Should I use a one-piece blanket or a two-piece blanket?

A one-piece blanket obtains the desired gauge with one sheet of blanket, whereas the two-piece blanket obtains the desired gauge with two separate sheets of blanket.

Generally speaking, the print quality of a two-piece set-up is superior to that of a one-piece set-up. The two-piece set-up also allows costs savings by providing repetitive use of the underblanket. Through careful and proper use, the press operator can use as many as eight top blankets for every one bottom blanket used. The two-piece set-up also allows for job flexibility. The press operator can customize the underblanket to the top blanket for specific print jobs that require compressibility or a cushion in the printing blanket.

A one-piece blanket is easy to place on the blanket cylinder, however, the print quality produced is generally not as good as the two-piece blanket, therefore, there is a trade-off between the speed of changing blankets versus print quality.

Does my choice of ink affect my choice of blanket?

Infra Red (IR) and Ultra Violet (UV) are the two basic ink groups for plastic container printing blankets. Each is made of different materials, therefore, it is important to match it with the right printing blanket. A wrong match will result in swelling on the face of the blanket leading to poor print quality and premature blanket wear.

IR inks are the industry standard of the plastic container industry. Butyl and Ethylene Propylene (EP) are the only two polymers (rubbers) compatible with this ink. The proper wash must also be used with this ink to ensure good print quality and blanket longevity.

Butyl and EP rubber compounds work well with UV inks, however, their printing life is shorter than certain special nitrile or synthetic based blanket faced rubbers or polymers.

How can I compensate for gauge variation?

Gauge variation can result from three basic sources: the printing blanket, the adhesive tape, and the plastic container. All three sources are subject to manufacturing variations and acceptable tolerances. Mounting the tape to the blanket is a further consideration. Improperly mounted tape on a blanket can result in air bubbles, which can lead to poor print quality and shortened blanket life.

The degree of container thickness variation depends on the manufacturing process. Generally, there is more wall thickness variation in thermo-formed containers than injected molded containers. Also, the larger the container, the more likelihood and degree of wall variation. To compensate, most press operators apply extra print pressure from the blanket to the container, however, this in turn will decrease the print quality and blanket life. Some blankets have a built in cushion to help improve the print quality and press speed.

At Package Print Technologies, our answer to blanket variation is to combine the printing blanket and adhesive tape in our plant. Our skilled production personnel and specialty equipment will ensure good contact between the blanket and tape to minimize the risk of air bubbles. We then cut the blanket to size for both lids and sidewalls. Each piece is checked with a precision micrometer to determine the exact gauge. The pieces are sorted by gauge and bundled into packages accordingly. Each package is labeled by gauge, size, and production date. When the package of blankets arrives in the pressroom, the press operator can be assured of receiving printing blankets with no defects and the same thickness.