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2.875 Mechanical Assembly and Its Role in Product Design

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Presentation on theme: "2.875 Mechanical Assembly and Its Role in Product Design"— Presentation transcript:

1 2.875 Mechanical Assembly and Its Role in Product Design
Pencil Sharpener Presentation#1 November 14, 2001 Hernan Joglar John Sharkey

2 Presentation Contents
Product Description Company Background CAD Exploded view Parts and Material List Photo of Product Disassembly Product Structural Decomposition Major Sub-Assemblies Critical Mates and Clearances Gearbox Key Characteristics and Datum Flow Chain Assembly liaison diagram Assembly Time Analysis Example Assembly Process Fixtures and Special Tooling Potential Problems and Risks Suggested Assembly Improvements Backups DFA Gross Motions - Product Structural Decomposition DFA Fine Motions - Part Liaisons and Mates Related Product Line

3 Boston Stapler Product Description
Battery Operated Pencil Sharpener: Model #16750 (black) Referred to as a “razor spiral cutter” model Operation activated by axial force of pencil insertion Safety lockout feature prevents operation without receptacle Features 1 year warranty No replaceable parts, Hunt simply replaces defective units Product Assembly Specifications: 29 identified parts, comprising 7 sub-assemblies 35 assembly features and liaisons Physical dimensions: 4.75” x 3.00” x 2.25” at 6.1 ounce weight Popular with graphic artists and designers provides clean, sharp pencil points for a wide range of pencil types, including composite pencils Approximately 250,000 units sold last year Distributed through all major office supply retail stores Staples, Office Depot, Wal-Mart, Target, etc Typically sells for around $5.00

4 Hunt Manufacturing Corporation
Founded in 1899 by George Bartol Went public in 1982 after a series of expansions and acquisitions. Corporate headquarters in Statesville, NC Donald L. Thompson became president and CEO in 1996 Product design center located in Statesville, NC Outsources most manufacturing within the United States Boston Series of pencil sharpeners manufactured in China 1300 employees nationwide Sales revenue of $286M in 2000, 1.6% increase over 1999 Main product lines is graphics equipment and office supplies A global leader in the pencil-sharpener market Boston family of pencil sharpeners and staplers accounts for 40% of company sales Other significant products lines include: Exacto razor blades Conte crayons and pastels Bienfang paper, painter markers, foam boards and laminates Seal imaging equipment

5 CAD Exploded View [ Model developed using Autodesk Inventer Version 3.0 ]

6 Parts and Material List

7 Photo of Product Disassembly
9 14 24 15 25 5 8 4 12 11 23 2 7 21 11 20 17 18 19 1 3 26 27 28 29 16

8 Product Structural Decomposition
Complete Assembly Pencil guide Base screws Motor Gearbox Bat. Comp. screws Shavings receptacle Battery Compartment Sharpener case Base Sharpener base Bat. Comp. housing Black wire Gearbox cover screw Rubber foot Gearbox housing Electric motor Bat. Comp. contacts Output gear Safety lever Battery Comp. cover Bat. install. guide Intermediate gear Lubrication Contacts battery Comp. cover Driven gear Gearbox cover Battery Comp. cover Cutter Unit Gearbox cover contacts Rubber foot Red wire Blade nut and bolt General Assembly Sub- Assembly Part Blue wire Blade Gearbox cover Blade holder

9 Major Sub-Assemblies Gearbox cover Sub-Assembly
Input contact Intermediate contact Edge Output contact Safety lever pin Motor rim Gearbox Cover Output gear Driven gear Motor Intermediate gear Gearbox housing Gearbox cover Sub-Assembly Motor Gearbox Sub-Assembly Mating features Electric in-out contacts Red and black electric wires Electric contact rivets Blade Blade holder Bolt Nut Cutter Unit Sub-Assembly Battery Compartment Sub-Assembly

10 Critical Mate and Clearance Ratio #1
Slots Shaver Receptacle to Shaver Case   Rims

11 Critical Mate and Clearance Ratio #2
Base to Sharpener Case Edge Interface Holes Slot along edge Rim along edge Pegs Rim Sliding surfaces Slot Note: Clearance ratio requires Gearbox and battery compartment sub-assemblies to be inserted.

12 Critical Mate and Clearance Ratio #3
Slots Rim and snap fit Rims Slot

13 Gearbox DFC and Key Characteristics
3 5 6 2 4 Gear housing cover Driven gear block Intermediate gear block Output gear block Top lateral stopping peg Top central stopping peg Motor Location pegs Gear housing Motor gear Driven gear input pinion Driven gear output pinion Driven gear stand 1 Z 13 17 10 18 14 9 8 11 X Driven gear pin Intermediate gear input pinion Intermediate gear output pinion Intermediate gear stand and hole Intermediate gear pin Output gear Output gear stand Bottom lateral stopping peg Bottom central stopping peg Top part of motor compartment in gear housing Hole in gear housing for motor location Motor 12 15 16 19 7 20 21 22 24 23

14

15 Simplified Gearbox DFC: Driven to Intermediate Gear
Driven gear pin Driven gear stand Intermediate gear pin Intermediate gear stand Tangency KC Intermediate gear Gear hole Bottom surface Driven gear Pitch circle driven gear output pinion Gear Housing Top surface Top Stopping pegs and contact end Rim Edges Bottom stopping pegs and contact surface Driven gear block Intermediate gear block Co-planarity KC Bottom surface input pinion Top surface driven gear input pinion Pitch circle input pinion Pitch circle of driven gear Pitch circle of intermediate gear Bottom Stopping pegs Rim Gears top surfaces Gear Housing cover Gear pins Gear stands

16 Pencil Sharpener Liaison Diagram and Fasteners Classification
Liaisons Using Threaded Features Screws Nut & Bolt Other mates c29 Permanent Liaisons Rivets Adhesive Soldering c27 p17 c30 c28 p16 C36

17 Assembly Time Analysis
Throughput requirement based on production volume 250, workdays/year = 1000 units/day hours/day = 125 units/hour = 2.08 mins/unit Assembly time per Boothroyd Handling and Insertion Times Handling Time per unit = (sec/unit) Location Time per unit = (sec/unit) Reversible Fastening Time per unit = (sec/unit) Irreversible Fastening Time per unit = (sec/unit) Total predicted assembly time = (sec/unit) Note: does not include inspection and test time Measured Handling, Location and Reversible Fastening Times Test# sec - Test# sec Test#2 222 sec - Test# sec Test#3 198 sec Assembly Efficiency Three “un-necessary parts: Sharpener case, paper guide, and pencil guide 207.18 (sec)

18 Example Assembly Process
SA 7 Cutter Unit Assy SA 7 Cutter Unit Inspect 18.25 sec 5 sec SA5a Gearbox Assy Solder Test SA5 Motor/Gearbox Assy SA6 Gearbox Cover Assy SA 6 Gearbox Cover Inspect 48.06 sec 5 sec sec SA5 Battery Comp. Assy SA 5 Battery Comp. Inspect SA1 Final Assy SA1 Final Inspect 19.62 sec 5 sec sec 20 sec SA3 Battery Cover Assy SA 3 Battery Cover Inspect SA2 Base Assy Package & Ship 19.62 sec 5 sec 33.5 sec 30 sec Note: Test, inspection and packaging times are SWAGS

19 Fixtures and Special Tooling
Riveting fixture. or special tooling, for battery compartment Riveting fixture, or special tooling, for gearbox cover Bending fixture for gearbox cover electrical contacts Bending fixture for battery cover electrical contacts Bending fixture for battery compartment electrical contacts (nice to have) Soldering station and fixture for electric motor (black and blue leads) Soldering station and fixture for battery compartment (black and red leads) Standard Tools and Special Tooling Heat stake tooling for battery compartment electrical contacts Magnetic Phillips head screwdriver (4” length) for battery compartment screw Small wrench, or pliers, for blade screw and nut Wire strippers (22 gage) Wire tinning and pre-form bending Soldering station for gearbox cover Electrical test station for operation of motor/gearbox sub-assembly Lubrication dispenser gun

20 Potential Problems and Risk Areas
Description Probability Impact Personnel injury from razor blade Med High Reversed motor polarity wiring (black on +) High High Reversed battery compartment wiring (red on right) High High Solder joint or wire breakage during gearbox insertion Low High Solder joint or wire breakage during motor insertion Low High Motor pinion clearance thru gearbox hole High Med Loss of motor location during final assembly High Med Improper location of battery compartment on gearbox Med Med Part damage from shaver receptacle insertion (snap fit) Med Med

21 Suggested Design Improvements
Description Impact Reversed motor polarity wiring (black on +) - Use wire connector instead of solder joint Med Reversed battery compartment wiring (red on right) - Imprint wiring polarity on battery compartment injection mold High Solder joint or wire breakage during gearbox insertion - Use wire connector instead of solder joint Med Solder joint or wire breakage during motor insertion Motor pinion clearance thru gearbox hole - Reduce and control gearbox manufacturing variance Med Loss of motor location during final assembly - Include snap/fit feature between battery compartment and gearbox High Improper location of battery compartment on gearbox - Use wire connectors instead of solder joint Med Part damage during shaver receptacle insertion (snap fit) - Training, coupled with control of manufacturing variations Low

22 Backups Part Handling: Gross Motion ( 2 slides)
Part Insertion: Fine Motions ( 2 slides) Part Liaisons and Mates Related Product Lines Product Structural Decomposition

23 Part Handling: Gross Motion

24 Part Handling: Gross Motion (con’t)

25 Part Insertion: Fine Motion

26 Part Insertion: Fine Motion (con’t)

27 Part Handling: Gross Motion (con’t)

28 Part Liaisons and Mates in Pencil Sharpener

29 Part Liaisons and Mates in Pencil Sharpener (cont.)

30 Related Product Line Item # 20052504 , Style # 001799 $21.99 each
Boston Electric Auto-Reset Pencil Sharpener Item # , Style # $ each New exclusive design offers modern styling with proven Boston quality, Auto-Reset thermal overload, solid steel cutter and nonskid rubber feet. Boston Powerhouse Electric Sharpener Item # , Style # $21.99 each This new powerful, heavy-duty commercial grade sharpener uses X-Acto precision steel cutters and a Pencil-Saver feature to sharpen to a perfect point. Features auto-reset and built-in pencil holder. Boston Electric Standup Pencil Sharpener Item # , Style # $19.99 each Features X-ACTO precision cutters for longer life. Unique stand up design stands out on your desk. 2 year warranty. Boston Battery Pencil Sharpener Item # , Style # $5.99 each Sleek, compact design with powerful razor blade sharpening mechanism. Safety features-Auto on-off switch; sharpener doesn't operate if receptacle isn't secured. Runs on 4 AA batteries (not included).

31 Product Structural Decomposition
sa5 sa7 sa6 sa4 sa3 p3 p4 p2 sa2 p6 p5 p15 p16 p17 p18 p19 p20 p21 p23 p24 p25 p27 p28 p22 p26 p29 p8 p9 p10 p1 p14 sa1 p7 p11 p13


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