For Milacron LLC, 2015 was a whirlwind year, as the plastics machinery manufacturer went public on the New York Stock Exchange, moved its headquarters as part of a 10-year tax credit package from Ohio, and bought Canterbury Engineering and Genca, makers of screws and barrels and crosshead dies. All that action after a 2013 in which Milacron plunked down $968 million for Mold-Masters Ltd., the major hot runner company, followed the next year by picking up Kortec Inc., a supplier of coinjection molding technology for making barrier packaging.