This always seems to cause troubles in every sim game I've played. Here's the NHL's rules regarding waivers: The “Playing Season Waiver Period” (which I will call “waiver period”) begins 12 days before the start of the regular season and ends the day after a team’s season ends.
This means waiver don't apply in the preseason until 12 games before puck drop on the start of the NHL season and doesn't apply from the elimination from the playoffs. I've started my first season and over two weeks before puck drop I'm sending guys down from training camp and they have to clear waivers. That shouldn't happen.