In {HEAD ~ a preferred embodiment}, the frame emulates a workpiece cassette and the distance sensors provide a numerical output of the distance to {TAIL ~ the workpiece} 
In { HEAD ~ a preferred embodiment } , the frame emulates a workpiece cassette and the distance sensors provide a numerical output of the distance to { TAIL ~ the workpiece }
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL