Abstract
BACKGROUND:
The footwear manufacturing industry is one of the significant sectors of leather businesses in India. In the Indian footwear production industry, there is an enormous potential for employment, export, and development. Kolhapuri footwear is a popular handmade craft in India. It is a well-designed craft used by Indian people for many years. Artisans using traditional tools manufacture this footwear manually. Workers of this craft use traditional methods and work in cottage-based enterprises where organized laws and legislations are not applicable. Therefore, any occupational hazard-related documentation is not available. Due to the nature of the job, workers occupy various apparent non-optimal postures that may cause multiple work-related disorders such as musculoskeletal disorders (MSDs).
OBJECTIVE:
The main objective was to study and assess different footwear manufacturing workstations and working postures. The work further aimed to improve the design of current workstations and evaluate the proposed design using virtual ergonomic assessment techniques.
METHODS:
An anthropometric database for the Kolhapuri footwear making population was developed. This work measured 35 different body dimensions of the footwear manufacturing artisans. Rapid Upper Limb Assessment (RULA) was used for postural analysis of the artisans.
RESULTS:
It was observed that the entire footwear making activity was carried out in awkward postures. RULA scores suggested that ‘a change in posture’ to improve the efficiency of artisans was required for most of the workstations. This work proposed a novel workstation design to reduce the high risk of MSDs. The design was evaluated for thigh clearance, vision analysis and RULA analysis with the help of Digital Human Modelling (DHM). The virtual ergonomics assessment of this design revealed that the vision, thigh clearances, and RULA scores were satisfactory in the new design.
CONCLUSION:
The anthropometric database proposed in this study is likely to be useful in designing Kolhapuri footwear manufacturing tools. The proposed workstation and work layout are helpful to improve the accessibility of required tools and materials to footwear workers. It also helps to reduce occupational risks by easing uncomfortable work positions.
Keywords
Introduction
In developing countries, small-scale industries play a significant role in employment and revenue generation [13, 21]. In the Indian economy, footwear plays an extremely vital role. In footwear manufacturing, India is in the second position next to China [1]. In India-crafted footwear like Mojari or Jaipuri juttis, (local name of the footwear) are made from cane and bamboo. The Kolhapuri Chappal (local name of the crafted footwear) is a famous craft of Maharashtra state, India and the most popular handmade footwear. [3]. Footwear manufacturing involves intense manual effort and high repetitions along with low variability in the task [5, 16]. Almeida et al. (2017) [16] observed that working in the footwear manufacturing industry present characteristics (e.g. repetitions, psychological work pressure for high output) that lead to musculoskeletal disorders (MSD) [16]. Asivandzadeh (2018) [2] found a significant correlation between occupational stress and MSD in various industries.
The majority of studies on MSD have been conducted in bag making, jewelry making, the manufacturing sector and the craft industry [3–17]. Some researchers (Afonso et al., 2014 [23]; Dianat and Salimi, 2014 [13]; Almeida et al., 2017 [16]) studied MSD symptoms and related issues among workers associated with footwear industries. They mentioned that an effective approach is required for the prevention of health-related issues in the footwear sector. Dianat and Salimi (2014) studied MSD symptoms and the consequence on workers involved in an Iranian hand-crafted footwear called Giveh, which is very similar to Kolhapuri-crafted footwear in India. They reported a high prevalence of various MSD symptoms, which were mainly associated long periods of continuous work, poor working postures and experiencing stress due to work. They further predicted that ergonomics design intervention of traditional hand tools and workstation may be one of the solutions to overcome the MSD-related problems. Aghali et al. (2012) [7] highlighted various MSDs of shoe manufacturing workers in Iran and recommended improved work postures and training for better execution of tasks to reduce MSDs. From a review of the literature, it was found that workers associated with the manufacturing of footwear have a high prevalence of musculoskeletal symptoms.
Many similar studies were carried out, for instance on squatting postures in bidi making and jewelry manufacturing [9, 12]. It was found that the health hazards such as body ache, low back pain, forearm pain, wrist pain, elbow pain, hand pain, headaches and eyestrain were commonly present in this kind of work [7, 10]. Giri et al. (2012) [10] concluded that in the bag making occupation, large numbers of employees suffered from occupational illnesses, primarily musculoskeletal problems.
Kolhapuri footwear manufacturing is a profession under the family enterprise and is an unorganized sector [4]. The population of these workers is undefined. However, some local (newspapers) sources reported that it involves approximately 7000 workers. There are about seven to eight types of tasks (Fig. 1) for manufacturing Kolhapuri-crafted footwear. The workstation is a small wooden block placed on a marble stone. Once seated, the workers continue their work for three to four hours in the same posture where the total work hours per day are usually more than nine hours. During these long work hours, their knees are folded under their body and operations such as sole/bottom making, skiving, stitching, punching, assembling and preparing various parts require the artisans or workers to incline forward to visualize the details of the work. In short, they work cross-legged in a seated posture on the floor for an extensively long period. In some of the operations like stitching and sole cutting, due to the requirement of large force, artisans experience, amongst others, stress and low back pain as well as ankle and knee problems. During a field visit it was observed that the same workstations are being used for skiving, punching, color pasting and trimming. Therefore, a common multipurpose workstation was designed which will help all workers (apart from stitching, sole and strip cutting) to occupy their traditional seating posture.
Various workstations for Kolhapuri footwear manufacturing.
Salve et al. (2018) [3] observed that while manufacturing Kolhapuri footwear, some processes did not contribute to the workmanship of the footwear and could be eliminated. The majority of the workers were seated in a non-optimal posture indicating that research from a perspective of workstation design to improve efficiency was essential. The main concerns of previous studies were only on the evaluation of work-related health problems. At present, the research studies on MSD symptoms of Kolhapuri footwear manufacturing workers are limited. In this crafted footwear/footwear sewing industry, there is a lot of potential to improve the workers’ quality of life and organizations’ performance [4, 16]. An effective design intervention program and some changes are required immediately with respect to the present working conditions of the Kolhapuri-crafted footwear sector [4]. Therefore, to accomplish this research gap, this study aims to design and analyze the workstation for worker compatibility and postural comfort. To achieve this aim, the following objectives were addressed: (1) To perform postural evaluation of seven tasks using Rapid Upper Limb Assessment (RULA), (2) To measure anthropometric body dimensions of Kolhapuri-crafted footwear, (3) To propose a common design (multipurpose workstation) using workers’ anthropometric body dimensions for the multipurpose workstation, (4) To evaluate the proposed new design of the workstation using Digital Human Modelling (DHM) for other ergonomic aspects (e.g. thigh clearances, vision, reach analysis, etc.).
The study population consisted of Kolhapuri footwear manufacturing workers in the Kolhapur district in the western part of Maharashtra, India. In this district, 15 co-operative societies manufacture Kolhapuri footwear. Thirty-five workers (30 males and 5 females) were selected randomly for the study from seven active societies. The worker population was undefined (since it is an unorganized sector). Therefore, this study followed a random sampling technique. The 35 participants were healthy workers with no medical history.
Institutional ethical board approval was obtained from the Indian Institute of Technology, Guwahati, India prior to the study. The
Postural evaluation was carried using RULA [18]. DHM [22] was used for virtual workstation evaluation. The selection of the different anthropometric body dimensions for seating postures was considered according to the study by Chakrabarti (1997) [19]. Standard calibrated vernier caliper, height gauge and a measuring tape were used for the body measurement (anthropometric data collection) process.
Results and discussions
Demographic and job descriptions of footwear manufacturing workers
Demographic and job descriptions of the crafted Kolhapuri footwear artisans are shown in Tables 1 and 2 respectively. The male artisans’ ages ranged between 18 to 66 years (average 41.1 years; SD =±14.2 years). The age range of females was 21 to 58 years (average 33.6±15.32 years). The footwear manufacturing workers were employed in their current jobs between one to 34 years (average = 13.5 years; SD =±8.8 years). The mean day-to-day occupied working hours were 7.8 (SD =±1.5). Twelve workers (out of 35) worked for more than two hours without a break.
Demographic characteristics of the workers (n = 35)
Demographic characteristics of the workers (n = 35)
Job characteristics of the workers (n = 35)
When making Kolhapuri footwear, the workers fold their knees under the body. They sit on the floor for a long period while performing different tasks. Table 3 presents the RULA [4] action levels. The mean RULA final grand score of seven tasks was 6.4, which clearly indicates a need to investigate and modify the workstations (Fig. 2). The study revealed that there was no significant difference between the RULA score of males (6.8) and females (6.7). The percentage of workers (89%) with a final RULA grand score of 7 revealed that analysis and modifications are essential immediately.
RULA action level
RULA action level
Mean final RULA score of various workstations.
The selection of the different anthropometric body dimensions for seating postures was considered according to the study by Chakrabarti (1997) [1]. All data were collected according to the Helsinki Declaration [20]. The data includes 35 body dimensions of the seating postures. Table 4 presents the list of body dimensions taken and Fig. 3 illustrates the body diagrams.
Anthropometric parameters of the workers
Anthropometric parameters of the workers
Multipurpose workstation design.
The 5th, 50th and 95th percentile, mean (M), coefficient of variation (CV) and standard deviation (SD) of the footwear workers’ anthropometric measurements were calculated and are presented in Table 5.
Anthropometric body dimension of the workers
Anthropometric body dimension of the workers
Table 5 presents the anthropometric measurements for the male and female participants. In the study, several measurements were measured accurately by using the guidelines given by Chakrabarti (1997) [19] with respect to postures mentioned in Fig. 3.
Design intervention of multipurpose workstation for footwear manufacturing workers
The result of the postural analysis revealed that the posture adopted by footwear manufacturing workers needs immediate intervention to enhance the working conditions. The RULA analysis indicated that the majority of the workers are working on different workstations in uncomfortable working postures during Kolhapuri footwear manufacturing. Their current working platform was found to be uncomfortable. This led to uncomfortable or hazardous work postures and body parts discomfort. Therefore, we designed a new workstation table which would be suitable for all workstations by considering various anthropometric dimensions. A common multipurpose workstation was designed which would help all craftsmen (apart from stitching, sole and strip cutting) to occupy their traditional seating posture, although the posture would be closer to natural alignment. Therefore, for changing their current working posture, a suitable workstation table design was provided. The multipurpose workstation was designed for shorter and taller people with height adjustment provision to avoid height mismatch. Local anthropometry data was considered for defining the design dimensions. A new design concept (Fig. 3) of the multipurpose workstation was generated based on the user’s requirement, field survey, nature of work, tools to be used, availability of space and natural (following native culture) way of siting. A computer-aided design (CAD) 3D model of the proposed multipurpose workstation was created using CATIA V5 software.
The multipurpose workstation table is shown in Fig. 3. Figure 4 presents the various design parameters of the workstation table design. The design included the following parts: A. Working surface table (with angular adjustability of D). The overall length is 991 mm, the overall depth is 700 mm and the width is 10 mm). B. Lap chair which can be adopted for buttock and trunk curvatures. C. Angularly adjustable knob for the table leg, which adjusts the angle of the table legs and keeps it stable for regular work. D. Angularly adjustable knob for the table working surface, which adjusts the angle of the table-working surface to keep the working surface comfortable for all percentiles.
Multipurpose workstation table. A-.Working surface table, B. Lap chair, C. Angular adjustable knob for the table leg and D. Angular adjustable knob for the table working surface.
Stature, normal sitting height, erect sitting height, mid shoulder, right knee, elbow to elbow relaxed, knee to knee, right buttock, knee length, arms reach length and heights of these anthropometric parameters were considered for the design of the table and chair for a wide range of users.
The DHM simulation approach was considered for ergonomic analysis of the newly designed multipurpose workstation. A CAD model of the proposed workstation design was created in CATIA V5 software. The clusters in the population covering the smallest, medium and largest body measurements are presented by the 5th, 50th and 95th percentile anthropometry body dimensions respectively. In order to confirm the footwear manufacturing worker’s compatibility with respect to the proposed workstation, the work envelope of different manikins was generated and analyzed.
Thigh clearance DHM analysis of the multipurpose workstation
The suggested multipurpose workstation table models were interfaced with the 5th, 50th and 95th percentile (Fig. 5) DHM for thigh clearance analysis. The thigh clearance between the working surface table frame and thigh is 3.3 mm, 330 mm, and 354 mm for the 95th percentile male, 50th percentile male and 5th percentile female correspondingly. Thus, it was found that the free thigh clearance between all percentiles in the population was satisfactory.
Thigh clearance analysis of the multipurpose workstation design.
The proposed multipurpose workstation model was interfaced with the 95th percentile male, 50th percentile male and 5th percentile female (Fig. 6) DHM for vision analysis (binocular). The focus distance was 300 mm while all three percentiles were interfaced with the proposed workstation. Neck flexion was 18°, 17° and 17° respectively with a focal distance of 300 mm. The majority of the workspaces were visible at a comfortable posture with respect to all percentiles. It was observed that the best visibility of the working surface was obtained within the recommended limit of 25° view cone at 10° head flexion for all percentiles.
Vision analysis.
Comfortable reach to the working surface table helps to maintain proper body postures, as shown in Fig. 7. An unreachable distance of the 95th percentile male from the edge of the table was 3 cm and at 70° from the table working surface angle. Similarly, an unreachable distance of the 50th percentile male from the edge of the table was 4 cm and at 70° degrees from the table working surface angle. Finally, the unreachable distance of the 5th percentile female from the edge of the table was 6 cm and at 70° from the table working surface angle. The nature of work confirms that workers need to perform their task within the midline of the body and keep material closer to the body. Therefore, the unreachable peripheral area will not hamper the craft person’s job.
Reach analysis.
Figures 8, 9 and 10 present virtual presentations of the working postures of the workstation table for the 95th percentile male, 50th percentile male and 5th percentile female respectively. The final score is 3 (i.e., acceptable) for both the right and left side, which is an acceptable value for all mentioned percentile populations. The results observed are as follows: RULA grand score of 3 each for all the 95th, 50th and 5th percentiles, which indicates a negligible risk level in certain design conditions.
Virtual presentation of the working posture of the multipurpose workstation, 95th percentile male.
Virtual presentation of working posture of multipurpose workstation 50th percentile male.
Virtual presentation of the working posture of the multipurpose workstation table, 5th percentile female.
Group work layout design based on workers’ cross-legged posture parameters
Figure 11 presents the layout design based on the collected parameters of workers seated on the ground in cross-legged postures. In this layout, all the arrangements such as shelves for their tools and raw material placement have been provided.
Layout design.
Figures 12 and 13 present the work layout design of all workstations. In this layout, shelf arrangement is provided between two workstations so that different hand tools and materials can be shared with each other. In this analysis, upper position length posture, upper position height posture, mid position length posture and mid position height posture are considered for the analysis.
Work layout design.
Work layout design.
These anthropometric parameters were considered for designing the work layout for all users (5th female, 50th pooled and 95th male percentiles). Among these percentiles, the 5th female human body dimensions were considered as a small body dimension for analysis. Using this percentile, a reach analysis was performed. Results found that hand reach of 5th female percentiles to take tools and raw material was considered good.
Figures 14 and 15 present the reach analysis of sharing tools with the shelf of the 5th female percentile and tray reach analysis of the 5th female percentile, respectively. Therefore, this layout will definitely help to improve productivity as well as to improve posture.
Tray reach of the 5th percentile female.
Sharing tool shelf reach of the 5th percentile female.
In this study, the design proposal and its evaluation for Kolhapuri-crafted hand-sewn footwear were presented. Awkward working postures of the workers involved in various tasks were identified. RULA analysis of the workers working on the different workstations was carried out. A virtual workplace (multipurpose workstation) was produced with the assistance of a CAD model and DHM. Different anthropometric parameters were considered for the design of the workstation table and layout design for all users. The workstation table was designed keeping in mind the ergonomic considerations. The final RULA score value after the analysis was reduced to 3, hence it eliminated uncomfortable postures. Thigh clearance and vision analysis were carried out in DHM software for the designed table. Satisfactory results were obtained with respect to all workstation table designs.
The working postures for the workstation table were acceptable and the proposed table design for all workstations can be implemented in a family enterprise type of business or home-based workshop. The methodology presented in this study can be implemented to various workstations to reduce or eliminate health-related risks. It is suggested that the newly developed multipurpose workstation design can be easily adapted for creating Kolhapuri footwear. The newly proposed work layout would be beneficial for productivity improvement. This new design of the multipurpose workstation table and work layout would improve the accessibility to footwear workers and would further reduce occupational risks.
Limitations
In this study, a new design of a multipurpose workstation has been proposed. The proposed design intervention is mainly based on the operation and workers’ wellbeing from an ergonomics perspective. In this new design, the next phase is to execute finite element analysis, which can help find performance and stability of the multipurpose workstation. The actual execution of the proposed design may not be possible at this stage of design.
Conflict of interest
None to report.
Footnotes
Acknowledgments
The authors express their honest appreciation to all the footwear manufacturing workers who rendered enormous assistance during the completion of this study.