A Sharp Seam is a condition where the seam has a sharp edge and/or radius on the upper inside edge of the countersink wall. Sharpness is a conditional defect and must be evaluated by degree (Slight vs. Sharp). A slight condition must be carefully watched and corrected as quickly as possible. Considered a CUTOVER if metal fractures as a result. Cutover may occur along welded overlap on three piece cans.
POTENTIAL CAUSES:
First and second operation seaming roll set too high or too low in relation to the seaming chuck flange.
First operation seaming roll set too tight.
Seaming chuck worn at top of flange.
Using too narrow a first operation seaming roll groove profile.
Seaming chuck bell may be adjusted too low or is bent and dragging on the end.
Overly tight second operation seaming roll.
Foreign material lodged above seaming chuck.
Foreign material entrapped in seam.
SUGGESTED REMEDY:
Re-adjust seaming roll for proper chuck to roll relationship. For interlocking chucks and rolls, check for excessive wear in the interlock.
Loosen first operation seam roll.
Check seaming chuck for damage and replace as necessary.
Replace first operation seaming roll.
Straighten seaming chuck bell. Chuck bell to chuck clearance should be .10”-.20”.
Loosen second operation seaming roll.
Inspect for foreign material and remove.
Check filling procedures. Product must not be laying on flange during seaming.