Term Project Final Presentation ? Visual aids available on-campus – Computer projection – Document camera – Camera ? Visual aids available off-campus – Camera – OR -- Send me your slides electronically and I’ll project them from my laptop 16.881 MIT Term Project Grading ? Term project is 30% of course grade ? Written report is 75% of term project – Due on last Lecture day. – 10% penalty per day late ? Final presentation is 25% of term project 16.881 MIT Term Project Final Presentation Schedule ? Tom Hoag, “Designing a Robust Business” ? Chip Clampitt, “The Use of Orthogonal Arrays to Optimize Nonlinear Functions Iteratively” ? Karl Hauenstein, “Robust Design of a Voltage Controlled Oscillator” ? Boran, Goran, Pepin, Shashlo, Wickenheiser, “Robust System Design Application / Integration - Ford Motor Company” ? Joe Distefano, “Application of Robust Design Techniques to a Paper Winding Simulation” ? Garth Grover, “HPT Dovetail 2-D Form Robust Design” ? Shelley Hayes, “Taguchi Method Meets Publish and Subscribe” 16.881 MIT Term Project Final Presentation Schedule, Cont. ? Wei Zhao, “Taguchi and Beyond - Methodologies for Experimental Designs” ? J. Philip Perschbacher, “Robust Design of Blade Attachment Device” ? Michelle Martuccio, “Allied Signal's Six Sigma Initiative: A Robust Design Case Study” ? Steve Sides, Bob Slack, “Coating Technology for Jet Aircraft Engines” ? Ebad Jahangir, “Robust Design and its Relationship with Axiomatic Design”. ? Tom Courtney “Robust Thermal Inkjet Printhead Design” ? David Markham, “Robustness Testing of a Film-Scanner Magnetic Module” 16.881 MIT Robust Conceptual Design Considering Variation Early in the Design Process 16.881 MIT Outline ? Motivation ? Tools and tricks -- TRIZ, etc. ? A framework -- RCDM & wafer handling case ? Case study -- VMA prehensor ? Case study -- Adhesive application in LBPs 16.881 MIT Quality in Product Development Quality efforts used to be focussed here determined here! Concept Development System Design Detail Design Testing and Refinement Production Ramp-up But 80% of quality is Customer use Taguchi Methods of parameter design Induce noise 16.881 Source: Ulrich and Eppinger, “Product Design and Development” MIT Concept Design: The Window of Opportunity Quality determined & costs committed Design flexibility Window of opportunity 100 Percentage of total Problem 75 50 25 Manufacture Use definiti on Concept Detail design design Source: Russell B. Ford and Philip Barkan16.881 Lifecycle phase Concept versus Parameter Design Concept Design ? Begins with broad specs ? Free wheeling, intuitive ? One off experiments ? Rough analysis ? Requires insight Parameter Design ? Begins with system design ? Bounded, systematic ? Orthogonal arrays ? Precise analysis ? Can be implemented as a “black box” Source: Russell B. Ford and Philip Barkan 16.881 MIT Biggest Roadblocks in Concept Design ? Poor problem formulation ? Stopping with too few alternatives ? Failure to search existing solutions ? Missing entire categories of solutions ? Inability to merge solutions 16.881 Source: Ulrich and Eppinger, “Product Design and Development” MIT Properties of a Good Problem Statement ? Solution neutral ? Quantitative ?Clear ? Concise ? Complete 16.881 MIT Techniques for Concept Generation ? Brainstorming ? Analogy ? Seek related and unrelated stimuli ? Use appropriate media to convey & explore – Sketching / Foam / Lego ? Circulate concepts & create galleries ? Systematically classify & search 16.881 Source: Ulrich and Eppinger, “Product Design and Development” MIT Theory of Inventive Problem Solving (TRIZ) ? Genrich Altshuller – Sought to identify patterns in the patent literature (1946) – "Creativity as an Exact Science" translated in 1988. ? The basic concept – Define problems as contradictions – Compare them to solutions of a similar form – Provide a large database of physical phenomena – Anticipate trends in technical evolution 16.881 MIT TRIZ Software ? Ideation International (http://www.ideationtriz.com/) ? Invention Machine (http://www.invention- machine.com/) – Effects –Principles –Prediction 16.881 MIT Tricks for Robust Concept Design ? Create lots of concepts with noise in mind ? Build breadboards & experiment (quickly) ? Don’t be afraid to revisit concept design stage ? Eliminate dependence on non-robust physical effects & technologies ? Design in non-linearities to exploit in parameter design 16.881 MIT Robust Concept Design Methodology ? Russell B. Ford and Philip Barkan at Stanford ? Four Stages – Definition of the robustness problem – Derivation of guiding principles – New concept synthesis – Concept evaluation and selection 16.881 MIT Wafer Handling Robot Rotating platform Gear pair Silicon Wafer Double Parallelogram Linkage Top View Process A Process B Process C Load Store 16.881 Side View MIT Stage 1 Definition of the Robustness Problem ? Identify robustness as a primary goal ? Incorporate critical performance metrics into the problem definition ? Target needed improvements in robustness ? Quantify key robustness goals T R = y 6σ y 16.881 MIT Stage 1 Rotating platform Silicon Wafer Gear pair Double Parallelogram Linkage How will you Top View specify robustness? Side View MIT16.881 Stage 2 Derivation of Guiding Principles ? Identify dominant error propagation mechanisms ? Derive insight into the root causes of performance variation ? Predict the effect of design parameters and error sources on performance variation ? Single out limiting constraints ? Substantiate the predicted behavior 16.881 MIT Stage 2 Rotating platform Gear pair Silicon Wafer Double Parallelogram Linkage Top View Side View 16.881 What are the root causes? What are the mechanisms of propagation? How would you predict effects? What are the constraints on the design? MIT Stage 3 New Concept Synthesis ? Modify error propagation mechanisms to reduce or eliminate transmission ? Eliminate or reduce error sources ? Circumvent limiting constraints ? Draw upon new technology ? Add extra degrees of freedom as necessary 16.881 MIT Stage 3 Rotating platform Gear pair Silicon Wafer Double Parallelogram Linkage Top View 16.881 How can you modify propagation? Can you circumvent constraints? Are there new technologies to employ? Develop 3 other concepts. Side View MIT Stage 4 Concept Evaluation and Selection ? Reconcile robustness requirements with al other critical performance specifications ? Select the best concept from all alternatives ? Predict the effect of design parameters and error sources on performance variation ? Decide whether further improvement is required 16.881 MIT References -- Conceptual Robustness ? Ford, Russell B., and Philip Barkan “Beyond Parameter Design -- A Methodology Addressing Product Robustness at the Concept Formation Stage”, DE-Vol. 81, Design for Manufacturability, ASME, 1995. ? Andersson, Peder, “A Semi-Analytic Approach to Robust Design in the Conceptual Design Phase”, Research in Engineering Design, Research in Engineering Design, vol. 8, pp. 229-239. ? Stoll, Henry W., “Strategies for Robust Product Design,” Journal of Applied Manufacturing Systems, Winter, 1994, pp. 3-8. 16.881 MIT Case Study VMA Prehensor ? Dan Frey and Larry Carlson ? The authors wish to thank the NCMRR (grant no. 1-RO1-HD30101-01) for its financial support ? The contributions of Bob Radocy as both design consultant and field evaluator are gratefully acknowledged 16.881 MIT Body Powered Prosthetic Prehension ? Amputee wears a harness to which a cable is attached ? Cable routed through a housing, down the arm, to a prehensor ? Body motions create cable excursion & apply force 16.881 MIT The TRS Grip ? A “voluntary closing” prehensor – Lightly spring loaded to open position – User applies cable force ? Often users want to change body position Cable tension while grasping objects ? How will variations in cable excursion affect grip force? 16.881 MIT Testing Apparatus ? Lead screw applies force / displacement ? Load cell measures applied tension ? LVTD measures applied displacement ? Resulting grip force measured MIT Testing the Grip Grip Force (lbs) Grip Force (lbs) Cable Tension (lbs) Amputees can generate 2” of excursion and 40 lbs tension How would you design the Grip? What form will the plots take? What determines robustness Cable Excursion (inches) to body motions? 16.881 MIT Pre-existing Approaches APRL Hook Northwestern U. “Synergetic Prehensor” 16.881 Allows the user to lock the prehensor - First stroke applies force and locks - Second, harder stoke unlocks - Safety compromised! - Poor reliability Myo-electrically operated hand -Sizing and gripping are distinct phases of grasp - Both require minimal mechanical energy - Longer battery life MIT Variable Mechanical Advantage ? Idea -- break up the task into sizing and gripping ? How can one use this to improve Cable Tension (lbs) robustness to body position error? Grip Force (lbs) Grip Force (lbs) 16.881 Cable Excursion (inches) MIT VMA Design Concepts Gear Based Design Linkage Based Design (Carlson) (Frey / Carlson) Simplified Linkage Based Design (Frey / Carlson) 16.881 MIT Operation of the VMA Prehensor MIT16.881 ? Over-running clutch used to hold force ? Performance very sensitive to shape of rollers ? Flat spots due to wear rendered design unreliable MIT Holding Assist Concept 0 5 10 15 20 25 GRIP FORCE (lbs.) 0 10 20 30 40 CABLE TENSION (lbs.) Carlson’s Design 16.881 VMA Prehensor First Prototype ? 2D profile allowed quick CNC prototyping ? $200 in machining costs ? Aluminum components ? Stock bearings ? ~$100 materials VMA prototype with face plate removed MIT16.881 Robustness to Error in Excursion ? Excursion saved in sizing ? Employed later to lower sensitivity to excursion by more than a factor of three 25 20 15 10 5 0 Grip Force at Figertip (lbs) 0 0.5 1 1.5 2 Input Cable Excursion (in) 16.881 VMA Prototype TRS GRIP II MIT MIT16.881 Robustness to Environment ? Users subject prehensors to varying conditions ? Such conditions adversely affected performance VMA I PERFORMANCE UNDER VARYING ENVIRONMENTAL CONDITIONS 0 5 10 15 20 25 0 5 10 15 20 25 30 35 40 45 INPUT CABLE TENSION (lbs) G R IP F O R C E (l b s ) CLEAN SOAPY WET DRY DEGREASED Series6 Ratchet Teeth ? Broached fine teeth into mating surfaces ? Friction no longer determines performance 16.881 MIT VMA Prehensor Second Generation Prototype ? More agressive increase in mechanical advantage ? Holding assist enhanced through mechanism design 16.881 MIT VMA II PREHENSOR COMPARED TO VMA I & GRIP II 25 20 15 10 5 0 0 10 20 30 40 INPUT CABLE TENSION (lbs) GRIP FORCE AT FINGER TIP (lbs) VMA II VMA I GRIP II 16.881 MIT Results of Amputee Evaluation VMA Prehensor ? Provides greater range of motion while maintaining grasp ? Works reliably under wide range of environmental conditions ? Shifts prematurely with compliant objects ? “Free-wheel” switch convenient to use – Provides alternate mode of operation 16.881 MIT References -- VMA Prehensor ? Frey, D. D. and L. E. Carlson, 1994, "A body powered prehensor with variable mechanical advantage," Prosthetics and Orthotics International, vol. 18, pp. 118-123. ? Carlson, L. E. and R. Heim (1989). "Holding assist for a voluntary-closing prosthetic prehensor," Issues in the Modeling and Control of Biomechanical Systems, American Society of Mechanical Engineers, DSC-Vol. 17:79-87. ? Childress, D. S., and E. C. Grahn (1985). "Development of a powered prehensor". In 38th Annual Conference on Engineering in Medicine and Biology, p. 50. ? Taylor, C.L. (1954). "The biomechanics of the normal and of the amputated upper extremity," Human Limbs and Their Substitutes, McGraw Hill, New York, pp. 169-221. 16.881 MIT Case Study Adhesive Application for Surface Mount of Large Body Packages ? Dan Frey and Stan Taketani ? The authors wish to thank the Hughes Doctoral Fellowship program for its financial support. 16.881 MIT Adhesive Application Design Issues ? Adhesives are required to: – Support mechanical loads – Transfer heat to sink ? Robustness problems Typical adhesive pattern – Epoxy thickens during application – Air sometimes “burps” – Air gap height not repeatible –LBPs 16.881 MIT P-Diagram Noise Factors Product / Process Response Signal Factor Control Factors 16.881 MIT Compression of a Single, Long Bead F/L (lbs/in) Navier-Stokes highly viscous x y h(t) W(t) dh/dt MCM Body Adhesive Bead u(x,t,y) h (,, ? h 3 dp ∫ uxt h) = 12μ ? dx 0 conserve mass PWA Upper Surface F = ?μ ? dh ?W 3 L h 3 dt Pressure (psi) x integrate ?15 ? 5FL 1 ? / ht / () = ? ? μ o 3 o 3 t + h o 5 ? ? Wh 16.881 MIT Multiple Beads with Air Pockets F/L x 1 x 2 x n p 1 p 2 p n h W gauge pressure onder MCM (atm) Pressure Profile During Rampup 0.15 0.1 0.05 0 1 0.8 0.6 0.4 0.2 0 0.2 0.4 0.6 0.8 1 x (inches) 16.881 MIT Eliminating “Squeeze-Out” Despite Viscosity Variation ? When beads touch one another, downward motion is arrested d dt touching 1 h = 2 d h n P P d t nottouching x not touching touching ? Design rules exploit this phenomena 4 margin>bead pitch ∫ Ft = ?3πμ ? ? W ? ? W ? d 2h f 2 ? ? 2 ? ? ? ? 1 ? W + margin? ? 16.881 MIT Estimating Percent Coverage ?h sparse coverage = h h h +?h sparse dense sparse coverage coverage coverage ? Thinnest air gaps set component height ? Wider air gaps are areas of sparse coverage 16.881 MIT Adhesive Flow Model Preliminary Verification ? Used dispense test data to estimate μ ?Used μ, P, and V to calculate bead shape ? Used force schedule to estimate final height and percent coverage 16.881 MIT Postage Stamp and Tape ? Postage stamp protects the circuitry ? Tape allows easier rework ? BUT -- MCM to PWA gap cut from 13 mils to 7.5 mils ?Fα1/h 3 -- over 400%more force req’d Force MCM Body Leads Leads PWA Adhesive Bead Pads Tape Pads Postage Stamp 16.881 MIT Accomodating Equipment Limitations ? Robot can only apply 7 lbs seating force ? Air pockets support substantial load (>50%) – Open air gaps (when practicable) ? F ∝ 1 - Switch to thinner beads W 3 16.881 MIT Gaps in Adhesive Coverage ? Model predicted existence of gaps in coverage under certain conditions ? Experimentally observed later ? Given gap location, they might not have been detected early enough 16.881 MIT Dispense Problems Due to PWA Waviness Nozzle too close to PWA -- Nozzle too far above PWA -- flow partially blocked. Just right. bead breaking and dragging. 16.881 MIT Dispense Parameter Selection Force h Force Plugging Dragging Gapping A < A max ( F max , μ, airgap) Dragging 2 A h < ??h D nozzle Plugging h > ?h + D nozzle 2 Gapping A (1 ? cosα) sin 2 1 ? α A 2 > airgap +?h 16.881 MIT Next Steps ? Next off-campus session ? Course evaluations ? Term project presentations ? Good luck! 16.881 MIT