Removing Fron and Rear Cover

Question

I can't seem to get the covers off of the maching. After removing the screws that appear to be holding it there is something in the center that won't let the covers come off. Does the base have to be removed first to get to the part holding the two covers together? I would like to get to the inner works to clean any pieces of thread etc. I would appreciate any help, thank you.

Bobrud