe diagram is plotted for the modified optimal spindle, and further online detection of chatter during the machining process is identified by the sensors such as the accelerometer and microphone. The data acquisition methodology used in this work confirms the relevance of chatter monitoring at the earliest stages.