DETROIT — After nearly 20 years working on the line at Ford Motor Co.’s Michigan Assembly Plant, Bob Wieck is used to change.

The 39-year-old started at the site in 1999, and during his career — which included a brief stint at the Dearborn Truck Plant — he has switched from building cars to trucks to cars and, next year, back to trucks.

Wieck had been making Ford’s unibody Focus sedan at the Wayne Stamping and Assembly Plant when, in 2009, the automaker decided to close it, consolidate production at neighboring Michigan Truck and rename the site Michigan Assembly. The state-of-the-art factory would build gasoline, electric and hybrid small cars after a $550 million renovation using a government loan. Wieck was moved to Dearborn Truck for about a year during the conversion, but returned to renovated Michigan Assembly in 2011.

He said initially workers were worried and confused over the closure and transition, but were ultimately excited that Ford dedicated major resources to adding C-Max hybrids and increasing Focus output.