ME2101 - Design Process-2013 (B&W).pdf

A/Prof. M O Lai

Room: E2-02-23

E-mail address:[email protected]

Tel: 6516 2577

Some information….There is NO final examination for this module !

Assessment is based on one small group design assignment (25%) and a quiz (75%). (Small group = minimum 2 maximum 3 students)

Tutorial: Prof Lai – NoneProf Seah – Yes

Schedule of lecture:

Prof Lai - First 3 weeks (25% mark):Design process (Design assignment)How to design a successful productHuman factors (?)

Prof Seah – Middle 6 weeks (50% mark)

Prof Lai – Last 3 weeks (25% mark):Design against fatigue leading to design of shaftsSelection of rolling bearingsSelection of materials

Text books:

Prof Lai – None

Prof Seah – Mechanical Engineering Design by Shigley/Mischke, McGraw-Hill.

What is engineering design?

Engineering design is a purposeful activity directed toward the goal of fulfilling human needs, particularly those which can be met by technological factors of our civilization.

Goal (or need) orientedVariformConstrainedEvolutiveProbabilisticValue comparativeCompromising

Characteristics of Engineering Design:

The relentless pursuit of Perfection

Design philosophy

The Concorde

On Wednesday 26th July 2000 ……

The aftermath….

Metal strip which fell off a Continental DC-10 punctured the wheel the Air France Concorde during take-off

The Concorde

Note the location of the wheels and the engines

Note the location of the wheels and the engines

Boeing 747

Airbus A380

What are the design problems?

Could the engines be placed further away from the wheels? - Space constraint due to delta wing design?

Could the engine intake be redesigned to be slanted?

Delta wing

Existing design New design ?

Could not the underside of the wing near the wheels be strengthened or made with tough but light-weight materials so that fuel tank could not be punctured?

The Straits Times 4 Feb 2010

Conclusions:

There is still much to learn in area of design……

Design engineers have still a long way to go to design perfectly safe structures !

The Engineering Design Process

Product life cycle

Design Disposal

UseManufacture

Nee

dM

arket

Morphology of Design Process

Recognition of need

Specifications and requirements

Feasibility study

Idea generation and development

Detailed design

Production of design

Sale/Usage

Obsolescence

Identification of constraints imposed

Prototyping/Evaluation

Application of Design Process

Case Study –

Design of a DIY Concrete Mixer

First step is to identify specific need (or market) that is to be satisfied by a solution based upon technology.

Engineering design is a purposeful activity directed toward the goal of fulfilling human needs.

Driving forces behind design projects may come from….

Recognition of need

Recognition of Need

Impetus from designer sponsor:Customers, government agencies, etc

Impetus from a changing market

Impetus from a changing customer or stakeholder needs

Impetus from technological breakthrough

Sony Walkman: Portable and individual music

Examples of design needs:

Aircraft-safe bullets: Counteract hijackers but save the plane

The Watercone

Need:

50% (2.5 billion) of world’s population has no access to clean, drinkable water.

How to design an innovative, inexpensive, simple but functional product to create potable water?

African Sahara Desert beetle

Moisture in air condenses on surface. Droplets roll

down and collected at rim.

Need: To fulfill the craze of buyers for rockets and jet engines in the Post WWII period.

1959 Cadillac Cyclone

1956 Oldsmobile Rocket 1959 Cadillac Biarritz

Need: To fulfill desire of those who missed owning a classical car; to arouse nostalgic emotion of older drivers and attract Y-generation car buyers.

Mazda Miata VW Beetle

Mini Cooper Fiat 500

Existing product may need to be redesigned to:

• eliminate shortcomings by incorporating new technology and manufacturing methods

• better serve changing needs of users

• to meet competition in the marketplace

• reduce cost of the product

Good design is good business……

All products can be improved through design……

Nik

e Tr

iax

Wat

ches

Con

vent

iona

l W

atch

es

Nike sport shoes

Run-away alarm clock

Fly-away alarm clock that makes mosquito noise

aXbo Sleep Phase Alarm Clock

During sleep, each person goes through various sleeping cycles each of 90 to 110 minutes.

Automation of Processes

Lance Armstrong’s Tour de France Bicycle

MICHELIN® TWEEL™

MICHELIN® TWEEL™

Waterlessurinal


Recognition of need


Client may impose constraints to fit budget, company manufacturing capabilities or market niche.

Additional constraints may be:Convention or code (such as building codes)Compatibility with existing equipment (eg. Standard tire sizes)Compatibility with mating parts of an assemblyAvailable power requirement (eg. 220V, 15amps, etc)Regulatory requirements (eg. Auto emission rules)Industry standards (eg. Thread on a light bulb base)Product environment (eg. Temperature, pressure, humidity)


Recognition of need



Ferrari Lamborghini

6 Speed Manual Standard Transmission 6 Speed Manual3.6L V8 Standard Engine 6.2L V123586 Displacement (cc) 619240 Valves 48400 at 8500 rpm Horsepower 571 at 7500 rpm276 at 4750 rpm Torque (lb/ft) 479 at 5400 rpm35.4/35.4 Steer Diameter (Curb) 41.2/41.2MID/RWD Engine Location/Drive MID/4WD-FTDisc/Disc Brakes (Fr/Rr) Disc/Disc215/45R18 Tires 245/35R183197/NA Curb Weight 3638/NA102.3 Wheelbase(Fr/Rr) 104.965.7/63.6 Track 64.4/66.7176.3 Length 180.375.7 Width 80.548.6 Height 44.7

Lamborghini - Murcielago 6.2Ferrari - 360 Modena Spider

Key Features :• 1.8in. LCD display • Resolution: 640 x 480 pixels, 320 x 240 mode • No. of pictures: 15 at 640 x 480, 50 at 320 x 240

Additional Features :• Automatic focus • Self-timer • Automatic power-saving mode • Video cable included for TV view • 3 Flash modes: Autoflash, Force Flash, and No Flash • JPEG compression

Specifications :• Internal memory: 2MB • Flash Range: 3 to 6 feet (1 to 1.8 m) • Focus Range: 3 feet (1 m) to infinity • Batteries: 4 AA (included) or AC adapter (included) • Packaged with PhotoMAX SE Software • Dimensions 2.63 in.H x 5.38 in. L x 1.88 in. D • Weight 10 oz. (with batteries)

System Requirements :• Windows 95 or 98 only, CD-ROM drive, 32MB RAM memory, 85MB hard drive space, VGA monitor with 16-bit display card, 24-bit recommended, Sound card (recommended), Available RS-232C serial port

PhotoMAX Fun Flash 640 digital camera from Polaroid

Example of Design Specification:

Portable Winch

Design Brief

From internal market research, it has been decided that IWC needs to design a general purpose winch to sell to the cable and pipe laying market sector. The winch should be portable but have mounting points for the end user. It is important that the winch sits within our current range of 'Excel General Purpose winches'.

1.0 Performance1.1 Lift / lower a load of 2.5 tonnes (+/- 10%).1.2 Draw in cable in at a rate of 0.2 m/s.1.3 Winch drive should cut out when the load exceeds 10% of the specified load.1.4 Drive to stop lowering load when only 1.5 metres of cable remains on drum.1.5 Winch should operate with forward, reverse, stop and inch facility.1.6 Any braking system employed, should produce a braking torque of 150% the full load torque.1.7 Winch should have a manual device to control the brake release and load descent in the event of a power failure.1.8 In the event of the winch 'overrunning', a manual safety relay/braking device should operate within 1 second or before the load exceeds a speed of 3m/s.1.9 The product should be portable but with the option for permanent mounting.1.10 The product must use a portable power source, preferably a diesel engine.1.11 The weight of the product must be sufficient to aid the stability of the product.1.12 Efficiency of the unit should be high, preferably in the area of 20 - 30%.1.13 The drum should hold 50m of cable.

2.0 Environment2.1 The winch drive and power unit should be power unit.2.2 The unit will be mainly used in European weather conditions. But we could expect sales of about 2% unit volume to the Far East.2.3 Temperature ranges:

-28 degree C - European12 - 44 degree C - Far East

2.4 The product may experience humid conditions.2.5 Corrosion resistance may be considered by the use of special materials or surface protection methods.2.6 Any noise from the equipment should not exceed 95 dB at a distance of 1.0m.2.7 The winch will be stored in suppliers warehouses before sales.

3.0 Product Life Span3.1 Product will be on the market for 10 years.3.2 Spare parts will be available for a further 5 years after that.

4.0 Life in Service4.1 Should withstand an operating period of 1 hr uninterrupted use per day for 5 years.4.2 Life in service should be assessed against the criteria outlined in the Performance and Environment categories.

5.0 Shelf Life5.1 The product will be stored on-site for up to 1 month before dispatched.5.2 Our Far East distributor may store the product for several months.

6.0 Target Costs6.1 The product should have an end-user cost of £5500 within Britain.6.2 The cost of manufacture should be less than £2750.6.3 The cost of packaging and shipping should be no more than 15% of the manufacturing cost.

7.0 Quantity7.1 150 units in the first year, increasing to 800 within four years.

8.0 Maintenance8.1 To be maintenance free except for light lubrication once a month and a recommended service every two years.8.2 Parts requiring lubrication should be accessible within 15 minutes without the use of special tools or equipment.8.3 All fasteners used should comply with BS6105.8.4 Spares should be available for 5 years after the product is replaced with a new model.8.5 No special tools should be required for maintenance.

9.0 Marketing9.1 Initially to be manufactured for European market but Far Eastern distributors in Singapore, Hong Kong and Australia will find a market.9.2 The winch should be operating against equivalent models which include the following companies:

Swansom - England Oholom - Sweden Winderhock - Germany

9.3 Applicable markets:Telecom - Cable laying Gas and Electricity operators Pipe laying services Civil Engineering Operations

9.4 Summary of market requirements:Portable winch which can be attached to vans and low loaders Use portable power source To be used in all weather To allow one man operation To have at least 40m of cable To pull 2000kg

10.0 Packaging10.1 Packaging / transport cost should be kept to a minimum and preferably below 5% of the unit cost.

11.0 Size and Weight Restrictions11.1 Weight should not exceed 500 kg.11.2 Length not to exceed 2500 mm.11.3 Width not to exceed 2000mm.11.4 Height not to exceed 2000mm.

12.0 Shipping12.1 Product will be shipped by road within Europe.12.2 Product will be shipped by sea to Far Eastern markets.

13.0 Manufacturing Processes13.1 Capacity is available for current market demand within scope to increase production to 200 per year without investment / expansion.13.2 Motors, transmissions, bearing and ropes are bought in from the following suppliers:Drives:

Electric Motors - Brook Compton Diesel Engines - Gardener Hydraulic Motors - Hydrostatic Transmission Ltd

Bearings:RHP Bearings

Transmissions:Couplings - Wellman Bibby Worm Gears - Reynold Planetary Gears - David Brown (PPG Divisions) In-Line Gears - David Brown Radicon Ltd V-belts - Fenner

Ropes:Bridon

13.3 Castings and injection moulds produced by external suppliers.

14.0 Aesthetics14.1 The form can follow function.14.2 If cost dictates, the winch should look attractive to improve our perception within the market.

15.0 Ergonomics15.1 Controls to be mounted in an accessible position, relative to the operator i.e. waist height - around 1m, to accommodate 95% of the working population.15.2 All controls should be hand operated, requiring one-hand operation with a maximum force of 1.5 N/m215.3 One man should be able to operate the product.

16.0 Customer RequirementsSee Marketing

17.0 Competition17.1 The winch will be operating against equivalent models which include the following companies:

Swansom - England Oholom - Sweden Winderhock - Germany

18.0 Quality and Reliability18.1 Quality should be such that winches should not generally fail within a period of three years and only 1 in 50 should fail within the first year.18.2 No winch should fail in the area of the safety overload device.

19.0 Standards and Specifications19.1 Standards to be adhered to:

BS 5000 part 99 Motor Performance BS 6105 and BSEN 20898(1) Bolts BS 6322(2) & BS 4320 Nuts and washers BS 7676 and BS 4517 Gears BS 3019 Welding BS 5989 Bearings BS 2754 Electrical Insulation BS 5646 pt4 Bearing Housing BS 4235 Keys and Keyways BS 7664 Painting BS 1399 Seals

20.0 Company Constraints20.1 None - except those outlines in Manufacturing and Processes.

21.0 Processes21.1 All components to be of metric form and comply with ISO 4900 for limits and fits.

22.0 Safety22.1 No winch should fail in the area of the safety overload device.22.2 Winch should not operate when maintenance is being carried out.

23.0 Testing23.1 Testing is to be carried out on 5% of units.23.2 All cables should be tested to BS3621.

24.0 Legal24.0 Possible litigation lies in the user injuring themselves by having access to moving parts during winch operation.

25.0 InstallationN/A

26.0 Documentation26.1 Product should be supplied with a user manual covering winch operation and maintenance.26.2 Suppliers require maintenance and repair manual.

27.0 Disposal27.1 Plastic parts should be separable and marked to aid disposal.

Design specs may be of several types:

PhysicalSpace allocation; dimensional requirement; weight limits; energy/power requirements…

EnvironmentalMoisture limits; dust levels; intensity of light; temperature range; noise limits……

Functional or operationalAcceptable vibrational ranges; operating times…

EconomicLimits on production costs; operating costs; service/maintenance requirements; existence of competitors; equipment depreciation…

LegalGovernment safety requirements; environmental/pollution control codes; production standards…

Human factors/ergonomicsStrength; intelligence; anatomical dimensions of users…


Recognition of need


Feasibility study


Aim: to verify possible success or failure of a design proposal from technical and economic standpoint.

Some factors to consider:Any natural law defied?Any specs beyond technically available currently?Any dependency on scarce materials?Product cost being too high?Any public objection to use of product?


Recognition of need


Feasibility study



This is most challenging part of design where innovative ideas are generated (through brainstorming)

All possible ideas are examined carefully and unbiasedly

Best solution is chosen for preliminary design

Overall configuration is made to establish functional relations between various parts and systems to validate the functional and overall size requirements of design specifications


Recognition of need


Feasibility study




Built and test prototype to evaluate performance and to decide upon modifications required.

At least three construction techniques available:

1. Mock-up :–

Generally constructed to scale from plastics, wood, cardboard, etc to give designer a feel of the design

Purpose – to check clearance, assembly techniques, manufacturing considerations, and appearance

Least expensive

May be replaced by solid model in CAD system

Often referred to as Proof of Concept prototype

Mock-up

2. Model :-

This is a detailed visual, mathematical, 2-D or 3-D representation of the design, often used to test ideas and/or make changes to a design

Purpose – test some of the functions or features of the final design

Often referred to as Proof of Product prototype

Computer Models

3. Prototype :-

This is a full-scale working model of a design intended to have complete form, fit and function of the intended design

Purpose – test a design concept by making actual observations and making necessary adjustments

Most expensive technique but produces the greatest amount useful information

Prototypes

Prototype of J-20 Stealth fighter, China - 2011

Other departments involved at this stage of design include:

ManufacturingMaintenanceMaterials, etc

Some questions to ask:

Can material be changed to improve product?Can parts be fabricated?What is the best process to fabricate them?Fabricate in-house or sub-contract out?

More questions to ask:

Can amount of material required be reduced?Can assembly time be reduced? Or made easier?Can number of drawings be reduced?Is there a simpler way to design it?Can it be made from standard parts?Is it more economical to buy part than designing and manufacturing it?How do others do it? Copy it? Modify it? Improve it? Buy it for your own use?


Recognition of need


Feasibility study


Detailed design



Finalise and fully design all components and systems with dimensions/tolerances, materials selection, quantity, and assembly details

Prepare all working drawings

Verification/Approval of drawings


Recognition of need


Feasibility study


Detailed design




Approve detailed design and produce product

Consider capital investment to pay for for materials, labour, subcontractors, fabrication, and loan etc.

Time schedule for production and delivery dates

Network analysis chart: indicates a prototype design time of 12.5 weeks is required (critical path along tasks 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 and 24)


Recognition of need


Feasibility study


Detailed design


Sale/Usage



Ensure supply of raw materials/services

Distribution of

Advertising and marketing

Pricing to ensure optimum sales and profits

Feedback of public opinion

Availability of spare parts and services


Recognition of need


Feasibility study


Detailed design


Sale/Usage

Obsolescence



At end of useful life, product should not be capable of prolonged operation

Product to be succeeded by new improved version or scrap?

Disposed? What about environment?Recycleable?

Example: Sony Walkman

Before the Walkman is obsolete, new technologies and features have been introduced to prop up the sale of the product.

History of innovation of Walkman 1979-1988:

Feature Company Date ImitatedWalkman Sony 1979 yesMini headphones Sony 1979 YesAM/FM stereo radio Sony 1980 yesStereo recording Sony/Aiwa 1980/1 yes

Feature Company Date ImitatedFM tuner cassette Toshiba 1980/1 noAuto-reverse KLH SOLO 1981/2 yesFM headphone radio Sony 1981/2 yesDownsized unit Sony 1982 yesDolby Sony/Aiwa 1982 yesDirect drive Sony 1982 noCassette-sized unit Sony 1983 yesShort-wave tuner Sony 1983 noRemote control Aiwa 1983 yesDetachable speakers Aiwa 1983 yesWater resistance Sony 1983/4 noGraphic equalizer Sony 1985 yesRechargeable Sony 1985 yes

Feature Company Date ImitatedSolar-powered Sony 1986 noRadio presets Panasonic 1986 yesDual cassette Sony 1986 noTV audio band Sony 1986/7 noDigital tuning Panasonic 1986/7 yesChild’s model Sony 1987 yesEnhanced bass Sony 1987/8 yesVoice activated Toshiba 1988 no

As worldwide sales grew rapidly, competition became intense. To maintain market share and leading position, Sony had to continually develop and launch improved products, even before existing ones became obsolete.

Recognition of need


Feasibility study


Detailed design


Sale/Usage

Obsolescence



Application of Design Process

Case Study –

Design of a DIY Concrete Mixer

KonKret-miKs Ltd, also known as 3KCompany, designs and produces a wide range of building construction equipment.

Market Research Department of 3KCompany has identified a gap in the market for low-cost low-capacity concrete mixers suitable for practical do-it-yourself enthusiasts.

Recognition of need

Board Meeting decisions:

Present: Managing DirectorSales DirectorTechnical ManagerWorks DirectorMarket Research Manager

Decisions:

a) Draw-up specifications, etcb) Design mixer

Further market research data:

Suggested price: approximately S$750

Sale forecast: approximately 5,000 units per year (export to neighbouring countries)

Configuration: Compact, light weight, easily dismantled for transport in a small station-wagon or estate car


Capacity 60 liters mixed batch (equivalent to an average wheel barrow load)

Dimensions 420 mm diameter drum opening1050 mm total height610 mm maximum between wheels

Drum speed Approximately 30 rpm.

Assembly All items easily assembled and dismantled by average DIY person using basic tools

Drive(suitable for domestic supply)

0.25 kW (1/3 hp), single phase, 50 Hz electric motor, speed 1450 rpm.


Final specifications cannot be determined until:

A prototype model has been designed, fabricated and tested.

Cost analysis is completed; customer feedback obtained after a trial batch of at least two units has been sold and used.

(1) Conditions of use:

Mixer must be able to mix quantities of cement, water, sand aggregates or plaster in varying proportions under its own power, without spillage

It should be light, portable, manoeuvrable around garden or work area; transportable in small station wagon or estate car

Performance and reliability of mixer not affected by climate condition

Requirements to be considered:

(2) Characteristics of components:

Mixing drum: plastic injection molded or welded steel cone;

supported by bearings; 2 heavy-duty mixing blades;

Drive: speed reduction from motor by gears or belt drive

Guard: welded steel plates

Wheels: two wheels, diameter 200 mm, plastic injection molded or welded steel plates

Tilt-handle: detachable from

main frame for transport, circular

steel tubes, long enough for easy

tipping, ergonomic as per 5th %tile man

Frame: welded steel angles or plates or tubes; ensure stiffness but minimum

materials to reduce weight

Mouth: easily loaded with shovel, and enable fast emptying

(3) Ergonomic considerations:

Size and height of drum (and whole mixer) for filling and tippingEase of manoeuvrabilityEase of tippingComfortable grip of tilt-handleEase of assembly, dismantling and maintenanceWeight of dismantled partsAvailability of tools (for assembling and dismantling)

(4) Aesthetics (appearance) considerations:

Should look symmetrical and stable; give impression of precision and efficiency of function; quality of manufacturing; pleasing continuity of profile; refreshing up-dated sense of styling suitable for display in catalogue

Flat surfaces and smooth lines to enable easy cleaning

Steel surfaces be given double coats of paint (prime and finishing) against rust, weather and rough treatment; pleasing colour choice on drum and guard, contrast with black frame and wheels

(5) Performance:

Prototype to be tested for performance under similar conditions as in actual service

Should allow some overloading; to cope with severe cases, motor to be fitted with thermal overload and reset button

(6) Life and reliability:

Useful life = 7 years under full loading capacity for stated number of hours per day and days per year operation

Prototype to be tested under stated conditions with intermittent stop/start

Periods between lubrication and change of parts during prototype testing should be quoted in final specification

(7) Packaging:

Mixer to be supplied in totally dismantled form packed in cardboard carton with assembly instruction booklet and warranty card (for motor only)

Instruction manual to consist of mixer in exploded view with parts numbered; parts to be listed with corresponding numbers

(8) After-sales service:

Servicing to be done by owner with aid of instruction booklet and standard workshop tools.

General spare parts available are:Pulleys and beltsShafts (for gears and drum)MotorBearings

Special parts (in small quantity) available are:DrumWheelsGuardTilt-handle

(9) Obsolescence:

Mixer be scraped at end of useful life

Metal parts to be reused or recycled

Plastic (if used) parts be made of recyclable or bio-degradable materials

Feasibility evaluation:

Mixer is technologically and economically feasible to be designed, fabricated and marketed

Motor/Gear box: to be purchased as standard parts; available

Guard: formed and welded in-house

Wheels and rims: purchased as standard parts; available

Mixing drum, internal parts and

structures: formed and

welded in-house; if plastic drum, be

sub-contracted out; quality to be

ensured

Frame and tilt-handle: formed and welded in-house

Feasibility study

1 Order of drive motor 0.5 week

2 Delivery of motor 4 weeks

3 Synthesis and evaluation of drive system 0.5 week

4 Order of pulleys and belts (if chosen in design) 0.5 week

5 Delivery of pulleys and belts 2 weeks

6 Cost analysis of drum 0.5 week

7 Order of Drum 0.5 week

8 Delivery of drum 6 weeks

9 Cost analysis of wheel and rim 0.5 week

10 Order of wheels and rims 0.5 week

11 Delivery of wheels and rims 5 weeks

12 Selection and order of bearings 0.5 week

13 Delivery of bearings 3 weeks

14 Analysis of frame and tilt-handle 0.5 week

15 Comparison and evaluation of frame 1 week

16 Design calculations 1 week

17 Design drawings/sketching 1 week

18 Overall cost analysis of product 1 week

19 Re-design for cost (if necessary) 0.5 week

20 Detail drawings and instruction manual 1 week

21 Fabrication of frame, handle, gears, shafts, guards, etc 2 weeks

22 Assembly of whole mixer 0.5 week

23 Testing of mixer 3 weeks

24 Re-design for function (if necessary) 1 week

Planning schedule -

Network analysis

chart:

to determine design time

to produce a fully-tested

prototype mixer. Table

shows allotted

tasks

Network analysis chart: indicates a prototype design time of 12.5 weeks is required (critical path along tasks 14, 15, 16, 17, 18, 19, 20, 21, 22, 23 and 24)

Some possible solutions


Some possible

solutions

1.25m

1.0m

After some brainstorming sessions and evaluation: design below is deemed best for simplicity and cost

Idea generation/development of tilt-handle

Idea (a) Idea (c)Idea (b)

Idea generation/development of supporting frame

Idea (a) Idea (b) Idea (c)

Idea generation/development of drive(reduce motor speed = 1450rpm to drum speed = 30 rpm; speed reduction = 48.3 : 1)

Idea (a) Idea (b) Idea (c)

Worm gear box expensive; and

unnecessary

Worm gear box bulky, heavy, and

expensive

Simple, neat and low cost; no gear box needed

Human factors:

To estimate frame dimensions, estimated full weight of concrete mixer, comfortable lifting force of a 5th

percentile adult man (from anthropometric data charts) at 315mm handle height, are considered


Details of support structure: Size of rectangular hollow steel sections as supporting frame calculated for bending and torsion with critical area at base of upright pedestal to support drum shaft assembly and handle

Details of wheel axle:Circular steel tube used and size calculated for bending

Handle tube sized to be 33.7mm outside diameter with 2.6mm thickness using max bending moment

Drum shaftdoes not transmit torque; sized using maximum bending stress

Examples of detail calculations:

Details of drum support assembly.

Note fabrication method and belt

tension adjusting method

Pinion-shaftcalculated for combined bending and torsion under fatigue loading. Stress concentration factor at weakest point considered

Selection of standard components:

Bought-out components like belt drive, pulleys and rolling bearings selected from manufacturers’ catalogues

Sizes of bolts and screws determined for tensile and shear loading

Cost Analysis:

Unit cost of mixer = $500

Fixed cost per batch (5,000 units) = $350,000

For 5,000 units, total cost = $350,000 + ($500 x 5,000) = $2,850,000

For $750 selling price, total income = 5,000 x $750 = $3,750,000

Profit expected = $900,000.

Re-design for cost:

Unit cost of mixer of $750 appears reasonable

To be competitive, comparison is made with competitors’ products:

List price RemarksCompetitor A $1104 30% discount for multiple orders

Competitor B $1092 Selling at 15% below list price

Competitor C $950 25% discount for multiple orders

Competitor D $1560 Selling at 15% below list price

Competitor E $840 Selling at 10 % below list price

Actual cost comparison:

List price Actual costCompetitor A $1104 $773Competitor B $1092 $928Competitor C $950 $713Competitor D $1560 $1326Competitor E $840 $756

To be competitive with competitor C, propose initial price be discounted by at least 5%.

Better to re-design to reduce cost: Use less robust drum; reduce quality of electric motor, use thinner steel structures, etc

Re-design for function:

Prototype mixer fabricated, tested and analyzed

Torsional deflection of motor-mounting plate caused excessive vibration under dynamic loading

Motor-mounting re-designed with flange rather than stiffening plate

Rigidity of motor-mounting plate improved with flanges

Working drawings are

drawn

Detailed design

Final product:

Mixer stand (optional extra):

Stand may be needed for tipping concrete directly into wheel barrow

Designed using steel tubes welded together; feet with rubber stoppers to ensure stability

Rubber stopper

Optional stand for tipping concrete directly into wheel barrow

Instruction booklet:

Information in instruction booklet include:

Part list of mixer

Assembly instruction of mixer

Maintenance and care

1

1A2

34

56

78

8A9

1011

1213

1415

1617

1819

19A20

2122

2324

2526

2728

Exploded view of

mixer showing

assembly procedure

Dismantled parts of mixer

Opening of cardboard carton in

which complete mixer is packaged

for assembly

Ope

ratin

g in

stru

ctio

ns

Dismantled for transport in a small station wagon at end of use

ME2101 - Design Process-2013 (B&W).pdf

Documents

design projects

design problems

delta wing design

small group design assignment

mark prof lai

prof lai noneprof seah

prof seah middle

human needs