The control of a manufacturing machine, modeled as an integrator with input saturation, is studied. An unknown demand must be tracked. A proportional feedback controller with reduced-order observer is proposed. This controller guarantees uniformly convergent system behavior in the presence of input fluctuations and external disturbances. The performance of the continuous system is considered in frequency and time domain. It is described how the controller can be implemented in discrete-event setting, and simulation results show that the proposed controller can be used to control a discrete-event model of a machine.