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Ergonomic Improvements of Workstations for Visual Inspection and Electrical Tests in a Multimedia Product Factory
Abstract
Workstations for Visual Inspections (WVIs) and also for Electrical Tests (WETs) of a multimedia product factory were studied from Ergonomic viewpoints. The problems, identified by subjective assessments and direct observations, were related to poor designs of workstations, work processes and improper tools, causing high (12.2 ± 4.1%) product returns. In some WVIs, operators were having visual fatigue due to excessive magnifying glass usage, glare from inspection templates and too many components to check within a very short period. Some WETs were not organised to reduce hands and body motions, and to eliminate confusing criteria for passing or failing of the tests. They also had poor visual projection tests due to too bright ambient illumination on the screen. The Ergonomic improvements were: the reduced usage of magnifying glass, the use of no-glare templates, visual inspection of only the electrically non-tested components, the re-design of WETs for economy of motion, the improvement on pass or fail criteria, dark space for effective visual projection tests, etc. These ergonomic interventions improved the company's productivity and operators' health, reduced the product returns and saved USD 70,900 per month.
... The present research was a part of a series of ergonomics studies in PCA factories in Malaysia, an industrially developing country (IDC), with the purpose of helping the industry (which is one of the biggest industries in the country) to improve quality, productivity and OHS [13,14,15,16,17,18,19,20,21,22]. The preliminary results of the study were presented in Yeow and Sen [20]. ...
... The present research was a part of a series of ergonomics studies in PCA factories in Malaysia, an industrially developing country (IDC), with the purpose of helping the industry (which is one of the biggest industries in the country) to improve quality, productivity and OHS [13,14,15,16,17,18,19,20,21,22]. The preliminary results of the study were presented in Yeow and Sen [20]. The final results are presented in this paper. ...
... Only a small number of operators (20) were involved in the ergonomics study because there were not many operators doing the VI task in the VI process. Taking samples from other factories was considered. ...
The study aimed at reducing the occupational health and safety problems faced by the manual component insertion operators. Subjective and objective assessments, and direct observations were made in the printed circuit assembly factory. Simple and low-cost ergonomic interventions were implemented, that is, repairing chairs, reducing high workloads, assigning operators to a maximum of 2 workstations, confining machines that emitted bad smell and much noise, and providing finger work aids. The results of the interventions were reductions in operators' work discomforts, that is, chair discomfort (by 90%), high work stress, and discomfort due to profound change in their workstations. Their health hazards were also eliminated, that is, inhalation of toxic fumes, exposure to too much noise, and pain due to pressing sharp components.
... The present research was a part of a series of ergonomics studies in PCA factories in Malaysia, an industrially developing country (IDC), with the purpose of helping the industry (which is one of the biggest industries in the country) to improve quality, productivity and OHS [13,14,15,16,17,18,19,20,21,22]. The preliminary results of the study were presented in Yeow and Sen [20]. ...
... The present research was a part of a series of ergonomics studies in PCA factories in Malaysia, an industrially developing country (IDC), with the purpose of helping the industry (which is one of the biggest industries in the country) to improve quality, productivity and OHS [13,14,15,16,17,18,19,20,21,22]. The preliminary results of the study were presented in Yeow and Sen [20]. The final results are presented in this paper. ...
... Only a small number of operators (20) were involved in the ergonomics study because there were not many operators doing the VI task in the VI process. Taking samples from other factories was considered. ...
An ergonomics improvement study was conducted on the visual inspection process of a printed circuit assembly (PCA) factory. The process was studied through subjective assessment and direct observation. Three problems were identified: operators' eye problems, insufficient time for inspection and ineffective visual inspection. These problems caused a huge yearly rejection cost of US 298,240 dollars, poor quality, customer dissatisfaction and poor occupational health and safety. Ergonomics interventions were made to rectify the problems: reduced usage of a magnifying glass, the use of less glaring inspection templates, inspection of only electrically non-tested components and introduction of a visual inspection sequence. The interventions produced savings in rejection cost, reduced operators' eye strain, headaches and watery eyes, lowered the defect percentage at customers' sites and increased the factory's productivity and customer satisfaction.
... Ergonomic adjustment is one well-known method to improve maintainability under complex operating conditions. Yeow and Sen [14] reported a project where ergonomic adjustment of the inspection workstation resulted in a 6% improvement in productivity, while the number of returned products went from 12% to 4.5%. ...
The paper emphasizes an ergonomics intervention in a medium-sized manufacturing plant to fit jobs for workers with respect to the handling of steel panels for installation onto central station air handlers. Ergonomic risk factors were identified via qualitative and quantitative data obtained from general survey, participative assessments followed by direct observations. Ergonomics intervention by means of real life experiment was conducted. Post survey incorporating both direct observations and participative assessments was subsequently implemented to gauge its effectiveness. The intervention study comprises the introduction of a trolley designed for placing steel panels horizontally and a mobile rack created for upright placing of those panels. The action-oriented ergonomics study finally produced results which were in conformity with the research aim as anticipated.
A survey was conducted on the efficacy of the Printed Circuit Assembly operations using newly designed Ergonomic Weighted Scores (EWSs) to evaluate Critical Instructions (CIs) to operators. This helped to choose priorities of problematic operations. Five EWSs were drafted, tried, and finalized by a team of experts, for the purpose of checking the adherence to CIs, failing any of which could cause adverse effects on the quality of products. The top three priority operations were identified and the follow-up studies resulted in an increase in monthly revenue of US$227,880 and improvements in quality, productivity, occupational health and safety of the operators. © 2003 Wiley Periodicals, Inc. Hum Factors Man 13: 41–58, 2003.
Key words: Business process management, process improvement, ergonomic design, motion study, ergonomic risk mapping, work life quality.
An ergonomic study was conducted to improve the workstations for electrical tests in a printed circuit assembly (PCA) factory in an industrially developing country (IDC). Subjective assessment and direct observation methods were used on the operators to discover the problems in their workstations. The problems found were: (i) poor workstation design, (ii) mix-up of tested and untested boards, (iii) missing or incorrect test steps, and (iv) unclear pass/fail colour inspection criteria. Ergonomic interventions implemented were: (i) an improved workstation with space for resting arms and the oscilloscope and computer keyboards within easy reach of the operators; (ii) clear segregation of tested and untested boards to prevent mix-up; (iii) retraining of operators by more qualified trainers; and (iv) reference colour samples for more effective recognition of different colours in the projection screen. The results were average savings in yearly rejection cost (of US1100. The interventions implemented were simple and inexpensive but resulted in many benefits.Relevance to industryThe study will be beneficial, if repeated in other PCA or electronic factories in IDCs, in terms of improvements in quality, productivity and OHS of the workers, as most of them have similar manufacturing processes and equipment and poor awareness in ergonomics.
A case study to illustrate the cost effectiveness of ergonomic redesign of electronic motherboard was presented. The factory was running at a loss due to the high costs of rejects and poor quality and productivity. Subjective assessments and direct observations were made on the factory. Investigation revealed that due to motherboard design errors, the machine had difficulty in placing integrated circuits onto the pads, the operators had much difficulty in manual soldering certain components and much unproductive manual cleaning (MC) was required. Consequently, there were high rejects and occupational health and safety (OHS) problems, such as, boredom and work discomfort. Also, much labour and machine costs were spent on repairs. The motherboard was redesigned to correct the design errors, to allow more components to be machine soldered and to reduce MC. This eliminated rejects, reduced repairs, saved US dollars 581495/year and improved operators' OHS. The customer also saved US dollars 142105/year on loss of business.
The aim of this study was to evaluate the effects on the levels on neck and shoulder muscular activity of ergonomic aids used to support or suspend the arm in different sitting postures, both with and without movement of the arm-hand. Ten skilled women workers performed a standardized simulated work cycle similar to assembling printed circuit boards, in different sitting postures with and without ergonomic aids. The elbow was supported by a loosely-mounted, padded plate. For suspension, a new device, the K-block, was used giving an adjustable, constant suspending force. Full-wave rectified, low-pass filtered, time-averaged and normalized EMG was used. Surface electrodes were applied over six neck and shoulder muscles. The results show that a reduction in the level of activity in neck and shoulder muscles can be obtained with either aid. The reduction, whether caused by suspension or support of the arm, was related to the sitting posture. Elbow support might be more efficient than arm suspension in a sitting posture with the whole spine flexed, while arm suspension might be more efficient when the trunk is inclined slightly backward. Elbow support and, particularly, arm suspension may thus be recommended as technical aids in sedentary assembly work for patients with easily elicited cervical spine and/or shoulder pain. It is also suggested that arm suspension may be used to improve ergonomic conditions at workplaces.
In an earlier paper, the authors presented models of human functioning in visual inspection and derived optimal working speeds to balance the cost of time and the cost of errors. Both self-paced and externally paced models assumed a random search strategy. It was noted that choosing a standard speed for visual inspection is difficult with standard work measurement techniques and that the data required for the suggested search model are easily measurable. The purpose of this paper is to complement the earlier work by deriving similar models employing a systematic search strategy. The two models can be considered as bounds on actual performance; thus the current paper complements the previous one by establishing an upper bound rather than a lower bound on performance in search tasks. Comparisons between the two strategies are presented.
In the design of industrial inspection tasks, the assumption is usually made that human performance data collected in a 100% inspection scheme is valid for use when the inspector is engaged in sampling inspection. A direct test of this assumption using 60 student subjects showed it to be valid. Analysis of the inspection data in terms of stopping policy in selfpaced inspection showed close correspondence with a model of systematic visual search.
Training is a neglected area for improvement of industrial inspection performance. Previous work shows that training can be effective but provides the reader with general principles rather than detailed examples of training programs. The experiment reported here gives details of two training programs devised for a complex visual inspection task. They differed only in that one (active) required the trainee to make an active response at each stage, while the other (passive) did not. Task performance for 42 subjects in three age groups showed significantly better performance (fewer errors) with the active training program. The specific error types reduced by active training were those logically related to the training program. There was a significant age decrement in performance, but it was smaller in magnitude than the difference between training programs.
Aims to verify the effect on visual inspection performance as the number
of fault types increases and to investigate the main personality traits
of a competent inspector using factor analysis. Forty subjects
participated in the experiment. The performance measures were response
time and error rate. A significant effect was found when the number of
fault types increased. Four factors obtained by factor analysis
demonstrate that the personality of a competent inspector includes the
following characteristics: stability, enthusiasm, sensitivity, and
suspicion.
An abstract is not available.
Records of the performance of a group of on-line inspectors of glass items over a ten month period were analysed using the Theory of Signal Detection. It was found that the inspection group as a whole followed the theoretical predictions. The introduction of more rapid feedback of performance to the inspectors after twelve weeks of the study increased the effective detectability of the faults significantly, reducing the percentage of missed faults by half. The effect of input quality level on performance before and after the change was studied. The usual drop in fault detection performance with increased quality was found and analysed to show that the inspection group were attempting to keep the outgoing percentage defective constant.
This article presents an approach to workload modeling of manufacturing workers using fuzzy set theory. Inspectors of integrated circuit boards in an electronic manufacturing system were observed for 9 months. Two types of inspectors were observed: novice inspectors with an average of 1.8 years and experts with an average of 26.5 years of experience. Data were collected on judgment, perception, and attention tasks. The inspectors were given subjective self-evaluation tests to capture the level of workload experienced in each of the task categories. The data were transformed into fuzzy membership functions and were used to quantify workload metrics and inspectors' performance. © 1999 John Wiley & Sons, Inc.
This paper describes the results of an ergonomics field study in a manufacturing environment. The study was performed primarily to improve the manufacturing yield in the production of electronic circuit board panels. A secondary objective was to improve operator comfort and job satisfaction. The project combined ergonomics and productivity assessments of several different tasks using analysis methodology such as ergonomic check lists, predetermined time and motion study operator assessment of ergonomic interventions and the rate of absenteeism. The project revealed a 16,000. This implies a hundred-fold rate of return of invested funds.
This paper describes the increasing emphasis on ergonomics in the manufacturing plants of IBM. Since 1978, 250,000 engineering hours have been devoted to ergonomics training. As a result a systematic approach to ergonomics improvement of manufacturing facilities has been implemented. This involves an analysis of the production environment including equipment, processes, ambient factors and job procedures. Information is collected through interviews of management, operators, and first-line supervisions, and complemented thorough field measurements of ergonomic parameters. Individual workstations as well as processes are analyzed with the purpose of modifying processes, reallocating tasks between automated devices and human operators and optimizing workstation design. Four case studies of industrial improvements are presented and analyzed in terms of improved productivity, quality, and reduction of injuries. All four studies proved to be good investments. Since its implementation around 1978, it is estimated that ergonomics improvements have resulted in cost savings of approximately $130 million.
Whereas knowledge of results (KR), that knowledge received on the outcome of one's responses, has been shown to facilitate learning of visual search in inspection, further research is required to determine its influence upon decision-making, the other aspect of inspection. Twenty subjects, randomly assigned to either a KR or No-KR group, performed a visual inspection task; defect probability and discriminability were manipulated within subjects, and sequence of discriminability levels was manipulated between subjects. Via a signal detection model interpretation, KR increased sensitivity but had mixed effects on response criterion. The sensitivity changes were interpreted via attention theory, and a cognitive model of KR utilization was presented.
We have determined the transverse chromatic aberration of the human eye by measuring the apparent offset of a two-color vernier viewed foveally through a displaced, pinhole aperture. For the same subjects, we also determined the longitudinal chromatic aberration for foveal viewing by the method of best focus. In both cases, the results were closely predicted by a simple, reduced-eye optical-model for which transverse and longitudinal chromatic aberration are directly proportional, with the constant of proportionally being the amount of displacement of the pinhole from the visual axis. Further measurements revealed that the natural pupil was closely centered on the visual axis for two subjects and slightly displaced in the temporal direction for three other subjects. One implication of these results is that, although the eye has substantial chromatic aberration, the pupil is positioned so as to minimize the transverse component of the aberration for central vision, thereby optimizing foveal image quality for polychromatic objects.
Dittmar, Warm, and Dember (1985) suggested that visual parallax may lead to declines in perceptual sensitivity over time in spatial vigilance tasks involving comparative judgments. The present study tested this possibility by restraining subjects' head movements during a 1-hr vigil in which comparative (simultaneous task) or absolute (successive task) judgments of line length were necessary for signal detection. Under free-viewing conditions, perceptual sensitivity declined over time with both types of tasks. Head restraint eliminated the sensitivity decrement in both cases. The results highlight signal quality as a crucial determinant of perceptual decrements in sustained attention.
EVALUATED, SINGLY AND IN COMBINATION, THE EFFECTIVENESS OF A 4-HR TRAINING PROGRAM AND A SET OF VISUAL AIDS DESIGNED TO IMPROVE THE PERFORMANCE OF 27 EXPERIENCED MACHINED-PARTS INSPECTORS. THE CRITERION WAS THE PERCENTAGE OF DEFECTS DETECTED IN A SAMPLE OF MACHINED PARTS. USE OF TRAINING ALONE RESULTED IN A 32% INCREASE IN DEFECTS DETECTED, WHILE USE OF VISUAL AIDS ALONE RESULTED IN A 42% INCREASE. USE OF BOTH RESULTED IN A 71% INCREASE, WHILE PERFORMANCE OF THE CONTROL GROUP DID NOT CHANGE. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Feedback of information has consistently shown positive results in human inspection, provided it is given in a timely and appropriate manner. Feedback serves as the basis of most training schemes; traditionally this has been performance feedback. Other forms of feedback which provide strategy information rather than performance information may have a role in improving inspection. This study compared performance feedback and cognitive feedback in a realistic simulation of an aircraft structural inspection task. Performance (time, errors) feedback showed the greatest improvements in performance measures. Cognitive feedback enhanced efficiency measures of search strategy. When cognitive feedback consisted of visual representations of the path and the coverage of the search sequence, subjects also were able to use this task information to improve their search performance.
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