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

B. Benhabib 2.008-spring-2004 S.Kim 38