The workpiece may be a single piece of {HEAD ~ material} or a plurality of pieces of material which are bonded together under {TAIL ~ the influence} of heat and pressure 
The workpiece may be a single piece of { HEAD ~ material } or a plurality of pieces of material which are bonded together under { TAIL ~ the influence } of heat and pressure
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH