Applications of Principles of Motion Economy

Application of motion economy Principles

2013 APPLICATIONS OF PRINCIPLES OF MOTION ECONOMYY

Wubshet Abide BAHIR DAR UNIVERSITY INSTITUTE OF TECHNOLOGY 1/1/2013

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Table of Contents Summery ............................................................................................................................................... v PART ONE: INTRODUCTION ........................................................................................................... 1 1.1

What is productivity? ............................................................................................................. 1

1.2

Symptoms of low productivity ............................................................................................... 1

1.3

Method and time study ........................................................................................................... 1

1.4

What Is Motion Economy? ..................................................................................................... 2

PART TWO: CLASSIFICATION PRINCIPLES OF MOTION ECONOMY .................................... 3 2.1

Principles of motion economy as related to the use of human body ...................................... 3

2.2

Principles of motion economy as related to the arrangement of the workplace ..................... 7

2.3

Principles of motion economy as related to the Design of Tools & Equipment .................. 15

2.4

Two or more tools should be combined wherever possible. ................................................ 17

PART THREE: APPLICATION AREAS OF MOTION ECONOMY PRINCIPLES....................... 20 3.1

Application of motion and time study in hospitals .............................................................. 20

3.2

General motors ..................................................................................................................... 25

3.3

Experiment on motion study ................................................................................................ 26

3.4

Limitations of Motion Economy .......................................................................................... 29

REFERENCES .................................................................................................................................... 30 Index .................................................................................................................................................... 31 Key definitions ................................................................................................................................ 31 Motion-Economy Device Design - Important Devices ................................................................... 32

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Application of motion economy Principles List of figures Figure 1 Normal line of sight ................................................................................................................................................ 7 Figure 2 a) properly designed Gravity-feed, bins and containers b) poorly designed.......................................................... 9 Figure 3 Standard bins of the gravity-feed type .................................................................................................................. 10 Figure 4 dimensions of normal and maximum working area in the horizontal plane for males ......................................... 11 Figure 5 dimensions of normal and maximum working area in the horizontal plane for females ...................................... 11 Figure 6 Normal and maximum working space in three dimensions .................................................................................. 12 Figure 7a) poor & b) Good arrangement of parts and tools in workplace ......................................................................... 13 Figure 8

Adjustable chair ................................................................................................................................................ 14

Figure 9 working conditions ............................................................................................................................................... 15 Figure 10 Foot operated soldering iron.............................................................................................................................. 17 Figure 11 multiple-spindle air operated nut runner ........................................................................................................... 17 Figure 12 Results of the study of lever ................................................................................................................................ 18 Figure 13 Results of the study of hand wheels .................................................................................................................... 19

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Application of motion economy Principles Summery The main target of every business wither it is manufacturing or service industry is improving Productivity. It is about the effective and efficient use of all resources. Resources include time, people, knowledge, information, finance, equipment, space, energy, materials. Some firms fail to compete with others in the era of globalization due to low productivity. The following symptom tells us our firm is operating in lower productivity level. Such as congested space, wasted resources, variable quality, no accurate cost estimates, etc. at this time companies must consider introducing industrial engineering concepts in their business. Work study and Methods engineering is among the most important applications of industrial engineering concepts. Particularly principles of Motion economy will help industries to improve their productivity. The heart of this paper is applications of motion economy principles. This has three main categories; Principles of motion economy as related to the use of human body, arrangement of the workplace and design of tools & equipment. On the last part of this paper some application areas of motion economy principles have been discussed. Motion economy principles has a wide range of applications today including the application in operating theatres in hospitals , improvement in bricklaying techniques, for manufacturing industries .It was not a friendly time at General Motors after a 113-day strike in the winter of 1945-46 the fantastic exiting gate from such harsh condition was applying motion economy principles in their organization.

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PART ONE: INTRODUCTION 1.1 What is productivity? Productivity is about the effective and efficient use of all resources. Resources include time, people, knowledge, information, finance, equipment, space, energy, materials. Productivity is often linked with “time and motion”. The evidence of time and motion studies was used to put pressure on workers to perform faster. Not surprisingly these studies had a bad press as far as workers were concerned. Similarly the image of “time and motion” doesn’t sit well with us as productivity specialists. 1.2 Symptoms of low productivity If you can identify with any of these issues in your business, your productivity level will be adversely affected. congested space

rejects and returns

wasted resources

excessive equipment downtime

variable quality

inadequate overhead recovery

no accurate cost estimates

shortfall in targets

no obvious work flow

under-recovered investment costs

high inventory levels

cost

high levels of overtime missed deadlines constantly moving things

variances

in

manpower

and

materials inaccurate staffing levels lack

of

appropriate

productivity

measures

If you can identify with any of these issues in your business, then you should consider making changes. Changing the method of doing things is could be the one w 1.3 Method and time study Because it’s the method that determines the time needed for any activity, the whole emphasis has changed over the years. The 21st century equivalent of the time and motion study is more literally a method and time study. This is a more far-reaching philosophy and approach to managing a business.

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When everyone is focused on better and leaner processes the methods improve, time is reduced and more value is added. This - with continuous improvement - means activities become more streamlined and Lean. Lean means that anything wasteful is shown the bin! (Movement, time, materials, space) When improvements and Lean initiatives are identified and implemented, workers can often benefit from less stressful working conditions, less fatigue - potentially better rewards, maybe in the form of different hours, increased pay and job satisfaction. It can be a win-win situation. 1.4 What Is Motion Economy? Motion Economy Also called “the characteristics of easy movement” as per the British Standards Glossary of Terms in Work Study. Developed by Frank Gilbreth, the founder of motion study. Motion economy deals with generating and improving plans for a certain group of simple tasks in industries. Given a desired configuration of the product and/or arrangement of the workplace, a motion economy specialist tries to generate a plan, which is composed of fundamental hand motions and is economic from the point of view of motion economy expertise. The tasks, which are in the scope of motion economy, may be classified as manual operations. Operations, which require the use of arms on a limited space for completion, are defined as manual operations. They do not require traveling of the worker, use of the body parts other than arms and hands, like foot or trunk. Manual operations may take place in production systems, as well as daily life. In many industries, there are production sequences, which require simple manual operations. Although there is a trend to eliminate these kinds of jobs in a production system by having industrial manipulators do the job instead, manual operations continue to occupy a major part of working hours. Manual operations take place not only in production systems. Work methods design deals with both process planning and design of the operation method. Frank Gilbreth is acknowledged as the pioneer of the field of scientific management. A field later made popular by F.W. Taylor. Fine-tuned by Prof. Ralph M. Barnes (in his book Motion and Time Study: Design and Measurement of Work). Motion economy helps to achieve productivity and reduce Cumulative Trauma at the workstation or sub-micro level. The Principles of Motion Economy eliminate wasted motion, ease operator tasks, reduce fatigue and minimize cumulative trauma such as Carpal Tunnel and tendonitis.

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PART TWO: CLASSIFICATION PRINCIPLES OF MOTION ECONOMY These principles can be helpful in work design, in reducing the human fatigue and in improving the work efficiency. According to Barnes, these can be presented under following THREE subgroups: 1. Principles of motion economy as related to the use of human body 2. Principles of motion economy as related to the arrangement of the workplace 3. Principles of motion economy as related to the design of tools & equipment 2.1 Principles of motion economy as related to the use of human body 2.1.1

The two hands should begin and complete their movements at the same time.

The natural tendency of most people is to use their preferred hand (right hand for right-handed people and left hand for left-handed people) to accomplish most of the work. The other hand is relegated to a minor role, such as holding the object, while the preferred hand works on it. This first principle states that both hands should be used as equally as possible. This reason is that both hands reinforce the effectiveness of work and helps in minimizing the time for a particular task. To implement, it is sometimes necessary to design the method so that the work is evenly divided between the right-hand side and the left-hand side of the workplace. In this case, the division of work should be organized according to the following principle. The work should be designed to emphasize the worker’s preferred hand: The preferred hand is faster, stronger, and more practical. If the work to be done cannot be allocated evenly between the two hands, then the method should take advantage of the worker’s best hand. For example, work units should enter the workplace on the side of the worker’s preferred hand and exit the workplace on the opposite side. The reason is that greater hand-eye coordination is required to initially acquire the work unit, so the worker should use the preferred hand for this element. Releasing the work unit at the end of the cycle requires less coordination. This principle follows from the first. To implement, it is sometimes necessary to design the method so that the work is evenly divided between the right-hand side and the left-hand side of the workplace. In this case, the division of work should be organized according to the following principle.

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2.1.2

The two hands should not be idle at the same time.

The work method should be designed to avoid periods when neither hand is working. It may not be possible to completely balance the workload between the right and left hands, but it should be possible to avoid having both hands idle at the same time. The exception to this principle is during rest breaks. The work cycle of a worker-machine system may also be an exception, if the worker is responsible for monitoring the machine during its automatic cycle, and monitoring involves using the worker’s cognitive senses rather than the hands. If machine monitoring is not required, then internal work elements should be assigned to the worker during the automatic cycle. 2.1.3

Motions of the arms should be symmetrical and in opposite direction and should be made simultaneously

This will minimize the amount of hand-eye coordination required by the worker. And since both hands are doing the same movements at the same time, less concentration will be required than if the two hands had to perform different and independent motions. 2.1.4

Hand and body motions should be made at the lowest classification at which it is possible to do the work satisfactorily.

Table 1 Basic body motions

High Speed &Precision

Class

Pivot

Body parts moved

1

Knuckle

Fingers(F)

2

Wrist

Hand (H)+ F

3

Elbow

Forearm(FA) + H+F

4

Shoulder

Upper arm(UA) + FA+H+F

5

Trunk

Torso + UA+FA+H+F

•

1rst class: finger motions,

Low force

Example: typing, grasping small parts. 2nd class: also wrist motions, Example: positioning a part 4


3rd class: also forearm motions, Example: placing a small part in a bin 4th class: also upper arm and shoulder motions, Example: reaching object on high shelf 5th class: whole body motions: leg, trunk, High force

Low Speed & Precision

Example: lifting a heavy box. 2.1.5

Momentum should be employed to help the worker, but should be reduced to a minimum whenever it is to overcome by muscular effort.

The momentum of an object is defined as its mass multiplied by its velocity. In the factory environment, the total weight moved by the operator may consist of the weight of the material moved, the weight of the tools moved, and the weight of the part of the body moved. It should be a real possibility to employ momentum to advantage when a forcible blow or stroke is required. The motions of the worker should be so arranged that the blow is delivered when it reaches its greatest momentum. When carpenters strike a nail with a hammer, they are using momentum, which can be defined as mass times velocity. Imagine trying to apply a static force to press the nail into the wood. Not all work situations provide an opportunity to use momentum as a carpenter uses a hammer, but if the opportunity is present, use it. The previous principle dealing with smooth continuous curved motions illustrates a beneficial use of momentum to make a task easier. 2.1.6

Continuous curved motions are to be preferred to straight line motion involving sudden and sharp changes in direction.

It takes less time to move through a sequence of smooth continuous curved paths than through a sequence of straight paths that are opposite in direction, even though the actual total distance of the curved paths may be longer (since the shortest distance between two points is a straight line). The reason behind this principle is that the straight-line path sequence includes start and stop actions (accelerations and decelerations) that consume the worker’s time and energy. Motions consisting of smooth continuous curves minimize the lost time in starts and stops.

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2.1.7

Ballistic (free-swinging) motions are faster, easier, and more accurate than restricted or controlled motions.

Ballistic movements are fast, easy motions caused by a single contraction of a positive muscle group, with no antagonistic muscle group contracting to oppose it. A ballistic stroke may be terminated by the contraction of opposing muscles, by an obstacle, or by dissipation of the momentum of the movement, as in swinging a sledge hammer. Ballistic movements are preferable to restricted or controlled movements 2.1.8

Work should be arranged to permit an easy and natural rhythm wherever possible

Rhythm refers to motions that have a regular recurrence and flow from one to the next. Rhythm is essential to the smooth and automatic performance of any operation. Rhythm, as in a regular sequence of uniform motions, aids the operator in performing work. A uniform, easy, and even rate of work is aided by proper arrangement of the workplace, tools, and materials. Proper motion sequences help the operator to establish a rhythm that helps make the work a series of automatic motions where the work is performed without mental effort. Basically, the worker learns the rhythm and performs the motions without thinking, much like the natural and instinctive motion pattern that occurs in walking. 2.1.9

Eye fixations should be as few and as close together as possible

Work should be arranged so that eye-movements are confined to a comfortable area, without the need for frequent changes of the focus. Where visual perception is required, it is desirable to arrange the task so that the eyes can direct the work effectively. The workplace should be laid out so that the eye fixations are as few and as close together as possible. In work situations where hand-eye coordination is required, the eyes are used to direct the actions of the hands. Eye focus occurs when the eye must adjust to a change in viewing distance. For example: from 25 in. to 10 in. with little or no change in line of sight. Eye travel occurs when the eye must adjust to a line-of-sight change. For example, from one location in the workplace to another, but the distances from the eyes are the same. Since eye focus and eye travel each take time, it is desirable to minimize the need for the 6


worker to make these adjustments as much as possible. This can be accomplished by minimizing the distances between objects (e.g., parts and tools) that are used in the workplace.

Normal line of sight is 15 degrees below horizontal,

Visual field is defined by a cone,

Head movements are minimized if eye fixations are limited imited to a single cone.

Figure 1 Normal line of sight 2.1.10 The he method should be designed to utilize the worker’s feet and legs when appropriate: The legs are stronger than the arms, although the feet are not as practical as the hands. The work method can sometimes be designed to take advantage of the greater strength of the legs, for example, in lifting tasks. 2.2 Principles of motion economy as related to the arrangement of the workplace 2.2.1

Definite and fixed po positions/stations sitions/stations should be provided for all tools and materials to permit habit formation. 7


There should be a definite and fixed place for all tools and materials. The operator should always have tools and materials in the same location, and finished parts and assembled units should be placed in fixed positions or locations. For example, in the assembly of mechanical hardware, the hand should move without mental direction to the bin containing flat washers, then to the bin containing lock washers, then to the bin containing bolts, and finally to the bin containing hex nuts. There should be no thinking required on the part of the operator to do any of this. As the saying goes, “a

place for everything, and everything in its place.” The worker eventually

learns the fixed locations, allowing him to reach for the object without wasting time looking and searching. 2.2.2

Tools and materials should be pre-positioned to reduce searching.

In the horizontal plane, there is a definite and somewhat limited area that the worker can use with a normal expenditure of effort. This includes a normal working area for the right hand and one for the left hand for each working separately, and another for both hands working together. Figure 5 and 6 shows this and the dimensions of normal and maximum working areas in the horizontal and vertical planes. 2.2.3

Gravity-feed, bins and containers should be used to deliver the materials as close to the point of use as possible.

This can sometimes be accomplished by using parts bins with sloping bottoms that feed parts by gravity to the front of the bin, eliminating the need for the assembly operator to reach down into the bin to grasp parts. A gravity feed bin is a container that uses gravity to move the items in it to a convenient access point for the worker. One possible design is shown in Figure (a). It generally allows for quicker acquisition of an item than a conventional rectangular tray shown in Figure (b).

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Fig 2a

Fig 2b

Figure 2 a) properly designed Gravity-feed, bins and containers b) poorly designed

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Figure 3 Standard bins of the gravity-feed type 2.2.4

Tools, materials, and controls should be located within the ‘maximum working area’ and as near to the worker as possible.

This helps to minimize the distances the worker must move (travel empty and travel loaded) in the workplace. In addition, any equipment controls should also be located in close proximity. This guideline usually refers to a normal and maximum working area, as shown in Figure 2a. It is generally desirable to keep the parts and tools used in the work method within the normal working area, as defined for each hand and both hands working together. If the method requires the worker to move beyond the maximum working area, then the worker must move more than just the arms and hands. This expends additional energy, takes more time, and ultimately contributes to greater worker fatigue.

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Figure 4 dimensions of normal and maximum working area in the horizontal plane for males

Figure 5 dimensions of normal and maximum working area in the horizontal plane for females

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Figure 6 Normal and maximum working space in three dimensions

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Figure 7a) poor & b) Good arrangement of parts and tools in workplace 2.2.5

‘Drop deliveries’ or ejectors should be used wherever possible, so that operators do not have to use his/her hands to dispose of the finished work.

The drop chutes should lead to a container adjacent to the worktable. The entrance to the gravity chute should be located near the normal work area, permitting the worker to dispose of the finished work unit quickly and conveniently. They are most appropriate for lightweight work units that are not fragile. This requires configuring the work-place, for example, so that finished units may be disposed of by releasing them in the position in which they are completed, delivering them to their next destination

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by gravity. Besides the savings in time, this frees the two hands so that they may begin the next cycle immediately without breaking the rhythm 2.2.6

Provision should be made for adequate lighting and, a chair of the type of height to permit good posture should be provided.

The height of the workplace and seat should be arranged to allow alternate standing and sitting. This usually means an adjustable chair that can be fitted to the size of the worker. The adjustments usually include seat height and back height. Both the seat and back are padded. Many adjustable chairs also provide a means of increasing and decreasing the amount of back support. The chair height should be in proper relationship with the work height. An adjustable chair for the workplace is shown in Figure 8.

Figure 8 2.2.7

Adjustable chair

The color of the workplace should contrast with that of the work and thus reduce the eye-fatigue. 14


The issue of illumination is normally associated with ergonomics. However, illumination has long been known to be an important factor in work design. Illumination is especially important in visual inspection tasks.

W orking Conditions T em perature & Ventilation H um idity

Illum ination

Noise & Vibration

Safety

C olor

Work Breaks

Causes of Accidents

Figure 9 working conditions 2.3 Principles of motion economy as related to the Design of Tools & Equipment 2.3.1

The hands should be relieved of all work of “holding” the work-piece where this can be done by a jig, fixture or foot-operated device.

JIGS, TOOLS AND FIXTURES 15


"A Jig holds parts in an exact position and guides the tool that works on them.""A Fixture is a less accurate device for holding parts which would otherwise have to be held in one hand while the other worked on them." The designer's object in providing jigs and fixtures is primarily accuracy in machining or assembly. Often, opening and closing them or positioning the workplace calls for more movements on the part of the operative than are strictly necessary. For example, a spanner may have to be used to tighten a nut when a wing nut would be more suitable. Some points worth noting are: 1. Clamps should be as simple to operate as possible and should not have to be screwed unless this is essential-for accuracy of positioning. If two clamps are required they should be designed for use by the right and left hand sat the same time. 2. The design of the jig should be such that both hands can load parts into it with a minimum of obstruction. There should be no obstruction between the point of entry and the point from which the material is obtained. 3. The action of unclamping a jig should at the same time eject the part, so that the additional movements are not required to take part out of the jig. 4. Where possible on small assembly work’ fixtures for a part which does not allow of two-banded working should be made to take two parts, with sufficient space between them to allow both bands to work easily. 5. In some cases jigs are made to take several small parts. This may save loading time if several parts can be clamped in position as quickly as one. 6. The work-study man should not ignore machine jigs and fixtures such as milling jigs. A great deal of time and power is often wasted on milling machines owing to the fact that parts are milled one at a time when it may be quite feasible to mill two -or more at once. 7. If spring-loaded disappearing pins are used to position components, attention should be given to their strength of construction. Unless the design is robust such devices tend to function well for a while but then have to be repaired or redesigned. 8. In introducing a component into a jig it is important to ensure that the operator should be able to see what he is doing at all stages; this should be checked before any design is accepted. The recording techniques of two-handed process chart and multiple activity charts proves very useful in improvement studies of work place layout. In certain type of operations and particularly those with very short cycles which are repeated thousands of times (such as sweet packing or electronic assembly). It may be required to go into greater details of study to save on movement of hands and efforts and to develop best possible pattern of movement, thus enabling the operator to perform the

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operation repeatedly with a minimum of effort and fatigue. The techniques used for this purpose frequently make use of filming and are known as 'Micro motion Study'

Figure 10 Foot operated soldering iron 2.4 Two or more tools should be combined wherever possible.

Figure 11 multiple-spindle air operated nut runner 2.3.2

Where each finger performs some specific movement, as in typewriting, the load should be distributed in accordance with the inherent capacities of the fingers. 17


2.3.3

Handles such as those on cranks and large screw drivers should be so designed that as much surface of the hand as possible can come in contact with the handle.

This is especially necessary when considerable force has to be used on the handle. 2.3.4

Levers crossbars and hand-wheels should be so placed that the operator can use them with the least change in body position and the largest mechanical advantage.

Figure 12 Results of the study of lever

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Figure 13 Results of the study of hand wheels

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PART THREE: APPLICATION AREAS OF MOTION ECONOMY PRINCIPLES 3.1 Application of motion and time study in hospitals Time and motion study has a wide range of applications today (Burguer 2008), including the application in operating theatres in hospitals (Burguer 2008; Leedal & Smith 2005). Through proper application of the principles of time and motion study, surgeons should be able conduct their work efficiently and prevent waste of their precious time (Chartered Management Institute 2000). The importance of efficiently managing activities in the OR has generally been well recognized. Atkinson and Kohn (1986) propose the use of time records of activities to determine efficiency and to identify the quickest and easiest ways of doing things. As Atkinson and Kohn (1986, p. 190) comment: Time is an important element in the OR. If time is wasted between operations, for example, the day‘s schedule is slowed down and later operations are delayed. The surgeons ‘time is wasted and they tend to late, anticipating delays. The patients become more nervous waiting for their operations and more un comfortable during the prolonged period without fluids. Leedal and Smith (2005) analysed the components of anaesthetists ‘operating room activities, and the factors contributing to workload, using an ergonomic-based model for technological environments. Den Boer et al. (1999) applied standardised time-motion analysis to evaluate the preoperative surgical process which provided detailed insight into the preoperative process of the surgery, thus leading to improvements in the surgical process and instruments used. Recently, Wallace & Savitz (2008) chose time-and-motion methods to allow a description of low-frequency events and problems encountered in the US health care system. Inside the OR, a body of knowledge commonly referred to as principles of motion economy has been in use for many years (Atkinson, 1992). Motion economy principles embody three categories of principles: body movement, arrangement of work places and design of tooling and equipment. As the first two categories are relevant for the present study, 16 principles of time and motion study in the first two categories are discussed next. The first nine of these principles concern the use of the human body, whereas the remaining seven principles relate to arrangement of the workplace. 1. The two hands should begin as well as complete their motions at the same time. 2. The two hands should not be idle at the same time except during rest periods. 3. Motions of the arms should be made in opposite and symmetrical directions and should be made simultaneously. The first three principles are related because they all relate to movement of hands (Barnes 1980). There is a natural tendency for most people to use their preferred hand (either right hand or left hand) to accomplish most of the work and to relegate the other hand to a minor role, such as holding the 20


object while the preferred hand works on it. The first principle states that both hands should be used as equally as possible, thus it would be necessary to design work methods such that the work is evenly divided between the two hands. The work method should be designed to avoid periods when neither hand is working. It may not be possible to completely balance the workload between the right and left hands, but it should be possible to avoid having both hands idle at the same time. When possible, symmetric and simultaneous motion minimizes the amount of hand-eye coordination required by the worker. And since both hands are doing the same movements at the same time, less concentration will be required than if the two hands had to perform different and independent motions. The need for economy of effort in an operating theatre and reducing fatigue in an operating room setting has been widely recognized (Burguer 2008). When interpreted from the point of view of an operating room, the scrub nurse, for example, when she is using her left hand to pass the tool to surgeon, can use the other hand at the same time to collect the tool that is no longer used by surgeon. The tools or instrument should be divided in two sides: one for the tools that are going to be used, and another side for the tools that are going to be collected. It is better to use both hands equally in order to improve the performance and allow smoother coordination with the surgeon. In addition, the preferred hand is faster, stronger, and more practical. If the work to be done cannot be allocated evenly between the two hands, then the method should take advantage of the worker‘s best hand. For the surgeon, for example, the patient should be positioned on the side of the surgeon‘s preferred hand. The reason is that greater hand-eye coordination is required to initially access the patient; so the surgeon should use the preferred hand for this element (Philips 2004). Regarding the second principle, the exception within the operating room is during the actual operation by the surgeon, when the rest of the staff are in a monitoring role and are using their cognitive senses rather than their hands. The scrub nurse, in her role of assisting the surgeon should, for instance, be able to notice the ongoing requirement from the surgeon in order to avoid the surgeon having both hands idle during the surgery (Philips 2004). 4. Hand and body motions should be confined to the lowest classification with which it is possible to perform the work satisfactorily. Short motions are more effective than lengthy ones. There are five classes of hand motion (Barnes 1980, p. 186), namely: 1. Finger motions. 2. Motions involving fingers and forearms. 3. Motions involving fingers, wrist, and forearm. 4. Motions involving fingers, wrist, forearm, and upper arm. 21


5. Motions involving fingers, wrist, forearm, upper arm, and shoulder. The motion first listed above requires the least time and effort. Thus, the work should be designed such that tools are near their point of use to enable short motions (Barnes 1980). The principle is applicable in a healthcare setting in that it helps reduce fatigue and, thus, enhances efficiency (Burguer 2008). 5. Momentum should be employed to assist the worker wherever possible, and it should be reduced to a minimum if it must be overcome by muscular effort Momentum, which can be defined as mass multiplied by velocity, assists easy movement of motion; if used appropriately. For the most part, in work that involves moving an object, the total weight moved by an operator includes the weight of the material moved and the weight of the part of the body moved. When the object to be moved is on the right momentum, it is advantageous to utilize it to move the object to the right target. When the momentum needs to be stopped, it takes some effort from the muscle of the operator to stop it. Thus the work should be designed such that the movement of objects enables the use of momentum and avoidance of unnecessary momentum (Barnes 1980). Not all work situations provide an opportunity to use momentum. Yet, as the general necessity to minimize physical stress in operating room activities is well recognized (Burguer 2008), the importance of this principle in OR, whenever possible, is evident. 6. Smooth continuous curved motions of the hands are preferable to straight line motions involving sudden and sharp changes in direction. It takes less time to move through a sequence of smooth continuous curved paths than through a sequence of straight paths that are opposite in direction, even though the actual total distance of the curved paths may be longer, i.e. although the shortest distance between two points is a straight line. The reason behind this principle is that the straight-line path sequence includes start and stop actions that consume the operator‘s time and energy (Barnes 1980). This principle could apply to a surgeon‘s hand motion and could be implemented to make the activities of the surgeon more efficient (Burguer 2008). 7. Ballistic movements are faster, easier and more accurate than restricted (fixation) or controlled movements. Ballistic movements (e.g. akin to when a carpenter swings a hammer in driving a nail) rather than fixation movements should be used whenever possible. Ballistic movements are less fatiguing, faster, and more effective. In ballistic movements, the body muscle contracts only at the beginning and will relax afterwards (Barnes 1980). In a similar way to the above principle, this principle could apply to surgeons‘and nurses‘movement of tools to make activities more efficient (Burguer 2008). 22


8. Work should be arranged to permit an easy and natural rhythm wherever possible. Rhythm refers to regular sequence of similar motions. Basically, the worker learns the rhythm and performs the motions without thinking, much like the natural and instinctive motion pattern that occurs in walking. Whenever possible, the work should be designed such that rhythmic motion should be applied (Barnes 1980). The importance of proper work design in operating rooms enhances efficiency of operations and reduces mental and physical stress (Burguer 2008). The principle is especially relevant for nurses and wards men who perform repeat tasks. 9. Eye fixations should be as few and as close together as possible. Where hand-eye coordination is required in a work situation, the eyes are used to direct the actions of the hands. Since eye focus and eye travel each take time, it is desirable to minimize, as much as possible, the need for the worker to make these adjustments. Eye travel occurs when the eye must adjust to a line-of-sight change—for example, from one location in the workplace to another, but the distances from the eyes are the same. Since eye focus and eye travel each take time, it is desirable to minimize, as much as possible, the need for the worker to make these adjustments. For example, in a health care setting, this can be accomplished by minimizing the distances between objects (e.g., patient and instruments) that are used in the operating room (Barnes 1980; Burguer 2008; Leedal & Smith 2005). 10. There should be a definite and fixed place for all tools and materials. The worker will be more efficient when there is a defined place for materials and equipment. Definite stations for materials and tools enable the worker to develop a habit that helps rapid development of automaticity. If the workplace is arranged as such, the worker can perform the tasks with little conscious mental effort (Barnes 1980). Burguer (2008) indicates that efficient design and set up of operating rooms has long been a subject of interest to surgeons and that the optimum design characteristics and the design of standards have been widely discussed. As the saying goes, ―a place for everything and everything in its placeǁ is essential in an operating room environment. For example, if sharp instruments and used sponges are scattered randomly around the anatomy area of surgery, it would reduce efficiency and increase risks. This principle could be used to design a fixed location, allowing surgery and scrub nurses to reach for the instruments without wasting time by looking and searching. 11. Tools, materials, and controls should be located close in and directly in front of the operator. Locating tools, materials, and controls close to and directly in front of the operator helps to minimize the distances the worker must move (travel empty and travel loaded) in the workplace. In addition, any equipment controls should also be located in close proximity. It is generally desirable to keep the parts and tools used in the work method within the normal working area, as defined for 23


each hand and both hands working together (Barnes 1980). Arrangement of surgery instruments within the grasp of the surgeon is a typical application of this principle (Burguer 2008). The change of a surgeon‘s body position is not only time consuming, but also raises the risk to the patient. If the method requires the scrub nurse to move beyond the maximum working area, then the worker must move more than just the arms and hands. This expends additional energy, takes more time, and ultimately contributes to greater worker fatigue. 12. Gravity feed bins and containers should be used whenever possible. Bins with sloping bottoms enable the item to be fed into the front with the help of gravity. A gravity fed bin is a container that uses gravity to move the items in it to a convenient access point for the worker (Barnes 1980). Designing equipment in operating rooms in a way that reduces physical stress could greatly enhance efficiency (Burguer 2008). 13. Use gravity drop chutes (channels, tubes) for completed work units where appropriate The drop chutes should lead to a container adjacent to the worktable. The entrance to the gravity chute should be located near the normal work area, permitting the worker to dispose of the finished work unit quickly and conveniently. They are most appropriate for lightweight work units that are not fragile (Barnes 1980). Similar to the preceding principle, this principle enables minimization of physical stress which, in turn, is expected to substantially improve efficiency (Burguer 2008). 14. Materials and tools should be located to permit the best sequence of motions. Items should be arranged in a logical order that matches the pattern of work elements. The items that are used first in the cycle should be on one side of the work area; the items used next should be next to the one that precedes it; and so on. If items are located randomly in the work area, that increases the amount of searching required and detracts from the rhythm of the work cycle (Barnes 1980). The need for proper arrangement and organization of tools and material in operating rooms for enhanced efficiency of operations has long been recognized (Burguer 2008). 15. Provide for adequate visual perception. Good illumination is the first requirement. Proper illumination assists adequate perception, thus, light of the right intensity and colour, and that is without glare, should come from the right direction to the work area (Barnes 1980). In an operating room, for example, proper positioning of the patient and the application of mechanical retractors to the anatomy area greatly enhances efficiency (Burguer 2008). 16. Arrange the height of the workplace and chair for alternate sitting and Standing, when possible. This usually means an adjustable chair that can be fitted to the size of the worker .The adjustments usually include seat height and back height. Both the seat and back are padded. Many adjustable chairs also provide a means of increasing and decreasing the amount of back support. The chair

24


height should be in proper relationship with the work height (Barnes 1980). This principle is highly applicable in an OR setting as there is a need to have a surgeon‘s chair that is adjustable in size. Gong, Xiao Yan

; Identifying and Minimising Preventable Delay within the Operating Theatre

Management, 2009 a dissertation 3.2 General motors Uses a Pegboard Device to Illustrate Principles of Motion Study Presents Case For Motion Study In Particular & Shows How Skeptics Can Be Convinced That Motion Study Is A Good Thing. It was not a friendly time at General Motors after a 113-day strike in the winter of 1945-46. The United Auto Workers (UAW) had been recognized by GM just four and a half years before the start of World War II, and wartime controls had regulated wage and price increases. Embryonic before being interrupted by war, the relationship between labour and management was young and poorly developed, and management was used to having its way, accustomed to telling workers what to do and how to do it. The Easier Way, which GM commissioned in 1946, expresses this attitude, selling efficiency as a boon for the worker rather than a means of maximizing profits. The Easier Way was designed to convince line management (many of whom had risen from the ranks) that time and motion study was a good thing for industrial workers. Bob (a motion study expert) and Marge invite Dick Gardner, an assembly-line foreman and his wife over for dinner. The two men start talking about motion study. Bob asserts that "a man can produce more without working a bit harder." Dick has risen from the ranks and is suspicious of all this time and motion study stuff, feeling that it's just designed to wring more work out of people. Bob tries to disabuse him of this idea, saying, "Now we're able to produce more and more stuff with less and less effort on the part of the guys who do the work. That's what motion study's for. We point out how the machines and tools and the methods of using them should be changed to make it easier for the operator." Dick is still suspicious: "It's gonna be hard to make some of the boys understand that." Bob answers, "It'll take time. But first, I've gotta sell men like you." Bob, Marge and the Gardners play with a pegboard and practice different ways of inserting the pegs into the holes. This hands-on demo convinces Dick of the righteousness of Bob's views: "The boys will listen to stuff that makes sense. Especially if it makes it easier for us to get production." Like a grown-up Alexander Phipps, Bob tries to infiltrate motion study into the domestic routine. "Now take this simple job of setting the table. Women do it the hard way." "Now Bob," says Marge, "you can't run a house like a factory." Bob responds: "Why not? Think of the effort you'd save.

25


Maybe you wouldn't be so tired at the end of the day." As Marge sets the table, Bob sneaks a look at his timepiece. As the film ends, she ties an apron around Bob and makes him do the dishes. In The Easier Way, we see company management drawing a line between issues subject to bargaining and others that it considers non-negotiable. GM is asserting here that the work process Ñ its technology, design and management Ñ is its own to plan and control, no matter how much influence unions exert in its plants. In fact, productivity increases were a major agenda item for General Motors at the time. In 1948, GM chairman Alfred P. Sloan, Jr. and president Charles E. Wilson proposed that the new GM-UAW contract link wage increases to increases in worker productivity, with adjustments for the cost of living. This clause was adopted in 1948 and was part of labor agreements for over twenty years. The business community praised the linkage between productivity and wages, and General Motors "got its production."

http://archive.org/details/EasierWa1946 http://www.processsolutions.net/bins.html

3.3 Experiment on motion study Materials 40 page papers (i.e. four different pages (1, 2, 3&4) each 10 copies) Stapler Stopwatch (electronic)

Procedure 1. Lay each page item on the table. (Different alternatives going to be evaluated) 1

2

3

4

2. Click the Start button of the stopwatch. 3. Pick from each page and staple as (page 1upper next 2, 3&4) in the figure below. 26

Application of motion economy Principles 2

1

3

4

4. Put the stapled paper on a given specific place. 5. When you complete press stop button of the stopwatch. 6. Record the time taken. 7. Compare different alternatives Alternative tests & results 1. Lay out first 1

2

Time taken 3

4

01:34:07(pick 1 page at a time& put on the floor) 01:05.50(pick 1 page at a time & put on the table)

Operator

2. Lay out second

Time taken 01:22.25(pick 1 page at a time & put on the floor)

4

3

2

1

01:05.70(pick 1 page at a time & put on the table)

Operator

3. Lay out Third

Time taken 01:32:44(pick 1 page at a time & put on the floor)

2

3

1

00:58.20(pick 1 page at a time & put on the table) 4

Operator

4. Lay out fourth 3

Time taken 01:00.20(pick 1 page at a time & put on the floor)

2

01:00.20(pick 1 page at a time & put on the table) 4

1 Operator 27


5. Lay out fifth 3

Time taken 00:47.60(pick 2 pages at a time & put on the floor)

4

1

00:47.60 (pick 2 pages at a time & put on the table)

2

Operator

6. Lay out sixth

Time taken

4

00:54.20(pick 2 pages at a time & put on the floor)

3

2

00:54.20(pick 2 pages at a time & put on the table) 1

Operator

7. Lay out seventh 1


2

01:00.80(pick 2 pages at a time & put on the table)

3

4 Operator

8. Lay out eighth


2

1

4

01:00.40(pick 2 pages at a time & put on the table) 3

Operator

28


Results Table 2 experiment results for different orientations Layout

Exp 1

Exp 2

Exp 3

Exp 4

Exp 5

Average

1

01:05.70

01:05.42

01:06.73

01:03.00

01:06.83

01:05.50

2

01:10.85

01:06.40

01:03.64

01:06.03

01:01.77

01:05.70

3

00:57.47

01:00.04

00:59.43

01:00.37

00:53.82

00:58.20

4

01:02.43

01:03.30

01:00.32

00:56.16

00:58.96

01:00.20

5

00:54.85

00:46.52

00:45.58

00:48.01

00:42.82

00:47.60

6

00:54.85

00:57.51

00:54.24

00:49.88

00:54.42

00:54.20

7

01:03.04

00:59.10

00:58.59

01:04.35

00:59.15

01:00.80

8

01:01.17

01:01.82

00:57.65

01:01.49

00:59.81

01:00.40

Discussion 1. Lay out one is done by picking one page at a time from left to right (1, 2, 3&4) and putting on the floor on the right side. The time taken to staple 40 pages of 4 different items is 01:34.07(1 minute, 34 seconds & 7 microseconds). But when two pages are picked at a time the average time taken is dropped to 01:05.50.When two pages are picked at a time and placed on the key board (drop delivery); the time required to staple will be 01:01.18. 2. Lay out two is done by picking one page at a time from right to left (1, 2, 3&4) and putting on the floor on the right side. The time taken to staple 40 pages of 4 different items is 01:22.25 (1 minute, 22 seconds & 25 microseconds).When the stapled paper is dropped on the key board & two pages are picked at a time the time taken is dropped to 01:04.00.

3.4 Limitations of Motion Economy Motion economy has limitations. It does not account for physical limitations or differences in operators. Moreover, a movement that appears ineffective from a motion economy perspective actually may prevent fatigue and possible injury from static posture loading. However, using them alongside Principles of Ergonomics and a rationalized design procedure will ensure a productive, safe and optimum workstation.

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REFERENCES [1] T.R. Banga S.C.Sharma, Industrial Organization and Engineering Economics Twenty-Third Edition, KHANNA PUBLISHERS, Delhi [2] Barnes, Ralph M., Motion and Time Study, Second Edition, John Wiley & Sons, New York, 1940. [3] www.strategosinc.com/motion_economy.htm [4] www.doms.iitm.ac.in/documents/rahul/layout&economy [5] Gong, Xiao Yan ; Identifying and Minimising Preventable Delay within the Operating Theatre Management, 2009 a dissertation [6] http://www.processsolutions.net/bins.html [7] J.P. Watson and D.N. Wise, “Motion-Economy-Device Design”, in Industrial Engineering Handbook, Second Edition, H.B. Maynard (Editor-in-Chief), McGraw-Hill, pp. 2-87 to 2-103. [8] General motor’s story real video site; http://archive.org/details/EasierWa1946 [9] http://www.processsolutions.net/bins.html

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Index Key definitions Operating theatre management process (OTMP): a complicated healthcare-delivery process which starts from the referral of a patient to a hospital that ends with the patient‘s discharge from the hospital after surgery has been performed. Operating Theatre Suit: part of OTMP that comprises all areas related directly to the surgical procedures from pre-operative function to recovery area. Pre-operative holding area is designed to accommodate the admission of patients before entering the OR. Anaesthetic bay is the area within the OR where the patient is assessed and prepared for anaesthesia. Recovery area is situated near the entrance of the operating theatre suit. There are eight bays commissioned within the unit.

The post-operative patient is closely monitored until they are

physiologically stable. Sterile stock room is centrally located in the operating theatre suit; reusable and disposable sterile supplies are stored in this area. Surgeon’s preference sheets:

the surgeon‘s specific preferences and any variance from the

procedures in the procedure book are noted on these sheets. The sheets are revised as procedures and personal preferences for new technology change. Consent form: the form requires patient‘s consent on patient‘s condition and procedure, surgery and treatment plan. It also includes statements about risks and complications. Anatomy area: the area when the incision takes place. Mayo table:

The table used in a sterilised area to lay down frequently used instruments and other

materials during the surgery. Patient positioning: the position of the patient during the surgery. Surgeon: physician who performs the surgical procedure. Assistant surgeon: member of sterile team who provides exposure and hemostasis during a surgical procedure. Anaesthetist: member of the non-sterile team who administers anaesthetics during the surgical procedure. Scrub nurse: member of the sterile team who passes instruments and facilitates the surgical procedure. Scout nurse: member of the non-sterile team who directs and coordinates the activities of the intraoperative environment during the surgical procedure. 31


Motion-Economy Device Design - Important Devices These devices improve the efficiency of manual operations. Important Motion-Economy Devices Watson and Wise, industrial engineers of Mine Safety Appliances Company mentioned the following as worthy of mention in a list of important motion-economy devices. Stops A stop is a device for locating material at some predetermined position so that work can be performed while it is so located. Quick-acting Clamps These clams provide an efficient method of holding parts in positions for a wide variety of operations. Ball-joint or Swivel Fixtures This has a work table attached to a ball joint. In many assembly operations, work needs to be performed on the sub assemblies and main assembly at various angles and positions. A swivel or ball-joint may be used by the fitter or assembler to mount the assembly on it and enable the operator turn the fixture at will at any position at any time and use his both hands for working. Hinged Fixtures This fixture allows the operator to work one side of the part for some time and then turn over the part using the hinge and then work on the other side. Air-Cylinder Devices Air cylinders are used in machining, forming, and assembly operations. They are available in a wide range of sizes and types, and engineers can use them ingeniously for many applications. Air cylinders are also used instead of arbor presses, foot presses, or bench-type punch presses for performing a wide variety of operations such holding, swaging, upsetting, riveting, and forming. Rotary-Assembly Fixtures In these fixtures there is a rotating table on which number of work pieces are mounted and each turn of the table brings a work piece to the operator. The operator completes his job and turns the table so that the next work piece comes to him. Another helper can now remove the finished work piece and load a new job. Hopper and Motion-Economy Bins A hopper is a storage device for either raw material or a component of an assembly, so designed that it delivers the material t be used at a selected point within the normal grasp area of the operator. Chutes and Other Drop Delivery Methods

32


Chutes and drop delivery methods facilitate deliver of the finished work piece to the next conveyor belt or a storage bin. Removable Table Tops They provide specially fitted assembly table tops for two or three different assemblies that an operator may be working in a day. They can be removed and kept in a rack and the different top can be put on the work bench. Foot Pedals The use of foot-operated mechanisms provides an economical method of holding, releasing, or assembling in various types of operations.

33

Applications of Principles of Motion Economy

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