CAD
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Transcript of CAD
CADHans JohnsonBuild/Design CaptainFRC 3018 Nordic Storm2013 Lake Superior Excellence in Engineering Award2013 10,000 Lakes Engineering Inspiration Award2013 Championship Xerox Creativity Award
Why do we use CAD? Model robot
Concepts Testing Iterations Modifications between tournaments
Make drawings Sponsor machining
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
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
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
Simulation FEA Size Motion
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
Size Does the robot fit within size limitations Frame perimeter easy to measure Our articulating robot fitting within cylinder
Motion Simulate motion of mechanisms Do parts collide? Cam system on this year’s robot when folded
Are there collisions?
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
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
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