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CAD

CAD. Hans Johnson Build/Design Captain FRC 3018 Nordic Storm 2013 Lake Superior Excellence in Engineering Award 2013 10,000 Lakes Engineering Inspiration Award 2013 Championship Xerox Creativity Award. Why do we use CAD?. Model robot Concepts Testing Iterations

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CAD

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  1. CAD Hans Johnson Build/Design Captain FRC 3018 Nordic Storm 2013 Lake Superior Excellence in Engineering Award 2013 10,000 Lakes Engineering Inspiration Award 2013 Championship Xerox Creativity Award

  2. Why do we use CAD? • Model robot • Concepts • Testing • Iterations • Modifications between tournaments • Make drawings • Sponsor machining

  3. Organization • Nordic Storm’s 2013 Robot had over 100 parts and sub-assemblies • Each subsystem was assigned a prefix • A = Actuation • C = Climber • D = Drivetrain • DMP = Dumper • P = Positive Engagement • R = Full robot assembly • Followed by name of part, e.g. C_ClimberPivotPlateLeft • Each subsystem had an assembly, combined into full robot assembly

  4. Dropbox • Nordic Storm uses dropbox to sync and back up our CAD files • Offers 30 day version control • Free • 2GB of space, invite other members to get more space • Allows everyone to work from one set of files, rather than moving them around on a flash drive

  5. Our Process • Drivetrain CADed within the first couple days • Manipulator/superstructure designs in parallel with prototyping of mechanisms • Once full robot model is largely complete, parts that will be manufactured by sponsors are sent off • For parts made in house, drawings are made and reviewed by a mentor before being printed and given to student machinist. • As parts are assembled, tested, and the design is modified, the CAD model is updated nightly

  6. Simulation • FEA • Size • Motion

  7. FEA • Finite Element Analysis • Used to determine stresses on parts • Will a part hold up under expected load? • Change material (AL vs Steel) • Increase thickness • Shows points of high stress

  8. Size • Does the robot fit within size limitations • Frame perimeter easy to measure • Our articulating robot fitting within cylinder

  9. Motion • Simulate motion of mechanisms • Do parts collide? • Cam system on this year’s robot when folded • Are there collisions?

  10. Gotchas/Tips and Tricks • Design some tolerance into your parts • Holes on laser cutting/waterjet should be cut small and drilled/reamed to size • Nesting parts – blocks into tubing • Clearances between moving mechanisms • Things get bent, make sure it won’t break something else if it does • Things won’t be perfect, make sure your design can handle that • Electronics boards • Make sure they aren’t an afterthought and there is enough space for everything • Make sure they are accessible • Battery • It’s big and heavy, use it to your advantage and include it in your design • Inventor has a CoG calculator. Use it! • Many COTS parts have CAD models available that can be imported • AM • McMaster • 3D Content Central

  11. Frame Generator • Inventor has a built-in frame generator • Provide a skeleton, and Inventor will create the proper lengths of tubing, pipe, extrusion, bar stock, etc

  12. Drawings • Drawings are made for all parts machined in house or sent to sponsors with material • Part files sent for laser and CNC • After part is created and design is reviewed by multiple students and mentors, a drawing is created • Drawing is then checked to ensure it is complete before printing • Each drawing has a revision number in the title block to avoid confusion between multiple versions of the part – updated every time the drawing is printed

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