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Unread 11-07-2018, 03:35 AM
chrisrin chrisrin is offline
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Past mechanism CAD libraries & early CNC prototyping

From looking at some teams' blogs and build season photo galleries, it seems some teams are able to CNC some very effective early prototypes to use for testing in a matter of days after kickoff.

It made me wonder about best practices. Teams often share their CADs nowadays, and it seems quite possible for a team to do the following:
- Build up a library of CADs of effective mechanisms from the past that interact with various kinds of game elements... sourced from many different high performing teams. Convert to files native to the team's preferred CAD application.
- Once the game is revealed, find (for example) a CAD from the library for an intake that performed very well with a similar game piece. This year, teams probably were looking at recycle rush intakes.
- Modify the CAD (maybe using a parametric approach) so scale/geometry of the mechanism design match the current game's game piece
- Send it to the CNC (perhaps cut out of plywood or plastic rather than metal), and start testing / iteratively refining

It seems like this kind of thing could be started by like day 2 & would be a nice jump start.

Do many teams out there on CD do this? For intakes of balls / cuboids, seems like a no-brainer. thanks.
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Unread 11-07-2018, 01:07 PM
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Chris Mounts Chris Mounts is offline
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Re: Past mechanism CAD libraries & early CNC prototyping

We have a library of past designs by several teams that we add to. This mostly saves us on conversion time from STEP to Inventor.

My few attempts at wholesale copying of mechanisms has not gone well. I have yet to see a model in FRC that can be built without inside knowledge or a lot of reverse engineering. The 6 week build schedule does not lend itself to perfect model creation and often details are figured out on the actual robot and never modeled.

Splitting out a specific mechanism is also complicated. Mechanisms tend to be tightly integrated into the overall design of the robot. Turning those into stand-alone parametric designs would be a large CAD effort.

Have you looked at the Greyt mechanisms? These are the closest I've seen to generic mechanisms. Hopefully he releases more next year and we start getting a library of designs to work with.Even if you don't use them on your actual robot the designs should speed up prototyping.
http://www.wcproducts.net/structure/greyt-mechanisms

Maybe some other teams have some common prototype geometry they reuse? We do not yet.
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