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Chapter 26

Predetermined Time Systems

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Methods To Set Time Standards

Methods to set time standards

Estimation

Historical records

Work measure-ment techniques

Direct time studies

Pre-determined time systems

Standard data systems

Work sampling

Engineered standards

Proportions of work activities

Estimated times

Historical times

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Predetermined Time Systems● Frank and Lillian Gilbreth broke work into therbligs

(elements).● The next step is to assign time values to the

elements.● Times for elements are added to obtain a total time.● Independence and additivity are assumed.● PTS are based on the concept that there are basic,

universal units of work with standard amounts of time.

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Methods-Time Measurements

● Developed in 1946● Simplified versions are available.● A training course is required for using the

system correctly.

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MTM-1

● 10 categories of movements● Times in TMUs (Time Measurement Units)

1 TMU = 0.000 010 h= 0.000 600 min= 0.036 s

● Times are for an experienced worker working at a normal pace.

● No allowances are included in the times.● Takes ~ 2,000 cycles to make MTM standard time.

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Reach

5 cases:A. Reach to an object in a fixed location or in the other hand.B. Reach to a single object whose general location is known.C. Reach to an object jumbled with others in a group (requires search &

select).D. Reach to a very small object or where accurate grasp is required

(visual control).E. Reach to an indefinite location (minimum mental control).

Parameterized by distance (inches) knuckle-to-knuckle

Must consider shoulder, body movement (body assist)acceleration, deceleration

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Move

Hand usually holding something.3 cases:

A. Move object to the other hand or against stop (little control).B. Move object to an approximate or indefinite location (some control).C. Move object to an exact location (control).

Parameterized bydistanceobject weight

Variation: Crankparameterized by diameter

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Turn

● A movement that rotates the hand, wrist, and forearm about the long axis of the forearm.

● Time depends on degrees of turn, weight of the object, and resistance against turn.

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Apply Pressure

● Application of force without resultant movement.

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Grasp

● Pickup grasp● Regrasp● Transfer grasp● Jumbled grasp● Contact, sliding, or hook grasp

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Position

● Aligning, orienting, or engaging one object with another

● Position times vary with:– Amount of pressure needed to fit– Symmetry of the object– Ease of handling

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Disengage

● Breaking contact between one object and another

● Times vary with:– Class of fit– Ease of handling– Care in handling

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Release

● Relinquishing control of an object by the hand or fingers

● Two types:– Simple opening of the fingers– Contact release

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Other Motions

● Body, leg, and foot motions● Eye motions● Combined motions

– e.g., Regrasp during Move– time is greater of two times

● Limited motions– accuracy required for one motion limits accuracy of

simultaneous motion– requires continuation of limited motion after limiting motion

is completed

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MTM Form

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MTM-2

● Takes about 40% of the time of MTM-1 to analyze a task.

● Has only 37 times in all.● Key categories are GET and PUT.● Provides decision trees to determine case.● User estimates distance and uses time from

table. ● Includes 7 other motions.

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MTM-2 Analysis

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MTM-2 Exercise

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MTM-3

● Takes about 15% of the time of MTM-1 to analyze a task.

● Has only 10 times.● Key categories are HANDLE and TRANSPORT.● Provides decision trees to determine case.● User estimates distance (< 6 in. or > 6 in.) and

uses time from table. ● Includes 2 other motions.

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MTM-3 Analysis

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MOST Work Measurement System● Based on observation that the majority of

activities are associated with a limited number of motion sequences.

● Significantly reduces time required to perform an analysis.

● 4 sequence models.

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General Move Sequence Model

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MODAPTS

● Based on the concept that the body member used is the key variable.

● All body movements are multiples of a MOD (1 MOD = .129 s).

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Comments about PTS

● In theory, PTS can accurately predict task times.● Evidence shows reality and theory don’t agree.● One problem is that analyst judgment is required.● Most managements are not concerned with a great

deal of accuracy.● Managements are concerned with cost of analysis.