Coating: Protection against external damages
In the first operation, the sheets are coated on both sides with a layer of varnish. This is necessary as protection against corrosion and as a primer for the applied inks.
The lacquer on the inside strengthens the resistance of the crown cork against corrosion. At the same time, it is needed for the adhesion of the plastic sealing when the varnish is heated again in the following lining process.
The external lacquer is basically coloring the crown cork: gold, silver or white over the complete surface. It fixes the following printing inks and increases the resistance against corrosion at the decoration side of the crown cork.
After printing, a further layer of varnish is applied which protects the printing from damages.
Printing – from design to individual brand presentation
The printing of the lacquered metal sheets is the most challenging step in the production of crown corks.
The drafts of the responsible marketing depts. are first checked if there may be any technical issues of transferring the design into the crown cork specification.
Sometimes, drawings or letters have to be slightly expanded so that they do not “run into each other” when being printed. Also to be considered is the size of the printed surface and the possible amount of dust which will be generated during the closing process if the decoration is extended until the edge of the crown.
Shaping: Punching and Lining
During the process of punching and lining the crown cork is getting its typical shape with 21 flutes and the liner profile.
The lacquered and printed metal sheets are punched in the next operation. The material is simultaneously cut and deep drawn by punching. Now the crown cork has got its typical shape with 21 flutes.
From the punching machine the shells run into the lining machines. Here the crowns are provided with their polyethylene liner. The liner properties as well as the different sealing profiles are selected to match specific customer requirements.
The online camera control system is checking inside and outside of the crown for all quality parameters.
After passing the control system, the crowns are counted electronically and run without further contact into the customer specified packaging.