3D Printed RC Servo Case (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.

A project I'm working on required that I reduce the overall size of a sub-assembly. I've contemplated modeling and printing RC servo cases in the past, access to an Object printer presented an opportunity to experiment.

I'm using Hitec's HS-645MG servo. I've included my file set at the end of the instructable.

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Step 1: Servo Case Modifications

Here's a few images of the original servo case next to the modified servo case. I've noted in the images the changes I've made.

Step 2: Removing the Servo Horn and Servo Case Back

Start by removing the servo horn, then remove the four fasteners that hold the servo together.

Step 3: Removing the Top Cap, Gear Train, and Bearings

Gently pull the top cap away from the body. The gear train may fall out as you do this. I took a picture of it still attached to the servo body for reference.

I've also included a shot of all the parts on a post it, make sure not to lose any of them.

Next, pull the bearing off the servo body and push the bearing out of the servo top cap.

Step 4: Removing the Potentiometer and Motor

The potentiometer is held in place with a small screw. Remove the screw and gently push the potentiometer out of the servo body.

The motor is a tight fit into the servo body, there may also be a dab of adhesive that you'll need to scrape off with the tip of a screw driver. Don't pull on the motor wires unless you want to solder them back on later.

Step 5: Inserting the Motor and the Potentiometer

Reverse the process, start by inserting the motor. It should be a press fit, and a dab of glue.

Step 6: Attaching Servo Back Cap and Bearing

You'll notice that I also changed the orientation of the servo cable, instead of exiting on to the side it exits to the bottom. 

Press the bearing on the servo body and into the servo cap.

Step 7: Reassemble Gear Train and Attach Top Cap

Reassemble gear train. Note the orientation of the servo limit post it should look like the picture.

Wiggle the servo top cap onto the servo, you shouldn't have to force it. If the gear train isn't reassembled correctly the top cap will not fit.

Step 8: Insert and Tighten the Servo Case Screws

Slide the case screws into their holes and tighten them up.

I like to test the servo at this point if it doesn't move smoothly I double check the gear train assembly.

Step 9: Attach New Servo Horn

I 3D printed a servo horn that would allow me to mount something at 90 degrees to the splined shaft.

Step 10: Removing the Servo Horn (HS-65MG)

In my design I've attached a smaller servo to the back of the larger servo. Here we remove the stock servo horn from the HS65MG.

Step 11: Mounting the New Servo Horn and Attaching the Smaller Servo.

Push the new servo horn on the smaller servo and then attach the smaller servo to the larger servo.

Step 12: The Complete Assembly

Here are a few picture of the assembly.

Step 13: The Files

I've attached the file I printed on an Objet 500. Even if you don't plan on using the HS-645MG they are useful in understanding servos.

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    16 Discussions


    5 years ago on Introduction

    Good work and nice Instructable. Great pictures and step by step explanation.


    Reply 5 years ago on Introduction

    @hunter9t9, I used Pro/Engineer now called Creo. Would you like copies of the native files or step files? I realize STLs are not the best for modifying parts.


    Reply 4 years ago on Introduction

    whatever is easist for you to send i have multple 3d design programs im very good at altering exsisting objects jut not very good at starting from scratch


    4 years ago

    No I am looking for a 3d printed 9g servo case like the one you did for this larger servo

    2 replies

    Reply 4 years ago

    whirl55, got it. I've haven't modeled any servos that small.


    4 years ago

    As I am not good enough at 3d modeling to make it myself


    Reply 4 years ago on Introduction

    whirl55, I designed a pan tilt system with 9g servos for ldevendorf, see her instructable, https://www.instructables.com/id/Become-Your-Own-3D-Printer/, is that what you have in mind?