Design and Fabrication of an
Optical Stage Redesign
Critical Design Report
Team 04025
Adam Pruyne, ME – Project Manager
Nate Smith, ME
Andrew Gallagher, EE
Dr. Risa Robinson – Mentor and Customer
Dr. Alan Nye – Project Coordinator
Department of Mechanical Engineering
Kate Gleason College of Engineering
Rochester Institute of Technology
76 Lomb Memorial Drive
Rochester, NY 14623-5604
Team 04025
Optical Stage Redesign
Preliminary Design Report
Executive Summary
This report summarizes the progress made by the Optical Stage Redesign Team. The
majority of this report was previously presented during the PDR phase of the project with
exception to chapters six through nine which highlight devleopment, assembly and
testing efforts since that time. The goal of this project is to design and manufacture a test
apparatus to facilitate the research of particle flow dynamics in the human lung. Due to
the complexity of the seven generation lung model, the apparatus must be designed to
overcome many challenges to the Particle Image Velocimetry analytical process.
Primarily, the apparatus must allow full, unobstructed, analytical access to all flow
passages. To do so, the apparatus must be designed with several degrees of freedom of
movement as well as minimal contact with the model.
A multi-faceted approach to new product development was used to redesign the
optical stage. Transitioning through the first six chapters, the team is successfully poised
for completion of the Preliminary Design Review. The first chapter of this report outlines
the steps taken to identify and clarify the needs as well as the background for the project.
The second chapter presents the methodology used for developing concepts to
accomplish the goal of the project. The third chapter examines the technical, financial
and schedule feasibility of each concept culminating in a final design recommendation. It
is in the fourth chapter, that specific design criteria are identified and a set of
performance goals are developed for the project. The fifth chapter outlines design
concerns and presents analysis and justification for the design methodology taken by the
team. The last several chapters outline the experiences involved with the manufacturing,
development and testing of the Claw assembly. In addition, a chapter is included that
provides design improvement recommendations to further improve the Claw design.
Lastly, a conclusions chapter is included and represents the general overall impressions
that remain after participating in this project.
Through this process the optical stage redesign has evolved through many different
concepts to a final configuration that is technically sound and robust. Using a
combination of screw-actuated slides and existing materials, all passageways of the lung
model are analyzable and all other performance requirements have been achieved.
The final configuration of the optical stage redesign, including all supporting
mathematical analysis, delivery schedule and budgetary considerations as well as
manufacturing drawings are included in the technical data package. The package has
both
assembly
drawings
as
well
as
part
drawings
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Table of Contents
Executive Summary ............................................................................................................ 2
Table of Contents ................................................................................................................ 3
1
Recognize and Quantify the Need ............................................................................... 4
2
Concept Development ............................................................................................... 10
3
Feasibility Assessment .............................................................................................. 15
4
Design Objectives and Performance Specifications ................................................. 17
5
Analysis of Problems and Synthesis of Design ......................................................... 21
6
Prototype Development ............................................................................................. 30
7
Test ............................................................................................................................ 34
8
Future Design Considerations ................................................................................... 36
9
Conclusion................................................................................................................. 37
10 Acknowledgments ..................................................................................................... 38
FIGURE 1 - THE GYROSCOPE CONCEPT...........................................................................................................12
FIGURE 2 - THE RING CONCEPT ......................................................................................................................13
FIGURE 3 - THE GLOBE CONCEPT ...................................................................................................................14
FIGURE 4 - THE CLAW CONCEPT ....................................................................................................................15
FIGURE 5 - TORQUE ANALYSIS – CANTILEVERED LOADING IMPLICATIONS ...................................................26
FIGURE 6 - TORQUE ANALYSIS - POSITIVE LOCKING MECHANISM .................................................................28
FIGURE 7 - CLAMPING BLOCK MODIFICATIONS .............................................................................................31
FIGURE 8 - KEYWAY MODIFICATION ..............................................................................................................32
FIGURE 9 - MODEL SUPPORT MODIFICATIONS ...............................................................................................34
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1 Recognize and Quantify the Need
Aerosol research is a growing field of study in today’s biotechnology industry.
Understanding particle dynamics within the human lung could lead to more effective
treatment of pulmonary diseases such as asthma, tuberculosis and COPD. Additionally,
understanding how particles behave with in the human lung could lead to new methods of
treatment for diseases such as diabetes or how to safe guard against airborne
contaminants such as cigarette smoke and biological weapons.
Currently, there are experiments taking place at the Rochester Institute of
Technology with the expectation of gaining insightful knowledge into these particle flow
dynamics of the human lung. Using a technique known as Particle Image Velocimetry
(PIV), velocity profiles are being mapped through an ideal three-generation lung model.
Knowing the velocity profiles for this ideal case is only the first step toward greater
understanding.
To gain in-depth knowledge of particle flow dynamics in the human lung, a sevengeneration cast replica of a thirty-four year old male subject, must be tested. The current
experimental test set-up is poorly equipped to handle a model of such complexity. As a
result, a more versatile test set-up must be constructed that will provide access to the
many additional bifurcations as well as meet several performance criteria as specified by
the customer.
The mission of this project is to create an experimental test set-up that will meet or
exceed the expectations of the customer. Consideration will be given to every detail.
Utilizing knowledge gained through study at the Rochester Institute of Technology the
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proposed design concepts will be thoroughly scrutinized and a concerted effort will be
utilized to achieve excellence in design and reliability.
To be able to effectively implement the mission, the characteristics of the project
must be described. The optical stage redesign employs multiple positioning mechanisms
including three translational slides and one rotational platform. Each of these positioning
mechanisms is capable of an infinite number of positions and therefore the operator is
unlimited in the positioning of the lung model. Additionally, the lung model is capable of
limited rotational motion about its axis. As a result of the positioning mechanisms and the
partial lung rotational motion, multiple degrees of freedom of movement are achieved.
A motorized camera focus has been incorporated for operator convenience. The
operator will no longer have to move from the PC workstation to the apparatus to adjust
the lens focus. The motorization of the camera focus will occur at the PC workstation.
All mechanical components of the optical stage redesign have been chosen to
provide sufficient design margin and mechanical stability. Angle brackets and
strengthening gussets have been incorporated to prevent deflection and twisting of
extension arms due to cantilevered loads. Materials for manufactured components have
been chosen for strength and to minimize bulkiness. Electrical components have been
chosen for their durability and performance.
A major objective of the project is to retain focus on, and to work within, specific
overall scope limitations of the project. One of the most important of these scope
limitations is regarding project documentation. Upon successful completion of this
project, the optical stage redesign team shall provide the customer with all necessary
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analysis, documentation and data acquired during the redesign effort. Additionally, the
scope limitations include working within a set budget and schedule. The project shall be
completed with in the specified budget of $2000 and be delivered in a timely manner
starting with the Preliminary Design Review in November of 2003 and the Critical
Design Review in May of 2004.
There are certain individuals or groups of individuals, called stakeholders, which
stand to benefit greatly from the successful outcome of this project. The primary
stakeholder has been identified as Dr. Risa Robinson, Assistant Professor of Rochester
Institute of Technology. The secondary stakeholders have been identified as Dr. Mike
Oldham of the University of California, the Mechanical Engineering Department of
Rochester Institute of Technology and the biotechnology and healthcare industry.
Beginning with the end result in mind, the key business goals of a project provide a
picture of the global effect that the successful completion of this project could provide in
the business sector. The key business goals, for the optical stage redesign effort, have
been established. With the success of this project there will be opportunities to contribute
to advancement of medical knowledge and as a result, many additional opportunities,
both financial and research oriented, could become available to either the team members
or the Institution.
To ensure that the project will meet financial objectives a preliminary analysis has
been conducted. As mentioned previously, the overall budget for the optical stage
redesign is $2000. Based on extensive research and assessment, there have been several
major cost concerns identified. Two optical stages, each at a cost of $440, must be
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purchased. At least one motor and other electrical supplies must be purchased in an effort
to supply the motorized camera focus function. These electrical supplies are not expected
to exceed a cost of $250. Other miscellaneous materials such as an assortment of
fasteners and angle brackets and gussets are estimated to cost approximately $100.
Manufactured components are not expected to exceed $200 as much of the machining
will be completed in-house. The remainder of the apparatus materials will be supported
with in-stock fixturing where applicable.
It is important to establish, from a business standpoint, what represents the primary
and secondary markets for the optical stage redesign. To do so provides additional insight
into the impact of the successful completion of the project. Although there is no primary
market for the apparatus itself, the resulting research will be very valuable to the
healthcare industry. Providing a better understanding of lung dynamics will facilitate
cheaper and more effective treatments for patients that suffer from a number of illnesses
including asthma and even diabetes.
Considered a secondary market, the research sector could advance significantly
with a better understanding of particle dynamics in the human lung. Future opportunities
for experimenting with more complex models will be possible with a versatile design. It
is expected that future graduate studies will proceed using this apparatus based on the
versatility of the final configuration of the optical stage redesign.
There are certain aspects that are considered an “Order-Qualifier” and those that are
considered an “Order-Winner”. Order-Qualifier aspects of the project are those that meet
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the customer’s basic requirements. The following have been identified as the project’s
Order-Qualifiers:
1. The test-bed must support a flexible, translucent model with minimal contact
points.
2. The test-bed must supply a minimum of three-axis rotation and translation.
Rotational freedom need not exceed 90 degrees in any axis. Translational freedom
must allow for three to four inches of travel in all three axes.
3. Resolution of rotational and translational adjustment must be fine enough to
secure and positively lock the model at angles of ± 0.5 degrees and translational
distances to within ± 0.005 inches.
4. The test-bed must be able to supply liquid flow to the model via one inlet and
multiple outlets. This supply must not inhibit rotational and/or translational
motion.
5. The test-bed must ensure that the light sheet generator (LSG) and the digital video
camera remain in a two-dimensional plane and at 90 degrees to one another at all
times.
6. The platform for both the camera and the LSG must be adjustable and maintain
the ability to be positively locked into position.
7. The vertical motion platform for the camera must be able to be adjusted while
monitoring flow at the PC workstation.
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Order-Winner aspects of the project are those that exceed the customer’s basic
requirements. As the project is a relatively simple one, it is difficult to identify many
Order-Winners. Along with this fact, the following project Order-Winners have been
identified:
1. The test apparatus will improve user “friendliness” by requiring minimal tools to
adjust position of the model/PIV equipment position.
2. The project is estimated to cost several hundreds of dollars less than the proposed
budget.
3. The durability of the test set-up is superior to the existing set-up.
4. The compact and simple design of the apparatus permits easy teardown and set-up
for movement to other research locations.
5. Movement of the Fiber Optic Cable will be minimized.
The ultimate goal of the optical stage redesign team is to provide a fully functional,
multi-axis experimental test set-up that is capable of meeting or exceeding all of the
customer’s requirements. The team has agreed to these requirements as stated in the prior
paragraphs of this document. The team shall endeavor to include, as a minimum:

A completed test apparatus that addresses the Order-Qualifiers objectives as
presented in previous paragraphs of this report.

A Technical Report chronicling the product development philosophies utilized in
the design of the apparatus.
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
Preliminary Design Report
This technical report shall also include financial and future schedule information.
This financial and schedule information will provide a clear justification for
component selection and cost.

A Technical Data Package that includes manufacturing and assembly drawings
as well as supporting analyses, delivery schedule information and a financial Bill
of Material.
2 Concept Development
During the concept development phase, a technique known as brainstorming was
used to fabricate a long list of design concepts. The philosophy for the long list was not to
arrive at the final solution but to build a roster of possible candidates regardless of
feasibility. Once the long list was created, an informal process of eliminating concepts
was employed to create a short list of more feasible candidates for the final design.
Concepts were down-selected if they obviously exceeded the scope of the project or were
not able to meet all of the customer requirements. The short list consisted of three
promising concepts.
The three final concepts were then modeled in Pro-Engineer CAD software. This
step was completed in an effort to give validity to the short list concepts. By modeling the
concepts in a three-dimensional CAD package, the advantages and limitations of each
concept are exposed. This process of three-dimensional modeling facilitated the
feasibility assessment that will be discussed in future chapters of this report.
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To ensure that all detailed components and purchased parts are accounted for,
preliminary Bills of Material (BOM) were created for each concept. Although it is
anticipated that the machining of components will be completed in-house, a machine
shop was contacted for estimated material and labor cost for parts that required intricate
machining beyond in-house capabilities. Vendors or their internet websites were
contacted for pricing sheets and specifications for any purchased hardware that was
necessary. The result of this effort was a reasonably accurate preliminary financial
assessment for each concept.
The following paragraphs provide a brief description of each short list concept that
resulted from the initial concept development.
The Gyroscope
This concept was founded on the premise that a gyroscope-type apparatus would
easily provide full access to all flow passageways. A gyroscope would allow three
degrees of rotational freedom. The translational degrees of freedom would be
accomplished by a series of positioning slides stacked on top of each other. After further
analyzing this concept, it was decided that a true gyroscope would not be realistic, as the
gyroscopic mechanism would not only obstruct PIV imagery but cause interference with
the flow tubing of the model. A modified version of the gyroscope, which addressed
these concerns, was conceived in its place. This modified version used a quasi-gyroscope
platform that supported the model. Shaped like a U, this support would easily be
positioned and locked in an infinite number of locations, within the confines of the U
shape. Being confined to the U-shape would prove to be this concepts major disadvantage
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as a consensus was reached that this U shape would not allow PIV access to all flow
passages.
Figure 1 - The Gyroscope Concept
The Ring
The Ring concept was the only concept to immobilize the lung model. This aspect
was considered the concept’s greatest attribute as the customer has expressed a desire to
minimize flow inconsistencies resulting from a moveable model. The benefit of the full
ring design is that the camera and light sheet generator are mounted at 90° to each other
on a common structure. Because of this, the requirement of keeping the camera field of
view perpendicular with the laser was easily satisfied. The ring can rotate completely
around the lung model. As with other concepts this concept incorporated three
translational slides to achieve the number of degrees of freedom necessary to fully
analyze the lung model. Among the limitations of this concept were its suspect stability
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and the inability of the ring to fully revolve around a vertical axis, based at the center of
the lung model. These aspects limited the Ring’s ability to permit full PIV access to the
lung model. Additionally, the budgetary implications of the one-piece circular member
were difficult to justify.
Figure 2 - The Ring Concept
The Globe
The most promising aspect of this concept was that that majority of components
could be purchased. Aside from potentially jeopardizing budget constraints, the ability to
purchase parts, rather than make them, would improve delivery schedule and provide
easier assembly. Unfortunately, the hemispherical platform has a limited degree of tilt.
As a result, this concept would not be able to provide full PIV access to all flow passages.
Additionally, this concept required the most contact between the model and the
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hemispherical platform that supports it. This aspect was of concern to the customer, as
the model would have to be moved to be able to access all flow passageways.
Figure 3 - The Globe Concept
The Claw
This concept represents the evolution of the Ring design. Relying on the
underlying premise of a stationary model, this concept transformed from the more
questionable Ring concept to a more stable configuration. The claw concept employs
robot-like extension arms that support the light sheet generator and camera such that they
are perpendicular to each other. These robot-type arms revolve about a horizontal axis
that is parallel to the axis of the model and therefore most of the model’s outside surface
is visibly accessible with the extension arm assembly alone. The remaining portion of the
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model’s surface can be analyzed by minimal rotation of the model about its horizontal
axis.
Figure 4 - The Claw Concept
3 Feasibility Assessment
The next phase of the project was to select one of the concepts from the short list of
candidates that was the most technically and financially feasible. To be considered
technically feasible, the final concept would need to meet all of the customer’s
performance and design requirements as well as be mechanically sound and able to be
manufactured. To be considered financially feasible, the concept would be required to fit
within the budgetary constraints of the project. Using a systematic approach to feasibility
assessment, a series of tools were utilized to narrow the selection objectively and without
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bias. The results of all feasibility assessment tools are included in the supplemental
Technical Data Package.
The first assessment tool to be used was a Radar Chart. A Radar Chart’s purpose is
not to provide an in-depth analysis of feasibility but to provide an easy method for a
visual preliminary assessment. The results of the Radar Chart comparison indicate that
the claw concept maintains a slight advantage over the other two concepts as a result of
its ability to meet budgetary constraints, its ability to meet the necessary degrees of
freedom necessary to provide full PIV access and its overall less complicated design.
These slight advantages, as expressed by the Radar Chart, do not provide enough
justification for selecting the claw concept over the others so other assessment tools were
utilized.
Because the Radar Chart assessment tool was inconclusive, a second assessment
tool, called the Pugh Method, was used. In this method, two of the three concepts were
compared to the third concept in an effort to determine which was the most feasible.
Unfortunately, the results of the Pugh Method were also not conclusive. Although a slight
advantage was given to the claw concept, each concept scored virtually the same. Again,
a final concept could not be confidently selected.
The final assessment tool to be used was the weighted method. The benefit to the
weighted method is that attribute categories are assigned a numerical weight that places a
greater emphasis on certain attributes over others. As a result, when each category is
rated on a scale of one to five, the weighting factor multiplies this rating. The weighted
method provides a more complex assessment tool that takes into consideration more
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detail about the concepts and their attributes. As a result, core confidence can be taken in
its assessment results. The results of the weighted method assessment proved that the
claw concept held and an advantage over the other two concepts.
Based on the results of the assessment tools, and a careful scrutiny of each concept,
it was determined that the Claw concept provided the most benefit. Its simple design will
facilitate manufacturing and procurement of parts as well as schedule and financial
concerns. The Claw concept represents an optimal balance between the improved “ease
of use” over the existing test set-up with new functional features that allow sevengeneration model testing. Additionally, all of the customer’s performance objectives can
be achieved with this design. It was for these reasons that the Claw concept was chosen
as the final concept.
4 Design Objectives and Performance Specifications
A good design is created around well-defined design objectives. These objectives
keep the focus of the design initiative on addressing the customer’s requirements. Several
design objectives were identified for this project. The first design objective is based on
the requirement for minimal contact points between the model and its support.
Minimizing the number of contact points promotes full access to all flow passageways in
the lung model. Without this “full-access” capability, the concept design would be
insufficient.
The second design objective is based on the requirement that all flow passageways of
the seven-generation lung model are accessible to the PIV imagery equipment. This
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objective is imperative as the inability to access all flow passageways, regardless of
direction or plane, is the primary function of this apparatus.
The third design objective involves translational and rotational positioning tolerance.
Positioning tolerance is important for this apparatus as small movements in the lung
model translate into highly amplified movements within the camera’s field of view. This
amplification is the result of the camera’s level of magnification. It is for this reason that
the translational and rotational positioning tolerance be as small as possible.
The fourth design objective is to ensure that the design of the model support does not
cause interference with the lung model’s inlet and outlet flow tubes. Obstruction of these
flow tubes, caused by interference with the support, can result in inaccurate flow
characteristics. These inaccuracies can lead to rendering the experiment invalid.
The fifth design objective is to ensure that the Light Sheet Generator and the camera
are located perpendicular to each other in a single two-dimensional plane. In the current
test set-up, these two pieces of equipment are not attached to a common support. As a
result, if one piece is moved it is possible that the two are no longer perpendicular to each
other. Non-perpendicularity, between these two components, can lead to skewed velocity
profile results and therefore must be minimized.
The sixth design objective closely parallels the requirement of the fourth design
objective. The light sheet generator and the camera must both be positively locked into
their respective positions. Being positively locked into position ensures that the correct
camera focal length and perpendicularity are maintained. Therefore, valid experimental
results are achievable.
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The seventh design objective is to ensure that the camera can be focused from the
operator’s PC workstation. The current test set-up requires the operator to move from the
camera focus to the PC monitor and back while attempting to bring the particles into
focus. Although achievable, this process is inefficient and problematic as it is difficult for
the operator to determine if the particles are in focus from several feet from the monitor.
Properly focused particles are essential to good PIV analysis results as the crosscorrelation technique depends highly on clear images to be accurate.
To ensure that the design objectives have been successfully addressed, performance
specifications must be created. These performance specifications, written in the form of a
“yes” or “no” question, provide a means to quantify that the design objectives were
achieved. To each of the design objectives listed above there are a corresponding
performance specification. These specifications are listed and described as follows:
1. Is the lung model simply supported to minimize points of contact between it and
its support?
2. Does the apparatus provide the necessary degrees of freedom of motion to allow
all passageways to be analyzed?
3. Is positioning resolution fine enough to achieve incremental translational and
rotational motion to the tolerance of ±0.5° and ±0.005 inches, respectively?
4. Is translational motion of 3” achievable by all translational slides, excluding the
camera focusing slide?
5. Does the test apparatus provide model support in such a manner as to minimize
interference with supply flow tubes as a result of model positioning?
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6. Does the Light Sheet Generator and Camera exhibit 90° ±2 ° perpendicularity
when an object of similar tolerance is placed between them?
7. Does each positioning mechanism provide a positive locking mechanism?
8. Is the platform for both the LSG and the camera adjustable?
9. Is camera focusing achievable while seated at the PC workstation?
10. Does the apparatus minimize Fiber Optic Cable Disturbance?
By addressing each of these performance objectives with the concept design, a
product that meets the customer’s requirements is eminent. In addition to these basic
performance requirements, certain engineering and manufacturing philosophies will be
utilized to ensure a quality design. These engineering and manufacturing philosophies are
listed below:

Design for Manufacturability – The apparatus has been designed such that all
components can be manufactured, in-house, at RIT.

Design for Re-Usability or Re-manufacturing – The apparatus has been designed in
such a way to facilitate assembly and disassembly processes. Upon disassembly, all
components will be reusable.

Design for Assembly – The apparatus has been designed such that the number of
assemblies and components has been minimized to reduce complexity.

Design for Low Cost – The apparatus has been designed such that the cost of
manufacture is minimized. Only the necessary components will be utilized to meet
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the minimum customer requirements. The materials were selected under the benefit of
a thorough cost benefit analysis process.

Design for Efficiency – The apparatus has been designed to make it as efficient for
the user as possible within the scope of the project.
It is also important to discuss any safety issues that may need to be addressed as a
result of this project. There are no known safety issues involved with this project.
Although the use of the LASER represents as significant risk to those operating the
station without proper eye-protection, there are no known risks in operating the apparatus
other than basic common sense. These common sense practices would include being
careful not to get fingers, hair or clothing in any of the moving mechanisms and to avoid
any edges of the apparatus that appear sharp.
5 Analysis of Problems and Synthesis of Design
This portion of this document outlines the methodology taken in the analysis of
problems and synthesis of design. In the methodology of Analysis of Problems and
Synthesis of Design, analysis is used to foster design maturity. Each of the design
objectives and performance specifications must be accounted for in the analysis and
synthesis. Additionally, any “by-product” design concerns must be addressed. “Byproduct” design concerns are those concerns that arise out of investigation of a
completely separate aspect of the design. By addressing all concerns, the most technically
sound and robust design solution is possible. Any applicable analyses are presented in the
supplemental Technical Data Package.
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The analysis and synthesis of the first design objective led to the simplistic design
of the model support. The requirement of minimal contact points between the model and
its support was easily achieved by careful design and component selection. The claw
concept incorporates a fork-type support where two support rods slide through holes on
the upright brackets. These support rods contact the model in only two places. As a result,
the design objective of minimal contact points is easily achieved.
The analysis and synthesis of the second design objective led to the use of
multiple translational and rotational positioning mechanisms in the design. The ability to
analyze all flow passageways offers a significant challenge. To achieve this requirement,
a multiple degrees of freedom approach was considered. It was determined that a
minimum of five degrees of freedom, three translational and two rotational, would be
necessary to fully analyze all flow passageways. This consensus was reached based on
sketching and conceptualizing of the model in Pro-Engineer software and examining the
lung model, in relation to the claw concept, in 3-D space. As a result of this examination,
each area for mechanization was carefully chosen. For instance, the base pedestal of the
claw mechanism houses the three translational degrees of freedom. The claw can move
both in and out, to the left and right as well as vertically. Additionally, the claw extension
arms rotate about a pivot axis that intersects the lung model’s center of gravity, providing
one of the two required rotational degrees of freedom. To accomplish the last rotational
degree of freedom, the lung model support rotates about a vertical axis. As a fail-safe
mechanism, and realizing the support of the lung model will prevent the claw mechanism
from performing a full 360° of rotation about the lung model axis, a provision was made
to the lung model/support interface. This provision allows the lung model to rotate about
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its axis to ensure that the entire outside surface of the lung model is accessible to the
camera and LSG. Since all of the positioning mechanisms have infinite resolution and are
easily adjustable and positively locked, all flow passages will be analyzable and easily
adjusted by the operator.
Pursuant to the third design objective and performance specification, the choice of
positioning mechanisms was considered. The main criterion for this requirement is that
the positioning mechanisms shall not exhibit index-type motion. Index-type motion is
motion where the operator cannot achieve the desired position as a result of being
between two index points. The Claw design incorporates screw drive linear motion slides.
These types of linear motion slides maintain an infinite amount of positioning resolution,
meaning that there they do not exhibit index-type motion. As a result, the requirement of
positioning resolution to within ± 0.005 inches is achievable. The Claw design also
incorporates simple post-and-hole rotational positioning mechanisms. In this type of
positioning mechanism, a shaft is placed into a tube. The dimensional tolerance of this fit
is classified as a “slip fit”, tight enough to prevent looseness but enough clearance to
allow rotational motion. As a result, this type of mechanism exhibits no index-type
motion and the rotational positioning tolerance of ± 0.5 is easily achieved.
The analysis and synthesis of the fourth and fifth design objectives address the same
issue of the limitation of model positioning as a result of limited range of motion and
tubing interference. During the Pro-Engineer three-dimensional analysis of this design
objective, it was determined that the positioning mechanisms would require a minimum
of three inches of linear translation to ensure the entire length of the model is accessible
to the PIV equipment. As a result, the positioning mechanism that was chosen is capable
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of at least three inches of travel in the X, Y and Z directions. To minimize flow tube
interference, the support mechanism was carefully designed. This requirement is very
similar to that of the first design objective. The model is contacted by the apparatus in
only two locations by support rods. These support rods extend away from the model far
enough that they do not interfere with any of the flow tubing. Additionally, the main bulk
of the design is placed away from the model so any rotation that the model must do will
not result in interference with the main body of the design.
The analysis and synthesis of the sixth design objective was extensive. The ability to
maintain a 90°±2° angle between the Light Sheet Generator and the camera resulted in a
somewhat complicated design issue. It was recognized that to accomplish this
requirement, the design would have to incorporate a common member approach. A
common member approach is one in which both the camera and the light sheet generator
are supported by a one common structure. As a result, the claw design incorporates this
feature. The extension arms, although not a true common structure, are rigidly supported
and fixed at the joint locations creating a solid one-structure member. To be able to
consider the common structure rigid, several analyses were conducted. As a result of the
fourth and fifth design objectives, it was necessary for the main portion of the design to
be moved away from the model support. This movement resulted in a fairly substantial
cantilevered loading scenario (see Figure 5) that could result in deflection. It was
recognized that any deflection in either the pivot shaft or the extension arms could result
in violation of the 90° ± 2° requirement. Although mechanical engineering intuition led
to the conclusion that the cantilevered mass would not cause any noticeable deflection in
the shaft or the extension arms, a deflection analysis was conducted on both the shaft and
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the worst-case extension arm loading scenarios. The results of these analyses showed that
both deflections were minimal and would not cause the design to violate the desired
perpendicularity requirement.
While addressing the cantilevered loading analyses, it became apparent that the
vertical linear positioning slide might experience awkward cantilevered loading (see
Figure 5). Typically, this type of positioning mechanism experiences loading that causes
rotation away from the mounting surface of the slide (see TY in Figure 5) or loading
toward the mounting surface of the slide (see TZ in Figure 5). In the claw design the
cantilevered load is parallel to the face of the mounting surface (see TX in Figure 5) and
therefore is cause for concern. The slide manufacturer was contacted with the proposed
loading scenario and a specific slide was suggested that would sufficiently tolerate this
loading scenario. As a result, the claw design will achieve and maintain the
perpendicularity requirement.
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TZ
Z
TX
X
Y
TY
Figure 5 - Torque Analysis – Cantilevered Loading Implications
Also, while addressing the cantilevered loading analyses, design consideration
was given to the bearings for the pivot shaft rotation mechanism. Although it seemed
intuitively obvious that any bearing selected for this mechanism would sufficiently
handle the loading scenario, a simple mathematical analysis was performed to ensure the
desired level of performance was achieved. This analysis presented a simple static-type
problem where the weight forces, in the vertical axis direction, were summed to
determine the radial loading forces that each bearing would experience. The results of
this analysis, in combination with the technical data supplied by the bearing
manufacturer, showed that the loading scenario would not adversely affect the bearings.
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The analysis and synthesis of the seventh design objective also required a
mathematical analysis for design validation. The ability to maintain positive position
locking mechanisms was of particular concern. It was recognized that all of the
positioning mechanisms maintained sufficient locking mechanisms to satisfy this design
objective but particular attention was given to the locking mechanism that prevented
rotational motion about the claw’s horizontal pivoting mechanism. Again as a result of
the cantilevered loading analysis, it was recognized that the suspended mass of both the
light sheet generator and the camera would result in a large torque load, Ty, on the antirotation locking mechanism (see Figure 6). The analysis and synthesis methodology was
to choose a design for this anti-rotation mechanism based on similar devices in the
industry and then perform an analysis on the design to ensure that it could withstand the
loading scenarios. The results of this analysis showed that the locking mechanism chosen
would adequately prevent rotation and thus satisfy the positive position-locking
requirement. The positive locking mechanism for the linear positioning slides is
considered to be the torque necessary to turn the positioning screw. The rotational
platform that supports the model incorporates a thumb-screw that creates a positive lock
on rotational movement.
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Z
X
F Clamp
Y
TY
Figure 6 - Torque Analysis - Positive Locking Mechanism
The analysis and synthesis of the eighth design objective provided a design that
allowed both the light sheet generator and the camera to be adjusted if required. The
extension arm supports for both the light sheet generator and the camera are constructed
from aluminum x-channel. This x-channel is often used in laboratory experimental
apparatuses as a result of its modular nature. The modular nature allows simple changes
in position with the use of one tool. As a result, both the camera and the light sheet
generator can be positioned as needed.
The analysis and synthesis of the ninth design objective provided a design that
was capable of allowing the camera to be focused while maintaining a seated position at
the PC workstation. Recognizing that this need could be satisfied with the use of a
motorized camera focus, an electro-mechanical solution was devised. An electrical circuit
was created which incorporated a small stepper motor that interfaced with the camera-
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positioning slide. Although several different motor options were considered, all except
the stepper motor failed to strike a balance between power requirements, torque load
capability, resolution of rotation and cost. To ensure that the stepper motor would provide
enough torque to lift the camera assembly, a simple mathematical lifting torque analysis
was performed. The results of this analysis showed that the torque needed to lift the
camera assembly was relatively small in comparison to the available torque of the motor.
Therefore, the stepper motor will accomplish the design objective.
To provide positioning control over the stepper motor a control circuit needed to
be designed. This control circuit was modeled based on a Motorola stepper motor driver
circuit. This circuit presents a low cost, simplistic and easily fabricated design. In
conjunction with the driver circuit, a clock circuit must be fabricated. This fabrication is
accomplished by using a National Semiconductor timer chip. A simple switch will be
added to allow the user control of the motor. Additionally, to address the heat that will be
generated by the large amount of current flow in the circuit, heat sink devices will be
used. These heat sinks will ensure that the circuit does not overheat and break down. The
electrical power for the system will be provided by a simple AC power source that is
supplied by the customer. As a result, the operator will be able to “dial-in” the camera
focus from the PC workstation. Diagrams of the driver circuit are included in the
supplemental Technical Data Package.
Mechanically, incorporating the motor presented a particular design challenge as
an interface mechanism, between the camera’s positioning slide and motor, needed to be
designed to allow the operator to position the camera roughly and then fine tune the focus
as needed. The result is a mechanism that allows the motor to be easily disengaged from
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the slide so that the operator can manually position the slide. Reengaging the motor/slide
interface, the operator can focus the camera from the PC workstation via the previously
described electrical circuit mechanism. Considering an electro-mechanical solution
ensured that the design would satisfy the design objective of allowing the camera to be
focused from the location of the PC workstation.
Analysis and synthesis of the tenth and final design objective provided assurance
that the fiber optic cable would not become tangled or be subjected to detrimental
bending as a result of the motion of the assembly. This aspect is of particular concern as
with the claw design the light sheet generator is not stationary. The solution of this
objective is to simply use cable tie straps to fix the fiber optic cable to the light sheet
generator extension arm. In doing so, the metal braided casing on the fiber optic cable
will not be able to kink or become twisted in any manner. Additionally, the rotational rate
of the claw mechanism is very slow and as a result, the possibility for damage is
minimized.
6 Prototype Development
Once the design configuration was finalized with completion of the Analysis and
Synthesis process, the next phase of process was Prototype Development. It was in this
step that the Claw apparatus began to take physical shape as the parts were manufactured
and assembled. Several hours were spent in the machine shop manufacturing parts.
Sometimes the parts were manufactured twice as “rookie” errors made an effort to push
the delivery schedule to the limit. Fortunately, due to a steep learning curve, most of the
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manufacturing errors were made at the beginning of the manufacturing process and were
minimized near the end.
During the manufacturing and assembly process, minor modifications were made to
improve the performance of the Claw apparatus. It was with these modifications that
improvisation and ingenuity played important factors in the development process.
Probably the most significant modification involved changes to the Clamping Block. The
purpose of the Clamping Block was to provide anti-rotation torque to the pivot shaft so
that the Arm Assembly could be held in one position. Unfortunately, the amount of
clamping force required with the existing Clamping Block was too large to effectively
prevent Arm Assembly rotation. As a result, minor changes were made to the Clamping
Block that improved its ability to sufficiently hold the pivot shaft. Realizing that the
block was too stiff to be compressed by the single ¼-20UNC bolt, the block was
machined from 0.5 inches thick to 0.4 inches thick. This reduction in cross-sectional area
effectively weakened the block reducing the amount of clamping force required to hold
stabilize the shaft. Additionally, the stress-relieving slot was lengthened to increase the
leverage of the clamping bolt. Because of these changes, the clamping block, in its
current configuration, effectively prevents Arm Assembly rotation. An illustration of the
Clamping Block modifications is shown in Figure 7.
Figure 7 - Clamping Block Modifications
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A second design modification that resulted from the development process was the
addition of a keyway to the pivot shaft and corner bracket interface. Initially, the design
intent was to thread the end of the shaft and prevent arm assembly rotation by using
clamping friction. Unfortunately, threading the precision ground and hardened pivot shaft
was impossible as the thread machining process was prevented by the hardness of the
shaft. Contrarily, machining a keyway slot in the shaft with a carbide end-mill was a
possibility. As a result, a 1/8” end-mill was purchased and the slot was machined not only
in the shaft but also in the corner brackets of the arm assembly. The addition of this
keyway slot compensated for the inability to add a threaded fastener on the pivot shaft
end. By using a keyway feature, the inadvertent rotation of the arm assembly was
effectively prevented. An illustration of the keyway feature is shown in Figure 8.
Keyway
Figure 8 - Keyway Modification
The last significant design modification pertained to the method in which the model
was supported. The original model support design utilized two simple steel shafts that
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were turned to a cone on one end. These rods protruded through two holes in a “goal
post”-like structure. The positioning of these steel rods was controlled by setscrews
incorporated into the support posts. Unfortunately, this type of support device did not
provide much versatility regarding model configuration or the ability to supply fluid to
the model. As a result, A few design changes were made that improved versatility and
performance of the model support.
To prevent the model from inadvertent rotation, a dry-wall anchor was used. This
drywall anchor incorporates two small metal teeth that help to secure the anchor in a
drywall application. Recognizing that these teeth, when turned outward, would
effectively hold the model in place without distortion, the anchor was incorporated into
the model support. Because the anchor is hollow and can accept a ¼” outside diameter
flow tube, the model could now receive flow through an inlet tube. The anchor is secured
in place by the same setscrew that held the original steel rod in place. The last
modification to the model support involved the incorporation of a threaded rod, opposite
the anchor support. The incorporation of this threaded support bolt increases the
versatility of the model support as many different size and shape models can be used with
one support. The threaded rod was turned to a cone shape on the end that interfaces with
the model to minimize the area of contact with the model and to avoid obstruction of any
of the flow passages. The introduction of these minor but effective modifications to the
model support provided the features necessary to improve the versatility and performance
of the Claw apparatus as a whole. An illustration of the modifications to the support post
is shown in Figure 9.
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Flow Through
Anchor – With
Teeth
Threaded
Rod
Figure 9 - Model Support Modifications
7 Test
To ensure that the Claw apparatus successfully achieved the performance
requirements set forth by the customer, an Acceptance Test Procedure was written that
itemized each individual customer performance requirement. In doing so, quick and
accurate testing of the Claw apparatus was possible. The testing began with a visual
examination of the apparatus to ensure that quality and overall general craftsmanship
were adhered to. Next, since the model must be supported with minimal points of contact,
this feature of the apparatus was inspected. Indeed, the new model support only contacts
the lung model in three small locations and, pursuant to ATP requirement 5.6, the
apparatus can supply flow inlet and outlets to the model as the support mechanism does
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not block any of the flow passages and is held securely enough to not inhibit rotational
and/or translational motion of the model.
Pursuant to the ATP requirements 5.4 and 5.5, the apparatus allows for a minimum
of 90°±0.5° degrees of rotation in each axis and can accommodate three to four inches of
translation freedom in each axis. Since the translational motion is accomplished with
linear positioning slides, the positional tolerance is infinite. Therefore, the requirement of
± 0.005 inches of translational freedom is easily achieved.
Perpendicularity between the camera field of view and the light sheet generator
output is achieved by careful assembly procedures and easily tested using a simple
carpenter’s square. Critical to achieving this requirement, is the construction of the Arm
assembly. To ensure perpendicularity, each component of the arm assembly was
assembled, on a perfectly flat surface, using a carpenter’s square as a template. As a
result, angular tolerance did not accumulate and the camera field of view and the light
sheet generator’s output remain perpendicular to each other.
Adjustability of the camera and light sheet generator is easily verified by inspection
of the components that were used to attach these components to the Arm assembly. The
modular x-channel construction allows for the necessary adjustment with the use of an
Allen wrench. Also easily verified by demonstration is the remote camera focus feature.
By simply viewing the PC monitor while the procedure is underway, the effectiveness of
the motorized camera focus is validated. Rigorously adhering to the Acceptance Test
Procedure ensured that the apparatus achieved all of the customer’s performance
requirements.
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8 Future Design Considerations
The purpose of this section is to provide design improvement recommendations for
future versions of this apparatus. These recommendations do not indicate that the current
product does not meet the customer’s specifications but merely suggest that
improvements to the current design could improve the ease of use of the apparatus.
One of the most significant improvements in ease of use could result from the
incorporation of a worm-gear positioning mechanism between the pivot shaft and
clamping block interface. The inclusion of a device of this type would eliminate the need
for special tools or clamping force to prevent the arm assembly from rotating about the
pivot shaft. Additionally, a worm-gear device would allow for smooth and precise
rotational positioning of the Arm assembly. The benefits of this ability to smoothly
position the Arm assembly would be realized in reduction of steps necessary, by the
operator, to precisely position of the Arm assembly. A wrench would no longer be
necessary to lock the Arm assembly in place and the assembly could be positioned with
one hand rather than two.
A second design improvement would be the incorporation of a modular cradle type
design for the lung model. Currently, repeatability from one experiment to the next
requires that the model be re-positioned from scratch every time. The operator must load
the model and “hunt” for the exact position of a previous experiment. With a modular
cradle assembly, the operator could quickly regain any previous position of the model
without excessive adjustment or “hunting”. The incorporation of this feature would
greatly increase the ease of use of the current apparatus.
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The last design improvement also would increase the repeatability and ease of use of
the Claw apparatus. With the incorporation of graduation markings on the positional
slides, precise re-location of any particular analysis location would be possible. By
simply recording the coordinates of the analyses, the operator could presumably relocated any position that they had previously analyzed. This feature would greatly reduce
set-up time during repetitive measurements.
9 Conclusion
Using a multi-faceted approach to new product development resulted in the final
working product whose intent was to meet or exceed the customer’s performance
requirements. Recognizing these performance requirements as the needs of the customer,
several concepts were developed with the intent of meeting these needs. The concepts
were analyzed for technical and financial feasibility and as a result only one of the
concepts was deemed appropriate to satisfy the customer’s needs.
Several design
objectives and corresponding performance specifications were developed to ensure that
the chosen concept would thoroughly and quantifiably satisfy the customer’s needs. From
these objectives and specifications, several design concerns became apparent and each
was addressed either intuitively or mathematically.
Once the design was finalized,
manufacturing began and the apparatus began to take physical shape. During the
manufacturing process, the need for slight modifications arose and was addressed
accordingly with engineering drawing changes. Assembly provided additional feedback
regarding design improvements and final improvements to the design were incorporated
at that time. Testing represented the final phase in the project. The Claw apparatus was
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subjected to an Acceptance Test Procedure that itemized specific customer performance
requirements. Upon successful completion of the test procedure, the apparatus was ready
for presentation to the customer. The result of this process is a test apparatus that
transformed from a preliminary concept to a robust and mechanically sound design that is
fully capable of satisfying or exceeding the customer’s performance requirements.
10 Acknowledgments
Team 04025 would like to thank the customer, Dr. Risa Robinson, for providing a
challenging and rewarding project to be associated with. By presenting the team with an
opportunity to demonstrate the skills acquired throughout our scholastic careers, Dr.
Robinson has helped the team to learn, grow and develop our engineering character.
Additionally, the team would like to thank Dave Hathaway and Steve for their
expertise, patience and dedication to the success of our project. Without their help, the
Claw would never have materialized into the mechanical apparatus that it is. We are
forever indebted to the care and diligence they provided, even when they were being
pulled in all directions by many different teams.
Finally, the team would like to thank Dr. Nye, Dr. Hensel and all of the remaining
RIT staff and faculty that provided assistance when times were tough. Even though the
spring quarter can be very hectic, our team never seemed to be a lost priority to the
institution. And that is a testament to the dedication that the staff and faculty has for the
success of their students. Thank you to all.
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