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On the lookout for the perfect screw cap

 On the lookout for the perfect screw cap

The Packaging Steel business unit has developed a new, high-quality, low-earing packaging steel for the production of particularly thin-walled screw caps.

Photo: thyssenkrupp

There are some things that seemingly never change. Cam screw caps, for example, commonly used for bottles or pickle jars. After all, most screw caps and packaging solutions are just fine as they are – right? Actually, the Packaging Steel business unit at thyssenkrupp is never satisfied with the status quo. As a technology leader for this packaging material, the Andernach-based business unit of the company is constantly researching new material properties and production processes for metal packaging, which includes bottling screw tops.

Not all tinplate is created equal

The latest innovation from the thyssenkrupp tinplate industry experts is rasselstein® Ultra-Low-Earing Steel. This is particularly well suited for the production of the cam screw caps mentioned before. That’s because this steel is exceptionally homogeneous and isotropic. This means that the tinplate always reacts in the same way to the most varied loads from different directions when being processed into a cam screw top. This avoids unwanted protrusions and uneven wall thicknesses. But what exactly does “earing” mean?

Low earing, efficient packaging

Earing is a distortion effect that occurs during deep drawing, i.e., the process used to turn packaging steel into the specific shape of a cam screw cap. It creates a wavy edge at end of the deep-drawn part. However, a straight closure is essential for downstream processing: “Caps with protrusions will always get stuck somewhere, for example, on the tools or later during transport,” says Stephan Schiester, development engineer in thyssenkrupp's Materials Technology division. “A low earing level is therefore much more efficient, as it ultimately saves material and thus valuable resources.”

Packaging steel will expand its role as an environmentally friendly product.

Stephan Schiester, Development Engineer at Materials Technology, Packaging Steel

The sheet thickness makes all the difference

The new material also enables steel production of thinner-walled caps. “When trying to attain the same low thickness with conventional material, this will result in a noticeably poorer cam screw cap quality and thus a higher reject ratio,” explains Schiester. There are even certain screw tops that cannot be produced without low-earing steel, in particular cam screw caps with small diameters and high cup walls. “You simply need a material that delivers a high degree of homogeneity and isotropy.” rasselstein® Ultra-Low-Earing Steel has yet another advantage: The innovative steel also improves the quality of tensile pressure on deep-drawn cans. The new product is very popular with customers.

High quality and outstanding

The new material is also successful within the company: rasselstein® Ultra-Low-Earing Steel took second place in the Steel Tomorrow award, with which thyssenkrupp annually honors the steel innovations of its employees. “Of course, it helps to have the entire production chain in front of our eyes and to collaborate with our colleagues at thyssenkrupp Steel in Duisburg in the area of research and development,” says Schiester. “These and many other innovations will of course contribute to further expanding the role of packaging steel as an environmentally friendly and efficient product in the future. A development that also benefits the environment and thus all of us.

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