Olmec UK has designed a novel vision system for 100% inspection of pharmaceutical tablets for a leading manufacturer of healthcare products. The tablets are inspected on packaging machines used for multiple products in order to prevent cross contamination - a tablet from a previous batch getting into the final packaging. The system, designed to inspect a variety of tablet types and colour combinations, was required to fit into a very limited space on the existing line and also provide good operator access for cleaning.
If cross contamination occurs on a pharmaceutical packing line and an incorrect, or rogue, tablet gets into the final packaging, the consequences for the patient could be potentially life-threatening. The implications for the manufacturer could also be massive, both in terms of reputation and costly product recalls, and possible production line closure while the problem is investigated. Industrial vision allows accurate inspection of the tablets before packaging with automatic stopping of the packaging line if a rogue tablet is detected.
The vision solution involved a redesign of the chutes carrying the tablets from a vibratory bowl feeder, to permit inspection of either falling tablets or tablets stacked up in the chute before they enter the pouches. The new chute features a 1 mm slit on each side through which the front and the rear of the tablets can be imaged as they pass through. Images of the front and rear of each tablet are acquired simultaneously by 4k resolution tri-linear colour line scan cameras positioned on either side of the chute.
The cameras are externally triggered at 10 kHz and each slit is illuminated by two high intensity spotlights which are strobed by a high speed controller that also handles the triggering of the cameras. The system has to ensure that there is no mutual interference between the lights, so that the lights for each camera are only on when that camera is acquiring its images. A PLC handles integration of the system into the packaging machine’s control system.
A special algorithm was developed for the measurement software to read a slice of data from the front and rear of the tablet to confirm the correct colour combination, since different tablet batches may be homogenously white or blue in colour, or even bi-colour – white on one side and another colour on the other. Imaging in this way is important for bi-colour tablets since they can enter the chute in random orientations.
The system will automatically stop the packaging line as soon as a rogue tablet is identified, ensuring that no rogues can enter the final pouches. The camera system was mounted on a specially designed ‘C’-shaped frame which can be cantilevered out for cleaning and set up of the packaging machine between batches. Since it is essential that the system is 100% effective, Olmec supplied a comprehensive set of calibration and verification routines that can be used on a daily basis.
