Predetermined Time Systems

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Predetermined Time Systems

• INSY 3021
• Auburn University
• Spring 2007

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History

• Fredrick Taylor
• Time Study
• Frank and Lillian Gilbreth
• Motion Studies
• Predetermined Time Systems (PDTS)
• Combination of time and motion studies

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Therbligs!

• Work can be described by these 17.
• Effective/Productive Reach, Move, Grasp,
  Release, Pre-Position, Use, Assemble
  Disassemble.
• Ineffective/Non-Productive Search, Select,
  Position, Inspect, Plan, Unavoidable Delay,
  Avoidable Delay, Hold, Rest to overcome fatigue.

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Uses

• To predict standard times for new or modified
  jobs
• Used to improve method analysis
• Can identify ergonomic risk factors and risk of
  repetitive strain indices (RSI)

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Composition

• Sets of motion-time tables with rules and
  instructions
• Specialized training is essential to the
  practical application of these techniques
• Times are at 100 - which eliminates performance
  rating
• May be slight variability among different people
  using the same tool

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Types of Systems

• Acceleration-deceleration Systems
• Different body motions move at different
  velocities
• 40 of total time is used during acceleration,
  20 for constant velocity, and 40 for
  deceleration
• Not widely used today
• Very important in fields of Biomechanics and
  Kinematics
• Average-motion Systems
• Represents average motion difficulties for
  industrial operations
• Additive Systems
• Basic time values are used with a correction
  factor for difficult motions

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Methods-Time Measurement (MTM)

• A procedure that analyses manual operations or
  methods into basic motions needed to perform it,
  and assigns each a pre-determined time based on
  the motion and environmental conditions

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MTM-1

• Fundamental Motions
• Reach, turn, position, release, move, grasp,
  disengage
• Procedure
• Summarize all right-hand and left-hand motions
• Determine time measurement unit (TMU)
• Remove non-limiting motion values

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Time Measurement Units (TMU)

• 1 TMU 0.00001 hour
• 1 TMU 0.0006 min
• 1 TMU 0.036 sec
• 1 hour 100,000 TMU
• 1 min 1667 TMU
• 1 sec 27.8 TMU

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Maynard Operation Sequence Technique (MOST)

• Developed in 1980 by Zjell Zandin
• Establishes standards at least 5 times faster
  than MTM-1, w/little if any sacrifice in accuracy
• Concentrates on the movements of objects

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MOST Procedure

• Watch job/task
• Determine sequence(s) to use
• Determine index values
• Add index values to determine TMU
• Multiply TMU by 10
• Convert TMU to seconds, minutes, hours

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Concept of MOST

• Definition of work
• Work is the displacement of a mass or object
• Work Force X Distance

f 10 lbs. d 4 in.
f 10 lbs. d 0 in.
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Concept of MOST

• In Work, an object is moved
• GET and PUT
• For example, you can lift a box and place it down
  three feet away.
• Basic body motions used to perform work occur in
  repeating patterns or sequences.
• This is the foundation of BasicMOST and the
  sequence models that make up MOST.

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Concept of MOST
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Concept of MOST

• Method Description
• Documents the action performed
• Clear, concise and easily understood
• Comprised of recommended words
• Example
• Grasp marker located three steps away on the
  floor and put in holder.

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Sequence Models

• Sequence models represent the sequence of events
  that occurs when an object is moved or a tool is
  used.
• Predefined sequence models represent different
  types of activities.
• Three sequence models can be used to analyze all
  types of manual work
• General Move (moved freely through space)
• Controlled Move (movement restricted attached or
  in contact)
• Tool Use (using common hand tools)

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Phases

• Sequence models are structured into phases used
  to describe the action performed.
• Each of the predefined sequence models has a
  different set of phases.
• From Method Description Example
• Grasp marker located three steps away on the
  floor and put in holder.

Phase Get Put
Return
How did I GET the marker?
How did I PUT the marker?
Did I RETURN?
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Index Values
A B G A B P A
6 6 1 6 0 1 0
Get Put Return

• Each parameter is assigned an index value based
  on the motion needed to perform the activity.
• Index values are then used to generate the total
  time required to perform a task.

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How is Work Measurement Done?

• Method Description from video
• Grasp heavy box located within reach, walk eight
  steps, position on pallet and return to initial
  location.

A B G A B P A
1 0 3 10 0 6 10
Get Put Return
300 TMU x .036 sec/TMU 10.8 seconds
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How is Work Measurement Done?
TMU 300 250 330
A B G A B P A
1 0 3 10 0 6 10
Top Row
Get Put Return
A B G A B P A
1 0 3 10 0 1 10
Middle Row
Get Put Return
A B G A B P A
1 0 3 10 6 3 10
Bottom Row
Get Put Return
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Sources of error variance

• Hard to classify some motions
• Difference in opinion between team members
• Variation in distance measurements
• Repeatability and variation of worker
• Very time-consuming to break up job
• Repetitive to enter in data
• May not match actual times

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Pros Cons

• Advantages
• Efficiently estimates the time to perform a task
• Accurate results
• Methods are easily understood
• Sequence models result in minimal paperwork
• Encourages method development and continuous
  improvement

• Disadvantages
• Requires exact job description and layout
• Chance of omitting elements when estimating new
  jobs
• Not always applicable to non-repetitive operations

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Basic Sequence Models

• General Move
• The spatial movement of an object freely through
  the air
• Controlled Move
• The movement of an object when it either remains
  in contact with a surface or remains attached to
  another object during movement
• Tool Use

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Basic Sequence Models
Activity Sequence Model Parameter
General Move ABG ABP A A action distance B body motion G gain control P placement
Controlled Move ABG MXI A M move controlled X process time I alignment
Tool Use ABG ABP ABP A F/L fasten/loosen C cut S surface treat M measure R record T think
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General Move

• Parameters
• Action Distance (A) horizontal distance
• Body Motion (B) vertical distance
• Gain Control (G)
• Placement (P)
• ABG ABP A
• Get Put Return
• Assign an index value based on complexity
• Accounts for 50-60 of most industrial work

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General Move
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MOST (PTS)

• When determining the normal time that it takes to
  obtain an object, Action Distance is accounted
  for in the calculation

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MOST (PTS)

• As you can see, Body Movement is taken into
  account for the calculation

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Controlled Move

• Parameters
• Action Distance (A) horizontal distance
• Body Motion (B) vertical distance
• Gain Control (G)
• Move Controlled (M)
• Process Time (X) machine time
• Alignment (I)
• ABG MXI A
• Get Move or Actuate Return

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Tool Use

• Parameters
• Fasten (F)
• Loosen (L)
• Cut (C)
• Surface Treat (S)
• Measure (M)
• Record (R)
• Think (T)
• ABG ABP ABP A
• Get Put Tool Action Put Return

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Examples

• Example Get a handful of washers and put them
  onto 3 bolts located 5 inches apart.
• A1 B0 G3 (A1 B0 P1) A0 (3) 100 TMU
• Example A worker slides a ruler within reach and
  pushes it 6 inches (15 cm) to measure two points
  that are 8 inches apart.
• A1 B0 G1 M1 X0 I6 A0 90 TMU
• Example Grasp wrench and fasten bolt with 3
  wrist strokes and aside.
• A1 B0 G1 A1 B0 P3 F10 A1 B0 P1 A0 180 TMU

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Other MOST Systems

• MiniMOST
• MaxiMOST
• AdminMOST
• MOST Work Measurement Systems Third Edition,
  Revised and Expanded, Kjell B. Zandin

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Special Issues

• Work Factors ? For instance, allows the
  incorporation of stairs gates into PDTS models.

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Questions Comments