In this paper we consider thc problem of optimal control design for off-line programming in educational assembly robotics. After introducing some key features for mechanical, electrical design systems and computer-control and programming of a prototype robot, we discuss the control system and the off-line programming for a case study of educational robotics. We propose a new Dynamic Optimal Time-Energy Trajectography (DOTET) controller based on the complete dynamic model of the robot and which takes into account intrinsic and extrinsic constraints, robot singularities and requirements of the task and the environment. Numerical results are given to demonstrate the efficiency of our design.