CTDtool-ed - • F = ½ M strength ⅔ • Handedness ↓10...

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IE 327 1 IE 327 Introduction to Work Design Dr. Andris Freivalds Class #7
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IE 327 2 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’
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IE 327 3 HAND ANATOMY and CTDs Carpal tunnel syn. Tenosynovitis Tendinitis Trigger finger White finger Raynaud’s disease Rotator cuff Thoracic outlet syn.
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IE 327 4 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
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IE 327 5 TYPES OF GRIP Power > Lateral > Two pt 100 lbs > 29% > 15% Opt = 1.5 in
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IE 327 6 CTD risk analysis Similar to NIOSH 4 factors Frequency Posture Force Misc Index < 1
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IE 327 7
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IE 327 8 COMMENTS ON CRIMIPER
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IE 327 9 TOOL DESIGN #1 Grip span, opt = 2¾-3¼ in
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Unformatted text preview: • F = ½- M strength ⅔ • Handedness, ↓10% • Strength, 90% can • Avoid tissue compression • Handle length ≥ 4 in IE 327 10 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 11 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 12 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 13...
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