Fabrication

[MichaelBick]

There is really no reason not to CAD. I was our single CADder for our team this year, and I was able to CAD the whole robot before we started building. Again, we had an amazing machine shop, not ridiculous turnarounds, but quicker than we could have done it in. If I had to do it again though, I would recommend CADding a full drive system before the season, preferably 6 wheel, as it is simple, yet robust and maneuverable. We took 2.5 weeks to get a drive CAD out, which was ridiculous. Part of it was that we had a hard time choosing between 6 and 8 wheel, but also, I was just inexperienced(my first year CADding). If they practice, getting a drivetrain CAD done in 2 days can be easily done, and then they will have extra time for manipulators. Furthermore, you will save time by doing this because you don't have to remachine parts.

[Mr. Van]

Originally Posted by MICHAELABICK

...I would recommend CADding a full drive system before the season...

Careful here. Check the timeline rules regarding design and fabrication. If I've got it right (at least for this year and several previous years), you can't take a CAD model you worked on prior to kickoff and use it to fabricate parts without making substantial changes or publishing the files for everyone to use.

- Mr. Van
Coach, Robodox

[MichaelBick]

I meant that they CAD the drive system before for practice, and then redo it for the season. Personally, I wen't into the season, and didn't know some things that I should have known. For example, one dilemma I had was deciding wether to use a bearing block, and after that, on a design for a bearing block. Sure, once you have seen Chief Delphi threads on the subject, it is an easy problem to solve, but it is much easier if you already decided on a design path before the season, and are just repeating decisions you made in the preseason, on a drive train that is optimized for the game.

[shawnz]

Regarding this "fabrication is/isn't engineering" business:

We are a team that fabricates entirely in-house (with CAD, though), but most people on the team agree that it's not very sustainable to operate this way -- especially with the short length of the build season. However, an earlier poster noted that the designers may not understand physical limitations as well without manufacturing experience, and I completely agree. This is true even if in-house CNC is in the budget.

The most obvious answer to this, IMO, is to train manufacturing in the off-season primarily where the deadlines are significantly more lax. Students who have that knowledge can then help the designers understand what will and will not work during the actual build season, where out-of-house fab or CNC (i.e., whatever gets the job done best) would be preferred. In addition to a better understanding of the implications of various design choices, I believe this basically satisfies the "moral" issues that some people have with fab-less teams as well.

Our team in particular has yet to implement this. Of course, such a strategy may greatly increase the off-season commitment required (depending on the team, of course), but that's just what it takes to be successful in a competition like FIRST -- hard work and commitment. Regardless of your priorities, training strategies, morals, or whatever else, there isn't a successful team that hasn't worked hard to get where they are, regardless of how they accomplished it.

[Anupam Goli]

Thank you all for your responses.

I don't mind in house fabrication, in fact, I loved it as a freshman, being able to manufacture my own parts and placing it on the robot. But fabrication without a design is meaningless. This year our mechanical lead student only used L-channel and 80/20 because of the ease of building, and how you can design around the build. When he heard about 1311's robot being fabricated outside and being amazingly done, he said "That's not fun, I like solving problems while building, that's more fun". Fabricating is fun, but fabricating without a design is foolhardy. I think that this attitude needs to be reversed.

[MichaelBick]

I completely agree. Yes it is fun to fix problems while building, that is even what our team, and many others did for the minibot. But remind him, that if you do that, it takes up much more time than if a CAD student solved the problem before you machine a part.

[DinerKid]

1768 does very very close to all of our fabrication in house. We have one Bridgeport and one functional lathe, we work hard to make sure that these machines are running all the time. This year we sent out 3 shooter parts to be water jetted, we had never done that before but we didn't see any other reasonable way to make a large cam or to frame out of shooter other than water jetted plates.
Because we need our machines to be running all the time and they are often the rate limiting step in the robot construction process we have started using quite a bit more ABS in our designs, it machines like butter and is incredibly strong.
We have our CAD team working all the time as well and the robot construction doesn't usually pass the CAD until mid way through week 5 or so.
As far as the in house vs sent out argument I think students are going to learn either way, it is just a matter of what they learn and in what areas they excel.

~DK

[nerdherdmember]

Originally Posted by DinerKid

Because we need our machines to be running all the time and they are often the rate limiting step in the robot construction process we have started using quite a bit more ABS in our designs, it machines like butter and is incredibly strong.
~DK

Could you explain how you use ABS? Team 422 uses aluminum C channel, Angle, and 80/20 for almost everything, and I would be interested to hear about what different materials teams use, and how. I also spent a lot of time talking to 1829 about their use of carbon fiber at the Virginia Regional, so my interest in odd build materials can be considered piqued.

[Anupam Goli]

I'm trying to encourage my team to use more aluminum tubing and composites. 80/20 is really heavy and though easy to build with, does not make the best frames. Aluminum tubing, when proper weight reduction holes are drilled, is very strong and can be very light.

[EricH]

Originally Posted by Wing

This year our mechanical lead student only used L-channel and 80/20 because of the ease of building, and how you can design around the build. When he heard about 1311's robot being fabricated outside and being amazingly done, he said "That's not fun, I like solving problems while building, that's more fun". Fabricating is fun, but fabricating without a design is foolhardy. I think that this attitude needs to be reversed.

He's almost right. Solving problems while building is not more fun after this competition, however. The real-world version of that (without the boss's response to such a quote if said aloud) follows...

"I like solving problems while building, that's more expensive." And that, my friends, is why you CAD thrice, measure twice, and cut once (and then cut again on any identical parts), and measure again once you're done cutting.

Do a cost add-up. Figure minimum wage for every student, and normal wages for the mentors. Figure out how much the season cost in labor and materials. Now, subtract any material wasted by building something wrong and any time wasted fixing something that was built wrong (and the associated man-hour cost). I think the results might surprise everyone on the team.

There's nothing wrong with building then designing, if you don't mind wasting money and time, and not getting a real-world engineering experience.

[Brandon_L]

Originally Posted by EricH

He's almost right. Solving problems while building is not more fun after this competition, however. The real-world version of that (without the boss's response to such a quote if said aloud) follows...

"I like solving problems while building, that's more expensive." And that, my friends, is why you CAD thrice, measure twice, and cut once (and then cut again on any identical parts), and measure again once you're done cutting.

Do a cost add-up. Figure minimum wage for every student, and normal wages for the mentors. Figure out how much the season cost in labor and materials. Now, subtract any material wasted by building something wrong and any time wasted fixing something that was built wrong (and the associated man-hour cost). I think the results might surprise everyone on the team.

There's nothing wrong with building then designing, if you don't mind wasting money and time, and not getting a real-world engineering experience.

Its cheaper for us. We don't have the money to send parts out to be made. We do have a pile of scrap metal and nearly infinite wood from our schools wood shop. Its what works for us. This is not meant to be a "Real world engineering experience". This is a robotics competition with teams from high schools made up of high school students that are mentored by real world engineers (be it we don't even have those). Try telling your potential boss "I'd like the job, but you're going to have to hire my mentor as well". In a real world engineering situation, CAD and then sending parts to be made would be the best choice. But this isn't the real world, and not all of us have the luxury of money. There is no right or wrong way to build a robot during build season. It depends on a teams situation what is cheaper. Don't assume everyone is in the same financial boat as you.

[EricH]

Originally Posted by Brandon_L

Try telling your potential boss "I'd like the job, but you're going to have to hire my mentor as well".

Usually, they already did. Most companies will have a time period where new hires have a mentor to help them adjust to the company.

If you have an infinite supply of scrap material, that's one thing. But, not every team will have that. There are teams out there that have to buy all their material. And, some of those teams are on a shoestring budget (as in, before they buy material, they have to look at can they afford it, or can they find a donation). For those teams, making it right the first time--or screwing it up so it CAN be used--is important.

Now, regarding it being cheaper for you: I also said that you should factor in labor. With materials being a non-issue, let's assume that each mistake or miscalculation costs you 15 minutes of 2 students working to fix it, on average. That's about 1/2 man-hour (that would otherwise not be used), and if one man-hour is 8 bucks, that's 4 bucks for an average mistake if everyone was paid. I'm not going to ask how many you make per season, because there are a lot--but let's assume that over a full build/competition season you make 100 mistakes to make calculations easy. $400 for fixing mistakes, in the entire season. Not too bad, unless you're on a shoestring budget. (Yes, I AM AWARE that all time in FIRST is volunteer time, so all labor is free unless you're dealing with an outside shop. I'm also quite aware that I didn't factor in major "Oh great that part will not work at all" redesigns, which take substantially longer.)

This isn't the real world: but it is meant to reflect the real world. Your team is a business, or can be looked at that way. If your team was a business, with paid employees, you would have far less room for error. Some planning before you build is necessary.

[MichaelBick]

Originally Posted by Brandon_L

Its cheaper for us. We don't have the money to send parts out to be made. We do have a pile of scrap metal and nearly infinite wood from our schools wood shop. Its what works for us. This is not meant to be a "Real world engineering experience". This is a robotics competition with teams from high schools made up of high school students that are mentored by real world engineers (be it we don't even have those). Try telling your potential boss "I'd like the job, but you're going to have to hire my mentor as well". In a real world engineering situation, CAD and then sending parts to be made would be the best choice. But this isn't the real world, and not all of us have the luxury of money. There is no right or wrong way to build a robot during build season. It depends on a teams situation what is cheaper. Don't assume everyone is in the same financial boat as you.

Still, CADding should be done. Unless you also have an infinite amount of students, you still have time constraints. How much time do you waste when you have to remake parts? Also, you don't always need to pay a shop to do things for you. Many will give you sponsorship.

[Brandon_L]

Originally Posted by MICHAELABICK

Still, CADding should be done. Unless you also have an infinite amount of students, you still have time constraints. How much time do you waste when you have to remake parts? Also, you don't always need to pay a shop to do things for you. Many will give you sponsorship.

We do CAD, I wasn't saying we don't. My point was sending parts out to be cut doesn't work for everyone.

Now, regarding it being cheaper for you: I also said that you should factor in labor. With materials being a non-issue, let's assume that each mistake or miscalculation costs you 15 minutes of 2 students working to fix it, on average. That's about 1/2 man-hour (that would otherwise not be used), and if one man-hour is 8 bucks, that's 4 bucks for an average mistake if everyone was paid. I'm not going to ask how many you make per season, because there are a lot--but let's assume that over a full build/competition season you make 100 mistakes to make calculations easy. $400 for fixing mistakes, in the entire season. Not too bad, unless you're on a shoestring budget. (Yes, I AM AWARE that all time in FIRST is volunteer time, so all labor is free unless you're dealing with an outside shop. I'm also quite aware that I didn't factor in major "Oh great that part will not work at all" redesigns, which take substantially longer.)

Again, this isn't the real world. We don't pay for labor. If it were real world, I agree 100%.

[EricH]

Originally Posted by Brandon_L

Again, this isn't the real world. We don't pay for labor. If it were real world, I agree 100%.

If I have to tell you to read the whole post, I will. And in the part you quoted, I specifically stated that I was aware that paying for labor was not an issue, because it is entirely donated. Do I have to make it stand out like a billboard?

I did note that FIRST is a reflection of the real world. As such, real world analysis and skills are a highly useful tool. However, they should not be the sole driver. If FIRST was real world, you and your team would be paying for that infinite supply of scraps, and for the labor. You probably wouldn't be functional financially, or would be having a lot of trouble paying bills. Do the analysis sometime, using the FIRST BOM accounting methods for the materials, and minimum wage for the labor costs. I think you'll be surprised at just how much your robot is actually worth. (I conservatively estimate any given Kitbot+stuff box-on-wheels built by a small team at about $9K. The bigger the team and the fancier the robot, the more it'd be worth. I'm not factoring in any awards earned by said robot, either.)

But when you get to the real world, you will have to worry about that. Engineering is a balance of money, time, and quality. (In some fields, use weight in that balance as well.) You can pick one, or maybe two, but the third will suffer. Reduce the cost, the time might go up or down, but the quality is almost certain to go down. Reduce the time, the cost goes up (for expediting) and the quality goes down. Increase the quality, one or both of time and money goes up. This is a real-world exercise, and this is engineering--learn to balance them now so that you can deal with the balancing later.