1. ME 437 - Session #6 More PDS / Materials / Bad designs
PDS due on Monday
Stay with the suggested format
Cover all items - Use NA, Not known, or None when applicable
Patent search sites:
Patent Number: D
(Darren!?)
More PDS / Materials / Bad designs

2. ME 437 - Session #6 Auto bike rack Home bike rack Cat/Dog Feeder
Eric & Merrily
Dave & Serin
Mark & Kareem
Home bike rack
Werner & Albert
Scott, Jim, Darren
Mahesh & Chan
Cat/Dog Feeder
Clint & Brett
Tony & Bruce
Jim & Jeff
Dana
Tavis
Envelope
Shane & Bill
Ceicel, Ben, Brial

3. Project Timetable

4. Deliverables Conceptual designs Include at least 3 different ideas.
Avoid close variations as much as possible.
Each concept should be clearly shown.
Use hand-drawn orthographic-like drawings with correct proportions.
Show details on separate pages if necessary.
Number each major component of the assembly
Motor, electronic control box, gear box

5. Conceptual Designs

6. Deliverables Final Report Includes Final PDS Final design description
Assembly drawing.
A description of each component in the assembly:
Drawings of designed components.
Complete description of off-the-shelf components including model and brand.
Instructions for product assembly.
Operations, maintenance, and safety manuals.

7. Final Report Final Design Supporting information
Other conceptual designs considered.
Decision methods used.
All major decisions made and reasons for them.
Relate decisions to PDS
Include cost and manufacturing concerns
Areas where possible improvements can be made.

8. Materail Selection Plain carbon steels have very poor hardenability.
Cold finished steels (1006 to 1050) can come in various tempers (hard to skin rolled). They can be strengthened up to 100% with cold working.
Cold finished parts are stronger, have better surface finish, are more dimensionally accurate. But, they have less ductility, cost more, are dimensionally less stable in machining, and loose their strength if welded.
High sulfur steels are ideal for machining (AISI 1112) as the chips break up easily. High sulfur content, however, causes weld cracking.

9. Material Selection Alloy steels
AISI 4340 or 4140 (Through hardening grades): Have excellent strength and toughness. Available in most forms in hot rolled form. Designed for high hardenability. Best suited to high stress machine parts - gears, cams, shafting, piston rods, bolts, dies, keys, bending rolls. They can be finish machined but can not be easily welded without special precautions.
AISI 8620 or 9310 (carburizing grades): These steels are designed for case hardening requirements. Deep cases can be created and hardened using carburizing. Used when high wear resistance is required. Suitable for gears, racks, cams, and sliding surfaces.

10. Alloy Steels High Strength Low Alloy Steels (HSLA)
Used for Structural applications
Stronger than plain carbon steels
Not heat treatable
Corrosion resistant (not as much as stainless steel)
Good weldability (low carbon content)
Good formability
Applications: structural forms, bars, plates.
ASTM A36 (most popular), A242

11. Alloy Steels Ultra-strength steels
High strength and reasonable toughness.
Used for heavily loaded machine parts.
4340 and 4140 are most common
Hard to weld but machinable
18% nickel maraging steel
Very high strength ( ksi)
Good weldability
Very expensive

12. Example
Suppose a designer has created a drawing for a shaft of a hypothetical device. The list of operational conditions have been determined as follows:
1.25” diameters are to fit ball bearings
The shaft is subjected to maximum shear stress of 10 ksi
There is possibility of moderate shock load
Small end must resist damage from frequent removal of a keyed gear.
There are no inertial requirements.
Surface roughness to be 32 micro inches max.
Diameters must be concentric to inch.

13. Example
Based on the operational requirements, time constraint, and cost, the following selection factors have been established:
Hardness of at least 30 HRC (285 HB)
Fatigue strength of 30 ksi
Impact strength must be high
Stiffness must be high
The part must not rust in 50% RH room air.
Must be dimensionally stable.
Parts are needed in one week.
Three units are required.
Expected service life is 5 years

14. Example [From Budinski]

15. Solution ideas What kind of material Must be hardenable to 30 HRC
Metal?
Plastic? Low stiffness
Ceramic? Low impact strength
Composites?
Must be hardenable to 30 HRC
Hardenable steels 1050 or 4340/4140
High fatigue strength
AISI 4340 or 4140
Must be surface treated (nickel plating)

16. Cast Irons Grey cast iron (ASTM A 48 grades 20-60)
Easy to cast (excellent fluidity)
Low cost
Low toughness, brittle, no shock resistance
High compressive strength
Not appropriate for parts stresses in tension.
Low to medium tensile strength
Excellent machinability
Superb vibration damping property
Not easily weldable
Low stiffness (30 to 60% of steel)

17. Cast Irons Gray cast iron Ductile iron (ASTM 536, grade 5 [60-40-18])
Excellent metal-on-metal wear resistance
Good corrosion resistance in all media
Ductile iron (ASTM 536, grade 5 [ ])
Easy to cast/Low cost.
Much better toughness than gray iron.
Stiffness is about 70% of steel
Yield strengths range from 40 o 90 ksi
Similar to gray cast iron in other properties

18. Aluminum Alloys General properties Lightness: 1/3 of steel
Good thermal and electrical conductivity
High strength/weight ratio
Weldable (most alloys)
Atmospheric corrosion resistance (will not rust)
Excellent machinability
Can be die case
Good formability
Non-magnetic
Non-toxic (pots and pans - 25% of all usage)