Blomberg refrigerator making intermittent loud knocking sounds coming from the ice maker
Icemakers work by freezing the ice, then thawing the outside, rotating the ice out of the tray, and eventually dumping it in the bucket.

If the ice fails to release from the tray, the gears will make loud gridnging noise until you remove the ice from the tray.

Easiest way I've found to do this is to run a hair dryer pointed at the icemaker until the ice releases.  Longer term, it seems that something is out of adjustment on your icemaker.  You can also shut it off by pushing the bail up.