Fabricator - Borderlands 3 Farming Guides
Location: Jack's Secret
Part of: Jack's Wild Story Mission (DLC)
Drops: ION CANNON (Vladof RPG)
Fabricator is one of the bosses you fight during the Jack's Wild Story Mission which is part of the Moxxi's Heist DLC storyline. You can find the Fabricator boss at the end of the Jack's Secret zone; the closest fast travel terminal is at the start of the zone which means you'll have to run through the entirety of the zone to get to this boss.
Tip: For running through this zone and other zones like it I strongly recommend you turn down/off your Mayhem difficulty then turn it back up when you reach the boss at the end. When you change Mayhem difficulty and it resets the zone, you're put at the same location you would be if you quit and entered again. This means that if you grab the save/respawn terminal just before the Fabricator boss you'll be placed right back here when the zone resets.
As far as loot goes, ION CANNON (Vladof RPG) is the only item on Fabricator's dedicated loot list. This item is also unique to the Fabricator and doesn't drop (or is extremely rare) elsewhere in the world, if you're looking to get an ION CANNON you'll have to farm this boss for it.