My Class

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IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 16
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IE 553 Engineering of Human Work Dr. Andris
Freivalds Class 16
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Predetermined Time Systems MTM-2

• PTS technique for obtaining a standard time
  (vs. time study, work sampling) via
• Analyze and subdivide a task into elemental
  motions (therbligs)
• Assign pre-set time values for these elements
• Summate times to obtain a standard time for whole
  task (no direct timing)

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History of PTS

• Based on Gilbreths therbligs
• Time added in for each therblig
• First Work Factor in 1930s
• Now over 200 PTS systems
• Focus on MTM based ones

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Methods Time Measurement (MTM)

• Maynard, Stegemerten, Schwab in 1940s
• Westinghouse jobs, broken down into elements,
  rated, timed
• Time Measurement Unit (TMU) 0.00001 hr 0.0006
  min 0.036 sec
• Main variations tradeoff of speed accuracy
  MTM-1, 2, 3
• Specialized variations for jobs MTM-C for
  clerical, MTM-V for machines, MTM-M for
  magnification

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Comparison of MTM-1,-2,-3
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Accuracy vs. Length of Cycle
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May Use MTM-2 When

• Cycle time gt 1,600 TMUs ( 1 min ? 5)
• Cycle is not highly repetitive
• No complex finger motions used
• Ex dealing a deck of 52 cards
• Time
• Repetitive
• Finger motions

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9 Elemental Motions

• GET (G) gain control of object
• Reach for an object
• Grasp object
• (eventually) Release object
• PUT (P) move object (when under control) to new
  location
• Move object to new location
• Position object to proper location

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Variations of GET PUT

• Case type of grasping or correcting motion,
  amount of control needed
• Distance reached
• Weight of object or resistance
• Type of PUT
• Insertion difficulty (one object into another)
• Surface alignment

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Cases for GET(G)
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Cases for PUT (P)
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Clearances (in.) for Insertion vs. Alignment PUT
PA PB PC
Insertion gt0.4 lt0.4 Tight fit
Alignment gt0.25 lt0.25 gt0.0625 lt0.0625
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Distance Code
Range (in) Code Classification
0-2 2 1-finger
2-6 6 2-wrist
6-12 12 3-forearm
12-18 18 4-arm
18-32 32 5-torso
gt32 ? step
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Weight Factor

• If significant weight moved, additional time is
  needed
• GET Weight (GW) 1 TMU for each 2 lbs up to 40
  lbs
• PUT Weight (PW) 1 TMU for each 10 lbs (above
  4 lbs) up to 40 lbs
• Values are per hand (20 lb box ? 5 TMU)
• Resistance Ffriction 0.4 N

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Other 7 Elemental Motions - 1

• Apply Pressure (A) 14 TMU
• Exert muscular force on object
• Without moving it (otherwise G or P)
• Ex push button
• Regrasp (R) 6 TMU
• Change position of object
• Without relinquishing control (otherwise G)
• Ex reorient tool

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Other 7 Elemental Motions - 2

• Eye Action (E) 7 TMU
• Recognize an object or
• Shift line of sight out of normal area of vision
• Dont overdue, G and P have already
• Crank (C) 15 TMU/rev
• Hand/fingers move in circular path gt ½ rev
• If lt ½ rev, use G and/or P
• May need GW to overcome stiction
• May need PW for sticky crank

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Other 7 Elemental Motions - 3

• Steps (S) 18 TMU/step
• Leg motion to move body,
• Distance gt 12
• Foot Motion (F) 9 TMU
• Short foot motion, to press pedal
• Distance lt 12
• Bend Arise (B) 61 TMU
• Vertical displacement of body
• Bend, stoop, kneel on one knee
• Kneel on both knees 2B

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MTM-2 Application

1. Use MTM Methods Analysis Chart
2. Summarize motions by hand (L R)
3. Add TMUs (no ratings needed)
4. Add allowances
5. Consider special cases

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Summary of MTM-2 Data
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Insertion vs. Alignment PUT
RH TMU
P
P

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Continuous vs. Intermittent Crank
Continuous C Continuous C Intermittent C Intermittent C
GB 18 18
GW 10 5
3C 45
3PW 10 3
Total 71
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1) Simultaneous Motion

• Simo difficult motions require more time
• Add a penalty

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Other Special Cases

• Principle of limiting motion
• For two different motions for each hand
• Use the longer time
• Principle of combined motion
• For two combined motion in one hand
• Use longer time
• R is included in C-type motions

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Examples
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Sources of Error

• Discreteness tabular data
• No interpolation
• Hopefully, this averages out
• Synthesis assumes correct process
• Need correct application - practice

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Ex U-bolt assembly