Robotics Education & Competition Foundation
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The Q&A is closed for the 2021-2022 season. Any rule changes or clarifications pertaining to the 2022 VEX Robotics World Championship will be included in the April 5 Game Manual Update. Teams attending VEX Worlds who wish to pre-submit questions for the driver's meeting should have received a contact form via email; if not, please contact your REC Foundation Team Engagement Manager for more information.

Official Q&A: VRC 2021-2022: Tipping Point

Usage Guidelines All Questions

Plastic Limit


Jess Zarchi
23-Dec-2021

Hello,

With the recently answered Q&A 975, the community has a few questions on how much polycarbonate teams are allowed to use.


Q&A 975

The intent of the rule is that all of the parts which are cut would theoretically nest into a single 12"x24" sheet. Teams are not required to literally use a single 12"x24" sheet of plastic. Yes, this is functionally the same as saying that the total surface area of all parts must not exceed 288 square inches.

R7-f from Nothing but Net Q&A 1 (this is R10 in the Tipping Point manual)

Q. Example for Question 2: Let’s say I start with a 12" x 24" sheet of allowable plastic, and cut two 12" x 11" rectangular pieces for use on a robot. This leaves me with a 12" x 2" piece of plastic left, this piece having an area of 24 square inches. I then get out a new 12" x 24" sheet of plastic (identical to the previous sheet) and cut from it a circle with a 4" diameter (having an area of ~12.56 square inches) for use on the same robot. This circle could not have been cut from the remaining piece of sheet 1, but is lesser in area than that piece, and the total area of all pieces used on the robot (the two 12" x 11" rectangles plus the 4" diameter circle) is less than the area of a single 12" x 24" sheet. Would this be legal under <R7f>?

A. No, this would not be legal. These three pieces could not be reassembled into a single 12" x 24" sheet.

R7-f from Nothing But Net Q&A 2 (this is R10 in the Tipping Point manual)

When using plastics, all pieces used must be able to be assembled into a sheet no longer than 12"x24". This is different than a maximum total area.


Attached are two images, both rectangles are 12"x24". The highlighted portions of both sheets are equal in surface area, but the left couldn't be reassembled into a 12"x24" sheet.

  1. Is the plastic limit based on reassembling parts into a 12”x24” sheet, or is it based on total surface area?
    a) If it’s based on surface area, how are holes within parts accounted for? Are holes/pocketing subtracted from the total surface area of the part?
    b) How should competitors prove the surface area of complex parts to inspectors and referees?

Thank you for your time! img

Answered by committee

Thank you for bringing this to our attention and for attaching an example image. It turns out that "theoretically nesting into a single 12"x24" sheet" is not functionally the same as the total surface area exceeding 288 square inches. The answer to Q&A 975 has been updated, and R10 will be clarified further in a future Game Manual update.

  1. Is the plastic limit based on reassembling parts into a 12”x24” sheet, or is it based on total surface area?

The former. However, the other portion of the answer from Q&A 975 is still correct - Teams are not required to literally use a single 12"x24" sheet of plastic.

b) How should competitors prove the surface area of complex parts to inspectors and referees?

The intent behind the requirement being "nest into a single sheet" instead of "288 square inches" is specifically to reduce complexity during inspection. In most cases, inspectors should be able to tell "at a glance" whether a given Robot is exceeding the permitted area (such as having four 9.5" diameter circles).

If a Robot is "pushing the limit", such as by having many small CNC'd parts that are nested perfectly to fit in a 12"x24" space, it would be within an inspector's authority to request a demonstration or documentation of the parts' legality. We would not expect this request be an issue, for Teams who are abiding by the rule; generally speaking, a Team who is pushing the limit to this extent knows that they are doing so, and this type of detailed Robot design work is a perfect example of documentation that should be included in an Engineering Notebook anyways.

We are not going to mandate a specific form of documentation or proof; however, suggested examples could be CNC router drawings, BOMs that match labeled parts on the robot, or even a photo of all plastic parts disassembled and laid on a 12x24" area.

Ultimately, this is similar to the answer from the "Commercially Available Hardware" Q&A. In most cases, it shouldn't require detailed discussion, but it is well within an inspector's authority to determine whether a Team's supporting documentation / evidence are satisfactory. If Team is unwilling or unprepared to oblige with this request, then it is probably a good sign that the spirit of the rule is not being followed.