Cutting forces should be kept constant during machining operations to prevent changes in spindle speeds or work position. Such changes would deteriorate the accuracy of the work's dimensions. A control system is proposed to control the cutting force. The plant is difficult to model, since the

Cutting force control system (Reprinted with permission of ASME.) factors that affect cutting force are time varying and not easily predicted. However, assuming the simplified force control model shown in Figure P6.16, use the Routh-Hurwitz criterion to find the range of K to keep the system stable (Rober, 1997)

Actual force Plant Controller Desired 60x 106 CO) force R(s) + (s+30)(s+140)(s+2.7)