Interview: SACMI’s top tips for smooth transition to tethered cap production

In an effort to reduce leakage of plastic waste to the ocean, the EU issued the EU Directive 2019/904, requiring all single-use plastic beverage container closures must be attached to the containers from July 2024 at the latest, as a means to ensure that the entire packaging can be recycled.

Cap producers and bottlers have to get ready for the transition to tethered caps, and it is a long process that involves several kinds of investments. Therefore, they have to consider: What do the customers accept? What design should be adopted? Can the existing equipment be used? How much does the switch-over cost?

New cap designs and system solutions have been developed for tethered caps.

SACMI has been active on developing solutions for tethered cap since the publication of the EU Directive 2019/904. The Italian packaging machine manufacturer’s systems can produce eight types of tethered caps with hinges or single or dual tether strips.

Adsale Plastics Network talked to Iacopo Bianconcini, Marketing & Business Development Manager, Rigid Packaging Technologies BU of SACMI, and got his expert opinion on tethered caps production.

Iacopo Bianconcini, Marketing & Business Development Manager, Rigid Packaging Technologies BU of SACMI.

Slitting pattern and snap cap design

There are two fundamental designs for tethered caps, the slitting (threaded) pattern and the snap cap design. The slitting pattern is compatible with all beverage types, while snap caps can be an option for packaging non-pressurized still water.

Regarding the technical requirements of these two designs, Iacopo Bianconcini pinpointed the advantages of slitting pattern.

“There is no additional complication on molds (for slitting pattern), and it is possible to fit the same number of cavities as before on the same molding machine,” he said.

“Besides, the band can retain its axial symmetry and this can be an advantage during high speed capping,” he continued. “Stable hinges, simpler designs or historic slitting patterns are possible on the same suitable caps, simply changing slitting tools.”

From Iacopo Bianconcini’s point of view, although “they (snap caps) have found their niche into the market and the application is expanding”, snap caps are not optimized for sustainability. 

“For example, the most common 26 mm snap cap weighs 1.3 g against less than 1 g for 26 mm screw caps. Besides, the bottles should be heavier and more rigid than bottles used for screw caps, so as to avoid water splashing while opening the packages,” he explained.

Snap caps can be an option for packaging non-pressurized still water.

CCM tethered solutions with downstream rotary slitters

Plastic caps can be molded by compression molding or injection molding. Iacopo Bianconcini recommended CCM (Continuous Compression Molding) technology with SACMI lines. The advantages are shorter cycle time, greater dimensional consistency of the product, and simplicity and reliability of the process.

For tethered caps, SACMI proposes solutions where a rotary slitter at downstream of the press scores the tamper evidence band.

This configuration of the line with separate cutting ensures constant cutting quality over time, easy maintenance of the components involved in the cutting process, and the possibility of producing with different cutting configurations on the same production line.

Separate cutting also benefits the molding process as the mold is less complicated and is easier to maintain. The molding process is also less complex and is easier to control.

Generally speaking, the choice of resin type is not critical for tethered caps, in particular for slitting pattern. Iacopo Bianconcini thus recommended customers to keep using the resins they used.

A versatile post processing line for production

SACMI has recently introduced a new high-speed post processing line consisting of four modules for feeding, scoring, folding and inspection for both tethered and traditional cap production.

According to Iacopo Bianconcini, the unique benefits of the line is that the collected information lets producers intervene upstream from the process, either via automatic machine adjustments or by providing the operator with information on how to act on the appropriate process parameters.

“The latest-generation inspection system operates at a level of detail unattainable with traditional cameras and improves self-adjustment of process machines on the basis of actual scoring quality,” he added.

This post processing line includes the SFMO8L tamper evidence band scoring and folding machine equipped with the newly designed ORGRS waterfall feeder, the CVS154 and CVS 36-3D multi-camera vision systems which performs multiple inspections by capturing multiple images; and the PFMC unit which inspects the tamper evidence band cut and measures its breaking force.

The new line is very compact and is designed for output rates of up to 1,000 caps/min (60,000 caps/hr).

SACMI’s new post processing line for producing tethered caps consists of four modules.

More efforts needed in reducing weight

At this time of transition, SACMI works with its customers to ensure their transition to tethered cap production to be smooth and painless with minimal economic impact, emphasized Iacopo Bianconcini.

Nevertheless, he believes the most viable way for plastic bottle to reach a better environmental balance in the short and medium term is lightweighting as many bottles are still far heavier than they might be, in particular in Asia.

“We are getting sporadic requirements from Asian countries, and it (tethered cap) does not seem to be a general trend in Asia,” he commented. “If the Asian beverage industry wants to improve its environmental footprint, it should focus more on packaging weight optimization, avoiding over packaging and unnecessary packaging components.”