Robotics Education & Competition Foundation
Online Challenges

Glitch Optimal Aiming System


Entry ID #: 6005
Created: Mon, Jan 14, 2019 10:08 AM

Team 50566C “Glitch” Crestview Middle School, Missouri VEX Optimal Aiming System   Software Used: Autodesk Fusion 360, Education License   Why was it created? In this year’s VEX game, we have noticed the problem of aiming robotic systems.  Past games, such as Starstruck and In The Zone (excluding Nothing But Net, because we are a middle school team we did not have the chance to play it), didn’t require scoring objects to be launched from a robot.  In those games, aiming was rather unimportant, if not completely unnecessary. Turning Point is one of the first game for our team that requires systems to be aimed, but the current aiming systems require clunky rack and pinion gears or a gear fixed to the system to be aimed.  Those are the only effective ways to do it, but as great as it is, the VEX system isn’t perfect. These systems can be a waste of precious space and parts.   What is it? So we propose an idea -- a more sleek and elegant rack and pinion system.  This new part, which we have decided to call the optimal aiming system (OAS), is a modified version of a rack and pinion gear.  Instead of being completely straight, the OAS has a curve.   How does it fit into a VEX robot? The OAS contains three independently moving pieces: The gear, the curved rack gear, and the rack gear shroud.  The shroud is the main backbone of the piece; it anchors the OAS to a VEX part, yet allows to curved rack gear to move.  One side of the curved rack gear, or CRG, will attach to the system that you want to be aimed, while the other end is locked inside the shroud.  The opposite side of the shroud is mounted to a stationary piece, such as the chassis. The shroud will remain stationary, but CRG will be freely allowed to move. A standard rack gear converts rotary motion into one-dimensional linear motion.  However, the rack gear in the OAS converts rotary motion into linear motion along two directions, one direction moving up or down relative to the axis of the rotary motion, and the other direction right or left relative to the axis of rotary motion.  When the gear is rotated, it causes the CRG to move both up and right (Or down and left, depending on which way the gear is spun).   How was the part created? Autodesk Fusion 360 Education License was used to make the OAS.  The OAS was created with parametric modeling, rather than direct or freeform.  The principle of parametric modeling is simple: 2D sketches are made on a plane, then extruded into the third dimension.  New sketches can be made on this new shape, then extruded again to make protrusions or holes. History of all features is kept, so if a past feature is updated, the later features adapt to the change.  The curvature of the OAS comes from a section of an ellipse. Teeth were copied directly from a CAD model of a VEX gear found on the VEX website. The Fusion 360 function “pattern along path” was used to add more teeth to the CRG, which will mesh with any standard 36 tooth VEX gear.  A model of a C-channel found on the VEX website was imported as well. This C-channel was used to aid in the design of one end of the CRG that will attach to the ball launcher. Calipers were used to measure physical VEX parts to make designing OAS easier. The VEX bearing flat was measured to create the part of the CRG that attaches to the metal piece.  The shroud was made similarly to the CRG, with a section of an ellipse. A channel was created on the inside to allow the CRG to move within it. Both parts contain a matching pair of notches and protrusions which will prevent the CRG from accidentally exiting its shroud. Both fillets and chamfers were used to give the part a nicer look and feel.   Make It Real: The OAS was 3D printed on the Flashforge Finder in PLA.  If this part was to be used in an actual robot, a stronger plastic, such as ABS or acetal should be used.  Unfortunately, there is not an ideal way for the OAS to be printed without support, so the OAS must be printed in four parts.  The main assembly, the two parts to connect it to metal pieces, and one key to help align the bottom connector and shroud while assembling. The main assembly used a technique that is very unique to 3D printing -- a process called print-in-place.  Because 3D printed objects are built up layer by layer, different objects can be locked inside one another. The CRG was printed inside the shroud so that it cannot be removed. The first iteration, which had been designed to fit a twelve tooth gear, was too small for accurate 3D printing.  The size had to be adjusted to fit a 36 tooth gear, so that the OAS was large enough to be printed correctly.   Conclusion: This project was a great way for me to learn about the functions, tools, and features of Fusion 360.  Joints, a feature that was very unfamiliar to me, were used to help animate the part and better understand how it will work -- or if it will work.  Motion links were another feature I learned that were needed to animate the part. I was able to discover new tools, such as the pattern along path feature, that was critical in positioning the teeth along the CRG.  I feel that learning how to model objects is a great skill for anyone to have. 3D modeling can be used to design a robot in three dimensions to make it easier to understand and build later on. 3D modeling has definitely taught me a lot, such as design considerations for different manufacturing processes, different aspects of geometry, how to take accurate measurements, and how to learn from failure.   Document Requirements: Brief introduction: Identify why you created the part – what functionality are you improving or what issue are you solving? Explanation of how the new part would be used and how it fits into a complete robot design. Note: you do not have to design the complete robot, just the custom part itself. Explanation of how you used Fusion 360, Inventor and/or Tinkercad to create your new part AND clearly state the version of the software you used. Brief conclusion: What did you learn from this project? Will you use 3D design software in the future? If so, what for? How does this software help you if you are on a competitive robotics team? Will learning 3D design software help you in your career path? If so, how?   Judging Information: New part design and function: How well does the new part meet the requirement of being useful in building robots? Does it improve functionality or solve the intended issue? Is the part design efficient, simple, and elegant? Does the design work show skill proficiency using Fusion, Inventor and/or Tinkercad? Is the software version clearly identified? Written description: Judged on clarity, thoroughness, design process and description of use. Overview images: Quality and thoroughness of the images. CAD datasets and 3D printed files: are only the required formats of .ipt, .iam, .f3d, or .stl used?   Entry Requirements: This document Multiple pictures, including a digital rendering and a picture of the 3D printed part (All images must be labeled with the software used) .stl file .f3d file animations/simulations

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