The preheat module has a vertically moveable rack and is loaded with various sized batches of {HEAD ~ wafers} with {TAIL ~ no vacant positions} between them 
with
The preheat module has a vertically moveable rack and is loaded with various sized batches of { HEAD ~ wafers } with { TAIL ~ no vacant positions } between them
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH