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Ergonomic design of hammer handle to reduce musculoskeletal disorders of carpenters

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  • Nipro JMI Company Ltd

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The musculoskeletal disorders (MSDs) are the most common work-related health problems in Bangladesh, affecting thousands of carpenters. Typically, musculoskeletal disorders affect the elbow, neck, shoulders and wrist pain during wooden work. The aim of this paper is to focus on certain important aspects of hammer use in occupational work situations, with an emphasis on comfort or discomfort in using hammer according to users. The study concluded that it was necessary to redesign the hammer to reduce the musculoskeletal disorders. Anthropometric data of 300 male carpenters (age: 45.23±11.65 years) in SouthWestern districts of Bangladesh were measured. The ergonomically designed multipurpose hammer reduces the musculoskeletal disorders mainly wrist pain 87% to 72%.
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International Journal of Research in Advanced Engineering and Technology
78
International Journal of Research in Advanced Engineering and Technology
ISSN: 2455-0876
Impact Factor: RJIF 5.44
www.newengineeringjournal.in
Volume 4; Issue 2; May 2018; Page No. 78-83
Ergonomic design of hammer handle to reduce musculoskeletal disorders of carpenters
MT Haque1
1 Department of Industrial and Production Engineering, Jessore University of Science and Technology, Bangladesh
Abstract
The musculoskeletal disorders (MSDs) are the most common work-related health problems in Bangladesh, affecting thousands of
carpenters. Typically, musculoskeletal disorders affect the elbow, neck, shoulders and wrist pain during wooden work. The aim of
this paper is to focus on certain important aspects of hammer use in occupational work situations, with an emphasis on comfort or
discomfort in using hammer according to users. The study concluded that it was necessary to redesign the hammer to reduce the
musculoskeletal disorders. Anthropometric data of 300 male carpenters (age: 45.23±11.65 years) in South-Western districts of
Bangladesh were measured. The ergonomically designed multipurpose hammer reduces the musculoskeletal disorders mainly wrist
pain 87% to 72%.
Keywords: hand tools, anthropomentry, musculoskeletal disorders, handle and power grip
1. Introduction
A hammer is a simple force amplifier that works by
converting mechanical work into kinetic energy and back [1].
Existing non-powered traditional hammer contains a head and
a handle, which can be fixed together by a special wedge or by
glue, or both. This construction is often used to combine a
compressed metallic striking head with a non-metallic shock
absorbing handle to reduce user fatigue from repeated strikes
[2-4]. Hammer is one kind of the best hand tool which todays
used for various function of household, machinery and
industrial works [5]. Hammer is one of the most important
hand tool used in carpentry. But an improper designed
hammer may cause significant musculoskeletal disorders
(MSDs) [6]. Musculoskeletal disorders (MSDs) are currently
most critical problems faced by the ergonomists in the
workplace [7]. Workplace injuries are extremely severe in
these types of industries. Poor working conditions and the
absence of workers have resulted in a very high incidence of
MSDs [8]. Ergonomically designed hand tools reduce the risk
of occupational disorders of the upper limbs. They also
provide comfortable work for the workers and give high
production rate [9]. Ergonomics is the scientific discipline
concerned with the understanding of interactions among
humans and other elements of a system, and the profession
that applies theory, Principles, data and methods to design in
order to optimize human well-being and overall system
performance [10]. Several researchers designed some non-
powered tools such as shovel, hammer, screw driver etc. In
that case they were focused on the comfort and discomfort
issues based on some parameter [11-17]. Grip size and diameter
is important parameter to design a hand tool. Proper gripping
improves the efficiency of the wooden work [18]. This study
was focused on hammer handle related injuries in traditional
carpentry or wooden work and controlling the rate of injury
through ergonomic study and designing new multi-purpose
hammer. In this study authors are trying to prevent the
ergonomic discomforts and injuries mainly wrist pain which
occurs most of the time using traditional hammer.
2. Methodology
A. Material and Methods
The study was conducted during 20th August 2017 to 20th
October 2017 in different areas of Bangladesh. In this study,
there were 300 carpenter’s respondents. All of them were
willing to participate in this study. A survey was conducted on
the types of hammers were used in Carpentry work. Following
figures-1 & 2 shows the design of hammers available in south-
western areas of Bangladesh [18-20].
Fig 1: (a) Carpenters hammer, (b) Bumping hammer, (c) Ball- peen
hammer
Carpenters hammer is a hammer with a cleft at one end for
pulling nails. Its broadly uses in carpenter industry. Bumping
hammer is a power-driven hammer with two broad flat faces
on a narrow head. It is used in bumping sheet metal. It is a
hammer have a rounded, hence “ball”, peen which used for
shaping metal closing rivets and rounding edges off metal pins
and fasteners. It is also used for hitting chisels and punches
during carpenter work.
International Journal of Research in Advanced Engineering and Technology
79
Fig 2: (d) Claw hammer, (e) Locksmiths hammer, (f) Masons
hammer
Claw hammer is a hammer with a heavy rigid head and a
handle. It is basically used to deliver an impulsive force by
striking. Locksmiths hammer is a German pattern hammer
with colored end of handle and basically handle made of
wood. Basically used to create high pressure & force.
Mansions hammer is a hammer with a moderately heavy head
sharpened at one end to a chisel edge. This types of hammer
specially used for removing pin from wood.
B. Measurement of existing hammers
The hammers are widely used in the carpentry and wooden
work in Bangladesh. Many existing hammers are not
ergonomically designed because they require a lot of wrist
bending and twisting during use. In this survey work
researchers took the measurement (Handle diameter, Grip
Size) of the different existing hammers shows in figure-3.
Fig 3: Measurements of hammers
C. Anthropometric measurements of hand
Hand length (HL): The length of the hand as measured
between the wrist crease and the tip of the longest finger on
the hand, usually thumb finger.
Hand breadth (HB): The length of the palm of the hand,
measured perpendicular to hand length.
Finger length (FL): The length of the thumb finger as
measured between the palmar digital and the tip of the middle
finger.
Hand breadth at metacarpal (HBM): The maximum breadth
across the hand where the fingers join the palm. The right
hand is extended straight and stiff with the fingers held
together.
Fig 4: Hand anthropometry
D. Determination of an optimal cylindrical handle
diameter for power grip
In this study researchers use following equations to determine
the general grip, power grip diameter and grip size [21-29]:
…….... [1]
= ..... [2]
…….……….. [3]
E. Skewness test
According to Fan and Gencay (1995) [30], Hamilton (1989) [30-
31] following equations is used to calculate the skewness:
……………….... [4]
If the skewness is between the -0.5 and 0.5, the data are
approximately symmetric.
If the skewness is between -1 and -0.5 or between 0.5 and
1, the data are moderately skewed.
If the skewness is less than -1 or greater than 1, the data
are highly skewed.
3. Results
A. Ergonomic selection of musculoskeletal disorders
The Figure-5 and Table-1 presents the prevalence of
musculoskeletal disorders in different body regions of
carpenters. As Figure-5 shows, the most commonly affected
parts are wrist, shoulder and elbow.
Table 1: Frequencies of ergonomic discomforts and injuries
Musculoskeletal
Disorders
No. of
Workers
Percentage of
Workers (%)
Headache
150
50
Shoulder pain
195
65
Wrist pain
260
87
Stiffness in finger
215
72
Soreness in elbow
183
61
International Journal of Research in Advanced Engineering and Technology
80
In this study the prevalence of musculoskeletal disorders
among carpenters were 87% for the wrist pain due to improper
ergonomically designed hammer. Other musculoskeletal
disorders among workers were 72% for the stiffness in finger
and 75% for shoulder pain [32, 33].
Fig 5: Frequencies vs. Musculoskeletal Disorders (After using existing hammer)
Survey results shows that 69% carpenters want to improve in
working conditions, other result shows that more than 55% of
carpenters do not satisfied with their working environments.
47% workers want to redesign the hammer because of they are
not comfortable with exiting hammer. Most of carpenters
suffer from various musculoskeletal disorders which are not
good for long time, so that they want to improve the design of
their hammer [34-38].
B. Overall dimensions of hammers available in different
areas of Bangladesh
The overall dimensions of existing hammers were recorded
from different areas of Bangladesh show in following table.
Table 2: Dimensions of existing hammers
Parameter
Handle length(cm)
Handle diameter(cm)
Average
32.35
2.95
SD
0.516
0.06
Max
33
3.1
Min
31
2.89
5th Percentile
31.6
2.896
50th Percentile
32.5
2.95
95th Percentile
33
3.04
C. Anthropometric measurements of the Carpenter
Table 3: Anthropometric measurements
Man
MFL
TL
IGB
HBM
HB
HL
MFL
Average
7.87
3.01
4.16
7.63
8.48
18.69
7.87
SD
0.487
0.34
0.47
0.49
0.45
1.18
0.487
Max
9.7
3.9
5.1
8.9
9.6
23.4
9.7
Min
6
2.3
3.4
6.4
7
16.4
6
5th %le
7.2
2.5
3.5
6.9
7.8
17.1
7.2
50th %le
7.9
3
4.1
7.6
8.5
18.5
7.9
95th %le
8.695
3.69
4.8
8.495
9.2
21
8.695
D. Skewness test of existing hammer
Table 4: Skewness test
Statistic
Handle length (cm)
Handle diameter (cm)
Mean
32.35
2.95
SD
0.516
0.06
Median
32.28
2.98
Skewness
0.41
-1.5
Evaluation
Approximately symmetric
Highly Skewed
E. Proposed dimensions and design of ergonomically
designed hammer
Table 5: Proposed dimensions
Features
Dimensions (cm)
Used Equations
Optimal grip diameter
3.368
[1]
Power grip diameter
3.739
[2]
Grip size
11.747
[3]
Fig 6: CAD Design (Isometric View)
International Journal of Research in Advanced Engineering and Technology
81
Fig 7: CAD Design (2D Drawing)
Fig 8: CAD design of newly designed hammer
F. Flexibility Analysis
Table 6: Ergonomically designed hammer vs. Existing hammer
Comfort factors
Ergonomically
designed hammer
Existing
Hammer
Quality of the hammer handle
Good
Good
Surface Finish of hammer handle
Good
Good
Compatibility for the type of grip
Excellent
Normal
Overall Comfort at first look
Excellent
Normal
Fits the hand
Excellent
Bad
Effect of hammer use on hand/arm
Good
Worst
G. Experimentation for ergonomically designed hammer
handle
Table 7: Experimentation for optimal diameter
Evaluation
Description
Grip size is too
small
The two middle fingers are digging into the
heel portion of the operator palm.
Grip size is
correct
The two middle fingers are slightly gapped to
touching the heel portion of the operator palm.
Grip size is too
large
The two middle fingers have too much gap to
the heel portion of the operator palm.
The authors have found that the Grip size is correct and the
compatibility of grip is excellent. It fits with hand
comfortably.
I. Validation and Testing
The Figure-9 presents the prevalence of musculoskeletal
disorders in different body regions of workers after using new
designed multi-purpose hammer.
Fig 9: Frequencies vs. Musculoskeletal Disorders (After using new designed hammer)
4. Discussion
In this study, the authors survey different areas in Bangladesh.
Here the authors have found that the carpenters were facing
high level of wrist pain after carpentry or wooden work. For
this reason, the authors were recorded some significant
anthropometric measurements for purpose of designing
ergonomically correct hammer handle to prevent the wrist
pain.
5. Conclusion
The purpose of this study has been fulfilled; a hammer handle
for power grip operation has been developed and
implemented. However the workers found that their working
postures with new multipurpose hammer is good and reported
comfort. Results shows that wrist pain was the big of
musculoskeletal disorder of carpenters which have been
reduced to 72% from 87%.
6. Future Scope
In this study, anthropometric data were collected from 300
male carpenters of South-Western districts in Bangladesh. As
the scenario of wooden working condition in most of the
districts in Bangladesh is almost the same, the provided injury
and discomfort related data can be a great resource for the
administration and for social workers to understand the
working condition in carpentry industries of Bangladesh. In
International Journal of Research in Advanced Engineering and Technology
82
this study, research could not perform dynamic simulation of
hammer operation for lack of facility. It will be makes the
proposed hammer model more validate.
7. Acknowledgments
The authors are pleased to acknowledge Monir Ahmed,
Mahian Haque, Shamir Kumar, Shahinur Rahman and Nipen
Kar for their cooperation and assistance in conducting surveys
and collecting data in this study. The authors are also thankful
to Dr. Deepak Kumar Biswas (Assistant Surgeon, United
Health Complex, Jessore), Dr. Motiur Rahman (Assistant
Surgeon, Pirojpur Sadar Hospital, Pirojpur), and Dr. Siddharth
Kar (Assistant Registrar, Medicine, Jessore Medical College,
Jessore) for their help, support, and consultation through the
study.
8. Conflicts of Interest
The authors declare that they have no conflicts of interest.
9. Ethical Statement
The authors declare that they have followed ethical
responsibilities.
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... However, a workplace safety sheet reported that a good hammer has a rubber handle with pinch grip, which is generally more comfortable to use and produces greater force with the lower strain on the forearm, wrist and hand muscles, and ligaments and joints [23]. Furthermore, it has been proposed that handle length and grip size also affect pain in the hand among carpenters [24]. In addition, the workstation was managed by developing a tilting adjustable desk and stool for individual carvers, as a previous report showed a work station designed with a high seat that sloped forward by approximately 10 degrees in order to provoke anterior pelvic tilt [9,25] in industrial carpenters [11]. ...
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Oyster as a popular and much beloved food, rich in nutrition and unique in flavor, has been cultivated widely in the wo rld. Taiwan has a history of oyster farming over 300 years. The recent farming areas spread mainly along the southwestern coast of Taiwan, generating about 90% in its to tal o utput. Oysters in Taiwan are mainly so ld in seafood m arket with only th e flesh . Therefore, oyster is shucked right away once it has been c ollected from the culturing fa rm. This paper pr esents a stud y on the lo cal o yster shucking too ls, co nsisting of two ph ases. First, a fiel d survey was c onducted t o i nvestigate t he s hucking m ethod, s hucking k nives used, an d possible injuries and disorders experienced by shucking workers. The field survey reveals that, i n practice, there are two methods in the shucking process, each using specific shucking knives with different shapes an d dimensions, u sually made by l ocal bl acksmith sh ops. In t otal, 5 different sh ucking knives we re collected. Furtherm ore, the i nterviewed workers als o re ported different i njuries a nd disorders experienced from their work, mainly concentrated on the forearm such as cutting on the palm and fingers, pain on the wrist and forearm. In the second phase, ergonomic hand-tool design principles are used to propose improvements in three redesigns of oyster shucking knife.
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Workers' quality of work life is an important factor which may affect organisational performance and success significantly. The good quality of work life is beneficial in any industry. There is a significant contribution of small scale industries to the economy of India. The focus of this study concerns an evaluation of quality of work life for the workers in handicraft industries of Jaipur. The data related to quality of work life were collected through questionnaire survey from 120 workers of four different handicraft industries of Jaipur (India). The analysis has pointed out that the major factors which influence and decide the quality of work life are working environment, job security and cooperation with co-workers. Ergonomics interventions could improve the quality of work life, reduce musculoskeletal disorders and increase the productivity.
Book
Comfort is increasingly important in sales of cars, hand tools, seats, earth moving machines and airplane tickets. Discomfort is a predictor of musculoskeletal injuries and should be reduced in situations that consume a significant part of our time. However, there is no such thing as a general notion of comfort or discomfort. Therefore, in research on comfort, the end-user of a product must be involved. If its done on the right way the end-user involvement leads to profitable results, which is shown in several cases in this book. This book supports managers, designers and researchers in designing products and work stations to increase sales (by comfort increase) and to reduce musculoskeletal injuries (by discomfort reduction). Theory as well as good practices on comfort and discomfort are described for the first time in one book. Examples come from Japan, USA, Sweden, Germany and the Netherlands. The reader is shown the latest developments in comfort theories on comfort and which factors should be studied to optimise comfort (chapter 1, 2 and 3). The reader gets also the latest knowledge on how to involve participants in comfort research and set up a project (chapter 4). 18 cases (chapter 5 – 22) are described in detail on how discomfort is reduced in a design process or how comfort is improved in this process. Also, on cost/benefits (chapter 23) the reader is informed.