So this is 3d printed cyclo reducer. I was trying to design cycloidal or harmonic reducer that can be 3d printed , so it can be used in precise robotic arm. But this reducer is basically just proof of concept , it has way to much wobble ,there is too much friction between cyclo disc and "roler pins"( they are just extruded plastic cams), and is prone to getting jammed.

Will probably make some revisions to this drive but i think harmonic reducer would work better when 3d printed.

Step 1: How It Works

Yellow part is cyclo disk/gear

Green part is hight speed input shaft

Purple part is low speed output shaft

White part is in our case , a case with roller pins

So when we spin input shaft it is offset by some amount , in our case 2.5 mm.On that offset shaft we place a bearing and on the bearing cyclo disk.Center of our case with roller pins is concentric with low speed output shaft but is not concentric with cyclo disk.There is 10 teeth on cyclo disk and 11 roller pins on our case. That gives us reduction of 10:1.When high speed input shaft spins it produces eccentric motion . For one rotation of high speed shaft, disk will move one of its teeth from one roller pin to another (as you can see in the gif).Holes in disk are used to convert eccentric motion to normal rotation for output shaft.Each pin of output shaft is always tangent to its related hole on cyclo disk.That forces it to rotate.

Step 2: Not Printed Parts

any nema 17 stepper motor
4x M3x10mm
4x M3x25mm
4x M3 nuts
1x 35x47x7mm 6807ZZ ball bearing
1x 17x23x4 6703ZZ ball bearing

On top of that you will need arduino , stepper motor driver ,power supply ,wires...

Step 3: 3D Printed Parts

Print all parts with 0.2 layer height

You wil need one of each parts.

On picture marked with numbers:

1.eccentric input shaft

2.low speed output shaft

3.case with roller pins

4.top cover

5.cyclo gear

After you printed all parts make shure there are no blobs or strings on cyclo gear and inside of case.I found out that even a tiny blob can jam the drive, so make shure everything is smooth.

Step 4: Assembly

Screw your stepper motor in case with roller pins, you will maybe need to drill holes with 3mm drill bit.Screws used are M3 x 10mm.

Step 5: Assembly

Place eccentric input shaft on shaft of stepper motor.It should fit tightly ,but if it does not you can add set screw in hole that is already there.

Step 6: Assembly

Place 17x23x4 6703ZZ ball bearing inside cyclo gear , if it is lose use super glue to secure it in place.

Step 7: Assembly

Place cyclo gear on escentric shaft ,Now place three fingers in those holes and try to spin it . If you cant spin it easily you will need to sand any of touching surfaces until you can .

Step 8:

Place 35x47x7mm 6807zz ball bearing inside top cover, again if it is lose use little bit of super glue.

Now place low speed output shaft in ball bearing . It should be tight fit. Make shure that pins on low speed output shaft have no blobs and strings.After that place top cover on lower case and secure them with 25mm screws and nuts,Again this is proof of concept. If it is not working at first sand it a bit more . You will not be able to use this for anything too usefull unless highly modified

Step 9: Make It Spin!

connect your stepper to arduino and use any code to spin it .

Here is an example:

const int stepPin = 3; <br>const int dirPin = 4; 
 
void setup() {
 
  pinMode(stepPin,OUTPUT); 
  pinMode(dirPin,OUTPUT);
}
void loop() {
  digitalWrite(dirPin,HIGH);
  digitalWrite(dirPin,HIGH); 
  for(int x = 0; x < 5000; x++) {
    digitalWrite(stepPin,HIGH);
    delayMicroseconds(500);
    digitalWrite(stepPin,LOW);
    delayMicroseconds(500);
  }}