Computer aided design for work injury elimination in production assembly systems

Work injury is one of the major obstacles in manufacturing industries especially in production assembly systems all over the world. Work injuries reduce production efficiency and threat human health. Among various types of work injuries, repetitive work injuries are the one that can be easily neglected. This thesis is about the application of computing technology to analysis and synthesis of repetitive work injuries in production assembly systems for the purpose of reduction or elimination of these injuries. A production assembly system consists of the assembly machines, products, tools, humans (workers), and particular environments. Injuries of the worker are basically caused by over stress, strain, and fatigue, which are further related to the worker’s posture. This research proposed a general methodology for constructing a software system for analysis and simulation of a worker’s postures in a virtual environment. The implementation of such a computer system was discussed. This research also proposed methods to compute work injury cost. Finally, this research proposed a more systematic method for the synthesis or re-design of worker’ postures to reduce or eliminate work injuries. The major contribution of this thesis work is to advance computing to work injury analysis and synthesis in production systems. This thesis study concludes that the computer technology is matured enough to highly automate the process of work injury analysis and synthesis. It is possible that a complete design of production systems with consideration of work injuries can be done in a much more efficient manner – perhaps reduction of the ramp-up process in the automobile industry from 6 months (typically) to one month in addition to the removal of wasted materials and potential injuries in the ramp-up process

A general computer-based methodology for work injury analysis in a production assembly line

Repetitive injuries have been a major obstacle in production assembly lines all over the world. These injuries have greatly reduced the production efficiency of assembly plants and also negatively affected human health. Various attempts have been made by the Canadian government through the Worker’s Compensation Board (WCB) to prevent the occurrences of these injuries because of the associated cost and effects. These attempts failed as the cost of injuries acquired in the workplace continues to increase. For example, in New Zealand alone, the total cost of accidents in 2005, is estimated at $300 million (Accident Compensation Corporation, 2005). In Canada, the number of accepted claims alone amount to 15623 people (Workers Compensation Board of Canada, 2003).A human body can be viewed as a mechanism that is composed of links and joints controlled by a central nervous system and are subject to stress, strain, fatigue and failure as can be observed on a regular industrial robot. But unlike the robot which is designed proactively, these stress and strain factors could be because of certain conditions such as inappropriate work posture, poor assembly line design, excessive workload, and poor work conditions. Often, it is almost uncertain to make a conceptual assessment of the appropriate ergonomic design of a production system before the assembly line is built and put in use. This research will propose a general computer-based methodology for analysis of work injuries given an assembly line where human workers perform repetitive operations. The general methodology integrates sophisticated computer software systems for biomechanics simulation with various manual measurement techniques and methods. The research further proposed a simple and handy synthesis method with which problematic areas of assembly line design, with special reference to human work design can be identified and improved. The proposed methodology for analysis and synthesis is then implemented in a real assembly line to understand the effects of different work activities on the human body. Various software packages and motion tracking techniques will be considered prior to the actual implementation of the final methodology. A rule of thumb table will also be presented as a guideline for the re-design process. The research also proposed a general procedure and specific formula within a specific regional context to calculate the costs of worker injuries in real-life assembly system. This formula thus allows us to obtain the total cost of injuries in a production assembly line, making it possible to optimize the design and operation of the assembly line