Fade in fade out effect to Combined objects in maya


Can any one please help me know how to apply fade in fade out effect on a combined object in maya? I am able to apply fades on objects using material attributes (transparency). But its too difficult to fade multiple parts of the object that way. So i tried combining them and apply fade, but its not working. Even after combining the parts i can see individual material attributes. Please help as i have just started working as a freelancer and this challenge is hindering my project.
Thank you in anticipation.