Everyone knows that toothpaste helps you maintain clean, healthy teeth. But is the toothpaste you're using to clean your teeth safe? It is only in recent years that vision systems have been implemented to check whether toothpaste packaging is clean and safe before the toothpaste tubes are filled.
Previously, filling systems that were not equipped with a visual checking system could not guarantee that no particles of dirt from the preliminary tube production stage would be inside the tube after the filling and sealing process. German company IWK Verpackungstechnik GmbH, in contrast, relies on Cognex vision systems in its latest packing machine: the TFS 80-6.
During the course of the filling process rather, the Cognex In-Sight cameras check that the 19- to 40-mm wide tubes are round, clean and firmly sealed. This in-process inspection reduced the number of cameras necessary from six units to just two.
500 Tubes Per Minute
With a capacity of up to 500 tubes per minute, the TFS 80-6 production line inspects, fills and seals toothpaste tubes in record time. Based on the needs of a single person using his or her toothpaste sparingly, a minute's production would be enough for a lifetime of teeth cleaning.
In contrast to conventional tube-filling machines, which operate using a turntable, the TFS 80-6 has a conveyor circuit with a diagonal layout. With process lines positioned at a 90° angle to each other, the tubes are picked up horizontally, then 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.
The packaging materials are required to be high quality due to the speed at which the machine operates, yet there can still be contamination by small dirt particles. Tubes may be deformed when the outer packaging is applied, or there may even be faulty seals at the base of the tube.
To ensure that its production processes are fault-free, IWK collaborated with OCTUM Electronic GmbH (a member of the Cognex partner integrator network) to install two In-Sight 5100 and 5400 cameras on each of three inspection stations. Each camera monitors a set of parallel conveyer rows with offset tube holders.
During the first operation step, a six-axis robot with an expanding gripper arm takes the tubes out of the boxes that they are delivered in and places them into the tube holders of the conveyor system, with the open base of the tube pointing upwards. The robot arm is equipped with a special tool with pins that precisely fit into the partition in the box and can pick up two arrows—a total of 30 tubes each time. The screw cap is already in place at the top of the tube, and the lower end is open for the filling procedure.
The conveyor system moves the tubes clockwise towards the cleaning and filling station. Before the tubes reach the station, however, a scanner checks that they are aligned correctly. This confirms that the printing is in the correct position when the base is sealed later. Before continuing through to the cleaning and filling stage, two successive inspection stations check that the tubes are round in shape and clean.
The In-Sight 5100 cameras installed above the conveyor and work areas evaluate the tube ground coat, the shoulders of the tube and the inside of the tube cap during particle check. The cameras detect foreign bodies based on contrast to their surroundings, while a red ring-shaped LED light illuminates the inside of the tube from above. Any undesired particles cast a shadow, which can be detected by the cameras, enabling users to detect objects that are camouflage with the tube itself.
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, ramming the packages back into the tube holders. This technology ensures that the nozzles enter the tubes accurately to within a tolerance of 3 mm. The checking procedure takes place without the need for an additional operation step during the process.
The individual cameras not only receive a trigger for every tube, but also record pictures of the packages as they move past. If a tube is misshapen or outside of the tolerance range, it is identified as faulty and is not filled. Further down the line, the TFS 80-6 seals the tube and ejects it from the production line.
After cleaning and filling, the laminated plastic tube ends are sealed with hot air at a temperature between 380° and 450°C. Then they are 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 can occur at this stage of the packaging process. For example, if a knife becomes blunt and cannot 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 without fail. The cameras also check the seal itself. If the seal is not complete or if the printing is not properly aligned with the specified parameters, the faulty tube is, once again, ejected from the process.
Saving Time & Reducing Costs
The In-Sight cameras are networked to a central panel PC that records all of the images of faulty pieces, which makes it feasible to detect faults quickly—without having to recheck the actual packaging item that has already been ejected from the process. The packaging process of IWK is thereby very reliable in terms of quality standards.
Another advantage of Cognex vision systems is their integrated structure. Whereas conventional packaging machines require a separate step for inspection, resulting in time delays, the Cognex technology is integrated directly into the production process, saving time and reducing overall costs.
This is because a machine with a separate checking module would require one camera for each tube. With six tubes being processed in each filling step, each checking station would require a total of six cameras and a total of 18 cameras would be required for three stations. The OCTUM/Cognex system is capable of meeting all inspection requirements with just six cameras over three inspection stations, thus maximizing process reliability and optimizing product quality.
For more information, visit Cognex Corp. at www.cognex.com.