if first shift starts at 7am and assuming 30 minute unpaid lunch would follows:
1st 7am-3:30pm
2nd 3pm - 11:30pm
3rd 11:00pm - 6:30pm
allows for 30 minute overlap for relief of duty.
EDIT: full time union workers at the plant I work for follow those hours except just an hour earlier if we're running 3 shifts.