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Unread 28-01-2014, 17:17
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Paul Copioli Paul Copioli is offline
President, VEX Robotics, Inc.
FRC #3310 (Black Hawk Robotics)
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Re: VEXPro 2014 Product Initial Impressions

Quote:
Originally Posted by magnets View Post
Oops, I meant to add that I wasn't upset because none of the other suppliers really have them. I'm not looking for roundness on the bearing holes as they tend to be quite round, but my problem with the dog gear was the diameter was a touch bigger than I would have made it.

Knowing if stuff is really concentric can really help with design to locate features. For instance, the versa pattern thing on vex parts is very accurately concentric, but for instance, some of the recesses for fastener heads in the gearboxes for mounting aren't quite concentric with the mounting hole. In normal use, it doesn't really matter, but if you're using the plates/gearbox your own application, it's nice to know.

I wouldn't mind seeing stuff like circular runout on hubs and stuff. Whenever our kids draw a part in CAD, I have them do all the GD&T dimensions. We've got a great machinist who won't work with kids and drawings who don't have a good understanding of GD&T. As a result, we end up with a bunch of high school kids who really understand dimensioning parts and tolerances for machining and who understand how poor the field drawing FIRST supplies are.
We agree on this: Good GD & T is essential to make parts that function properly and as required. All of our manufacturing drawings have fully dimensioned drawings with GD & T per ISO standards. Our customer interface drawings will never have them. Why? We believe that is proprietary information. We believe that prescribing total runout (because concentricity in the GD&T world has nothing to do with rotating a surface around an axis) for a hexagonal hole is one of the most complicated things to get right.

So, in general, for VEXpro items, things that are supposed to be locating features (versakey system, bearing bores) will be true and things that are fastening (screw counterbores) will be at the maximum allowable tolerance for the fastener to fit.
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In full disclosure I am the President of VEX Robotics, a division of Innovation First International.
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