Subsequently, {HEAD ~ the grinding wheel} sequentially grinds the remaining object portions while {TAIL ~ the first wheel head} is returning to its home position 
Subsequently , { HEAD ~ the grinding wheel } sequentially grinds the remaining object portions while { TAIL ~ the first wheel head } is returning to its home position
OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH