First things first. There are 3 Excavators and each name of the excavator itself corresponds to a certain area on the map either Tunnel 11, The Biodome and Tunnel 6. The power must be turned on for any of the excavators to begin to come out.
At one point while playing, a lady over an intercom will announce that either excavator Omicron, Epsilon, or Pi is going to cause decompression in Tunnel 11, Biodome or Tunnel 6. Omicron is to Tunnel 11, Epsilon is to The Biodome and Pi is to Tunnel 6. Listen very carefully to the lady over the intercom. The last thing that you want is to risk your life trying to hack an excavator you already have hacked.
There is no certain amount of waves that the excavators come out in and there is no certain order, you can get the same excavator 3 times in a row if you're unlucky enough. I will tell you that I have played for this achievement about 10 times and the 1st excavator has always come through rounds 3-8. If you TURN ON THE POWER on round 3, there is a chance the lady will say that an area is about to be breached, it has happened to me 3 times.
When the lady finally does announce that an excavator is going to cause decompression I suggest that one person go for the hacker immediately, usually its the person with the best weapon so that they can protect themselves. If you need a place to camp I would suggest the right and left sides of the pyramid, they are easy to cover and it is really close to the hacker room. In order to get the achievement, the SAME (I cant stress that enough) person has to hack all three of the consoles at the start room, the consoles are pretty obvious, when activated they are green and flashing, simply walk up to them and hold x until the hack is done. Even though the same person has to hack all 3 consoles, all present players get the achievement when the last console is hacked.
NOTE: Do not shoot explosives in any of the rooms that the hacker can be found in and don't shoot any explosives in the start room, that includes grenades. You may be wondering why, well its because if you accidentally blow out a window, the room will no longer have air in it, therefore you cant have the hacker in those rooms because you have no space suit when having the hacker and you cant breath and you'll slowly lose oxygen until you go down.
SUGGESTIONS: I suggest getting the zap gun and pack a punching it, the wave gun comes in handy in a plethora of situations, it is basically like having a wunderwaffe except with 28 shots in it, not to mention the 120 something electricity bullets you have. I would also suggest that you get Juggernaut, Stamina-up, Quick revive and Sleight of Hand, they are the most helpful out of all of the perks.
CAUTION: The astronaut will take your most recent perk from you if you get caught by him, along with being teleported away from your teammates, so try not to get caught by him, a good way to take him out is by shotguns or quantum grenades.
GERSH: Gersh devices also come in handy when you need to grab a max ammo and there are too many zombies or just when you need to revive someone who is amidst a mass of zombies. May I also say that gersh devices will transport you to a different part of the map if you walk into the black hole where all the zombies die at.
MORE SUGGESTIONS: If I were to make any more suggestions it would be that if you are in the position where you need to hack the last excavator for the achievement and you don't think you'll make it due to it being a high wave like wave 20 and up, send ALL players up to the hacker and run as fast as you can to the earth teleporter. If everyone is running fast enough, the person with the hacker should'nt go down due to lack of air and you should teleport to earth. Step back on the teleporter as soon as it will let you and go back to the moon. That way when you come back to the moon, there will be no zombies in the map for about 10 seconds and you will be in the start room and can hack the last excavator without worries of hordes of zombies coming behind you.
HACKER TRICKS: A couple other tricks that you may not know is that you can hack 500 points at a time to other players if they do not have many points but are in desperate need of a weapon or perk. Simply pick up the hacker and walk up to the player you wish to transfer points to and hold x until it gives your points to them, you need a minimum of 500 points or you cant transfer. Another thing is you can hack the random box 2 times every time it moves. Simply pay for a weapon and when the roulette stops take out the hacker and hack the weapon for 600 more points added on to the 950 you already spent, it will cycle through another roulette and give you a different gun, if you in fact hack that second weapon it will give you 950 points back and make the current roulette weapon available for any of the current players in the game to pick up.
NOTE: I will give an example. I BUY A GUN FROM RANDOM BOX (-950) IT IS A FAMAS. TAKE OUT HACK TOOL AND HACK THE FAMAS LIKE YOU HACK EVERYTHING ELSE (-600 MORE) WHICH IS (-1550 TOTAL). NOW THE ROULETTE CYCLES AGAIN. IT IS A RAY GUN THIS TIME, HACK THE RAY GUN. NOW YOU WILL GET 950 POINTS BACK (ONLY LOSING 600) AND MY TEAMMATES CAN PICK UP THE RAY GUN IF THEY WANTED. YOU CAN DO THIS WHOLE PROCESS TWICE FOR EACH TIME THE BOX MOVES.
Last but not least you can hack the weapon outlines on the walls. What this does is it makes regular weapon ammo 4500, or somewhere around there, and pack a punched ammo really cheap. Although hacking a weapon on a wall costs quite a few points, its up to you to decide if its worth those points. For example the steakout pack a punched ammo would be 750 points. The pack a punched steakout is a pretty good weapon up until round 20. Since it seems to be unclear, you cannot simply hack a weapon outline and then buy pack a punched ammo. Before you can actually buy the ammo off of the wall, you have to pack a punch (in this example the steakout) first on earth. Basically saying you cannot buy pack a punched ammo without having the pack a punched gun first.
If there is anything you think I forgot or anything that is unclear to you please leave a comment and I will fix it or make it more clear to you.