Because Solid Freeform Fabrication (SFF) has an extremely wide range of potential applications,
crossing traditional engineering and science boundaries, it is a technology that lends itself to
multi-disciplinary activities and projects. SFF is an ideal mechanism to present scientific
concepts including materials science and mechanics, as well as larger-scope engineering topics
such as agile manufacturing. At Milwaukee School of Engineering (MSOE), we are using SFF
technologies as a means to teach engineering concepts to undergraduate students through multidisciplinary research.
MSOE was awarded a five-year grant under the NSF Research Experiences for Undergraduates
Program (EEC-9619715) to facilitate student exploration in the field of Solid Freeform
Fabrication. Sixty undergraduates will participate in summer and academic year programs by the
year 2001. Eighteen students from around the country have participated in the program to date,
bringing with them a diverse background of university experience, skill level, and interests.
Working closely with a faculty advisor possessing expertise in a particular research area, they
have performed research on Solid Freeform Fabrication applications in the biomedical,
aerospace, architectural, manufacturing, and electronics industries.
Some ofthe keys to the success of this program include:
• Hands-on access to Solid Freeform Fabrication equipment through the facilities
ofthe MSOE Rapid Prototyping Center (SLA 250, LOM 2030, and FDM 1650).
• Close partnerships of the students with faculty and industry mentors in
specialized areas of expertise.
• Teaming with other educational institutions.
• Significant cross-pollination between projects; faculty from diverse
departments.
• Encouraging students to publish and present results at national conferences and symposia.Mechanical Engineerin

Crockett, R.S.

Gervasi, V.R.

English

Texas ScholarWorks

SOLID FREEFORM FABRICATION RESEARCHIN ENGINEERING EDUCATIONR.S. Crockett, V.R. GervasiRapid Prototyping CenterMilwaukee School of Engineering, Milwaukee, WIMilwaukee School of Engineering (MSOE) has been using Solid Freeform Fabricationtechnologies as a means to provide stimulating, multi-disciplinary research topics forundergraduate engineering students. SLA, LOM, and FDM have enabled undergraduate researchin disciplines including Architecture: using SFF for preservation, archiving, and reproduction ofhistorical features; Microelectromechanical Systems: producing packaging and interconnects forMEMS devices through a combination of stereolithography and photolithography; andBiomedical Engineering: creating forensic, research, and educational models of anatomicalfeatures and pathology development from MRI images. In addition, MSOE is currently involvedin a joint program with the Milwaukee Discovery World Museum to create a SFF experimentthat will fly on the Space Shuttle as a Get Away Special payload.IntroductionBecause Solid Freeform Fabrication (SFF) has an extremely wide range of potential applications,crossing traditional engineering and science boundaries, it is a technology that lends itself tomulti-disciplinary activities and projects. SFF is an ideal mechanism to present scientificconcepts including materials science and mechanics, as well as larger-scope engineering topicssuch as agile manufacturing. At Milwaukee School of Engineering (MSOE), we are using SFFtechnologies as a means to teach engineering concepts to undergraduate students through multi-disciplinary research.MSOE was awarded a five-year grant under the NSF Research Experiences for UndergraduatesProgram (EEC-9619715) to facilitate student exploration in the field of Solid FreeformFabrication. Sixty undergraduates will participate in summer and academic year programs by theyear 2001. Eighteen students from around the country have participated in the program to date,bringing with them a diverse background of university experience, skill level, and interests.Working closely with a faculty advisor possessing expertise in a particular research area,theyhave performed research on Solid Freeform Fabrication applications in the <biomedical,aerospace, architectural, manufacturing, and electronics industries.Some of the keys to the success of this program include:• Hands-on access to Solid Freeform Fabrication equipment through the facilitiesof the MSOE Rapid Prototyping Center (SLA 250, LOM 2030, and FDM 1650).• Close partnerships of the students with faculty and industry mentors inspecialized areas ofexpertise.• Teaming with other educational institutions.229'" Significant cross-pollination between projects; faculty from diversedepartments.'" Encouraging students to publish and present results at national conferences andsympoSIa.ProjectsArchitectureare potentially numerous applications for Solid Freeform Fabrication the architecturalis the archiving, and duplicating historical architecturalas rosettes or -- tasks that are currently performed by labor-intensivehand operations. While architects may not talk terms "reverse engineering, parametric dataarchival, and low-volume production", these are all problems that have addressed for theindustry using techniques.project applies to the restoration and replication of architectural pieces and artwork.is especially challenging in that it requires the three-dimensional input of existing objects inmultiple scales: entire buildings to very small detail features. An additional challenge is inu fO-, digital input compatible with the paradigms of the architectural field, such as existingsoftware and processes. This project analyzes the feasibility of obtaining three-dimensional datausing methods ofphotogrammetry, compatible with standard photographic techniques, to quicklyand easily archive and reproduce architectural features.digital photos was of architectural details from different angles. CommercialPro) was used to triangulate common reference points from photos,a mesh which is output directly to an file. A LOM part was created fromthis file, which served as a pattern a silicone mold to create multiple reproductions in plaster1). computer surface model can remain with architectural to retrieved......v' ............. ""'...... (size, mirror-image, mold, etc.) for any future client.Figure 1. Computer file (inset) obtained from Photogrammetry techniques. LOM masterpattern (left), original plaster item (right).230Microelectromechanical SystemsMicroelectromechanical systems (MEMS) are devices and pumpsetched onto a silicon wafer with features as small as 1 these extremelysmall systems with the outside world is the most costly a MEMS design. This projectendeavors to reduce costs by using a modified stereolithography technique. Currently,stereolithography has planar resolutions on the order of 500 ~m, which is not precise enoughto create MEMS features. Increasing the resolution by combining stereolithography with amasking technique allows a single manufacturing system to construct not only the MEMSsensors, but also the interfaces and protective packages.Figure 2 shows the results of initial exploration into using a micron-detail photo mask withstereolithography resin. Working with Process Technologies, Inc. of Milwaukee, multiple-layer parts were prepared by shining UV light through a mask that contained a test patterntypically used the semiconductor industry. Features as small as 5 ~m in-plane wereachieved, and the creation of multiple layers was only limited by the positioning accuracy ofthe physical apparatus used to hold the mask. With a more precise mechanism, multiplelayers at this resolution can be manufactured, creating what are in effect high-aspect-ratioMEMS devices. As aspect ratio is a key limitation in current MEMS manufacturingtechnology, techniques can potentially offer some significant advantages.The ultimate goal of this project is to create objects that have features spanning multipleorders of magnitude. building larger-scale features with the scanning stereolithographylaser, then inserting a photo mask in the beam path as required, this goal should beachievable. It should thus be possible to use a modified stereolithography apparatus to create10 cm objects that contain features on the order ~m.231Biomedical EngineeringThe Medical College of Wisconsin has served as a partner in the exploration of a variety ofBiomedicaLapplications of Solid Freeform Fabrication, Current efforts focus on constructingsolid model data from combined medical imaging modalities such as MRI and CT scans, andthen using this information to create complex composites that accurately replicate the non-homogeneous mechanical properties of bone,One student project is working on automating methods to distinguish the boundaries ofanatomical structures in MRI images, Because MRI images are not homogeneous, much manualeffort is required to .select the desired anatomical structure using software such as MIMICS(Materialize, Inc,), Figure 3, top left shows the original MRI image of a knee, A threshold levelmust be set within the software to isolate desired features, As Figure 3, bottom left shows, asingle threshold level is generally not sufficient to correctly identify a desired structurethroughout the scan, In this picture, the bone was the target structure; most of the materialmeeting the threshold criteria was non-bone, thus an operator must manually isolate the structureslice-by-slice,A computer program was developed by the student that uses a K-mean segmentation algorithmto analyze and "homogenize" pixel values associated with different structures in MRI images,This program uses data from the MIMICS format as an input, reduces the total number of pixelvalues from 4095 levels of gray to a user-defined, more manageable set (usually 3-20), and thenre-introduces the data back into the MIMICS software for display, structure selection, and ,stlFigure 3. Top left: Original MRI image; top right: homogenized image; bottom left: thresholdingon original image misses bone; bottom right: correct features are captured in homogenized image,232file construction. Figure 3 shows the results of initial efforts. The figure in the upper right is thesame MRI image homogenized to 3 grayscale values. The figure in the lower right is the resultafter this data has been imported back into MIMICS and an appropriate threshold value has beenapplied. In this example, the desired bone structure has been correctly identified with minimummanual manipulation.Whereas this project concentrates on making complex 3-D input more usable, a secondundergraduate project in Biomedical applications of SFF is exploring the output side of theproblem. Physical models are extremely useful in pre-surgery planning as well as the teaching ofanatomy and pathology, and SFF techniques have been used in this area with great success.Human bone replicas to date show only the exterior overall structure of bone, however, and noneof the minute' interior tissues and structures. This project involves using SFF to build cross-sectional models of fine-detailed interior structures of bone.Although this project is in the early stages of development, the eventual goal will be to replicatenot only the internal physical geometry, but also the non-homogenous mechanical properties ofbone. This will require the "borrowing" of techniques developed by a previous project in thearea of composites. Stereolithography patterns consisting of open cellular structures inside asurface shell are used as a host for filler materials; regions within a single object may beseparated by thin barriers, allowing filling with different matrix materials to create regions ofdiffering local properties. The internal structure can also be continually gradiated in thickness toproduce composites with properties ranging from that of the filler material to that of theStereolithography epoxy. Current fillers include epoxy matrices loaded with glass microspheres,as well as hydraulically-bonded ceramic mixtures with bulk properties matched to various bonestructures. The long-term goal of this project is to create a composite spinal cord model formechanical testing, such as automobile crash tests (Figure 4).Figure 4. Inset:inside spongy bone. model is ""'1'".«1"..,,,,,1",:>rlnon-homogeneous final product.233Space Shuttle Get Away Special PayloadThe objective of this project is to demonstrate some of the key technologies required for SolidFreeform Fabrication (SFF) and other automated manufacturing in a.microgravityenvironment. Because ofthe manufacturing flexibility offered>by Solid Freeform Fabrication,these techniques. have the potential to. be Qfenormous value to continued habitation of humans inspace; •••• ·SFF could eventually serve the International .space Station as an on-orbit system forproducil1gnew andrepl:;icement components, as well as tools. the .•. absence gravity, there isthe potential for rapidly creating extremely complex shapes, as supports are not required. Theabsellceofgravity also presents significant challenges associated with placing a liquid tobuildianobject,however. example, in depositing a bead of liquid into free space (i.e.without a substrate), interfacial tension will tend to cause the bead to break apart and ball upbefore it can solidify into a layer. Placing a liquid with a slow solidification rate in a planararrangement thus becomes a significant challenge.Two. students have prepared a preliminary design for a Get Away Special (GAS) payload to beflown on the Space Shuttle in September 1999 (Figure 5). This payload has been donated toMSOE by the Gammex Corporation through the Discovery WorId Museum of Milwaukee, WI.This set of GAS experiments will explore a number of the core scientific principles behind thedeposition, material flow, and solidification of fluids absent of a gravitationalTwo types of liquids will be deposited in test patterns that evaluate the relationship between theliquid and the surface onto which it is deposited. In one set of experiments, beads of a rapidlysolidifying thermoplastic (ABS) will be deposited onto a rigid substrate, into space, and ontopreviously deposited, unsupported beads. In another set of experiments using .the sameapparatus, a low viscosity photopolymer will be deposited onto a fiber mesh to create a planarFoam MoldingExperimentFluid DynamicsSyringes3-AxisSyringeComposite FomlinExperimentClose-FieldVideocamera Fluid DynamicsFigure 5. Preliminary design for SFF in Microgravity Get Away Special (GAS) payload.234sheet of liquid. This liquid will be cured by ultraviolet light after deposition.In a separate experimental apparatus, carbon-fiber composite tubes of varying diameter will beconstructed from prepreg material without any support structure. Two heated pinch rollers willfeed a prepreg strip past a guide roller, which will change the trajectory of the strip such that itfeeds back through the pinch rollers after circling through a set diameter. A composite tube withmultiple (3-5) layers will be produced during this experiment.The final experimental apparatus will create and mold a polymer foam. This apparatus consistsof a double syringe: Part A is polymeric diphienylmethane diisocyanate and part B is a polyethertype of a polypropolene glycol mixture. Parts A and B will be mixed mechanically at the end ofthe syringe and expand into a mold where the foam will set.Benefits of SFF Research in Engineering EducationWhereas textbooks have traditionally defined the boundaries between engineering principles,modern engineering education requires packages that integrate diverse concepts "containers"providing the resources for student-initiated, project-based learning. These containers must beconstructed around a topic that captures the imagination of students and encourages them to viewtechnology in a holistic perspective. They must enable mentor relationships between educatorsand students, whereby the learning process is a non-linear, joint exploration that includescollaboration with colleagues and industry. Few technologies offer a scope of applications asbroad as Solid Freeform Fabrication. Because of this, SFF is a topic that can become the idealtool for modern engineering education; an education container built around SFF can provide thefoundation for an entirely new engineering education paradigm.ACKNOWLEDGEMENTSThe authors would like to acknowledge the work of the following undergraduate students, who,under mentorship from faculty advisors, performed all of the research presented in this paper:REU STUDENTSSteven GerritsmaRebecca ZickSarah VickmanKevin TetzJames CaninoKristin PowellADVISORSDr. Robert CrockettVito GervasiDr. Lisa MilkowskiProf. Mike McGeenBrian StemperAnn BloorWe also gratefully acknowledge the financial support of the National Science Foundation and theMSOE Rapid Prototyping Consortium, as well as the facilities and expertise provided by thestaff of the MSQE ·Rapid Prototyping Center. The Shuttle experiment was made •possible bysupport from the Discovery World of Milwaukee, WI, the Gammex Corporation, the WisconsinSpace Grant Consortium, and Danfoss Fluid Power, Inc.235

Solid Freeform Fabrication Research In Engineering Education

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Solid Freeform Fabrication Research In Engineering Education

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