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Applications:
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Paper Substrate - All Types
Nu Tech recommends a plate with a Shore A durometer between 50 and 55 when printing on any type of paper substrate with their standard coated cylinders. The cylinder is a Shore A of 42 and they have learned through trial and error that a 10 to 12 point difference in the coating versus plate durometer will assure outstanding print results.
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Unsupported Film & other High Hold Out Substrates
Nu Tech recommends a plate with a Shore A durometer between
60 and 65 when printing on unsupported film or other types of high
hold out substrates with Nu Tech’s PEC HD (High Durometer) coated
cylinders.
This coating is around a 55 Shore A and will deliver the same results as
Nu Tech’s standard coating on paper when matched with a 60 to 65 Shore A plate.
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Plates:
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The most common plate seen in the field among printers with in-house platemaking in North America is the DuPont FAST system and the recommended medium durometer (50-55 Shore A) plate is the DFM. The higher durometer version is the DFH (60-65 Shore A).
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Nu Tech has an extensive background with Flexo plates, both rubber and photopolymer, and are able to share that knowledge with us to help match your plate and application with the right PEC.
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Tape Recommendations:
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Nu Tech offers a 0.005” mounting tape to use with the Nu Tech cylinders. Other tapes which have worked well are the 3M 2205 and Tesa 52916. All tapes have excellent adhesion, but the 3M and Nu Tech tapes have the added ability to release air trapped between the tape and the cylinder. The 3M tape uses channels in the tape and the Nu Tech tape uses perforations in the tape surface.
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The Tesa tape adheres very well to the cylinder, but Nu Tech reports they have noticed that it tends to leave the adhesive on the cylinder when removed, making for a messier clean-up.
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Impression Setting:
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The key advantage of a PEC is to provide a platform for a plate that will allow for impression and absorb vibration that is created in the nip. You can dramatically over-impress the plate to the substrate without the usual negative consequences; haloing, slur, reverse fill in, dot gain, etc. This feature eliminates bounce and removes banding or gear marking while significantly increasing press speeds and reducing make-ready times.
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You want to maintain light anilox-to-plate impression, and retain the ability to apply heavy plate-to-substrate impression. Most operators understand the concept when they see the coated cylinders, but still need reassurance that added impression, plate to substrate, is okay.
(See Impression Setting Tip)
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Anilox Roll:
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A common occurrence when using coated cylinders on press is a significant reduction with ink metering to the plate. We think this is due to the increased plate-to-substrate impression, which allows most of the ink to transfer from the plate.
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Nu Tech reports they have seen printers increase anilox cell count by as much as 30%, and still achieve the target densities. (800 to 1200 line, 1.8 or less BCM) The result is increased plate life, less ink usage, and decreased press down time due to plate cleaning.
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Cylinder Undercut:
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The optimum coating thickness on the cylinder is .750” in diameter. There are minimum cylinder or repeat sizes for every press that are candidates for coating. We prefer to maintain the integrity of the shaft so it will allow a bearing. A bushing or needle bearing may cause drag and you will not fully realize the benefits of the coating.
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Example:
.894 Nu Tech undercut for a 65 tooth cylinder, 8.125 repeat *
Print diameter: 2.5863
-.7500 (0.375” coating/side) x 2
1.8363
-.1440 (0.067” plate + 0.005” tape) x2
1.6923 BCD
*All units in inches
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Tolerance, Registration & Shelf Life:
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These tolerances are within a cylinder, as well as from
cylinder to cylinder.
- Tolerance on outer diameter +/- 0.0005”
- Tolerance on concentricity (TIR) +/- .001”
- Cylindricity .00019” (Cylindricity describes a condition
of a surface of revolution in which all points of a surface are equidistant from a common axis; i.e. roundness)
The polymer used to create the coating is applied as a liquid and
cast in a mold with the base cylinder. After the polymer is cured,
the cylinder is removed from the mold and finished to the published specification through Nu Tech’s proprietary process.
Unlike compressible cushion tape, which contains air, Nu Tech’s coating
is a solid material. Compressible tapes vary in thickness and break down during a press run. As a result, the diameter of the cylinder changes. Nu Tech’s coating reacts as a displaceable, not a compressible, material and consistently prints true print repeat through the nip. An analogy Nu Tech uses is: Picture it as a bulldozer tread. It can run over an uneven surface, over rocks, but the length of the tread impression does not change. The coating allows the plate to conform in the printing nip and print its true length.
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Nu Tech does not recommend that you mix and match these cylinders with traditional hard cylinders mounted with cushion tape for process work. They have several customers who use these cylinders to print a background screen or vignette, and use their traditional cylinders for the other spot colors. As a rule of thumb, if the trap is less than .012 (.012 ÷ 3.1416 or around .004), Nu Tech does not recommend mixing and matching.
Shelf Life: Do not store coated cylinders on their side because they will eventually take an impression set. Nu Tech has had the product at some of their beta test sites for more than 3 years and have not had any issues with shrinkage or other changes to the coating. The polymer is fully cured when it leaves the factory.
The coating carries a one year limited warranty.
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If you need technical support or would like to place an order, call FlexoDepot.com toll-free at: 1-866-416-1484
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