3D Printing RC Servo Splines (Hitec HS-645MG)


Introduction: 3D Printing RC Servo Splines (Hitec HS-645MG)

About: I am organic computer running poetic software. Interested in overlaps and antipodes. Fascinated by how metaphors shape our thoughts and objects. I've been wondering when you'd show up and send me a note.

In prototyping mechanisms I find that I need to print parts that include RC servo spline geometry. A google search didn't point me to useful geometry, at least not when I wrote this.

Before you get too excited you'll need access to a high resolution 3D printer, I used the an Objet 500. The good news is service bureaus are popping-up everywhere and small parts are quite affordable to print.

I tend to use Hitec servos with ball bearings and metal gears for most of my mechanisms. They cost a bit more and are worth it. Stripping plastic gears on a newly assembled project feels almost the same as finding out someone ate your last piece of chocolate.

Step 1: Printing and Testing for Proper Fit

Sadly, not all 3D printers are alike. I've even found that different materials, on the same printer, produce different results. Given the size of the RC servo spline you'll want to run a few test parts and check the fit.

I've included the test parts that I printed in a zip file. Servo Spline 000.stl worked perfectly for me. 001, 002, and 003 are .001, .002, and .003 of an inch oversized.

Remember to clean out all the support material before testing. I've found that remaining support material can give the impression of a tight fit. Assemble and dissemble each test part a few times as well.

Step 2: Creating Your Part

Here's an example part incorporating the spline geometry.

I've also included the solid part files to work with.



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    8 Discussions

    Is it possible to upload the original files? (or step files) That would be even more helpful and awesome.

    2 replies

    matt3333, I've updated the zip file to include step files and the original Creo/Pro Engineer file.


    2 years ago

    I successfully printed it many times on my Ultimaker2 using a 0.4mm nozzle, but both PLA and ABS ripped at the spline teeth every time. The Hitec horns are made of nylon. Is nylon less breakable or do you think I printed it incorrectly? I have been 3D printing indentations to incorporate genuine hitec horns by screwing them to my prints. Now I am using 9380TH servos, lifting 36 kg and even the nylon teeth are ripping. PLA and ABS don't seem to stand a chance, unless you know something I don't. Are you rotating tiny light objects or are you able to hold heavier objects and move them back and forth quickly? Which plastic do you use and nozzle size?

    1 reply

    zxen, for loads that heavy I use aluminum servo horns, like these http://bit.ly/1UfyOf1. That said, depending on the position of the load, and rate of change, you may be asking too much from the 9380TH. Servo manufacturers design the servo horn to be the weak link when overloaded. If you use a aluminum horn, and the servo is underpowered, you'll toast the mosfets in the servo. Post an image of the mechanism so I have a better idea of what you're up to.

    Downloaded Sketchup 2015. Downloaded STL Sketchup extension. Downloaded your zip folder. Unzipped your zip folder. Imported Servo Spline 000.stl. Displayed vertically at x=0, y=0, z=0. Exported as both STL and DAE file. Loaded files into Cura. Both files appeared as two tiny circles. How does this work? I just need the female spline for Hitec 645MGfor a shoe I'm making.Thanks for providing this, but using the Ultimaker 2 and all this awful software is a counter-intuitive, incompatible nightmare.How can I use your female spline to create my own servo horn please?

    1 reply

    zxen, I modeled the servo spline in millimeters, that said I don't think the Ultramaker 2 has the resolution to print the spline.

    Can you import and see the stl into Meshmixer (free program)? I would avoid using sketch-up for modeling tiny things, it's more of a architectural modeler. Give Fusion 360 a try, if you're a student it's free. If not, they have a start-up option that is also free.