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EML 4905 Senior Design Project
A B.S. THESIS
PREPARED IN PARTIAL FULFILLMENT OF THE
REQUIREMENT FOR THE DEGREE OF
BACHELOR OF SCIENCE
IN
MECHANICAL ENGINEERING
Digital Photolithography System Utilizing
Motion Control and Machine Vision
Final Report
Xavier Bercy
William Billini
Ricardo Charlestin
Advisor: Professor Ibrahim Tansel
April 24, 2016
This B.S. thesis is written in partial fulfillment of the requirements in EML
4905. The contents represent the opinion of the authors and not the Department of
Mechanical and Materials Engineering.
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Ethics Statement and Signatures
The work submitted in this B.S. thesis is solely prepared by a team consisting of William
Billini, Xavier Bercy, and Ricardo Charlestin and it is original. Excerpts from others’ work have
been clearly identified, their work acknowledged within the text and listed in the list of references.
All of the engineering drawings, computer programs, formulations, design work, prototype
development and testing reported in this document are also original and prepared by the same team
of students.
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Table of Contents
Abstract ............................................................................................................................... 1
1. Introduction ..................................................................................................................... 2
1.1 Problem Statement ................................................................................................ 2
1.2 Motivation ................................................................................................................. 2
1.3 Literature Survey ................................................................................................... 2
1.3.1 Digital Micromirror Devices .............................................................................. 2
1.3.1 Printing Screen Exposure Process ................................................................... 4
1.3.2 Photolithography ............................................................................................. 6
1.4 Survey of Related Standards ..................................................................................... 7
1.5 Discussion ................................................................................................................. 8
2. Project Formulation .................................................................................................. 8
2.1 Overview ................................................................................................................... 8
2.2 Project Objectives ..................................................................................................... 8
2.3 Design Specifications................................................................................................ 9
2.4 Addressing Global Design ........................................................................................ 9
2.5 Constraints and Other Considerations ...................................................................... 2
3. Design Alternatives ................................................................................................... 2
3.1 Overview of Conceptual Designs Developed ........................................................... 2
3.2 Design Alternate 1 .................................................................................................... 2
3.3 Design Alternate 2 .................................................................................................... 3
3.4 Integration of Global Design Elements ..................................................................... 3
3.5 Feasibility Assessment .............................................................................................. 3
3.6 Proposed Design ....................................................................................................... 4
3.7 Discussion ................................................................................................................. 6
4. Project Management ................................................................................................. 6
4.1 Overview ................................................................................................................... 6
4.2 Breakdown of Work into Specific Tasks .................................................................. 6
4.3 Patent Application ..................................................................................................... 6
4.4 Discussion ................................................................................................................. 7
5. Engineering Design and Analysis ............................................................................. 7
5.1 Overview ................................................................................................................... 7
5.2 Kinematic Analysis and Animation .......................................................................... 7
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5.3 Dynamic Analysis of the System .............................................................................. 8
5.4 Structural Design .................................................................................................... 11
5.5 Force and Stress Analysis ....................................................................................... 12
5.6 Deflection Analysis ................................................................................................. 14
5.7 Material Selection ................................................................................................... 14
5.8 Component Design/Selection.................................................................................. 14
5.9 Design Overview .................................................................................................... 15
5.10 Cost Analysis ........................................................................................................ 15
5.11 Discussion ............................................................................................................. 15
6. Prototype ................................................................................................................. 15
6.1 Overview ................................................................................................................. 15
6.2 Description of Prototype ......................................................................................... 15
6.3 Parts List ................................................................................................................. 16
6.4 Construction ............................................................................................................ 16
6.4.1 Light Engine Construction ............................................................................ 16
7. Testing and Evaluation ........................................................................................... 19
7.1 Overview ................................................................................................................. 19
7.2 Design of Experiments – Description of Experiments ........................................... 19
7.3 Test Results and Data .............................................................................................. 20
7.3.1 Light Engine Test Results and Data................................................................. 20
7.3.2 Machine Vision Test Results and Data ............................................................ 27
7.4 Evaluation of Experimental Results........................................................................ 29
7.4.1 Evaluation of Light Engine Experiment........................................................ 29
7.4.2 Evaluation of the Machine Vision System .................................................... 30
7.5 Improvement of the Design .................................................................................... 31
7.6 Discussion ............................................................................................................... 31
8. Design Considerations ............................................................................................ 31
8.1 Health and Safety .................................................................................................... 31
8.2 Assembly and Disassembly .................................................................................... 32
8.3 Manufacturability .................................................................................................... 32
8.4 Maintenance of the System ..................................................................................... 32
8.4.1 Regular Maintenance..................................................................................... 32
8.4.2 Major Maintenance ....................................................................................... 32
9. Design Experience .................................................................................................. 32
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9.1 Overview ................................................................................................................. 32
9.2 Standards Used in the Project ................................................................................. 33
9.3 Impact of Design in a Global and Societal Context ................................................ 33
9.4 Discussion ............................................................................................................... 33
10. Conclusion .............................................................................................................. 34
10.1 Conclusion and Discussion ................................................................................. 34
10.2 Future Work .......................................................................................................... 34
References ......................................................................................................................... 35
A) Detailed Engineering Drawings ............................................................................... A
B) Multilingual User’s Manual ................................................................................... NN
C) Copies of Used Commercial Machine Element Catalogs ...................................... OO
D) Detailed Raw Design Calculations and Analysis ................................................... QQ
E) Project Photo Album ............................................................................................ WW
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List of Figures
Figure 1-1: Magnified image of DMD [3] .......................................................................... 3
Figure 1-2: Illustration of DMD projection system's light path [4] .................................... 3
Figure 1-3: Stouffer 21-Step Test Method .......................................................................... 7
Figure 1-4: Mil Std-150A pattern used for calibrating optical components ....................... 8
Figure 2-1 : Digital micromirror device trademarked as Digital Light Processing (DLP) by
Texas Instruments Inc. .................................................................................................................... 9
Figure 3-1: International plug identification guide [10]. .................................................... 3
Figure 3-2: The proposed design for the system. ................................................................ 4
Figure 3-3: BeagleBone Black microcontroller [11]. ......................................................... 5
Figure 3-4: EasyDriver – Stepper Motor Driver [12]. ........................................................ 5
Figure 3-5: DLP LightCrafter 4500 light engine [13]. ....................................................... 5
Figure 3-6: Luminus Devices, Inc. CBM-40-UV light engine [14]. .................................. 6
Figure 4-1: Patent Application ............................................................................................ 7
Figure 5-1: Pathway of light engine over screen printing frames. ...................................... 8
Figure 5-2: X-Axis Linear Displacement ........................................................................... 9
Figure 5-3: Z-Axis Linear Displacement ............................................................................ 9
Figure 5-4: X-Axis Linear Velocity .................................................................................. 10
Figure 5-5: Z-Axis Linear Velocity .................................................................................. 10
Figure 5-6: X-Axis Linear Acceleration ........................................................................... 11
Figure 5-7: Z-Axis Linear Acceleration ........................................................................... 11
Figure 5-8: Design of steel frame consisting of 17 elements welded together ................. 12
Figure 5-9: Design of motion control frame ..................................................................... 12
Figure 5-10: Von Mises stress analysis ............................................................................ 13
Figure 5-11: Factor of safety analysis ............................................................................... 13
Figure 5-12: Results of deflection analysis ....................................................................... 14
Figure 6-1: The DLP LightCrafter 4500 after dismantling ............................................... 17
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Figure 6-2: The DLP LightCrafter 4500 optics unit with heat sink and OEM LEDs removed
....................................................................................................................................................... 17
Figure 6-3: A sharp blade modifying the DLP LightCrafter 4500 optics module removing
the OEM plastic stems in order to fit the Luminus Devices, Inc. UV LED ................................. 18
Figure 6-4: DLP LightCrafter 4500 optics module mounted with Luminus Devices, Inc.
UV LED ........................................................................................................................................ 18
Figure 6-5: Side-by-side comparison of OEM blue LED from DLP LightCrafter 4500
optics module and Luminus Devices, Inc. UV LED .................................................................... 19
Figure 7-1: Screen printing frame with green-colored grid pattern .................................. 20
Figure 7-2: Newport Multi-Function Optical Meter Models 1835-C ............................... 21
Figure 7-3: Newport Model 818-IS-1 universal fiber optic detector ................................ 21
Figure 7-4: Light engine positioned 10 cm away from the fiber optic detector ............... 22
Figure 7-5: Graph of UV Intensity vs. Time..................................................................... 23
Figure 7-6: Three screen printing frames prepared for this project .................................. 24
Figure 7-7: DLP LightCrafter 4500 Control Software by Texas Instruments .................. 25
Figure 7-8: Results of five minute exposure time ............................................................. 26
Figure 7-9: Second result of five minutes exposure time ................................................. 26
Figure 7-10: Results from three minutes of exposure ....................................................... 26
Figure 7-11: Results from 90 seconds of exposure ........................................................... 27
Figure 7-12: Test image for machine vision subsystem ................................................... 27
Figure 7-13: Test image for algorithm to superimpose onto screen printing frames ........ 28
Figure 7-14: Resulting image from machine vision algorithm ......................................... 28
Figure 7-15: Successful completion of superimposing the test image onto the frames .... 28
Figure 7-16: Individual pictures generated by raster image processor algorithm ............ 29
Figure 7-17: Relative Power vs Junction Temperature [17] ............................................. 30
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List of Tables
Table 1-1: Major standard development organizations ..................................................... 7
Table 2: Measurements of Intensity vs. Time ................................................................... 22
Table 3: Standards used in the project .............................................................................. 33
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Abstract
This research project demonstrates a digital photolithography system with
integrated machine vision and motion control. The intended industry for this
technology is to be used in screen printing shops around the world. A DLP
LightCrafter 4500 evaluation kit from Texas Instruments was modified and fitted
with a UV LED. The machine vision system was conducted with a webcam and
successfully tested using MATLAB. The images to be projected onto the screen
printing frames are to be projected by the light engine moving by a CNC-like system.
The results of the experiments proved the modified light engine can in fact expose
the photo-resistive material.
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1. Introduction
1.1 Problem Statement
Screen process printing is a process of applying images or patterns onto manufactured
products. Many industries, such as apparel, electronics, and plastics, are well-known for utilizing
this technique to mark their products. The creation of the screen printing media requires expensive
and time-consuming materials such as silver-halide or polyester films. This material, known as the
film positive, contains an image or pattern which is utilized to expose an image onto the printing
screen [1].
Traditionally, the film positive is applied onto the screen which is coated with an ultraviolet
(UV) sensitive polymer. Afterwards, the screen is flood exposed with UV radiation. The aggregate
cost of consumables and its related labor expenditures can become very high for companies. A
cost-effective solution for transferring the image onto the screen printing frame (screen printing
frames) is to project it directly utilizing a digital micromirror device (DMD).
Transferring the image directly onto the media by way of a projection system using a DMD
will save manufacturers money by significantly reducing the number of steps, improving image
quality, and eliminating expensive consumables. Further productivity improvements can be
realized by integrating machine vision and motion control all into one single industrial automated
system.
The system being proposed is an integrated photolithography system utilizing machine
vision and motion control systems. For this project, the scope will focus on projecting patterns
onto the photo-resistive material applied to screen printing framess.
1.2 Motivation
The project’s motivation to innovate the process of exposing printing screens is to eliminate
the consumables such as the film positive, improve a company’s productivity, and improve image
quality. Essentially, the goal of this project is to make printing screens cheaper, faster, and better.
1.3 Literature Survey
1.3.1 Digital Micromirror Devices
Digital micromirror devices (DMD) are micro-electromechanical devices invented by
Texas Instruments Inc. [2]. They consist of an array of microscopic mirrors, with a pitch width
ranging between 10 μm – 17 μm, which are each mounted onto deformable metal hinges. Each
mirror, considered a pixel, has its reflective plane parallel to the DMD’s plane while in a neutral
state. The array of deformable mirrors are capable of tilting on its axis with an angle of ±12°. As
such, each DMD mirror is considered to be both an opto-mechanical and electro-mechanical
element.
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Figure 0-1: Magnified image of DMD [3]
When a pixel is tilted towards the light source it is deemed “on” or in a positive state. A
negative, or “off,” state is when the pixel is tilted away from the light source. The DMD is utilized
as an opto-mechanical device by controlling the tilt of each mirror, light is then deflected off the
mirror towards a projection lens. It is by the aggregate positioning of each pixel’s state in the array
which allows the formation of images to occur.
Figure 0-2: Illustration of DMD projection system's light path [4]
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For this project, a DMD with an array of 912 x 1140 pixels will be utilized to create the
patterns to be projected. It is because of the control of each pixel which makes this technology to
be instrumental for the purposes of photolithography.
Due to the nature of photo-resist materials, polymerization is induced when it receives UV
energy per unit area. Therefore, the position of each mirror will be “on” when the pattern’s unit
area is to be polymerized, and “off” when the unit area of the photo-resist is to remain in an
unchanged phase. This configuration of the DMD system is known as a binary image [5].
1.3.1 Printing Screen Exposure Process
Screen printing is a method of printing graphic images. Its origin can be traced back to
early Japanese and Chinese civilizations who used it to reproduce artwork and to publish posters
with words of wisdom of the emperor. Although it is an ancient process, many innovations and
improvements have been made over the years in materials, techniques, and equipment. Nowadays,
it is the only printing method that allows one to print almost anything including vertical, hard, or
on round surfaces. It has become a major industry which integrates many existing industries like
fashion, design, and sports.
Most of the existing screen printing systems are composed of the following basic components:
1) Artwork. Design on transparent or translucent material.
2) Frame. It may be of wood, metal, or recycled plastic.
3) Screen Mesh. I was originally silk, but nowadays multifilament and monofilament
polyesters are used.
4) Film positive. Used to expose and harden light sensitive emulsion.
5) Squeegee. Basic piece of equipment used for flooding the screen with the ink and printing.
6) Printing press. Where T-shirts are printed.
7) Substrate to be printed.
After the emulsion (photo-resist) is exposed, a stencil remains whereby the mesh is open. The
ink is deposited onto the screen and frame assembly, pressure is applied with a squeegee to push
the ink through those areas which are not blocked by the polymerized photo-resist. When the ink
passes through the surface below (the substrate), that surface is printed with the image defined by
the stencil. The substrate may be T-shirts, paper, glass, plastic, etc. Figure 1-1 demonstrates the
entirety of the screen printing process with a T-shirt as the intended substrate to decorate.
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Figure 0-1 Screen printing life cycle [6]
The process of creating a stencil on a printing screen commences with the application of the
photo-resist onto the mesh. This step in the process is started by coating the screen with a pre-
sensitized emulsion or dry-film photoresist.
Once the photo-resist coats the mesh, a film positive (photomask) is furnished. Modern
techniques utilize wide-format printers to print the image onto polyester film with a sufficient
density of ink to ensure opaqueness. The printed pattern is then cut away from the bulk of the film.
Exposure is then realized by adhering the film positive to the mesh and then flood-exposing
against an actinic light source. Flood exposure units containing a metal-halide light source are
designed so that the lamp effectively irradiates an area sufficient to fit several square feet of
screens. The resulting design allows for a plurality of screens to be exposed as a batch. Figure 1-2
illustrates a screen printing exposure system,
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Figure 0-2 Douthitt Direct Method Screenmaker Model DMA [7]
While flood exposure systems are highly effective in exposing screens, their disadvantages
lie in that they need to be manually calibrated periodically to ensure proper UV dosing. The
standard method to calibrate these systems is by the Stouffer 21-Step process, which will be
discussed in Sect. 1-4. Other disadvantages are that they require added consumables to create the
film positive and have an extra step where a vacuum pump needs to be actuated in order to ensure
proper contact between the mask and screen.
1.3.2 Photolithography
Photolithography is the process of transferring patterns via optical methods onto photo
resistive materials [8]. Historically, photolithography was utilized to etch patterns onto printed
circuit boards starting in the 1970s, known as projection printing. Before then, printed circuit
boards were manufactured using standard lithography methods by utilizing a mask.
The need to change from standard lithography to photolithography was due to damages
caused by direct contact with the wafer and wear and tear on the masks as well [9]. Initially,
photolithography was limited to exposing an entire wafer at one time. Eventually, wafers became
smaller and throughput needed to be increased. Around the mid-2000s, manufacturers such as
ASML/Zeiss, Canon and Nikon began manufacturing systems which exposed wafers in a “step-
and-scan” method. In other words, the lens is scanning across the surface of the wafer.
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1.4 Survey of Related Standards
Standards to be considered for the design of this system are divided into two groups: system
and component standards. Some of the standards which will be followed are regarding safety as
the system will have moving parts, electric motors, and UV radiation.
Major standard development organizations (SDO) to be considered whose standards will be
utilized for the design of the system are the following:
Table 0-1: Major standard development organizations
Oher application specific standards to be considered for this project deal with image
resolution once the photoresist has been exposed. One standard testing method to calibrate UV
flood exposure systems is to utilize the Stouffer 21-Step method (Figure 0-3).
Figure 0-3: Stouffer 21-Step Test Method
Another standard testing method to be used is military standard 150A pattern (Figure 0-4)
which is used to calibrate resolutions of optical systems.
Acronym Organization Name Keyword
AATCC The American Association of Textil
e Chemists and Colorists Test Methods
AIHA American Industrial Hygiene
Association
Occupational health and safety,
worker safety
INCITS International Committee for
Information Technology Standards data interchange, interface
ISA International Society of Automation Automation, Control,
NEMA National Electrical Manufacturers
Association
Electrical, Industrial Control,
Low Voltage Equipment, Motors,
Wire and Cable
UL Underwriters Laboratories Panelboard, electrical
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Figure 0-4: Mil Std-150A pattern used for calibrating optical components
1.5 Discussion
Transposing an image onto screen printing frames is already known by the industry. It is
therefore their vow for engineers to develop affordable system that will help them with their
productivity and get more asset back in return in lesser time. Engineers are studying the possibility
to see how screen printing frames can be made cheaper, faster and better. This can be done by
improving the DMD being used and the printing screen exposure process. From standard
Lithography to photolithography a lot of improvement has been done and a lot more can be done
to improve. With the help of previous research and new experiment result along this project, the
feasibility of an improved system will be documented.
2. Project Formulation
2.1 Overview
The system being proposed is an integrated photolithography system utilizing machine
vision and motion control system. All three major components will operate in an open-loop design.
For this project, the scope will focus on projecting patterns onto the photo-resist material applied
to the screen printing frame.
2.2 Project Objectives
An apparatus containing a DMD, similar to a conventional video projector, is proposed to
project patterns onto a photo-resistive material with UV radiation. This integrated subsystem,
consisting of a DMD, optical components, and the irradiator will be known as the light engine.
The second major component is the motion control system. This system will be designed with two
servo motors to allow for control in two axes.
The light engine will be mounted onto a linear actuator on an axis parallel to the floor. The
projected image plane will be collinear with the floor. A second servo-driven linear actuator will
position the light engine on a vertical axis to ensure the image plane is in focus.
For every increment of motion, the light engine is traversing over the screen printing frames,
on a perpendicular axis, projecting a linear segment of the image. The motion control system will
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essentially synchronize the motion of the light engine and the screen printing frames so that the
image is projected in a serpentine pattern.
The final major component is a machine vision system which will measure the dimensions
and orientation of the screen printing frames. Once these variables have been determined, the light
engine will utilize these coordinates to project the image onto the screen printing frame. This is
the key feature that is not available on screen exposure systems which utilize DMD projection
systems!
2.3 Design Specifications
To decrease the number of steps required to expose an image on to the screen printing
frames, we are going to eliminate the film positive and transfer the image directly onto the media
using a digital micro-mirror device patterns onto a photo-resistive material using ultraviolet
radiation.
Figure 2-1 : Digital micromirror device trademarked as Digital Light Processing (DLP) by Texas
Instruments Inc.
The control system will be designed to include two stepper motors to control the motion in
two axes. A light engine mounted onto a linear actuator will be used on an axis parallel to the floor
and the projected image plane will be collinear to the floor. Finally, a machine vision system will
be used to measure the dimensions and orientation of the screen printing frames. With all variables
determined, the light engine will project the image onto the screen printing frame using the
coordinates determined by the machine vision software.
2.4 Addressing Global Design
In terms of designing a system which can operate on any continent, the only thing that
needs to be considered is the power supplied to the machine. As such, a switching power supply
that is able to be supplied with either 110 V or 240 V will be utilized. It is common for industrial
equipment to be sold without a plug. Thus, the customer would have to furnish their own plug and
connect it to the power supply.
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2.5 Constraints and Other Considerations
Keeping the team productive under tight deadlines requires a systematic method. Each
restraints are studied by the individual in charge of the task along with team members and advisors
to find feasible solutions and considerations to maintain a good project quality. The overall
challenges of this project remains under the “classic project constraints’’ encounter by most project
developers and managers globally: scope, cost and time.
The scope of the project requires knowledge of mechatronics, computer programming,
optical engineering, electrical engineering, and mechanical engineering. Over the recent semesters,
members of this team have acquired knowledge and understanding via courses and further research
projects; a bundle that benefits to the extent of this project but not yet sufficient. For a good
working prototype, hands-on is needed. Unexpected reactions, testing, trial-and-error, failure, are
all expected in the course of this project. The best possible saving decision is a gain because it runs
on a budget set by the team.
To maintain that budget, economic decisions should be firm. The cost of materials, tools
and commodities needed must be the bare minimum without affecting the original quality set for
the project. Time lost cannot be found ever. Team L makes it a priority to stay on top of their
agenda to satisfy their milestone. To avoid maximum constraints, commitment is key. A complete
and working prototype must be delivered on time. It is an original capstone project, new aspects
and approaches will be revealed; however Constraints are expected and will be handled with
professionalism.
3. Design Alternatives
3.1 Overview of Conceptual Designs Developed
The conceptual design developed for this project will be chosen out of two design
alternatives. Each one will differ from the type of light engine and motion control system being
used and how they are each mounted onto the superstructure. A critical cost analysis will be made
along with best result output. Based on the final result and the budget set for this project, the most
suitable one will be picked.
3.2 Design Alternate 1
The first major design that was sought for this project was to mount the light engine over
a conveyor belt. The light engine was to move on a linear actuator which traversed perpendicularly
in relation to the conveyor belt. This design would have required an aluminum flat bed for the belt
to slide on, a drive spindle which moved the belt, and an idle pulley which provided tension in the
belt and also supported the belt on the other end of the system.
This design was not chosen because of the difficulty of finding inexpensive belts and
spindles. Also, there was the risk that if any of these components were to break, it would be very
costly to replace any of the major conveyor belt components. Additionally, the conveyor belt
would require us to measure and ensure a predetermined tension as required by the supplier.
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3.3 Design Alternate 2
The following design alternate which was considered for this project relates to the light
engine itself. An optical module was salvaged from a Panasonic PT-D4000U video projector
which was donated by the university. The projector itself utilizes two 230 W metal-halide lamps
which irradiate UV light in the spectral range of 350 – 420 nm at a high intensity. Additionally,
this projector utilizes an XGA format DMD which measures 0.7 in diagonally.
Although this would have been an ideal light engine to use for this project, three challenges
are presented which would have increased the prototype’s cost. The first challenge is that in order
to use this specific optical module, a programmable XGA DMD kit would be required. For
example, the cost of a Texas Instruments DLP Discovery 4100 evaluation kit would cost at a
minimum approximately $8,000. Secondly, the metal-halide lamps would require a ballast which
would ignite the lamps with 10,000 V that would have presented a safety challenge as well. Lastly,
the overall mass of the optical module would have required a linear actuator that could sustain the
stresses incurred from such a massive object.
3.4 Integration of Global Design Elements
In terms of global design elements considered for this project, a machine which is marketed
to an international market would need a switching power supply. The on-board power supply unit
has a switch which can be toggled between 110 V and 240 V. This would suffice on any continent
to provide power to the system. However, the customer would have to furnish an appropriate plug
for the system which has a load, neutral, and ground connection. For systems operating in North
America, the appropriate plug is a NEMA 5-15P.
Figure 3-1: International plug identification guide [10].
3.5 Feasibility Assessment
In order for this system to be built, the team would need to be experienced computer
programmers in C++ and MATLAB. These programming languages are needed to create the
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machine vision algorithm, program the microcontroller which actuate the stepper motor drivers,
and also to create a custom computer program to control the light engine.
Another skill which the team will have to learn is how to weld structural steel elements,
wiring the electric panel, and assembling the entire superstructure.
A budget of $3,000 is considered suitable to purchase all components required. It should
be noted that for this project, educational donations and discounts were requested regularly.
Lastly, the most important goal of this project is to expose an image onto a screen printing
frame coated with screen printing photo-resistive material. The light source must emit UV
radiation and the patterns must be projected via a DMD.
Considering the aforementioned requirements to build the system, it is quite feasible for
this system to be built by the authors of this report.
3.6 Proposed Design
The proposed design for the photolithography system will utilize a smaller scale motion
control system and a modified, turnkey light engine which was obtained as a donation from Texas
Instruments. The design is similar to a CNC-router which has a gantry which moves the router
horizontally while the gantry itself moves in a perpendicular motion.
The motion control assembly was purchased on eBay and was originally designed as the
motion control system for a CO2 laser engraving system. The motion control assembly is already
equipped with two NEMA 17 stepper motors (Figure 3-2). The motors would be driven by two
EasyDriver by Spark Fun stepper motor drivers (Figure 3-4) which would be controlled by a
Beagle Bone Black microcontroller (Figure 3-3).
Figure 3-2: The proposed design for the system.
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Figure 3-3: BeagleBone Black microcontroller [11].
Figure 3-4: EasyDriver – Stepper Motor Driver [12].
The light engine is a DLP Light Crafter 4500 evaluation kit (Figure 3-5). It is a turnkey
solution which contains optics, LEDs, and a driver board. However, the light engine would need
to have an UV LED installed in place of the blue LED. The UV LEDs were donated from Luminus
Devices, Inc., Inc (Figure 3-6) and can output up to 8 W of UV radiation.
Figure 3-5: DLP LightCrafter 4500 light engine [13].
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Figure 3-6: Luminus Devices, Inc. CBM-40-UV light engine [14].
3.7 Discussion
Upon considering the design alternates and feasibility of building the proposed system, it
is certainly possible to construct such a system within two semesters and within the affordability
of a group of three students. The final design will contain a light engine with a UV LED, two
stepper motors, and a BeagleBone microcontroller.
4. Project Management
4.1 Overview
There are three mechanical engineering students forming this group: Xavier Bercy, William
Billini, and Ricardo Charlestin. A multi-disciplinary approach is necessary for an integrated
industrial automated system. The system will require design and fabrication of hardware
components, assembly of electro-mechanical systems, and computer programming. An overall
management plan mapped out ways of obtaining resources. Each phase is planned and scheduled
to promote noticeable work to help monitor the progression of the project and assure quality. All
the risks involved are discussed to communicate potential issues for resolution. Specific changes
in the scope of this project is allowed with appropriate balance and controls. All information will
be made available upon completion, any changes or updates will be documented. To measure the
success of this capstone project for further improvement, a post implementation review will be
conducted at the end.
4.2 Breakdown of Work into Specific Tasks
The group of three students will separate their work according to with what they feel most
comfortable. William Billini will design the system in SolidWorks, along with their accompanying
simulations. He will also program the light engine, program the microcontroller, and perform the
machine vision experiments. Additionally, he will be responsible for researching and writing the
literature survey for this report.
Xavier and Ricardo will be responsible for finding appropriate standards for this project,
building the prototype, and helping out with the final report
4.3 Patent Application
In anticipation that the intended system is potentially patentable, the process of applying for
a provisional patent was initiated. Before an inventor can apply for a patent of any type, he or she
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must request a customer number through the United Stated Department of Commerce identifying
customer number.
Figure 4-1: Patent Application
4.4 Discussion
Because the group of students is limited in time by only having the space of eight months
to complete this ambitious project, there exists a risk that deadlines may be missed. However,
through the help of faculty, sponsors, sheer determination and luck, the project will be completed
to the best of their abilities.
5. Engineering Design and Analysis
5.1 Overview
In this chapter the engineering design and analysis will be covered. Topics include
kinematic and dynamic analysis, stress analysis, details of the structural design, and other
components which are needed to build the prototype.
5.2 Kinematic Analysis and Animation
The kinematic analysis was done on the path the light engine is to follow. The path can be
described as a serpentine pattern as the light engine first traverses 250 mm along the length of the
gantry, followed by the gantry advancing 38 mm along the positive Z-axis. After the gantry
8
advances forward, the light engine returns to its initial position. It should be noted that the origin
of the light engine path is at the back of the motion control frame and to the left relative to the door
of the enclosure.
Figure 5-1: Pathway of light engine over screen printing frames.
5.3 Dynamic Analysis of the System
This section will discuss the dynamic analysis which was conducted in SolidWorks. Below
are six graphs displaying the linear displacement, velocity, acceleration of the light engine as it
moves through its serpentine path.
9
Figure 5-2 shows a graph of the linear displacement in the x-axis. The light engine moves
back-and-forth between 0 and 250 mm.
Figure 5-2: X-Axis Linear Displacement
Figure 5-3 shows the z-axis linear displacement. Note the staircase pattern of the line. This
indicates that the motion control system pauses periodically as it is moving along the z-axis.
Figure 5-3: Z-Axis Linear Displacement
Figure 5-4 displays the linear velocity along the x-axis. The highest velocity is 93 mm/s.
Figure 5-4: X-Axis Linear Velocity
0.00 2.25 4.50 6.75 9.00 11.25 13.50 15.75 18.00 20.25 22.50
Time (sec)
0
6
123
185
247
Lin
ear
Dis
pla
cem
ent
3 (
mm
)
0.00 2.25 4.50 6.75 9.00 11.25 13.50 15.75 18.00 20.25 22.50
Time (sec)
3
7
113
150
187
Lin
ear
Dis
pla
cem
ent
4 (
mm
)
0.00 2.25 4.50 6.75 9.00 11.25 13.50 15.75 18.00 20.25 22.50
Time (sec)
-93
-46
2
46
93
Velo
city
1 (
mm
/sec
)
10
Figure 5-5 displays the linear velocity along the z-axis. The highest velocity is also 93
mm/s.
Figure 5-5: Z-Axis Linear Velocity
Figure 5-6 displays a graph of the linear acceleration in the x-axis and Fig. 5-7 displays it in the z-
axis.
Figure 5-6: X-Axis Linear Acceleration
Figure 5-7: Z-Axis Linear Acceleration
0.00 2.25 4.50 6.75 9.00 11.25 13.50 15.75 18.00 20.25 22.50
Time (sec)
-1
22
45
69
93
Velo
city
2 (
mm
/sec
)
0.00 2.25 4.50 6.75 9.00 11.25 13.50 15.75 18.00 20.25 22.50
Time (sec)
-218
-129
-40
4
136
Acce
lera
tion
1 (
mm
/sec
**2)
0.00 2.25 4.50 6.75 9.00 11.25 13.50 15.75 18.00 20.25 22.50
Time (sec)
-601
-110
38
87
1
Acce
lera
tion
2 (
mm
/sec
**2)
11
5.4 Structural Design
The structural design of the system will consist of one-inch square tubing. The structure
consists of seventeen lengths of tubing which are to be welded together.
Figure 5-8: Design of steel frame consisting of 17 elements welded together
The frame for the motion control system consists of 5 pieces of extruded aluminum. A ½
in diameter smooth rod is utilized to support the weight of the x-axis stepper motor. Additionally,
a quarter inch steel shaft is fastened to the z-axis stepper motor with a pulley fastened at the far
end.
Figure 5-9: Design of motion control frame
12
5.5 Force and Stress Analysis
Figures 5-10 and 5-11 illustrate the analysis conducted in SolidWorks to determine von
Mises stress and the factor of safety. The simulations were carried only on the bar which serves as
the system’s gantry. The overall system does not experience heavy loads, but the simulation on
the x-axis cross bar was conducted with a downward force of 22 N. This force was selected as a
worst-case scenario if the resulting light engine weighs 5 lbs. The factor of safety is measured to
be approximately 8.5.
13
Figure 5-10: Von Mises stress analysis
Figure 5-11: Factor of safety analysis
5.6 Deflection Analysis
Figure 5-12 illustrates the deflection experienced by the extruded aluminum bar. Applying
a downward force of 22 N results in a displacement at the center of the bar of 1.9 x 10-2 mm.
14
Figure 5-12: Results of deflection analysis
5.7 Material Selection
The materials selected for the superstructure (Fig. 5-8) was chosen to be steel. The reasons
one-inch steel square tubing was selected was because it is less expensive and easier to weld than
aluminum. Also, steel sheet metal was selected to be riveted to the frame.
For the motion control frame (Fig. 5-9), extruded aluminum was selected because it is
relatively easy to assemble the structure and is lightweight. The lightweight properties of
aluminum are desirable to reduce the load on the motors to move the gantry.
5.8 Component Design/Selection
The components to be discussed in this section cover the items to be installed in the
electrical panel, motors, and the light engine.
For the components utilized in the electrical panel, a 12 V switching power supply was
selected because the light engine and stepper motors require a 12 V source.
A BeagleBone Black microcontroller was selected because of its abilities to control the
stepper motor drivers and its ease of programming. Additionally, this microcontroller allows itself
to be controlled via an onboard Ethernet port. Hence, the device can be controlled via a TTY
application such as PuTTY.
The stepper motor drivers selected for this project are the EasyDriver by Sparkfun. They
were selected simply because of their inexpensive price and because there is an example in the text
book Exploring BeagleBone: Tools and Techniques for Building with Embedded Linux [15] which
we followed. As far as stepper motors, two NEMA 17 stepper motors were included with the xy-
15
table which was purchased on eBay. Stepper motors were also desired because of their ease of use
and inexpensive price.
For the light engine, a DLP LightCrafter 4500 evaluation kit was chosen due to its ability
to be programmed and it included all the necessary optics and heat exchanger. It is noteworthy that
it was utilized because Texas Instruments, Inc. was generous enough to donate it to this project.
Additionally, it allowed itself to be modified by replacing the blue LED with a UV LED.
The UV LED, the CBM-40-UV from Luminus Devices, emits UV radiation at the
wavelength of 385 nm. This made it compatible with the photo-resist which requires about 380
nm to polymerize.
5.9 Design Overview
Based on the previous analysis, it is believed that the resulting system will function
properly and be able to survive in an industrial setting. The only concerns which remain are the
longevity of the DMD and the UV LED. The DMD mirrors degrade over time when exposed to
constant UV light. Also, the UV LED is very sensitive to high temperatures
5.10 Cost Analysis
The two most expensive components for this system are the light engine and the UV LED,
which cost $1299 and $135 respectively on DigiKey.com. However, the remaining components
can be purchased on Amazon, eBay and local supply depots. As such, each student is prepared to
fund this project with a total budget of $3000. Additionally, the university is providing $500 to aid
in the costs.
5.11 Discussion
From the information gained in performing engineering analysis, it is safe to say that the
system can handle the loads mounted on the gantry by the light engine. Also, the dimensions of
the outer steel frame will provide adequate space for the components.
6. Prototype
6.1 Overview
In this chapter the prototype will be discussed in detail along with its design characteristics.
The construction process and details of the parts used will also be discussed. Finally, a cost analysis
of the prototype will be covered.
6.2 Description of Prototype
The working prototype of the digital photolithography system includes three subsystems:
A light engine, a video detection system along with a motion control and a CNC super structure.
The light engine model for the system is a DLP LightCrafter 4500 from Texas Instruments
that was donated to the team. The light engine was modified by installing a UV LED from Luminus
Devices.
16
Images for the machine vision will be captured by a webcam with 720P resolution
controlled by MATLAB. The motion control system will powered by two NEMA 17 stepper
motors move to allow the light engine to move in a serpentine pattern underneath the camera. The
motion control as whole will be controlled by a BeagleBone black microcontroller board purchased
from Amazon connected to two stepper motor drivers. A steel frame superstructure 26 x 18 x 26
inches made of steel square tubes wrapped with sheet metal reflects the visual appearance of the
prototype as designed preliminary.
6.3 Parts List
6.4 Construction
The project started with eight pieces of square tube plain steel measuring 0.6 inch in width,
0.06 inch in depth and 36 inches in height. Each of these square tubbed steel were cut with a cutting
wheel. The pieces were then assembled into a frame using a welding machine. The dimensions
were 26 x 18 x 24 inch. The second part of the prototype involved the motion control. The motion
control needed to be added to the frame.
The motion control was careful placed into the frame. From which an approximation was
made on the hole for the screws. The holes were punctured with a drill. After the holes were made,
screws were used in order to secure the motion control on the frame.
6.4.1 Light Engine Construction
Light engine supplied by Texas Instruments needed to be modified as to be able to emit
UV radiation. To do this, the optical module needed to be disassembled to remove the blue LED.
Once the UV LED was installed in its place, thermal paste was spread on the back portion before
installing its heatsink.
Part List Donated? Qty Unit Cost Extended Cost
DLP Light Crafter 4500 Yes 1 $ 1,299.00 $ 1,299.00
K40 laser XY table No 1 $ 109.00 $ 109.00
Luminus Devices, Inc.
CBM-40-UV LED Yes 2 $ 135.41 $ 270.82
Steel Square Tube 72" No 4 $ 10.82 $ 43.28
Aluminum Metal Steel No 3 $ 21.98 $ 65.94
Logitech USB WebCam Yes 1 $ 14.99 $ 14.99
BeagleBone No 1 $ 50.00 $ 50.00
EasyDriver No 2 $ 7.00 $ 14.00
Total Cost $ 1,867.03
Total Cost After Donation $ 282.22
17
Figure 6-1: The DLP LightCrafter 4500 after dismantling
Figure 6-2: The DLP LightCrafter 4500 optics unit with heat sink and OEM LEDs removed
18
Figure 6-3: A sharp blade modifying the DLP LightCrafter 4500 optics module removing the
OEM plastic stems in order to fit the Luminus Devices, Inc. UV LED
Figure 6-4: DLP LightCrafter 4500 optics module mounted with Luminus Devices, Inc. UV LED
19
Figure 6-5: Side-by-side comparison of OEM blue LED from DLP LightCrafter 4500 optics
module and Luminus Devices, Inc. UV LED
7. Testing and Evaluation
7.1 Overview
In this chapter, the design of experiments will be discussed.
7.2 Design of Experiments – Description of Experiments
For this system, there are three major subsystems which need to be proven experimentally.
However, only two of the subsystems – the light engine and machine vision – were able to be
completed. The motion control system was not able to be demonstrated experimentally. That is,
the motion control did not receive the intended coordinates which were to be determined by the
machine vision algorithm.
For the light engine, three experiments were completed. The first experiment was to
measure the UV intensity leaving the projection lens at a distance of 100 mm. The second
experiment for the light engine was to prove that the completed light engine could in fact expose
an image onto the photo-resist. Finally, the third experiment was to create a computer program
which would upload a series of frames which are to be created by the machine vision subsystem.
Similar to the light engine subsystem, there were three experiments for the machine vision
subsystem. The first experiment was to be able to capture an image with a USB webcam and
determine the centroid and orientation (angle relative to the edge of the image) of each screen
printing frame. The second experiment was to utilize the coordinates determined from the first
experiment and place and create a new image with a test image and superimpose it where the
frames would be located. Lastly, the third experiment was to create a series of images which are
to be uploaded to the light engine for projection onto the screen printing frames.
20
7.3 Test Results and Data
In this section, the test results and data are presented for the experiments conducted on the
light engine and machine vision subsystems.
7.3.1 Light Engine Test Results and Data
The first experiment for the light engine subsystem was to measure the intensity leaving
the light engine at a distance of 10 cm. The distance of 10 cm was chosen because the light engine’s
projection lens provided the smallest image width and still provide acceptable focus. As seen in
Figure 7-1, a green-colored grid pattern was projected onto the screen printing frame. The focus
was adjusted until the pattern became clearly focused. Afterwards, a ruler was utilized to measure
the distance between the projection lens and the screen printing frame.
Figure 7-1: Screen printing frame with green-colored grid pattern
The experiment to measure the intensity of the UV radiation was conducted in a dark room
utilizing a Newport Multi-Function Optical Meter Models 1835-C along with a Newport Model
818-IS-1 universal fiber optic detector (Fig 7-3).
21
Figure 7-2: Newport Multi-Function Optical Meter Models 1835-C
Figure 7-3: Newport Model 818-IS-1 universal fiber optic detector
The light engine with the UV LED were mounted on a laboratory table with the fiber
optic detector’s objective lens situated at a distance of 10 cm from the projection lens of the light
engine (Fig 7-4).
22
Figure 7-4: Light engine positioned 10 cm away from the fiber optic detector
Four trials were conducted to measure the intensity in μW and the values were recorded in
intervals of 30 seconds. The results show that as the temperature of the LED increased, its output
power decreased as a function of temperature. This was to be expected as the manufacturer
provided output power versus temperature of the LED. The temperature was measured using an
infrared laser thermometer with its objective lens pointing at the UV LED as close as possible
without touching the light engine to avoid altering the distance its distance from the fiber optic
detector.
Table 2: Measurements of Intensity vs. Time
Time
(s)
Trial 1
(μW)
Trial 2
(μW)
Trial 3
(μW)
Trial 4
(μW)
0 4.8 4.9 4.9 4.8
30 4.7 5 4.9 4.5
60 3.8 4.5 4 3.1
90 2.2 2.9 2.4 1.8
120 1.5 1.8 1.5 1.3
150 1.1 1.3 1.2 1
180 0.94 1 0.95 0.86
23
Figure 7-5: Graph of UV Intensity vs. Time
Table 2 lists the values of intensity recorded in intervals of thirty seconds and Fig 7-5 shows
a graph of the values from the table.
The second experiment for the light engine subsystem was to determine if the DMD light
engine can in fact expose an image into the photo-resist. The photo-resist used for this experiment
was donated by Ulano Corporation; a manufacturer and distributor of screen printing consumables.
The specific photo-resist is a capillary film with the product name CDF Vision-15. For this, screen
printing frames needed to be constructed from square wooden dowels measuring 5/8 in thick.
The screen printing frames for this experiment were to have approximate dimensions of 6
x 3 x 0.625 in. The pieces of wood were cut at a 45° angle using a miter saw. Afterwards, the
lengths of wood were stapled together on both sides. Upon completion, a sample of screen printing
mesh which was obtained from a local screen printing shop was stretched over the wooden frames
tightly and stapled in place. The make and model of the screen printing mesh is Saati Saatilene
Hitech 330.34 UO PW.
0
1
2
3
4
5
6
0 20 40 60 80 100 120 140 160 180 200
Inte
nsi
ty (μ
W)
Time (s)
UV Intensity vs Time
Trial 1 (μW) Trial 2 (μW) Trial 3 (μW) Trial 4 (μW)
24
Figure 7-6: Three screen printing frames prepared for this project
Upon completing the construction of the screen printing frames, nine screen printing
frames in total were furnished. The subsequent step is to remove the oils impregnated into the
fibers which aids in the manufacturing process. This was done by spraying a degreaser which
contains sodium hydroxide, similar to what is used to remove oil stains from driveways. The
degreaser was allowed to set into the mesh and was then gently scrubbed with a scrubbing brush
followed by a thorough rinsing with tap water.
Finally, the capillary film was cut into rectangles measuring 1 x 1.5 in approximately. The
strips were placed on top of the wet mesh and then pressed with a squeegee to ensure proper
adhesion to the mesh. Afterwards, the screens were allowed to air dry overnight [16].
The following day, the screen printing frames with the photo-resist were setup in a
darkroom. The frames were stood up on edge lengthwise and were placed 10 cm in front of the
light engine’s projection lens. The goal was to expose an image into the photo-resist. Thus, a grid
pattern which is a test pattern installed in the internal memory of the light engine was projected
onto the screen printing frames one-at-a-time. The light engine can be controlled with software
provided by Texas Instruments called DLP LightCrafter 4500 Control Software. The software was
set to an Operating Mode of Video Mode and the checkerboard pattern was selected from the
Internal Test Pattern in the Source Select menu. As for the power output of the UV LED, a value
of 255 (maximum power) was selected in the LED Driver Control.
25
Figure 7-7: DLP LightCrafter 4500 Control Software by Texas Instruments
Once the instructions are sent to the light engine via a USB cable, the exposures were
timed. Four screens were exposed with the following times: 5 min, 5 min, 3 min, and 90 seconds
respectively. Once the screens were exposed, they were rinsed with tap water until the images
appeared. The following figures shows the results of the experiments.
26
Figure 7-8: Results of five minute exposure time
Figure 7-9: Second result of five minutes exposure time
Figure 7-10: Results from three minutes of exposure
27
Figure 7-11: Results from 90 seconds of exposure
7.3.2 Machine Vision Test Results and Data
There were three experiments for the machine vision subsystem. The first was to test the
algorithms ability to determine the centroid and orientation of the screen printing frames in an
image. The second experiment was to create a new image placing an outside image or pattern
utilizing the coordinates determined from the first experiment. Lastly, the machine vision
algorithm was to generate individual images to be projected by the light engine similar to a video
projector.
To commence the machine vision experiment, a webcam was placed over the frames which
were mounted on a flat surface. The program was developed using MATLAB and was able to
control the camera and generate images. Figure 7-12 shows the initial image captured by the
webcam. Figure 7-13 shows the bitmap image which was created using a separate image
processing software. The goal is to place the bitmap image onto the image of the screen printing
frames properly oriented relative to each frame.
Figure 7-12: Test image for machine vision subsystem
28
Figure 7-13: Test image for algorithm to superimpose onto screen printing frames
Figure 7-14 displays the modified image of the screen printing frames by isolating their
shapes. Finally, the algorithm successfully placed the test image on the rectangular objects taking
into account the proper orientation relative to each screen printing frame.
Figure 7-14: Resulting image from machine vision algorithm
Figure 7-15: Successful completion of superimposing the test image onto the frames
Finally, the third experiment for the machine vision system is to generate a series of new
bitmap images. This was accomplished by dividing the previous image (Fig 7-15) into a series of
matrices measuring 912 x 1140 pixels. Each subsequent image was created by indexing its
corresponding matrix by 10 pixels horizontally. When the row of images, measuring 1140 pixels
reached the far end of the image, the matrix was indexed downward 1140 pixels and the generation
of images was commenced in the following direction. In other words, the images moved from left-
to-right and then right-to-left on the subsequent row. The bitmap images were stored into a folder
location as pictured in Figure 7-16.
29
Figure 7-16: Individual pictures generated by raster image processor algorithm
7.4 Evaluation of Experimental Results
7.4.1 Evaluation of Light Engine Experiment
The first experiment was intended to measure the output power of the UV LED. This was
necessary to calculate the time needed to expose the photo-resist. The project’s goal was to expose
the photo-resist as quickly as possible. Thus, the higher the output power in the wavelength of 385
nm, the faster the photo-resist polymerized. The photo-resist’s required power to cross-link was
12 mW / cm2. Hence, if the output power is 12 mW, then the photo-resist would polymerize in one
second. Furthermore, if the output power is 24 mW, then it would take half a second to expose.
The test equipment revealed that the maximum output power was measured to be 5 µW.
However, this does not appear to be correct because at that power level, the photo-resist would
require 40 minutes to expose! On the other hand, the photo-detector revealed that the LED’s output
power decreased as a function of junction temperature. The decrease in output power was expected
as mentioned in the LED’s datasheet [17].
30
Figure 7-17: Relative Power vs Junction Temperature [17]
It was also discovered after the experiment was conducted that the fiber optic detector is
calibrated for wavelengths from 400 – 1600 nm [18]. Obviously, if the light emitted is outside of
this range, the output power cannot be measured. It is believed that what was measured were
harmonic frequencies emitted by the light engine’s optics. Despite not being able to directly
measure the wavelength of interest, the results did provide insight into the power decreasing as the
LED heated up.
The following experiment of exposing an image directly onto the screen printing frame
was to simply prove that the modified light engine does in fact work. Four tests were conducted
with an image projected onto the photo-resist with time intervals of 5 min, 5 min, 3 min, and 90
seconds. The first two frames were successfully exposed, the third frame presented fair results,
while the last frame presented unsatisfactory results.
What this experiment proves is that the light engine is outputting UV radiation at the
wavelength of 385 nm with sufficient power such that the photo-resist polymerizes. Unfortunately,
this experiment would require a trial-and-error method to determine the optimal time for the light
engine to adequately polymerize the photo-resist. However, that was not the goal of this
experiment as better optical measuring instruments would be needed to measure the output power.
7.4.2 Evaluation of the Machine Vision System
The results of the machine vision experiments proved to be successful. The first experiment
was to capture an image of three screen printing frames and determine the coordinates of the
centroid and their respective orientation relative to the horizontal axis of the image plane.
MATLAB provides functions for image processing and proved to be relatively easy to develop.
The algorithm consisted of 38 lines of code and also output an image of the geometry.
31
The results of the experiment to create an algorithm which imported an image or pattern
with the intent to expose onto a screen printing frame also proved to be successful. The test image
was imported by the algorithm in MATLAB, placed the center of the test image on the centroid of
each screen printing frame in the initial photograph, and rotated each test image to align properly
to the screen printing frames.
The results from the previous experiment were then utilized for the third experiment which
was to “chop” the image into a series of images – each with dimensions of 912 x 1140 pixels. The
goal of this experiment was to generate a series of frames to be uploaded to the light engine. The
idea is to create a movie to be projected onto the screen printing frames.
7.5 Improvement of the Design
This project required the design of three subsystems to work together as an integrated
industrial system. Unfortunately, the prototype which was built could not expose the screen
printing frames in a step and scan manner due to limitations of the light engine’s optics and UV
source.
Suggested improvements for the light engine are to design a projection lens which permits
the UV radiation to be emitted without absorption by the optics. A larger DMD is also suggested
which is specifically designed for UV applications would be optimal. Additionally the UV source
should be a 200 – 300 W metal halide lamp to provide a very high output of UV power, or an array
of LEDs with an optimal heat sink would be recommended.
Improvements to the machine vision system is to utilize a camera which is specifically
designed for industrial applications. The image should then be sent to a standalone application,
rather than manually running three separate algorithms.
Lastly, the motion control system would benefit from higher quality stepper motors and
stepper motor drivers. The microcontroller should be replaced with a programmable logic
controller.
7.6 Discussion
A majority of the experiments were completed successfully. The modified light engine
proved to be capable of exposing the screen printing photo-resistive material. Additionally, the
machine vision algorithms proved to be very successful with potential uses in industrial settings.
8. Design Considerations
8.1 Health and Safety
It is known by the board on safety codes and standards (BSCS) that any built system is
required to follow standards that will assure end users safety. When it comes to electro mechanical
system, any malfunction or mal-operation can trigger danger that can lead to harmful injuries or
death. For this prototype, the team made sure that all the general safety guidelines and procedures
for electrical and mechanical were respected throughout the whole system. A well-insulated panels
on which all the electrical wires and components were mounted separate from the motion control
32
station. The xy-table meet the ASME B20 safety standards for motion control table. The prototype
is safe to operate and should be handled with care.
8.2 Assembly and Disassembly
To assemble and disassemble the prototype is made easy. Presetting of the manufactured
superstructure built from scratch also made it time efficient. The motion control is one piece
structure that can be bolted onto the superstructure at its four corners. The electrical panel is also
made easy to come off. It is screwed onto the superstructure in a well-designed area that the sheet
panel can be remove easily through the accessible door. Few of the electrical components are
installed on the panel with standoffs and others glued directly to the panel. The doors are attached
to the body using hinges that can also be easily unscrewed. The metal sheet that is enwrapping the
superstructure cannot be assemble nor disassemble because a permanent fastener was used to
attached it to the body.
8.3 Manufacturability
The development of this project has been a subject of much research. All the details and
process plan needed to be generated since the beginning. An estimation and analysis of the most
affordable and most efficient proposed designed were picked. The team simplified the design and
reduced few part for cost and ease of fabrication. To manufacture such prototype, it requires all
the materials listed in parts, a team of welder to build the superstructure, an electrical engineer for
the wiring, a programmer for the light engine and the motion control and an assembly team to put
everything together.
8.4 Maintenance of the System
8.4.1 Regular Maintenance
The only part that would require a regular maintenance would be on the X-Y table. The
number of movement that is happening in the X-Y direct of the table would require daily inspection
to make sure that it runs properly. Because of the power and vibrations of the system, daily
maintenance would include to check the motors, belts, and loose screws.
8.4.2 Major Maintenance
Major maintenance should happen for at least a couple of years. It would mainly rest on
the regular maintenance which was given to the system. The maintenance would occur on the
electrical panel. After long use of the system, damage would bound to happen on the wires and
blow up fuses. The yearly maintenance would include to switch the beagle bone black, easy driver,
wires, and power supply.
9. Design Experience
9.1 Overview
In this chapter the design experience will be summarized. Topics to be covered are
standards used in designing the prototype, life-long learning experiences and other subjects
relating to the overall experience for the team members.
33
9.2 Standards Used in the Project
Few standards had to be followed to safely build and incorporate the mechanical and
electrical components of the system. Standards from the American society for testing and materials
(ASTM), Underwriters Laboratory (UL) and few electrical safety standards from UL, a global
independent safety science company have been found and listed below.
Table 3: Standards used in the project
SDO Standard Title
American Welding Society AWS D01.1 Structural welding Steel
American Society for Testing and Materials
F593 - 13a
Standard Specification for
Stainless Steel Bolts, Hex
Cap Screws, and Studs
American Society for Testing and Materials
ASTM Standard B 258-02 Wire gage
Underwriters Laboratory UL61058-1 Switch
Underwriters Laboratory UL20 General use for snap
switch
Underwriters Laboratory UL 10004-6 Standards for servo and
stepper motors
9.3 Impact of Design in a Global and Societal Context
With the distribution of this technology in screen printing shops throughout the world, that
would reduce the demand for polyester film and their related chemicals to produce film positives.
That would contribute by lessening waste heading to landfills and the consumption of energy used
in manufacturing these consumables.
Also, it would boost productivity at screen printing shops, increasing profits for those
companies. It can be said that those companies can pay their existing employees a higher wage,
and aid in preventing screen printing shops around the world from becoming bankrupt.
The latter statement of potentially increasing wages of those working at screen printing
shops is arguable, but there is a definite benefit in terms of environmental impact by eliminating
the need for consumables used in creating screen printing frames.
9.4 Discussion
The senior design project was a lifelong experience for the team. As a team of mechanical
engineers, the team had to work together outside of their comfort zone to complete the tasks. The
project tasks were to weld, program the equipment, create machine vision algorithms and . Without
any idea how to weld or program the team took the challenge. With a lot of research and hard
work, the team managed to complete the required tasks for the project. The welding learning
experience was fun when building the superstructure. As for the programming learning experience,
34
the team worked hard on developing the code to make the system work. Doing these activities
provided the team with real life engineering experience. As such, the team members can state that
they have experience with welding, building industrial systems, screen printing and
photolithography.
10. Conclusion
10.1 Conclusion and Discussion
In conclusion, the team was able to complete the arduous task of completing the senior
design project. Designs and simulations were made before the prototype was built.
10.2 Future Work
Future work for this research project are to make improvements to the light engine by
designing better optics intended for UV lithography applications. Additionally, there are potential
improvements that can be made to the motion control system. Such as feeding the screen printing
frames onto a conveyor belt to further boost productivity.
35
References
[1] A. Kosloff, "Screen Printing Electronic Circuits," Chicago, The Signs of
the Times Publishing Co., 1968, p. 52.
[2] M. S. Brennesholtz and E. H. Stupp, "Micro-electromechanical Devices,"
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[3] Electronic Design, "DLP Shines the Light on Automotive HUDs | Displays
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http://electronicdesign.com/displays/dlp-shines-light-automotive-huds. [Accessed
April 2016].
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(DMD) Technology, Dallas, 2013.
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Technology," Texas Instruments Inc., Dallas, 2008.
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[Accessed April 2016].
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Washington, SPIE Press, 2010, p. 1.
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International Society for Optical Engineering, Washington, 2007.
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36
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[18] Newport Corporation, Newport Model 818-IS-1 universal fiber optic
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A
A) Detailed Engineering Drawings
B
C
D
E
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G
H
I
J
K
L
M
N
O
P
Q
R
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T
U
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B) Multilingual User’s Manual
To start the system:
1. Connect the power cord plug into an AC power source
2. Turn on the switch in the back
To prepare the Frames:
1. Open the front door
2. Load the frames
3. Close the door
4. Load up the machine vision in MATLAB
A. Run software
B. Run the software to determine the orientation and coordinates of the frames
C. Upload image frame onto light engine using custom software
5. Activating Motion control
A. Open up PUTTY
B. log into the Beaglebone black via Ethernet to run the motion control sequence
6. Removing frames
A. Once the exposure process is finished, stop the machine, remove the frames and
develop them according to the photo-resist manufacturer’s instructions
Manuel d’utilisateur
Pour démarrer le système:
1. Branchez le cordon d'alimentation à une source d'alimentation en courant alternatif
2. Allumez l'interrupteur à l'arrière
Pour préparer les cadres:
1. Ouvrez la porte d'entrée
2. Chargez les cadres
3. Fermez la porte
4. Chargez la vision de la machine dans le logiciel MATLAB
A. Run
B. Exécutez le logiciel pour déterminer l'orientation et les coordonnées des cadres
C. Ajouter l'image cadre sur le moteur de lumière en utilisant un logiciel
personnalisé
5. Activation de mouvement
A. Ouvrez PUTTY
B. connecter au BEAGlight engineBONE noir via Ethernet pour exécuter les
séquences de
mouvement
6. Retrait des cadres
A. Une fois que le processus d'exposition est terminée, arrêter la machine, retirez
les cadres et les développer selon les instructions du fabricant de la résine
photosensible
OO
C) Copies of Used Commercial Machine Element Catalogs
Figure D-1: Amphenol LVDS Cable, P/N 7804-01
Figure D-2: DLi Catalog print out of DMD assembly
PP
Figure D-3: DLi 3000 Industrial DMD Driver Board
D) Detailed Raw Design Calculations and Analysis
Figure E-1: Initial cost improvement calculations
RR
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Figure E-2: Steps and Pixel Dimensions
SS
Figure E-3: Estimated Line Width
TT
Figure E-4: DLi3000 Pinout Plan
UU
Figure E-5: DMD pixel relation. Necessary to understand bitstream and clock relations
VV
Figure E-6: Exploded view from Panasonic PT-D5700 Service Manual
WW
E) Project Photo Album
Figure F-1: Initial drawing of system
Figure F-2: Testing of TI Discovery 3000 evaluation board in laboratory
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Figure F-3: Test pattern loaded onto DMD confirming system is functional
Figure F-4: Test pattern loaded after TI Discovery 3000 kit was setup at home
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Figure F-5: TI Discovery 3000 setup with power and Xilinx Platform USB interface
Figure F-6: Xilinx Virtex 4 IO Configuration Map
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Figure F-7: Internal components of Panasonic PT-D4000U
Figure F-8: materials and equipment to build the frames
F)
AAA
Figure F-9: welding process
Figure F10: grinding process
BBB
Figure F11:Steel frame
Figure F 12: Evolution of steel frame as sheet metal being riveted
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Figure F13: mounting of doors
Figure F14: Preparing frames
DDD
Figure F15: assembly of the motion control