West Coast has cruised into the club's seventh AFL grand final, with a thumping win over Melbourne at Perth Stadium to set up a decider against Collingwood.

It was a nightmare for the Demons, who were jumped from the start and kept goal-less until half-time — the first team held without a goal in the first half in a final since 1927.

West Coast led by 63 points at the main break, before the home side clinched victory by 66 points, 18.13 (121) to 7.13 (55).

Led by Josh Kennedy (four goals) and Jack Darling, Mark LeCras and Jamie Cripps (all with three majors), the Eagles were unstoppable as they swept into their first grand final since 2015, when Adam Simpson's men lost to Hawthorn by 46 points.

The Eagles were cheered home by a big home crowd of 59,608 at Perth Stadium.

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West Coast will now face Collingwood in next Saturday's grand final, following the Magpies' stunning upset win over Richmond on Friday night.

Like the Magpies and their coach Nathan Buckley, the Eagles and Simpson have had their ups and downs, with plenty of criticism aimed at the team after two relatively early finals exits in 2016 and 2017 following the grand final loss to the Hawks.

West Coast lost the side's first home game at Perth Stadium to the Swans, but since then have won 10 out of 12 on their own deck — and few if any of those wins came easier than the victory over the Demons.

Melbourne came into the game with confidence after two top finals wins over Geelong and Hawthorn, coupled with the recent experience of beating the Eagles in the west in round 22.

But from the opening minutes of the preliminary final, it became clear that West Coast was on song — and Melbourne was not.

With key players like Jack Viney, Christian Petracca and Tom McDonald kept very quiet, the Demons struggled from the get-go to get their hands on the ball.

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A team that had dominated contested possessions during 2018 trailed by eight at quarter time, and 14 at the half, starving the visitors of crucial ball.

Meanwhile the Eagles' direct style paid dividends, with West Coast kicking twice as often as their handballs.

Liam Ryan and Willie Rioli were there at the fall of the ball up forward while Kennedy and Darling combined in attack to give Melbourne problems.

Kennedy and Darling have both been on the field in 12 games this season — the preliminary final makes it 12 wins and no losses for the Eagles in those games.

With the game all but gone after half-time, Clayton Oliver's first-minute goal opened the Demons account in the third quarter.

But despite Melbourne's more fluent attack kicking five goals for the quarter, they still trailed by 61 points at the final change after the Eagles also booted five for the term.

The final quarter was a fait accompli for the home side, who ran out the game with ease.

The Eagles will have a couple of injury concerns ahead of the grand final, with Luke Shuey injuring an ankle in the first half but returning to play out the game.

Key defender Jeremy McGovern also looked sore after receiving a solid bump to the hip.