Take a moment to imagine two rubber balls of identical weight, size and shape. When dropped, one ball hits the floor, bounces high into the air and continues to bounce, over and over again, like the “superball” of your childhood. In comparison, the other ball hits the floor and barely moves from the surface it strikes.
The contrast is simple: one ball continues to transmit the energy and bounce, while the other ball absorbs the energy and does not move. In the second ball, that absorption of energy “dampens” its ability to bounce.
When speaking of engineered polymer solutions, this analogy is a helpful way to visualize their incredible ability to achieve a specific result in plate mounting sleeves and bridges. A unique dampening technology, like that of the bouncing balls, is incorporated into the sleeve. It is found in a single layer, replacing the “foam” expansion layer used in a typical plate mounting sleeve. We’ll talk more about the advantages of this characteristic, but for now we’ll suffice with pressing home the point that it is a big deal for achieving the highest quality from your printing process.
Why? In a nutshell: The energy created/generated by the plate coming on and off impression that would typically contribute to bounce, can now be absorbed instead.
Outer & Inner Layers
Another aspect to notice about these sleeves is the use of epoxy versus urethane. The outer layers of most sleeves are made up of urethane resin, but these specific sleeves are manufactured using an epoxy resin system.
This is important for several reasons, but most interesting is that urethane often absorbs moisture through contact and humidity. Cleaning solvent absorption and exposure to solvent inks can distort urethane, creating a problem that is found in many pressrooms: losing the total indicated runout (TIR) and concentricity of the sleeve. The epoxy resin system found in this distinctive sleeve, however, is not affected by humidity or exposure to solvents and is less affected by changing plant temperatures.
Figure 1 shows a breakdown of the layers as seen in Trelleborg’s Axcyl sleeve:
- The first layer utilizes a technical non-woven fabric, as well as the epoxy resin we spoke of earlier
- The second (or buildup) layer is a honeycomb structure saturated in epoxy. It provides strength while reducing the weight associated with the buildup
- The third layer, or the inner belt material, again has epoxy resin utilized throughout the structure
- The fourth layer provides the sleeve’s unique and proprietary characteristic. It is an energy-absorbing layer that acts the same way as the second of those two rubber balls—It doesn’t bounce, but instead absorbs the energy that would otherwise create bounce on press at higher speeds
- The fifth layer, or inner diameter, utilizes a distinct technical fabric versus the traditional woven fiberglass, lending longer life and durability to the sleeve, especially when paired with the addition of even more epoxy resin. Have you ever trashed sleeves that were in otherwise good condition except for a split on the inside that prevented easy placement or removal from the press? That is one of the reasons for this fabric
How It Works
Let’s gather all the information we just covered into practical application. If you look at Figure 2, you’ll see the print results of a typical sleeve on the left and one with dampening technology on the right. This graphic is a classic example of an image that is prone to bounce issues; one in which you have a solid bar coming on and off compression with a 30 percent tint that runs through the same area. As press speed increases, bounce transmits itself into the print. It is here you can see the bands of increased dot gain throughout that tonal area. With identical press settings and speed, it is clear the elastomer technology reduces bounce and the associated dot gain.
So how does it work? As a combination of pieces working in harmony. This particular technology absorbs the energy created on press, allowing higher press speeds through its exceptionally stable structure. The epoxy resin woven throughout produces longer life and rigidity, and the physical properties of epoxy prevent solvent attacks that change sleeve dimensions and cause print-related issues from the loss of concentricity. In addition, its honeycomb structure reduces weight by up to 30 percent. There is a plethora of other interesting characteristics about these sleeves, like reinforced ends that prevent shock and bumps from abuse on press.
All technology built into these sleeves was designed to add value to converters. But how is that value really created? Well, we understand that quality press components designed to eliminate press-related problems are vital if printers are to achieve their maximum press speeds while still getting the high-quality graphic reproduction they need. Because of this, value is created through increased press speeds and longer life associated with the components being purchased. The speed increase alone provides considerable benefits in regard to printing efficiency.
About the Authors: John Rastetter, VP of sales and marketing at Pamarco, has more than 30 years in the printing and packaging industries. Prior to joining Pamarco, John held various executive positions at some of the leading suppliers to the printing industry, developing and managing sales and service organizations in North America, Asia Pacific and Europe. John has a true appreciation for the global nature of today’s packaging business and its impact on clients. He graduated from Rochester Institute of Technology and is a member of FTA and a contributor to technical articles in various trade journals, and has presented at FTA, AICC and FPPA events.
Damien Letterier, Axcyl sales and application manager, graduated as a mechanical engineer from the INSA, Lyon, France. He has been in the packaging industry for 26 years in various large multinational companies such as WR Grace/Cryovac, MacDermid Graphics Solutions and now Trelleborg in different technical and sales positions. He currently lives in the South of France, where he enjoys gliding and spending time with his wife and four children.