Dead Space 3

Load up Chapter 13 and as you go around the corner you will see a spot to unload your scavenger bot. Save and Quit straight after doing this and go back into the game. The same spot where you put the last bot will still be active. Just past this spot is a room with a bench. Wait for all of your bots to come to the bench and rinse and repeat. This is also a really good way farm for resources!

You unlock the Scavenger Bots progressing through the story.

To equip a Scavenger Bot press the up arrow BMD.
Then hold LT and you have a scanner that will follow the indicator to find a point of resources, directing you to the strange sound.
When you arrive at the point of contact scanner Scavenger Bot will blue circles in the middle deploy Scavenger Bot pressing RT.
Repeated the process 15 times.

PS: Sorry for my English

I found a spot that works really well in Chapter 12.

In the room with the giant alien carcass, there's a Bench right near an elevator that goes up to the catwalks above that have the harpoons you use to open the carcass. If you're facing the Bench, the door you want is just to your right. It will lead you to a small outside space with a Resource Area on your left literally a few yards from the door. Once you place the scavenger bot go back through the door and open the other side so it closes behind you.

After that just turn around and go back outside again. The area reloads and the Resource Area will be reset and you can place another bot. This eliminates having to quit out of the game and saves a lot of time.

Also as a bonus, just to the left of the spot where you set down the bots is a post/pillar with an unbreakable grey cube box next to it. Go over and look behind it. Initially there's an artifact here, but in subsequent passes, the game will drop in another random pick-up item: ammo clips, stasis pods, crafting materials, etc. However, it doesn't replace the item if you fail to pick it up and continues to add a new item each time you pass through this area. So keep checking this spot for additional resources.

I've made a video showing what I've described above. Hope it helps!:

GnarlyDannyBoy mentioned a useful location Chapter 13. I'll briefly describe what's said above. Right when you start, you'll find a place to unload your bot. You can save and quit, restart the chapter and place it there again.

If you feel like using any other location, you can, but that chapter is the easiest one to use.
You can get this achievement the fastest if you have the maximum of 3 scavenger bots. Some people have said you can have 5 with DLC or something like that. You can look it up or read the comments on other guides if you want to try that.

If you've placed scavenger bots throughout the story and collected them, you'll likely have some progress towards this achievement. You can check it by pressing , selecting achievements and scrolling down to "Metal Detector". You need to equip the bot, then walk towards the direction where it points you. If you're in Chapter 13's beginning like GnarlyDannyBoy mentioned, you'll just have to walk a few feet behind you. When the screen has a flashing full blue circle on it, you can deploy your bot. You have successfully struck a resource area.

If you follow the method above, you can deploy all 3 bots and play another mission or do something else to pass the time until they all come back to the Bench. Repeat this process until the achievement's tracker reaches 15/15. Once you reach this value, you'll get the achievement.

Here are the locations of each scavenger bot in the game:

Chapter 4: "History's Ember":
You'll find this naturally through the story as you climb down a ladder.
Chapter 8: "Off the Grid":
After a cutscene of the Hydra, you should keep walking forward past a couple large pipes and a ladder until you reach a couple metal barriers in a camp like area. If you walk through the path they form, you will come to a room. You'll find the bot next to an audio log in the room. The audio log is hard to miss. It shines bright blue in the darkness. You're required to go here to progress the story.
Chapter 13: "Off the Grid":
After climbing a wall with necromorphs, you'll come to a room where you'll be ambushed my wasters, exploders and some other enemies. After dealing with them, follow the objective until you see a fork in the path. Take the path to the left to find a SCAF artifact and the bot you're looking for. The bot itself will be in the far corner of the room. You'll see four closely packed little lights on the ground.