Complex sentence: The two defining characteristics of spin casting; semi-permanent (non-expendable) rubber molds and utilization of centrifugal force make the process relatively unique compared to machined die-based and expendable mold casting methods.
Split into simpler sentences: The two defining characteristics of spin casting are semi-permanent (non-expendable) rubber molds and the use of centrifugal force. These make the process relatively unique compared to machined die-based and expendable mold casting methods.