It’s also one of the most error-free, thanks to a vision system from Cognex Corp., Natick, Mass. The machine fills and seals up to 500 tubes per minute. In contrast to conventional tube filling machines that operate using a turntable, the TFS 80-6 has a conveyor circuit with a diagonal layout. With the process lines positioned at a 90-degree angle to each other, the tubes are picked up horizontally; cleaned, filled and sealed vertically, and then placed back down horizontally on a conveyor belt that takes them to a cartoning machine for final packaging.
Though rare, contamination of the tubes by foreign matter does occur. Also, tubes may be deformed when the outer packaging is applied, or there may be a faulty seal at the base of the tube. To ensure that none of these faults are passed along to the customer, IWK worked with machine vision integrator Octum Electronic GmbH, Obersulm-Willsbach, Germany, to integrate two Cognex cameras—an In-Sight 5100 and 5400—into each of the system’s three inspection stations. Each camera monitors a set of parallel conveyer rows with offset tube holders.
During the first operation, a six-axis robot with an expanding gripper arm takes the tubes out of the boxes they are delivered in and places them, with their open lower end pointing upwards, into the conveyor’s tube holders. The screw cap is already in place at the top of the tube. The conveyor system moves the tubes clockwise toward the cleaning and filling station. Before they reach it, a scanner checks that the tubes are aligned correctly so that the printing is in the correct position when the base is sealed later. Two successive inspection stations check that the tubes are round and clean before they go through the cleaning and filling stage.
The In-Sight cameras installed above the conveyor evaluate the tube ground coat, the shoulders of the tube and the inside of the tube cap during the particle check. The cameras detect foreign particles based on their contrast with their surroundings. A red, ring-shaped light-emitting diode (LED) illuminates the inside of the tube from above. Any undesired particles cast a shadow that is detected by the cameras.
During the subsequent tube roundness check, another two In-Sight 5100s check whether the tubes are of the required shape. If the tubes do not have the specified roundness, the nozzles stay at the edge during the cleaning and filling process. The vision system ensures that the nozzles enter the tubes accurately to within a tolerance of 3 millimeters (mm). The individual cameras receive a trigger for every tube and record pictures of the packages as they move past. If a tube is out-of-round or outside of the tolerance range, it is identified as faulty and is not filled, and the TFS 80-6 subsequently ejects it from the production line.
After cleaning and filling, the ends of the laminated plastic tubes are heated by hot air at a temperature of 380 C to 450 C, and then pressed together by cooled stamping jaws. The seal is either stamped smooth or in a corrugated pattern, and may feature a serial number or code.
Defects sometimes occur at this stage. For example, if a knife becomes blunt and can no longer cut off the ends of the tubes correctly, the seal will be left with rough edges. In the trimming station, two In-Sight 5400 cameras thus make sure that all faulty packages are detected. The cameras also check the seal itself. If it is not complete or if the printing is not properly aligned with the specified parameters, the faulty tube is ejected from the process.
The cameras are networked to a central panel personal computer which records all of the images of faulty pieces. In addition, since the Octum/Cognex system is integrated in the production process rather than being placed in inspection stations at the end, IWK is able to ensure fault-free tubes with fewer cameras, reducing overall system cost.
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To read the feature article relating to this story, go towww.myenum.com/feature-5284.
