The AX2550 is built into a aluminum extrusion shaped as a heat sink. Consequently, the controller is able to operate without a fan in most typical applications. In the most demanding applications, the controller may generate more heat than the heat sink is capable of dissipating. In this case, it is recommended to add an external fan that will blow air on the controller's fins. You may also physically bolt the controller to a large metallic chassis of the robot so that excess controller heat dissipates through conduction. Providing additional cooling will allow the controller to deliver higher current for longer periods of time