We consider a flexible manufacturing cell composed of several parallel machines and a material handling robot. The robot is responsible for material transportation between the input/output buffers and the machines as well as loading and unloading of these machines. The system produces multiple parts. The part input sequence, the sequence of robot's transportation and loading/unloading activities, and the speed of the robot in these activities are the decisions of the problem. These decisions affect both the production rate and the energy consumption during the moves of the robot. The objective is to complete the production of the parts within a given time limit with minimum energy consumption. We develop a mathematical programming formulation and test its performance with a computational study. We also demonstrate the tradeoff between the production time and the energy consumption through numerical examples.