Managing Parts

I am interested in how other teams manage students access to inventory and parts. I was the coach of another team the last couple of years which was small and had low resources. We managed things without much waste and it was easy. The students seemed to understand we needed to make very good use of what we had because it was unlikely we could afford more.

The team I am on this year is about 20-25 students and they treat things like we are operating from a bottomless pool of money. They feel free to grab any part at any time without asking or evaluating the cost and waste is high. Some of this waste is related to learning how to do things right (machining, wiring, assembly …) however they don’t have an inherent fear that if they mess something up or lose it that they won’t get more. I have started pushing back, pointing out the problem with this, hiding parts and controlling things but I am struggling to change an ingrained culture.

Any suggestions to put a good system that doesn’t require too much red tape would be greatly appreciated. Bag time seems like a good time to figure this out before our spare parts inventory is consumed.

We have ~30 kids on our team, and at any given meeting there are 15+ kids in our work room.

What the other mentor and I try to do, is any time a student is about to cut/drill/modify anything, we stop and ask them questions about what they’re doing, why they’re doing it, what they’re going to learn, etc.

So we control the flow of materials by asking critical thinking questions and evaluating if the cost of what they’re doing is worth the benefits we’d gain by them doing whatever they’re going to do. We often try to ask/suggest if there are any ways that the same thing could be achieved with cheaper materials.

For example: some students want to make a mock-up of a part that will be made out of 1/4" Al sheet, and they want to make the mock-up out of thinner Aluminum sheet metal to make sure that it fits on the robot and doesn’t hit anything.

We ask what they’re trying to accomplish, and ended up suggesting that they make the cut-out from cardboard to test the fit instead of using sheet metal.


Ask critical thinking questions to get the students to think about what they’re trying to accomplish and see if there are any other ways to accomplish their goal. This also helps the mentors keep track of what’s going on and meter the materials.

Thanks for the tip. Anything that gets them thinking is good.

I do expect a certain amount of scrap. I even make it when I’m trying something. I just need to strike a better balance. Part of my frustration is that they still need to learn to slow down and do it right instead of doing fast and getting whatever quality happens. It isn’t the whole team but it is too many.

Yeah, I feel that.

I always tell the new freshmen that they’re going to hate me, because I’m going to ask them all of the critical questions that they didn’t want to think about (well, I do my best, I can’t think of everything). The returning students laugh about it, because they remember being in that position, but now I see them asking themselves these questions and coming to me with the answers before I ask them because they know what I’m going to ask

We spent some time in the offseason making a spreadsheet inventory of everything we have in the lab. Now, if anyone wants to use anything, they have to update the spreadsheet. We place importance on this by emphasizing early on how if you take something and don’t update the sheet, we may design a part thinking we have a certain piece but end up not having it and that causing issues. It’s been working wonderfully so far, and also helped teach all our rookies what different parts were called so they had a great headstart.

Once they do take pieces, we do the question series mentioned above.

CAD first. Push drawings second. Then build.

If something is happening on the robot, drawings are being referenced. If not, build does not happen.

If you are not running it this way, then I am not certain how to handle the inventory. You are basically putting out fires at this point - I know from experience.

Our team doesn’t have enough of a CAD base to get good working CAD in the first week or two, so this wouldn’t really work for us.

I wish our team did work like this, and I try to push it every year, but we always get to week 2-3 and our CAD is nowhere near complete, then we start building and we deviate from the CAD almost instantly. It’s not great, but that’s what happens.

Our parts management site is a fork of cheesy parts. It’s been working pretty well for us, but we’re in the process of rewriting it to match our own fabrication process better.

The ideal is to design everything in CAD then build, no sane person would dispute that. (I build custom equipment for a living and that’s how we do it.)
However since I have to work with the skills I have which doesn’t include CAD or mechanical design. I find myself sketching sub systems prior to build or (more often) while holding parts in my hand and figuring out as I go. We prototype and iterate. This is not the waste I am concerned with.

I’d love to hear about a realistic process to take a group of high school students that haven’t built anything as complex as a robot, don’t know what parts are out there, aren’t familiar with simple mechanical systems and don’t have stellar CAD skills how to design our robot in two weeks on paper first. (Let’s throw in that it has to be built out using mostly hand tools, must be durable, most of the parts require shipping and there is a time limit.)

Hey…I’m starting to feel better about some of the scrap.

Sounds like we’re in the same boat in this aspect. However, I’m also a Design Engineer who spends most of my day in CAD, so I know how to do it all properly, but in a professional sense, not for FRC.

I’ve been trying to find a good way to speed up the front-end of our season, and it seems that you and I could both benefit from the same information (if anyone out there has it and is willing to share their experiences…)

For managing inventory, we had a crib that was more or less free for all. It was decently organized. The more organized and visible things are the better and you’ll save tons of money this way versus buying parts you already have. Raw stock (plate, tubing, etc) that was meant for the competition/practice bot was wrapped up and a mentor had to give permission to use that material. Scrap bins were fair game.

Past the initial prototype stage we’d create buckets and store parts for each subsystem there. These would only be touched by that subteam.

As for getting kids who know nothing (mentors included) up to speed quickly… I think the biggest thing is examples. Physical examples. Showing how the VEX gussets, bearing brackets, bearing blocks, motor mounts, etc work is huge. You can have these parts but if no one knows how to effectively use them then they won’t get used. One fall we built a handful of examples showing how these were used and that worked well as I could then pull one out and show a student/mentor how a COTS item can achieve what they are trying to do quicker and easier.

Side note: Unless you have very good machining abilities, use bearing blocks or bearing gussets from VEX for everything. Don’t try to drill your own bearing holes. Most of the time they won’t line up and will take forever to drill.

I wish my team would do this haha. They loooove the 1/2" flange bearings that need a freaking 1-1/8" hole… so much time spent drilling those holes. Even when they pilot drill all the way through something, there’s still misalignment issues.

We are a community based team without a fixed build space, or a school shop to build out of. We have a chop saw, portable table saw, drill presses, (had a small bandsaw but it died this year), and had power tools. It can be done.

We do the robot in design in CAD, print drawings, review (which includes lead design mentor signoff), and then fab process. All parts go from raw material to finished parts, with their drawings, until they are binned as either practice bot or comp bot.

We look at last years design in the fall, and talk about parts selection and what we already have, design standards, plus standard places to get robot stuff.

Part of the fall activities are to look at simple machines, and past years robots and understand design solutions. We also try and do some sort of fall building activity, mostly in wood. This year we build simple ball shooters.

I cannot truly speak for CAD as I am the fab mentor, but we have a CAD training session in the fall season, which culminates typically in design a simple robot off a skeleton design, as an activity for the design subteam.

After kickoff we paper sketch/design and prototype (mostly in wood, quick and dirty) until we decide on a main design concept. We break that design concept down into subassemblies, design mentor creates a framework to hold the subassemblies, we import the kitbot into the design and then students get subassemblies to work on. Design mentor assists in this but it really is the students design (which leads to “interesting” design decisions). As we freeze assemblies, students make drawing (based off a template) and we start fabrication. Ideally students fabricate and if possible assemble their assembly.

The rule is everything goes in CAD. This likely slows us down from a more iterative process, but it is deterministic, and it teaches the design team about CAD. Plus it is way easier to tweak and fiddle when your design is in CAD. Plus you can do more advanced stuff like stress analysis on critical parts or get a sane weight estimate, if the design is in CAD.

We have taken students from never touched CAD to designed something in their first year. It also simplifies fab and assembly, since students are fabricating off of real dimensioned drawings, and we can quickly turn out limited assembly drawings, or just refer to the CAD model (well actually the students can, I actually never logged into a CAD laptop this build season, which I consider a huge success).

We love 1/2" hex flanged bearings and tend to have them all over the design.

Get a flat surface (granite plate is best) and a decent digital height gauge. Teach the students how to scribe parts and life will be much much better.

Something like:

Will improve your tolerances tremendously.

Between using a decent measurement device, good drill bits and thinking through where we wanted to drill parts and where we wanted to match drill, we have significantly fewer alignment issues.

I know there’s a right way to do it, and I can do it myself (generally just use blue Dykem and some calipers as long as I have a nice flat/smooth edge). The hard part is getting the students to both create an accurate layout and then also accurately position the part on or rickety drill presses.

Our organization process starts in the Fall. We are lucky to have room for a lot of shelves, so these get filled with boxes and bins. Controls, parts, motors, brackets, pneumatics, bolts and nuts and washers (sorted by size), bumpers, gearboxes, wheels, belts and pulleys, etc. In the fall the entire team reorganizes this so they know where things can be found. These parts are mostly a free for all for prototyping and building. While this does get in some disarray by the end of the build season, it is still usable.

Once the build season starts and specific parts get ordered for subsystems, each subsystem gets a dedicated (i.e. labeled) bin (or a few) to keep their parts in. The team understands that if they ‘borrow’ from these bins they may not have a working robot when we get to competition. Borrowing is frowned upon, unless it is agreed upon, or a replacement part is ordered.

For getting the new team members up to speed, we hold Training Modules in the fall. Design, fabrication, controls, and business are typically the main modules; team members might take one or two at a time, and are asked to take different ones each year. This way they know how to build things, and the students in fabrication are properly trained on the power tools. Depending upon the maturity of the students, these can be taught by students (with mentor oversight) or by mentors.

We did not take use of CAD fully until this season. It was a major reset for our team and the mentors received much backlash from existing members because that is not the way we had done it in the past. However, the practice has played out very well for us this year. We may not have the world’s greatest robot - but for us this process has helped to produce the best robot for FRC 4607 to date.

Oh - and we did not start building until late in week 3 of the build season. We now have a practice robot that is nearly an exact replica of our comp bot.

I highly encourage your team to work on CAD this coming off-season. It will pay dividends. To steal a tag line from a fellow MN - “CAD all the things!”

On a different note, we also went to HDX stackables for most of our hardware, pneumatics, electrical (terminals), etc. This has allowed for a quick visualization of what we need to order now and what we don’t need to order for a few more years.