Box Hill's preliminary final opponent has been locked in, after Richmond convincingly defeated the Casey Demons in Saturday's semi-final.

The Tigers piled on eight goals to two in the second term to escape to an early lead. Despite a seven-goal third term, the margin proved too large for the Demons, who trailed by 27 points when the final siren sounded.

Richmond now face Box Hill at Fortburn Stadium this Saturday 16 September at 2.40pm, with the winner to guarantee a 2017 VFL Grand Final berth.

Port Melbourne has also locked in a preliminary final appearance after overcoming Footscray by 30 points, and are set to take on Williamstown as the two teams fight for the remaining grand final position.