kettle design process

Product DevelopmentThe Electric Kettle Case Study

Tuesday, May 4, 2010

Market Requirements

Volume of boiling water = 2 liters

Kettle weight include water < 3 kg.

Demand of kettle is 2 million/year


Objective of Case Study

Functional RequirementsAutomatically stops boiling when water is boiled

Cordless design

Easy to clean

Handle remains cool and safe to touch



Materials that can be ruled outPolyphenylene oxide (PPO)

maximum operating temp. is 105 degree Celsius

discolor-able due to outdoor exposure

difficult to mass produce (must be blended with polymers)



Materials that can be ruled outPolyethersulphones (PES)

limited exposure to hot water

changes dimension when exposed to moisture



Materials that can be ruled outPolyetheretherketones (PEEK)

high cost

excessive working temperature

limited shaping process - difficult to manufacture



Materials that can be ruled outAluminum (Al)

corrosive prone

require further treatment before processing



Materials that can be ruled outMagnesium (Mg)

corrodes easily

burns if reacted to water, thus coating will be required


Objective of Case StudySketch and dimension of kettle body

Dimension

Half Side view

- overall height : 10.5 cm.

- inner radius: 8.003 cm.

- base thickness: 1 cm.


Objective of Case StudySketch and dimension of kettle body

Sketch



Consider the mechanical properties affected

wear resistance: considering wear between kettle and plate since the two components have to be contacted during its operating life




thermal resistance: we have to consider thermal resistance of the kettle since the body is in direct contact with the boiling water. It is necessary to have a body which will not conduct heat out the the outer shell.




impact resistance: since we do not want the kettle to break when dropped, we should consider the impact resistance of the material used for the kettle body.




electrical insulation: the kettle consist of electrical system for the heating system, thus we should consider the importance of electrical insulators of the kettle




corrosion resistance: many materials can corrode when exposed to moisture, thus we must consider the corrosion of materials used for the kettle


Comparative Cost of Materials


Stiffness of Various Plastics:

(GN/M2) StiffnessPolyamide (PA) 1.25Polypropylene (PP) 0.24Polyacetal (Polyoxymethylenes POM) 0.71Polyphenyleneoxide (PPO) 1.6Polyethersulphone (PES) 2.5Polyethertherketone (PEEK) 2.8


Materials Density (Kg/M3)

Cost per kg (rel. to steel)

Minimum wall thickness (mm)

Volume of material (M3×10-4)

Material cost per casting (rel. to steel)

Steel 7900 1 0.6 4.87 2.32638

Al 2700 2 0.8 4.87 1.052

Mg 1700 15 0.9 4.87 0.74511

PP 910 5 5.6 4.87 2.21585

POM 1200 8 3.8 4.87 4.6752

PPO 1200 7 3.3 4.87 4.0904

PES 1300 20 2.6 4.87 12.662

PEEK 1300 30 2.5 4.87 18.993

PA 1200 9 3.2 4.87 5.2596


Bench Marking for Materials


Criteria Weight (100)

PA PP POM PPO PES PEEK

Wear Resistance 5 2.5 3 3 3.5 4 3.5

High Temperature Resist 15 3 3 4.5 3 3.5 4

Insulator Properties 20 2.5 4 4 3 3 3

Chemical Resistance 5 3 4 4 4 3 3.5

Impact Resistance 5 3 4 3 4 3 4.5

Cost 20 4 5 4 4 2.5 2

Durability 15 3 3.5 3 4 3 3

Ease of Manufacturing 15 3 5 2.5 2 4 3

Total 100 307.5 407.5 360 322.5 317.5 307.5


Material to useFrom the benchmarking table, the most appropriate material for our kettle is PP or Polypropylene.



Choose the material(s) and process(es) for manufacturing the kettle

The material we choose for kettle body is polypropylene (PP). Due to its low cost and ease of manufacturing, we think that this is the most appropriate material to use. Also, the thermal resistance of this material is suitable for such operation as boiling water. The manufacturing process which is the most suitable is blow molding, since the production volume is appropriate. Also the capital cost and tooling cost seems to be the most appropriate.


kettle design process

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