Assessment of Workload, Fatigue, and Musculoskeletal Discomfort Among Computerized Numerical Control Lathe Operators in Mexico

Abstract

OCCUPATIONAL APPLICATIONS Several manufacturing concerns in Mexico, as part of a broader effort to incorporate advanced manufacturing technology, have replaced traditional machines with those using computerized numerical control. As a result, workers have experienced new levels of workload and fatigue levels that have not been previously investigated in depth. Among a sample of over 400 computerized numerical control workers in Mexico, we found that workload has an important effect on the perception of fatigue. Our results also suggest that sleep hours per night, handled weight, and stature of the workers are variables that must be considered in the design of tasks wherein computerized numerical control lathes are present. These results can be useful for managers and industrial engineers to develop and improve production schedules when computerized numerical control machines are operated.

TECHNICAL ABSTRACT Background: With the introduction of new and more sophisticated machinery—commonly classified as advanced manufacturing technology—industrial workers must increasingly perform both physical and mental efforts, often simultaneously. A typical case is the operation of computerized numerical control lathes. This type of work has not been thoroughly studied, particularly in developing countries. In these countries, high workload levels are frequently neglected and the extent of fatigue experienced by operators remains unknown and unaddressed. Purpose: We aimed to assess workload, fatigue, and work-related musculoskeletal consequences; to explore the relationship between workload and fatigue; and to identify differences in workload and fatigue levels related to demographic and work-related variables, among computerized numerical control lathe operators in Mexico. Methods: A cross-sectional, descriptive study was completed, using a survey. Workload was assessed using the NASA Task Load Index. Fatigue was assessed using the Swedish Occupational Fatigue Inventory and the Occupational Fatigue Exhaustion Recovery scales. We examined differences in workload and fatigue items/dimensions related to work and demographic variables, as well as correlations between workload, fatigue, and musculoskeletal discomfort. Results: Survey results had generally high internal consistency and sample adequacy. Workload items with the highest scores were overall effort, mental demands, and physical demands. Fatigue dimensions with the highest scores were lack of energy and physical effort. Chronic fatigue was the fatigue state with the highest score. Significant, positive correlations were found among workload items, dimensions/states of fatigue, and musculoskeletal discomfort. Handled weight and sleeping hours were the factors with significant differences across physical demands, physical effort, physical discomfort, lack of motivation, sleepiness, and chronic fatigue. Conclusions: Factors both directly (e.g., handled weight and sleep hours per night) and indirectly (e.g., demographics) related to workload can contribute to perceived fatigue among computerized numerical control lathe operators. Such results may help in developing effective future interventions.

KEYWORDS:

• Assessment
• mental workload
• physical workload
• fatigue
• advanced manufacturing technology
• computerized numerical control
• operators

CONFLICT OF INTEREST

The authors declare no conflict of interest.

FUNDING

The authors thank the Mexican Council of Science and Technology (CONACYT) for the support provided during this research (project 261218 for sabbatical and postdoctoral grants).