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IJRET: International Journal of Research in Engineering and TechnologyeISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org
233
A STUDY ON PUSH-PULL ANALYSIS ASSOCIATED WITH AWKWARD
POSTURE AMONG WORKERS IN AEROSPACE INDUSTRY
Norhidayah Hashim
1
, Seri Rahayu Kamat
2
, Isa Halim
3
, Mohd Shahrizan Othman
4
1
Master Student,
2, 3
Senior Lecturer,
4
Lecturer, Faculty of Manufacturing Engineering, University Technical Malaysia
Malacca, Hang Tuah Jaya, Durian Tunggal 76100, Malacca, Malaysia
Abstract
In aerospace industries, many working tasks required their workers to perform works in push-pull activity. It is associated with an
awkward posture. The awkward posture is a practical working posture when joints are not in neutral position. Furthermore, the
workers need to push or pull the mould in a long distance into a workplace. If the workers perform the activity continuously
throughout the working hours, they may be experienced back pain problem. The objective of this study is to measure the maximum
acceptable initial force and sustained force for push-pull activity while workers perform their tasks. Besides that, this study also wants
to identify which activity can endure longer between push or pull activity. Moreover, this study measures the comfort level of working
posture. The acceptable initial force and sustained force were measured using Push-Pull Analysis, expressed in Newton, N. The
comfort level is measured using Rapid Upper Limb Assessment (RULA) Analysis, expressed in scoring level. Both of these assessments
are analysis tools Computer-Aided Three-Dimensional Interactive Application (CATIA) software. Six production workers from
manufacturing department were participated as subjects. The results show the maximum acceptable initial force for push task is
433.942N and pull task is 396.691N. While, the sustained force for push task is 333.465N and pull task is 318.317N. Referring to the
results, pushing activity can endure longer than pulling activity while workers perform their tasks. While the comfort level for this
working posture is seven. Based on this study, the authors concluded that push-pull activity can lead to the back pain problem for
workers in aerospace industry. It’s was influenced by the work activity, work load, work duration of awkward posture and distance
between workplace.
Keywords:Push-pull activity, awkward posture, Acceptable initial force, Acceptable sustained force, Comfort level
----------------------------------------------------------------------***------------------------------------------------------------------------
1. INTRODUCTION
Manual material handling (MMH) such as lifting heavy
products, reaching materials, bending forward their back when
doing tasks, and pushing or pulling excessive loads because
those tasks require a stable position and large degree of
freedom.Pushing and pulling activities are one of the activities
for MMH that can increase the risks of back pain problem [1].
The pushing and pulling activities is a frequent activity for a
great segment of the workforce, including hospital workers,
manufacturing workers, construction workers, forest workers,
etc [2-8]. Moreover, both of these activities are associated
with the awkward posture. Awkward posture can be theorized
as a discomfort posture because it is harmful position for
human body when a joint is not in its neutral range of postures
and make muscles are either shorter or longer than resting
length. When joints are exposed to postures that involve range
of movement near the extreme positions, the muscles around
the joint are stretched or compressed. If the exposure to
extreme postures is prolonged, the muscles do not
immediately return to their resting length [9]. In
manufacturing workplaces, numerous processes jobs are
recommended to be performed in awkward posture. For
example, they need to bend their neck forward greater than 30
degrees, raise their elbow above their shoulder, bend their
wrist downward with palm facing downward greater than 30
degrees, bend their back forward greater than 45 degrees,
squatting, etc [10].
The Ergonomics Design and Analysis tool of Computer-Aided
Three-Dimensional Interactive Application (CATIA) software
is one of the ergonomics analysis tool that have been applied
to analyze pushing and pulling activities of workers while
performing tasks in awkward posture [5, 11-14]. The tool
quantifies the push-pull activity in two different forces which
is maximum acceptable initial and sustainability force in terms
of Newton, N corresponding to contraction of the awkward
posture while handling the jobs. For instance, if the maximum
acceptable sustainability force is high, it means that the
workers can endure longer while performing the particular
tasks. But, if the tasks are continuously performed over the
limit, they will experience back pain problem. Besides that,
this ergonomics analysis tool also can quantify comfort level
of working posture while workers perform their tasks using
Rapid Upper Limb Assessment (RULA) feature. Several
epidemiology studies used this feature because they wanted to
IJRET: International Journal of Research in Engineering and TechnologyeISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org
234
know whether the working posture in comfort or discomfort
condition [2, 15-20].
The purpose of this study is to measure the maximum
acceptable initial force and maximum acceptable sustainability
force for push or pull activity among six manufacturing
workers in aerospace industry while workers performed their
tasks in awkward posture. Additionally, the maximum
acceptable sustainability force between push and pull activity
was compared to find out which can endure longer while
workers perform their tasks. Furthermore, the level of comfort
also measured to figure out whether the working posture in
comfort or discomfort condition.
2. METHODOLOGY
An aerospace company situated in Malaysia was selected to
perform the data collection. In the production department of
the company, all workers are males andnational citizenship.
They worked in two shifts based on a 12-hour shift schedule.
A main working activity in this company is MMH activities.
One of the MMH activities is pushing and pulling activity. All
manufacturing workers related with pushing and pulling
activity performed their tasks in awkward posture especially in
lay-up process line. Moreover, the tasks require workers to
push or pull with awkward posture because the nature of jobs
is repetitive, frequent movement, and large degree of freedom.
Six production workers were recruited as subjects in this
study. They are selected from lay-up process lines. To fulfill
the basic requirement of this study, selected workers who
performed pushing or pulling activity in awkward posture and
no injuries for the past 12 months were allowed to participate
in the experimental work. Demographic of the selected
workers from lay-up process line are described in Table -1.
Table -1: Demographic of workers participated in the study
Criteria Mean (SD)
Gender Male
Age 25.7 (5.0)
Mass (kg) 64.5 (10.9)
Height (cm) 174.2 (7.3)
Experience (year) 4.7 (2.7)
An Ergonomic Design and Analysis tool of Computer-Aided
Three-Dimensional Interactive Application Version 5 Release
19 (CATIA V5R19) software were used to analyze the
pushing and pulling activity associated with awkward posture
of the workers. Besides that, the comfort level of working
posture also measured using this tool. The capture posture of
workers was captured based on real job monitoring. The
measurement of distance between workplace was measured by
using measuring tape. The distance is about 2.1 meters (m)
from furnace (Autoclave) to workplace (Clean Room). This
distance is the furthest distance for pushing and pulling
activity in this working area. On the other hand, the real time
monitoring also needs to be considered for this working
activity. It is because one of the requirements from the
ergonomics analysis tool is time consumption for pushing and
pulling activity per mould. Other than that, the weight of panel
also required which is 500 kilogram, kg per panel. After all the
data needed are ready, the design can now start to analyze.
Fig-1 shows the worker with awkward posture for pushing and
pulling activity.
Fig -1: Awkward posture for pushing and pulling activity
By using ergonomics analysis tool from CATIA V5R19, the
pushing and pulling activity can be analyzed. The analysis is
used to analyze the maximum acceptable and sustainability
force when workers push or pull each mould. The feature used
from this tool to do the analysis is Push-Pull Analysis feature.
Besides that, the comfort level of the working posture also
analyzed by using this tool. But, the comfort level is analyzed
by using RULA feature. The working posture for this analysis
is same with the posture shown in Fig -1. However, the
analysis needs to be done in three different height of mould
which is 50 centimeter (cm), 47cm, and 45cm. For this
analysis, the workers is separated into three group which is
taller (the height above 180.0cm), medium (the height
between 170.0cm to 179.9cm), and shorter (the height below
170.0cm). Besides that, in this analysis, all the angles involved
in awkward posture are an average from each worker as
shown in Table -2. The angles in analysis are same with the
angles in real case study as in Figure 1.
Table -2: Analysis angle involved in awkward posture (pls
modify like a table)
Body Segment Angle
Shoulder:
both left and right 95o
IJRET: International Journal of Research in Engineering and TechnologyeISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org
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Hand arm:
both left and right 53o from
origin, 00
Neck:
12o from origin, 00
Upper back:
5o from origin, 0o
Lower back:
36o from origin, 00
Right thighs:
40o from origin, 00
Right calf:
40o from origin, 00
Right ankle:
5o from origin, 00
Left thighs:
32o from origin, 00
Left calf:
20o from origin, 00
Left ankle:
5o from origin, 00
Based on selected angle in Table -2, the whole body working
posture for push-pull activity has been designed in CATIA
V5R19 software by using ergonomics analysis tool. Fig-2
shows the design of whole body awkward posture for pushing
and pulling activity by using ergonomics analysis tool in
CATIA V5R19 software.
Fig -2: Awkward posture for pushing and pulling activity
After the whole body awkward posture with the mould has
designed, the Push-Pull Analysis now can be analyzed. The
output parameter from the analysis is the value of maximum
acceptable initial and sustained force that is expressed in
Newton (N). While the output parameter from RULA feature
is final score for comfort level of awkward posture. Graphical
analyses associated with descriptive and comparative analysis
were used to interpret the data.
3. RESULTS AND DISCUSSION
This study has conducted an analysis of pushing and pulling
activity associated with awkward posture of manufacturing
workers in aerospace company. Besides that, this study also
quantifies the comfort level of working posture among the
workers while they are doing their tasks. In the company, a
IJRET: International Journal of Research in Engineering and TechnologyeISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org
236
main manufacturing process is coming from lay-up process
line. This lines required workers to perform pushing and
pulling activity in awkward posture for period of time. All
workers worked on a 12-h shift schedule. The shift is changed
every week which is worked both; day and night shift. It was
observed that the workers spent about 80% of the working
hours in awkward posture to do their tasks (only neutral
standing during setup ply and sitting during breaks)
throughout the 12-h working period. This is due to the
activities that required the workers to push or pull the panel
every 45 minutes with awkward posture from furnace
(Autoclave) to workplace (Clean Room). For instance,
workers also need to push or pull the panel in the workplace
(Clean Room) before the panel is fixing to the floor. Thus, the
process would be practicable in awkward posture as it requires
frequent bending forward of the workers back. This study
observed that the back pain problem occurred particularly in
the lower back due to above mentioned working conditions.
Furthermore, there were complaints of intense pain in those
body parts from the workers of lay-up process lines which is
upper back, shoulder, hand arm, wrist, and fingers.
Through Push-Pull Analysis as shown in Fig-3, this study
identified that the maximum acceptable initial force when the
workers do the pushing activity is 433.942N. While the
maximum acceptable initial force for pulling activity is
396.691N. According to the results, the workers must either
use the initial force of 433.942N to push the mould or use
396.691N to pull the mould. The initial force is the primary
effort needed for workers to do their works [1].
Fig -3: Push-Pull Analysis from CATIA V5R19 software
Based on Fig-3, the time consumption used is 2700 seconds is
equally 45 minutes. Besides that, the distance of push or pull
the mould is 2100 millimeters (mm) is equally 2.1m. Other
than that, the population sample is 50% because the subjects
for this experiment are six workers among 12 workers. Hence,
the population sample is half of the overall workers.
Referring to the result of maximum acceptable sustained force
for pushing activity is 333.465N. While the result for pulling
activity is 318.317N. According to the results, the workers
used 333.465N to push the mould or use 318.317N to pull the
mould along the activity is performed. The sustained force is
the gross effort needed when the workers do their works along
working hours [1].
This analysis pointed that working activity, distance of push-
pull activity, and weight of mould can influence the initial
force needed to push or pull the mould. Other than that, it’s
also influence the sustained force which is the gross force
needed during the activity is performed. When the worker
used the sustained force in a long period of time, their energy
will decrease. Due to energy diminish, the muscles will
involve with contraction and this condition can lead to
discomfort and back pain problem [21].
Moreover, according to ergonomics analysis tool using RULA
feature from CATIA V5R19 software, the working posture is
discomfort posture because the level of comfort for this
awkward posture is 7 score. Fig-4 shows right body region
from RULA analysis for push-pull activity using average
shortest worker with 45cm height of mould. Whereas Fig-5
shows left body region from RULA analysis for push-pull
activity using average shortest worker with 45cm height of
mould. Both left and right need to analyze because the
awkward posture is not in symmetrical posture. Thus, the
analysis needs to be done in both body regions because the
comfort level will different. By referring to Fig-6, the score
from comfort level of RULA analysis will easily understand
using RULA standard from NIOSH [20].
Fig -4: RULA analysis of right body region for push-pull
activity using average of shortest worker with 45cm height of
mould
IJRET: International Journal of Research in Engineering and TechnologyeISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org
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Fig -5: RULA analysis of left body region for push-pull
activity using average of shortest worker with 45cm height of
mould
Fig -6: Standard score from NIOSH for comfort level of
RULA analysis
Based on Fig-4 and Fig-5, both of body regions which is right
and left are in very high risk working posture. Changing is
immediately needed for that working posture. The changing
only needed for right and left hand arm. Based on the results,
wrist and arm is in discomfort posture because the wrist is in
twist position for both hand arms. Thus, placed more stress in
the wrist for both hand arm [22]. Table -3 shows summary of
RULA analysis for three different groups of workers with
three different height of mould.
Table -3: Summary of RULA analysis for three different
groups of workers with three different height of mould
Group of
Workers Height of
Mould (cm) Average Score (Right
and Left)
Small 50 7
Medium 45 7
Tall 47 6
Small 45 5
Medium 47 5
Tall 50 5
Small 47 6
Medium 50 6
Tall 45 7
* Tall workers (the height above 180.0cm), medium workers
(the height between 170.0cm to 179.9cm), and small workers
(the height below 170.0cm)
After averaging both of the results (right and left body region),
the average score for each group of workers shows the smaller
size of workers not suitable to work using mould with 50cm of
height. While the medium and taller size of workers not
suitable to work using mould with 45cm of height. Fig -7
shows statistical data analysis of average score from RULA
analysis for each group of workers. From the results, small
workers experienced discomfort working posture when they
are working with 50cm height of mould. Other than that,
medium and tall workers experienced discomfort working
posture when they are working with 45cm height of mould.
Fig -7: Statistical data analysis of average score from RULA
analysis for each group of workers
This analysis pointed that the height of workers and height of
mould can influence the level of comfort for working posture.
When the worker is bending forward their back in a long
period of time, static contraction of muscles can occur
particularly in the back. Due to static contraction, performance
of the muscles may decrease and this condition can lead to
discomfort and back pain problem [21].
CONCLUSIONS
This study has performed Push-Pull Analysis and RULA
Analysis for working posture of manufacturing workers at lay-
up process line in aerospace company. All workers performed
their tasks in awkward posture for prolonged time periods.
The measurements of push-pull activity were conducted using
500 kilogram weight of mould and 2.1 meters of distance from
furnace (Autoclave) to workstation (Clean Room). Besides
that, the measurements of RULA activity were conducted
using three different height of mould and three different height
of worker. Regarding to the maximum acceptable initial force
from Push-Pull Analysis, if the workers push the mould the
force needed is 433.942N. If the workers pull the mould the
Small
Medium
Tall
45cm
5
7
7
47cm
6
5
6
50cm
7
6
5
0
2
4
6
8
Average Score
IJRET: International Journal of Research in Engineering and TechnologyeISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 01 | Jan-2014, Available @ http://www.ijret.org
238
force needed is 396.691N. On the other hand, if the workers
push the mould the maximum acceptable sustained force
needed is 333.465N. If the workers pull the mould the force
needed is 318.317N. Both results show that if the workers
used pushing activity they can endure longer to finish their
tasks. Moreover, the highest result of discomfort score from
RULA Analysis is level seven which is very high risk working
posture and the changing should be implemented now.
Therefore, this study concluded that back pain problem of the
lay-up workers in aerospace industry was influenced by the
work load, work activity and duration of awkward posture.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the Ministry of Higher
Education of Malaysia, the UniversitiTeknikal Malaysia
Melaka (UTeM), and the Centre of Research, Innovation &
Management (CRIM) UTeM for funding this research under
Research Grant PJP/2012/FKP (6D) S1125. Special thank also
goes to Composites Technology Research Malaysia (CTRM)
Sdn. Bhd. for the permission and opportunity to facilitate a
fruitful research.
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BIOGRAPHIES
Norhidayah Hashimis currently a fulltime
research student for Master of Science in
Manufacturing Engineering. Her research area is
musculoskeletal disorders (MSDs) problem
focusing on back pain problem. She already
published 2 journal articles and conference proceedings in
Malaysia. She has joined CATIA Training on 2013 in UTeM.
She is a member of the Institution of Engineers, Malaysia.
Seri Rahayu Kamat. She completed her Doctor
of Philosophy in Mechanical Engineering in
2010 from Sheffield Hallam University,
Sheffield, United Kingdom. She specializes in
Biomechanics, Ergonomic, and Work Study. She
has authored 20 journal articles and conference proceedings in
Malaysia and other countries. She has received Award in
Malaysian Technology Expo 2012 in PWTC Kuala Lumpur,
Malaysia and Award in UTeM Expo 2012 (UTeMEX 2012) in
UTeM, Malacca. She is a member of the Institution of
Engineers, Malaysia and Board of Engineers, Malaysia.
Isa Halim. He received Doctor of Philosophy in
Mechanical Engineering from
UniversitiTeknologi MARA, Malaysia in 2011.
His research discipline is Industrial Ergonomics.
He has authored more than 50 publications
including journal articles and conference proceedings. He has
been conferred Excellent Research Award from the
UniversitiTeknologi MARA in 2012, Best Paper Award from
International Conference on Design and Concurrent
Engineering (2012), and from Social Security Organization of
Malaysia (2011). He is member of Board of Engineers,
Malaysia, The Institution of Engineers, Malaysia, and
Malaysian Society for Engineering and Technology.
Mohd Shahrizan Othman He has received his
Master of Science in Statistics granted by USM
on 2004. His expertise in Engineering
Mathematics, Numerical Method, Differential
Equation, and Statistics and Probabilities. He is a
member of the Institution of Engineers, Malaysia and Board of
Engineers, Malaysia.
