Repairs for our FTC robot

We love our robot, but sometimes stuff breaks, so we 3D print those parts, and other prototypes we think of.

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We would like to enter in the "Repairs you can print" contest as a organisation because we are a First Tech Challenge team.
We are team "RobotX HD" from Hunedoara, Romania, and we participated last year at the National FTC Contest.
During last years, we almost always had broken or missing parts, and because we are in Romania shipping always takes at least two months (sometimes up to three months), and some of those part are very expensive, or it's not worth to buy them because the shipping is more expensive than the pieces themselves. In those circumstances we decided to 3D print everything we can, and it turned out it was totally worth it, because we were on the third place at qualification matches and we participated in the semifinals.
In the "Details" section you will find out more about the pieces we printed for this year's robot and last year's robot, and in the "Files" section you will find the pieces we've printed.

Further modifications:

  1. We will continue to design and print 3D replacements for our robot, because things always break on our robot.
  2. We will try to improve our 3D models for the phone support, for the end caps, and for the strain reliefs to provide better functionality.

Things we have learned while designing and printing those repairs:

  • You almost never need more than 75% infill on a piece, it only increases the printing time without adding too much strenght.
  • Some pieces, like the pieces from the Tetrix kit are very easy to print because you can find them in the virtual kit
  • Other pieces, like the end cap or the double end cap for our 20x20 profiles are very easy to design if you have a calliper and a profile next to your computer, because you can get the exact measurements very fast and easy
  • We learnt that, even if PLA breaks easier than aluminium or steel, doubling the thickness of some parts like the motor mount or the 3D printed gears can help with the strenght of our pieces (PET-G would have helped also, but our 3D printer cannot print in PET-G)
  • Also, all the holes in our robot and in our models are M4, because they are the standard screws in Romania, and Imperial screws are very hard to find and very expensive.

The pieces we have printed/designed:

   1. The double thickness Motor Mount: last year we wanted to mount an extra motor on the robot for the ball elevator, but we've discovered that we don't have any aluminium motor mounts left. Because we didn't have the option to buy another mount (we were 2 weeks before the deadline, shipping from USA to Romania takes 2-3 months), the 3D design team proposed that we print one, with double thickness. After a couple of failed prints (due to bed adhesion), we have printed the motor mount, and it survived all the shocks until now (it's been almost one year since printing). Here is what the piece looks now:

and here is the Motor Mount mounted on our tank drive that we've built this summer:

  2. The double thickness gears: this summer we decided to make a new tank drive chasis. But we discovered that the gears we had were not enough, and even a new set of gears was not enough for both sides, because we needed 2 big 120 teeth gears, and one set contained only one gear of this type. So we decided to 3D print the double thickness gears. The printing took about 30 hours for 6 double thickness 80 teeth gears and 4 double thickness 120 teeth gears. They survived until this day, despite our abuses. Here are the printed gears:

and here is a picture with half of them on the chasis:

  3. The 3D printed omni wheels: this were the objects that took the longest time to print & assemble from our list. One single wheel took about 10 hours of printing and one hour to assemble. After each piece (10 rollers and 2 frames) have been printed, each roller was wrapped in shrink tube, the. But despite the very low cost (actually the antennas were free) materials we have used, the omni wheels did their job and were good enough to help us get on the third place in qualification matches, despite the shrink tube needed to be changed after 3 matches. Here are the omniwheels (after all the matches):

  4. 3D printed strain reliefs: those are some strain reliefs we have printed for our electronics modules. They proved somewhat useful, but because our USBs were not losing their connection we decided not to use them. Here are the strain reliefs:

5. 3D printed battery holders: last year, we had a very odd battery holder mount, that used 2 U-shaped pieces. The mount was holding the battery well, but it was hard to change the battery, thing required after 2 matches. So we decided to design and print some models. Here we have the full battery holder,...

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A zip file that contains a STL and a PRT file for a 3D printed motor mount.

x-zip-compressed - 784.12 kB - 02/19/2018 at 07:17


A zip file that contains the pieces needed for printing an omnwheel. Contains STLs and PRT files for one roller and for half of the omniwheel frame

x-zip-compressed - 1.91 MB - 02/19/2018 at 07:17


A zip file that contains our own phone support for our FTC robot. Includes a STL file and a PRT.

x-zip-compressed - 1.90 MB - 02/19/2018 at 06:38


A zip file that contains a FTC Relic Recovery Relic, split in 4 STLs, each taking about 2 and a half hours to print.

x-zip-compressed - 4.07 MB - 02/19/2018 at 06:24


A zip file that contains 3D models from Thingiverse, that we used to guide our T5 belts in our custom-made tank drive we madel last summer.

x-zip-compressed - 67.39 kB - 02/18/2018 at 17:22


View all 20 files

  • 1 × Robot (because you need to have something to repair)
  • 1 × Broken/Missing component
  • 1 × Sheet of paper and pencil (for perspective drawings if necessary)
  • 1 × Calliper (digital if possible)

  • 1
    The beginning

    For starters, you should detach the broken piece from the robot, or to find the missing piece you want to model / modify (on the internet).

  • 2
    The modeling stage

    Take the broken piece and start to model it, with the measurements from the calliper. Make a 3D model as precise as possible, with all the details you think that are important from the piece. Alternatively, you can modify the part from the internet to be stronger, thicker or things like that.

  • 3

    When printing, high infill is recomended, because the robot parts will be pushed to their limits during the contest.

View all 5 instructions

Enjoy this project?



mircea.fizitec wrote 02/18/2018 at 21:45 point

Impressive! So many 3d printed parts to solve problems!

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