Understanding Double Impressions On Tablets

Description: A tablet can be designed with a monogram or image that is embedded on it. The embedded form is produced with a suitably shaped punch in the tablet press. Double impression is where the shape appears to have been stamped twice on the tablet.

Cause: Each tablet is imprinted with the design during the compression stage. Double imprinting may be the result of the lower punch not being secure, allowing it to drop freely a short distance thereby causing a new imprint on the tablet. The effect can also occur if the upper punch is unrestrained allowing it to accidentally rotate and accidentally imprint the tablet for the second time. Double impressions cannot be formed on the TDP 5 or other desktop presses as the top and bottom die are firmly secured in position.

CAUSE SOLUTION
Rotation of either the upper or lower die during pressing or ejection process
  • Use keying on the punch die tooling
  • Use machinery with anti-turning designs already in place
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