mechanical man vs automaton

mechanical man and automaton both are nouns.

Word	Noun	Adjective	Verb	Adverb
mechanical man	Yes	No	No	No
automaton	Yes	No	No	No

As nouns, automaton is a hypernym of mechanical man; that is, automaton is a word with a broader meaning than mechanical man:

Other hypernyms of mechanical man include golem, robot.

mechanical man (noun)	automaton (noun)
an automaton that resembles a human being	a mechanism that can move automatically
	a machine that operates on its own without the need for human control
	someone who acts or responds in a mechanical or apathetic way