Functional 3D printed parts are not allowed in the Middle School and High School levels of the VEX Robotics Competition. 3D printed parts are not considered identical replicas of official parts due to differences in material type, strength, or other physical properties. Please see these previous Q&A's:
VEX U teams are allowed to use 3D printed parts as specified in VUR2, quoted here for reference:
<VUR2> Teams are allowed to fabricate their own unique VEX parts from the following additional items, for each of their robots:
a. Plastic cut from a single 6” x 6” x 1” block.
i. Examples of “plastic block” are PVC, Delrin, and ABS.
b. Steel OR Aluminum cut from a single sheet no larger than 12” x 12” and no thicker than 0.070”
c. An unlimited number of plastic 3D printed parts, each less than 3” x 6” x 6”.
Note: these are not measured by “volume”. Teams are restricted as though the components they are constructing were made from the raw materials listed.