Answered: Clarification on 3D Printed Parts

In a previous thread, the following ruling was given:

A teammate interpreted this as they wanted to print gears of different dimensions, I interpreted this as a blanket ban on printed parts, so to clarify:
If parts with the exact same dimensions are printed using the same kind of plastic as VEX parts, would these be legal or illegal? (If the ruling is different by part, we plan to print spacers, but we want a ruling on all parts)

In the manual it is rule R7b:

3D printed parts would not be considered identical to VEX parts, even if the dimensions were the same.

Sorry to necro this thread, but may I know why this is not allowed? How are lexan and other plastics allowed then?

obtaining and cutting lexan is cheap
3D printed parts are not

this gives rich teams a big advantage which is not what VEX is about

I see your point murdo, however I think the printer they stated that the CTE department has so its not acuaulty there team and 3rd printing in cheaper then buying vex parts.

The idea is that no matter what specific teams would experience in general it would give an advantage to privileged teams. Vex wants to give an even playing field to everyone and with custom printable parts that just isn’t the case.

There is also the question about the material composition. All 3D printers do not use the same plastic as VEX which I believe for most is Dupont’s Delrin.

This. Also, it’s the same story with using 3rd party batteries and chargers - VEX can do quality assurance which poses a risk to safety of everybody. Now, I would argue that everybody who attends a competition has to sign a release form which means that you can’t sue VEX if you get hurt. I can understand the need to prevent teams from using 3rd party batteries, not so much printed gears and such, especially if they’re identical to the real VEX product. With that in mind, it would be too easy to cheat and not make your 3D printed object identical. So rather than having a mutual trust, it’s easier and more fair to just ban 3D printables all together. Imagine VEX allowing people to print gears and such, and a team getting to the World Championship finals only for somebody to discover that their parts were not identical to the VEX ones - imagine all of the teams that were beaten by that one team who was cheating.

That’s my two cents, I’m sure somebody will disagree with me…

The reality is at this level 3D printed parts are never going to be exactly the same as injection molded parts. If you did print some gears of the same pitch I’d be surprised if they didn’t break within 5 minutes because the gear faces are small and loads high. Even with more expensive filaments 3D printing at this level is really just a glorified hot glue gun on an XYZ table.
It’s nothing to do with privilege or who can afford what - VRC is a competition based around VEX robotics parts. This makes it simple for schools (or anyone for that matter) to implement and you can even get away without any mechanical facilities at all if necessary.
If you really wanted to 3D print and machine stuff from raw materials go do FTC. Aside from some electrical component constraints you could 3D print your whole robot. I mentor teams in both competitions and having component constraints in VRC is also a good engineering experience since students must adapt accordingly.

For the record lexan/polycarobonate is not the only plastic permitted in VRC Toss Up.
<R7> f. Non shattering plastic from the following list; polycarbonate, acetel monopolymer (Delrin), acetal copolymer (Acetron GP), POM (acetal), ABS, PEEK, PET, HDPE, LDPE, Nylon (all grades), Polypropylene, FEP; as cut from a single 12" x 24" sheet up to 0.070" thick.

But then you can say that some teams can’t afford some parts on the website. 3D printing makes the $$ back over time, and its not even that expensive. We bought our printer for $1000. I have a feeling its a business and money thing for VEX themselves, not the teams. What if I wanted spacers? I don’t want to pay exuberant shipping charges. I don’t want a pack of them. I just want a few. In regards to tampered dimensions, shouldn’t inspectors check for valid parts and specs?

When we are talking about the subtle differences that people could easily abuse. Measuring every spacer is ridiculous. The parts on the site are designed to be cheap enough so that high school and middle school clubs can afford them. The only part were load wouldn’t affect the abilities of parts is in spacers and 1000$ in spacers is pretty ridiculous for most teams.

I can see school teams having access to 3D printers through their schools, but it’s pretty unrealistic/impractical for a homeschool team to just go out there and buy a 3D printer for the robotics team…

~George

If we could 3D print, VEX would make no money because everyone would have (mostly) plastic robots.

They would be pretty cool though…

The problem is where do you draw the line, if it’s ok to use a $1000 desktop printer, is it ok for me to use the $30000 printer we have at work for rapid prototyping. If that’s ok then what about the SLA (stereolithography) machine we have budgeted this year that costs over $400,000. Then why not allow desktop CNC machines (Intelitek would love that) etc. etc.

It keeps everything simple when we have to start with VEX (or identical) parts and modify them from there.

^^ This is key. I don’t really care about the “favoring rich teams” argument (typically); it is because of the lack of a “brightline” in this particular issue that makes me not want 3D printed parts. As cool as it could be, it opens the door to semi-professional robots/robotics equipment, and it’s hard to rationalize how far to open that door.

//Andrew

Inspectors don’t have that much time at most competitions. Inspecting 3D printed parts to make sure that they are identical to VEX ones is a lot harder than simply checking that a part is from VEX, and that would add time. You would have to be checking for things like non-standard numbers of teeth on gears that can’t be easily accessed from the outside of the robot.

An inspection takes 2-5 minutes usually. If you want to extend that time, you either have to increase the proportion of the time at the event that teams spend being inspected (not fun) or you need more volunteers (not easy). Keeping inspection time to a minimum is one of the things that helps make VEX what it is.