Release of compact, 3d printed swerve drive from frc team 3737

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After two years of testing and development, team 3737 is pleased to release our latest 3D printed swerve drive. Our goal was to enable us (and any team) to manufacture a relatively low cost but competition capable swerve drive using a quality FDM 3D printer. To this end, we have provided with the CAD model, step-by-step assembly instructions, full BOM, complete print settings and a speed calculator for various gearing and drive motors. The swerve assembly is designed to bolt to the underside of a 3030 T-slot chassis (see 3737’s robot release of BB Mantis). This lightweight but strong chassis design also provides immense versatility with infinitely variable bolting positions on all faces.

The base design uses NEO drive and NEO550 steer motors. However, all current FRC legal brushless drive motors are possible (serrated shaft prints are provided).

Note that this assembly uses the ‘standard’ 4” x 1.5” Aluminum billet wheel. However, we have separately developed a fully interchangeable, FDM 3D printable, TPU ‘suspension tread’ wheel assembly (see end of this post for link).

Some highlights are:

  • Fully 3D printed design in PETG (excl. bearings, most gears and fasteners)
  • Competition tested
  • Relatively low cost (vs metal framed swerve drive)
  • Various drive motors possible
  • Five available drive gear ratios
  • Drive speed gearing can be changed by 2 or 3 steps with removal of two screws
  • Calculated max free speed:
    • NEO: 15.41 ft/sec
    • NEO Vortex: 18.42 ft/sec
    • Falcon 500: 17.32 ft/sec
    • Kraken X60: 16.29 ft/sec
  • Full assembly size (with SparkMax controllers):
    • 5.35”wide (136 mm)
    • 7.02” long (178 mm)
    • 9.11” high (231 mm)
  • Swerve assembly (incl. Aluminum wheel & tread) weights:
    • W/O motors, UP gearboxes & SM controllers: 2.5 lbs (1.136 kg)
    • With motors, UP gearboxes, w/o SM controllers: 4.68 lbs (2.121 kg)
    • With SM controllers: 5.24 lbs (2.379 kg)
  • 4” dia. x 1.5” wide wheel with center 2.75” from edges of chassis.
  • Enclosed design to virtually eliminate pickup of dust and carpet
  • Virtually zero maintenance
  • Fully manufacturable in-house
  • Brushless motors
  • Drive motor assembly is removable with two screws
  • Steer motor & gearbox assembly is removable with two screws
  • Swerve assembly is removable from chassis with four screws
  • Encoder is removable without disassembling the swerve drive
  • Simple wire management
  • Integrated motor controllers with full status light visibility and plug accessibility
  • Manufacturable in any available filament colors (including your teams’ colors)
  • CAD models of seven printable tools and jigs are supplied to simplify manufacture

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Comments and questions are welcome.
If you use it, we’d love to hear and be credited.

https://drive.google.com/drive/folders/1ZQC3a7gMxewyTUdJOlmf7fr8g3cw6-PB?usp=sharing

Suspension treads link:

27 Likes

Nice work! I assume this is for development and testing only? Otherwise I’m not sure I would trust a 3D printed thrust bearing with plastic races to hold up a robot in competition.

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Thanks! We have been using 1/4" Delrin balls in a PETG printed V grooves for 2 years (in separate swerve drives of course) during both on and off season competitions and have had no problems. This year, our drivers managed to get some ‘air-time’ off the charge station with no ill effects. We will be using this design on our competition bot in a few weeks (assuming the terrain is suitable for swerve).
I just did the calculation - in static mode, each contact point on each Delrin ball takes just 2.8oz for a full weight robot.

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Nope, they’ve used these in competition. I was discussing them with one of their mentors during an off-season event this year, so I’ve seen the units directly on their robot. They really do stand up to hard use and are completely reliable.

Derek, this is really fantastic work your team has done to develop these. Congratulations!

2 Likes

Do you have photos of the swerve modules on a robot and off it?

4 Likes

These look great. Low part count and built robustly. Would be nice to see some kind of reinforcement option and steel bearing for longer term use but I think it’s great as is for a low budget option. EDIT: nevermind, I see you’ve run these in season already. Wow!

Glad to see the as5600 get some love. Do beware that the magnets that ship with those often aren’t diametric magnets at all. Also, did you need to pull R4 off the PCB before using it? I wasn’t able to get an analog output before doing that or it would be stuck in programming mode. You can use pliers to remove.

This is the basis of our test bot, Mr. Anderson, with one swerve removed (and untidy wiring).

One assembly (w/o encoder, SM cable clips and wheel dust guards)

5 Likes

Thanks for the compliments!
Regarding life, we did a full year of on and off season competitions, plus a STEM event (Wings over Wayne) where we played every other match all day for three days. We are confident that they will last another year of demos to sponsors etc.
We found the same issue as you with the magnets! So, in the BOM we provide a source for the exact match, diametric type.
We have not pulled R4 (or the other resistor) but our programmers know the exact details on reading.

1 Like

You do not have to remove the R4 resistor. That method works but you can do it an easier way. The GPO pin on the board which is misspelled, it is called the PGO pin according the AS5600 documentation. If you connect the GPO (or PGO) pin to 5 volts it puts the chip in analog mode.

Very cool, my team built our own swerves once… I think its still in our storage closet. This however, will be a tremendous help for new teams!

Thank you! This was exactly our goal- to make swerve accessible to any team, especially those wanting to try swerve for the first time.

IMPORTANT UPDATE: Absolute encoder wiring. The assembly instructions we provide that refer to the encoder wiring omit the link wire (preventing the encoder from working).

However, while building our current swerves, we decided that removing R4 was the most elegant solution. This has been tested and is working. (Grab the sides of R4 with fine tip cutters and oscillate a little to crack the resistor. Dab the two solder blobs with a soldering iron to neaten them and ensure no connection). In summary: Follow the instructions provided AND remove R4.