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Material - Process Selection. Polycarbonate? Aluminum? Stainless steel?. Die cast? Forged? Stamped? Molded?. CRS? Nylon 6? Zinc?. Poli, C., Design for Manufacture: a structured approach, 2011, 1 st Ed, Butterworth-Heinmann. Proposed replacement part. Original 5-part assembly.
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Material - Process Selection Polycarbonate? Aluminum? Stainless steel? Die cast? Forged? Stamped? Molded? CRS? Nylon 6? Zinc? Poli, C., Design for Manufacture: a structured approach, 2011, 1st Ed, Butterworth-Heinmann
Proposed replacement part Original 5-part assembly Decisions Decisions Decisions • Question: Should we replace the original 5-part assembly with a single part? • Question: If so -what material should the part be made of? -what process should be used to make the part? • Question: Should we choose the material first? Should we select the process first?
Materials First Approach • Consider application information such as stresses, environment, codes, disposal, etc. • Based on this information, select feasible material classes • Now select associated process types • Now consider application information such as stresses, environment, codes, disposal,etc. • Select feasible process and material
Process First Approach • Consider part information such as size, shape, production volume, etc • Based on this select feasible process types • Select associated materials classes • Now consider application information such as stresses, environment, codes, disposal,etc. • Select feasible process and material
Product Design Process Design Team Marketing Production Control Production Shipping Concurrent Engineernig • Involve Everyone (Team Approach)- from beginning to end / from cradle to grave • Product and process design done simultaneously rather than sequentially
Taxonomy of the kingdom of materials, process and their attributes
Preliminary Process and Material Selection - Wrought Processes
Preliminary Process and Material Selection - Casting Processes
Preliminary Process and Material Selection - PlasticProcesses
Level I: Metals vs Plastics Can be formed into almost any shape with no finishing Resist corrosion better Better insulators Plastics less dense Less costly
Level I: Metals vs Plastics - continued Metals have better mechanical properties Better thermal and electrical conductivity; higher temp. capabilities Can be processed by a fast process - stamping!
Complex shapes Level II - Cast vs Wrought • To choose must know: - How easily can the material be shaped? - Mechanical and physical properties. - Easy to cast - Difficult to forge Castings:- small voids- pockets of impurities (inclusions)- large grain structure- poorer mechanical properties Forgings:- start with cast billet that was then rolled/drawn/extruded - squeeze between die halves - formed using 2-3 stages- better mechanical properties
Level II - Cast vs Wrought - continued • Mechanical properties (ductility and strength) are improved by wrought processes. • For alloys of the same composition - wrought better than cast • By choice of composition - high carbon steel casting better properties than low carbon steel sheet • Specify desired mechanical properties- producer adjusts composition.
Level II - Cast vs Wrought - continued • Consider casting process/alloy - complex/hollow shapes - large parts - when several parts can be combined • Consider wrought alloys/processes - simple geometry - fast process such as stamping or extrusion can be used
Level II- Thermoplastic vs Thermoset Thermoplastics faster and easier to process Thermosets have higher flexural modulus => more rigid
Level III: Ferrous vs Non-ferrous Ferrous more resistant to corrosion Easier to fabricate due to lower tensile and yield strengths Better thermal and electrical conductors Lighter in weight Non-ferrous better mechanical properties; stiffer
Level III: Steels Strength, hardness, wear resistance increases As carbon content increases, ductility (%elongation) decreases structural shapes, forgings,plates hammers, dies, tool bits Resist corrosion, high strength
Nylon has low coefficient of friction => used for bearings, bushings, gears, etc Level III: Plastics Polycarbonate has highest impact resistance Plastics with fillers have improved mechanical properties, electrical and thermal conductivities and cost more
Die cast: aluminum A380.0 Injection molded: polycarbonate Stamped: CRS ASTM A606 Level IV • At the parametric stage of design we pick the specific alloy or resin