1

Pencil Sharpener Report#4Assembly Workstation

Analysis

November 21, 2001Hernan JoglarJohn Sharkey

2.875Mechanical Assembly and its Role in Product Development

2

Report Contents

1. Introduction

2. Cycle Time Analysis

3. Candidate Assembly Process Flow

4. Part And Subassembly Inflow and Outflow

5. Workstation Layout

6. Motion Analysis for People and Equipment

7. Inspection and Test Requirements

8. Gannt Chart Analysis of Assembly Process

9. Estimated Cost for Workstation Purchase and Installation

10. Estimated Cost of Unit Assembly

11. Appendices• Pencil Sharpener Exploded View

• Pencil Sharpener Structural Decomposition

• Pencil Sharpener Disassembly Photo

• Pencil Sharpener Indentured Part List

• Pencil Sharpener Parts & Material List

3

Introduction

• Purpose is to analyze assembly workflow and workstation requirements

• Approach was to modify the assembly flow presented in the Project Report#3 as the baseline for analyzing workflow, workstation and timing requirements– Added an additional final functional test of completed assembly

– No attempt made at optimized work flow

– Alternate variations considered for inspection and test analysis, but not presented in this report

• Method assumes manual assembly process throughout

• Approach assumes all electrical contacts are pre-formed by manufacturing, or supplier, prior to assembly operations

4

• Throughput requirement based on production volume– 250,000 units/year @ 250 workdays/year = 1000 units/day– 1000 units/day @ 8 hours/day = 125 units/hour = 2.08 mins/unit

• Assembly time per Boothroyd Handling and Insertion Times– Handling Time per unit = 106.98 (sec/unit)– Location Time per unit = 47.50 (sec/unit)– Reversible Fastening Time per unit = 54.20 (sec/unit)– Irreversible Fastening Time per unit = 121.00 (sec/unit)– Total predicted assembly time = 329.68 (sec/unit)

Note: does not include inspection and test time

• Measured Times for Handling, Location and Reversible Fasteners(does not include soldering, riveting, lubrication, or other irreversible fasteners)

– Test#1 309 sec - Test#4 169 sec– Test#2 222 sec - Test#5 153 sec– Test#3 198 sec

207.18 (sec)

Cycle Time Analysis

5

SA5a Gearbox

Assy

SA5b Gearbox

Solder

SA5c Gearbox

Test

SA5

Motor/Gearbox Assy

87.30 + 30 sec

Baseline Assembly Process Flow

SA 7Cutter Unit

Assy

SA 7Cutter Unit

Inspect

SA6Gearbox Cover

Assy

SA 6Gearbox Cover

Inspect

SA4 Battery Comp.

Assy

SA 4Battery Comp.

Inspect

SA3 Battery Cover

Assy

SA 3Battery Cover

Inspect

SA2Base Assy

SA1Final Assy

SA1Final Test

Package& Ship

18.25 sec

48.06 sec

19.62 sec

19.62 sec

5 sec

5 sec

5 sec

5 sec 33.5 sec

101.83 sec

30 sec

30 secNote: Test, inspection and packaging times are SWAGS

SA1Final Test

20 sec

6

Part And Subassembly Inflow and OutflowStation Sub-station Part # In-flow Sub- Assembly

In-flowSub- Assembly

Out-flowFunction

A 1 11,12 SA4 Riveting contacts to battery compartmentA 2 23,24,25,26 SA6 Riveting contacts to gearbox cover and

soldering red and blue wires A 3 27,28,29 SA7 Fastening blade to blade holder by with

nut and boltB 1 8,9,10 SA3 Rivetting contacts to battery

compartment cover and glueing rubber foot

B 2 5,6 SA2 Glueing rubber foot to sharpener base.C 1 14,15,16,17,

18,19,20,21, 22

SA6,SA7 SA5 Installing gears, safety lever, lubrication in the gearbox housing and attaching the gear housing cover with its screw.

C 2 20 SA4 SA5,SA4 soldering black and blue wire to electric motor, mating sa5 and sa6 together and soldering red and black wires to battery compartment housing contacts

C 3 SA5,SA4 Testing electric circuit in motor/gearbox subassembly

D 1 1,2,3,4,7,13 SA2,SA3,SA4, SA5

SA1 Mating sa4 and sa5 inside sharpener housing, inserting battery installation paper guide in battery compartment, installing sharpener base and attaching it to sharpener base with its screws, and installing battery housing cover.

D 2 SA1 SA1 Testing sharpener functioning

E SA1 SA1

Putting the sharpener with the instruction manual in plastic, putting everything in a box and closing the box

7

Workstation Layout

Parts and subassemblies storage shelf

Tools and fixtures storage cabinet

Transportation belt

Part & subassembly transportation tray

Packaged products carrying cart

Parts

Part StorageArea No 3

Tool &Fixturestorage Finished sharpener transportation tray

Tool transportation buckets

Trash bucket

Worker spinning seat

Storage Space

Part StorageAreaNo 1

Part StorageAreaNo 2

2

A

1 3

Parts

PartsParts

2

C

1 3

PartsPartsPar

ts

B

Parts Parts

1 2

D

Parts Parts

1 2

E

Packaging M

aterial

12

Finished &PackagedProducts

Storage Area

Parts

Parts

8

Layout Explanation• For layout design, this team has sought to group functions in such a way

that floor space is saved without loosing flexibility. Functions that require similar activities and/or tooling have been grouped. Flexibility is accomplished by grouping activities that have similar duration and may be performed in parallel with those being carried out in other workstations. Estimated floor space is 4000 square ft (80’ x 50’).

• In workstation A, for instance, functions functions that imply riveting have been grouped, so that workers can help each other if one of them is too slow.

• Workstation B groups gluing activities and workstation E groups packaging activities.

• The way tasks have been grouped gives management the possibility of changing the number of workers in each station as transitory situations may require it. This variations should not affect the assembly process

• The layout has also been designed in such a way that there is a minimum of handlers and they stay at a certain distance of the workers assembling the product, that’s why both storage areas are at the extremes.

9

Motion Analysis for People and Equipment

• Every worker has the parts, fixtures and tools he/she needs at an arm length distance or so.

• Every worker sits on a wheeled spinning chair for ease of movement.• Parts are moved by a handler from the storage area to the distribution

belt in trays.• Part trays are picked up from distribution belt by workers at stations

and stored in shelves.• When necessary parts and/or subassemblies are passed on directly

between workers (station C).• Subassemblies are moved from station to station on by means of

transportation belt.• Tools, fixtures, and materials are moved by handler from storage area

to the distribution belt in buckets. These buckets are picked up by workers in stations.

• Finished products are moved from packaging station (Station E) to finished product storage in carrying carts by a handler.

10

Inspection and Test Requirements• Unaided Visual Inspection Requirements

– Cutter Unit (SA7) inspection to confirm blade installation and alignment

– Gearbox Cover (SA6) inspection to confirm proper installation and heat staking of of electrical contacts, and correct soldering, location and orientation of red and blue wires

– Battery Compartment (SA4) inspection to confirm proper installation and riveting of electrical contacts

– Battery Compartment Cover (SA3) inspection to confirm proper installation and riveting of electrical contacts

– Final assembly (SA1) inspection to confirm aesthetic appearance (lack of nicks, scratches, smudges), mechanical integrity (no loose parts)

• Baseline Electrical and Functional Tests– Motor/Gearbox mechanical function test, and electrical continuity tests, to confirm

proper operation (full range of motion w/out binding) of safety lever switch, motor actuation switch, and ability to manually back-drive the geartrain

– Final electrical function test required additional special equipment:• Re-chargeable battery-pack unit

• Plastic pencil “simulator” tool which rotates freely inside of a handheld bearing unit

• Assembly and test flow requires removal and re-installation of battery compartment cover, to verify proper end-to-end operation

11

Gant Chart of Baseline Assembly Process

Cutter Unit Assy

Cutter Unit Inspect

Gearbox Cover Assy

Gearbox Cover Inspect

Motor/Gearbox Assy

Motor/Gearbox Test & Inspect

Battery Compartment Assy

Battery Compartment Inspect

Battery Comp Cover Assy

Base Assembly

Battery Comp Cover Inspect

Final Assy

Final Test

Final Inspect

Package & Ship

0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00

0 30 60 90 120 150 180 210 240 270 300 330 360 390

18.25

5

48.06

5

87.30

30

19.62

5

19.62

5

33.5

101.83

30

20

30

Time (sec)

Time (min)

12

Estimated Cost for Workstation Purchase and Installation

• Overall Cost Summary $20,955– Workstation equipment $16,660

– Assembly fixtures $2200

– Standard tools and special tooling $2095

• Workstation Equipment $16,660– Work tables 12 ea @ $250 = $3000

– Part bins 12 ea @ $50 = $600

– Spinning seats 12 ea @ $150 = $1800

– Transportation buckets 2 ea @ $50 = $100

– Part transportation trays 5 ea @ $50 = $250

– Packaged product carry carts 2 ea @ $250 $500

– Finished sharpener trays 4 ea @ $50 = $200

– Trash buckets 7 ea @ $30 = $210

– Conveyor belt ( 30’ x 6 ‘) 1 ea @ $10,000 = $10,000

13

Fixtures and Special ToolingFixtures $2200• Riveting fixture for battery compartment $750• Riveting fixture, or special tooling, for gearbox cover $750• Soldering station and fixture for electric motor (black and blue leads) $350• Soldering station and fixture for battery compartment (black and red leads) $350

Standard Tools and Special Tooling $2095• Heat stake tooling for battery compartment electrical contacts $350• Magnetic Phillips head screwdriver (4” length) $25• Small wrench, or pliers, for blade screw and nut $10• Wire strippers (22 gage) $10• Wire tinning and pre-form bending $10• Soldering station for gearbox cover $350• Electrical test station for operation of motor/gearbox sub-assembly $500• Lubrication dispenser gun $150• Electrical test station for final functional test $500• Plastic pencil simulator with bearing holder $200• Hand rivet tool $75• Re-chargeable battery pack $50

14

Estimated Cost of Unit Assembly • Labor rates for assembly in China based on average CY200 hourly

compensation cost for production workers, as reported by the U.S. Bureau of Labor Statistics (see Chart 1 below)

• Using 405 seconds for total labor ( 330 sec assembly time plus 75 sec test and inspection) per completed unit, assembly costs for various countries are shown in the table below:

Country

Average Hourly Wage ($)

Unit Assembly Cost ($)

United States $19.86 $2.23

Mexico $2.46 $0.28

Taiwan $5.98 $0.67

Hong Kong $5.53 $0.62

Singapore $7.42 $0.83

15

Appendices

• Pencil Sharpener Exploded View

• Pencil Sharpener Structural Decomposition

• Pencil Sharpener Disassembly Photo

• Pencil Sharpener Indentured Parts List

• Pencil Sharpener Parts & Material List

16

CAD Exploded View

[ Model developed using Autodesk Inventer Version 3.0 ]

17

Complete Assembly

Battery Compartment

BaseMotor GearboxBase screwsPencil guide Bat. Comp.screws

Shavings receptacle

Sharpener case

Bat. Comp.housing

Bat. Comp.contacts

Bat. install.guide

Sharpener base

Rubber foot

Battery Comp. cover

Contacts battery Comp. cover

Battery Comp. cover

Rubber foot

Black wire

Gearbox housing

Output gear

Intermediategear

Driven gear

Gearbox cover screw

Electric motor

Safety lever

Lubrication

Cutter Unit

Gearbox cover

Blade nutand bolt

Blade

Blade holderGearbox cover

Gearbox covercontacts

Red wire

Blue wire General Assembly

Sub- Assembly

Part

Product Structural Decomposition

18

Photo of Product Disassembly8

11

2

4

7

20

26

5

21

16 1817 119 27 28 29

1524

23

11

3

14

12

25

9

Pencil sharpener parts numbered as in the Part List

19

P/N Part Name Qty Material Description1 Base Screws 2 Self-threading steel screw2 Pencil guide 1 Injection molded plastic3 Battery compartment screw 1 Self-threading steel screw4 Shavings receptacle 1 Injection molded plastic5 Sharpener base 1 Injection molded plastic6 Rubber foot (Underneath of base) 1 black rubber7 Sharpener case 1 Injection molded plastic8 Contacts on battery compartment cover 2 stainless steel contacts with plastic rivets9 Battery compartment cover 1 Injection molded plastic10 Rubber foot (Underneath of battery comp. cover) 1 black rubber11 Battery Compartment housing 1 Injection molded plastic12 Contacts and rivets on battery compartment 3 stainless steel contacts and brass rivets13 Battery installation paper guide 1 white paper with black graphic print14 Blue wire 1 22 gage aluminum braid wire15 Gearbox housing 1 Injection molded plastic16 Output Gear 1 Injection molded plastic17 Intermediate Gear 1 Injection molded plastic18 Driven Gear 1 Injection molded plastic19 Gearbox cover screw 1 Self-threading steel screw20 Electric motor 1 Brush commutated DC permament magnet motor21 Safety lever 1 Injection molded plastic22 Lubrication 1 red petroleum jelly on gears and motor23 Contacts and rivets on gear housing cover 3 stainless steel contacts and brass rivets24 Red wire 1 22 gage aluminum braid wire25 Black wire 1 22 gage aluminum braid wire26 Gearbox cover 1 Injection molded plastic27 Blade screw and nut 1 Machine screw and hex nut 28 Blade 1 Stainless steel razor blade29 Blade holder 1 Injection molded plastic

Parts and Material List

20

Subassbly. Part # Part Subassembly NameSA1 Complete Asembly

1 Base Screws2 Pencil guide3 Battery compartment screw4 Shavings receptacle7 Sharpener case

SA2 Base Subassembly5 Sharpener base 6 Rubber foot (Underneath of base)

SA3 Battery Compartment Cover Subassembly8 Contacts on battery compartment cover9 Battery compartment cover10 Rubber foot (Underneath of battery comp. cover)

SA4 Battery Compartment Subassembly11 Battery Compartment housing12 Contacts and rivets on battery compartment13 Battery installation paper guide

SA5 Motor/Gearbox Subassembly14 Black wire15 Gearbox housing16 Output Gear17 Intermediate Gear 18 Driven Gear19 Gearbox cover screw20 Electric motor21 Safety lever22 Lubrication (red jelly on gears)

SA6 Gearbox Cover Subassembly23 Contacts and rivets on gearbox cover24 Red wire25 Blue wire26 Gearbox cover

SA7 Cutter Unit Subassembly27 Blade nut and bolt28 Blade29 Blade holder

Pencil Sharpener Indentured Parts List

21

Part Handling: Gross Motion

Order P/N Description QtySize (mm)

Thick (mm)

G.M. Code

Alpha (deg)

Beta (deg)

(deg)

Handling (sec)

1 29 Position blade holder 1 35 6 10 180 180 360 1.502 28 Locate blade 1 21 0.5 13 180 180 360 2.063 27 Locate and fasten blade screw and nut (tools: screwdriver & pliers) 1 9 1.5 03 180 0 180 1.694 SA7 Inspect & Release Cutter Sub-Assembly 1 35 6 5.255 26 Position Gearbox cover 1 65 1.9 10 180 180 360 1.506 23 Locate & rivet cover contacts 3 18 0.2 13 180 360 540 2.067 24 Solder red wire to cover 1 130 1 03 0 1.698 25 Solder blue wire to cover 1 111 1 03 0 1.699 SA6 Inspect & Release Gearbox Cover Sub-Assembly 1 65 1.9 10

10 15 Position gearbox housing (inverted) 1 58 50 10 180 180 360 1.5011 22 Apply lubrication to axle stands 3 00 0 1.1312 16 Locate output gear 1 25 2 03 180 0 180 1.6913 17 Locate intermediate gear 1 21 5.8 00 180 0 180 1.1314 18 Locate driven gear 1 21 5.8 00 180 0 180 1.1315 22 Apply lubrication to gear surfaces and axles 3 00 0 0 0 1.1316 SA6 Position gearbox cover sub-assembly 1 65 1.9 00 180 0 180 1.1317 21 Locate safety lever on gearbox cover (retain with one hand) 1 11 6.1 85 180 270 450 5.0018 SA6 Locate gearbox cover sub-assembly & safety lever (2 hand ops) 1 65 1.9 85 180 0 180 5.0019 19 Locate and fasten gearbox cover screw (self-threading) 1 15 3 00 180 0 180 1.1320 sa5 Invert & position partially complete gearbox sub-assembly 1 65 50 00 180 0 180 1.1321 20 Position electric motor near gearbox 1 43 23.6 10 180 360 540 1.5022 14 Solder blue wire to motor (2 hand ops) 1 111 1 03 0 1.6923 25 Solder black wire to motor (2 hand ops) 1 86 1 03 0 1.6924 20 Locate electric motor in gearbox 1 43 23.6 85 180 45 225 5.0025 SA7 Locate cutter unit sub-assembly 1 35 6 80 180 90 270 4.1026 SA5 Inspect, Test & Release Motor/Gearbox Sub-Assembly 1 65 50

22

Order P/N Description QtySize (mm)

Thick (mm)

G.M. Code

Alpha (deg)

Beta (deg)

(deg)

Handling (sec)

27 11 Position battery compartment housing (inverted) 1 70 32 10 180 180 360 1.5028 12 Locate & rivet battery compartment contacts 2 22 0.2 13 180 180 360 2.0629 SA4 Inspect & Release Battery Compartment Sub-Assembly 70 3230 9 Position battery compartment cover 1 43 2.5 10 180 180 360 1.5031 8 Locate and rivet (plastic heat stake) battery cover contacts 2 20 0.2 13 180 180 360 2.06

32 SA3 Inspect & Release Battery Compartment Cover Sub-Assembly 43 2.533 5 Position sharpener base 1 75 7 10 180 180 360 1.5034 SA3 Locate battery compartment cover sub-assembly 1 43 2.5 10 180 180 360 1.5035 11 Locate rubber feet on base and battery compartment cover 2 25 1.6 10 180 180 360 1.5036 SA2 Inspect & Release Base Sub-Assembly 1 75 737 SA5 Position motor/gearbox sub-assembly 1 65 50 00 0 180 180 1.1338 SA4 Locate battery compartment sub-assembly on motor/gearbox 1 70 26 80 180 180 360 4.1039 25 Solder black wire to battery compartment 1 86 1 03 0 1.6940 24 Solder red wire to battery compartment 1 130 1 03 0 1.6941 7 Position sharpener case 1 82 36 10 180 180 360 1.5042 SA4/ Locate battery compartment & motor/gearbox in sharpener case 2 96 32 80 180 10 190 4.1043 3 Locate and fasten battery compartment screw 1 8 3 01 180 0 180 1.4344 SA2 Locate base sub-assembly in sharpener case 1 75 7 10 180 180 360 1.5045 3 Locate and fasten battery compartment screws 2 9 3 01 180 0 180 1.4346 1 Locate and fasten sharpener case screws 2 14 3 01 180 0 180 1.4347 13 Install battery installation paper guide 1 50 1 13 180 180 360 2.0648 sa1 Invert and reposition partially complete sharpener assembly 1 96 50 00 180 0 180 1.1349 2 Locate pencil guide (tricky alignment) 1 32 11.7 05 180 0 180 1.8450 4 Locate shavings receptacle (snap fit) 1 73 36 05 180 15 195 1.8451 SA1 Inspect, Test & Release Pencil Sharpener Assembly 1 115 50

Part Handling: Gross Motion (con’t)

23

Order P/N Description QtySize (mm)

Thick (mm)

F.M. Code

Handling (sec)

Insertion (sec)

Total Time

1 29 Position blade holder 1 35 6 00 1.50 0.00 1.502 28 Locate blade 1 21 0.5 40 2.06 4.50 6.563 27 Locate and fasten blade screw and nut (tools: screwdriver & pliers) 1 9 1.5 48 1.69 8.50 10.194 SA7 Inspect & Release Cutter Sub-Assembly 1 35 6 5.25 18.255 26 Position Gearbox cover 1 65 1.9 00 1.50 0.00 1.506 23 Locate & rivet cover contacts 3 18 0.2 35 2.06 7.00 27.187 24 Solder red wire to cover 1 130 1 95 1.69 8.00 9.698 25 Solder blue wire to cover 1 111 1 95 1.69 8.00 9.699 SA6 Inspect & Release Gearbox Cover Sub-Assembly 1 65 1.9 48.06

10 15 Position gearbox housing (inverted) 1 58 50 00 1.50 0.00 1.5011 22 Apply lubrication to axle stands 3 99 1.13 1.20 6.9912 16 Locate output gear 1 25 2 00 1.69 1.50 3.1913 17 Locate intermediate gear 1 21 5.8 00 1.13 1.50 2.6314 18 Locate driven gear 1 21 5.8 00 1.13 1.50 2.6315 22 Apply lubrication to gear surfaces and axles 3 99 1.13 1.20 6.9916 SA6 Position gearbox cover sub-assembly 1 65 1.9 00 1.13 0.00 1.1317 21 Locate safety lever on gearbox cover (retain with one hand) 1 11 6.1 00 5.00 1.50 6.5018 SA6 Locate gearbox cover sub-assembly & safety lever (2 hand ops) 1 65 1.9 06 5.00 5.50 10.5019 19 Locate and fasten gearbox cover screw (self-threading) 1 15 3 38 1.13 6.00 7.1320 sa5 Invert & position partially complete gearbox sub-assembly 1 65 50 00 1.13 0.00 1.1321 20 Position electric motor near gearbox 1 43 23.6 00 1.50 0.00 1.5022 14 Solder blue wire to motor (2 hand ops) 1 111 1 95 1.69 8.00 9.6923 25 Solder black wire to motor (2 hand ops) 1 86 1 95 1.69 8.00 9.6924 20 Locate electric motor in gearbox 1 43 23.6 11 5.00 5.00 10.0025 SA7 Locate cutter unit sub-assembly 1 35 6 30 4.10 2.00 6.1026 SA5 Inspect, Test & Release Motor/Gearbox Sub-Assembly 1 65 50 87.30

Part Insertion: Fine Motion

24

Order P/N Description QtySize (mm)

Thick (mm)

F.M. Code

Handling (sec)

Insertion (sec)

Total Time

27 11 Position battery compartment housing (inverted) 1 70 32 00 1.50 0.00 1.5028 12 Locate & rivet battery compartment contacts 2 22 0.2 35 2.06 7.00 18.1229 SA4 Inspect & Release Battery Compartment Sub-Assembly 70 32 19.6230 9 Position battery compartment cover 1 43 2.5 00 1.50 0.00 1.5031 8 Locate and rivet (plastic heat stake) battery cover contacts 2 20 0.2 35 2.06 7.00 18.12

32 SA3 Inspect & Release Battery Compartment Cover Sub-Assembly 43 2.5 19.6233 5 Position sharpener base 1 75 7 00 1.50 0.00 1.5034 SA3 Locate battery compartment cover sub-assembly 1 43 2.5 30 1.50 2.00 3.5035 11 Locate rubber feet on base and battery compartment cover 2 25 1.6 97 1.50 12.00 27.0036 SA2 Inspect & Release Base Sub-Assembly 1 75 7 32.0037 SA5 Position motor/gearbox sub-assembly 1 65 50 00 1.13 0.00 1.1338 SA4 Locate battery compartment sub-assembly on motor/gearbox 1 70 26 02 4.10 2.50 6.6039 25 Solder black wire to battery compartment 1 86 1 95 1.69 8.00 9.6940 24 Solder red wire to battery compartment 1 130 1 95 1.69 8.00 9.6941 7 Position sharpener case 1 82 36 00 1.50 0.00 1.5042 SA4/ Locate battery compartment & motor/gearbox in sharpener case 2 96 32 08 4.10 6.50 21.2043 3 Locate and fasten battery compartment screw 1 8 3 48 1.43 8.50 9.9344 SA2 Locate base sub-assembly in sharpener case 1 75 7 00 1.50 1.50 3.0045 3 Locate and fasten battery compartment screws 2 9 3 38 1.43 6.00 14.8646 1 Locate and fasten sharpener case screws 2 14 3 38 1.43 6.00 14.8647 13 Install battery installation paper guide 1 50 1 00 2.06 1.50 3.5648 sa1 Invert and reposition partially complete sharpener assembly 1 96 50 00 1.13 0.00 1.1349 2 Locate pencil guide (tricky alignment) 1 32 11.7 30 1.84 2.00 3.8450 4 Locate shavings receptacle (snap fit) 1 73 36 30 1.84 2.00 3.8451 SA1 Inspect, Test & Release Pencil Sharpener Assembly 1 115 50 104.83

329.685.49

Assembly Total (sec) = (min) =

Part Insertion: Fine Motion (con’t)