Cordless Handheld Vacuum Cleaner

Transcription

1 Cordless Handheld Vacuum Cleaner R.A.M. Squad Alex Bellott Robert Hayes Marc Yarnall ME 340: Design Methodology May 5, 2015

2 Table of Contents 1. Letter of Intent Customer Needs Customer Needs Target Audience External Search and Benchmarking Research on Existing Products Intended Market Segment Descriptions and Specifications of Three Competitors Patent Search Design Specifications Design Specifications Weighted Selection Black Box Concept Generation Concept Generation Process Concept Subsystems Concept Designs Concept Selection Selected Concept Theoretical Analysis Requirements for Flowrate Impeller Specifications Minor Losses First Prototype Evaluation Materials and Construction Process Performance and Results Positive and Negative Aspects Plan to Improve Prototype Component and Material Selection Components and Materials Common off the Shelf Parts Environmental Impact

3 10. Fabrication Process Creating the Individual Parts Assembly Process Safety IEC & IEC Scope Requirements IEC Scope Requirements Economic Justification Bill of Materials Overview Injection Mold Cost Analysis Commercial Off the Shelf (COTS) Parts Price Analysis Net Present Value Analysis Industrial Design Aesthetic and Ergonomic Features Simple Use Extremely Safe Anthropometric Data Final Prototype Performance and Evaluation Construction Process/Materials Used Alterations Positives and Negatives of Final Prototype Performance Usability Suction Power Conclusion Poster References Appendix

4 1. Letter of Intent Dear Manager of ACME Tool Company, Our names are Robert Hayes, Marc Yarnall, and Alex Bellott and as part of our Mechanical Engineering Design Class, we intend to participate in the Cordless Handheld Vacuum Design Project. Our team, which we have named R.A.M. Squad, plans to reverse engineer an 18V cordless drill to create the prototype vacuum cleaner. Using parts from an already existing ACME product line should help lower the production costs if our item is manufactured in Shanghai. The vacuum needs to have economic potential, pleasant aesthetics, and the finest performance. The team s main goal is to create a cheap, cordless, handheld, functional vacuum cleaner. Therefore, it must retain all collected material and the user must be able to empty this material effortlessly. No material can exit through the exhaust for obvious reasons. The design will retain the drill s motor, battery connector and battery pack. We will decide what other parts of the drill to utilize during the concept generation phase of our design process. Overall, our group has a strict $30 budget limit. This strict budget will help ensure that this design has as much economic potential as possible. The Pennsylvania State University has many available resources to help us with this project. Most of the construction will happen at the Learning Factory. This building provides many manufacturing capabilities that will be extremely useful during the project. We also have access to fabricating components using rapid prototyping, water jet, CNC and casting methods. At least one component in the vacuum will be fabricated using one of these processes. We will make these decisions during the concept generation and selection phases. Finally, we have access to free nuts, bolts, washers and fasteners at the MNE instrument room at 23 Reber. All these resources will greatly help us create the prototype quickly and cheaply. R.A.M. Squad plans to follow a very structured development process to create the prototype. We plan to start with a planning phase. Here, the team will research current handheld vacuum designs and learn about the customer s needs. This leads to concept development. Each group member will develop their own concepts and share them with the group. We will then discuss the different ideas and vote on our favorites. While a consensus is ideal, we will resort to a majority rule if a dispute lingers for too long. Once we settle on a concept, we will build our first beta prototype. After evaluating the prototype, we will create a detailed design and build our final alpha prototype. This design will also be evaluated via a competition. We will complete against other groups to see who can collect the most uncooked white rice. It should be noted that this competition will only judge the vacuum s performance and not judge the vacuum on other important factors like aesthetics, economic potential and durability. Throughout the design process, we also plan to create weekly progress memos. There will also be memos for important tasks during the development process. For example, we will have memos for concept generation, concept selection, theoretical analyses and more. This will help us keep track of ideas and construct the final report. We have created a preliminary Gantt Chart (Figure 1) to help guide us through this project. This chart lists when we plan to start and finish different tasks. Many of these tasks must be completed by a certain date. For instance, the due dates for the memos are finite. Some aspects can and probably will change as we work on this project. Please note that the final prototype will be finished by the end of 4

5 April If our design is chosen, there should be plenty of time to further refine the design, create a production schedule and have the final product on the shelves for Christmas Overall, R.A.M. Squad is excited to design and build the handheld vacuum cleaner for the ACME Tool Company. We will follow all the design constraints and will design an innovative, user-friendly prototype. Please let us know if you have any questions or concerns. Sincerely, Marc Yarnall, Robert Hayes, and Alex Bellott Task Description Completion Date 1 Letter of Intent 3-Feb 2 Customer Needs 5-Feb 3 External Search and Benchmarking 10-Feb 4 Design Specifications 17-Feb 5 Concept Generation 24-Feb 6 Concept Selection 3-Mar 7 Theoretical Analysis 19-Mar 8 Build First Prototye 26-Mar 9 Component and Material Selection 2-Apr 10 Evaluate First Prototype 30-Mar 11 Build Final Prototype 20-Apr 12 Fabrication Process Memo 7-Apr 13 Safety Memo 14-Apr 14 Economic Justification Memo 16-Apr 15 Industrial Design Memo 21-Apr 16 Final Protoype Performance 23-Apr 17 Performance Memo 28-Apr 18 Poster Presentation 30-Apr January 27th- 3rd-9th 10th- 2nd 16th February March April 17th- 23rd 24th- 2nd 3rd-9th 10th- 16th 17th- 23rd 24th- 30th 31st-6th 7th-13th 14th- 20th 21th- 28th Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 Figure 1: Gantt Chart 5

6 2. Customer Needs The purpose of this section is to discuss the customer needs in relation to the cordless vacuum project. This section will also examine the methods used to find customer needs, and why the methods used allowed for an adequate characterization of the target customer and their needs Customer Needs While doing research about cordless handheld vacuum cleaners, we found that many of the customer needs were relatively straight forward and expected. Many of the primary customer needs dealt with the overall functionality of the vacuum cleaner. The customer need that seemed to be the most important for most customers was having a vacuum with adequate suction power. Many customers mentioned how they became frustrated when their vacuum cleaners would not pick up all the dust and dirt the first time they went over it. This issue meant that users had to then go back to the same areas multiple times in order to clean up all of the dirt. However, in most cases there is a trade-off between suction power and loudness. For another (less important) customer need that we came across is having a vacuum cleaner that is not loud enough to block out ambient sounds such as a telephone or doorbell ring. Customers also expressed for a need for the vacuum to work well in tight areas such as corners. Finally, another customer need dealing with functionality is a vacuum that has a long lasting battery life The rest of the customer needs that we found had to do with the design and specifications of the vacuum cleaner. The most important customer need in this regard, is a vacuum cleaner that is lightweight. Along with being lightweight, having an ergonomic and comfortable grip was another important customer need Target Audience One group that was surveyed about the usability and design of handheld cordless vacuum cleaners were the parents of all three group members. We asked our parents mainly because they each have different experiences using vacuum cleaners. Some parents routinely use vacuums to clean around the house on a daily basis. However, some other parents used vacuum cleaners in garages, woodworking areas or in other heavy duty areas. Surveying users who have vacuumed in various atmospheres allowed us to find customer needs for a vacuum cleaner that would be sufficient for a very broad yet demanding spectrum of users. We also looked at cordless handheld vacuum cleaner product reviews on as a way of gathering customer needs. We felt this was a great place to look because of the fact that every person who was writing a review had used the product before, and had specified what they liked about the product, or if there were other customer needs that could have been met, but were not. Due to the fact that we surveyed and gathered information from a diverse group of people, who have all vacuumed in various atmospheres, we believe that our sample adequately characterizes our intended customer market. 6

7 3. External Search and Benchmarking The purpose of this section is to discuss the fact that we have researched and now understand some notable handheld cordless vacuum cleaners that are currently on the market. This section also aims to discuss the specific segment of the vacuum cleaner market where we envision our product competing. This section will also discuss and analyze specific models which will be likely competitors Research on Existing Products Upon researching current handheld cordless vacuum cleaners that are currently on the market, there were a few general aspects that applied to nearly all the best-selling vacuum cleaners. Firstly, it was noted that many handheld cordless vacuum cleaners are canister vacuum cleaners and not filterbag vacuum cleaners. This basically means that the dirt and debris that is collected within the vacuum is held in a simple hollow canister rather than a filter bag. It appears as if most of the new vacuums use a canister to hold the dirt and debris, while older and larger vacuums appear to use filter bags. However, many canister vacuums have filters, but these filters are washable and can be reused many times before needing to buy a replacement. The general consensus is that canister vacuums are much easier to clean and maintain, and it lowers the long run cost because filter bags do not need to be continually purchased. This trait of new handheld cordless vacuum cleaners is important to understand because it seems the most competitive companies are using canister techniques over filter bags. Another common aspect that many popular handheld cordless vacuums had was that they used Lithium batteries instead of Nickel Cadmium batteries. After conducting more research on these types of batteries, it appears that Lithium batteries are more commonly used in smaller vacuums because they are lightweight, smaller, and they have no self-discharge (which means they do not lose power as quickly and have a more steady lifetime). However, many of the vacuums which used these batteries tended to be more expensive [1] Intended Market Segment Although the handheld cordless vacuum market is very close to being in the perfect competition phase (nearly identical products at similar prices), there still seem to be a few specific market segments. One segment is the side of the market that appeases to consumers who are willing to spend money on more known name brands (such as Hoover, Dyson, etc.). While these vacuums received positive costumer ratings, some of the ratings were not much higher than vacuums that cost half as much money. However, as seen in many other types of technology markets, there are many customers who buy products simply off of the name brand, and their aesthetic preferences. Many of these vacuums fell within a price range of 70 to 240 dollars. After conducting this research on this specific market segment, it is clear that our vacuum will not be intended for these consumers. Seeing as our budget for this project is a mere 30 U.S. dollars, our product is aiming to compete with handheld cordless vacuum cleaners that are between 30 and 70 dollars. Despite the lower price, many of the vacuums that were in this price range also received positive views. The lower price and high ratings lead us to believe that these vacuums appeased to customers who were looking for the best value vacuum cleaners. This is a market segment where the consumers are looking for a practical and low cost vacuum that will simply get the job done effectively. This is the market segment that we envision our product competing in. 7

8 3.3. Descriptions and Specifications of Three Competitors The first possible vacuum cleaner that we could compete with was the Black and Decker CHV1510 Dustbuster. This is a bag-less, handheld cordless vacuum cleaner for a price of 44 dollars. This vacuum uses a lithium battery that, once fully charged, is able to hold a charge for 18 months. Although the vacuum uses a lighter Lithium battery, the overall weight of the vacuum was 4 pounds (a little heavier than some vacuums that used a Nickel Cadmium battery). The vacuum uses a 15.6 volt battery, although according to Black and Decker s website, the vacuum uses about 14.4 volts. The canister capacity is 20.6 ounces and it uses a reusable and replaceable canister filter. This vacuum also uses an effective power of 18.2 watts. It is recommended that this vacuum be charged for at least 24 hours before use [3]. Another vacuum that we found could be a competitor in our intended market segment was the Dirt Devil Accucharge Vacuum. This vacuum cleaner is also a bag-less vacuum cleaner that can be purchased for 45 dollars. This particular vacuum has a total weight of 3.25 pounds and it uses a Nickel Cadmium battery and also has a 15.6 volt battery. This vacuum cleaner has a full charging time of only 6 hours. Also, the vacuum uses reusable and replaceable canister filters [4]. The third vacuum that could potentially be within our market segment is the Shark Pet Perfect II Hand Vac. This is a bag-less handheld cordless vacuum cleaner for a price of 52 dollars. This vacuum uses an 18 volt Nickel Cadmium battery and it has a charge time of about 16 hours. This vacuum weighs about 5.8 pounds most likely due to the fact it uses a more powerful and heavier Nickel Cadmium battery. This vacuum uses reusable and replaceable canister filters, just like the other vacuums [5] Patent Search Some of the newest and most revolutionary patents on vacuum cleaners are filed by Dyson. Dyson has a reputation for holding a variety of complex patents and integrating that technology within their vacuum cleaning products (they have hundreds of patents). However, many of these patents are very complex and use high technology and innovative/expensive design in order to function. With this being said, it is clear that we do not have the funds or technology to mimic these ideas and that a full patent search will not be necessary. However, it is still important that when we start developing handheld cordless vacuum concepts that we try continue to do patent research to make sure we are developing unique and original ideas that would not violate patent laws [6]. 8

9 4. Design Specifications The purpose of this section is to state the design specifications for our vacuum project. Included in this section are the engineering specifications (with appropriate values and metrics) and the ranking system used to determine which specifications are most important Design Specifications In order to determine the design specifications, we first looked at the needs of our customers, including any latent and unstated needs. Customer needs are not exact specifications so it was our job to attach specifications that could be quantified to each need. These needs and specifications can be seen below in Table 1. Table 1: Quality Function Deployment Lbs. of rice per min Motor speed Measured decibels Weight Suction Power X X X Quietness X X Works in Nozzle dimensions Canister Dimensions corners X Battery Life X X Light weight X X Comfortable X X X X Easy to clean X Hours of usability Target Values 0.5 lbs. > RPM < 70 db < 7 lbs. 2 in 5 in 30 min An important thing to note about Table 1 is the target values attached to each specification. These are values that can be physically tested and will allow us to determine if our vacuum satisfies the customer needs. Each value was determined through research, often times by examining other similar products. Our target value for pounds of rice per minute is a goal that we have set for our vacuum. Since we will be testing how well our vacuum can pick up rice, we feel that 0.5 lbs. of rice in a minute is an obtainable goal. The motor speed was determined through comparison of other vacuums in the market now. Most impellers spin faster than 10,000 RPM. This is a reachable speed for our product. The motor and impeller speed contributes to many factors including the suction power, the quietness, and how comfortable the vacuum is to use. As specified in our customer needs section, our vacuum has to be quiet enough to hear a phone ringing while in use. That is where a specification of less than 70 db was determined. The weight also needs to be less than 7 pounds so that it is not too heavy to hold for extended periods of time. The nozzle size was set at 2 inches so that it could be used in tight corners. The reduction in size also helps to contribute to a higher flow velocity at the nozzle. The canister needs to be 5 inches wide to allow for ample storage of refuse without being too large. The size also allows for 9

10 the canister to be easily cleaned. The battery needs to run for at least 30 min without dying. It does not need to run that long as this vacuum most likely won t be used for multiple hours at a time Weighted Selection After the specifications were fully determined we developed a weighted scale to determine which specifications were most important. To create a weighted scale, we used a process known as the analytical hierarchy process. This process involves assigning a number based on the importance of one specific factor compared to another specific factor. The scale is laid out so that a 1 represents that the 2 factors are of equal importance. The scale continues to increase up to 9, which represents that the factor is of extreme importance when compared to the other factor. The numbers are then added up to calculate the total for that factor. When this total for the factor is divided by the overall total points, it returns a weighted rank for each factor. Our analytical hierarchy process can be seen below in Table 2. Table 2: Analytic Hierarchy Process Ranking Suction Quietness Size Battery Weight Easy to clean Total Rank Suction Quietness Size Battery Weight Easy to clean Black Box If this vacuum were to be viewed as a black box it would have the inputs of: energy, dirt and air, and the trigger input. Within the black box, the inputs could be divided into subsystems of: energy storage and energy conversion to rotational energy; dirt storage and exhaust gas; and variable speed control. These subsystems and inputs work together to produce a canister of dirt. This black box system can be visualized in Figure 2. Figure 2: Black Box 10

11 5. Concept Generation This section describes and illustrates three feasible concept designs for our handheld cordless vacuum cleaner. It includes both descriptions and drawings of these concepts. Within this section, we also explain the important subsystems of the handheld cordless vacuum. Finally, this section also provides our concept generation process and methodology Concept Generation Process We used a methodological concept generation process to ensure all ideas were properly documented and analyzed. First, group members started generating their own ideas for either specific subsystems or complete concept designs. These ideas were then recorded on index cards, which were separated into different categories. These categories eventually helped us formulate the vacuum s subsystems. Every team member was then given three votes to disperse among the different concepts, which helped eliminate some of the ideas. The remaining concepts were organized into a Concept Combination Table (Table 1) that each team member used to create a complete concept. In the end, the team had three feasible design alternatives. Table 3: Concept Combination Table Nozzle Impeller Canister Filter Trigger Inner Tube Axial Twist Off HVAC Behind Motor Upper Pipe Centrifugal Slide Off Rice Strainer Below Motor Door Cloth Mesh 5.2. Concept Subsystems Our concept designs can each be broken into five important subsystems: the Nozzle, Impeller, Canister, Filter and Trigger. The nozzle subsystem includes the design and the specific functionality we would like the nozzle to have. The impeller subsystem describes exactly what type of impeller could be used within the vacuum cleaner. The canister subsystem describes how the rice could be collect and removed from the vacuum. The filter subsystem simply describes the type of filter could separate the rice from the air stream. Finally, the trigger subsystem describes the various locations where the trigger could be located on the vacuum. Nozzle: -Inner Tube: On the inside of the nozzle, a hollow cylinder will be placed on the mouth of the nozzle. This inner tube will prevent debris from coming out of the vacuum cleaner if it is tipped forward. If the vacuum is tipped, the rice will be trapped between the vacuum s lower housing and inner tube. 11

12 -Upper Pipe: Air flows through the top of the vacuum s housing until it reaches the canister. Once the rice hits the filter, it will fall into the canister due to gravity. Impeller: -Axial: An axial impeller blows air axially due to the blade s geometry (figure 3). -Centrifugal: A centrifugal impeller blows are radially due to the blade s geometry (figure 3). Figure 3: Impeller Design Canister: -Twist Off: The canister has the ability to be loosened or tightened by twisting the canister clockwise or counter clockwise. The canister will have a threaded design (like a nut and bolt). -Slide Off: The canister will have edges and or grooves that will allow it to slide off of the rest of the vacuum cleaner. The sliding will be done is a single axial direction. -Door: The canister will have a hatch or a door on the bottom that can open to let out the contents. The canister itself will be permanently attached the vacuum. The door can either use a hinged, threaded or a sliding design. Filter: -HVAC: An HVAC filter will be used as the filter within the vacuum cleaner. -Rice Strainer: The filter will be taken from part of the filter that is used in standard household rice strainers. Only the filter portion will be used, and the material can either be metal or plastic. -Cloth Mesh: A mesh filter will be custom made from a cloth material. Trigger: -Behind Motor: The trigger that controls the power to the vacuum will be located at the same height as the motor and directly behind it. -Below Motor: The trigger that controls the power to the vacuum will be located directly underneath the motor. 12

13 5.3. Concept Designs Our first concept (figure 4) includes a conical inner tube nozzle and a centrifugal impeller. The canister will use a threaded twist off design, and a section from a rice strainer will be used as the filter. This design concept calls for the trigger system to be located towards the back of the vacuum cleaner below the motor and the canister. This concept will use an angled filter that is located upstream of the impeller and downstream of the canister. The canister will be of cylindrical shape and will be attached to the bottom of the vacuum cleaner vertically. The idea is to have the angled filter located above the canister so that when rice enters the nozzle due to the negative pressure created by the impeller, the rice will bounce off the angled filter into the canister below it. If any rice sticks to the filter it will fall directly into the canister once the vacuum is turned off. The inner tube design of the nozzle will prevent any rice from falling out if the vacuum is tipped forward. Figure 4: First Concept Our second concept (figure 5) also contains a nozzle with a smaller diameter tube to prevent dirt from falling out when the vacuum is tipped forward. This concept has a dirt canister that also acts as the nozzle. It unscrews so that dirt can be emptied. At the back of the nozzle is a cloth mesh filter to prevent any dirt from entering the impeller/motor area of the vacuum. The axial impeller is behind this filter with exhaust slits cut into the side of the vacuum to allow air to exit the vacuum. The axial impeller is actually perpendicular to the filter and forces the air to make a ninety degree turn before it exits the vacuum through the exhaust. Finally the trigger and battery are located behind the impeller for easy access and to counteract the weight of the long nozzle. This also gives us the opportunity to utilize the drill s housing for the vacuum s handle. 13

14 Figure 5: Second Concept Our third concept (figure 6) contains the Upper Pipe nozzle design. After flowing through a pipe at the top of the vacuum, the rice will fall to the bottom of the canister due to gravity. The canister is emptied via a door that slides off. The HVAC filter, used extensively in the heating and air conditioning industry, will keep any rice or dust from contacting the impeller or exiting through the exhaust. The centrifugal fan will force the air out of a single exhaust at the top of the vacuum away from the user s hands. By having only one exhaust outlet, it will be easier to control and analyze the vacuum s flow path and rate. The vacuum s handle and trigger are behind the motor to avoid any awkward right angles in the design. These right angles could make it difficult for users to reach small nooks and corners. Figure 6: Third Concept 14

15 6. Concept Selection The purpose of this section is to proclaim and discuss our selected concept for our handheld cordless vacuum cleaner. This section will also aim to justify the methodology we used to select our specific concept. We will do this by providing results of our decision matrices as well as justifying the numerical rankings that we labeled each of our concepts with Selected Concept We first created a matrix that would return weighted values for each selection criteria. The criteria were mostly based on customer needs, but we also included criteria that were important to us such as Manufacturability. We used an analytic hierarchy process (AHP) to weight the criteria for our vacuum. These weights were determined by comparing criteria directly against each other. Using an AHP allowed us to visibly see which criteria is most important and should be focused on the most when choosing a concept. Our AHP can be seen in Table 1. Table 4: Analytic Hierarchy Process for Concept Selection After the weighting process was finished, we compared our three concepts from our concept generation process in order to select a final concept. The overall results for our concept selection can be seen in the decision matrix in Table 5. It shows how the weights from the AHP were used with the ratings for each concept in order to develop a final score for each concept. The ratings were determined by comparing a concept directly against the other concepts. A rating of 3 signifies that the selection criteria for that concept is average in comparison to other concepts. A rating above 3 means that a criteria is above average and a rating below 3 means that a criteria is below average. The ratings are then multiplied by the weights of the criteria and summed to determine a final score for each concept. After analyzing this data and discussing our results, we came to the unanimous decision that concept 1 is our best concept. 15

16 Table 5: Concept Decision Matrix An early SolidWorks model can be seen in Figure 7. Our selected concept includes a conical inner tube nozzle that includes a centrifugal impeller design. The canister will use a threaded twist off design. Although the original concept called for a rice strainer as a filter, we have agreed to use a cloth mesh filter instead. This design concept calls for the trigger system to be located towards the back of the vacuum cleaner behind the motor and the canister. This concept will use an angled filter that is located upstream of the impeller and downstream of the canister. The canister will be of cylindrical shape and will be attached to the bottom of the vacuum cleaner vertically. The idea is to have the angled filter located above the canister so that when rice enters the nozzle due to the negative pressure created by the impeller, the air can pass through the filter but the rice will bounce off the angled filter down into the canister below it. If any rice sticks to the filter it will fall directly into the canister once the vacuum is turned off. The inner tube design of the nozzle will prevent any rice from falling back out if the vacuum is tipped forward. Figure 7: SolidWorks Exploded View 16

17 7. Theoretical Analysis All calculations in this analysis will assume a steady flow, incompressible flow, uniform velocities at the vacuum s inlet and outlet and a rigid housing. These assumptions imply that mm iiiiiiiiii = mm ooooooooooooand QQ iiiiiiiiii = QQ oooooooooooowhere mm is the mass flowrate and QQ is the volumetric flowrate Requirements for Flowrate In order to pick up rice, the velocity at the inlet needs to be at least 4000 ft./min or 6000 ft./min. This can be converted into a volumetric flowrate by using the following equation: QQ = vv AA. Equation 1 For equation 1, Q is the volumetric flow rate in ft 3 /min, v is the velocity in ft./min and A is the area of the inlet in ft 2. The volumetric flowrate was calculated using equation 1 with a wide range of inlet crosssectional areas ranging from.002 ft 2 to.015 ft 2 and a range of inlet velocity values ranging from 4000 ft./min to 6000 ft./min. With these numbers, the required volumetric flow rates ranged from 8.3 cfm to 73.6 cfm. The fan static pressure can be calculated by using the equation: SSPP ffffff = PP 8.52 NN ff. Equation 2 QQ For this equation, SSPP ffffff is the static pressure in inches water gauge (w.g.), P is the drill mechanical power in watts, NN ff is the fan efficiency, and Q is the volumetric flowrate in cfm. The maximum mechanical power output from the drill dissection data was used for P. This value was 70 watts. SSPP ffffff was calculated using equation 2 for a variety of inlet velocities, inlet diameters and fan efficiencies ranging from.5 to 1. SSPP ffffff ranged from 72 in. w.g. to 8 in. w.g Impeller Specifications The current design uses an 8 blade backward curved airfoil with a 4 inch diameter and a 21,600 rpm. The design is based on a Continental Fan Manufacturing Inc. design. The fan has a 7.12 inch diameter, 3450 RPM, an airflow of 250 cfm and a static pressure of 2 inches w.g. For a constant diameter, the relevant fan affinity laws are QQ 1 QQ 2 = NN 1 NN 2 and HH 1 HH 2 = NN 1 NN 2 2. For constant shaft speed, the relevant fan affinity laws are QQ 1 QQ 2 = DD 1 DD 2 3 and HH 1 HH 2 = DD 1 DD 2 2. (please note that fan affinity laws are not the same as pump affinity laws). N is the rotational speed, D is the diameter and H can be either pressure or head. Since this design varies both in terms of diameter and rotational speed, Continental Fan Manufacturing Inc. s design must be scaled twice. Therefore, the relationships become: QQ 1 QQ 2 = DD 1 DD 2 3 ( NN 1 NN 2 ). Equation 3 HH 1 HH 2 = DD 1 DD 2 2 NN 1 NN 2 2. Equation 4 17

18 By using the variables defined above with equations 3 and 4, the volumetric flowrate for the vacuum s impeller is 278 cfm and the static pressure is 24.7 inches w.g. The impeller s volumetric flowrate is much higher than what is required. At this high of a flowrate, the required static pressure should decrease significantly. Therefore, the static pressure also satisfies the requirements. Overall, theoretically, the impeller should create a powerful vacuum that can accomplish the task even with added frictional losses Minor Losses Generally, major losses can be neglected if the length of a pipe divided by the diameter of the pipe is less than 50. Since the current design has a pipe length of about 10 inches and a pipe diameter of 5 inches, the major losses can be neglected. Therefore, the equation for total pressure loss is: pp = kk ρρvv2 2. Equation 5 k is the minor loss coefficient and ρ is the density of air. In the current design, there are 5 sections that will result in minor losses labeled in Figure 8 as a, b, c, d, and e. Figure 8: Minor Loss Locations Location a is going from a ft 2 cross-sectional pipe to a 5 inch diameter pipe. For this section, k= 1 AA iiiiiiiiii AA oooooooooooo 2 = Location b is a flow branch which has a minor loss coefficient equal to 0.3. Location c is the filter. Currently, the design uses a car air filter rated for cfm at a pressure decrease of 1.5 inches w.g. Since the actual flowrate is much smaller than this, 1.5 inches is a worst case scenario. Location d is a 90 degree bend which has a minor loss coefficient equal to 1.3. Location e is an outlet to an open room so is will have a coefficient equal to 1. Equation 5 now becomes pp = (kk aappvv aa 2 ) 2 + (kk bbppvv bb 2 ) 2 + (kk ddppvv dd 2 ) 2 + (kk eeppvv ee 2 ) iiiiiiheeee ww. gg. The inlet velocities at different sections of the pipe can be easily calculated by using the fact that mm iiiiiiiiii = mm oooooooooooo. Using this equation with the necessary unit conversions leads to the following data: at an inlet speed of 4000 ft./min, p = 2.52 to 2.56 inches w.g., at 5000 ft./min, p = to and at 6000 ft./min, p = to inches w.g. The range in the results is due to using a range of inlet cross-sectional areas. Overall, the pressure losses are smaller than every predicted static pressure. These values do get close at large inlet areas though, the closest being with 4 inches w.g. This means that the vacuum s inlet area should not be larger than.015 ft 2 to be safe. + 18

19 8. First Prototype Evaluation The purpose of this section is to explain and analyze our first prototype for our handheld cordless vacuum cleaner. Within this section we will discuss the materials that were used to construct our first prototype, as well as the construction process itself. Next, this section will detail the testing that was conducted with this first prototype, and analyze the results of said testing. Finally, this section will discuss the pros and cons of our first prototype, while including various ways that the prototype could be improved upon Materials and Construction Process The first step in our production/construction process was designing and physically producing a radial impeller. This was the first step in the construction process because we wanted to have an impeller to build the housing around. The impeller was designed using SolidWorks, and the final file was 3D printed using the Makerbot printers in the Reber Building. After receiving the finished impeller, we took apart the drill and removed all the gear stages. We then used the drill press in the Learning Factory and drilled a 7/16 inch hole in the center of the impeller so it could be directly attached to the motor gear. Originally, we used a 4 inch diameter impeller but we quickly realized that this would make the vacuum too large. We changed the impeller diameter to Figure 9: 3 Inch Diameter Impeller 3 inches as shown in Figure 9 which led us to use 4 inch PVC piping for our motor/impeller housing. While the plan was to use the entire drill s housing for the motor/impeller housing, it became problematic to attach the PVC pipe to drill s housing while keeping the motor concentric with the pipe s shaft. Therefore, we had to design a way to attach the motor to the PVC pipe. Figure 10: Motor Mount Design The second step was to create housing for the motor. In order to center the motor within the housing, we cut out two doughnut shaped pieces of acrylic using the laser cutter in the Learning Factory. This design is shown in Figure 10. These pieces will function as a motor mount. We cut the outer diameter to 4 inches so it could fit snug within the PVC piping, and the inner diameter was cut to 1.5 inches, so the motor could fit perfectly through. By attaching two of these pieces to the motor, the motor could not move up, down or side to side. By attaching one of the motor mounts to the part that originally connected the motor to the clutch s housing, the motor was 19

20 stopped from moving axially, too. These will also ensure that no air travel s behind the motor shaft and that the airstream is directed towards the exhaust. Figure 11 shows the motor mounted to the PVC piping. Figure 11: Mounted Motor The third step was to add the necessary holes to the PVC. First, a 1-⅞ hole was drilled for the canister. Secondly, a variety of other holes were drilled for the exhaust. The fourth step was deciding what to do with the battery and trigger. Due to the fact that we were primarily focused on the functionality of our prototype, we decided to keep the trigger and battery system out of any housing. The fifth step was to create the filter. We originally planned to use an old car air filter, but initial testing showed that this blocked significant airflow. For this prototype, we created a filter by cutting a piece of plastic from a soda bottle and drilling many holes through it as shown if Figure 12. Figure 12: Air Filter The final step was to attach all the different parts to the PVC Housing. This was accomplished by mostly using duct tape because it can be easily removed and modified. The nozzle, and the motor mounts, were held to the housing using duct tape. The nozzle was made out of the top of a 2 liter soda bottle simply because it was an easily available item and it has the generic shape of a vacuum cleaner nozzle. The complete prototype can be seen in Figure 13. Figure 13: Complete Prototype 20

21 8.2. Performance and Results After completing the prototype, we first wanted to see if the prototype worked at all. When we turned on the impeller and pressed our hand to the nozzle, we discovered that there was a noticeable amount of suction. We then tried to suck up tiny pieces of shredded notebook paper. After ripping up the paper, we piled them onto a surface high enough such that the paper pieces were level with the nozzle. We then placed the nozzle about 1.5 inches away from the paper and slowly pulled the trigger. When the impeller was running at approximately half its total speed, we were able to barely suck up these pieces of paper. When we increased the power, we were able to quickly suck up these pieces of paper for about a second. After a second, the impeller fell off the motor shaft. To keep the motor and the impeller from becoming damaged, we decided to not run the impeller over half speed for further tests. We decided to run a very similar test but without the filter. At low speeds we were just able to generate enough suction to suck in pieces of shredded paper through the nozzle. As we slowly increased the speed of the impeller the suction continually improved. The vacuum was significantly more powerful without the filter. Since we could not run this prototype at full speed, we could not conduct detailed tests. Still, these tests greatly helped us troubleshoot our design. It is obvious that we need to make significant improvements to the filter and to the connection between the impeller and the motor shaft Positive and Negative Aspects There are several aspects that worked very well. The PVC pipe worked well as the housing because it was sturdy and looked professional. The motor mounts also functioned and looked professional. These pieces did a very good job at keeping the motor and impeller centered within the housing. We were also surprised that drilling a hole into the impeller and sticking it onto the motor worked at all at low speeds. Overall, this prototype showed that we are capable of building a functional vacuum. There are several things that need work. First, some of the exhaust holes need to be redesigned. Some are not safe (someone could stick a finger through them) and they were drilled in an unorganized manner. Secondly, we need to rethink the filter. The current filter slows down the airflow too much. Thirdly, the trigger and battery system are uncovered at this point, which makes the prototype cumbersome to hold and unprofessional looking. Fourthly, as stated earlier, at very high speeds the impeller would fall off of the motor. Fifthly, we will need to eliminate all the duct tape from our final design entirely. Finally, this prototype did not let us test some of our more innovative ideas. For example, this prototype did not feature the inner tube or the screw-off canister 8.4. Plan to Improve Prototype This basic prototype has helped us learn about the practicality of our design. There are also several bugs in this prototype that will need to be corrected for the next prototype. We have devised a five step plan to improve this design. Our first step to improve the prototype is to find a more secure way to attach the impeller to the motor. Due to the fact that the impeller fell off at high speeds, we are considering cutting the shape of the motor s spindle into the impeller so we can get a more perfect fit. Our goal here is to have the 21

22 impeller fit securely enough so that when the motor runs at full speed the impeller will remain on the motor. This would essentially work like a press fit. Our second step to improve the prototype is to create housing for the trigger and battery system. We plan to do this by using the original drill housing. However, we will only use the handle part of the drill housing and we will remove the motor housing section. This handle will be attached to the bottom of the prototype, directly below the motor. Our third step is to find a more functional and professional looking nozzle. In order to utilize the best nozzle for our vacuum we will most likely design and 3D print it as we did with the impeller. The inner tube will be 3D printed with the nozzle. Fourthly, we must include a better filter. The current filter significantly impeded airflow. At the learning factor there is free wire mesh that we can use as a filter. On inspection, the holes looked small enough such that rice could not pass through. The wire mesh also appeared to impede airflow less than the current filter. Improving this filter will also allow us to attach and test our canister idea. Finally, the last way to improve our prototype is to eliminate all duct tape by using screws, fasteners and epoxy to connect parts and hold everything in place. This will look more professional and also allow us to test the strength of these connections. Overall, the prototype has given us insight into the various components of the design. The knowledge gained will dramatically improve our final project. 22

23 9. Component and Material Selection The purpose of this section is to document and discuss the specific materials and components that should be used in the final mass produced handheld cordless vacuum cleaner. This section will also document certain off the shelf parts that could be included in the final product. This section also aims to assess the potential environmental effects due to specific materials and components that will be used. Finally, detailed drawings of specific parts will also be included within the appendix of this section to aid in the documentation and visualization of our design choices Components and Materials When examining our design for the handheld vacuum cleaner project it is important to realize that the outer housing, nozzle and canister will require the most material to produce. It is also important to realize that all three of these parts can basically be made from the same type of material. For these three components in particular, an acrylonitrile-butadiene-styrene (ABS) plastic should most likely be used. These parts would be produced by using injection molding within a two part steel mold. ABS plastics would be the best for this design because it is tough, light-weight and cheap compared to other strong plastics. Also ABS is a good choice because any time a defective or unwanted part is made, the ABS can simply be re-melted and re-used for another part in the vacuum, thus minimizing waste. The inner motor holder rings could also be produced using ABS plastic and they could even be included in the housing mold to speed up production. The inner motor holder rings could also be made out of acrylic or polycarbonate as well, however they would not be able to be included in the housing mold, and thus production would be slower and more expensive Common off the Shelf Parts There are a number of common off the shelf parts that will be used on our mass produced device. One of the most frequently used off the shelf parts that we will use is various screws. These screws will be placed at various locations and will primarily be used to hold major components to the main housing. Screws will be used to fasten the nozzle to the housing so that it does not come unattached and fall off, especially when vacuuming at a downward angle. The end cap will also be screwed to the housing so that it cannot be separated from the housing. It is important that the end cap does not become separated because the end cap is responsible for containing and protecting the motor and impeller. Without the end cap, the motor and wiring will be exposed which could be dangerous for the user and the vacuum. We will use 6-32 type 316 stainless steel pan head Philips screws. These screws are cheap, reliable, and easy to remove if maintenance is necessary. Another off the shelf part that we will use are various sizes of rubber O-rings. These O-rings will be used to create a seal around components that attach to the main housing of the vacuum. The O-rings will ensure that the housing is air tight. This will in turn create better suction and overall better performance. Plastic mesh will also be used as a filter. This mesh can be purchased from a number of manufacturers in large sheets. These sheets can then be cut down to the required size and used as filters. Parts from a drill master 18V drill will also be used. These parts include the motor, trigger mechanism, and handle. Finally, the last off the shelf part that we will be using is a 2 part 3M adhesive. This adhesive will be used to secure the component of our vacuum used to center our motor. If they were made from acrylic or polycarbonate, these rings could slide freely inside the housing without the adhesive. Adhesive was chosen over screws since the rings do not have enough thickness to screw into the housing. 23

24 9.3. Environmental Impact We are going to attempt to minimize the environmental impact that our vacuum causes. The housing, nozzle, end cap, and canister are all made of ABS plastic. ABS plastic is recyclable so these components can be reused once they have reached the end of their lifetime. Another way we plan to minimize our environmental impact is by using smart packaging to distribute our product. This packaging will be made out of recycled cardboard and recycled plastic. The canister and battery will be packaged unattached from the main housing in order to save space in the packaging. Unfortunately, our vacuum uses some components that are not environmentally friendly. For example, our vacuum uses a nickel-cadmium battery. This battery could potentially be harmful if not disposed of properly. Because of the project requirements, the battery and motor cannot be changed for a more environmentally safer option. Overall, the design and packaging will be made out of mostly recyclable materials which will minimize the overall environmental impact. 24

25 10. Fabrication Process The purpose of this section is describe the fabrication process for our cordless vacuum cleaner. This section explains the methods that will be used for mass production, not the prototype. There are also images detailing the parts of the vacuum (Figure 14) as well as an assembled view (Figure 15) Creating the Individual Parts The fabrication and production of our vacuum will be relatively simple to limit manufacturing errors. An exploded view of all the parts can be seen in Figure 14. Screws and the trigger system are not included in the exploded view. The first step of the fabrication process is to create the nozzle, housing, and the impeller. These parts will be created using an injection mold. Injection molds are used in many industries to create plastic parts. Essentially, it uses a device called a ram to Figure 14: Exploded View force the molten thermoplastic into the mold cavity. For this design, all the molds will be made from a tool steel because it can withstand a high production rate. Two separate molds will be needed to create the housing to ease the assembly process. Each mold will encompass one half of the total housing and these halves will mirror each other. Please note that Figure 14 already shows the two housing pieces assembled together. Therefore, four molds will be needed in all: one for the nozzle, one for the impeller and two for the housing. Injection molding allows for the production of a large volume of parts in a short amount of time, which will help produce vacuums at an efficient rate. Five parts will be bought from suppliers. These parts are the wire-mesh filter, the motor, the battery, the screw-off canister and the trigger system. The motor, battery and trigger system can be bought from the same company that supplied these parts for the 18V drill. Wire-mesh filters and canisters are fairly common and can be bought from many suppliers such as McMaster-Carr Assembly Process The vacuum is designed for a four-step assembly process. 1. The impeller will be press fitted onto the motor s sun gear. The impeller has the outline of the gear cut into its center. Since the impeller is relatively fragile, a rubber mallet should be used to complete this press fit. 25

26 2. Secondly, one half of the housing will be laid down with the internal cavity facing the worker. This will allow the each component of the vacuum to be placed into the housing. The motor is placed into the exposed half of the donut shaped motor mounts. The screw, which connects the motor to one of these mounts, should also be assembled at this time. The trigger system can be placed into the exposed half of the handle. Finally, the filter can be placed at a 60- degree angle above the screw-off canister. The filter will be attached to the plastic housing using a permanent adhesive, probably a type of plastic adhesive. 3. The second half of the housing will be carefully attached to the other half of the housing using a plastic adhesive. Using a permanent adhesive will ensure a tight bond between the two housing halves, which will help lower pressure losses. A permanent adhesive will also be needed to secure the filter to the other half of the housing. 4. The last step is to attach the nozzle. The nozzle is attached to the housing by using four, equally spaced screws. While the user can easily take the nozzle off, the impeller and motor cannot be easily reached once the vacuum is completely assembled. This is a direct effect of wanting to combine the filter and impeller housing. Since the filter is permanently attached to both halves of the housing, these halves could not be assembled simply using screws. Instead, the two housing sections must also be held together with a permanent adhesive. Overall, this decision leads to harder repairs but simplifies the manufacturing process. A model of the assembled handheld vacuum can be seen in Figure 15. Figure 15: Assembled View 26

27 11. Safety The purpose of this section is to demonstrate that our handheld cordless vacuum cleaner meets or exceeds all relevant consumer product safety regulations for sale in North American and European markets. We will do this by clearly identify and cite the safety standards that our product complies with IEC & IEC Scope IEC safety standard is for household electrical appliances that have rated voltages below 250V for single-phase appliances. This standard is not for children s products. It assumes that young children will use the appliance with adult supervision and that it will not be used as a toy. Our vacuum cleaner falls into this category. It has an 18V motor which is below 250V and it is intended to be used by adults in a household. IEC is the standard specifically for vacuum cleaners. Our vacuum cleaner would need to pass both standards before being mass produced [7] Requirements There are many aspects to IEC Many of them involve standards for the instruction manual to label voltages, power inputs, etc. correctly. We assume that our part will meet these standards when the product is mass produced. Also, since the motor comes from a vendor, we know that it will meet its required safety standards. Our vacuum cleaner must follow the standard s protection against live parts requirements. This requires that any moving parts such as the impeller and the motor cannot be touched by the user unless he or she completely disassembles the part. For our design, the exhaust and ventilation holes are small enough such that no fingers can pass through them. This protects the user from accidentally touching the impeller or the motor. When the user unscrews the canister, the wire mesh filter also stops the user from accidentally touching the impeller. IEC also has some specifications on heating. It ambiguously requires that appliances must not generate excessive temperatures in normal use [7]. The standard also makes some more specific references to the required maximum motor temperature. To help keep the motor cool, ventilation holes were added to the back of the design. The plastic doughnut shaped pieces mounting the motor to the housing does not impede this ventilation. Our vacuum is also designed to withstand abnormal use as specified in the standard. Generally, we believe that if the user decides to hold the vacuum not by the handle or use the vacuum in any reasonable abnormal way, the vacuum will not endanger the user. Most of the dangerous equipment is protected by ABS plastic, which is sturdy and will be able to withstand any rough handling by the user. While there are a few other requirements in this standard, the ones listed above are the most relevant to our vacuum. We know any parts taken from the drill will meet the required safety specifications because the handheld drill met its safety specifications. While hand-held motor electric motor tools use the standard IEC instead of IEC , the standards are extremely similar and the drill design appears to meet both standards. 27

28 11.2. IEC Scope IEC safety standard applies to enclosures for electrical equipment with a rated voltage that does not exceed 75 kv. This standard deals only with enclosures that are suitable for their intended use. (That is the claimed degrees of protection are maintained with normal use) [8] Requirements There are three key requirements within the IEC standard. The first requirement is sufficient protection of persons against access to hazardous parts inside the enclosure. This requirement is nearly identical to one of the requirements in IEC The analysis for why our vacuum cleaner would meet the requirement for IEC can also be used for the IEC requirement. The next requirement to the IEC is sufficient protection of the equipment within the enclosure against solid foreign objects. Due to the fact that our enclosure is simply housing for a handheld cordless vacuum cleaner, the inner electrical equipment is protected by a wire mesh filter. This filter is fine enough that it will prevent any solid foreign objects from coming in contact with the electrical equipment and damaging it. Also, the exhaust holes near the electric motor within the enclosure are small enough such that they will prevent any damaging solid foreign objects from coming in contact with the electric equipment. The final requirement states that there must be sufficient protection of the equipment inside the enclosure against any incoming water. Due to the fact that our vacuum is only used for dry cleaning under normal use, our vacuum should not come in contact with any water. However, if water were to enter the vacuum, the electric motor is placed in between two sealed plastic walls that should provide a watertight seal. This seal would prevent any water from coming in contact with the inner electric equipment within the enclosure. 28

29 12. Economic Justification The general purpose of this section is to economically justify production of our vacuum and describe whether or not it is a worthwhile investment by calculating the Net Present Value (NPV). This section will contain an analysis of the all-inclusive cost to produce a single unit when 100,000 units are mass produced. This section will also include a complete Bill of Materials (BOM) to aid in this analysis Bill of Materials Overview The Bill of Materials (BOM), which can be seen in Table 6, was produced by analyzing how much parts would cost individually. Material costs, labor costs and fixed costs were also incorporated into the BOM. Also included in the BOM is the overhead cost which includes other expenses such as development, marketing, maintenance, taxes and employee benefits. Cost analysis of each individual part is explained in subsequent sections. Table 6: Bill of Materials Part Vendor/ Part # Qty Material Cost ($) Labor ($) Fixed Cost ($) Total ($) Housing N/A K Battery + Charger Motor Assy Drill Master Drill Master Nozzle N/A K Impeller N/A K Filter Canister McMaster-Carr/ 922T966 The Cray Store/ 63B27W Screws Bolt Depot/ Packaging Drill Master Unit Production Cost Overhead Other expenses such as lighting, marketing, maintenance, taxes and employee benefits Total The total cost for each unit was calculated by determining how much an individual part would cost to produce if 100,000 units were produced annually. We had to take material costs, labor costs and fixed 29

30 costs into consideration. The costs for every part were then added together with overhead cost also incorporated. We predict that a fixed percentage of 15% of the unit production cost would suffice for our per unit overhead cost Injection Mold Cost Analysis For our design, the impeller, the housing, and the nozzle are created by an injection molding process. To help estimate the cost of these parts, we used CustomPart.net s Injection Molding Cost Estimator for 100,000 units. For one half of the housing, the material will cost about $123,917, production will cost about $21,213 and tooling will cost about $47,677. The total cost per unit would be about $ For the second half of the housing, the fixed cost should not be factored into the calculation. Therefore, the total cost for two units would be $ For the impeller, the material will cost about $27,084, production will cost about $25,663 and tooling will cost about $27,038. Therefore, the total cost per unit would be about $ For the nozzle, the material will cost about $75,811, production will cost about $26,406 and tooling will cost about $27,232. Therefore, the total cost per unit would be about $ All of these numbers have been added to the BOM (Table 6) Commercial Off the Shelf (COTS) Parts Parts that cannot be easily produced in house will be purchased from a supplier and shipped to our assembly plant. The six Commercial off the Shelf (COTS) parts are the motor assembly, the canister, the battery, screws, the filter and the packaging. It would be a waste of time and money for us to develop and produce these parts ourselves at this point. Parts such as the wire mesh filter and packaging will be shipped in bulk and trimmed and assembled by our employees. The six COTS parts will be bought from several suppliers several suppliers. The motor assembly and battery are part of the original drill made by Drill Master. It has been given (from the lecture notes) that the motor assembly, which includes the motor and the trigger, will cost about $1.80 with an assembly labor cost of $.10 per unit. The battery will cost about $2.50 with an assembly labor cost of $.05 per unit. Our vacuum s packaging will be similar to packaging used for the The 23 oz. screw-off canisters will be bought at The Cary Store where 1440 canisters can be bought for $0.665 each. Since we are buy almost 70 times more canisters, we expect a larger discount. For the purposes of this analysis, we will guess that the cost per unit will drop by about 50% which is probably a conservative estimate. Therefore, we will assume that the price will be about $0.330 each. The part ID number for this part is 63B27W. The assembly labor cost for the screw-off canister should be very cheap, so we estimated it at about $.05 per unit. The wire mesh can be bought in a large sheet from McMaster-Carr. According to McMaster-Carr, a mesh size of at least 8x8 is needed to filter rice. On McMaster-Carr, a 150x150 mesh size made with 304 stainless steel wire with a length of 100 feet and a width of 4 feet costs $9.92 per foot of length. This mesh will have the added bonus of also impeding dust. The part number on their website is 9226T966. Since the filter will need to be cut to about a 4 inch diameter circle, each vacuum will need a 12.6 square inch surface area of filter. For 100,000 units, about 8,750 square feet of mesh is needed which will cost about $21,700. Therefore, it will cost $.217 per unit. The labor cost should also be low and be around $.05. Finally, six screws are needed for our design. Four screws are used to connect the nozzle to the housing and two more screws are used to attach the motor to the housing. All of these screws will be 30

31 socket cap, Stainless steel 18,8 #4-40 screws with a ¼ length from Bolt Depot. The product number for this part is ,000 bolts will cost $ Taking the previous assumption that buying in bulk will decrease this cost by about 50%, each bolt will cost about $.009. Screws are also easy to assemble and the labor cost should be rather small. We estimate that it will be about $.05 per unit Price Analysis As shown in the BOM (Table 6), the vacuum will cost about $ to make. We would sell this vacuum to the distributor at a ⅓ markup or $ If the distributor and the retailer both markup the price by ⅓, then the final vacuum s final retail price will be about $30. After analyzing the unit cost and deciding what the retail price would be, we have decided that this product would be a good investment because it is a quality vacuum that generates more than sufficient suction, but still keeps other consumer needs in mind. The vacuum is comfortable to hold, lightweight and not noisy enough to block out ambient noise. The vacuum also has a competitive price. For example, Black & Decker have cordless vacuums that range from $21.99 to $44.99 and Dirt Devils can range from $29.99 to $ Since our vacuum falls within the beginning of this price range, we have an excellent opportunity to gain a strong consumer base Net Present Value Analysis Table 7 shows a quarterly profit predictions for the next four years assuming 100,000 units are sold each year. The table uses this information to calculate the net present value (NPV) assuming an annual discount rate of 10% or 2.5% a quarter. Development cost was estimated by first calculating the number of hours we have spent so far on the project. In total, we have spent 100 hours on this project with about 30 more hours of work for the rest of the semester. If our hourly wage was about $35.00 an hour (a typical entry level mechanical engineering salary), then our expenses will be about $4,550. Throughout the development process, we have used many tools that add to the development cost such as a 3D printer, a laser cutter, a drill press, etc. For the purposes of this analysis, we have decided to severely overestimate our expenses at $50,000 a quarter. We used this same value for the ramp-up cost which is the estimated costs associated with setting up production. In all, if we began ramp-up by mid-summer, we should have the product on the shelf by the beginning of next year. We used the overhead cost to estimate the marketing and support cost. This was estimated at about 15% of the total production cost. The total production cost per unit from the BOM and a projected sale of 25,000 units per quarter was used to calculate the total production cost. The unit price was based on a ⅓ markup and the assumption that we sold all 25,000 units. Period cash flow was calculated by summing the development cost, ramp-up cost, marketing, support cost, production cost and the sales revenue for each period. The Present Value was calculated by the following formula: PPPP = CC where PV is the present value, C is the period cash flow, r is the discounted rate per (1+rr) tt quarter and t in the current period. Present value is the value in today s dollars of expected future cash flows. Simply summing all the present values calculates the NPV. Our analysis shows a positive NPV of $286,272. Since this value is positive, the NPV value supports the notion of proceeding with development. Overall, this shows that the product will be profitable and is worth the company s investment. 31

32 Table 7: Total cash flows, present values and net present value 32

33 13. Industrial Design This section details and justifies the ergonomic and aesthetic features of the design. It proves that the design is easy to use and very safe. Finally, it includes all the anthropometric data for the customer Aesthetic and Ergonomic Features Overall, the vacuum his aesthetically pleasing due to very simple design. For example almost all of the vacuum s main components are located in a single housing unit that has a very simple, cylindrical design. At one of the ends of the cylindrical housing is the handle, which has a comfortable and ergonomic grip. The handle is optimized to help the user hold the device just like how the original 18V Drill Master s was designed. Tiny grooves are cut out into the handle to match a person s fingers. Also, a rubber section was added to the back of the handle where the user s palm would rest. This also helps the user grip the device. By using the same grip design as the original 18V Drill s, the vacuum is optimized for comfort. On the other end of the vacuum, there is a simple nozzle that is easily screwed on with 4 screws. In In the middle of the housing, the canister is the only part protruding which allows for a clean design as well as comfortable place for the user to place their other hand. Overall, we believe this simple design not only looks very elegant and easy to hold, but also ensures that the user will not be intimidated by the vacuum Simple Use The simplicity of our design also helps the user understand how to use the vacuum properly. In other words, the vacuum is very intuitive. The only necessary action to make the vacuum turn on is the pulling of the trigger on the back handle. The attaching of the battery is also simple and intuitive as it is attached to the bottom of the handle. This was purposely designed such that it matched the standard convention for cordless power tools. Anyone that has used or even seen a power drill will immediately understand how to attach the battery and work the vacuum. The screw off canister is also very simple to use. Anyone that has used a twist off lid should understand how to empty the vacuum once it becomes full. The vacuum also has a special feature to help the user reach nooks, crannies and other hard to reach places. The vacuums nozzle can be rotated ninety degrees by removing the four screws, rotating the nozzle, and reassembling the screws. With this set up, the handle would be parallel with the surface that is being vacuumed. This is especially useful for locations where the canister and handle might get in the way. Also, the ease of which the nozzle can be removed allows for the user to clean the inside of the vacuum in case any debris or dirt should clog the inside. Charging the battery is also a very simple task. All the user needs to do is press down on a red button on the battery and slide the battery off the bottom of the handle. Then they simply turn the battery upside down and slip it on to the charging dock in the same manner it is slipped on to the handle. There are two helpful lights on the charging station that help alert the user to current state of the battery. If the light is red the battery is still charging, when it turns green the battery is completed charged and ready for use. This simple procedure allows the user to get the most use out of their vacuum, for they will not waste time trying to figure out how to charge the battery, and they will know exactly when the battery is ready to go. Overall, these features help with the device s functionality while ensuring that the vacuum is simple to use. 33

34 13.3. Extremely Safe All the dangerous mechanical aspects of the vacuum are sealed to ensure that users do not accidentally injure themselves. One key safety aspect is that the exhaust and ventilation holes are too small for users to stick their fingers into. Most importantly, this stops any users from touching the impeller while it is spinning which could damage the impeller, but more importantly, the user s fingers as well. These small exhaust holes also prevent any user from damaging the motor or electrocuting themselves by directly touching the motor. The filter also protects the user from touching the impeller if the nozzle is removed. Clearly, the vacuum was designed to withstand usual and unusual use. The vacuum is also designed to withstand accidental water contact. If a small amount of water is accidentally suck up by the vacuum, it should not come in contact with the motor. This is due to the watertight motor mount that holds the motor in place. While water is not supposed to come into contact with the vacuum, the vacuum is still designed with a small safety guard in case of accidents Anthropometric Data The vacuum is inches long, inches tall and 4.50 inches thick. Overall, it weighs about 8 lbs with battery attached 34

35 14. Final Prototype Performance and Evaluation The purpose of this section is to detail the construction process and materials used to create our final vacuum prototype. This document will also explain the changes that our prototype has gone through to reach the point that it is at now. To support our reasoning for the changes from our original design, this section will describe concepts that worked well on a working prototype and concepts that did not work well or reach final production Construction Process/Materials Used Our final prototype was constructed from materials that were readily available to use from the Learning Factory. Our main vacuum housing is constructed of a single solid piece of 4 diameter PVC pipe. Above the impeller, exhaust holes (figure 16) were drilled using an electric drill and a ⅜ drill bit to allow air to escape the housing quickly and easily. Figure 17: Handle Figure 16: Exhaust Holes There is a hole near the end of the housing that is used to attach the grip, trigger, and battery. It was cut using a jig saw and fit to the grip multiple times before finishing to ensure that the appropriate amount of material was removed. This hole is used to route the wiring from the battery and trigger mechanism up to the motor. The trigger and battery are held in place using the original grip from our Drill Master cordless drill. The hole in the housing is covered by this grip to eliminate losses in air flow and to provide an aesthetically pleasing design. The grip was secured to the housing using four screws, two at each end. The grip was then sealed to the housing through the use of silicon around the contacting edge (figure 17). Inside the housing is the motor from our Drill Master cordless drill. This motor is centered inside of the housing by two acrylic, ring shaped motor mounts. These mounts were precision cut using a computer aided laser cutter. The motor sits concentrically inside the ring shaped motor mounts, while the motor mounts sit concentrically inside the vacuum housing. The motor mounts are held rigidly together and perfectly in-line by a PVC spacer that surrounds the motor (figure 18). The mounts, with motor attached, were glued to the housing using standard PVC cement. Figure 18: Motor Mount Spacers 35

36 Attached to the front of the motor is a centrifugal impeller that we designed and produced ourselves. The impeller was designed in SolidWorks and manufactured using 3D printing techniques. The 3.50 diameter impeller was designed using 8 backwards angled blades for optimal volume flow. The impeller was designed so that it would fit directly onto the original sun gear on the motor. The sun gear mate on the impeller was made to be a tight fit so that our impeller could be press fit directly onto the motor without any additional adhesives or other hardware (figure 19). In front of the impeller is a filter designed to block large debris from contacting the impeller. The filter is a wire mesh sandwiched between two acrylic plates. The plates were cut with a laser cutter to have an outside diameter of 4 and an inside diameter of 3.5 so Figure 19: Impeller that they would fit securely inside of the housing, but would still allow a large volume of air to flow through them. The filter assembly was secured in the housing by using an acrylic sealant as a backstop and adhesive (figure 20). The front was then glued to the housing with PVC cement. Figure 20: Attached Wire-mesh Filter At the back of the housing is an end cap. The end cap seals the back of the vacuum so that nothing may contact or interfere with the motor or motor wiring. The end cap was cut from clear acrylic. Holes were drilled in the end cap to allow hot exhaust gases from the motor to escape. The end cap was attached to the back of the vacuum using PVC cement (figure 21). At the front of our prototype is the nozzle. Like the impeller, the nozzle was designed in SolidWorks and 3D printed as one solid piece. The nozzle was designed to decrease from a 4 diameter to a 3/4 diameter to create a greater airflow velocity at the entrance of the nozzle. The nozzle is also downward sloping to allow for easier use and a more comfortable holding position for the user. The complete assembly can be seen in figure 22. Figure 21: End cap 36

37 Figure 22: Final Prototype Alterations Before this final beta prototype was produced, we constructed two functioning alpha prototypes. Since the production of the two alpha prototypes, we have changed some of the key features of our vacuum cleaner. Our first alpha prototype was strictly functional; it was not aesthetically pleasing and it was difficult to handle. This was mainly because duct tape was used to hold parts together, there was no handle for easy grip, and there was no backing to the housing. Also, with our first alpha prototype some of the parts were only used as temporary solutions. For example, the nozzle on our first alpha prototype was simply the top of a 2 liter soda bottle, and the impeller that was used only had a circular hole through the back, which made it hard for the impeller to stay on at high speeds. After testing and analyzing our first prototype, we began to make changes to produce a more effective second alpha prototype. On our second alpha prototype we used a 3D nozzle that was manufactured using the 3D printers in Reber building. We also printed a new impeller, and included a hole in the shape of the motor s sun gear, so the impeller could have a more perfect fit. Another important change from our first prototype, is that we added a spacer made of PVC that went in between the two circular motor mounts so they would stay perfectly concentric and parallel. We had also added a clear acrylic end cap to the housing that had exhaust holes so the motor would not overheat. Another added feature was that we had included a wire mesh filter that was duct tape to the inside of the housing. Finally, the last noticeable changes we made since our first prototype was adding a canister that was made out of water bottle and temporarily adding a handle to the housing by using duct tape. Since our second alpha prototype we have made a few more changes. Firstly, we used a new housing that is longer and has more consistent exhaust holes cut into it. Also, we have decided to get rid of the canister entirely, and instead the housing itself will be used as the area to hold the rice. The canister is emptied by detaching the nozzle. This was due to the fact that during testing, little rice actually fell into the canister. However we still are using the same filter from before except now it is being held in place using silicone gel and epoxy adhesive. Perhaps the last and most noticeable change we had made since our last prototype was drilling a hole in the housing to feed the wires through so they could be placed within the drill housing handle. From here we screwed the drill housing handle directly onto the housing and then sealed all the gaps with silicone gel. 37

38 14.3. Positives and Negatives of Final Prototype As we examined our final prototype there were many things we found to work well. Firstly, our prototype is able to generate a lot of suction. Also, the acrylic motor mounts worked very well, as our motor is nearly perfectly concentric, along with our impeller. Also, the weight is balanced relatively evenly throughout the vacuum which makes it comfortable to hold. Finally, another pro is that the nozzle is very easy to remove which allows for easy cleaning and emptying of the canister. On the other hand, there are a few downsides to our prototype as well. Firstly, our prototype was difficult to assemble. Therefore if something were to break it would take a long time to repair and reassemble the prototype. Another con is that some of the rice seems to fall back out of the inlet when the vacuum is turned off. Although this is a downside, the simple solution to this problem could be to add a flap on the inside of the inlet that prevents any rice from falling back out once the vacuum is turned off. 38

39 15. Performance This section explains the general performance of the final prototype. This is discussed in terms of usability and suction power. Tests showed that the prototype was simple to use and generated enough suction such that it would be competitive in the market Usability We found that our prototype was very comfortable to hold. The user should use both hands to operate the vacuum. One must be placed in the back to squeeze the trigger while the other should be placed near the nozzle. The handle which contains the trigger is very comfortable because we reused the drill s original handle. This handle has great features such as indents for people s fingers and a rubber section to help increase the user s grip. However, we found that it was uncomfortable for the user to hold the vacuum with only this handle. This is due to the fact that the entire vacuum s center of mass is not directly over the handle, especially when it is full of rice. To add more support, we recommend users to place their other hand directly behind the nozzle Suction Power Initially we wanted to ensure that our prototype generated suction. We started by running the vacuum at about half its full speed. When we blocked the inlet with our fingers, we found that there was a noticeable amount of suction generated. This suction was very similar to the amount of suction generated in the previous two prototypes. We then brought the vacuum slowly to full speed. Unlike our first prototype, the impeller did not fall off its shaft. We then brought the impeller to full speed as quickly as possible. This test was a success because the impeller did not break and an increase in suction was noticeable. Our next round of testing was to test the filter at low speeds. Like previous prototypes, we were able to suck up rice even when the impeller was spinning at low speeds. The filter successfully stopped the rice from contacting the impeller or exiting through the exhaust. Overall, our tests showed that the filter was able to filter rice from the air stream. Secondly, we tested our vacuum s emptying procedure. Overall, we found that it is very important to have the housing vertical with the nozzle facing up before taking off the nozzle. If the vacuum is at a slight angle, the rice would fall out of the housing extremely fast. Secondly, we found that some of the rice would get stuck between the nozzle and the housing. Therefore, when the nozzle was taken off, rice would fall out not matter how the vacuum is oriented. This is not a large problem since users can just open the vacuum over top of the trashcan. Since a mass produced nozzle would snap into place, this should not be an issue in the final product. Finally, we tested the vacuum at full speed and tried to see how quickly we could suck up a plate of rice. At full speeds, we were able to consistently suck up a plate of rice in about ten seconds. None of the rice exited through the exhaust and we were able to empty the vacuum in a controlled manner. The vacuum did not lose a noticeable amount of suction during the course of this test. 39

40 15.3. Conclusion The R.A.M. Squad s Handled Vacuum cleaner performed very well, both in terms of usability and suction. We found that not only was the device comfortable to hold, but it was also able to suck up a plate full of rice in a very competitive design. These two factors contribute to the success of this prototype. 40

41 16. Poster 41