The study starts with the identification and investigations of different tasks related to the production of bell metal items. The study progressed with a collection of drudgery data associate with the artisans working in the bell metal items production centers. Finally, an ergonomically correct workstation along with plausible dimensions of a few tools/ equipment commonly used in the bell metal production centers has been presented.
6.2.1 Task characteristics
Bell metal products manufacturing techniques were observed to start with the casting task, followed by the forging and cleaning task. These tasks are classified as follows a) task 1- casting, melting of old scrap material at a temperature of nearly 1200ºC in an open charcoal
furnace (Fig. 6.1a), b) task 2 - forging at a temperature between 600 – 800ºC using a hammer of weight 1.5 – 2kg (Fig. 6.1b) and c) task 3 – surface cleaning to remove the oxide layer by using a locally manufactured tool (Fig. 6.1c). The average total working hours per day was found to be 12hr.
Figure 6.1 Different manufacturing techniques: a) Casting, b) Forging, c) Cleaning Different body part movements and postures involved during performing each task were identified according to the method proposed by Keyserling et al. (1992) [249] and the results were found as follows:
a) For “task 1”, the trunk of the workers bent forward at some angle (i.e., flexion/
extension) accompanied with side bending. Few workers adopted a posture similar to squatting with flexion of the trunk.
b) For “task 2”, one of the arms moves from the top of the head to chest level (i.e., the arm moves almost 90º) while holding a hammer. However, for heavy work, the arm moves from the top of the head to almost ground level (i.e., the arm moves almost 160º). The other arm remains constant in the power zone for holding the job in red hot
condition. During forging, the trunk repeatedly flexions accompanied by side bending and the arms work across the side of the body.
c) For “task 3”, both the hands are continuously engaged in holding the tool and the feet are used to provide support to the product. During cleaning, the trunk repetitively flexions to cover the whole surface and the arms work across the midline of the body.
6.2.2 Drudgery data collection and analysis
For this study, 40 male workers were randomly selected from 20 different bell metal items production units located in Sarthebari. The drudgery data i.e., discomfort/ pain in various body parts, were collected through the questionnaire-based interviews by following the World Medical Association of Helsinki protocol as described by Rennie (2013) [191]. The Borg scale was used to collect the data on body discomfort and determine the occurrences and intensity of pain in the workers various body parts as described in chapter 2.
Again, Sanjog et al. (2019) [112] study shows that artisans experience maximum drudgery on the lower back (82.6%), shoulder (56.5%), wrist (52.2%) and knee (34.8%).
Dewangan and Singh (2015) [117] have reported that artisans experience maximum drudgery on the lower back (80%), shoulder (80%), neck (60%) and upper back (50%). Kushwaha and Kane (2016) [118] have found that artisans experience maximum discomfort in operator hip/thigh (66.6%), upper back (66.6%), neck (62.9%), knee (59.25%), lower back (51.8%), shoulders (44.4%), forearm (33.3%) and wrist (29.6%). Further, Chohan and Bilga (2011) [250] have reported eye infections of 32.5% of artisans working in a small scale steel plant located in Ludhiana, Punjab. Hence, the drudgery data of shoulders, forearms, upper arms, neck, lower back, upper back, wrists, thigh, knee joint and eye of the workers have only been collected. The collected data also consists of personal information like age, weight, grip force, etc. as described in chapter 2.
Collected drudgery data were analyzed by taking the discomfort scores less than 3 as
"no discomfort" and score greater than equal to 3 as "discomfort" as described by Meksawi et al. (2012) [193]. The responses of the workers were analyzed for ascertaining the prevalence of discomfort as described in chapter 2. The workers reporting any earlier history of discomforts because of accidents, diseases or any other injuries are excluded from this study.
6.2.3 Digital human modelling
The working postures of the workers have been evaluated using direct observations at the workstations and then the ergonomic analysis has been carried out by using Digital Human
Modelling as described in chapter 2. Since, in all the production techniques, the upper limbs were mainly involved, Rapid Upper Limb Assessment (RULA) score was used as recommended by McAtamney and Corlett (1993) [251] to ascertain the level of ergonomic risks involved with the adopted awkward postures and the urgency of intervention. In RULA technique, score is calculated based on kinematics and loading effects of users [252]. RULA score has already been used by Singh et al. (2012) [113] and Singh (2012, 2010) [110, 111]
to assess the ergonomic risks involved with the kind of postures and forces involved in the casting and forging industries as they often lead to pain related drudgeries of workers.
6.2.4 Workstation design
The modified systematic layout planning (MSLP) (see Fig. 1.6) has been used to design the workstation for the removal of drudgeries from the industry and hence, for achieving a healthy worker posture, as discussed in chapter 2. The principle of “designing for adjustable range”
proposed by Taifa and Desai (2017) [172] has been used for designing the tools and equipments of the workstation. Again, Somatotype, i.e., covering the extreme range of endomorph to ectomorph dimensions recommended by Tilley (1993) [195], has been used to design the workstation.