Students usually have difficulties in understanding threshold concepts related to engineering subjects. This problem could be due to the fact that students do not always start the course with the concepts from with concepts belonging to prior subjects assimilated. For this reason, in order to assess this knowledge, several experiences have been carried out, not only to help the students to find out if they are able to deal with the subject, but to improve their knowledge about them. In this paper, the results from the reinforcement of threshold concepts in three subjects of theory of machines and mechanism of different engineering degrees are presented. The subjects involved in the project are “Mechanical Systems and Strength of Materiales” (Bachelor’s Degree in Industrial Electronic and Automatic Engineering), “Mechanics and Theory of Mechanisms” (Bachelor’s Degree in Product Design and Development Engineering) and “Theory of Machines” (Bachelor’s Degree in Industrial Organization Engineering).

A Mechanisms Threshold Concepts Quiz has been designed for the engineering subjects: “Mechanical Systems and Strength of Materiales” and “Mechanics and Theory of Mechanisms, both belonging to the first semester of the third year, to assess the knowledge of the students at the beginning of the year. The proposed tool has been tested during 2022-2023 and 2023-2024 academic courses and these results were compared to those coming from the midterm exams. It is important noticing that during the 2023-2024 academic course some teaching activities have been carried out to palliate the difficulties of students when dealing with the threshold concepts of the subjects. For instance, some exercises were proposed as reinforcement activities (with no mark) that the students can try as many times as needed. The main goal is to check how this kind of activities can improve the overall performance of the students in the subjects.

On the other hand, with the aim of reinforcing the acquisition of fundamental concepts of theory of machines and mechanisms throughout the semester, in the subject “Theory of Machines” five online tests have been designed. Each test consists of multiple-choice questions and short problems. To encourage student participation, the average grade of the online tests stands for the 5% of the course grade. The designed tests have been implemented during the last two academic courses as well and compared to exam grades.

Keywords: Mechanisms, Theory of Machines, Threshold Concept, Reinforcement Activities.