Optimal develops inspection system for blister packs

Inspects two sealed blister packs a second for pharma client

Optimal has developed a high-speed inspection system for blister packs for a pharmaceutical client

Optimal Industrial Automation has developed a high-speed vision system for a major pharmaceutical manufacturer that inspects sealed blister packs at a speed of two packs a second.

The packs are for the Japanese market, with Japanese text, and both sides must be 100% inspected. The natural variation in the blister packs is a challenge, compounded by the fact that they are made from highly reflective aluminium foil.

‘The client’s requirements were daunting,’ said Optimal director Martin Gadsby. ‘The pharmaceutical firm needed to inspect to a standard that was higher than anywhere else: in effect, a zero tolerance standard.

‘In addition, the speed of the line and the very small visual differences between the required standard and those that had to be rejected, were major issues.

‘These factors made the project very challenging, and were presumably why other vision inspection companies had declined to take it on.’

The vision inspection system had to inspect that the correct lot code and expiry date were in place on each blister; that the overprint was correct with no defects; and verify that there were no scratches, dents, marks, holes, or surface contamination of any kind on the blister packs.

Optimal, based in Yate, Bristol, undertook a significant r&d programme and developed a range of lighting techniques to provide the desired effects, while not being troubled too much by the natural variations in the blister packs.

The firm also developed specialised synTI software that would enable image analysis in real-time.

The final system integrates high-speed digital cameras, lighting, image analysis techniques and software that identifies sub-standard packs and rejects them from the production line.

‘The fact that the blister packs reflect light made the acquisition of useful images very difficult, and also increased the difficulty of being able to see the desired surface defects to the required resolution,’ said Gadsby.

‘Also, the blister pockets naturally move in each blister: not a huge amount, but sufficient to make a simple direct image comparison invalid. To overcome these problems, multiple images using differing lighting techniques were found to be necessary, all of these having to be correctly synchronised to each blister pack.’

The system is now in daily operation and Optimal aims to talk to other pharmaceutical clients who might be interested in the technology.