A major challenge for manufacturing companies today is to manage a huge amount of product variants and build options at the same time in manufacturing engineering and in production. The overall ...complexity and risk of quality errors in manual assembly will increase placing high demands on the operators who must manage many different tasks in current production. Therefore, methods for decreasing and controlling assembly complexity are urgent because managing complex product and installation conditions will result in distinct competitive advantages. The objective of this paper is to present a method for predictive assessment of basic manual assembly complexity and explain how included complexity criteria were arrived at. The verified method includes 16 high complexity and 16 low complexity criteria to aid designers in preventing costly errors during assembly and create good basic assembly conditions in early design phases of new manufacturing concepts.
The objective of this study was to examine to what extent ergonomics simulations of manual assembly tasks correctly predict the real outcomes in the plants and if recommended measures originating ...from ergonomics simulations are taken into consideration. 155 ergonomics simulation cases were used in the study and all cases were performed by nine simulation engineers at Volvo Car Corporation in Gothenburg. The evaluations of the ergonomics conditions of the simulated tasks were done by six professional ergonomists working at Volvo Car Corporation in Gothenburg. The results show that digital human modelling tools (DHM-tools) are useful for the purpose of providing designs for standing and unconstrained working postures. Furthermore, the design of various auxiliary devices and their needed space for movements is a prevalent use of DHM-tools. However, the study also identifies areas that require additional development in order to further improve the digital human modelling tools' possibility to correctly predict a work task's real outcome, i.e. hand access, push pressure and pull forces, leaning and balance behaviour and field of vision. Moreover, a better feedback of product and process changes and a more careful order description of simulation cases to the simulation engineers would lead to improved simulation results in current and future projects.
DHM-tools are increasingly the major means used to perform ergonomics analyses of manual assembly tasks in the automotive industry, but there is still a need for improvements of the tools. It is of great importance to disseminate end users' experiences of the use of different DHM-tools so these can be developed and applied in a more efficient way.
Earlier studies have demonstrated strong relationships between manual assembly at high physical load levels and increased amounts of quality defects compared to assembly at low physical load levels. ...A recent Swedish interview study of engineers in design and manufacturing engineering indicated that assembly complexity factors are of additional importance for the assembly quality. The objective of this study was therefore to examine the significance of high and low complexity criteria and the relationships between assembly ergonomics and assembly complexity and quality failures by analyzing manual assembly tasks in car manufacturing. In total, 47 000 cars were analyzed and the results showed several significant correlations between assembly ergonomics and assembly complexity, assembly time, failures and action costs. The action costs for high complexity tasks were 22.4 times increased per task per car compared to low complexity tasks.
Assembly ergonomics and assembly complexity factors interact. Both should be proactively considered in order to keep assembly-related failures and action costs as low as possible.
•A model for assessment of assembly complexity in manual assembly was developed.•The higher the level of complexity, the more errors will occur.•Assembly ergonomics and complexity are interrelated. Both affect the failure rate.•The highest complexity level resulted in 22 times increased action costs/task/car.
Increasing design and assembly complexity are challenges facing the automotive industry today because increasing number of car variants and build options can result in immense difficulties and lead ...to costly assembly errors and quality losses. In order to remain on the market these conditions must nevertheless be managed by companies in hard competition with other manufacturers.
The objective of this study was to analyze the impact of newly developed basic complexity criteria (CXB) on assembly quality and associated costs for corrective measures in manual assembly of cars. Data on error rate and action costs of assembly tasks of different complexity level was collected and analyzed. The inter-relationship between different complexity criteria was analyzed to see whether any criteria had a greater impact than others.
The results showed that the action costs/car increased with increasing complexity level and that several complexity criteria together resulted in increased action costs. Some criteria tended to have a greater impact than others but need more research. The results further suggest that if high complexity issues are identified and replaced by low complexity solutions the assembly related action costs in manual assembly are likely to decrease.
By reduction of basic assembly complexity already in early planning stages in product development significant reduction of costly assembly related action costs in manual assembly can probably be made.
•Strong relationships shown between basic assembly complexity and action costs.•The higher the basic complexity level the higher were the action costs/car.•Several basic complexity criteria together affected error rates and action costs.•Reduction of high complexity issues could result in much reduced action costs.
This paper presents the development of an adaptive linear regression model for synthesizing of missing anthropometric population data based on a flexible set of known predictive data. The method is ...based on a conditional regression model and includes use of principal component analysis, to reduce effects of multicollinearity between selected predictive measurements, and incorporation of a stochastic component, using the partial correlation coefficients between predicted measurements. In addition, skewness of the distributions of the dependent variables is considered when incorporating the stochastic components. Results from the study show that the proposed regression models for synthesizing population data give valid results with small errors of the compared percentile values. However, higher accuracy was not achieved when the number of measurements used as independent variables was increased compared to using only stature and weight as independent variables. This indicates problems with multicollinearity that principal component regression were not able to overcome. Descriptive statistics such as mean and standard deviation values together with correlation coefficients is sufficient to perform the conditional regression procedure. However, to incorporate a stochastic component when using principal component regression requires raw data on an individual level.
When developing products, workplaces or systems, it is of great importance to consider the anthropometric diversity of the intended users. The proposed regression model offers a procedure that gives valid results, maintains the correlation between the measurements that are predicted and is adaptable regarding which, and number of, predictive measurements that are selected.
•A regression model for synthesizing anthropometric population data is presented.•Predictions of missing data based on a flexible set of predictive data are made.•The model includes use of principal component analysis.•Partial correlation coefficients are used to incorporate a stochastic component.•Predicted result based on sample size and predictive measurements is evaluated.
The work activities of industrial engineers (IEs) and ergonomists drive workplace changes. The purpose of this study is to compare the work practices of the two professions and examine (1) how IEs ...and ergonomists gain influence over workplace changes and (2) whether there are prevailing types of intentional interaction behaviours called Power bases (PB) present in the interaction tactics they employ. The study identified key behavioural strategies used by the interviewees to successfully influence workplace changes; these were then mapped to their corresponding PB. Results showed that IEs and ergonomists were successfully influencing workplace changes using several tactics across the spectrum of PB, with the exception of Reward and Coercion. The study concludes with a list of recommended workplace change agent tactics, and proposes that a PB 'analytical lens' can serve to increase the budding ergonomists' critical and analytical skills when considering possible workplace change tactics.
Practitioner Summary: This interview study examines how workplace ergonomics change agents, represented by the two professions: industrial engineers and ergonomists, perceive and exercise their capacity to influence workplace change. Key behavioural tactics that interviewees have found successful are reported, alongside effects on short- and long-term relations with other workplace-influencing stakeholders.
Tough competition force companies to develop and increase their product assortment in order to maintain their market share. This has resulted in numerous product variants with more features and build ...options. The complexity and risk of quality errors will increase. Managing complex product and installation conditions will result in distinct competitive advantages. Research has shown that sustainable and more cost-efficient assembly solutions can be obtained by proactive improvement of the working environment and installation conditions for the operators. Significant reduction of costly corrective measures can be made. The objective of this paper was to demonstrate criteria for proactive assessment of manual assembly complexity, which have been developed and verified in several studies. A further objective was to clarify and quantify included criteria as far as possible to enable a more general application in manual mass production of complex products.
The objective of this study was to investigate whether the appearance of virtual human models influences observers when judging a working posture. A task in which a manikin is manually assembling a ...car battery was used in the experiment. In total, 16 different pictures were presented to the subjects. All pictures had the same background, but included a unique posture and manikin appearance combination. 24 subjects consisting of manufacturing managers, simulation engineers and ergonomists were asked to rate and rank the pictures. The results showed that the virtual human model appearance influenced subjects when they rated pictures one by one: a more realistic manikin was rated higher than the identical posture visualized with a less natural appearance. This appearance effect was not seen when subjects ranked the pictures while looking at all of them at the same time. The study demonstrates that the human modelling tool used when showing and visually evaluating results makes a difference. To minimize subjective effects, a combination of visualizations and objective ergonomic assessment methods is recommended.
In this article, two field experiments, conducted in an automotive assembly plant, evaluate how computer‐based training of operational sequences and related quality information can support the ...assembly performance of the operators. The experiments were performed during the launch of a new vehicle. A comparison was made of learning progress and quality performance between a reference group of operators that only had regular training and a test group for which some of the regular training was replaced with individual computer‐based training. Both quantitative measures of the quality output and questionnaires and observations were used to evaluate the effects of computer‐based training. The results show a clear positive difference in learning progress and improvements in quality output for the test group compared with the reference group. This combined with positive attitudes expressed by the operators and their team leaders shows that this type of training is an effective way to train operators during launches of new vehicles in automotive production.
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