Furnace tending is one of the activities within the casthouse which most depends on operators. Due to the large dimensions of melting and holding furnaces, the equipment used for tending, also of large dimensions, is either mobile and operated by humans, or mounted on rails. Robotics integration is limited, because standard robots are designed for high speeds with small payloads, while slow speeds at large payloads are required. To overcome these limitations, a custom robot has been designed, integrating innovative features such as portability (onboard energy supply) and high payload capacity. This paper explains how the various design constraints were overcome by designing a custom geometry for the robot.