Thread: Fabrication
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Unread 02-04-2012, 15:07
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Re: Fabrication

Quote:
Originally Posted by FenixPheonix View Post
Team 751 does all our own manufacturing for one simple reason: we don't have the resources.

Let me explain. Our team has, in terms of manufacturing, a manual mill, lathe, drill press, four hand drills, a drop band saw, a vertical bad saw, a sander, a grinder, and a TIG welder that we got half-way through this season. We have a small team of fifteen students, and a highly devoted core of less than eight. As such, we have to balance both man-hours and machine hours. For every day-long mill job we set up, we sacrifice another, and lose design time for some area of the robot. And that is precisely why we, the students on the team, choose not to outsource our work. We've found that the lesson in practicality and trade-offs is more valuable than the functionality that we would gain from outsourcing. If a person on our team has a great idea that would need three days of manufacturing time, we all sit down, and run cost-benefits analysis on it. Is one day of mill-time and a student day worth half a pound of cheese-holing? We run into this one a lot. Most of the time, we say it isn't. But before SVR, we realized that, for one part, it was, because that half pound let us change out our corner wheels from Plaction for Performance, letting us solve the wheel breakage issues from Sacramento (cracked one in half and dented three to the point of being unusable crossing the bump.) So we spent the time, and ended up below the weight limit.

And it's precisely because of our in-house work that we CAD everything. We design all our parts, do time estimates, and schedule our machine time, going for maximum efficiency. We've got folders of part layouts that students just churn out, organized by sub-system and machine utilization. Our drivetrain was fabricated (not assembled, Andy-Mark shipping held us back) in three days, and everything else took us about nine. Everything was CAD'd, everything was prototyped. When you know how to run design well, you can streamline manufacturing. CAD is vital for optimizing machine schedules and ensuring that we can make everything, and producing accurate drawings our designs (very few of which are made by the person who designs them. That's usually for the few that we decide need the machining time the most for optimization, as we want the person who understands the design intent and manufacturing process, having designed both.)

We're looking into expanding our manufacturing abilities with another manual mill, and possibly a CNC. We are also hoping to get access to a local waterjet (at the TechShop. We've also done a bit of laser cuttig there.) This will eliminate some of the urgency of the scheduling (though I have no doubt that our designs will become more complicated to saturate our machines again.) However, we will continue to design and build all of our own parts, as we find it promotes a culture of responsibility and efficiency.

My point here is: we build in-house to teach our members about time and resource management, at the cost of some machine functionality. Is it worth it? Depends on what you want to get from it.
Right. I'm not against in house fabrication at all, I think it's great to know the process and be able to make good time estimates. If people can do it properly, let them. I love being able to use our team's CNC mill, and being able to mill manually is very useful. As a freshman and Sophomore, I loved being able to make parts and place them on the robot, as I got proud that my own part that I created was being placed on the final machine.

The point of this thread was to point out that designing is needed before fabrication, and everyone here seems to agree that detailed drawings or CADs are the way to go before any fabrication. My team likes to jump into fabrication, so a lot of times we end up finding solutions while we are creating parts. It's terrible. Parts cut too short are somehow placed somewhere else, parts too long are cut, and then found out they are not needed, and the result is an entire robot that is one swift kick away from being destroyed. In 2010, we used a lot of 80/20, but we didn't do CADs or detailed drawings. By the end of CMP, which was our second event that year, our Frame was offset by more than 30 degress because of the irregular placement of parts and the use of subpar parts because of a lack of design.
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