Rep. Mot. Inj. & Hand Tool Design

Question 1

What are some synonyms for Repetitive Motion Injury?

Answer 1

Cumulative Trauma Disorder
Overuse disorder
work-related disorder
‘motion injury’

Question 2

What are 4 basic causes of RMI’s?

Answer 2

1. Excessive Force
2. Awkward or extreme joint motion
3. High repetition
4. Duration of work

Question 3

Name some common RMI’s

Answer 3

Carpal Tunnel Syndrome
Cubital Tunnel Syndrome
Ganglion
Tendonitis
Thoracic Outlet Syndrome

Question 4

How can shoulder tendonitis occur?

Answer 4

When arms and shoulders are frequently raised

Question 5

What are the classifications of hand motions?

Answer 5

Flexion, Extension, Ulnar and Radial Deviation

Forearm rotation
palm down: pronation

palm up: supination

Question 6

Comment on other factors causing RMI

Answer 6

• It isnt instant.
• Direct cause often impossible to pinpoint
• Leisure activites (eg knitting, carpentry, tennis playing) can impact likelihood

Question 7

What are some design guidelines to avoid RMI?

Answer 7

Hand posture:

• Watch out for suden flexion, extension
• Avoid extreme ulnar or radial deviations
• Keep forces low during rotation or flexion

Handtools:

• Cylinder grips not exceeding 2in. diameter
• Avoid excessive finger spreading
• Keep work surface low to permit working with elbows and wrist in working position

Process Engineering:

• Allow machines to do repetitive tasks
• Provide jigs/fixtures that allow for convenient angles etc.

Question 8

What are some tenets of Hand Tool Design

Answer 8

A tool must:

• Fit the task
• Fit the user and hand
• Not create injury

Question 9

What are 3 types of power grips?

Answer 9

Force parallel to forearm eg. a saw

Force at angle to forearm eg hammer

Torque about the forearm eg. screwdriver

Question 10

What are two forms of precision grips

Answer 10

Internal-Tool inside hand

External- Tool pinched by thumb/index finger

Question 11

What is an opportunity for ergonomic tool design?

Answer 11

Wrist position, example, pistol vs. in-line grip?

Tools should be operable using a straight wrist

Question 12

What are certain concerns related to user populations of tools?

Answer 12

• Hand size affects tool grip size (different across male/female populations
• Handedness: Design tools that can be used by Right and left handed people

Question 13

Name some Guidelines for Tool design

Answer 13

Precision grip

• Grip btwn thumb and index finger
• grip thickness 8-13mm
• Grip length max 100mm
• Max tool weight 1.75kg
• Locking mechanism

Power grip

• Grip with whole hand
• Thickness 50-60mm
• Length minimum 125mm
• Max 100N grip force
• Noncylindrical grip shape preferably triangular with 110mm periphery
• Max tool weight 2.3kg, preferably abt 1.2kg
• Locking mechanism

General

• Smooth, slightly compressible and non conductve grip surface
• Avoid vibration esp. 50-100Hz
• Make handles used by either hand
• Keep wrist straight
• Tool weight balanced about grip axis
• Eliminate pinching hazards