When drawing robotic parts, how do you keep the shapes organic but also keeping the feeling that they're made of metal? :o
Probably the balance between natural and unnatural shapes!
Like this:
It is pretty much a mix of human anatomy and the sharp edges and gaps commonly found in mechanic joints. In Beatrix's case, her arms are not jointed in the same way a human arm is, however they function as one. They mimic an organic form in 80% of sillhouette.
Aside from color and lighting variations, there's a trick using lineart. Notice that bodies have wrinkles where the skin twists and stretches to accommodate the muscle, tendons and bones underneath. Mechanisms have "wrinkles" of their own, except they show that parts are detachable and far more rigid in comparison. There's also a symmetrical look to them not usually found in organic matter!
