Chapter 7

1. Chapter 7 Ergonomics and Workstation Design Space Requirements

2. Objectives • After reading the chapter and reviewing the materials presented the students will be able to: • Understand ergonomic principles as applied to workstation design. • Understand the concepts of motion economy. • Be able to apply these principles and concepts to work space planning and space determination.

3. Workstation Design • The result of ergonomics and workstation design is a workstation layout, and the workstation layout determines the space requirements. • The manufacturing department total space requirements are a total of individual space requirements plus a contingency factor. • Ergonomics is the science of preventing musculoskeletal injuries in the work place. • Design the workstation so that the task fits the person rather than forcing the human body to fit the job. • Improper workstation design costs the American industry millions of dollars annually in lost productivity, health, and job related injuries and accidents.

4. Ergonomics and the Principles of Motion Economy • Effectiveness is doing the right job. • Efficiency is doing the job right. • Safety and efficiency should be the goals of every workstation designer. • Ergonomics and the principles of motion economy should be considered for every job.

5. Principle 1: Hand Motions • First of all hand motions should be eliminated as much as possible. Let a machine do it. • If hand tools are used they must be designed ergonomically, and they must be easily adapted to both left handed and right handed people. Over 10% of the people are left handed. • Combine motions to eliminate other motions. • Make motions as short as possible, and eliminate leaning. • Locate frequently used tools and materials closer to point of use. Place heavy materials closer to the point of use.

6. Principle 2: Basic Motion Types • Ballistic motions are fast motions created by putting one set of muscles in motion, and not trying to stop those motions by using other muscles. • Controlled restricted motions require more control especially at the end of the motion. Controlled motions are to be considered first for elimination because they are costly, fatiguing, and unsafe. • Continuous motions are curved motions. When the body has to change direction, speed is reduced.

7. Principle 3: Location of Parts and Tools • Have a fixed place for all parts and tools and have everything as close to the point of use as possible. • Looking for parts wastes time. • Reaching for something is fatiguing. • You can place parts in two or three tiers to make them visible.

8. Principle 4: Freeing the Hands From as Much Work as Possible • Fixtures and jigs are designed to hold parts so that the worker can use both hands. • Foot operated control devices can be designed to activate equipment to relieve hands from work. • Fixtures can be electric, air, hydraulic or manually activated. • A hex nut can be placed in a hex shaped hole that has no clamping need, but it will be held firm because of the part and fixture shape. • Many tooling vendors would love to supply you with fixture building material and devices (fig 7-12, page 205).

9. Principle 5: Gravity • Gravity is free power. • Gravity can move parts closer to the operator. • Large boxes of parts can be moved into and out of workstations using gravity rollers and skate wheel conveyors. • Slide chutes can carry punch press parts away from the die without operator assistance by using jet blasts of air, mechanical wipers, or even the next part pushing the finished part from the die.

10. Principle 6: Operator Safety and Health Considerations • Keep safety hazards in mind and anticipate emergency action requirements while designing the workstation. • The correct work height is elbow height. Light work can be 2 inches above elbow height, whereas heavy work should be 2 inches below elbow height. • To maintain correct work height have adjustable workstations. Design the station for the tallest person and provide platforms for the shorter people, or adjust the work height on the top of the workstation. • The closer the work is, the more need there is for light. The best place for the light is over the work and slightly over the back, but not casting a shadow. • Operator space should be 3 x 3 feet. Three feet off the aisle is adequate for safety and 3 feet from side to side allows parts to be placed comfortably next to the operator. If machines need maintenance and cleanup, a 2 foot access should be allowed around the machine.

11. Space Determination • The space determination for most production departments starts with the workstation design. • Multiplying the total workstation design square feet by 150% allows for extra space for the aisle, work in process, and a small amount of miscellaneous extra room. • It does not include restrooms, lunchrooms, first aid, tool rooms, maintenance, offices, stores, warehouse, shipping or receiving.

12. Summary • Ergonomics is the science of preventing musculoskeletal injuries in the work place. • Design the workstation so that the task fits the person. • First of all hand motions should be eliminated as much as possible. Let a machine do it. • If hand tools are used they must be designed ergonomically, and they must be easily adapted to both left handed and right handed people. Over 10% of the people are left handed. • Controlled restricted motions require more control especially at the end of the motion. Controlled motions are to be considered first for elimination because they are costly, fatiguing, and unsafe. • Have a fixed place for all parts and tools and have everything as close to the point of use as possible. • The correct work height is elbow height. Light work can be 2 inches above elbow height, whereas heavy work should be 2 inches below elbow height. • Operator space should be 3 x 3 feet. Three feet off the aisle is adequate for safety and 3 feet from side to side allows parts to be placed comfortably next to the operator. If machines need maintenance and cleanup, a 2 foot access should be allowed around the machine. • Multiplying the total workstation design square feet by 150% allows for extra space for the aisle, work in process, and a small amount of miscellaneous extra room. • It does not include restrooms, lunchrooms, first aid, tool rooms, maintenance, offices, stores, warehouse, shipping or receiving.

13. Home Work • What is ergonomics? • What is the correct work height ? • How much operator space should be allowed?