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.