Investigating assembly complexity is a continuing concern within manufacturing field, as it may impact quality and costs of products. There is a growing body of literature aimed at developing novel and reliable methods to assess assembly complexity. The first aim of this paper is to provide an extensive literature review, identifying the main approaches to this problem. Three main approaches emerged: product-centred approach, information-centred approach and system-centred approach. A second goal is to carry out a comparative analysis of these approaches highlighting their advantages, limitations and providing guidance for process and product designers seeking to control assembly complexity. For each approach, a representative method was chosen, analysed in detail, and applied to three different real products.

Human–Robot Collaboration (HRC) represents an innovative solution able to enhance quality and adaptability of production processes. However, to fully exploit the benefits of HRC, human factors must be also taken into account. A novel experimental setting involving a repetitive assembly process is presented to investigate the effects of prolonged HRC on user experience and performance. Each participant was involved in two 4-h shifts: a manual assembly setting and a HRC one. The response variables collected in the study included self-reported affective state, perceived body discomfort, perceived workload, physiological signals for stress (i.e., heart rate variability and electrodermal activity), process and product defectiveness. Experimental results showed less upper limb exertion in the HRC setting, emphasizing the contribution of cobots in improving physical ergonomics in repetitive processes. Furthermore, results showed reduced mental effort, stress, and fewer process defects in the HRC setting, highlighting how collaborative robotics can improve process quality by supporting operators from a cognitive point of view in repetitive processes.

Human-Robot Collaboration (HRC) represents an innovative solution able to enhance quality and adaptability of production processes. In a collaborative process, man and robot cooperate symbiotically. However, to fully exploit the benefits of HRC, human factors must be taken into account. A novel experimental setting involving a repetitive assembly process is presented to investigate the effects of prolonged HRC on user experience and performance. Each participant was involved in two 4-hours shifts: a manual assembly setting and a HRC assembly setting. The response variables collected in the study include the perceived workload, self-reported affective state, perceived body discomfort, physiological indicators of stress (heart rate variability and electrodermal activity), and process defectiveness. The experimental results showed reduced mental effort and fewer process defects in the HRC setting, highlighting how collaborative robotics can also support humans from a cognitive point of view.

Assembly complexity assessment is a widely addressed topic in manufacturing. Several studies proved the correlation between assembly complexity and the occurrence of defects, thus justifying this increasing attention. A measure of complexity provides control over quality costs and performances. Over the years, many methods have been proposed to provide an objective measure of complexity. One of the most widely diffused is the so-called MCAT (i.e., “Manufacturing Complexity Assessment Tool”) modified by Samy and ElMaraghy H. for assessing product assembly complexity. Although this method highlights some interesting aspects, it presents some critical issues. This work aims to thoroughly analyse this method, focusing on its strengths and limitations.