The Foundry Freaks are located in The Pitted Stain Ripper Drill Site around Idolator's Noose in the Fadefields.
In order to make the Foundry Freaks and Frank the Furnace spawn, you will first need to kill several waves of Rippers.
How to Beat
FIGHT TLDR
Make sure to keep a safe distance and try to kite the Foundry Freaks trio as they're mostly melee.
Pick one of the bosses to focus on at all times as it'll be easier to kill them off one by one.
Mechanics
All 3 Foundry Freaks first healthbar is Armor that is weak to 🟢Corrosive and ❄️Cryodamage. Their second healthbar is Flesh that is weak to 🔥Incendiary damage.
1. Hank the Welder
What Happens:Hank the Welder is a melee focused enemy who will leap towards you to close the gap. Once up close, he'll fire a flamethrower to deal damage and set you on fire.
What to do:Keep kiting the boss. The flamethrower is low range and easily avoided if you keep moving. His leap is very telegraphed and can be dodged away from.
Keep your distance!
2. Sal the Engineer
What Happens: Sal the Engineer is the hybrid melee/ranged boss of the trio. Like Hank, Sal will launch towards you to close the gap, this time spinning and burning the ground around and below him. His ranged attack comes in the form of a fireball attack to mix things up.
What to do: Continue to kite Sal and use terrain to line of sight the fireballs.
Sal's spins are dangerous!
3. Frank the Furnace (Leader)
What Happens:Frank the Furnace is the ranged and arguably most dangerous member of the trio. He will launch rockets, fireballs, and waves of lava at you leaving damaging fire puddles on the ground.
What to do: It's hard to keep tabs on Frank's artillery-like support while Hank and Sal are chasing you down, so it's recommended to focus on those first. Fortunately, the best way to dodge Frank's moves is to keep moving which you will already be doing while kiting the other two.
Avoid fire puddles that are left on the ground, stay behind terrain, and jump over lava waves he sends your way!
Frank's bombs the spawn lava puddles.
The lava waves can be hopped over!
Tips & Tricks
Use 🔥Incendiary weapons to kill off the Rippers on The Pitted Stain Ripper Drill Site as they're mostly just Flesh.
Leave some Ripper adds alive to use for Second Wind.
Sal the Engineer and Hank the Welder are most likely to chase you down in the battlefield - which is why it is recommended to kill them first and Frank the Furnace last.