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Chapter 26
Predetermined
Time Systems
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Methods To Set Time
Standards
Estimation
Estimated times
Historical
records
Historical times
Methods to
set time
standards
Work
measurement
techniques
Direct time
studies
Pre-determined
time systems
Engineered
standards
Standard data
systems
Work sampling
Proportions of
work activities
Predetermined
Time Systems
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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
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Developed in 1946
Simplified versions are available.
A training course is required for using the
system correctly.
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MTM-1
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10 categories of movements
Times in TMUs (Time Measurement Units)
1 TMU = 0.000 010 h
= 0.000 600 min
= 0.036 s
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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.
B.
C.
D.
E.
Reach to an object in a fixed location or in the other hand.
Reach to a single object whose general location is known.
Reach to an object jumbled with others in a group (requires search &
select).
Reach to a very small object or where accurate grasp is required
(visual control).
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.
B.
C.
Move object to the other hand or against stop (little control).
Move object to an approximate or indefinite location (some control).
Move object to an exact location (control).
Parameterized by
distance
object weight
Variation: Crank
parameterized by diameter
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Turn
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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
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Application of force without resultant
movement.
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Grasp
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Pickup grasp
Regrasp
Transfer grasp
Jumbled grasp
Contact, sliding, or hook grasp
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Position
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Aligning, orienting, or engaging one object with
another
Position times vary with:
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Amount of pressure needed to fit
Symmetry of the object
Ease of handling
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Disengage
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Breaking contact between one object and
another
Times vary with:
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Class of fit
Ease of handling
Care in handling
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Release
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Relinquishing control of an object by the hand
or fingers
Two types:
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Simple opening of the fingers
Contact release
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Other Motions
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Body, leg, and foot motions
Eye motions
Combined motions
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e.g., Regrasp during Move
time is greater of two times
Limited motions
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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
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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
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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
MOST Work
Measurement System
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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.
General Move
Sequence Model
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MODAPTS
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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
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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.