Using a buffer overrun/s-t-u-t-t-e-r processor, especially when combined with the right compression and bit reduction, can create the sound of a robot that is digitally-fried or breaking down.
Using a pitch correction tool to remove all inflection when not using a vocoder will help to remove emotional expression from the voice, and make it sound less human.
Another thing to try is when you have your phrase completed, ReCycle it into its parts and then use some method to alter/mangle the timing and cadence. This also helps to sound less human and much more mechanical. Subtlety is key when using this technique, especially when the voice has already been vocoded or pitch-corrected.
Sluttiness is a state of being, a philosophy, a way - not the gear you own.