Easy way to farm this one. When you get the robot mech suite, there is a hallway with a ton of helperBots. Additionally, there are machines that spawn about 4 at a time throughout this section. If you stand a couple steps from one (even better if you can get 2 on the screen), helperBots will spawn in constantly.
Just keep firing away, and you will get 4 - 8 at a time. About 125+ re-spawns will net you the 1000 cheevo. Keep at it for the 5000 as well