This paper deals with the development of an open-loop controller implemented in the Arduino platform in order to reuse an existing CNC machine for performing simple manufacturing operations. The CNC machine considered in this study is an Objet Quadra Tempo 3D printer. The goal of this work is, therefore, to convert the machine, considered obsolete due to high maintenance costs, by using low-cost off-the-shelf components and by using open source software in order to reduce the amount of electronic and industrial wastes by means of simple retrofitting operations. To control the drivers of the stepper motors of the machine, an ArduinoMega 2560 microcontroller was used. The Arduino micro- controller allows for controlling analog and digital devices in a straightforward manner. All retrofitting operations were conducted in order to carry out additive manufacturing and subtractive manufacturing operations. For the activity reported in this paper, an electro-spindle for machining products in wood and polycarbonate was installed. The use of low-cost components allowed the transformation of the 3D printer into a CNC milling machine capable of working materials such as wood and polycarbonate.