RIGHT AND LEFT HAND MOTION ANALYSIS OF SEWING MACHINE OPERATOR

1. Masters in Fashion Technology, Department of Fashion Technology, National Institute of Fashion Technology, New Delhi, India. 2. Doctorate in Philosophy, Department of Fashion Technology, National Institute of Fashion Technology, New Delhi, India. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History Received: 20 May 2020 Final Accepted: 24 June 2020 Published: July 2020

Textile and Apparel Industry second largest employment generation sector, after agriculture gives a safe place to work as compared to other manufacturing industries. But hazards and injuries faced by operators here are not fatal immediate but subtle and grow with period of time. Repetitive motions with high frequency make sewing operations ergonomic vulnerable. In this study the authors have focussed on left and right hand motions of sewing operators. Selected six different operations based on type of operation and number of plies to be attached. With the help of markers specific body parts distinguished with other body parts. Digital Camera used for capturing videos. Data Analysis (Human motion Tracking and Simulation) done by open source physics available software named Tracker. With the help of Autotracker feature of software all motions of body part analysed in every frame of video. Graph and table plotted for the x-position, yposition with respect to time. Principles of Motion economy given by International Labour Organisation (ILO, Geneva) are also verified in this paper. After analysing results and calculating distance travelled, different statements concluded like left hand moves more than right hand. Left hand never crosses needle point but right hand crosses. All pivots of hand move in synchronise with each other just the magnitude varies, finger with most movement and shoulder with lowest.

Introduction:-
The clothing industry is generally seen as a safe place to work. Compared to other industries, there are relatively few serious accidents in clothing plants. The hazards we face are different. The major health risks in this industry do not arise from immediate, potentially fatal hazards. Instead, the risks that clothing workers face come from more subtle hazards whose effect accumulates over time. Research shows that sewing machine operators face a substantially higher risk of muscle pain and injury than workers in other jobs. Studies also show that the frequency of persistent neck and shoulder injuries increases with years of employment. One report found that sewing machine operators experience as many cases of repetitive strain injuries as data entry keyers and secretaries combined. These injuries lead to long-term health effects. (Gunning, et al., 2001) 943 As per Principles of Motion Economy, there are some sets of human body motions. They are: 1. The two hands should begin and complete their movements at the same time.
2. The two hands should not be idle at the same time except during periods of rest. 3. Motions of the arms should be symmetrical and in opposite directions and should be made simultaneously. 4. Hand and body motions should be made at the lowest classification at which it is possible to do the work satisfactorily. 5. Momentum should be employed to help the worker, but should be reduced to a minimum whenever it has to be overcome by muscular effort. 6. Continuous curved movements are to be preferred to straight-line motions involving sudden and sharp changes in direction. 7. "Ballistic" (i.e. free-swinging) movements are faster, easier and more accurate than restricted or controlled movements. 8. Rhythm is essential to the smooth and automatic performance of a repetitive operation. The work should be arranged to permit easy and natural rhythm whenever possible. 9. Work should be arranged so that eye movements are confined to a comfortable area, without the need for frequent changes of focus. (Kanawaty, 1992)  It is obvious that each movement above Class 1 will involve movements of all classes below it. Thus the saving in effort resulting from using the lowest class possible is obvious. If, in laying out the workplace, everything needed is placed within easy reach, this will minimize the class of movement which the work itself requires from the operative (Kanawaty, 1992) 944

Background Study:
Ergonomics aims at preventing injuries by controlling the risk factors such as force, repetition, posture and vibration that can cause injuries to develop. Some fundamental ergonomic principals that should be followed in our workplaces are: 1. Use proper tools 2. Keep repetitive motions to a minimum 3. Avoid awkward postures 4. Use safe lifting procedures 5. Get proper rest (Gunning, et al., 2001) Two Handed Process Chart: The Left and Right Hand Chart is a process chart in which the activities of a worker's hands (or limbs) are recorded in their relationship to one another. It is a specialized form of process chart because it shows the two hands (and sometimes the feet) of the operative moving or static in relation to one another, usually in relation to a time scale. It is generally used for repetitive operations, when one complete cycle of the work is to be recorded.

Objectives of Two Handed Process Chart:
1. The very act of making this chart enables the work study specialist to gain an intimate knowledge of the details of the job and study each element of the job the relationships between two different activities can be established 2. The aim of this chart is to eliminate or reduce the unwanted motion to minimum 3. Give ideas for improvements and to arrange the best of motions in a possible sequence (Two Handed Process Chart) With Two Handed Process Chart we can determine the different motions performed by right and left hand simultaneously.

Human Motion Analysis and Simulation:
Given the range of human motion related applications, there are numerous techniques that can be used to capture the human motion, to process the resulting data and also to simulate it, each one with its own strengths and weaknesses. For each application scenario it is possible to select the techniques that best fit its constraints and specific needs (e.g.: budget, scene conditions, available equipment and software, etc.    Video captured were uploaded to Tracker, then after calibration of video frames, movement of different specific marked points was tracked by Autotracker function of this software.
Origin can be set with correspondence to sewing table length or width which was also used for calibrating video frames.
With the help of origin, different graphs, tables, plots can be plotted for different parameter such as x-position, yposition, displacement, velocity, acceleration, angular velocity, potential energy, kinetic energy, vector etc. with respect to frame number.

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All the available data can be extracted to excel file to calculate the distance travelled by different parts of hand during the sewing operation.
The Pythagorean Theorem provides an easy way to compute the straight line distance between any two points whose Cartesian coordinates are known. (Gutierrez)   Table 1:-Classification of movements.

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All the available data extracted to excel file to calculate the distance travelled by all the five points.

Principle of Motion Economy:
The data (x and y co-ordinates of Left Hand and Right Hand with Needle point as origin) can be used for analysis of checking for Principles of Motion Economy.
The two hands should begin and complete their movements at the same time.
The two hands should not be idle at the same time except during periods of rest.
The above two points can be checked by calculating the distance between two consecutive co-ordinates. If the coordinates of both hands are changing at the starting time and ending time that means both hand motions are beginning and terminating at the same time.
For Checking if any of the hand is idle, the consecutive co-ordinates can be checked. If the co-ordinates are same that means idle (no change).
Motions of the arms should be symmetrical and in opposite directions and should be made simultaneously.
By symmetry, it means that both hand motions should be mirror image to each other. So taking origin and X and Y Axes as mirror it can be used to analyse when both hands are coming towards origin or vice-versa.
The distance of each co-ordinate from origin can be calculated by distance formula. Then for every consecutive coordinate of Right Hand and Left Hand at same timeframe, it can be identified that distance is increasing or decreasing i.e. coming towards the origin or going forwards the origin.
If the distance is either increasing or decreasing in both the hands (condition should be same in both hands), then it is symmetrical otherwise asymmetrical (i.e. one increasing and other decreasing).
Calculation of number of points in the normal and extended reach area (i.e. the primary and the secondary area) As discussed earlier needle point is taken as the origin for all co-ordinates. In the above figure 10, operator is sitting at a distance of 20 cm from sewing If the distance is more than 40 cm (i.e. the range of primary area) and the co-ordinates are outer the primary area range, those points were separately counted to find out how many points are outside primary range.

Principles of Motion Economy:
As the distance between the origin and the consecutive co-ordinates for both the hands was changing at the beginning and ending, it can be stated that in all six operations Right and Left Hand start and end moving together.
The difference between two consecutive co-ordinates was never zero in all six operations, it can be stated that both hands were not at idle position instead of rest time.
Symmetry of both hands can be identified by comparing the increasing and decreasing values of consecutive coordinates for both hands. If both are in same direction i.e. either increasing or decreasing then both hands motion is symmetrical otherwise asymmetrical. The number of points outside the primary area was calculated by defining the centre and radius of the primary area and distance of each co-ordinate with respect to centre of primary area.

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4. This software and method can be used for calculating difference between standing and sitting operations (For Example if a same operation can be performed standing and sitting, which is more accurate ergonomically can be identified) 5. Not only sewing operations, but other operations in Cutting and Finishing Department can also be analysed. 6. Can be used for designing ergonomic work station as per minimum movements of five points. 7. The Five Point Motion Analysis can be used for MODAPTS. 8. MODAPTS stand for MODular Arrangement of Pre-determined Time Standards. 9. It differ from others as it focus on the body part doing the moving rather than the distance covered by the body part of the object being handle. 10. Just the distance travelled by different parts calculated and is multiplied to the respective code (Jana & Tiwari, 2018)