ROBBOB Robot SG90 Servo Horns (Arms)

thingiverse

MOBBOB is really an interesting project and I appreciate the kindness of Kevin Chan, who opened and shared the design source code to the public. These days, I've tried to assemble this cute robot, but I don't want to damage SG90 parts due to some accidents. So, I started to print some spares, include the servo horns (arms). The horns are used for SG90 servo motor, which is created by FreeCAD. So, if you have some knowledge in using FreeCAD, you can modify the position or diameter of holes by yourself. Since the flexibility of filament are different, as I've tried two different filament material, and I noticed one of the filament with the same R2.25 cannot be mounted onto SG90 servo. So, I printed another one with R2.3. If the above two radius are not fit to your own 3D printed horns, you can try to adjust the radius by yourself. The method is finding the object Axis from Fusion->Ring Holder w Gear -> Horn Ring Holder -> Axis. Double click the mouse to open the 2D drawing. Then double click on the radius of 2.3mm or 2.25mm to modify the inner radius. No matter you expand or reduce the radius, it may cause the gear too thin or too thick. So, you need to modify the module of gear, too. Then, find out the object InvoluteGear from Fusion->Inner Gear->InvoluteGear, double click mouse, and adjust the number of "Modulers" in the 3rd digit behind point. Don't adjust too much. And after the value is changed, the position of gear will be changed (maybe a bug of FreeCad). You need to modify the position of gear by select the InvoluteGear again (single click mouse), and adjust the "Placement, with Z:2mm, Angle:9 degree, and leave the others as it is. Or if you may like to expand or reduce the width of horns, you can find out the object "sHorn". Double click it to open the 2D drawing screen, simply adjust the distance of the outer virtual circle from the center (same, double click the number of distance, and adjust the value). Then, press "Update" button on the left side. And you will see the width is changed in the 3D drawing. The same method to adjust the position drill hole is the same. Find out the sketch of the hole and adjust the distance. Finally, select the object "Fusion" and then select the menu File -> Export, then you can get a new STL file.