2.008-spring-2004S.Kim
2.008 Design & Manufacturing
II
Spring 2004
Assembly & Joining
1
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Dexter’s Plastic Can
-cool ?
-gas leakage ?
-recycling?
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A 2002 Yo-Yo vs. a free gift
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Guidelines to Assembly Design
Minimize parts
Design assembly process in a layered fashion
Consider ease of part handling
Utilize optimum attachment methods
Consider ease of alignment and insertion
Avoid design features that require adjustments
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Manufacturing
MarketResearch
ConceptualDesign
Factory,Systems &Enterprise
UnitManufacturing
Processes
Contributions on the final cost?
•Welding•Bolting•Bonding•Soldering
•Machining•Injection molding•Casting•Stamping•Chemical vapor deposition
Assembly andJoining
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Cost of Design Changes
J.Chun and http://www.lboro.ac.uk/departments/mm/research/product-
realisation/res_int/ipps/dfa1.htm
time
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Typical Cost Breakdown
Selling Price
Engineering14%
R&D5%
Admin, sales24%
Manufacturing38%
Manufacturing Costs
PlantMachinery
12%
Indirect labor26%
Direct labor12%
Parts, Material
50%
Profit19%
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Assembly business
M. Culpepper
Industry % Workers in Assembly
Automobile
Aircraft
Telephone & Telegraph
Farm Machinery
Home appliances
Two-wheel vehicles
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Optical Connectors
MT connector
Alignment errors
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Initial Quality Study
Problems experienced after 90 days of ownership per 100 vehicles
IQS:
0 to 100, 100 to 200, 200 and over
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The automobile industry, 1980’s
Sullivan, 1986
Problem “fine and fix”
(US company)
Problem prevention(Japanese company)
Product Launch
SOP
Months Relative to Product Launch
Des
ign
Ch
ang
es p
er W
eek
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Good DesignDFMA (Design for Mfg. & Assembly)
Simplicity for both human operators and robotsEven Kids can do.
http://order.tupperware.com:8080/coe-images/items/10044822000_detail.jpg
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DFA guide
Simplicity is the best DFA. Minimize part numbers, operations, simplify assembly sequence (steps) and set-ups Standardize components, use suppliable common parts Minimize assembly directions (layered structure)
N. Suh
Figure 3.3. Can and bottle opener. This bottle/can opener satisfies two FRs: (1) opens cans, and (2) opens bottles. If the requirement is not to perform these two functions simul-taneously, then this physically integrated device satisfies two independent FRs.
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DFA guide (cont.)
Modular design, product families, assembly friendiness Use symmetrical parts Physical integration Minimize sharp, delicate, flexible, slippery part Relax tolerances on non-critical locations. Approachable, line of sight
Size Fragile/Sharp
Slippery/Flexible
Symmetry
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DFA Guide (cont.)
Material for DFA, avoid flexible components Concurrent engineering
Design for disassembly (recycling, repair, retrofit)
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DFMA
Hitachi assemblability evaluation method Lucas DFA Boothroyd-Dewhurst DFA (BD)
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Design for Assembly
Number of parts
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Pneumatic Piston Sub-Assembly
T. Gutowski
screw
spring
piston
cover
piston stop
main block
Redesigned
1 – snap on cover and stop (plastic)
2 – spring(steel)
3 – piston(aluminum)
4 – main block(plastic)
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DFA: Examples
Pa rt ca n jam when Tape ring the hol einserted into hole . facilitates part insertion.
Alignment
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DFA for Automation: Examples
Parts are difficult Chamfers assist to assemble . assem bly.
Parts are difficult Changing part geometry to align properly; allows it to be aligned properly jamming can occur. before it is released.
Kalpakjian, Benhabib
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Assembly automation
Challenges
Parts Feeding
Sorting
Orienting
Pick-and-place
Assembly
PCB assembly?
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Non-vibratory Feeding
Groove
Hopper
Rotation axis
Rotary mechanism with multiple blades
Inclined discharge rail
B. Benhabib
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Vibratory Parts Feeding
B. Benhabib
Track
Bowl
Electromagnet
Outlet
Leaf springs
Base
TranslationalvibrationTorsiona
l vibratio
n
Vibratory Feeding -orientation
Second attachment(rejects c and d ) First
attachment(rejects a and b )
Third attachment(orients e and f )
Side view
Top view
Discharge hole
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Magnetic Parts Feeding
Parts picked up by magnets
Delivery chute
Magnets Parts
Stationary hopper
DFA for Transporting
Flat ends prevent jamming.
Non-functional peg prevents jamming.
Wider edge surface prevents overlap.
B. Benhabib 2.008-spring-2004 S.Kim 26
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Automated Assembly
Transfer Transfer lines Conveyor Automated Guided Vehicle
PositionerAssembly Operations
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Transfer Lines
Piston
Stop
Work carriers Fixed rail
Step
Transfer rail
Slide
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Rotary Assembly Transfer
B. Benhabib
Positioningunit Riveter
Adhesive-bond applicator
Inspection station
Completed pieces
Vibratory bowl
Feedtrack
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AGV
Pallet load / unload mechanism
Workpiece
Pallet
Safeguards against collision
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Pick & Place Positioner
Linear actuator
Rotary actuator
Gripper
Fixed-length arm
Rotary actuator
Fixed base
Shoulder swivel
Robot
Hydraulic/electric power unit
Elbow extension
Arm
Robot controller
Arm sweep
Pitch
Yaw
Wrist
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Robots: Components
Manipulator positioning power stiffness control
End effector tooling
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Robots: Applications
3 D’s (Dull, Dirty,
Dangerous)
3 H’s (Hot, Heavy,
Hazardous)
Materials handling
Spray painting
Spot welding
Arc welding
Assembly
J. Chun
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Good Design Principles: DFM Assembly
Design parts to be self-locating and self-aligning Error-proof parts to make incorrect assembly impossible Minimize the number of parts. Minimize the number and variety tools for assembly Minimize the number of axes of insertion Ensure clear vision and access for all assembly operations Minimize the number and complexity of adjustments Eliminate the need to hold down, clamp or fixture parts
Eliminate special assembly tools
Alignment
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What assembly process to choose?
Reasons to avoid assembly
Reasons that justify assembly
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Workholding
Immobilization of a workpiece for machining or assembly
Jigs: locating and holding workpiece, guiding tools Fixtures: locating and holding
Provide maximum accuracy and ease of mounting Datum
3-2-1 rule of locating
6 dof, (Dx,Dy,Dz) and (Rx,Ry,Rz) 3 support Points (1, 2 and 3) eliminate (Rx and Ry) and (-Dz); 2 points (4 and 5) eliminate (Rz) and (- Dx); and, 1 point (6) eliminates (-Dy). Push or clamp 3 directions, x,y,z.
Direction of resultant clamping force
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