Custom Plastic

Any plastic that does not serve a function beyond decoration does not count towards the legal plastic limit. A piece is considered non functional if the performance of a robot or subsystem is not in any way altered by the removal of the piece(s). (A piece that is used to shield game elements from entering or being stuck in a portion of the robot is considered functional)

Robots may use custom-made parts cut from certain types of non-shattering plastic. It must be possible to have cut all of the plastic parts on the Robot from a single 12” x 24” sheet, up to 0.070” thick.

Plastic parts do not have to be literally cut from the same original 12” x 24” sheet. However, all individual parts must be able to “nest” or rearrange into a 12” x 24” area.

Legal plastic (functional or decoration) types include polycarbonate (Lexan), acetal monopolymer (Delrin), acetal copolymer (Acetron GP), POM (acetal), ABS, PEEK, PET, HDPE, LDPE, Nylon (all grades), Polypropylene, and FEP.

Robosource - https://www.robosource.net/plastic-sheets

VEX - https://www.vexrobotics.com/polycarbonate.html

Manufacturing Components

Templating

Templating can be done in 2 ways but is critical for ensuring that custom plastic parts will fit well into the greater robot design.

Manual templating can be done on a sheet of graph paper where key aspects of the design are sketched out (cuts, bends, holes, etc.) and the overall outline is cut from the paper and measured against an existing mechanism. The template can then be traced onto a sheet of plastic & cut.

Use a Dremel, Hack-saw, Band-saw, or Scroll-saw to cut the plastic & a drill press for any holes.

If the part, or entire robot, is being designed in a CAD program, then the face of the part can be exported, printed, and traced onto components. This is a great way to make more precise designs than may be possible with a pencil on paper, but without the need for additional tools like a laser cutter.

Laser Cutting

Laser Cutting is a legal technique in VRC & VURC as long as the material being cut itself is legal to be used. Find more information in the Laser Cutting Article

Bending

To bend plastic, use a heat gun, first, securely clamp the plastic sheet along the desired bend line, ensuring it remains stationary. Gradually heat the bending area with the heat gun, moving it back and forth evenly until the plastic becomes pliable. Once softened, gently bend the sheet to the desired angle and hold it in place until it cools and solidifies in the new shape

Make sure this is done with proper PPE (gloves, safety glasses, pliers, etc.) and under adult supervision. Do this in a well ventilated area & don't use a hair dryer.

Teams Contributed to this Article:

• BLRS (Purdue SIGBots)