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PRINTING BLANKETS -- Got Ya Covered

October 2002

Circle 375 on Reader Service Card

From Reeves Brothers, Vulcan 2000 Plus and Vulcan 2000 Plus SR printing blankets offer good resistance to gauge loss and feature excellent dynamic mechanical properties for sharp dot reproduction. They transfer ink efficiently with low levels of distortion. Vulcan blankets assure exceptional web or sheet release and consistent, accurate gauge. Benefits of this line include improving smash resistance and service life; allows users to print closer to the gap, while eliminating sinking; requires less retensioning; and reduces slippage on the cylinder and at the printing nip.

Circle 376 on Reader Service Card

The Gerber Innovations Sector automatic coating blanket cutter offers an entirely new approach to producing coating blankets, making coating blanket preparation an integral part of a prepress workflow. Coating blankets produced on the Gerber Sector provide coating accuracy exceeding that with hand-cut blankets, and ensure proper registration with printed images. Perhaps most important, the Gerber Sector reportedly provides a speedy and verifiable return on investment.

Circle 377 on Reader Service Card

For more information on printing blanket manufacturers, use the reader service card in this issue, refer to our July Master Specifier issue, page 50, or visit www.piworld.com/doc/masterspec.html


GATF Examines Blankets

According to a new original research study on blanket variables, proper torque affects print quality the most. In cooperation with seven blanket manufacturers, the Graphic Arts Technical Foundation (GATF) conducted the study of various blankets and their effects on print quality and sheet movement to promote product development and printer awareness.

Blanket Study

The Offset Blankets, Print Quality and Sheetfed Movement study examined 12 blankets, all used in print runs under the same conditions at GATF. Press, paper, ink, fountain chemistry, speed, plate and temperature were identical. In the first print run, GATF's press operators carefully used a torque wrench. Although suppliers recommend a variety of torque settings, all blankets were tensioned to 38-foot pounds—an acceptable middle ground torque.

Also, all blankets were printed at 0.006˝ squeeze between the plate and the blanket. GATF's second shift press operators were then asked to print two of the blankets without a torque wrench or packing gauge. Twenty random samples were pulled for print attribute measurement, and 30 consecutive sheets were measured with the Mitsubishi Digital Register Analysis—a machine vision system that carefully measures relative position of triads of dots.

The findings showed that print attributes are only slightly affected by the blanket, all other things being equal. Results regarding sheet movement were inconclusive and may be a topic for a future study. However, torque setting greatly affected tone value and could be used as another tool to control and adjust the process.

GATF also explored several blanket issues with the participating blanket manufacturers. Representatives who troubleshoot problems discussed customer feedback regarding packing latitude, blanket life, printer expectations, torque and packing frequency among printers, and the effect of blanket washing on blanket life. Interestingly the manufacturers estimated that only 10 percent to 50 percent of printers even use a torque wrench when fastening the blankets.

Comparing Printability

In comparing the printability of different blankets with all other conditions equal, Offset Blankets, Print Quality and Sheetfed Movement also documents trapping and print contrast, discusses sheet movement from unit to unit affecting tone value, and shows the effect of various blankets on printing solids and halftones.

While preliminary results were reported at GATF's TechAlert conference in January and at the Technical Association of the Graphic Arts (TAGA) conference in April, a full report is now available. Offset Blankets, Print Quality and Sheet Movement is the latest study in a series of Research and Technology Reports (RTR) published by the GATF. As an independent, third-party organization, association reports are objective and original research studies. Methodology is also described in all reports.
 

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