By joining their expertise, Harro Höfliger, a mechanical engineering company, and the machine vision experts at STEMMER IMAGING have implemented a high- performance filling system for functional pharmaceutical tubes.
The design and construction of clean room systems for pharmaceutical industry is particularly challenging. The production of pharmaceuticals and medical solutions as well must meet the highest requirements in terms of processing and quality. The internationally successful company, Harro Höfliger Verpackungsmaschinen GmbH, located in the Swabian Town Allmersbach im Tal, has been specialising in these demanding industrial sectors, developing integrated system solutions and customised machines for pharmaceutical, chemical and food industry for more than a quarter century.
One of the company's strongest points is the design of clean room machines for the manufacture of pharmaceutical and medical products. "These systems must be capable to meet above-average standards", explains Manfred Hild, Control Engineering Department Manager at Harro Höfliger. According to him, this results from the aggressive cleaning agents frequently used in clean rooms, significantly reducing the range of suitable materials that can be used. "Such systems", adds the Division Manager, "need to be easily cleanable and must not be susceptible to failure as the individual system components may be difficult to access. The integrated systems for measurement, illumination and detection usually need to be encapsulated, thus involving tedious and complicated work to replace them in case of fault or for maintenance."
In a recent project, which again was subject to such difficult conditions, the Swabian company has supplied to their customer a solution with two identical filling machines for "tubes for oral live-virus vaccines", designed for filling liquids and paste-like materials into plastic tubes. The user can then easily squeeze out, like toothpaste, the contents of these tubes and use them. "During implementation of these two machines not all optical material properties had been known", describes Manfred Hild one of the difficulties experienced by his team.
Even more challenging, however, was to select the best machine vision components for the alignment station of the machine. Before reaching the alignment station, the tubes are transported in a non-oriented position. Once the tubes have been separated, they are aligned in an upright position with the tube cap downward. A special gripper seizes ten tubes simultaneously in each step and transfers them to the alignment and rotation station.
Before the substances can be filled into the tubes, they need to be aligned and moved into a defined rotation position. This intermediate step has two reasons: one is to ensure that the tubes will not break along the longitudinal joint during sealing and become leaky. The other reason is that the pharmaceutical manufacturer wants to ensure that the prints on the tubes always have the same location after sealing, thus being perfectly readable.
To accomplish the task, ten tubes each are grasped by the gripper mentioned above and deposited in special holders where they are then positioned by turning them around their longitudinal axes in 400 ms. During this process, five DALSA Genie CMOS cameras from the Canadian manufacturer Teledyne DALSA check two tubes each for correct position of the print marks needed for proper orientation of the tubes. The image signals transmitted via Gigabit Ethernet interface are evaluated on two PCs using the powerful VisionPro software by Cognex. The results of this evaluation are then communicated to the rotation stations. The image processing system thus ensures that the positions of the ten tubes remain within the necessary precision limit of less than 2 degrees*.
The Genie cameras used were able to provide the necessary frame rate of about 110 images per second with a defined field of view resolution of 1024 x 768 pixels. "As only part of the image was needed for tube alignment, we were able to operate the cameras in partial scan mode which made it possible to increase the frame rate even more", reports Manfred Hild. In this way, the system manages more than 220 tubes per minute, thus providing the performance needed for cost-effective production.
Once the suitable cameras had been selected, further issues still had to be addressed. Taking into account that the system has been designed for clean room applications, the entire hardware for image processing inside the machine had to be installed in a housing specially developed by Harro Höfliger. This housing has been designed in accordance with GMP regulations (Good Manufacturing Practice) and has a special surface coating for easy cleaning.
As the cameras, lenses and lights had to be installed under glass owing to the cleaning requirements, the installation angle of the cameras had to be selected in such a way as to prevent light reflections on the camera. Another difficulty was the limited space for the cameras inside the housing. "To solve this problem, we have chosen 90° angled heads for the Genie cameras, as recommended by our vision partner STEMMER IMAGING", explains Hild.
We also had to take into account that it was not possible to completely shield the system from extraneous light and that pivoting tools of the machine protruded into the camera's field of vision. "These brilliant chrome parts create various disturbing reflections while moving. But we have managed to solve this problem by combining edge detection and histogram vision software tools", describes Manfred Hild the approach taken in this matter.
Another difficulty was to detect the white semi-transparent tube edges and the print marks on the tubes against the silver steel background or the glass panes in the machine. According to Mr.Hild, STEMMER IMAGING provided a solution for this problem as well: "Tests performed during the design phase made it clear that LED light sources with wavelengths in the blue spectrum provided the best contrast between the tube and the print mark and between the tube edge and the background."
For Manfred Hild, the alignment station developed together with STEMMER IMAGING is the key part of the machine: "Our customer attached great importance to the correct rotation position of the tubes before filling and to an increase in productivity. To meet these requirements, we absolutely needed a suitable image processing system." He summarized his words in a general statement: "The pharmaceutical industry insists on total control of their products, covering all fields, from plasters to capsules. For this reason, there is practically no machine without a complex image processing system in this industrial sector."
According to him, this is a reason why Harro Höfliger, in contrast to other players of the branch, employs its own machine vision specialists. "We consider this technology a central topic of our work. Having the necessary expertise ourselves enables us to provide a more comprehensive and faster service to our customers", explains Mr. Hild, who feels confident that this strategy is much more efficient considering the large number of machines produced by his company every year.
In spite of, or maybe just because of, the machine vision expertise available in their own company, the team around Manfred Hild rely on a strong supplier for the image processing components required. Hild feels certain that he has already found the right partner: *"STEMMER IMAGING has been Harro Höfliger's supplier of machine vision products for many years already. I particularly appreciate the company's consultancy services when it comes to select the best components for the respective application. This has often saved us precious time", stresses Hild.
Hella Gillig is the sales contact at STEMMER IMAGING for many of the projects already carried out. In cooperation with colleagues specialised in certain fields, she determines the suitable components and has the necessary tests performed in the company's laboratory. "In this way, we can always use our wide range of available resources, with the option of drawing on the latest developments from our suppliers", says Gillig and adds that hardly a customer could afford to have his own image processing laboratory with comparable comprehensive and up-to-date equipment. Manfred Hild also values this offer:
He mentions another reason for their cooperation with the technology suppliers from Puchheim: "Purchasing image processing components from one source and relying on globally available products is part of Harro Höfliger's strategy. The systems we produce for our customers are used all over the world. Being able to provide fast replacement of components even internationally is therefore very important to us."
Since both Harro Höfliger and STEMMER IMAGING use standard components as far as possible, the new owner of the functional tube filling machine can be assured that maintenance of the system will not cause any problems.
About Harro Höflinger
Harro Höfliger, with its headquarters at Allmersbach im Tal, started to focus on the design of machines with sophisticated requirements already many years ago. The company employs more than 600 people across the world and considers itself above standard mechanical engineering companies as it mainly develops customised machines for clients operating on an international level with core activities in the medical and pharmaceutical industries. In many other industrial sectors, Harro Höfliger has an excellent reputation as a key supplier of production systems and system solutions, for example in the fields of aseptic technology, blister and tablet technology, syringe/injection technology and capsule and powder filling machines and in other fields.
Aiming to make life easier to its customers, the company is part of a network of globally acting mechanical engineering suppliers to the pharmaceutical industry. "The complementary competencies of these companies make the customers of the association benefit from quick and uncomplicated solutions", explains Manfred Hild. "This network of companies provides the advantage of using synergies, because sharing technologies means halving the cost of development. Thus the associated companies are not only in a position to cover a huge area, but also to provide services at favourable prices, guaranteeing, for example, a 24 hours service."
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