Windshield wiper assembly 2
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| '''Wiper Blades''' | | '''Wiper Blades''' | ||
| Tearing | | Tearing | ||
- | | Reduced | + | | Reduced ability to effectively clean the windshield |
| 5 | | 5 | ||
| Material failure from high-cycle fatigue | | Material failure from high-cycle fatigue | ||
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| '''Wiper Arm Spring''' | | '''Wiper Arm Spring''' | ||
- | | | + | | High-cycle fatigue<br />Yielding |
- | | | + | | Allowing wiper arms to move away form windshield, preventing them from clearing the windshield of water |
- | | | + | | 5 |
- | | | + | | Debris on windshield getting wedged in the spring<br />Pulling the wiper arms too far away from the windshield during cleaing |
- | | | + | | 4 |
- | | | + | | Durability tests of spring |
- | | | + | | 5 |
- | | | + | | 100 |
- | | | + | | More durable spring<br />Use a torsion bar |
|} | |} | ||
Revision as of 23:51, 6 February 2011
Contents |
Report 1 - Product Analysis: Competitor Study
Executive Summary
Major Post-Production Stakeholders
A list of the major stakeholders of the competitors product was generated as long as a listing of their primary concerns with regard to the product. The benefit of this process is the expansion it has on our own awareness of the product since the redesign will be focused on benefiting these stakeholders and addressing their concerns in the most effective manner. Additional stakeholders or stakeholder concerns, along with a more quantitative understanding of the importance of these concerns, will be generated after more market research has been completed.
- User (Car-owner who used the product to clean their windshields)
- Effective: Effective removal of water, debris, and snow (light and heavy); Wide-cleaning motion; Leaves no streaks; Wide fluid dispersal
- Long-lasting components and structure: Durable and resistant to corrosion
- Easy and cheap replacement
- Safe: No sharp edges, would not injure the user, does not damage windshield
- Aesthetically appealing
- Must work under various climates extreme conditions: Especially - does not ice over or must be easy to de-ice
- Should not obstruct visibility both during operation and during storage
- Option to store replacement blades
- Broad selection of wiper blades – Ability to customize or upgrade
- Transporter (Concerned about the ease and safety of handling)
- Light-weight
- Durable in case of rough handling
- End-assembly automotive plant (Purchases sub-assemblies from separate manufacturer)
- Cheap, light-weight, durable, long-lifetime components and structures
- Simple and quick installation/assembly
- Safety, No VOC
- Efficient packaging within the engine compartment
- Minimize power usage and aerodynamic drag
- Repair mechanic (Concerned with ease of access and failure modes)
- Standardized
- Difficult to replace, but easy to repair
- Modular
- Safe: No sharp edges, would not injure the mechanic
- Other cars on the road (Concerned with other drivers being safe)
- Effectiveness of cleaning: Water, debris, snow, or ice is not flung in a dangerous way
- Does not fail (break) catastrophically
- Safe failure mode in case of collision
- Parking police (Wipers are needed to dispense traffic tickets)
- Wiper is safe and easy to lift so as to slide ticket underneath
Product Usability Study
Early on in our analysis of the competitor product, a usability study was conducted to both learn how the product functioned and how different users interacted with it. The goals of this study were to develop an initial understanding of the wipers use as well as areas where typical users may have difficulty operating the product, fail to operate the product correctly or operate the product in an unsafe manner. Two users were tested during this stage, one of our team members and someone without an engineering background.
The use of these windshield wipers can be broken into two processes. The first is the process loop that involves turning on and off the wipers to clean the windshield. The second is the typically closed-loop process cycle where the user observers the need for maintenance and then at a later date fixes any observed problems. The significant steps of the each process cycles were combined into the following process flow chart including the materials and signals generated and required during use. The first process loop is broken into the following steps. First, the driver checks the condition of the windshield for snow or ice. If there is snow he or she uses an ice scraper to clean of the windshield and clean off the wiper blades so that they work. Next, they turn on the car and, for the particular make and model of vehicle tested, shift the master lever down to turn on the wiper system. Next they adjust the speed and delay of the wipers by turning a knob inside the car. If the windshield becomes dirty, the user can use wiper fluid to clean of the windshield by using a switch inside the car. Finally, the user can turn off the wipers when they are no longer needed.
The second process loop involves intermittent maintenance either on a regular basis or as problems arise. For the use of this study we assumed that maintenance was done as needed since this was felt to be more representative of the general user and encompassed the worst case scenario. First, if the user sees that no wiper fluid is dispensed when they try to wash the windshield, they can fill up the wiper fluid tank in the engine compartment. Second, if the wiper streaks or fails to clean the windshield adequately, the user can replace the blade by pulling up the wiper blade, pulling the old blade off the clips holding it in place and pressing a new blade into the holding clips. More complex failures that are noticed by the user require taking it into a mechanic and were therefore not considered as part of the products use.
Based on this study we found that the while the general use of the product was well understood by both users, both users said they ignored issues with maintenance until a failure was noticed, and even then they both said they had delayed maintenance. This finding is problematic since dirty windshields are necessary for
Assembly
Product Operation
Dissection Exercise
Dissection Write Up
This section highlights the process used to reverse engineer the competitor’s windshield wiper shown in figure 1. This reverse engineering exercise dual objectives; first, it helped give an understanding of the function of the product and the manufacturing process used to create this product, secondly, it helped identify weaknesses in the design that may be developed into opportunities for design improvement.
Based on function, we disassembled the product into the following # sub-assemblies; Base substructure, large and small vibration mounts, 4 arms, gear casing, motor and the wiper. By taking a higher level view and observing these sub-assemblies and their interactions, we were able to fully develop the function structure diagram that is displayed in our usability study. By taking a closer view by dissecting and analyzing each component of the sub-assembly, we were able to create an assembly process for the entire structure.
Dissection Table
Bill of Materials | ||||||||
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Part Number | Sub-Assembly | Part Name | Quantity | Weight (in g) | Function | Manufacturing Process | Material | Image |
Base Structure |
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1 | Driver Side Wiper Casing | 1 | 111 | Protect Arm 3 (driver side) wiper mount linkage | Cast | Aluminum | Image:.jpg
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2 | Passenger Side Wiper Casing | 1 | 212 | Protect Arm 3 (passenger side) wiper mount linkage | Cast | Aluminum | Image:.jpg | |
3 | U-Shaped Connection Bar | 1 | 259 | Connect driver and passenger side wiper mount casings | Stamping | Steel | Image:.jpg | |
Vibration Mount (large) | ||||||||
4 | Metal Grommet Insert (large) | 2 | Stabilizes vibration mount by holding onto chassis | Extended and expanded | Steel | Image:.jpg | ||
5 | Rubber Mount (large) | 2 | Vibration dampening | Molding | Rubber | Image:.jpg | ||
Vibration Mount (small) |
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6 | Metal Grommet Insert (small) | 1 | Stabilizes vibration mount by holding onto chassis | Extended and expanded | Steel | Image:.jpg
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7 | Rubber Mount (small) | 1 | Vibration dampening | Molding | Rubber | Image:.jpg
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Arm 1 |
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8 | Arm 1 Linkage (w/ plastic ball-in-socket joint) | 1 | 53 | Transfers drivetrain's rotational motion 90 degrees to linkage mechanism's plane | Steel tube crushed and welded. Hole drilled, ball-in-socket joint stamped in. | Steel | Image:.jpg
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9 | Lock Washer | 1 | 2 | Distribute nut pressure | Steel | Image:.jpg
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10 | Nut | 1 | 3 | Attach Arm 1 to drivetrain | Tapping | Steel | Image:.jpg
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Arm 2 | ||||||||
11 | Arm 2 Linkage (w/ plastic ball-in-socket joint) | 1 | 149 | Transfer motion | Steel tube crushed and welded. Hole drilled, ball-in-socket joint stamped in. | Steel | Image:.jpg
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Arm 3 |
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12 | Arm 3 linkage (w/ plastic ball-in-socket-joint) | 2 | Transfer motion | Steel | Image:.jpg | |||
13 | Wiper Mount Pin | 2 | Transfer motion | Steel | Image:.jpg
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14 | Plastic Cover | 2 | 2 | Prevent fluid from seeping into linkage area | Injection Mold | Plastic | Image:.jpg
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15 | Screw-On Cap | 2 | 11 | Protect Wiper Mount Pin | Cast and Threaded Die | Steel | Image:.jpg
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Arm 4 |
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16 | Arm 4 linkage [Length: 20.5" (52 cm) | 1 | 177 | Transfer motion | Image:.jpg
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Other |
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17 | Top Washer | 1 | 1 | Steel | Image:.jpg
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Gear Casing |
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18 | Gear Casing Cover Screws | 4 | <1 | Attach cover to casing | Die | Steel | Image:.jpg
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19 | Drivetrain Mounting Bolts | 3 | 5 | Mount drivetrain to base | Die | Steel | Image:.jpg | |
Motor |
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20 | Motor Mounting Bolts (w/ Lock Washer) | 4 | 5 | Mount motor to base | Die | Steel | Image:.jpg
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21 | Motor Mounting Nuts | 4 | 3 | Mount motor to base | Tapping | Steel | Image:.jpg
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22 | Motor | 1 | Convert electric current via EMF to rotation of a linear worm gear | Standard purchased part | Image:.jpg
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Windshield Wiper |
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23 | Wiper | 2 | Rotate about pin and sweep across windshield | Plastic | Image:.jpg
| |||
24 | Blade | 2 | Remove water or other debris from windshield | Rubber | Image:.jpg |
DFMA
Manufacturing
Design for Manufacturing | |
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Guideline | Comments |
Minimize Part Count Eliminate fasteners, part consolidation | One motor Remove extra bolts Complex linkage can be replaced by another motor
|
Standardize Components Take advantage of economies of scale & known component properties | Different bolt sizes Different sized grommets that performed similar functions Standardized C-channel and tube size Standardized motor Standardized cast housing |
Commonize Product Line Economies of scale and minimum training and equipment | Same wiper assembly can be used in different vehicle models because of adjustable base length Cast parts remain the same; mold can be reused |
Standardize Design Feature Common dimensions for fewer tools and setups | Different screws all have the same head; only requires one type of screwdriver head |
Keep Designs Simple Simplest way to achieve needed functionality | Utilizes a constant, forward rotation of motor to achieve cyclic motion |
Multifunctional Parts e.g.: fingernail clipper | Four-bar linkage both achieves desired motion & connects the wipers |
Ease of Fabrication Choose materials easy to work with | Uses common metals (aluminum & steel) Uses common rubber for vibration isolation |
Avoid Tight Tolerances Causes exponential cost increases | Ball joints at ends of linkages allow for twisting & other non-planar motion within assembly without stressing parts Four-bar linkage arms have enough phase offset to allow for looser tolerance in linkage arm lengths |
Minimize Secondary & Finishing Operations Only where needed | Assembly is typically hidden, so aesthetic finishes are unnecessary |
Take Advantage of Special Process Properties e.g.: color in injection molding | Cast parts have ribs & optimized shape - does not add much complexity to casting process Text on cast parts(?) |
Assembly
Design for Assembly | |
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Guideline | Comments |
Minimize Part Count Eliminate fasteners, part consolidation | Three-piece housing can be cast as one Two motors can eliminate the need for a four-bar linkage
|
Minimize Assembly Surfaces and sequence them | Motor + gearbox are mounted on reverse side of linkages Grommets must be installed from sides of the assembly |
Use Subassemblies can be assembled and tested separately, can be outsourced | Motor + gearbox are preassembled Three-piece housing can be preassembled |
Mistake-Proof unambiguous, unique assembly orientation | Linkage arms are not labelled; their different lengths can lead to confusion during assembly No way to orient the cast housings |
Minimize Fasteners snap fits and part consolidation | Staked ends on pins Ball joints are staked in linkage ends |
Minimize Handling position for insertion or joining is easy to achieve | Fasteners are not all accessible from one side |
Minimize Assembly Direction ideal - add each component from top to base | |
Provide Unobstructed Access consider assembly path (e.g.: oil filter) | Motor housing screws are difficult to access |
Maximize Assembly Compliance chamfers and radii help assemble parts with variance | |
Features for Assembly Features that have no functionality in use but support assembly |
FMEA
Failure Mode and Effects Analysis | |||||||||
---|---|---|---|---|---|---|---|---|---|
Item & Function | Failure Mode | Effects of Failure | S | Causes of Failure | O | Design Controls | D | RPN | Recommended Actions |
DC Motor | Gear teeth stripped from excessive wear Gears out of alignment | Costly repair Temporarily inoperable | 7 | Excessive torque Obstruction on arm Body vibrations | 1 | Durability tests | 2 | 14 | Fail-safe built into motor control to shut down motor when excessive torque is detected |
Linkages | Misalignment in assembly Shearing of steel tube | Costly repair Temporarily inoperable Possible damage to components within the engine bay | 7 | Improper installation Environmental degradation | 2 | Durability tests | 1 | 14 | Clear markings or part geometry that only allows one assembly orientation |
Ball Joints | Ball becomes detached from joint Ball seizes in joint | Costly repair Temporarily inoperable | 7 | Debris Linkage misalignment Random forces | 2 | Dimension checks with gages Dye penetrant to check for adequate lubrication | 2 | 28 | Locker ring to prevent detachment Maintenance checks for adequate lubrication |
Wiper Arm | Elastic deformation | Reduced wiping effectiveness | 5 | Impact from flying debris User error Weather Damage from carwash | 4 | Stress tests | 4 | 80 | Recess arm beneath car hood Increase plastic strength |
Mounting Assembly | Detachment from body Grommet failiure | Damage to other components in the engine bay Reduced effectiveness | 8 | Loosened from body vibrations Bad installation Corrosion | 1 | Durability Tests Electrical sensor | 4 | 24 | Specify correct materials Allow for maintainance Progressive, controlled failure |
Wiper Blades | Tearing | Reduced ability to effectively clean the windshield | 5 | Material failure from high-cycle fatigue | 5 | Easily replaceable | 1 | 25 | Second blade Thicker rubber reinforcement where wiper blade attaches to wiper arm |
Wiper Arm Spring | High-cycle fatigue Yielding | Allowing wiper arms to move away form windshield, preventing them from clearing the windshield of water | 5 | Debris on windshield getting wedged in the spring Pulling the wiper arms too far away from the windshield during cleaing | 4 | Durability tests of spring | 5 | 100 | More durable spring Use a torsion bar |
DFE
After conducting a design for environment analysis on the competitor's windshield wiper, we discovered that the wiper system's largest effect on the environment is the greenhouse gas emissions through the burning of pretroleum in the use phase of the product. Other damaging effects on the environment are present during the production phase by way of greenhouse gas emissions and energy consumption through the manufacture of synthetic rubber and the manufacture of the windshield wiper system.
In the first section of our DFE analysis, we applied DFE guidelines to provoke areas of improvement in the wiper system design. The results are included below, however notable sources of improvement with respect to the environment are reducing the number of components either through eliminating linkages or entire wiper arms and enabling easier disassembly to make the steel and aluminum easier to recycle at end of life.
Design for Environment | |
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DFE Guideline | Suggestions for Improvement |
0. New Concept Development De-materialization, Functional optimization | -hydrophobic windshield -blowing a film of air -heated windshield/wipers/fluid |
1. Select Low Impact Materials Avoid toxics and ozone depleters, Use renewable, recycled, recyclable materials | - toxicity of the ethanol or methanol mixture of wiper fluid may be harmful when breathed in or ingested - disposal of fluid may lead to air or water pollution - fluid may corrode paint, rubber, wax, or plastic components |
2. Reduce Material Amount Reduce weight, transport volume | - depending on model of car, one wiper may clean effectively - designing system with two separate motors for each wiper would remove body connection and additional linkages |
3. Eco-Manufacturing Alternate production processes, reduce production waste | |
4. Optimize Distribution Less/cleaner/reusable packaging | |
5. Reduce Use-Phase Impact Lower energy consumption, reduce consumables | - maximize the efficiency of the wiper fluid pressure and spray pattern to reduce amount of fluid used while maintaining effective cleaning |
6. Maximize The First Life Increase durability, easy maintenance and repair | - design rubber vibration mounts to last lifetime of car
- since linkage assembly may be hidden underneath chassis, design structural components to last throughout lifetime |
7. End of Life Recycling, Design for Disassembly, Reuse of product, Re-manufacturing | - system can be easier to disassemble to make recycling of metal and rubber more desirable |
The first step in our Life Cycle Analysis was to list the materials involved in each stage of the wiper system's life. These results are included in the table below. For the purposes of our LCA, the production phase will be considered as a whole, while the use phase will be separated into the effects from the inputs of wiper blade replacement parts, washer fluid, and the combustion of gasoline.
EIO-LCA | ||
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Life Cycle Stage | Inputs | Outputs |
Material Extraction | Natural resources (iron ore, aluminum) | Steel, Rubber, Plastic, Aluminum Environmental Damage (GHG like CO2) |
Production | Materials, Energy, Labor, Facilities (Machinery and Storage0 | Parts, Assemblies, Packaged goods |
Use | Fuel to run motor Wiper Blades & Replacement parts Washer fluid | Used/damaged wiper blades Disposed washer fluid Environmental Damage (GHG like CO2) |
End of Life | Windshield wiper assembly Washer fluid and its plastic container Replacement blades | Recyclable Components: Steel, Rubber, some Plastic Landfill waste |
Transportation | Packaging Diesel fuel Labor | Packaging Environmental Damage (GHG like CO2) |
Energy Consumption
Using the Economic Input-Output Life Cycle Assessment method on EIOLCA.net enabled us to quantify the energy consumption and greenhouse gas emissions generated both through the production and use phases of our product. We found that the majority of energy consumption effects was due to petroleum refineries, while synthetic rubber manufacturing and power generation and supply also had significant energy draw.
Motor Vehicle Parts Manufacturing
Greenhouse Gases
The EIOLCA models showed that the largest greenhouse gas effects came from oil and gas extraction in the production of petroleum, however power generation and supply and petroleum refineries were also significant.
Motor Vehicle Parts Manufacturing
Life Cycle Analysis
Team Member Roles (Report I)
The team member roles were assigned as follows by a process of individuals volunteering based on their preferences and expertise in an area:
Role | Team Member |
---|---|
Team Leader | Justin Whaley |
DFMA Lead | Mike Lin |
FMEA Lead | Max Gustafson |
DFE Lead | Andrew Socha |
While each team member was present for the usability study, the dissection, and the in-class exercises, the write-ups for the analysis sections of the report were contributed by the individual analysis leads. The team leader completed the write-ups for the usability study, the conclusions from the dissection exercise, compiled the PowerPoint presentation and scheduled weekly team meetings.
References
[1] Dieter, George Ellwood., and Linda C. Schmidt. Engineering Design. Boston: McGraw-Hill Higher Education, 2009. Print.