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 PRINTING & PACKAGING TECHNOLOGY Written by: Glen W Spielbauer Printing and packaging technology are very important to our lives. Bags of potato chips, drink pouches, wrapped snack cakes and candy bars are all made with printed packaging material. Potato chips are bagged on vertical machines, while snack cakes and candy bars are packaged on horizontal machinery. Both the printing and packaging equipment have electronic photo-eyes, programmable logic controllers, plug-in timer modules, and microprocessor electronics for automated machine control. Examine a wrapped candy bar and you may see colored dots along the edge. Not all wrappers will have these dots, unless it is printed with more than two or three colors, or if they were trimmed off after printing. These dots were for the alignment and timing of the printing press, which prints the labeling before the product is packaged. For example, you may see three dots next to each other - such as black, red, and yellow. These color dots or patches are to print the colors for the label (both text and picture) in precise locations. Sometimes, primary colors are combined to make a specific color shade for a specific company. THE PRINTING PROCESS The Diagram shows a roll of continuous flexible packaging film being fed into the printer. The colored dots are in groups, with each spaced a set distance from each other. Each is group is identical. For example - black, red, and yellow. The roll is on a spindle, and the printing press feeds the roll into the print stations to print the label on the film itself. The speed must be very precise, so the motor is controlled by an electronic module to keep the speed both constant and exact. The printing press works at very high speed, with the film always moving. Each color is printed at a different station in the machine, one color at a time, so the film can keep moving for high speed printing. At each station, an electronic eye sees its corresponding colored dot, and sends a signal to the controller to print that color on the film. The eye has both its own light source and receiver in the same unit, just a microscopic distance from each other beneath the lens. The eye is small enough to hold in your hand, and is mounted just a few millimeters from the moving film. The light from the eye reflects off the film back to the eye. When the correct color is seen for that print station, the controller initiates the print cycle for that color. If a fiber optic eye is used because of small space, then the eye is mounted elsewhere with a fiber cable that is one to two feet in length. The tip is held in a small clamp. The light exits the fiber tip and reflects off the film back to the fiber tip and to the remote eye. Fiber optics is 8 | highTECH NEWS | NOVEMBER/DECEMBER 2022 more expensive, but allows for a much smaller space at the detection site. When the label area reaches the next print stage, another color is printed. Having different print stages allows for very fast printing at high volumes to avoid the machine having to stop. If the timing is off, one or more of the colors may be off-center. The eyes and controller provide for precise multi-color printing of each color in its required space. Color registration marks have also been printed along the edge of the film at equal distances for the packaging machine to have correct timing when processing each candy bar. The finished roll may be 100 feet or longer, and is now ready to ship to the candy factory. THE PACKAGING PROCESS The candy factory mounts the packaging film roll on its packaging machine (See Diagram). The candy bars are on a conveyor machine controlled by electronics to keep the motor speed constant while feeding the bars into the packaging stage. The packaging film is also fed into the packaging stage with precise speed. The speeds of product and film must be in sync. When the electronic eye sees the registration mark, it sends a signal for the controller to initiate the seal and cut cycle. A small heated metal bar comes down to seal the wrapper, and a blade cuts to separate the wrapped bar. The timing must be exact, or some of the wrappers will be off-center, and the bars will be sliced through. The wrapped bar has "end seals" and a seal along the length called the "fin seal." When you look at a wrapped candy bar, you may see both a group of small color dots or patches (for the printing press) and the color registration mark for the packaging machine. The color mark will be a stripe either at the ends or near the middle. You may have to lift the flap to see the dots or mark. ONLINE VIDEOS The diagram shown above is oversimplified, but gives a basic process flow. There are online tutorials, photos and videos of electronic eyes, controllers, printing and horizontal packaging machines. There are some "See It Made" videos that will show the action of both printing and packaging technology. You can now have a greater appreciation for the advanced electronic and mechanical technology that provides the products we use and enjoy every day.   PRINTING & PACKAGING  

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