Narrow web offset (on)

Offset printing provides another printing effect for manufacturers and their customers to evaluate and select. This process differs from flexo printing in that print quality is often useful in an image-oriented industry.

Offset printing and flexo printing can also be used for label production, but in different ways. Although the use of flexo printing is more common among narrow manufacturers, offset printing has its own advantages and disadvantages. One of the advantages of offset printing is that quality is usually better than flexo printing, and it has become increasingly demanding in a market that is dedicated to satisfying excess demand from customers.

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Offset uses a more sophisticated system to transfer ink to the substrate: a long ink cart consisting of many rollers. In contrast to a flexographic plate, the front of the offset plate is the desired printed image. In offset printing, a roll containing an offset printing plate conveys ink to a blanket, a roller having a rubber layer. The desired print image is on the opposite side of the blanket. The blanket then conveys the ink to the substrate, printing the desired image directly on the substrate.

Flexo printing uses inks, just as human consumption of milk must last for long. Nylon or plastic offset plates directly draw ink from ink plates. The ink is delivered directly to the substrate or paper. Offset ink is a paste ink, a heavier weight ink. Need to use a more sophisticated system to make it flat. It is guided by an aluminum printing plate and transferred to the blanket material. The blanket conveys the ink to the substrate. ”

The maximum precision of flexo printing is 170 to 180 dpi, while offset printing can reach 200 to 350 dpi. Therefore offset printing is much simpler and less expensive than flexo printing. However, UV drying must be used in offset printing. In flexo printing, either hot air or UV drying can be used.

The ink flow rate is another aspect of flexographic and offset printing. The ink flow in flexo printing is controlled by the ink volume of the anilox roller. This factor is selected based on the surface of the paper and the desired printed image. The ink flow during offset printing is controlled by screws (also called buttons) in the ink reservoir. The button adjusts the amount of ink allowed to enter the ink cart for the substrate.

If a locking system is used on the offset printing plate and a mounting device with a camera is used on the flexographic printing plate, the flexo and offset printing preparation time is the same. Both technologies print at the same high speed, about 100 to 200 meters per minute (1000 feet per minute).

The advantages of offset printing

The most commonly mentioned advantage of offset printing is better print quality. On every inch of print, offsets have more dots and more uniform optical density than flexo.

The print quality with respect to the accuracy of the flexographic printing surface can usually be seen from 3% to 98%, while the offset printing is better, and can reach 0% to 100%.

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Offset printing has a greater advantage in the start-up cost of a new project; the cost of offset printing is very low compared to a flexo or gravure cylinder. At the same time, the average production time of the offset printing plate is only 10 minutes, which is surprisingly short compared to flexo printing. This means that you can start a new project immediately.

Easy to operate is another benefit. Jakob Landberg, director of sales and marketing at Nilpeter, the world's leading narrow-web printer manufacturer in Slagelse, Denmark, explained that "I usually say that even a sloppy printer can print excellent quality on offset printing - but In flexo and UV flexo, you have to do 100% of your best.” He also said that the offset press has a high degree of continuity and is ideally suited for repeated singles and long singles.

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Nilpeter MO line combined presses (free combination flexo, offset, gravure, silk screen, hot and cold stamping units)

Flexo printing needs to separate many color points. In offset printing you can print 10% black silkscreen and dark black text on the same plate. This means that the eight-color flexo press is just a five-color or six-color offset press. Installation time is reduced at the same time. Instead of changing eight colors, you only need to replace one or two special colors.

challenge

No perfect process, offset printing is no exception.

The challenge is how does your printer better control the press? This process is different from flexo printing and requires some people to get used to it. This is a definite learning curve, but if there is good training then there will be no problems.

The second challenge is to use offset technology on flexible, non-absorbent substrates such as plastics, polyolefins, or self-adhesive substrates. The disadvantage of web offset printing is that the print size is fixed.

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Print cylinders with printing unit inserts corresponding to other print lengths are a viable option but they are relatively expensive. ”

Another way to solve the problem is to use half-rotation technology, also known as intermittent feed. On offset presses that use half-rotor technology, the substrate does not move forward. It will move back intermittently so that blank areas can also be used for printing to reduce waste.

The drawback of half-round technology is slowing down. In intermittent motion, the speed of the press is limited compared to rotary presses. Our maximum speed is 150 feet per minute. This technique is very suitable for short and medium singles. Because the task change becomes more flexible than on a rotary press. When you have to print 10 tasks, each with 20,000 labels, speed is not the most important factor. Task replacement is a more basic principle. The third possible solution is to use a sleeve with a fixed print size. For 10 years, web offset printing has not attracted the attention of flexible packaging and label manufacturers, because you have to change a whole set of printing unit plug-in (heavier and more expensive) to change a repeat length. When the new technology is introduced, you only need to change two lightly loaded sleeves to change the length of a repeat. This has made flexible packaging and label manufacturers who need repeat lengths in production to begin to become increasingly interested in offset printing.

Some of the challenges of offset printing may be mostly the expectation of increasing perfection. Customers expect better quality, so better quality is needed. Everyone spends more time installing it to ensure quality.