A knocked down flange typically occurs when a can body with a bent flange enters the seamer. Effectively this creates a false seam.
What this looks like using a seam inspection system (SEAMetal):
Possible causes of a Knockdown Flange:
- Bent can flange
- Damaged or bent end
- Mushroomed can flange
- Incomplete formation of can and end
- Filler or closing machine not properly timed