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IE 553 Engineering of Human Work Dr. Andris Freivalds Class #16

IE 553 Engineering of Human Work Dr. Andris Freivalds Class #16. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #16. Predetermined Time Systems – MTM-2. PTS – technique for obtaining a standard time (vs. time study, work sampling) via:

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IE 553 Engineering of Human Work Dr. Andris Freivalds Class #16

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  1. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #16 IE 553

  2. IE 553 Engineering of Human Work Dr. Andris Freivalds Class #16 IE 553

  3. 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) IE 553

  4. History of PTS • Based on Gilbreths’ therbligs • Time added in for each therblig • First – Work Factor in 1930’s • Now over 200 PTS systems • Focus on MTM based ones IE 553

  5. 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 IE 553

  6. Comparison of MTM-1,-2,-3 IE 553

  7. Accuracy vs. Length of Cycle IE 553

  8. May Use MTM-2 When: • Cycle time > 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 = IE 553

  9. 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 IE 553

  10. 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 IE 553

  11. Cases for GET(G) IE 553

  12. Cases for PUT (P) IE 553

  13. Clearances (in.) for Insertion vs. Alignment PUT IE 553

  14. Distance Code * >32 → step IE 553

  15. 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 IE 553

  16. 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 IE 553

  17. Other 7 Elemental Motions - 2 • Eye Action (E) = 7 TMU • Recognize an object or • Shift line of sight out of normal area of vision • Don’t overdue, G and P have already • Crank (C) = 15 TMU/rev • Hand/fingers move in circular path > ½ rev • If < ½ rev, use G and/or P • May need GW to overcome stiction • May need PW for sticky crank IE 553

  18. Other 7 Elemental Motions - 3 • Steps (S) = 18 TMU/step • Leg motion to move body, • Distance > 12” • Foot Motion (F) = 9 TMU • Short foot motion, to press pedal • Distance < 12” • Bend & Arise (B) = 61 TMU • Vertical displacement of body • Bend, stoop, kneel on one knee • Kneel on both knees = 2B IE 553

  19. MTM-2 Application • Use MTM Methods Analysis Chart • Summarize motions by hand (L & R) • Add TMUs (no ratings needed) • Add allowances • Consider special cases IE 553

  20. Summary of MTM-2 Data IE 553

  21. Insertion vs. Alignment PUT IE 553

  22. Continuous vs. Intermittent Crank IE 553

  23. 1) Simultaneous Motion • Simo difficult motions require more time • Add a penalty IE 553

  24. 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 IE 553

  25. Examples IE 553

  26. Sources of Error • Discreteness – tabular data • No interpolation • Hopefully, this averages out • Synthesis assumes correct process • Need correct application - practice IE 553

  27. Ex: U-bolt assembly IE 553

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