and former head ta c.j. adams mechanisms,...
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Mechanisms, Fabrication,and
Crash Course TipsZoe Klesmith & Ana Schauer
With much appreciation to Kyle Saleeby, Dr. Rich Simmons, Dr. Tom Kurfess, Dr. Chris Saldana,
and former Head TA C.J. Adams
Some content based upon material created by: Dr. Andrew Semidey & contributions from Alexis Noel and Hannes Daepp
ME2110 | Spring 2020
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This Lecture
2
Crash Course:1) a rapid and intense course of study
2) an experience that resembles such a course--Merriam-Webster Dictionary
Not comprehensiveInspire and engage
Reference slides
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Announcements
1. Announcements on homepage of website
2. FAQ Page http://2110.me.gatech.edu/QnAs
3. Next week: Studio Design Discussion
3
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Design Process – How to utilize CAD during conceptual design and prototyping
Discuss material selection for ME2110 machinesJoining and fastening methods
Provide fabrication tips with available toolsApply lessons learned & avoid common mistakes
Learning Objectives
4
1.
2.
3.
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Mechanical DesignIndividual project and final competition
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Successful Design
Terrible Ideas Great Ideas
Bad Construction
Good Construction Reliable Performance
High Scoring Potential
6Other critical dimensions: Execution, Timing, Communication & Reporting
win the competition
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Design Process
7https://www.google.com/search?q=design+process&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiQ99WJ05XgAhUrhOAKHd4CCVsQ_AUIDigB&biw=1660&bih=875#imgrc=I2Ez6g6_VE9LeM:
Design tools
Not CAD
Prototype & CAD, then test(order depends)
Competition document
Design discussion, interim reports
Iterative design
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Practical Design
❖ ME 2110 projects are time consuming – Ideas must work– Construction must be feasible with available tools– Construction needs to be well executed
❖ Choose tools to match your skill set – aim to make manufacturing efficient & error-free– Design for Manufacturing– Invention studio tools expand fabrication capability, and can
improve quality and efficiency
8
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CAD and Conceptual Design
9
❖ Locate and orient subsystems and parts❖ Enhanced visualization❖ Fast concept generation by combining existing
concepts❖ Documentation (version control)❖ File sharing for co-operation and communication❖ Detailed design can proceed from conceptual models❖ CAD models easily evaluated with engineering tools
(e.g. FEA)❖ Leads directly to rapid prototyping processes for
fabricating parts (Invention Studio)Adapted from: E. Bamberg, "Principles of Rapid Machine Design", 2000.
Why incorporate CAD in your design process?
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Risks and Drawbacks with CAD
10
❖ Biggest Drawback: Loss of hands-on experience❖ Need to make sure concepts are physically realizable❖ Limiting assumptions can stifle creativity❖ Cannot test unmodeled effects or validate assumptions❖ Physical tests can lead to lots of learning
You need to balance Physical Testing with the Design Process and CAD
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Other Sources of Standard Parts
12
Mechanism Inspiration:❖ 507 Mechanical Movements
http://507movements.com/
Other Sources of Standard Parts:❖ ServoCity
https://www.servocity.com/
❖ SDP/SIhttps://shop.sdp-si.com/catalog/
❖ MISUMI USAhttps://us.misumi-ec.com/– Application Library:
https://us.misumi-ec.com/us/ideanote/
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ROBOT DESIGNDO’S AND DON’T
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Wire Management❖ [Do] Wire Management
– Cables and wires– Strings
What can catch wires?– Zip tie ends– Loose duct tape– Bolts and screws– Any moving parts on your robot
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Wire Management Methods
1. Wire harness
2. Spiral cover
3. (Cleanly cut) Zip ties/Panduits
4. Duct tape
5. Twisties
6. Heat Shrink
15
Balance successful functionality with
clean design
https://www.amazon.com/Tesa-adhesive-wiring-original-ISOBAND/dp/B00XPDVER2/ref=sr_1_6?keywords=wire+harness+wrap&qid=1550078407&s=gateway&sr=8-6
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MyRio Indication Feedback
❖ [Do] Real-time Feedback from MyRio/Arduino
❖ Basic LED Feedback – Built-In LED status / state indicators– On / off combinations– Flashing protocol
❖ Advanced LED Feedback– External LEDs connected to MyRio/Arduino (add resistors!)– External LED / LCD screen (digikey, adafruit, sparkfun)
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Selectable Functionality
❖ [Don’t] Live programming of MyRio/Arduino– Modifying code each round– Re-uploading code for different home zone– Drop your computer in the competition
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Auxiliary Sensors
❖ [Do] Check out other sensors!
❖ Light-sensitive diode❖ Ultrasonic range finder❖ Potentiometer, encoder
18
https://www.google.com/search?q=light+sensitive+diode&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjpms75hrjgAhWBUt8KHfiQATcQ_AUIDygC&biw=1546&bih=824#imgrc=HWP-2Spom-BTMM:https://www.sparkfun.com/products/13959
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Fabrication Common Materials
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Common Materials – Wood
❖ Natural Wood– Hardwood vs Softwood– Stay away from softwoods, such as pine, as they
tend to warp – Hardwoods, like poplar or oak, are easy to work with
and more dimensionally stable than pine
❖ Manmade Wood Products– Manmade wood products are more dimensionally
stable then natural products– Avoid MDF (medium density fiberboard) as it does
not hold nails or screws well and is not as strong as other manmade materials
– Plywood is good for large flat members (such as a base)
▪ Stick to sanded plywood or birch plywood (best)▪ OSB is a rough material and hard to work with
Poplarhttp://www.boulterplywood.com/photogallery/wood%20names/poplar.jpg
Birch Plywoodhttp://tablerosferrandis.sharepoint.com/siteimages/birch.jpg
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Common Materials – Plastics
❖ PVC (Polyvinyl chloride)– Mainly for rods and pipes– Easy to work with– Readily available– Rigid or flexible
❖ HDPE (High-Density Polyethylene)– Mainly used for flat sheets– High strength to density ratio
❖ Plastics can be used as linear or rotational bearing surfaces– Plastics have low coefficient of friction against
most other materials– Avoid metal-on-metal or wood-on-wood moving
joints
PVChttp://www.jayplastindustries.com/product/hose-pipe.html
HDPEhttp://www.tapplastics.com/product/plastics/cut_to_size_plastic/hdpe_sheets/529
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Common Materials – Metal
❖ For products requiring a long lifetime❖ Stick to aluminum (5000-6000 series
if you buy online)❖ Sheet material can be cut to shape
on WaterjetAluminum rodshttp://www.alumaloy.org/
https://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.amazon.com%2F80-20-Inc-T-Slotted-Extrusion%2Fdp%2FB001F0F112&psig=AOvVaw0rHN3S__DKpmC6cx2UlUsb&ust=1581009686831000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCMip0s32uucCFQAAAAAdAAAAABAE
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80/20 Aluminum extrusionhttps://www.google.com/url?sa=i&url=https%3A%2F%2Fwww.servomagazine.com%2Fmagazine%2Farticle%2Fthe-armadeus-project&psig=AOvVaw1o_MXLNcs--OvJmnX69whJ&ust=1581009703355000&source=images&cd=vfe&ved=0CAIQjRxqFwoTCNjJt-n2uucCFQAAAAAdAAAAABAD
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Material Stewardship
❖ No Devices in the Trash Can– Dumpster outside
❖ Devices in the scrap bin– Break down components– Take out screws and nails
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FabricationJoining and Assembly
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Joining – Common Methods
❖ Nails– Shear Strength only– Easy and fast, but not very accurate
❖ Screws– Shear Strength and Tensile Strength– Needs pre-drilling– To draw 2 parts together, you can’t have threads bite
into both parts– Counter-sinking may be used to ensure a flat surface
❖ Nuts and Bolts – Good for metal or plastic joining– Must oversize the bolt hole to draw the parts together
❖ Rigid Joints require 2 fasteners– 1 fastener makes a pin joint
❖ Soldering– Don’t let electrical connections plague your builds!Youtube - Soldering Video
http://www.commonnail.com/commonnails/ironnails.html
http://www.norfolkhardware.com/
Nut, Bolt, and Washerhttps://www.britannica.com/technology/bolt-fastener
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Joining - Screws
❖ Drill pilot hole first❖ Fasten with screws
– Transfer punch / one at a time– Do not drill 4 pilot holes, then fasten with 4 screws– Difficult to precisely align
26https://www.popularwoodworking.com/wp-content/uploads/PWE150322_QAfull.jpg
Checkout popularwoodworking.com!
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Joining - Wood
❖ Combination of:– Wood Glue– Screws– Nails (rarely)
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Joining – Wood Glue
28https://www.thegeekpub.com/4314/glue-vs-screws-which-one-is-stronger/
Glue 2 withstood 590 lbs
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Joining – Wood Glue
❖ Wipe joint with cloth– Remove saw dust– Gorilla glue? Use damp cloth– Yellow glue? Use dry cloth (water weakens joint)
❖ Spread glue evenly over surface❖ Clamp together
– Some advise slightly moving the joint
❖ Wipe away excess glue
❖ (Optional) Drill pilot hole and fasten with screws while clamped
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Joining - Glue
What to join other materials besides wood to wood?
Check out the link below:http://www.thistothat.com/cgi-bin/glue.cgi?lang=en&this=Wood&that=Plastic
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Joint and Link Fabrication
❖ Pin Joints
❖ Link Fabrication– Lasercut (plastics) – Waterjet (wood/metal)
Links
Pin Joint
Exploded View
NutJam Nut
Washers
Bolt
Bushingor SleeveBearing
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Joining - Enforcing Constraints
Rotational Constrainers Translational Constrainers
Flange Bearinghttp://www.micromech.co.uk/dir_suppliers/spyraflo_gfx/flangemount.jpg
http://vipdictionary.com/img/SSHinge.jpg
Pillow Block Bearinghttp://www.vxb.com/ball-bearings-images/ucp.jpg
Turntable / Lazy Susanhttp://ecx.images-amazon.com/images/I/71TgDkqXx1L.jpg
Hinge
Drawer Sliderhttp://www.edirecthardware.com/img/products/643/643-3832_GRP1.jpg
Linear Bearinghttp://3.imimg.com/data3/YP/BT/MY-4165859367/linear-ball-bearing-2-500x500.jpg
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You wanted… You got…
Common Fabrication Mistakes
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UseCorner
Clamps… …andSquares
Common Fabrication Mistakes
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FabricationMachines and Resources
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Rapid Prototyping – Laser Cutter
36
How does it work?• Lasers• Accuracy of 20 microns• Can cut through 0.5” woodWhen to use laser cutter:• 2D cuts of wood, some plastics
Common materials NOT ALLOWED:• Polycarbonate (Lexan), PVC• Most rubbers
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Rapid Prototyping – Laser Cutter2D to 3D Wood Fabrication
37https://www.google.com/search?q=laser+cut+bendable+wood&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiQoJ2C08fdAhUmTt8KHd5kAjcQ_AUIDygC&biw=1118&bih=676#imgrc=p266zv8a8KMTGM:
https://www.google.com/search?biw=1118&bih=676&tbm=isch&sa=1&ei=14-iW6C5Kqqc_QaUkYbICw&q=laser+cut+wood+gears&oq=laser+cut+wood+gears&gs_l=img.3..0i24.27396.28362..28883...0.0..0.51.233.5......1....1..gws-wiz-img.......0j0i30.DO78RL64VG8#imgrc=zciSYmJToLucQM:
https://www.google.com/search?biw=1118&bih=676&tbm=isch&sa=1&ei=SJCiW7aKA427ggfigIf4DQ&q=laser+cut+wood+robot&oq=laser+cut+wood+robot&gs_l=img.3...2844.3755..3882...0.0..0.50.262.6......1....1..gws-wiz-img.......0j0i67j0i24.DDoMB7_on4c#imgrc=xlazkNF0oe8EXM:
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Laser Cutting
Benefits
Very Small Kerf“Non-Contact” CuttingPrecise, RepeatableRelatively cheap
Drawbacks
Relatively thin materials2D Constrained designMust carefully plan jointsLimited materials (non-Chlorine)
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Types of Cuts
Raster Vector Cut
Vector Engrave
Raster
Vector Cut
Vector Engrave
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Rapid Prototyping - 2D to 3D Design
Assembling 2D shapes into 3D geometries
40
Combination of hardware and finger jointsFasten with epoxy for extra strength
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Rapid Prototyping – Finger Joint
41https://en.wikipedia.org/wiki/Finger_joint#/media/File:Boxjoint.png
Finger joints are used for structure and rigidity
Load-bearing
• Generally, finger joint width is thickness of material• Wider is ok, application specific• Laser kerf and fitting tolerances:
https://alliance.seas.upenn.edu/~medesign/wiki/index.php/Guides/LaserCuttingFits
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Rapid Prototyping – Finger Joints
42
http://www.instructables.com/id/How-to-Build-your-Everything-Really-Really-Fast
http://3dbizcenter.com/category/how-does-3d-printing-work/
http://www.instructables.com/id/How-to-Build-your-Everything-Really-Really-Fasthttp://www.instructables.com/id/How-to-Build-your-Everything-Really-Really-Fast
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Rapid Prototyping – Fasteners
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• Match nut to thickness of material• Make sure washer size is sufficient• Wide-head bolts are better• Consider which tools are readily available to you
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Rapid Prototyping – Waterjet
44
How does it work?• 50,000 PSI with garnet• Accuracy of 80 microns• Can cut through 6 inches of steelWhen to use waterjet:• 2D cuts of most materials
• Wood, metal, plastic
When NOT to use waterjet:• Cutting soft woods, glass, foam
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Rapid Prototyping – 3D Printers
45
How does it work?• FDM, SLA, SLS, DLP• FDM accuracy 150 microns • Uses PLA (other materials available)When to use 3D printers:• Complex 3D geometries
When NOT to use 3D printers:• To make boxes• To make 2D shapes
For more general tips and guidelines, see:https://www.3dhubs.com/knowledge-base/3d-printing-stl-files-step-step-guide
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When to use the 3D printer
❖ Custom parts to interface with your mechatronics components
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Rapid Prototyping – Boxes
47
• Warped• Time-consuming• Inaccurate
measurements• Expensive
• Flat edges• Fast• Accurate
measurements• Cheap
3D Printing Laser Cutting
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Rapid Prototyping – Trade-offs
❖ ‘Build it now and tinker until it all fits together and works’ vs.‘Design (CAD) it now and let a machine make it for us’
❖ Trade-off involving Time and Effort:upfront design / CAD build and tinker
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CAD: ~15 hoursManufacture: ~3 hoursAssembly: ~15 minutes
Ex: Sanding End Effector Prototype
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Common Fabrication Mistakes
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❖ Building without a plan (‘cut and try’)– CAD first!
❖ Assembling skewed or slanted frames❖ Fasteners that must be tightened 'just right’❖ Using duct tape as a fastener❖ Not modifying mousetraps❖ Overuse of string
– String tangles and snags– Requires proper management to be used effectively
❖ Forgetting to regularly inspect and maintain your machine
❖ Motor/Actuator coupling and mounting– Hot glue is not a motor coupling
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Common Fabrication Mistakes
❖ Not considering the trade-offs: when does it become worth it to purchase a component rather than manufacture it in-house?
❖ Waiting until the last minute to use equipment - there can be a long queue for printers/laser cutting
❖ Not testing multiple times❖ Design fixation: don’t get stuck on a design just
because you’ve spent a lot of time on it already❖ Gears not meshing/inappropriate gear ratio
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Summary
❖ Use mechanisms to achieve capable designs– Use materials that are appropriate for desired properties (strength-weight
ratio, friction, etc.)– Constrain mechanisms to achieve reliable performance– Re-purpose household items to match functionality
❖ Select materials that are easy to work with– Low quality materials mostly produce low quality results
❖ Choose an efficient, straightforward primary manufacturing strategy that matches your experience & skills– Most foolproof manufacturing methods do not rely heavily on manual skills:
waterjet, laser-cutter, 3-D printer, CNC, etc.
❖ Plan & design your device layout & construction thoroughly– Design for Manufacture, Design for Assembly, Design for Disassembly– Secure & store all components in a well-defined device location– Use strain relief (secure wires) to avoid loose electronic connections– Remember that design is iterative: prototype and test thoroughly
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Appendix:Good Examples
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Good Examples: AXE (Fall 2019)
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Good Examples: AXE (Fall 2019)
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Good Examples: A Few Loose Screws (Spring 2016)
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Good Examples: Blue’s Clues (Spring 2015)
❖ Chelsea SilbergliedArmaan VeljiOpeyemi Olaleye
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• Constructed primarily from 2-D laser-cut plywood components• DFA/DFD: Slotted parts assemble/disassemble easily; reinforced with screws &
brackets as necessary• Result: Ability to minimize manufacturing effort - majority time spent in planning
& design (CAD), and testing• Performance: 4th round (within top 30/74)
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Good Examples: Top Gun (Spring 2015)
Chris Healy, Zach Archbold, Randy Long, & Sahas Singh 57
Sidewalls for secure storage, boxing, & aesthetics
Quality materials & assemblyGood usage of space & absence of hair triggers
Laser-cut precision components: storage shelf, side walls, & victim pusher
Clean decals for simple visual appeal
• Performance: 4th round (within top 30/74)
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Good Examples: The Shady Mammals (Summer 2015)
58
Hoang Dang, Andrew Hanna, & Reagan Wilkerson
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Good Examples: The Shady Mammals (Summer 2015)
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•Performance: 1st Place
Victim RetrievalLinkage
Rubble SweepingLinkage
Weight with Pulley System
Motor 1 (Wheel and
Axle)
Motor 2 (Spur
Gears)
Constraints (Pivots and Support)
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Good Examples: Ghost Squadron (Fall 2015)
William Neidecker-Gonzales, Hannah Orr, Abheer Bipin, & Darren Maguire
• LED display for aesthetic appeal• Waterjet use for metal components• CAD: Cardboard-Aided-Design
Example: Torpedo deployment arm1. Prototype in cardboard & test2. Trace/Modify in CAD package3. Manufacture (e.g., waterjet, lasercut)4. Assemble & run
Performance: 3rd Place
1/2
1/2
3/4
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Good Examples: WoodFellas (Fall 2015)
• Example of good planning & great carpentry skills
• Tools: table saw, drill press, waterjet, metal shop, general assembly
• Secure location for ALL components (use provided mounting holes if possible)
• Avoid fabricating necessary/important parts if they are hard to make and affordable elsewhere (e.g., some gears are cheap on Amazon)
• Design with construction in mind (DFA)• Use structural cuts (e.g., Dado cut)
• Performance: 2nd Place
Robert Lineberg, Nolan Hall, Jason Hunyar, & Shen Yoon
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Good Examples: Average Joes (Summer 2016)Reed Morris, Kyle Brantley, Nick Maniscalco, & Alex Ullrich
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Good Examples: Average Joes (Summer 2016)
• Laser cut parts provided:Precision Spare partsAbility to make mirrored subsystems
• Minimized snag/rough points for all string driven systems
• Used manual prototyping / rough builds to validate concepts, then created CAD models to produce final parts
• Performance: 1st Place and Best In Show 63
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Laptop
Arduino &Electronics
Mounting PlatformAmigoBot Base
Air Supply
Launcher & Reloading Mechanism
Camera
Non-ME 2110 Example: Ramblin’ Wrecking Bot
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Non-ME 2110 Example: Ramblin’ Wrecking Bot
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Mechanical Design & Construction
❖ Primarily laser-cut plywood and 3-D printed parts
❖ Launching Mechanism– Solenoid valve attached to PVC
pipe– Servo-actuated gimbal provides
2 DoF
❖ Reloading Mechanism– Servo-controlled barrel– Custom laser-cut plywood parts
with 3D-printed spacers/braces
❖ ME2110 Projects have different requirements – use resources wisely
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