Boehringer uses machine vision to implement 100 percent testing of pharmaceutical capsules
At their main location in Ingelheim, Germany, the Boehringer company produces inhaled medications for respiratory disease. To meet quality control demands, the company designed and installed a machine vision system for pharmaceutical inspection with FireWire cameras to perform a 100% quality test. The optical testing facility was developed under the direction of Dr. Peter Stöckel, a senior scientist at Boerhinger.
The active ingredient in the capsules is loaded in micronized powder form into pharmaceutical hard gelatine capsules. Patients then load these capsules into inhalation devices. Each capsule contains 5.5 mg of powder, which is dispensed by filling machines into the capsules in the form of a weakly compacted cylinder.
The precise and rapid dosing of such a small amount of powder is an important development by Boehringer engineering. However, there remains a residual risk that the amount deposited into individual capsules might deviate from the intended value. For Boehringer, such risk was unacceptable.
Machine vision pharmaceutical solution
The machine vision system was positioned in the assembly process after the filling and before the sealing of the capsules. After filling, the content of each still-open capsule is imaged from above. The filling machine’s clock pulse triggers a Marlin F-046B FireWire camera from Allied Vision Technologies and its dedicated LED flash unit, not via the PC but rather directly via the camera’s external trigger input.
The half-capsule is then illuminated from below using a high-intensity LED. Since the camera cannot be housed over the capsules that are traveling past, it captures their contents via a tilted mirror on the side. The camera transmits the image data to an industrial PC. There, applications software analyzes the images. The software was internally programmed by Boehringer Ingelheim based on NI LabVIEW 7.1 by National Instruments.
After the capsule has been localized within the image, the imaging software first tests whether it contains powder at all. If so, then it analyzes the silhouette of the powder cylinder to derive the volumes and amounts of the active ingredient. If a capsule is identified as defective, it is sorted out by a SPS-controlled air jet.
Capturing 22 capsules per second
The most important challenge for the testing mechanism is speed. At an output of 80,000 capsules per hour, one capsule leaves the filling machine every 45 ms – put another way, the capsules move at a speed of 1.5 m/s, calculated Dr. Stöckel. For the camera, this means that 22 capsules per second must be captured. To avoid motion blurring, the exposure time cannot exceed 80 µs.
Meanwhile, the imaging system has successfully been installed on several machines in series production. “We are especially proud to have developed this innovative testing procedure in-house, in cooperation with Allied Vision Technologies and National Instruments.“ commented Dr. Peter Stöckel.
Source: Allied Vision Technologies.
Posted by Vision Systems Design
