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Vac Attack Final Report
Team #3: Adrian Baran, Matthew Murphy, Scott Novak, Doug Wissler
12/15/2014
Executive Summary
The Vac Attack portable vacuum is a response to the ACME tool company’s need for a portable vacuum
for their line of portable tools. The team was given the constraint of needing to reuse the motor and
battery of one of their existing cordless drills. Customer needs were addressed early in the design
process with the team including: effective removal of debris, ergonomic, easy to empty, and a durable
design. Quality Function Deployment was used to transfer these customer needs into technical
specifications necessary for the brainstorming phase, and the importance of various specifications was
assessed using the Analytical Hierarchy Process. The team eventually chose the fourth concept proposed
as the one which will continue on as the final product. Only one major change has occurred since then
with the impeller design going from a conical design to a centrifugal one for the final product.
The component and material selection of the product has been set with the housing, impeller, coupling
and nozzle/canister being made from ABS plastic using plastic injection molds. Items such as the motor
and battery will be carried over from the existing product line with the wiring and fasteners being
purchased from vendors. The ergonomics of the product was always considered throughout the design
processes with a comfortable handle designed along with an easily accessible on/off switch to promote
ease of use. Section 5.9 shows the beta prototype used to conduct the tests, and how it is constructed.
The testing procedure shown Section 6 can be replicated and describes the process which the team used
to optimize the Vac Attack vacuum for optimal performance for the competition against the other
design teams. Based off the specifications set by the team the product can be produced at $8.12 a unit,
and retail for $30. In a four year period the product will produce a positive NPV of $4,127,052.83 for the
firm showing that the product is a sound and profitable investment.
Table of Contents
Introduction………………………………………..............................................................................1
Customer Needs and Specifications……………………………………………………………………..…..….1-2
2.1 Identification of Customer Needs…………………………………………………………………………………………………………....1
2.2 Design Specifications…………………………………………………………………………………………………………..…………………..2
Concept Development……………………………………………………………………………….………….…….2-4
3.1 External Search…………………………………………………………………………………………………………….…………………………2
3.2 Problem Decomposition……………………………………………………………………………………………….………………………2-3
3.3 Concept Generation……………………………………………………………………………………………………….…………………….3-4
3.4 Concept Selection…………………………………………………………………………………………………………….……………………..5
System Level Design…………………………………………………………………………………….…………………6
4.1 Overall Description………………………………………………………………………………………………………………………… …......6
4.2 Preliminary Theoretical Analysis ………………………………………………………………………………………………………….…6
Detailed Design………………………………………………………………………………………………………….7-12
5.1 Modifications to Proposal Sections……………………………………………………………………………………… ….…………...7-8
5.2 Final Theoretical Analysis……………………………………………………………………………………….………………..……………8-9
5.3 Component and Material Selection Process (for Mass Production)…………………………………………………………..9
5.4 Fabrication Process for Mass Production……………………………………………………………………………………….…………9
5.5 Industrial Design …………………………………………………………………………………………………………………….…..………..10
5.6 Detailed Drawings…………………………………………………………………………………………………………….………..……… ..10
5.7 Economic Analysis…………………………………………………………………………………………………………….……………..10-11
5.8 Safety………………………………………………………………………………………………………………………………… …..…………….11
5.9 Construction of Beta Prototype………………………………………………………………………………………… ……………..11-12
Testing………………………………………………………………………………………………………….………..12-14
6.1 Test Plan………………………………………………………………………………………………………………………………….………12-13
6.2 Test Results and Discussion of Results………………………………………………………………….…………………………13-14
Conclusion…………………………………………………………………………………………………….……….14-15
References………………………………………………………………………………………………………….………16
Appendices…………………………………………………………………………………………….…….………..17-33
1
1 Introduction
1.1 Problem Statement
Team Vac Attack has been presented with the opportunity to develop a cordless vacuum cleaner based
off the existing architecture of the ACME Tool Company’s 18V cordless drill. The market for this product
is current users of the ACME line of products, and other consumers in need of a light, portable, and
affordable cordless vacuums. The team has been provided the following constrains for the project: a
completed design by November 15, 2015, developing the product around the existing electronic system
(batteries and motor), no components from competitor’s products may be used.
1.2 Background Information
Certain technical specifications are already available to the team due to the constraints in the project,
including: battery specifications and charge time [1]. The motor type, from performing a dissection of
the motor [Appendix A] and its specifications [2], and customer needs will be discussed later in the
proposal.
A substantial amount of information on centrifugal fans was used when determining the final fan design.
In order to achieve maximum efficiency, the team went with an airfoil blade design. An airfoil fan has
the highest efficiency of all centrifugal fans [10]. 9 to 16 blades of airfoil contour curve away from the
direction of rotation [10].
1.3 Project Planning
The project has gone through a methodical design process as shown in the Gantt chart [Appendix D] . In
the finalization of the design, members of the group were assigned specific tasks to complete while
other members were given other tasks. Each member was selected for their specific task based upon
their expertise in the task at hand whether it be theoretical analysis, creating the CAD files and
machining to name a few. Meetings were recorded with deadlines set for the completion of tasks, which
allowed the team to learn how projects are handled in the industry.
2 Customer Needs and Specifications
2.1 Identification of Customer Needs Early in the design process the team discussed possible customer needs and developed a list including: effectively remove debris, ergonomic, quiet, ease of emptying, cost effective, durability, battery life and ease of use. Also, by researching online customer reviews at “cnet.com”, the team found that customers where concerned with suction performance across a variety of material, portability and tendency to clog while operating. The customer needs the team established are primarily focused on the specific design objective of creating a portable vacuum to pick up rice. The reviews found online are for real manufactured vacuums, but some of the criteria still applies to our design project. After all research was
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completed, the team established that suction performance, ease of use , and emptying were the most important customer needs based off of the AHP’s [Appendix B]. 2.2 Design Specifications From the customer needs a proper list of design specifications was established. The design specifications include: force to move rice, handle design, decibel rating, canister size, cost, battery life, single speed and cycles per life. The customer needs were then related to these design specification by developing a Quality Function Deployment (QFD) [Appendix B, Table 7], illustrating the corresponding specification to each customer need. The design was broken down into three subsystems: suction, containment unit and body design. Within each subsystem there are particular specifications. These specifications were then weighted by importance. The most important features were found to be suction, ease of use, capacity of containment unit and reliability. From these weights all the specifications were arranged by using an Analytic hierarchy process. The tables illustrating the comparison of features within subsystems can be found in the Appendix B.
3 Concept Development
3.1 External Search
In order to start the design process, an external search was performed. Patents and current products
were researched to obtain information on the function and design of working vacuums. One of the
patents that was researched is a rigid transparent dust collection apparatus (US7419521 B2). This
apparatus was unique because it allows for quick and easy detachment, which would be preferred in the
final design. A Dewalt DC515 wet/dry vacuum was researched and documented because it used
common parts within the Dewalt family of tools using a 18V battery used throughout the product line
similar to our intended product. Other features include a large on/off switch instead of a trigger for
more comfortable use, and a large ½ gallon container for longer use between emptying the container.
All of these features were taken into consideration for the initial design concepts.
3.2 Problem Decomposition
The overall vacuum design was broken into three subcategories; body design, suction, and the
containment unit. These were then broken down into further categories as shown below in the Problem
Flow Chart.
3
Problem Flow Chart
The flow chart allowed the team to develop designs to fulfill each problem. For instance, the problem of
the containment unit is solved with either a detachable, internal, external, or a mix of more than one.
Each of the different subcategories were included in at least one of the concept designs that will be
shown in section 3.3 Concept Generation.
3.3 Concept Generation:
The team developed multiple concepts via multiple brainstorming sessions for the problem, which will
be tested to determine the best solution. Below are the concepts with hand drawn schematics of
varying degrees of complexity, and their descriptions:
Concept A
With the following concept it is intended to be
used as an alpha prototype mainly to test the
fan/impeller design solution that the team wishes
to implement on the product. A majority of the
original drill’s housing would remain intact with it
only being shortened due to the loss of the
transmission and chuck used on the original
product. The impeller would be directly mounted
to the DC RS550-18V motor to create the suction
necessary for the vacuum. In this particular figure
a gravity fed debris container (bottle) is shown
where the debris would accumulate as it is moved
through the nozzle.
Concept A
4
Concept B
Both of the following two concepts are fairly
similar in how they are shaped. The main intention
with these two concepts is to retain the lower
handle design used on the original drill to
minimize the overall housing redesign. The
majority of the redesign would be done on the end
where the motor and impeller is along with the
debris containment unit(s). Concept B retains the
same gravity fed container (canister) that was
shown in Concept A above, along the inclusion of
an on/off switch to simplify the use of the vacuum.
Concept C
With Concept C once again the design has
many similarities to Concept B already
described. The difference is the
placement of the actual debris container
(canister). In this concept the debris
would be contained in the same area as
the impeller. The impeller would be
shielded from the debris by a shielding
material that would allow for the fluid
(air) to flow, while not allowing the debris
to pass, and possibly damaging the
impeller. A possible solution for this
shielding would be a cone style air filter or
even mesh.
Concept D
Concept D takes on a completely
new housing with the only
components that are retained
from the original drill being the
battery, the battery connectors,
and the RS550-18V motor. The
housing retains a very
conventional design seen in
many handheld/portable
vacuum units. The on/off switch
Concept C
Concept D
Concept B
Concept C
5
shown in Concept B and C is retained to aid ease of use. A new handle will be designed to be as
ergonomic as possible promoting ease of use and comfort. The debris container (canister) is once again
similar to the one shown in Concept C above, and the impeller would be shielded by a material that
would allow fluid flow, but not allow for debris to pass. The nozzle pictured is not a final nozzle design,
but only a placeholder to show the location, with a more concrete design after alpha testing.
3.4 Concept Selection:
Decision matrices were used by the team to determine which concepts would be used in the final
design. An AHP table was created for each of the three subsystems; motor/suction, containment unit,
and body design. For each subsystem, multiple categories were created and compared to each other to
determine which aspects of each subsystem were most important. In order to explain how each table
works, AHP 1 [Appendix B, Table 1] will be used as an example. First, each category was given an
importance value, which the team decided together. In the first row, suction is compared to noise,
vibration, durability, and reliability. The numbers are determined by dividing the importance of the row
category by the importance of the column category. The first number, 4.00, was is the importance of
suction, 8, divided by the importance of noise, 4. Once a row was filled, the total was determined by
adding each number in the row together. To find the weight of each category, the total of each row was
divided by the total of the total column. For suction, 10.27 was divided by 24.24 for a weight of .42. Each
AHP was determined using the same aforementioned steps.
AHP 1 [Appendix B, Table 1] determined weighted values for the subcategories of motor/suction.
Suction ended with the highest weighted value, with reliabili ty and durability coming in a close second.
Vibration and noise were weighted as the least important. Next, AHP 2 [Appendix B, Table 2]
determined the weighted values of the subcategories for the containment unit. It was determined that
ease of use was the most important, followed by capacity, durability, and ergonomics. Finally, AHP 3
[Appendix B, Table 3] determined the weighted values of the subcategories for body design. It was
determined that ease of use and durability were the most important aspects of the body design.
Compactness and aesthetics were weighted as moderately important and mass was determined to be
almost a non-factor.
The determined weights were used to create a concept scoring matrix for three different design
categories. Using these matrices, a concept design was chosen for the impeller, containment unit, and
body. By using information from the external search, ratings were given based on data and observations
of patents and similar products. The durability of the 2D impeller was ranked lower because of its
thinner build, which wears quicker than the 3D impeller. It was determined from Concept Scoring Matrix
1 [Appendix B, Table 4] that the 3D impeller design will be taken further and the 2D impeller will not.
Concept Scoring Matrix 2 [Appendix B, Table 5] has the internal unit barely beating out the external unit.
The largest disparity was with ergonomics. An external canister is bulkier and in the way, while an
internal canister is hardly noticeable. With such similar scores, either design could be considered in the
future. A final decision will be made after testing of the alpha prototype.
6
A custom Housing was determined to be the superior design the body based off of Concept Scoring
Matrix 3 [Appendix B, Table 6]. The custom design, shown in Concept D of Section 3.2, is more compact
than Concepts A, B, and C. The team also determined that the custom body is more aesthetically
pleasing than the designs using the original drill housing.
4 System Level Design:
4.1 Overall Description
The chosen design incorporates six main components, as shown in Fig. 1. The vacuum is built around
the electric motor which acts as the central element. A fan, filter, and nozzle all have a horizontal
concentric alignment with the motor to allow for simplicity. This is possible because there is no gearing
off of the motor and the fan is connected directly to the shaft. All of these parts are encased in or
attached to a square like body that separates down the center for easy disassembly. The handle is part
of the body and has a button located by the thumbs position when holding the vacuum for ease of
use. The drills battery attaches to the back of the body staying away from the moving components in
the front. The nozzle also doubles as the containment unit for the rice using gravity to keep it settled at
the bottom.
4.2 Preliminary Theoretical Analysis
This handheld vacuum cleaners most important component when it comes to performance is the fan. In
order to determine what properties this fan needs, an existing vacuum must be compared. Two
important specifications in fan design are volumetric flow rate and change in pressure. To estimate a
Figure 1
7
flow rate that our electric motor is capable of producing, we compared it to an existing vacuum cleaner
whose specifications are shown in [Appendix C, Fig.4]. Using a ratio between motor input powers,
estimation for flow rate can be obtained. These calculations are shown in [Appendix C, Fig.2]. A flow
rate of around 4 ft^3/min is then used to determine the pressure change needed in order to create said
flow rate. This is shown in [Appendix C, Fig.3]. All data used for our motor is listed in [Appendix C,
Figure 5]. Equations are found from engineeringtoolbox.com, Fans – Efficiency and Power Consumption.
5 Detailed Design:
Figure 2: Exploded view of vacuum
Figure 2 shows an exploded view of our handheld vacuum cleaner. This design incorporates a simple set
up for ease of assembly and minimal part count. An electric motor, coupling piece, centrifugal fan, and
nozzle/containment unit all sit concentrically within a two piece body. This body acts as the housing and
supports for all components listed. All parts are sandwiched between the two pieces and require no
other components to support them.
5.1 Modifications to Proposal Sections
A prototype based on Concept A shown in the Section 3.3 was constructed and basic testing was
performed. From testing a few design flaws and problems were found. The main issue was the ability to
securely connect the 3D printed impeller to the metal gear at the end of the motor shaft. A couple of
methods were attempted with the best being hot glue to fit the pieces together, but at high rpm the
impeller rotation was very unstable. The new design will now include an aluminum adapter piece that
will fit over the gear and be secured using two set screws. The other end of the adapter will connect to a
high quality 3D printed fan by means of an axial screw with a washer providing compression on the fan.
This design will restrict movement of the fan in all directions, while still allowing free rotation. Another
8
change to the originally proposed design is the shape and type of fan being used. The new design is a
flat centrifugal fan with air foil blade profiles. An updated Gantt chart [Appendix D] shows the upcoming
project schedule that was updated to include beta prototype, submission of detailed design report,
design refinement and final testing.
5.2 Final Theoretical Analysis
In order to calculate the inlet pressure of the cordless vacuum, Bernoulli’s Principle and the
Conservation of Energy equations were used. A simplified equation is found below, considering
compressible flow due to air being the analyzed fluid.
outlet
PoutletVoutlet
inlet
PinletVinlet
)
1(
2)
1(
2
22
The equation can be simplified even further to the one below. At the inlet the velocity is considered zero
which creates high pressure. The inlet velocity terms are canceled out.
outlet
PoutletVoutlet
inlet
Pinlet
)
1(
2)
1(
2
The specific heat ratio of air:
401.1
The outlet will have a high velocity created by the impeller which creates low pressure. The high
pressure from the inlet will rush towards the area of low pressure to even it out, creating suction. The
outlet velocity created by the impeller with a radius of .0889 m and spinning at 6400 rpm is solved for
below. The rpm value is found from the table in [Appendix C, Figure 5].
s
mm
radrpmRVoutlet 58.59)0889)(.
sec60
min1)(
sec2)(6400(
Rearranging the simplified Bernoulli’s equation, the inlet pressure is solved for below.
2
)229.1()58.59(
)401.1
041.0(
3
2
m
kg
s
m
Pinlet
psiPaPinlet 0093.84.63
During the competition, 1 cup of rice will have to be removed from a plate. The weight of 1 cup of rice is
defined as Wr below. The area of plate is defined by Aplate, and was found by using a typical paper plate
radius of 4.5 inches.
9
lbsWr 46.
22 62.63)5.4( ininAplate
Finally, the force required to pick up one cup of rice spread evenly over the area of a plate is solved for
below by dividing the weight of one cup of rice by the area of the plate.
psiin
lbsFp 0072.0
)62.63(
)46.0(2
5.3 Component and Material Selection Process (for Mass Production)
The proposed product will use a combination of available off the shelf components as well as custom
components. Our custom components include: two housing halves, impeller, canister/nozzle, and
coupling. All of the custom components will be made with plastic injection molding, with the material of
choice being ABS plastic. ABS was chosen because the material’s properties make it a very impact
resistant and tough, which is ideal for a vacuum cleaner. The plastic is also widely used throughout the
industry making it readily available to purchase as a raw material. The main concern with this material is
to have a well-ventilated work space due to the fumes that may be harmful to potential factory workers.
The material can be easily recycled allowing for the reuse of scrap material in manufacturing, and once
the product reaches the end of its life [6].
The remain components for the product come off the shelf either from vendors or are already in used in
other products in the Drill Master line. The reuse of the motor and battery /charging system come from
other Drill Master products, which will allow the firm to lower costs across the whole line due to the
ability to purchase these parts at a bulk discount. The remaining components such as the toggle
switch/soldered wiring and fasteners can be purchased from vendors as specified by the design
requirements.
5.4 Fabrication Process
The fabrication process for the product will require an initial investment for 5 new molds necessary to
create the custom components outlined in Section 5.3. The molds required will be made out of
aluminum and will require machining to produce the desired shapes for each mold. After the molds
have been produced the actual parts can be made with each molded part needing some post processing
to remove any flash left after the molding process. Once that is completed the molded parts may e nter
the assembly line. Another necessary process is the joining of all of the electrical components: motor,
wiring, switch, and battery connector into one assembly by soldering any necessary connections. Once
this electrical sub assembly is complete the impeller may be attached to the motor. Afterward, the
impeller along with the electrical assembly may be placed into the housing and secured with the other
housing half. Finally, the canister and nozzle maybe be snapped on, and the product can be sent to
packaging.
10
5.5 Industrial Design
The design features a comfortable handle with an easy to use switch located on the spine of the handle
exactly where a user’s thumb would naturally lie. This enables the user to easily switch the vacuum on
and off with little effort. The weight of the vacuum is also evenly distributed so that independent of how
the user holds the vacuum there will no difference of how easy it is to support vacuum. The vacuum also
features flat surfaces on the both the sides and rear faces. This allows the user to set the vacuum down
without really needing to worry about how the vacuum is oriented. The vacuum is made primarily of
light weight ABS plastic ensuring that the overall weight is manageable and easy to use by all users
regardless of strength or body composition. ABS is also resistant to high impact ensuring that product
maintains its integrity through all common operations. The product is also symmetrically designed so
that it can be operated by either right or left handed users. The overall body design is rather compact
and in generally a rectangular shape, so that it can be used in most common vacuuming situations.
5.6 Detail Drawings
Figure 3: Side view of vacuum with all internal components
The detailed drawing shown in Figure 3 above shows the relative position of all of the components for
the vacuum. Complete design drawings are in Appendix E, which can easily be replicated to reproduce
the Vac Attack vacuum.
5.7 Economic Analysis
The bill of materials [Appendix F, Table 1] breaks down the cost for one production unit of the Vac
Attack vacuum. The break down includes how many of each component is necessary for the vacuum,
the cost of the raw material/part, the labor costs incurred, and the total cost for that part. A unit
production cost for one unit of $8.12 was calculated with a 13.5% overhead cost to help cover
11
marketing, development, and support costs for the product (one unit). All part, and material costs were
assumed to at a bulk discount rate as a result the cost to produce 100,000 units annually is $812,000.
The NPV (net present value) of the proposed product over 16 quarters is $4,127,052.83 at a 10%
discount rate. All of values presented above are based off a proposed price of $30 per unit. The NPV was
created by the team based of the estimations of various expenses including: development, production,
and ramp up costs. The full spreadsheet for the calculations can be seen in [Appendix F, Table 2]. Based
off the positive NPV calculation the Vac Attack vacuum is sound investments for the firm.
5.8 Safety
Our design features a two part housing which encloses the motor and all wiring. The two halves of the
body assembly are mounted together using screws which will allow the design to experience some
collisions and wear, without breaking apart and risking injury. This design will allow the user to operate
the product without the risk of being electrocuted by the electrical components. If an internal failure
where to occur all the components would be contained within the housing, eliminating the risk of
shrapnel injuring the user. The design also features rounded edges to ensure that the user does not
injure themselves or other with potential sharp corners of the vacuum while operating. The designed
vacuum is in compliance with UL1017 [7] standard for Vacuum Cleaners, Blower Cleaners, and
Household Floor Finishing Machines under 250 V. The designed product also complies with the UL60745
[8] standard for Hand-Held Motor-Operated Electric Tools as long as the product is not used on any type
of explosive or bio-hazardous material. The designed vacuum also complies with the IEC60312 [9]
standard for House Hold Vacuums particularly dealing with dry materials. This design is only safe to
operate on dry, non-explosive and non-hazardous materials operating with a power supply of less than
250 V.
5.9 Construction of Beta Prototype
The construction of the Vac Attack beta prototype (Figure 4) deviated from the mass production mainly
due to the inability to fabricate a housing unit such as the production model. Production techniques
used to produce the beta prototype differed as well due to the fact that a majority of the components
are plastic injection molded parts for the production model. On the beta prototype the components
produced were constructed using: a milling,
lathe, laser cutter, band saw, belt sander,
drill press, hot glue gun, soldering iron, wire
cutters, knife, duct tape, and a 3D printer.
Addition construction photos can be viewed
in Appendix G.
Figure 4: Completed Beta Prototype
12
The housing on the beta was made out of a 4” diameter PVC pipe at 7” in length to allow for the
packaging of the rest of the components, 16 exhaust holes
were drilled to allow air to exit, and an opening for the
electrical switch. To fit the motor onto the PVC pipe housing
securely two .1” thick acrylic mounting brackets were cut out
that would slide over the motor, with the motor being hot
glued in place. After the motor was glued in place an
aluminum coupling was attached to the gear on the motor
by tightening two set screws on the coupling, which would
for a stable mount for the impeller. All of this is shown in
Figure 5 to the right. The wiring that was used on the hand
drill was lengthened, re-soldered and a toggle switch
replaced the trigger. Also the team reused the lower
portion of the drill where the battery was attached,
and glued that piece onto another .1” thick acrylic
plate at the rear of the vacuum.
The team then began final assembly of all of these components into the PVC pipe housing. The motor
mounts were adjusted with the impeller on the coupling to get the proper alignment with the exhaust
holes that were drilled earlier. The motor mounts were then hot glued into place to prevent the motor
from shifting, and damaging the impeller. The 3D printed impeller was then finally mounted to the
coupling and secured by a bolt and washer. A shield was placed in front of the impeller where it acted as
a mount for the canister which a soup container and an inlet for air to the impeller. At the shield inlet a
fine wire mesh was also added to prevent debris from damaging the impeller. The container had the
nozzle permanently attached on the opposite side with hot glue. Finally, a handle was also glued on to
aid with the handling of the beta prototype. The overall form of the beta resembles that of the
production model, and allows the team to simulate how the production model would operate.
6 Testing:
6.1 Test Plan
The first test to be conducted will determine the most efficient nozzle design. Two nozzles were 3d
printed with identical bases and different diameter circular openings. Nozzle one has an opening with a
0.375 inch diameter and nozzle two has an opening with a 1 inch diameter. Both nozzles fit identically
to the current beta prototype. A flat plate taped to a surface will have 1 cup of uncooked rice evenly
distributed over it. Nozzle one and two will be attached to the vacuum on a series of separate runs.
These runs will be timed from when the vacuum is turned on to when the entire plate of rice has been
removed from the plate. Up to 15 pieces of rice can remain on the plate and still be considered a
completed run in order to promote accurate results. Five runs will be performed with each nozzle and
their times will be averaged. The nozzle with the fastest average time will be used for the final
Figure 5: Aluminum coupling and acrylic motor mounts
13
competition. Items needed include paper plate, duct tape, 1 cup of uncooked rice, 2 nozzles with
varying diameters, stop watch, and vacuum prototype with interchangeable nozzle slot.
Test number two will focus on the flow rate of the vacuum. The exit ports for the flow of the vacuum
are placed radially on the housing being concentric with the fan blades inside. There will be a total of 16
evenly spaced 0.25 inch diameter holes in this pattern. To begin the test all but two of the holes, which
are spaced 180 degrees from one another, will be covered with scotch tape to prevent flow. The
vacuum will be placed vertically on each run for consistency and a flow meter will be placed flush on the
nozzle. The fan will be turned on and the air speed will be recorded after it has stabilized on the meter.
This process will repeat after the tape is removed from two more holes spaced 180 degrees from each
other. The last run will consist of all 16 holes being open. These 8 data points will be graphed and a line
of best fit will be attached. The amount of holes used in the final design will be determined by the peak
of this graph. Items needed include scotch tape, flow meter, paper, pencil, and vacuum prototype.
6.2 Test Results and Discussion of Results
After performing the first test involving nozzle design, nozzle 2 with the larger diameter performed 79%
better than the other nozzle based on the average of the recorded times. Nozzle 1 averaged 7.77
seconds a run and nozzle 2 averaged 13.89 seconds. The data for individual runs is available in Appendix
H, Table 3. Going into this test, our team was not sure if our fan was producing a big enough pressure
drop for the larger diameter to work efficiently. The results proved that our original 0.375 inch diameter
nozzle design was more conservative than it needed to be with respect to its opening area. Because of
these results our final prototype will be using the 1 inch diameter nozzle.
The second test was conducted in order to optimize the flow of our vacuum. It had to be performed
two separate times due to concerns with the charge of the battery. The second time performing the
test, with a fully charged battery, produced larger overall air speeds so we chose this curve to base our
findings off of. This graph is shown below as Figure 6. The two data tables and original graph are in
Appendix H. Our data shows that the air speed rose with each set of holes being opened up. Right
around the point where all 16 holes are opened, our line of best fit levels off. Because of this we chose
to use all 16 holes opened up for our final design. Due to the graph leveling we came to the conclusion
that adding more holes would do nothing the performance of the vacuum.
14
Figure 6: Flow speeds vs number of exhaust openings
7 Conclusion and Recommendations: The Vac Attack portable handheld vacuum is a multi-part assembly featuring lightweight plastic
materials making it both easy to use, cost efficient, and eco-friendly. The design features airfoil fan
technology in order to maximize flow rate from the provided battery and motor (of a handheld drill).
The fan is mounted to the motor through a durable plastic coupling utilizing set screws to properly
secure the fan. A toggle switch is wired to the motor and battery, and all connections are soldered to
ensure reliability while operating at different orientations. The wire, fan and motor assembly are
encased in lightweight plastic housing with an attached ergonomic handle for customer ease of use. The
battery simply slides into place on the rear of vacuum and is easily removable. A fine mesh screen is
used to separate the fan and the containment unit to prevent debris from striking and destroying the
fan. The nozzle is permanently attached to the containment unit, which is easy to remove from the
housing, empty and clean.
The key features of this design are the centrifugal fan and the mounting coupling. The centrifugal fan is
able to produce massive suction to handle any type of household cleaning. The mounting coupling is
also key to the design because it allows the vacuum to reliably operate at maximum rpm’s without
chance of the fan disconnecting from the motor. Since the majority of the vacuum is produced through
injection molding using ABS plastic the vacuum is able to retail at $30, which is relatively inexpensive for
such a high performance device. From a manufacturer perspective investing in and producing this
vacuum is a high profit venture. The vacuum only costs $8.12 to produce and would retail for $30, which
in a four year period would produce a positive NPV of $4,127,053.
0
5
10
15
20
25
30
35
40
0 2 4 6 8 10 12 14 16 18
Flow Speed (mph)
Number of Open Holes
Flow Speed Test 2
15
The design could be improved further through the development of detachable nozzles, to adapt to the
many different cleaning needs of the customer base. Minor improvements could also be made to the
handle to improve ergonomics as well as placing the power switch in a more convenient location for
ease of customer use. Another improvement could be to the containment to make it easier to ope n and
empty, maybe by implementing a latch to open a door to release debris. Finally, the overall aesthetics
could be improved to make the product more stylish and pleasing to the customer’s eyes.
Through this entire design process the team has learned a wealth of information about product design,
as well as gained experience working as a design team. The team also learned about various
manufacturing processes and the advantages/disadvantages that each one possesses. The team utilized
3D printing while producing prototypes of the product, which proved to be a very efficient and easy
process to produce multiple functional models to test. The team also learned how successfully manage a
project by designating each member to a specific role suiting their strengths to ensure maximum time
and work efficiency. However the biggest lesson that the team learned from this design process is that
the first idea is never the best. Many prototypes were produced and were either scrapped or damaged,
allowing the team to address flaws that were unforeseen prior to actual building the prototype(s).
16
References
1. Drill Master Owner’s Manual available on Angel
2. Motor specs: http://kingmotor.en.alibaba.com/product/396990176-
211911710/DC_Motor_RS_550_RS555.html
3. Vacuum comparison: http://cjcelectric.gmc.globalmarket.com/products/details/cjc-vb-54-
series-electric-carbon-brush-ac-motor-for-vacuum-cleaner-1047019.html
4. Motor vendor: http://kingmotor.en.alibaba.com/product/396990176-
211911710/DC_Motor_RS_550_RS555.html
5. Household Vacuum Market:
http://www.businesswire.com/news/home/20131206005329/en/Research-Markets-Global-
Household-Vacuum-Cleaners-Market#.VEG40vnF-Lk
6. http://plastic-molding.daviesmolding.com/thermoset-thermoplastic.html
7. http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=1017.html 8. http://ulstandardsinfonet.ul.com/scopes/scopes.asp?fn=60745-1.html 9. http://webstore.iec.ch/preview/info_iec60312-1%7Bed1.0%7Den.pdf
10. Understanding Centrifugal Fans by Tom Gustafson
17
Appendix A
Drill Dissection:
Figure 1: Dissected Drill
RS 550 -18v
Motor
Transmission to
be removed
Trigger to be
removed for
on/off switch
Battery contacts
18
Appendix B
Motor/Suction Suction Noise Vibration Durability Reliability Total Weight Importance
Suction 4.00 2.67 2.00 1.60 10.27 0.42 8
Noise 0.25 0.67 0.50 0.40 1.57 0.06 2
Vibration 0.38 1.50 0.75 0.60 2.85 0.12 3
Durability 0.50 2.00 1.33 0.80 4.13 0.17 4
Reliability 0.63 2.50 1.67 1.25 5.42 0.22 5
24.24 1.00
Table 1: AHP1
Table 2: AHP2
19
Table 3: AHP3
Table 4: Concept Scoring Matrix 1
Table 5: Concept Scoring Matrix 2
20
Table 6: Concept Scoring Matrix 3
Table 7: QFD
Needs /
Specs
Force to
Move
Rice
Handle
Design
dB Rating Canister
Size
Budget/C
ost
Battery
Life
One
Speed
Cycles
per Life
Effective
Rice
Removal
X
Ergonomi
cs
X X
Noise X
Ease of
Waste
Disposal
X
Cost vs.
Performan
ce
X X
Durable X
Run Time X X
Simple to
use
X X
21
Appendix C
Figure 2: Flow Rate Estimations
Figure 3: Net Pressure Change
22
Figure 4: Electrical Specification Chart Reference [3]
Figure 5: RS 550 Motor Specifications; Reference [4]
23
Appendix D
Gantt chart
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 Week 14 Week 15 Week 16
Team Contract
External Search
Concept Generation/Selection
Drill Test
Presentation 1
Proposal
Alpha Prototype
Testing/Design Refinement
Beta Prototype
Detailed Design Report
Write Final Report
Beta 2 Prototype
24
Appendix E
Figure 6: Housing Half
Figure 7: Impeller/Fan dimensions
25
Figure 8: Nozzle/Containment Unit drawing
Figure 9: Coupling part drawing
26
Appendix F
Table 1: Bill of Materials
Bill of Materials and Production CostParts Qty Material Cost Labor Total
ABS Molded Parts
Housing 2 $0.70 $0.40 $2.20
Impeller 1 $0.15 $0.10 $0.25
Canister 1 $0.20 $0.10 $0.30
Nozzle 1 $0.05 $0.10 $0.15
Coupling 1 $0.04 $0.05 $0.09
Motor 1 $0.80 $0.10 $0.90
Wiring/Switch 1 $0.60 $0.10 $0.70
Battery + Charger 1 $1.50 $0.10 $1.60
Fastners 8 $0.05 $0.05 $0.45
Packaging 1 $0.60 $0.10 $0.70
Unit Production Cost $7.34
Overhead 13.5% $0.99
Total Cost 1 Unit: $8.33
27
Table 2: Project NPV
Year1Year 2
Year 3Year 4
ValuesQ1
Q2Q3
Q4Q5
Q6Q7
Q8Q9
Q10Q11
Q12Q13
Q14Q15
Q16
Development-200000
-200000-200000
-200000
Ramp up-225000
Production cost-203000
-203000-203000
-203000-203000
-203000-203000
-203000-203000
-203000-203000
-203000
Production volume25000
2500025000
2500025000
2500025000
2500025000
2500025000
25000
Unit Production cost-8.12
-8.12-8.12
-8.12-8.12
-8.12-8.12
-8.12-8.12
-8.12-8.12
-8.12
Sales Revenue750000
750000750000
750000750000
750000750000
750000750000
750000750000
750000
Sales Volume25000
2500025000
2500025000
2500025000
2500025000
2500025000
25000
Unit Price30
3030
3030
3030
3030
3030
30
Cash Flow-200000
-200000-200000
-425000547000
547000547000
547000547000
547000547000
547000547000
547000547000
547000
PV Year 1, r = 10%-200000
-195122-190476
-395349497273
486222475652
465532455833
446531437600
429020420769
412830405185
397818
Project NPV4127052.83
28
Appendix G
Figure 10: PVC pipe housing with 0.25” exhaust holes, hole for switch, and 3D printed handle.
Figure 11: Exhaust hole locations
29
Figure 12: Impeller on coupling relative to motor.
Figure 13: Impeller secured on coupling with bolt and washer.
30
Figure 14: Wiring from switch to battery mount. All connections are soldered.
Figure 15: Wiring inside the PVC housing
31
Figure 16: 3D printed nozzle and PVC pipe extension attached to soup container that acts as the debris container.
32
Appendix H
Table 3: Nozzle Run Test Data
Table 4: Air flow Test Data
(seconds) Nozzle 1 (0.375 in.) Nozzle 2 (1 in.)
Run 1 9.62 13.29
Run 2 7.33 14.5
Run 3 8.01 12.76
Run 4 6.36 13.53
Run 5 7.56 15.36
Average 7.77 13.89
Holes Closed Flow Speed (mi/h) Test 1 Flow Speed (mi/h) Test 2
2 12.5 12.8
4 18.7 19.1
6 20.7 24.8
8 23.9 28.1
10 26.2 32.1
12 26.4 33.9
14 26.8 36.1
16 27.6 35.6
33
Figure 17: Test 1 Air Flow Plot
0
5
10
15
20
25
30
0 2 4 6 8 10 12 14 16 18
Air
Sp
eed
(m
ph
)
Number of Open Holes
Flow Speed (mi/h) Test 1
