Principles of Motion Economy and Work Design

Assist. Prof.Dr. ule SELUKSelman Kaymaz

Work Analysis and Design (IE305)

Principles of Motion Economy and Work Design

Work design involves the methods and motions used to perform a task. Work design is the design of the work system.

Motion study Involves the analysis of the basic hand, arm, and body movements of workers as they perform work.

What does work design include?

the workplace layout and environmentthe tooling and equipment (e.g., work holders, fixtures, hand tools, portable power tools, and machine tools).

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I should catalog the basic motion elements and I should call them therbligs.

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Therbligs are the basic building blocks of virtually all manual work performed at a single workplace and consisting primarily of hand motions.Each therblig represents time and energy expended by a worker to perform a task.

17 Therbligs

1. Transport empty (TE) reach for an objectwith empty hand today we call it reach.2. Grasp (G) grasp an object by contactingand closing the fingers until control has beenachived.3. Transport loaded (TL) move an object withhand and arm today we call it move.4. Hold (H) hold an object with one hand.5. Release load (RL) release control of anObject.6. Use (U) manipulate/use a tool.

7. Pre- position (PP) position object for nextoperation8. Position (P) position object in definedlocation9. Assemble (A) join two parts10. Disassemble (DA) seperate multiple partsthat were previously joined11. Search (Sh) attempt to find an object using eyes or hand

17 TherbligsThats All, Guys 12. Select (St) choose among several objects in a group (hand- eye coordination is involved).13. Plan (Pn) decide on an action (a short pause or hesitation in the motions)14. Inspect (I) determine quality of object using the eyes.15. Unavoidable delay (UD) waiting due to factors beyond worker control.16. Avoidable delay (AD) worker waiting.17. Rest (R) resting to overcome fatigue.If the task is repetitive, of relatively short duration, and will be performed many times, it may be appropriate to analyze the therbligs that make up the work cycle as part of the work design process. The term micromotion analysis is sometimes used for this type of analysis.

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What are objectives of classification of Therbligs?

Principles of Motion Economy and work desIng

Can be organized into 3 catogories :1 . Principles related to the use of human body.2 . Principles related to workplace arrangement.3 . Principles related to the design of tooling and equipment.

Use of Human Body

The two hands should begin and end their motions at the same time.

Both hands should be fully utilized.Both hands should be used as equally as possible.

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 motions of the hands and arms should be symmetrical and simultaneous.

Minimize hand-eye coordination.If both hands are doing the same movements at the same time ;Less concentration will be required.

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The work should be designed to emphasize the workers preferred hand.

The preferred hand is faster,stronger and more dexterous.

For exp: Work units should enter the work place on the side of the workers preffered hand.

The workers two hands should never be idle at the same time.

Method should consist of smooth continuous curved motions rather than straight motions with sudden changes in direction.

Use momentum to facilitate task.

Using of momentum to make a task easier.

The method should take advantage of gravity ,instead of opposing it !

Less time and energy are required to move a heavy object from a higher elevation to a lower elevation than to move the object upward.

Method should achieve a natural rhythm of the motions involved.Basically, the worker learns the rhythm and performs the motions without thinking, much like the natural and instinctive motion pattern that occurs in walking.

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The lowest classification of hand and arm motions should be used.There are five classification.The worker can perform the hand and arm motion more quickly and with less affort.

The lowest classification of hand and armI Movement of the fingers only.

II Fingers and wrist motion.

III Fingers, wrist, and forearm

IV Finger,wrist ,forearm,upper arm and shoulder

Minimize eye focus and eye travel activities.Eye focus occors when the eye must adjust to change in viewing distance.Eye travel occors when the eye must adjust to a line-of-sight change.Since eye focus and eye travel each take time, it is desirable to minimize the need for the worker to make these adjustments as much as possible.

The method should be designed to utilize the workers feet and legs when appropriate.The legs are stronger than the arms.The feet are not as dextrous as the hands.

The work should be designed to take advantage of the greater strength of the legs. For example : Lifting tasks.

Workplace Arrangement1 . Tools and materials should be located in fixed positions within work area.The worker eventually learns the fixed locations, allowing him to reach for the object without wasting time looking and searching.A place for everything, and everyting in its place.

3. Locate tools and materials to be consistent with sequence of work elements in work cycle. Decrease the time required for searching.2. Tools and materials should be located close to where they are used.To minimize the distances to be covered.

Normal working area in the workplace.

Maximum working area in the workplace.

For working area dimensions of average male and female workers.Poor arrangement of parts and tools in workplace

Good arrangement of parts and tools in workplaceElements in relation to locations of hand tools and parts bins.

4 . Use gravity feed bins to deliver small parts and fasteners

A gravity feed bin is a container that uses gravity to move the items in it to a convenient access point for the worker. It generally allows for quicker acquisition of an item than a conventional rectangular tray shown in Figure (b).

One possible design is shown in Figure (a). 5 . Use gravity drop chutes for completed work units where appropriate.

The drop chutes should lead to a container adjacent to the worktable.

6 . Provide adequate illuminationThe 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.

Workplace Arrangement7 . A proper chair should be provided for the worker.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. The chair height should be in proper relationship with the work height. An adjustable chair for the workplace is shown in Figure .

Design of Tooling and Equipment1. Work-holding devices should be designed for the task.

A mechanical work-holder with a fast-acting clamp permits the work unit to be loaded quickly and frees both hands to work on the task productively.

2 . The Hands should be relieved of work elements that can performed by the feet.

Foot pedal controls can be provided instead of hand controls to operate certain types of equipment. Sewing machines are examples in which foot pedals are used as integral components in the operation of the equipment.

3 . Combine multiple functions into one tool where possible.

Many of common hand tooks and implements exhibit this principle.The head of a claw hammer is designed for both striking and pulling nails.All pencils are designed for both writing and erasing.Less time is usually required to reposition such a double-function tool than to put one tool down and pick another one up.

4.Multiple operations should be performed simultaneously rather than sequentially.

5 . Equipment controls should be designed for operator convenience and error avoidance.Equipment controls include dials, cranks, levers, switches, push buttons, and other devices that regulate the operation of the equipment. >>>All of the controls needed by the operator should be located within easy reach, so as to minimize the body motions required to access and activate them.

6. Hand tools and portable powered tools should be designed for operator comport and convenience.The location of the handle or grip relative to the working end of the tool should be designed for maximum operator safety, convenience, and effectiveness of the tool. If possible, the tool should accommodate both right-handed and left handed workers.

7 . Manual operations should be mechanized or automated wherever economically and technologically feasible.

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Work Systems and the Methods, Measurement, and Management of Work 2013 IUS Sarajevo

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REFERENCESWork Systems and the Methods, Measurement, and Management of WorkISBN 90+387=