Blister packaging: catching forming issues before you fill and seal

By Daphne Allen in Blister Packaging Machinery on August 27, 2014

An inspection system uses light to check film material on the packaging line.

“Is your package in shape?” asks Christoph Lehmann, director, Visiotec GmbH.

The forming process of blister packaging is “one of the most critical process steps next to feeding products into blisters or trays,” argues Lehmann. Variation in material thickness or thickness distribution in formed cavities could impact the ability of the package to maintain the intended barrier function. Visiotec, a member of the Uhlmann Group, develops solutions to drive process efficiency, such as 100% process monitoring or process safety and control in manufacturing and packaging operations.

To monitor blister forming consistency, Visiotec has developed FormChecker. The inspection system measures thickness and thickness distribution of clear and transparent film materials and components, explains Lehmann. “This innovative technology helps to consistently and immediately produce in-spec blisters and trays. In-spec means the pocket/cavity is formed out properly and is safeguarding its content against environmental influences.”

FormChecker inspects formed cavities right after forming, before filling and sealing. “The measurement is based on light (sender) penetrating the thermoformed and/or flat material,” Lehmann explains. “The receiver is converting the transmitted signal information into thickness in microns (µm).”

Barrier against moisture correlates directly to the thickness of the walls of the package, says Lehmann. “Too thin means that moisture can diffuse easier and quicker inside the cavity, harming the product by reducing its shelf life/efficacy and potentially causing discoloration.”

But rather than just catch problems, the technology allows users to optimize barrier within tight tolerances. “Another consideration is, why should one use extra-thick material when there is a technology available that allows one to always stay within the allowed boundaries that already have been established in stability testing?” asks Lehmann.

There are multiple sources of forming variation, explains Lehmann. He offers the following potential reasons for variations in material thickness and thickness distribution:

  • The base material quality itself.
  • The proper function and setting of the heating and forming stations (e.g., temperature) or the speed of the entire process.
  • The timing of so-called plug-assists inside the forming station, which are mechanical plugs to pre-form the blister or tray. This is a technique that is typically used when the cavities need to be drawn down very deeply (e.g., for blisters holding vials, syringes, or any medical devices that require more ‘footprint,’ or typical consumer packaged goods (CPG) display packs with hanger holes carrying toothbrushes, batteries, etc.). Prior to applying compressed air to shape out the cavity, some of the material that is smooth at this time because it is heated up is ‘forced’ downwards, then the remaining gap is formed out by air. By doing this, the material thickness in critical areas of the cavity such as the ridges stay thicker than forming without plug-assist. Consequently, the cavity is more rigid and provides better moisture barrier in those otherwise thin areas.
  • New packaging materials that are more difficult to control, such as PET. More and more companies have sustainability and carbon footprint initiatives in place, and one current initiative for numerous companies across the industries is to eliminate PVC, which is relatively easy to form. The alternate films are in some instances quite tricky to control; hence, an inline-monitoring system supports maintaining the quality of the form in shape.
  • Users now can catch variations in formed cavities before the filling step, correcting problems before filling and sealing and potentially reducing product waste or repackaging. For instance, “machines using a dedicated product feeding system can be signaled by the system to skip feeding for the section of formed web where the issue was detected,” Lehmann says.

When asked whether FormChecker could help improve OEE or other measures of efficiency, Lehmann says yes, offering these potential process benefits:

  • Ramp-up phases can be reduced during start-up of production.
  • Outliers and quarantine are reduced, which are caused by finding an out-of-spec during an in-process control (IPC) sampling. Because of the 100% monitoring, trends are noticeable on-time, and one can counteract immediately. Even automatically, if necessary, via feedback loop to the heating and forming station. This is part of the “Smart Factory” (aka Industrie 4.0) approach, in which smart and fully automated systems are fully and entirely self-regulating production processes.
  • If a dedicated feeding system is used and an out-of-spec cavity is detected, products are saved because they are not fed, and only the formed material is rejected. Also, stops caused by poorly formed cavities initiated by the machine’s safety flap are avoided when products are sticking too far out of their pockets.
  • Packs are always in shape, and poorly formed cavities (which even might fulfill the thickness criteria but just look bad) are caught immediately, rather than when a patient or consumer catches that package on the market, causing complaints.

Finding formed material thickness consistent and as intended could reduce some downstream testing or sampling, “in theory,” Lehmann says, but not entirely. “In pharma, most likely not all sampling will be eliminated. There will stay a degree of sampling, which makes sense to challenge the systems against each other. Due to the criticality of pharmaceutical products, the industry ‘standard’ is kind of like ‘wear a belt and a suspender’, means that redundancy guarantees the final quality of the product. From the perspective of a patient it is good to know that multiple safeguards are in place.”

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