In trying to earn the Mecha-Done achievement, this is part of the Junkyard Architect portion and you need to do it in the "Hard Mode" which can be very frustrating if there are tons of other players out there and they blast your "Irradiated Elemental" (green golems that come after the wave of slimes) before you can turn them into Unstable Irradiated Elementals (they become red coloured versions of the green golems). I just got lucky as a lower level player was there trying to get their own achiev and they didn't kill the mobs I needed to convert.
I would clarify something as the write up on doing this makes it sound like you have to do the "Supercollider" quest 4 times. What is meant is that I believe it is usually the fourth item that becomes available to make, not that you have to do the quest that Rocket-Chief Fuselage (Toys for Destruction) offers 4x. I do not have the Boltspitter weapon made yet, so have not earned that achiev (Armed for Action) and today I did the Supercollider and after a few attempts at doing the Reclamation Rig, managed to have a good player out there who let me convert all the 20 Elementals to get the Hard Mode completed and earned my Irradiated Box of Assorted Parts. Thanks to that individual for their understanding :)
Hope this helps you complete your adventure to get the Mecha-Done achiev.