Sprockets: A Little Robot — Alexander Key

A pint-size robot with a big spirit goes on an interstellar adventure

Running low on metal, an assembly line spits out something unusual: a peculiar little robot, no bigger than a boy. His name is Sprockets, and though he is small, he has the most powerful electronic brain on Earth. “Destroy him!” cries the foreman, but Sprockets escapes. He runs through the moonlit city, pushing his little body as hard as he can until rain starts to fall -- and he begins to rust. But Sprockets is rescued just in time by Jim and his father, Dr. Bailey -- a brilliant inventor who sometimes has trouble with fractions. Luckily for him, there is no finer tabulator than Sprockets.
 
They adopt this little robot as their own, and soon set off for another world -- where Sprockets will be charged with saving the universe and learning what it is to be alive.

Sprockets is the 1st book in the Sprockets series, which also includes Rivets and Sprockets and Bolts.