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Ergonomic design of workstation for a labeling task Asim Amjad

Institute of Quality and Technology Management, University of the Punjab, New Campus, Lahore, 54590, Pakistan. [email protected]

Zahid A. Shah Institute of Quality and Technology Management, University of the Punjab, New Campus,

Lahore, 54590, Pakistan. [email protected]

Abstract –The aim of this study was to design a workstation for a labeling task using principles of ergonomics. The case company was involved in packaging imported electronic devices and selling them in the market. Before packaging, the labels had to be attached on the devices. When authors were consulted for workplace assessment, the workers used to sit on floor to attach labels. Based on anthropometry of the workers in this department, an adjustable table was designed and put to use for evaluation. An assessment of posture and fatigue resulting from the task was made – both for sitting-on-floor and new workstation and under different lighting conditions. Production and discomfort for both settings were compared. Borg scale was used to calculate the level of discomfort. There was a significant reduction in fatigue using ergonomically designed workstation as compared to sitting-on-floor setting. There was a 70% increase in production as well.

Keywords: ergonomic design; labeling; anthropometry; discomfort; posture

I. INTRODUCTION In the current study the labeling task for imported electronics products was assessed using principles of

ergonomics. The workers were performing labeling activities in an open hall. They faced difficulties to perform their task efficiently because they had to sit on floor for a prolonged period of time. So, they tired soon and production was also affected. A workstation was designed using ergonomic principles [1, 2, 3, 4, 5] to overcome these problems.

Ergonomic workstation design based on engineering anthropometry and occupational biomechanics can play a major role in the reduction of many risk factors of occupational injury [6]. Anthropometry and biomechanics are closely related, because occupational biomechanics provides the bases for the use of engineering anthropometry to the problems of workstation design [3]. Engineering anthropometry is the effort in applying such data to workstations, equipment, tools and clothing design to enhancing the workforce safety, efficiency, and comfort.

Lighting is an important factor for all industrial tasks. The poor lighting conditions in the workspace can cause different problems like (1) Insufficient light; (2) Glare; (3) Improper contrast; (4) Poorly distributed light; (5) Flicker [7, 8, 9, 10].

An ergonomically designed workstation attempts to obtain an adequate balance between worker capabilities and work requirements. The objective is to optimize productivity of workers and the total system and at the same time enhance workers’ physical and mental wellbeing, job satisfaction, and safety. Often, workstation in industry is designed in an arbitrary manner with little attention to anthropometric measurements and biomechanical considerations of the anticipated user. The situation is aggravated by the lack of usable design parameters or dimensions [11]. Workstation design is closely associated to the risk of work activities [12]. The main risk factors for musculoskeletal disorders can be categorized under one of four headings: force, posture, repetition, and duration of task [13]. Other factors that contribute to musculoskeletal discomfort including: increased job demands and more hours of working [14]; increased levels of psychological stress [15, 16]; and a lack of specific ergonomic features in the workstations design [17]. One of the most at-risk parts of human body at work is the backbone. There are many conditions in the low back which may cause back pain, including muscular or ligamentous strain, facet joint arthritis, or disc pressure on the annulus fibrosis, vertebral end-plate, or nerve roots [18].

In this study risk associated with work activities was measured for the labeling operation. The goal of this study was to help a company, involved in labeling of electronics products, design ergonomic workstation by analyzing current job design.

2808© IEOM Society International

Proceedings - International Conference on Industrial Engineering and Operations Management, Kuala Lumpur, Malaysia, March 8-10, 2016

mailto:zahid.iqtm@

II. METHODOLOGY

The case company had two major departments – packaging and labeling. The focus of this study was labeling department. There were ten workers performing this task sitting on floor for whole shift (with one break). They had to bend their back and neck and cross their legs to perform the task. One example posture is shown in Figure 1. Such a posture was obviously dangerous and could result in physical disorder in the long run. Moreover, the task was performed during night shift. The lighting conditions also seemed inappropriate. As the labels had to be fixed at a specific place on the devices, the task required a sufficient amount of light.

As a first step, some basic anthropometric measurements of all the workers performing the task were taken. They included stature and elbow height. These measurement along with the age of all workers are shown in Table I.

TABLE I. Age, stature, and elbow height of workers performing the labeling task.

Sr. # Aged Stature (in.) Elbow Height (in.) Sr. # Aged Stature (in.) Elbow Height (in.) 1 32 66 46.2 6 29 69 48.5 2 25 65 45.4 7 28 66 46.2 3 28 68 47.7 8 30 65 45.4 4 23 69 48.5 9 25 64 44.6 5 28 66 46.2 10 30 65 45.4

An adjustable table was designed so that workers could perform the task while standing and could also adjust its height. The workstation was designed according to basic anthropometric principles [13]. The minimum elbow height was found to be 44.6 inches and maximum elbow height was found to be 48.5 inches. However, the table was designed with an adjustability range of 40 – 55 inches – to provide a greater range of adjustability for newly hired workers with a greater elbow height. The table and its range of adjustability is shown in Figure 2. The resulting posture is shown in Figure 3.

Fig. 2. (a) Minimum; and (b) Maximum Dimension of Workstation; and (c) Isometric view of designed Workstation

Fig. 1: Posture of a worker performing the labeling task.

(b) (a) (c)



Fig. 3: Posture (After redesigning the workstation)

In order to assess the effect of this design, an evaluation of workers’ production and discomfort was made for both postures. As this was a precision task, the effect of lighting was also investigated using its two levels (low: 148 lux and high: 466 lux). The production was measured using time study while discomfort in ten different body parts was measured using Borg scale.

There were 2 dependent variables i.e. production and discomfort. Four different combinations were studied with and without using workstation (labeling while sitting on floor). The details of these four combinations are shown in Table II.

TABLE II. The list of experiments performed. For posture: sitting means existing posture, standing means posture with newly designed table.

Sr. # Posture Light Intensity Sr. # Posture Light Intensity

01 Sitting Less, 148 Lux 03 Standing Less, 148 Lux

02 Sitting High, 466 Lux 04 Standing High, 466 Lux

The workers were randomly assigned to any of the above combinations. Each experiment was repeated four times; so a total of 40 measurements were made for production.

Table III. Data of production under different combinations of light intensity and posture. For light: less = 148 lux, high = 466 lux. For posture: sitting means existing posture, standing means posture with newly designed table.

Sr. # Posture Light Production Sr. # Posture Light Production 1 Sitting Less 95 21 Standing Less 150 2 Sitting Less 90 22 Standing Less 153 3 Sitting Less 93 23 Standing Less 159 4 Sitting Less 100 24 Standing Less 160 5 Sitting Less 97 25 Standing Less 161 6 Sitting Less 98 26 Standing Less 169 7 Sitting Less 101 27 Standing Less 163 8 Sitting Less 99 28 Standing Less 169 9 Sitting Less 93 29 Standing Less 165

10 Sitting Less 95 30 Standing Less 158 11 Sitting high 144 31 Standing High 193 12 Sitting high 150 32 Standing High 191 13 Sitting high 155 33 Standing High 193 14 Sitting high 151 34 Standing High 195 15 Sitting high 149 35 Standing High 198 16 Sitting high 138 36 Standing High 190 17 Sitting high 132 37 Standing High 191 18 Sitting high 149 38 Standing High 194 19 Sitting high 148 39 Standing High 198



20 Sitting high 151 40 Standing High 190

The recommended intensity of light for labeling operation is 200-500 lux [19, 20, 21, 22, 23]. The combinations of posture (sitting, standing), light (less i.e. 148 lux, high i.e. 466 lux) and corresponding production for attaching labels are shown in Table III.

III. ANALYSIS & DISCUSSION

All statistical tests were conducted using Minitab v15.0. The number of factors in design of experiment were 2 i.e. posture (sitting & standing) and light (148 lux & 466 lux). The cube plot of yield (Production) is shown in Fig. 4.

The analysis of variance showed that there was a significant difference in production for two postures as well as for two lighting levels (p < 0.05). It shows that increasing the lighting to the recommended level and improving the posture increased the production. There was also a significant interaction effect of these two variables. The effect of lighting on production depends on the posture and vice versa i.e. the effect of improved lighting is further enhanced with improved posture. Conversely, the effect of improved posture on production is further enhanced with improved lighting. The detailed results of ANOVA are shown in Table IV.

TABLE IV. ANOVA table for production.

Analysis of Variance for Yield (Production) (coded units) Source DF Seq SS Adj SS Adj MS F P

Main Effect 2 48219.2 48219.2 24109.6 899.24 0.000 2-Way Interactions 1 810.0 810.0 810.0 30.21 0.000 Residual Error 36 965.2 965.2 26.8 Pure Error 36 965.2 965.2 26.8 Total 39 49994.4

The discomfort was measured with the help of Borg CR 10 Scale [24, 25, 26, 27]. The discomfort of the subjects was measured for both sitting and standing postures. The bar graph of discomfort for different body parts is shown in Fig. 5. It is clear that the mean discomfort for all body parts is less in standing posture as compared to seated posture (p <0.05), except for knees, ankles, and feet where the score was zero for both posture. Result further shows that upper and lower back were affected the most in sitting posture. The ANOVA table of discomfort of different body parts for both postures is shown in Table V.

Fig. 4. Cube Plot for Yield (Production)

Body PartsPosture

Upper BackThingsShoulderNeck or HeadLow BackKneesCalf ( Leg Below Knee)ButtocksArms & HandsAnkles & FeetStndSitdStndSitdStndSitdStndSitdStndSitdStndSitdStndSitdStndSitdStndSitdStndSitd

7

6

5

4

3

2

1

0

Prec

eive

d D

isco

mfo

rt



Fig. 5. Discomfort Result (sitd = siting, stnd = standing)

TABLE V. ANOVA for discomfort of different body parts for two postures

Two-way ANOVA: Discomfort versus Body Parts, Posture. Source DF SS MS F P

Body Parts 9 126.174 14.0193 53.38 0.000 Posture 1 38.069 38.0689 144.94 0.000 Interaction 80 47.146 5.2385 19.94 0.000 Error 99 21.012 0.2627 232.401 S = 0.5125 R-Sq = 90.96% R-Sq(adj) = 88.81%

IV. DISCUSSION

Labeling task in sitting posture resulted in stress on worker’s body especially upper and lower back and resulted in low production. Simple principles of ergonomics were used to improve the task. The task was designed according to ergonomics principle i.e. fit the task to the person [6], instead fit the person to the task. Anthropometric design of table with adjustability significantly improved the production. It also reduced the discomfort significantly. However, it is hard to stand for 8 hours. The task could be further improved by designing a sit-stand workstation. If not possible, a footrest could be useful to reduce stress on the backbone.

This study clearly demonstrated how applying very basic rules of ergonomics science – improving posture and setting lighting at recommended levels – can bring significant improvements in productivity and also improve the workers’ well-being. One of the appealing aspect of this study is that these improvements are very cost-effective. They do not require high investments. The most important challenge, however, is to create awareness among top management that benefits of ergonomic interventions are two-fold; increasing workers’ well-being and organization’s productivity. Both of these go hand-in-hand. Compromising on one automatically affects the other.

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