Chapter 6: Value Engineering

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Ch-30 PREDETERMINED
TIME SYSTEMS
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Methods Analysis and Time
General Assumption in Industry Time/unit
cte MTM WF, levels of detail gives trade
off between analysis detail vs analysis time
Basic Concepts
MTM-1 Reach Methods for
Move, Turn, Grasp, Apply Time Measurement
Pressure, Position MTM-2 MTM-3 Work
Factor Basic Concepts, Associated Factors
Detailed Work,
Detailed Mento, Ready
Work, WOCOM
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Methods Analysis and Time
Frank Lilian Gilbreth broke work into 17
Micro-elements or Therbligs (see Table
30.1) Example They improved bricklaying by
300 a gt 2000 years practice
!! Technique for PTS Step 1) Determine an
Efficient Work Method Therbligs
breakdown work into elements Step 2) Determine
(assign) a Time/unit to each element How
Determine the total time for a Task. Time for
each element are totaled
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Methods Analysis and Time
Concept How would you build your own house?
Industry Each job is independent and
additive, Or, Each element does not affect what
happens before or after it Independence
Additivity. NOT true in general, and here is
where PTS comes in Idea Develop a System of
Universal Units of Work with Standard Units of
work with standard amounts of Time Methods
Time Measurements and Work Factor Methods Time
Measurement Most widely used PTS
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Methods Analysis and Time
Reference Karger, D. Bayha, F. Engineer
Work Measurement, 4th edition. New York, Ind.
Press 1987. MTM-1 Basic MTM MTM-2
Basic MTM 2 Simplified Systems MTM-3
Basic MTM MTM-1 Motions are broken into 10
categories Units Time Measurement Unit 1 TMU
1 sec 27.78 TMU 1 min 1,667 TMU
No Allowances 1 hr 100,000 TMU
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Methods Analysis and Time
Q M What is the learning Curve (see Ch-29) ?,
i.e., How many cycles of practice are
needed ? A Not clear yet 82, 74, 71,
108, etc REACH (see Table 30.2) Measured
with empty hand, or finger. Five Cases 1) Reach
Object in Fixed location, or to object in other
hand or on which other hand rests. 2) Reach
to single object in location, which may vary
slightly from cycle to cycle.
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Methods Analysis and Time
REACH (cont) 3) Reach to object that jumbled
with other objects in a group so that search
and select occur 4) Reach a very small object or
where accurate grasp is required. 5) Reach
to indefinite location to get hand in position
for body balance or next motion or out of way.
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Methods Analysis and Time
Distances Motion path of hand knuckle or finger
tip. Body assistance (shoulder
movement or pivoting) not
included. Interpolation is suggested R15A
ltR14AR15Agt Acceleration Deceleration Hands
could be in motion at the beginning and end of
the cycle. Then Acc. Decel. can be omitted.
Double this decrease is subtracted (Hand in
Motion Table 30.2) MOVE Hand is usually holding
something (or pushing and dragging an object.
Three cases are considered (nature of their
destination). See Table 30.3
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Methods Analysis and Time
Movements can be refined to consider the effect
of acceleration or Dec., or both. Also considered
as a refinement for Object weight resistance to
movement. MTM Both Moves and Reach are
influenced by motions preceding
or following them Nomenclature Accel. - Decel.
If omitted we use m mM6B or M6Bm Weight
Included up to 2.5 lb/hand If two
hand used, and object is 5lb, no extra
time is allocated.
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Methods Analysis and Time
Sliding Takes the Object Weight ? ?
(wood-wood wood-metal 0.4 metal-metal
0.3) Example M6B 8.9 a 5lb weight
object (T-30.3) M6B5 8.9 ? 1.06
2.2 11.8 Dynamic Factor
Static Constant Weight of Additional
Components To gain control
through dynamic component for extra Travel Time.
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Methods Analysis and Time
TURN (see Table 30.5) Considers the
rotation of the hand, wrist and forearm about
long axis of forearm Time
f(?,weight, resistance to ?) APPLY PRESSURE
(see Table 30.6) Is the application of force
without resultant move APA Basic element APB
APA Regrasp Grasp Position Skill
Motions Disengage Time Reducers Release
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Methods Analysis and Time
GRASP To gain Control of an object or Objects
(followed by a move). Considers 5 Types (see
Table 30.7) Type 1 Pick-up Grasp Follows an A
or B reach Type 2 Regrasp Performed during a
move limited-out Type 3 Transfer Grasp Control
from 1 hand to the other Type 4 Jumbled Grasp
Follows a C reach Type 5 Contact, sliding or
hook Grasp Between a Reach and a
Move. POSITION (see Table
30.8) Collection of minor hand movements (less
than 1 inch) for aligning, orienting, engaging 1
object with another.
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Methods Analysis and Time
Align Orient longitudinal axes of the two
items. Orient Rotation about long axis to align
mating features (key in a lock, for
example). Engaging Move along longitudinal axis
to mate the parts. Disengage
Complement of the engage portion position
Assumption Alignement Orientation are
already done
t 0 Position Times (see
Table 30.8) They are a function of Pressure to
Fit, Object Symmetry, Ease of Handling
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Methods Analysis and Time

• 3 Classes of Fit (see Table 30.8)
• Loose Gravity will do it, code 1
• Close Light pressure needed (1 APA), code 2
• Exact Heavy pressure needed (3APAG2), code3
• 3 Classes of Symmetry (see Table 30.8)
• Symmetrical (Code S) No matter the orientation
  no rotation is needed for assembly (peg in round
  hole)
• Non-Symmetrical (Code NS) There is one and
  only one orientation in which the parts will
  mate.
• Semisymmetrical Any position that is not S or NS
• (A turn of 45
  for example)