In this study, the automation of an assembly process using a collaborative robotic arm (Cobot) was analyzed. The manual process is the assembly of a Lego® bricks structure and was analyzed using the technique of predetermined movements MTM-1. Moves were defined and processing time was set. The results obtained show that the automated process can increase production capacity by up to 40% using the same personnel as the manual process, but in different shifts. Likewise, defects due to a bad union between the edges of the bricks, which is the main problem in the manual process, are avoided. Finally, the automation process was detailed by associating the manual movements with the Cobot® commands in the simulation environment of the PolyScope Robot User Interface®. What has application to automate other types of manufacturing sequences and manual assemblies. Keywords: Automatization, Robotic arm; Methods-Time Measurement; Cobot®; Lego® bricks.