I think this is an early 90s movie.

Basically this guy has these nasty boxes that he places over someone's head and switches on, they have a powerful motor inside, winding a steel cable noose into the box thus decapitating the unfortunate victim.

There's a bit in it where one of the severed heads is used as a disguise briefly.

I found it myself! (I think)

Trauma (1993)

Going to watch it and see if it's the right one!

I saw one that sounds like that but I am thinking of one other than that... I just can't remember the name of it.