Where do you find all robotic parts?

ACT I

Widow's Veil in Crow's Pass

You have to light up all fires and than backtrack to locked door

ACT II

Tower of Moon

It's small arena you have to hit four gongs for secret door to open

Brood Hive

The area for the side quest [Missing Zeraphi] where you have to clear up all eggs. This one does not have any puzzle. You just have to look very carefully

ACT III

Abadoned [cursed] Windmill

You have to read all diaries and find four skeletons attached to wooden beams by axes, when you click on them you will hear ghostly wail and one torch on small graveyard lights up. When all four are "saved" door will open. You have to do this before teleporting to the boss, otherwise you have to enter that area again.

Cacklespit Realm

Destroy all tree stumps, you should open hidden passage. But on my 2nd char its bugged, so maybe you will need to travel back to 2nd city to rebuild new map if that happens to you as well. But when all tree stumps are cut down, you will hear distinct sound. Than go around edges of map on one place logs will appear and create you way for last robot part.

That should be all pieces - now you need to obtain power source from Main quest so its unmissable.

--Part in Act 1 is

Side quest: Little Lost Ones (light all the Brazier's)

Dungeon: Widow's Veil

Region: Crows Pass

Part located: on the left side of the exit area a passage will open.

--Parts in Act 2 are

-#1

Side quest: (Hit all the Gongs around the room.)

Dungeon: Tower of the Moon

Region: Ossean Wastes(south end of town)

Part Location: to the right side of the exit area.

-#2

Side quest: Shadow of Skara

Dungeon: the Blood Hive (second floor)

Region: Salt Barrens (north side of town, second zone up)

Part Location: right side of exit break all the eggs.

--Act 3 Parts are

-#1

Quest related: This is part of the main quest.

Dungeon: Abadoned [cursed] Windmill.

Region: Blightbogs (south exit from town)

Part location: Read all diaries and release the 4 skeletons attached to wooden beams by axes. When all is done a door will open on the west side of the main map area. You have to collect this before teleporting to the boss, otherwise you have to enter thhe area again.

-#2

Quest Related: Second side quest in the quests given by/for Cacklespit

Dungeon: Cacklespit Realm

Region: Sundered Battlefield (north exit from town, second zone up)

Part Location: Destory all tree stumps in the zone, You will trigger a log bridge to be created in the center of the map leading to the north.

--Final Part.

Quest Related: Main Quest Last quest befor you unlock Act4.

Part Location: obtain power source as part of the Main quest. If you have already turned the powersource in then just go talk to the NPC and the robot will be constructed.

Your now Done collecting parts, 5 in total you should see them in your "Q"uest log on the tab for the robot quest. The Turn in NPC is located in the act 3 town.

Enjoy your rewards

I found one (the head) in Cracklespit´s Realm in act 3, which you can enter by doing his/her (?) sidequest(s).

I found one in the Swarm Temples... in the Salt Barrens Act 3 if I am correct.

Which act is the Temple of the Moon since I very intrested in this robot? :)