Leaf blower

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! Assembly/Parts !! Failure Mode !! Consequence of Failure !! S !! Causes of Failure !! O !! Safeguards !! D !! RPN !! Recommendations !! Responsibility  
! Assembly/Parts !! Failure Mode !! Consequence of Failure !! S !! Causes of Failure !! O !! Safeguards !! D !! RPN !! Recommendations !! Responsibility  
|-   
|-   
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| Electric Motor and Wiring || Blown Fuse || Motor does not run || 6 || Short circuit || 3 || Coated wire || 1 || 18 || None || N/A
+
| Electric Motor and Wiring || Blown Fuse || Motor does not run || 7 || Short circuit || 3 || Coated wire || 3 || 63 || None || N/A
|-  
|-  
-
| || Switch Broken || || || || || || || || ||
+
| Electric Motor and Wiring || Switch Broken || Unable to turn blower on || 7 || Broken mechanism due to fatigue or turning knob while off || 3 || Sliding design does not experience substantial fatigue || 3 || 63 || None || N/A
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|-
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| Fan and Mulcher || Fan jammed || Motor overheats, does not run || 6 || Heavy or thick objects in fan || 4 || Blade guard for blowing, mulcher blades for use with vacuum || 2 || 48 || None || N/A
+
| Electric Motor and Wiring || Power cord worn || Potential shock hazard, may not run || 8 || Cord worn by frequent twisting and bending || 5 || Flexible cord coating, longer cord is more flexible || 2 || 80 || Plug directly into case with no wire; use wireless power source || Design Engineer
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|-
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| Blower chute, Vacuum chute, bag and attachments || || || || || || || || || ||  
+
| Fan and Mulcher || Fan jammed || Motor overheats, does not run || 6 || Heavy or thick objects in fan/mulcher || 4 || Blade guard for blowing, mulcher blades for use with vacuum || 2 || 48 || None || N/A
 +
|-
 +
| Fan and Mulcher|| Broken blade || Decreased mulching efficiency || 2 || Rocks or other hard objects in mulcher || 3 || Strong mulcher blades, blade guard || 7 || 42 || None || N/A
 +
|-
 +
| Fan and Mulcher || Loose blade || Decreased air flow || 5 || Nut loosened by spinning and vibration || 2 || Left handed nut || 5 || 50 || None || N/A
 +
|-
 +
| Blower and Vacuum Attachments || || || || || || || || || ||  
|-
|-
| Motor Housing and Connections || || || || || || || || || ||   
| Motor Housing and Connections || || || || || || || || || ||   

Revision as of 16:00, 12 September 2009

Contents

Executive Summary

Stakeholders and Stakeholder Needs

Product Use and Function

Product Use

Product Design and Function

Motor

Safeties and Interlocks

Power Control

Product Components

Part Number Description Quantity Function Material Manufacturing Mass (g) Picture
001 Screw 15 Hold case together, hold bracket down Steel Standard item 1
002 Housing Right Side 1 Protect motor Plastic Injection Molded 546
003 Housing Left Side 1 Protect motor Plastic Injection Molded 534
004 Mulcher/Fan blade guard 1 Protect user from blade Plastic Injection Molded 204
005 Chute Locking Tab 1 Hold chute on housing Plastic Injection Molded 14
006 Bottom Attachments Release Tab 1 Release bottom attachments for removal Plastic Injection Molded 13
007 Chute Locking Tab Spring 1 Hold Chute locking tab in place Steel Drawn 13
008 Torsion bar for heal release 1 Holds heel release in place and allows for unlocking Steel Bent 13
009 Bottom Attachment Interlock Trigger 1 Depresses contact for bottom safety interlock Plastic Injection Molded 10
010 Spring for interlock trip 1 Holds trigger in off position when attachment is not installed Steel Drawn 1
011 Heel Attachment Safety Switch Assembly 1 Allows operation only when bottom attachment/guard is installed Plastic, Steel, Copper Injection molding, stamping 1
012 Wire Bracket 1 Holds wires in place Steel Stamped 6
013 Male Connector 3 Connects components in electrical circuit Steel Punched N/A
014 Male Connector Insulator 2 Protects connections from contacting other electrical components Plastic Injection Molded 1
015 Female Connector 3 Connects components in electrical circuit Steel Punched N/A
016 Female Connector Insulator 2 Protects connections from contacting other electrical components Plastic Injection Molded 1
017 Power Cable Rubber Grommet 1 Adds flexibility to power connection Rubber Injection Molded 8
018 Power Cable 1 Connects motor to power source Copper, rubber, plastic Pre-assembled component 74
019 Soft connector isolator 2 Protections connections from contacting other electrical components Plastic Molded 1
020 Selector Switch Insulation/Mount 1 Holds selector switch contacts in place Plastic Injection Molded 2
021 Selector Knob Slider 1 Slides when knob is turned to turn blower to OFF/I/II Plastic Injection Molded 2
022 Switch Contactor 1 Contacts appropriate output contact to close circuit when blower is on and select speed Steel Stamped 1
023 Contactor from safety interlock 1 Closes circuit to switch when bottom attachment is secure Steel Stamped 1
024 Contactor for High Power 1 Connects circuit in high power orientation Steel Stamped
025 Contactor for Low Power 1 Connects circuit in low power orientation Steel Stamped 1
026 Diode 1 Prevents current from alternating to provide low power mode Various Purchased Component 1
027 Knob 1 Allows user to turn blower on and switch between low and high power mode Plastic Injection Molded XX
028 Selector Housing 1 Holds selector switch connectors and slider in place and attaches to knob Plastic Injection Molded N/A
029 Pin 2 Attaches knob to selector housing Steel Pulled N/A
030 Fan/Mulcher Blade 1 Draws air into blower to be blown out and mulches leaves in vacuum mode Aluminum Cast 322
031 Blade Spacer 1 Separates blade from motor housing in order to prevent incidental contact Plastic Injection Molding 16
032 Blade nut 1 Holds blade and blade spacer on shaft, left handed to prevent loosening Plastic Injection Molded 7
033 Bearing mount 1 Holds shaft bearing in place Steel Stamped 56
034 Wire Contact Spring 1 Holds wires in place and provides contact across motor coils Steel Drawn 1
035 20 A Fuse 1 Protects motor from overload Various Standard Component 6
036 Fuse Insulation 1 Protects fuse from contact with other electrical components Plastic Purchased (tube) N/A
037 Motor Assembly 1 Drives shaft to rotate fan Various Standard Component 619
038 Motor Magnet and outer coil 1 Provides magnetic field to drive motor Various Standard Component 946
039 Zip Tie 6 Holds components (wires, bag) in place Plastic Standard Component N/A
040 Blower Chute Attachment 1 Directs air from fan to blower extension Plastic Injection Molded 128
041 Blower Chute Midsection 1 Extends blower chute from attachment to tip Plastic Injection Molded 97
042 Blower Chute Air Concentrator 1 Concentrates air leaving blower Plastic Injection Molded 48
043 Blower Chute Oscillating Head Tip 1 Swivels under air pressure to allow air to be blown in a multiple directions for wider path Plastic Injection Molded 18
044 Blower Chute Oscillating Head Connector 1 Links oscillating tip to connection to chute midsection Plastic Injection Molded 17
045 Oscillating Tip Connection to Chute Midsection 1 Connects oscillating tip to chute midsection Plastic Injection Molded 44
046 Vacuum Tube, Fan End 1 Connects to bottom of motor housing for vacuum use Plastic Injection Molded N/A
047 Vacuum Tube Bottom 1 Connects to fan end to suck leaves into mulcher Plastic Injection Molded 1031
048 Leaf Bag 1 Collects debris when used in vacuum configuration Nylon Sewn 245
049 Bag/Chute Connector 1 Connects leaf bag to blower outlet Plastic Injection Molded 71

Design for Manufacture and Assembly

Failure Modes and Effects Analysis

Considering ways in which a product could potentially fail is a crucial part of the design process. All products must be designed such that they are both safe and reliable for use and any potential dangers must be addressed in the design phase. The table below shows the primary ways in which the leaf blower studied for this report could potentially fail as well as the probable consequences, severity, causes, likelihood of occurrence, design safeguards, detectability of failure, recommendations for improvement and responsibility for making changes. The values assigned for severity, likelihood of occurrence and detectability (S, O, and D respectively) are based on the tables found in Dieter and Schmidt's 'Engineering Design'. The risk priority number (RPN) is simply the product of these numbers and can be used to assign a priority to potential failures in order to organize the redesign process.

Assembly/Parts Failure Mode Consequence of Failure S Causes of Failure O Safeguards D RPN Recommendations Responsibility
Electric Motor and Wiring Blown Fuse Motor does not run 7 Short circuit 3 Coated wire 3 63 None N/A
Electric Motor and Wiring Switch Broken Unable to turn blower on 7 Broken mechanism due to fatigue or turning knob while off 3 Sliding design does not experience substantial fatigue 3 63 None N/A
Electric Motor and Wiring Power cord worn Potential shock hazard, may not run 8 Cord worn by frequent twisting and bending 5 Flexible cord coating, longer cord is more flexible 2 80 Plug directly into case with no wire; use wireless power source Design Engineer
Fan and Mulcher Fan jammed Motor overheats, does not run 6 Heavy or thick objects in fan/mulcher 4 Blade guard for blowing, mulcher blades for use with vacuum 2 48 None N/A
Fan and Mulcher Broken blade Decreased mulching efficiency 2 Rocks or other hard objects in mulcher 3 Strong mulcher blades, blade guard 7 42 None N/A
Fan and Mulcher Loose blade Decreased air flow 5 Nut loosened by spinning and vibration 2 Left handed nut 5 50 None N/A
Blower and Vacuum Attachments
Motor Housing and Connections

Design for Environment

Engineering Analysis

Team Members and Processes

Resources

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