ok as you have experiance then you can start thinking about arms moving parts. where to get motors, how much torque must they have, what power consumption, what voltage. Also about the control cirquit. where to get H-bridges to control your motors, how powerful must they be. after you have made block shematic about all what you need, then you can start constructing more acurate shematic.
but before you start making the shematic, you should build that arm. al the mechanical components, motors etc. so you know if you have to add or discard some things, you didn't think before. When you are constructing an industrial arm, i suggest make it from metal (like alluminum).
you can also look other peoples work over the internet. you can find them through google.