Writing is one of the main tasks humans do in their everyday life. Although nowadays robots can perform very complex actions such as sorting, transporting or lifting, they are not specialized in writing, both from the hardware and software points of view. Moreover, the cost of most existing robots make them completely unaffordable for most people. In order to solve this gap, we present a whole methodology for the development of a low-cost 3 degrees of freedom robot arm able to write in an arbitrary 2D plane. First, a low-cost structure consisting of three modules with attached servomotors is designed and tested. Then, the robot is kinematically analyzed and the resulting model is embedded in a microcontroller that drives the motors based on references in the Cartesian space of the end effector. In our system, the end effector is a tool such as a pen, pencil or marker properly attached to the mechanical structure. The main novelty of the approach consists in specifying the reference as plain text at the highest level. Each recognized character is then converted to a set of Cartesian points based on adequate geometric trajectories and aesthetically respecting the character proportions. The whole system was developed through digital simulation and later implemented on a prototype.