As {HEAD ~ the substrate} moves over {TAIL ~ the table surface}, it contacts the first and second grinding apparatuses 
moves over
As { HEAD ~ the substrate } moves over { TAIL ~ the table surface } , it contacts the first and second grinding apparatuses
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH