Leaf blower
From DDL Wiki
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 | Inoperable | 7 | Short circuit | 3 | Coated wire | 4 | 84 | None | N/A |
Electric Motor and Wiring | On/Off Switch Broken (Plastic fracture prevents operation) | Inoperable | 7 | Broken mechanism due to fatigue or misuse | 4 | Sliding design does not experience substantial fatigue | 4 | 112 | None | N/A |
Electric Motor and Wiring | Power cord worn | Potential shock hazard, may be inoperable | 8 | Cord worn by frequent twisting and bending | 5 | Flexible cord coating, longer cord is more flexible, wires also coated independently of cord | 2 | 80 | Plug directly into case with no wire; use wireless power source | Design Engineer |
Electric Motor and Wiring | Contactor corroded | May become inoperable | 5 | Exposure to water | 4 | Motor housing, plastic insulators for wires | 8 | 160 | None | N/A |
Electric Motor and Wiring | Interlock activator spring corroded | May become inoperable | 5 | Exposure to water | 3 | Enclosed in motor housing | 8 | 120 | None | N/A |
Fan and Mulcher | Fan jammed | Fan stops, motor may overheat | 3 | Heavy or thick objects in fan/mulcher | 6 | Blade guard for blowing, mulcher blades for use with vacuum | 3 | 54 | None | N/A |
Fan and Mulcher | Broken blade | Decreased mulching efficiency | 2 | Rocks or other hard objects in mulcher | 4 | Strong mulcher blades, blade guard | 7 | 56 | None | N/A |
Fan and Mulcher | Loose blade | Decreased air flow | 4 | Nut loosened by spinning and vibration | 2 | Left handed nut | 5 | 40 | None | N/A |
Blower and Vacuum Attachments | Blower chute locking tab broken | Unable to secure blower chute and vacuum bag, cannot use as blower or collect vacuum debris easily | 5 | Fatigue stress | 4 | Design for repeated loading | 1 | 20 | Consider different locking mechanism | Design Engineer |
Motor Housing | Cracked motor housing | Vibration and difficulty in use | 3 | Misuse (e.g. dropped) | 5 | Design for strength | 3 | 45 | Consider padding areas likely to experience impact | Design Engineer |
Blower and Vacuum Attachments | Torn Leaf collection bag | Unable to collect leaves | 4 | Excessive or improper use | 5 | Bag fabric is tear resistant | 3 | 60 | None | N/A |
Blower and Vacuum Attachments | Air concentrator locking tab broken | Unable to use air concentrator | 3 | Overuse leading to fatigue failure | 5 | None | 2 | 30 | Consider different locking mechanism | Design Engineer |
The FMEA analysis of the leaf blower studied for this report revealed no particularly large risk priority numbers with which engineers should be concerned. The highest RPN were generated by failure modes resulting from corrosion of pieces inside the motor housing that would cause inoperability of the product. However, these failures modes resulted in high RPN's mainly because they are difficult to detect due their location inside the motor housing. Because they seem unlikely to occur except for cases of gross misuse (e.g. left out in the rain) it does not seem worthwhile to focus any design effort on these failure modes. Other high numbers were from failure modes associated with electrical components. Of these, the failure of the cord due to a break in the cord casing due to fatigue from frequent bending in use provides the greatest opportunity for redesign. While this failure mode can occur without causing operability issues or hazards, it can also be very dangerous if cords carrying current are exposed to the user. Potential opportunities for improvement include redesigning the power connection to avoid use of a cord on the blower side and designing the cord for greater flexibility.
Other potential failure modes produced risk priority numbers that are of little concern as failure is unlikely to occur and will likely not have severe consequences and be easily detectable. However, it is worth noting that there are a number of plastic locking tabs used in attaching accessories that could potentially fail as a result of repeat installation and removal. Additionally, use of the product suggested that these tabs can be difficult and frustrating to use. The manner in which these accessories are connected could provide an opportunity for improvement in order to eliminate failure modes and improve user satisfaction. Most potential improvements would have to be implemented in the design stage.
Design for Environment
Engineering Analysis
Team Members and Processes
Resources
Dieter, G.E. and L.C. Schmidt. (2009). Engineering design. New York, NY: McGraw Hill.