Vacuum cleaner
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Executive Summary
During our product analysis of a Dirt Devil Swift Stick we came across several notable observations. As we went through the uses of the product and used them for its main function a few basic problems occured. These problems ranged from small annoyances to major hazzards. This caused us to further look into customer needs and how they can be addressed for this product. A vacuum cleaner is a common household appliance designed for cleaning purposes. It may be easy to design a vacuum for one of the many uses a customer buys a vacuum for, but to design a vacuum that can cover all of the uses is the challenge. Our customers need more than just a vacuum that picks up a mess off the carpet, they also want to be able to clean up a spill on a hard floor, or vacuum the steps with ease. Those are a few of the problems we will address in our product redesign. Once the product uses and customer needs were completely documented the product was dissected and all of the parts were analyzed and documented in detail. This gave us a more complete understanding of how this product was manufactured and assembled. The dissection gave us a basis for further analysis. This further analysis included DFMA, FMEA, DFE, and Quantitative Mechanical Analysis. The DFMA for this product was well thought out and little or no improvements can be made in this area. The screw fastener design lend itself to making the vacuum robust and able to hold together through any bumps or vibrations of the vacuum, even though this manufacuring proceedure would take longer. There were also many times during our dissection where we noted places that the plastic was molded in such a way that the parts could not be put together incorrectly. Only one time did we notice that an improvement could be made at the spot where the electrical cord meets the motor housing. During further analysis of the failure modes we discovered that _________________________________________________________________________________________________________________________________From these analyses, decisions could be made to improve upon any areas of manufacturing that could be lacking or cause ill effects on the environment.
Product Evaluation
During product evaluation our group used the vacuum cleaner in an everyday use situation. We noted things that worked well along with external problems that occured with everyday use.
Function
A vacuum cleaner is common household appliance used for cleaning purposes. A vacuum cleaner cleans by creating suction. A pump creates a pressure difference inside the unit causing atmospheric air to be forced up through a tubing system. Most vacuum cleaners utilize a rotating brush at its entrance to help "sweep" dust and dirt into the suction path. Vacuumed particles are finally depostited in some collecting container that can either be removed or emptied after use.
Main Compnenets
There are six main components to a standard vacuum cleaner:
-Intake port which may include attachments such as a brush
-exhaust port
-Electric motor
-Fan
-Pourous bag or container
-Housing
Diagram found at HowStuffWorks.com HowStuffWorks
How it Works
A vacuum operates by creating a low pressure area inside the machine causing for air at atmospheric pressure to be forced or "sucked" into the system. What connected to a power supply, the motor uses the potential difference as energy for its work. Most commonly, the motor uses a fan; spinning the fan causes the low pressure region and therefore the suction. A spinning brush is often used to help sweep up dust, dirt or other particles into the air stream. Particles pass through the intake port and are deposited into some type of container. Air is forced out through the exhaust port to allow for the continuous flow of air. Finally, dirt and dust is removed by either removing the porous bag or emptying the removable container. A general diagram is seen above.
Information gathered from HowStuffWorks HowStuffWorks site
Product Uses
For normal use of a vacuum cleaner:
-Unwind power cord and connect unit to home outlet
-Power on unit
-Move unit in back and forth motion covering the vacuum area desired
-Turn off unit
-Wind power cord and store
The normal use of a household vacuum cleaner can be seen in the flow chart below.
Customer Needs
The traditional user needs for a vacuum cleaner are:
-Ability to provide suction
-Effective cleaning ability of carpet, hard wood and any other household surfaces
-Comfortable use while operater is standing
-Ability to transport easily (weight and bulk)
-Easy removal of dirt/dust container/bag
-Durability
-Easy Storage
-Fair cost
-Quiet and smooth running
Bill of Materials
An extensive list of parts in the vacuum. Information includes part names, quantities, weights, function of use, process for manufacturing, and the material the parts are made from.
Product Analysis
In depth analysis of the individual parts and function of the vacuum. This allowed for more discussion for possible improvement to the existing product. Improvements were found in the areas of manufacturing, failure, and environment.
Design for Manufacturing and Assembly
Design for Manufacturing and Assembly (DFMA) is a set a of tools and methods for analyzing the manufacturing process in order to develop a simplified process of reduced cost.
Current DFMA
The current product has most likely been through an extensive improvement process. Nearly all of the parts of the vacuum has only one possible fit so there is no opportunity for confusion or mistakes. Making the design even better is the inclusion of notches between fitting parts. The addition of notches allow for correct pieces to easily slide together into the correct position.
There are a few areas that could be improved.
Recommended Improvements
The current design requires many screws to be used for assembly. This process can be improved with a redesign utilizing snaps to fasten the product. Snaps would make assembly easier and faster but also more robust. A vacuum's operation experiences many vibrations. These vibrations can lead to eventual losening of the screws. The use of snaps would eliminate the potential for this problem.
Another problem with the current design is the process of attaching the power cord. The current design has multiple ambiguous positions for placement of the cord. It is the one part where this occurs. This process can be easily simplified by merely adding a color code or the elimination of the multiple choices.
Finally, there were a few different screws used in the assembly. There was not a major difference between the different types which could possibly lead to some mistakes or confusion when deciding which component to use. Making the screw types more identifiable with there correct position could further aid assembly. Elimination of screw elements would also solve this problem.
Failure Mode Effects Analysis
Chris, put some stuff in here to explain what this table is.
Item and Function | Failure Mode | Effects of Failure | S | Cause of Failure | O | Design Controls | D | RPN | Recommended Actions | Responsibility & Deadline | Actions Taken | S | O | D | RPN |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
Vaccum Channel *Creates channel for vaccum flow | Jams/Clogs | No air flow | 4 | Objects jammed at inlet | 5 | Product testing in normal situations | 3 | 60 | Explore other inlet design options | N/A | N/A | 4 | 5 | 3 | 3 |
Wheel *Allows vaccum to roll | Jammed/Stops turning | Vaccum can no longer roll | 4 | Axel dammage | 2 | Quality control testing | 1 | 8 | Take no action | N/A | N/A | 4 | 2 | 1 | 8 |
Motor/Blower *Provides air flow | Blower stops turning | Fails to produce suction | 6 | Missing filter/hole in filter causes debris to damage moter/blower | 2 | Test use when filter is damaged | 2 | 24 | Take no action | N/A | N/A | 6 | 2 | 2 | 24 |
Electrical Cord *Provides power to motor | Does not fit properly into electrical outlet | No electrical connection can be made, Potential for electric shock | 8 | Tight fit around electrical outlet | 5 | Failure observed by user | 1 | 40 | Explore other cable/outlet design options | N/A | N/A | 8 | 5 | 1 | 40 |
Switch activator *Makes circuit connection to provide power turn on motor | Does not make connection | Vaccum will not turn on | 4 | Shaft does not line up due to wear | 1 | Quality testing by pushing button Extended life testing | 3 | 12 | Explore more durable materials | N/A | N/A | 4 | 1 | 3 | 12 |
Design for Environment
Design for environment (DFE) is method for analyzing the environmental impact of a product. DFE considers a product’s manufacturing processes as well as its use throughout the product’s life cycle.
The environmental impact of a product can be determined through a process called EIO-LCA. This process takes into account all sectors of the econonmy affected by the manufacturing and distribution of the specified product. The EIOLCA software determines the impacts of economic activity, energy usage, greenhouse gas emissions, employment, etc.
For our analysis we found Power generation and supply to be the sector to have the most environmental effect. Power generation and supply was responsible for roughly 30% of the total greenhouse gas release and nearly 75% of total air pollutant release. We also found that the power supply to the manufacturing has the most effect on the environment of the vacuums various stages. The manufacturing stage was also responsible for over half of the toxic releases into the environment. Pie charts are show below.
Chart for Air pollutants
Chart for toxic releases
Chart for greenhouse gases
For our product we evaluated the economic impact as well as the energy usage for the products end-of-life cycle. Using the software we evaluated the economic impact of a household vacuum production for 1 million dollars of economic activity. It was determined that 2.3 million dollars total is needed for production. Using the price of a single vacuum, (30 USD,) we determined the per unit price of manufacturing to be 69 USD. The resulting table is shown below. .
Economic Activity
Sector | Total Economic $mil | Value Added $mil | Direct Economic $mil | Direct % | |
---|---|---|---|---|---|
Total for all sectors | 2.30 | 0.987 | 1.62 | 70.4 | |
335212 | Household vacuum cleaner manufacturing | 1.00 | 0.375 | 1.00 | 100.0 |
420000 | Wholesale trade | 0.096 | 0.064 | 0.050 | 52.4 |
550000 | Management of companies and enterprises | 0.072 | 0.051 | 0.039 | 53.9 |
325211 | Plastics material and resin manufacturing | 0.063 | 0.015 | 0.041 | 64.6 |
32619A | Plastics plumbing fixtures and all other plastics products | 0.056 | 0.023 | 0.051 | 91.8 |
It is clear after our analysis that the power generation and supply of the manufacturing process has the most impact. There is certainly some uncertainty in our data. We could benefeit from further analyzing the environmental impact of the use of the product through the end of its life cycle. Still, even with our uncertainty, the power generation and supply sector is so much greater than all others that we can come to our conclusions with great confidence.
In addition to the evaluation of manufacturing impact, we evaluated the impact of electrical use. For our unit we estimated the use to be 100 hr/year. This value considers home use as well as use by cleaning professionals. With the vacuum rating and our electrical supplier’s kw-hr price, the cost for a year of operation is 117 USD/year. BAsed on the EIOLCA software, we determined that on yearly basis, the electrical power supply actually produces slightly larger amount of greenhous gases than does the manufacturing process. For air pollutants, the manufacturing of the vacuum and the production of the power supply provide similar amounts of pollutants. For our product we can assume that a vacuum will occur less than an annual basis, (a vacuum will not be bought every year.) Considering this, the environmental effect of the electric power production becomes very important.
For a green design, the power problem most be top priority; Although power supply for the production phase is clearly a problem, we would be most effective in a design that addresses the products energy consumption during use. Energy for operation has the most environmental impact over a products life span. Addressing the issue would benefeit both the end user, having to pay less operation costs, and the manufacturer, creating a more attractive product to market to the consumer.
Quantitative Mechanical Analysis
Air flows in the vaccum from the blower to the vaccume outlet. In between, the air flows through parts of the vaccum assembly with different cross sectional areas. The path of air is as follows:
1.) Air is pulled in through the initial vaccum channel (arrow point) (Fig. A)
2.) Air travels through a rectangular cross-sectional channel
3.) Air flows through a circular swivel connector (Fig B)
4.) From the connector, the air travels throgh the waste basket
5.) Air is pulled from the waste basket through a filter (Fig C)
6.) Air is pulled in to the blower inlet
7.) Air pulled through impellar and exhaled out the vent on the motor housing
The airflow, Q, does not change at any point through the vaccum. Airflow is dependent only on the fluid power of the motor/blower assembly. The velocity, however, does change at different points through the flow channels. As the cross-sectional area increases, the velocity of air decreases. As the cross-sectional area decreases, the velocity increases. Suction produced at the outlet is based on the dynamic pressure at that point. Dynamic pressure is directly proporational to the square of the velocity.
If the motor and impellar efficiencies were known, as well as the voltage and current being delieverd to the motor, then the suction pressure could be estimated using the formulas Q=VA where A is the cross-sectional area and V is the air velocity, and q=1/2 rho * V2 where rho is the fluid density and q is the dynamic pressure.