STEMMER IMAGING

Mucoadhesive Buccal Film (MBF) is the medical term for the delivery form of the strong painkiller for which the internationally operative mechanical engineering company Harro Höfliger develops and builds production and packaging systems.

What patients ultimately remove from the packaging and allow to dissolve in their mouths to relieve pain must satisfy the strictest quality requirements at every stage of processing.

"In our PMK 150/300 production and packaging machine the MBF active ingredient, which is applied to a carrier film, is initially wrapped up in the form of a roll and the protective film on the upper side is pulled off by an appropriate mechanism", says Hartwig Sauer, head of the machine vision team at Harro Höfliger, explaining the first step of the machine process.

"The web is subsequently printed with data for the active ingredient dosage by a flexo printer. The active ingredient is evenly distributed in the laminate so that the medicament dosage can be controlled by the size of the MBF." In this plant the products with sizes between 10 x 10mm and 17 x 17mm are sealed in 50 x 50mm aluminium bags between an upper and lower aluminium composite foil.

Three image processing stations

The first of a total of three image processing modules in this system checks that the printing is correct on the front side of all three active ingredient strips with a maximum speed of 1050 parts per minute or almost 18 parts per second – on each ofthree webs. The triggered image capture across all three strips and 150 mm beyond is done by a Spyder3 line scan camera from Teledyne Dalsa with a resolution of 4k pixels and an APO-Componon lens from Schneider Kreuznach. Red LNSP line lighting from CCS provides the appropriate illumination. The images from all three image processing modules are evaluated by an Industrial PC, which is described separately below.

Faulty parts are marked in the machine's internal shift register as "bad" and discharged into a separate ejector at the end of the machine.

Subsequently, the final products are cut out of the three webs with a rotary die cutter and transferred to the lower packaging film by means of vacuum. The products should now be placed on the carrier material in three rows with correct longitudinal and transverse spacing, which is what the second image processing station checks: firstly, it checks the position of the separated products to ensure that the subsequent sealing process can proceed correctly. Secondly, this station also checks the product size and for contamination by foreign bodies. This fault is detected by the system down to a size of about 1 mm².

The image capture across all three strips at this second image processing station is done once again by a combination of a Spyder3 line scan camera from Teledyne Dalsa with a resolution of 4k pixels and an APO-Componon lens from Schneider Kreuznach. Blue LNSP line lighting with coaxial attachment from CCS provides the optimum illumination of the strips here. With the aid of this blue lighting the product – and the lettering in the case of a later extension by printing checks – can be contrasted optimally with the background at this point.

A third image processing station checks the printing of the upper packaging material web. This inspection is very similar to the first station: The items printed beforehand – the production data, shelf life, batch number and packaging material number in the form of a 2D matrix code – are checked.

Demanding evaluation

The linear image data of all three image processing stations are transferred to a specially assembled computer in which a microEnable IV frame grabber from Silicon Software buffers the incoming line data, assembles them into complete images and then evaluates the images. "This part of the task was extremely demanding, because the images are captured with an overlap beyond the individual products", say the responsible application engineers Achim Hasmüller and Goran Tambolas from Harro Höfliger, explaining the particular challenges. "Each image consists of the end of the preceding product, the complete current product and the beginning of the following product. In this way we were able to ensure that errors at the interfaces between two products are also detected reliably." Since all captures are triggered, the positions of all faulty products in the process can be tracked precisely in order to be able to eject them as bad parts at the end of the machine.

Following various unsuccessful attempts with other technologies, the machine vision team from Harro Höfliger were able to solve this processing task with a frame grabber in combination with the Visual Applets software environment from Silicon Software. A computationally intensive part of the image processing is done by an FPGA on the frame grabber, thus reducing the Industrial PC's CPU load through suitable image pre­processing.

Expert partners

"At this point in the process, which is crucial for the processing as a whole, it can be seen how important it is to co-operate with expert partners", Mr Sauer emphasises. "Following training by Silicon Software on the optimum use of the FPGA architecture on the frame grabber in combination with Visual Applets, we commissioned *STEMMER IMAGING to carry out the adjustments that were necessary for our special requirements. STEMMER IMAGING took care of the FPGA programming and has continually developed the image processing system together with us so that, amongst other things, monochrome and colour line scan cameras* can be used."

Harro Höfliger has relied for many years on its machine vision technology supplier. "STEMMER IMAGING supports our open concept of selecting the optimum imaging components for each of our customers' systems in order to be able to meet their individual requirements. The enormous variety of technologies and components for all disciplines of machine vision ensures that we can satisfy our customers' wishes", says Hartwig Sauer.

He also highlights the quick and reliable advice that he and his team get from STEMMER IMAGING: "It saves me time and effort if I can clarify all pending questions or discuss new machine vision technologies with just one expert partner."

Harro Höfliger has now sold more than 100 of the systems described here worldwide. For future systems too, with web widths exceeding 300 mm, Hartwig Sauer is certain that when it comes to machine vision STEMMER IMAGING will continue to be used as a component and technology partner for joint developments in the machine vision sector.