This post should detail some of the most stumbling blocks in building and using any of the LittleBots.
Bluetooth or USB not connecting
With the LittleArm Big, and all of our robots, the Bluetooth and the USB cord cannot be connected simultaneously. Since they both use the Serial port of the Arduino their signals effectively cancel each other. If you wish to control the arm with Bluetooth ensure that it is not connected via USB and vice versa.
Driver Issue with Arduino
The Atmega chips used in all of our robots are Arduino Clones, as such a certain driver error can arise when attempting to flash them using the Arduino IDE, if it is not appropriately updated. This is easily remedied by following this instructable about adding the necessary drivers to your computer.
3D printing can occasionally leave a little residue behind. This can sometimes be due to poor retraction, or intentional in order to gain something somewhere else in the design. This residue can sometime block or impede insertion of components. If you find/print a piece with this slight defect simply use some needle-nosed pliers, a razor, or a small file to pluck or smooth out the problem. This is a very minor side effect and is easy to remedy.
3D Printing the Arm
All 3D printed parts for the LittleBots are designed to be Sliced with CURA. Using other softwares can sometimes result in incorrect slicing of the parts. While we work to make sure that our files are compatible with all 3D printing slicers we do not always succeed and are constantly updating the files to extend their compatibility.
One last consideration. We designed the LittleBots to be printed with our printers. That is the only reference that we have. Since many of the kits are "snap together" tolerances are fairly tight for 3D printing. Many desktop 3D printers are not tuned or maintained well enough to hit our tolerances. Generally this can be fixed by scaling parts to 101% of their original size. This typically increases the margins enough for servos to slide into to lower-tolerance slots, without causing other assembly difficulties.
If you have trouble with one of your LittleBots please let us know and we will work to help you as much as possible.