Mechanisms and Fabrication Part II ME2110 Spring 2019 Kyle Saleeby

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1 Mechanisms and Fabrication Part II ME2110 Spring 2019 Kyle Saleeby

2 Mechanisms and Fabrication Part II Kyle Saleeby With much appreciation to Dr. Chris Saldana and Dr. Tom Kurfess ME2110 Spring 2019

3 Lesson Objectives v Understand design considerations and tradeoffs for advanced fabrication techniques with including CNC machines, laser cutters, and 3D printers v Understand good practices for robust, consistent, and quality prototype robot designs v Exposure to resources for mechanisms and fabrication methods 3/ 63

4 Individual Competition v Triggering -> One action No additional energy Clean, repeatable v Things that get you DQ d.. Damage to the track (Scratches, WD-40, etc ) Not triggering Projectiles (including unintentional rubber bands) 4/ 63

5 Standard of Quality v Devices in the Trash Can Dumpster outside v Devices in the scrap bin Break down components Take out screws and nails v Begin early 5/ 63

6 Standard of Quality v Hot Glue Gun Don t leave plugged in v Shop Rules Clean up after yourselves 6/ 63

Saws, Wood, and Metal v Wood blades vs. Metal blades Teeth per inch Desired quality of cut WOOD METAL https://www.google.

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7 Saws, Wood, and Metal v Wood blades vs. Metal blades Teeth per inch Desired quality of cut WOOD METAL 7/ 63

How to cut wood 1. Mark your cut Pencil or Sharpie Carpenter s pencil 2. Mount your stock Clamps or vice Workbench in Idea Lab 3. Starting the cut Small, slow cuts 4.

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8 How to cut wood 1. Mark your cut Pencil or Sharpie Carpenter s pencil 2. Mount your stock Clamps or vice Workbench in Idea Lab 3. Starting the cut Small, slow cuts 4. Finishing the cut Push, not pull Near handle / guard of saw (not tip) / 63

9 Laser Cutting Benefits Drawbacks Very Small Kerf Non-Contact Cutting Precise, Repeatable Relatively cheap Relatively thin materials 2D Constrained design Limited materials (non-chlorine) / 63

10 Laser Cutting Focused beam heats material Gas-Assisted OR Gas blows away melted material Material is burned or vaporized Image [2] / 63

11 Types of Cuts Raster Vector Cut Vector Engrave / 63

12 Types of Cuts Raster Vector Cut Vector Engrave / 63

13 Power Density Power of a laser matters far less than power density!"#$% &$'()*+ =!"#$% -."* /%$0 [W/m2 ] 6mm Spot Diameter 503!"#$% &$'()*+ = : ; >3/: ; 0.6mm Spot Diameter 503!"#$% &$'()*+ = @ : ; 44. 2A3/: ; 100X Higher Power Density! / 63

14 Power Density for Common Materials Cutting thin plastic ( mm) Process Power Density (W/mm 2 ) Process Rate mm/min Hard Wood Engraving mm/min (1.5-3mm deep) Tissue Removal N/A Cautery 5-10 N/A / 63

15 Design for Laser Cutting Considerations Disadvantages 3D -> 2D Components Carefully plan joints, shear load Kerf of Laser Consider Aesthetics: Illumination, Light, Opacity Design for Assembly Difficult to hide fasteners Shear, Brittle Fracture (Acrylic) / 63

16 Fastening with Acrylic T-Nuts Attachment Only Nut width = thickness of acrylic Finger Joints Load Bearing (somewhat) Joint width = thickness of acrylic Image / 63 [3]

17 Fastening with Acrylic Recommend combination of T-Nut with finger joints. Add epoxy for permanent joints. / Image 63

18 Laser Ablation UV Laser, lower wavelength Minimum spot diameter limited by wavelength of light Allows for higher power density with extremely small spot size / 63

19 CNC MACHINING INTRODUCTION 19/ 63

20 Ideal Lab CNC Machine EMCO E350 3-Axis Mill Siemens 828D Controller 20/ 63

21 CNC Manufacturing v Computer Numeric Control of machine tools v Typically refers to CNC Machining (cutting) v Also, involved in many many other things Grinding Welding and fastening Pick and place machines (electronics assembly) Injection molding Thermoforming 21/ 63

22 Machine Tools v 5 basic tools Flat endmill Ball endmill Center drill Drill Edge-finder v Other tools Fly cutter (shell mill) Chamfer tool Reamer Single point tap Automatic Tool Changer (ATC) on Emco E350 Mill Left: Fly cutter / shell mill Right: Insert Endmill 22/ 63

23 Controlling a CNC Machine v External CAD + CAM software Geometrical based design Voxel based design v Internal control software Feature based 23/ 63

24 ShopMill Internal control software v Impressive 3-axis capabilities v Intro to machining concepts without Gcode v Easy to create, edit, and simulate most CNC operations v Leads to full CAM training with Fusion / 63

25 Fusion 360 External CAD + CAM software 25/ 63

26 ROBOT DESIGN DO S AND DON T 26/ 63

27 Wire Management v [Do] Wire Management Cables and wires Strings What can catch wires? Zip tie ends Lose duct tape Bolts and screws 27/ 63

28 Wire Management 1. Wire harness 2. Spiral cover 3. (Cleanly cut) Zip ties Balance successful functionality with clean design 4. Duct tape 5. Twisties 28/ 63

29 MyRio Indication Feedback v [Do] Realtime Feedback from MyRio v Basic LED Feedback Built-In LED status / state indicators On / off combinations Flashing protocol v Advanced LED Feedback External LEDs connected to MyRio (add resistors!) External LED / LCD screen (digikey, adafruit, sparkfun) 29/ 63

30 Selectable Functionality v [Don t] Live programming of MyRio Modifying code each round Re-uploading code for different home zone Drop your computer in the competition 30/ 63

Selectable Functionality v Modular and movable design Pegged limit switch v DIP Switches Digikey, Amazon v SPST (Toggle) Switch) Easier to mount and solder Cheap, robust v Push button with LED

31 Selectable Functionality v Modular and movable design Pegged limit switch v DIP Switches Digikey, Amazon v SPST (Toggle) Switch) Easier to mount and solder Cheap, robust v Push button with LED feedback Mechatronics kit 31/ 63

32 Auxiliary Sensors v [Do] Checkout other sensors! v Light-sensitive diode v Ultrasonic range finder v Potentiometer, encoder / 63

33 Lesson Objectives v Understand design considerations and tradeoffs for advanced fabrication techniques with including CNC machines, laser cutters, and 3D printers v Understand good practices for robust, consistent, and quality prototype robot designs v Exposure to resources for mechanisms and fabrication methods 33/ 63

34 References v Advanced Measurement and Instrumentation v Autodesk Fusion 360 Intro to CNC 34/ 63

Mechanical Design. Mark Jennings and Meera Wakim

Mechanical Design. Mark Jennings and Meera Wakim Mechanical Design Mark Jennings and Meera Wakim Download, install, and log in to the UT Virtual desktop (for engineering students): http://www.engr.utexas.edu/itg/facilities/virtualdesktop Mark Jennings