The heat hardening process may be individually controlled for each spring, and it may be performed in {HEAD ~ a very short period} of {TAIL ~ time} 
of
The heat hardening process may be individually controlled for each spring , and it may be performed in { HEAD ~ a very short period } of { TAIL ~ time }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL