EPT 221 ENGINEERING DESIGN

DESIGN for X

Design for X

The term used to describe any of the various design methods that focus on specific product development concerns.

X – any desirable attributes. Attributes can be: safety, reliability,

robustness, assembly, manufacture, environment, tolerances, maintainability, reliability, affordability (cost), environment (recyclability)/sustainability, ergonomics, aesthetics, standards, robustness, quality, etc.

Design for X: Safety

Injury Hazards Conditional Circumstances Legal Responsibilities Guidelines for Safe

Products/systems Safety Hierarchy Safe Design Principles

What is a safe product or system?

No injury to user, (products liability)

No injury to consumer /society

No injury to production worker (e.g. OSHA)

No damage to personal property

No damage to real property (environment)

Hazardshazard – a source of danger which has the potential to injure people or damage property or the environment

Hazards include (Lindbeck, 1995):

1. Entrapment hazards – machine parts move towards each other to create pinch points where fingers, hands, or other body parts can get pinched or crushed.

2. Contact hazards – hazards that come into contact with body parts such as hot surfaces, sharp edges, electrically charged parts.

3. Impact hazards– injuries occur when translating, rotating, or reciprocating machine parts collide with body parts. E.g. a hammer blow to the hand, fingers

4. Ejection hazards – debris particles flinging from moving machine parts. E.g. grinder sparks, saw dust, welding

5. Entanglement hazards – rotating shaft of work pieces that can catch hair or loose clothing.

6. Noise & Vibration –

Loud noises can result in hearing loss

Extended exposure to vibrations can result in Hand-Arm Vibration Syndrome (HAVS)

Others: fire, explosion, electromagnetic radiation

exposure to toxic, hazardous or radioactive substances

environmental hazards such as extremes in temperature, humidity, wind, ice, snow and lightning

Conditional Circumstances

1) hazard is inherent during normal use

E.g. sparks caused by normal grinding.

2) hazard originates from a component failure

E.g. a grinder has a rotating abrasive wheel. If a chunk of the wheel breaks

off during use, it may have sufficient kinetic energy to penetrate unprotected

human skin tissues and very likely to cause eye injury. This happens when

the abrasive fails to hold the wheel together.

3) hazard caused by user misuse

e.g. a user uses a bench grinder to grind an I-beam that is elevated 10 feet

off the floor, rather than using a portable grinder.

4) hazard exists during normal maintenance

e.g. service a person may be exposed to electrical shock when removing a

protective cover from a machine.

5) hazard created by improper maintenance

6) hazard stems from lack of maintenance

e.g. lack of exhaust muffler maintenance might lead to CO poisoning.

Legal Responsibilities (for safety, health and public welfare)

Product liability: a phrase used to describe a a seller or manufacturer responsibility to their customers under civil action or criminal action

Civil action: legal action taken by the injured party (the plaintiff) against the manufacturer or seller (the defendant) to recover damages for personal injury or lost to property caused by defects in design or manufacture.

Criminal action: legal penalty resulting in prison sentences directed at individuals who were negligent in the performance of their duties

Products Liability: Civil Actions, and Criminal Actions

Plaintiffs attorney will try to prove that the company or its employees failed to:

perform “appropriate analyses.” comply with published standards. make use of state-of-the-art technology, due to

ignorance. include reasonable safety features or devices. take into account how the user might misuse the

product. consider hidden dangers that might surprise the user. consider variations in materials, mfg processes, or

effects of wear. carry out appropriate testing, or interpret results

correctly.

Occupational Safety

OSHA : Occupational Safety and Health Act Employees are protected with regards to

occupational safety and employers are legally responsible for ensuring that their employees are protected from a variety of workplace hazards.

Guidelines for Safe Products/systems

1) Perform appropriate analyses 2) Comply with published standards 3) Use state-of-the-art technology 4) Include reasonable safety features or devices 5) Take into account how the user might misuse the product6) Consider hidden dangers that might surprise the user7) Consider variations in materials or manufacturing

processes, or effects of wear8) Carry out appropriate testing and interpret results correctly9) Provide adequate warnings10) Implement superior quality control 11) Document everything

Consider …..

A machine tool housing requires removal of a cover panel during servicing, exposing moving gears and links, which could cause pinching injuries. Some of the alternatives to resolve/remedy this problem are:1. Have the user turn off the machine, and ‘red-tag’ the on/off switch to alert other personnel (warn against the hazard)2. Redesign the cover/access such that the moving parts are not exposed (eliminate the hazard)3. Print a warning label on the access cover and in the user manual (warn against the hazard)4. Retrofit the machine with an ‘open-access-cover’ alarm (protect against the hazard)

Safety Hierarchy Method

1. Eliminate the hazard pro-active approach, “design-out” the hazard (eliminate any moving parts, hot or sharp surfaces)

2. Protect against the hazard passive approach, (machine guards, seat belts)

3. Warn against the hazard - weak remedy, (warning labels, alarms)

4. Provide training Provide and require operating training.

5. Provide personal protection – least effective, (safety glasses, gloves, shoes)

Safe Design Principles3 fundamental design principles to design safe products and systems:Safe-Life

entire predicted useful life without malfunction.designers to identify all operating conditions, misuses and abusesdesign appropriate maintenance and repair schedules.

Fail-Safe upon failure of a component, product/system shuts down safely, critical functions are sometimes still performed. (e.g. boiler feed-water valve failing in the open position)

Redundant design additional product components or systems are designed to take over the principle function of the failed component or system. (e.g. multi-engine airplanes, emergency brakes)

Summary (continued)

Safety is no accidentanonymous

Safety is no accidentanonymous

Design for Safety: Prevent injury or damage Hazards exist, and depend on conditions We have Legal Responsibilities Guidelines for Safe Products/systems Safety Hierarchy – maximize our design efforts Safe Design Principles

Design for X: Ergonomics

Human factors/ergonomics: a term used to describe the abilities, limitations, and other physiological or behavioural characteristics of humans that effect the design and operation of tools, machines, systems, tasks, jobs, and environments.

To achieve: userfriendliness, convenience, effectiveness, efficiency, increased productivity, improved safety, reduced fatigue or stress, increased comfort, greater user acceptance, increased job satisfaction, improved quality of life.

Customer Requirements

Example: analysis for a riding bicycle

What interactions occur between the rider and the bike?

What would a ‘poor’ design be?

Human-machine system

Models the interaction between user and product

Surrounding environment

Sensory inputs: seeing, hearing, touching, smelling, tasting.

Interface: any part of the machine that the human touches with a part of his/ her body or is exposed to. Also any component that the human sees, hears, or is exposed to. Also means by which human interacts with the product.

Machine: can be a consumer product or equipment, systems, facilities.

How humans interface with machines?

Design machines that fit the size of human hands, feet, arms, legs, chests. anthropometrics: a field of human factors that deals with the measurement of the human form such as height, reach.

Identify and accommodate the capacity of a human to correctly process information and make timely decisions (e.g. reducing reaction time).

Acknowledge human limits with regards to applying forces or torques.

Design product so that customers can use it in ideal weather or foul, or during various phases of use including setup, operate, maintain, repair, take-down, disassemble, recycle, and dispose.

Design for X: Environment

Design for minimal use of materials. Design for recyclability-returning recyclable

materials back into the product stream. Design for remanufacture-disassembly,

inspecting, cleaning, replacement of worn or broken parts

Design for energy efficiency-during manufacture and during usage

Design for workplace-OSHA

Reference: Hewlet Packard’s ….

Hewlet Packard’s notebook is designed according to the company’s Design for Environment (DfE) Guidelines.

DfE has 3 priorities: i. Energy efficiency: to reduce the energy

needed to manufacture and use HP products.

ii. Materials innovation: reduce the amount of material used in HP’s products and develop materials that has less environmental impact and more value at end-of-life

iii. Design for recyclability-design equipments that is easier to upgrade and/or recycle.

Continued… HP’s DeF recommends that its product designers consider the following for their

design: Place environmental stewards on every design team to identify design changes

that may reduce environmental impact throughout the product's life cycle. Eliminate the use of polybrominated biphenyl (PBB) and polybrominated

diphenyl ether (PBDE) flame-retardants where applicable. Reduce the number and types of materials used, and standardize on the types

of plastic resins used. Use molded-in colors and finishes instead of paint, coatings or plating whenever

possible. Help customers use resources responsibly by minimizing the energy

consumption of HP's printing, imaging and computing products. Increase the use of pre-and post-consumer recycled materials in product

packaging. Minimize customer waste burdens by using fewer product or packaging

materials overall. Design for disassembly and recyclability by implementing solutions such as the

ISO 11469 plastics labeling standard, minimizing the number of fasteners and the number of tools necessary for disassembly.

HP’s Design for Environment (DfE) The Design for Environment program has three priorities:

i. Energy efficiency – reduce the energy needed to manufacture and use our products ii. Materials innovation – reduce the amount of materials used in our products and develop

materials that have less environmental impact and more value at end-of-life iii. Design for recyclability – design equipment that is easier to upgrade and/or recycle

HP's DfE guidelines recommend that its product designers consider the following:• Place environmental stewards on every design team to identify design changes that may

reduce environmental impact throughout the product's life cycle. • Eliminate the use of polybrominated biphenyl (PBB) and polybrominated diphenyl ether

(PBDE) flame-retardants where applicable. • Reduce the number and types of materials used, and standardize on the types of plastic

resins used. • Use molded-in colors and finishes instead of paint, coatings or plating whenever possible. • Help customers use resources responsibly by minimizing the energy consumption of HP's

printing, imaging and computing products. • Increase the use of pre-and post-consumer recycled materials in product packaging. • Minimize customer waste burdens by using fewer product or packaging materials overall. • Design for disassembly and recyclability by implementing solutions such as the ISO 11469

plastics labeling standard, minimizing the number of fasteners and the number of tools necessary for disassembly.

Ex: Notebook PC

Reduction of hazardous waste• Plastics greater than 25 grams have no halogenated flame

retardants • No use of polyvinyl chloride (PVC) except for cables. • No use of polybrominated biphenyls (PBBs), polybrominated

biphenyl ethers (PBDEs) also known as polybrominated biphenyl oxides (PBDOs)

• Batteries do not contain mercury or cadmium or do not contain mercury or cadmium at a concentration currently prohibited by law.

• Cadmium has not been used as a stabilizer, coloring agent or as a surface treatment for any parts, components or material in this product.

• Mercury in laptops is less than 5mG per LCD • No use of ozone depleting substances in product manufacturing

Resource conservation • Packaging is made of 66%

minimum of post-consumer recycled cardboard.

• Manuals are printed on elementary chlorine free (EFC) bleached virgin or recycled paper or put on CD-ROM to minimize paper use

Design for Recycling• Marking plastic parts weighing

more than 25 grams according to ISO 11469 for easier sorting

• This product is designed for easy disassembly during recycling. Use of glues, adhesives and welds from product construction has been avoided where feasible.

• Large mechanical plastic parts consist of one material or are made of easily separable materials

• The product uses common fasteners

• The product includes snap-in features

Power consumption All Business and Consumer

notebook PCs are ENERGY STAR® qualified. Currently, there are six product families that are Energy Star qualified: OB4150, OB900, OBXE2, OBXE3, OB6000/6001, and OB500.

Some notebook PCs with Intel SpeedStep Technology enables the processor to automatically switch to lower, power-saving speeds or switch to higher-performance speeds according to the workload.

Set display brightness to lowest comfort level to conserve energy / battery life

Power management settings Standby-mode

Saves significant power Turns off the display and other components Maintains current session in RAM Restarts quickly Restores network connections Power mode status light is blinking Customers instructed not to disable

standby mode Default setting on AC power = standby

within 20 minutes of inactivity Default setting on battery power = standby

within 5 minutes of inactivity Hibernate mode

Saves maximum power Saves current session to disk, then shuts

down Restores network connections Power mode status light is off Default setting on AC power = hibernate

within 3 hours of inactivity Default setting on battery power = hibernate

within 2 hours of inactivity

Design for X: Affordability

Engineering economics concerns with understanding the economic or financial implications of engineering decisions, including:• choosing among alternatives (e.g. cost benefit

analysis), • deciding if or when to replace machines or

other systems (replacement analysis), and • predicting the full costs of devices over a

period of time that they will be owned and used (life cycle analysis).

Rules for minimising costs

Aim for low complexity, i.e. a low number of parts and few production processes.

Aim for small overall dimensions to reduce material costs, because these costs increase disproportionately with size, most frequently diameter.

Aim for large numbers (large batch size) to spread the once-only costs.

Aim for minimising precision requirements i.e. specify, where possible, large tolerances and rough surface finishes.