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IE 327 Introduction to Work Design Dr. Andris Freivalds Class #7

IE 327 Introduction to Work Design Dr. Andris Freivalds Class #7. Ex. 4-1 Lifting Box into Car. 30 lb box from ground into trunk Twist 90 ° to pick up Ground level → V = 0 Min horizontal → H = 10 Trunk → H = 25, V = 25 One-shot lift, FM = 1 No cutouts, CM = 0.95.

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IE 327 Introduction to Work Design Dr. Andris Freivalds Class #7

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  1. IE 327 Introduction to Work Design Dr. Andris Freivalds Class #7 IE 327

  2. Ex. 4-1 Lifting Box into Car • 30 lb box from ground into trunk • Twist 90° to pick up • Ground level → V = 0 • Min horizontal → H = 10 • Trunk → H = 25, V = 25 • One-shot lift, FM = 1 • No cutouts, CM = 0.95 IE 327

  3. Ex. 4-1 Lifting Box into Car RWLor = 51(10/H)(1-.0075|V-30|)(.82+1.8/D)(1-.0032A)FMxCM RWLdest = 51(10/H)(1-.0075|V-30|)(.82+1.8/D)(1-.0032A)FMxCM IE 327

  4. IE 327

  5. COUPLING MULTIPLIER IE 327

  6. Effect of Multipliers - 1 IE 327

  7. Effect of Multipliers - 2 IE 327

  8. Effect of Multipliers - 3 Frequency Multiplier IE 327

  9. Lifting Interventions • Decrease H • Avoid twisting • Turntables • Extra step • Lift tables • Tilt tables • Hoists IE 327

  10. CTD and TOOL DESIGN • Cumulative trauma disorders (CTDs) • Work-related musculoskeletal injuries • Due to repeated microtrauma from • High force, high repetition • Extreme joint motions, lack of rest • AKA: repetitive motion injuries • Cost to industry • 15-20% of workers • Average of $30,000/case • OSHA effort ‘Ergonomics Standard’ IE 327

  11. HAND ANATOMY and CTDs • Carpal tunnel syn. • Tenosynovitis • Tendinitis • Trigger finger • White finger • Raynaud’s disease • Rotator cuff • Thoracic outlet syn. IE 327

  12. HAND/WRIST POSTURES • Maintain neutral wrist • Flexion/extension • Radial/ulnar deviation • ↓ grip strength 20-30% • Arms hang down • Abduction fatiguing • Overhead work is very bad IE 327

  13. TYPES OF GRIP Opt = 1.5 in Power > Lateral > Two pt 100 lbs > 29% > 15% IE 327

  14. CTD risk analysis • Similar to NIOSH • 4 factors • Frequency • Posture • Force • Misc • Index < 1 IE 327

  15. IE 327

  16. COMMENTS ON CRIMIPER IE 327

  17. TOOL DESIGN #1 • Grip span, opt = 2¾-3¼ in • F = ½-⅔ M strength • Handedness, ↓10% • Strength, 90% can • Avoid tissue compression • Handle length ≥ 4 in IE 327

  18. TOOL DESIGN #2 • Triggers→ trigger finger • Force < 2 lbs • Use 2-3 fingers (not 1) • < 10,000 motions/day • Use strongest finger • Thumb ~ 16 lbs • Middle ~ 88% • Index ~ 81% • Ring ~ 69% • Little ~ 44% IE 327

  19. TOOL DESIGN #3 • Handle – grip • Circular crossection (double frustum) • Wood, plastic - ↓ shock, ↓ conductivity, friction • Metal bad (unless covered with rubber) • Weight < 5 lbs • Gloves • Add 0.2-1 in to hand diameter • ↓ grip strength & dexterity 10-20% • Tradeoff: ↑safety vs. ↓ performance IE 327

  20. POWER TOOLS • Provide power • But vibration • But reaction torque • Automatic shutoff • High RPM, high power • Reaction bar • Use proper tool in proper orientation • In-line vs. pistol grip • Neutral wrist IE 327

  21. IE 327

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