ROBBOB Robot SG90 Servo Horns (Arms)

thingiverse

MOBBOB is an exceptionally intriguing project that I appreciate for the kindness displayed by Kevin Chan, who opened and shared the design source code with the public. Lately, I've attempted to assemble this adorable robot but want to avoid damaging SG90 parts due to some accidents. So, I began printing some spares, including the servo horns (arms). These horns are used for SG90 servo motors, created by FreeCAD. If you have knowledge in using FreeCAD, you can modify the position or diameter of holes yourself. Since the flexibility of filament varies as I've tried two different materials and noticed one with the same R2.25 cannot be mounted onto SG90 servo, I printed another one with R2.3. If the above two radii don't fit your own 3D-printed horns, you can try adjusting the radius yourself. To do this, find 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 2.3mm or 2.25mm radius to modify the inner radius. When modifying the radius, be aware that it may cause the gear to become too thin or thick, so you'll need to adjust the module of the gear as well. Next, find the object InvoluteGear from Fusion -> Inner Gear -> InvoluteGear and double-click the mouse. Adjust the number of "Modulers" in the third digit behind the decimal point carefully, as adjusting too much may change the position of the gear (which might be a bug in FreeCad). You'll need to adjust the position of the gear by selecting the InvoluteGear again and adjusting the placement, with Z:2mm, Angle:9 degree, leaving the others unchanged. Alternatively, if you'd like to expand or reduce the width of the horns, find the object "sHorn" and double-click it to open the 2D drawing screen. Simply adjust the distance of the outer virtual circle from the center by double-clicking on the number and adjusting the value, then press the "Update" button on the left side. You'll see the width change in the 3D drawing, and the same method applies to adjusting the position of drill holes - find the sketch of the hole and adjust the distance. Finally, select the object "Fusion" and go to File -> Export to get a new STL file.