The Role of Novel Solutions for Higher Performance and Longer Lasting Fusing Solutions

Abstract

As the demand for economical, sustainable, and innovative printing technologies soars[1], business and operational efficiencies require higher performance and longer-lasting fuser rollers to reduce machine downtime and extend longevity. This growing demand has challenged fusing product developers and manufacturers to discover novel material and construction approaches that outperform existing state-of-the-art technologies. These novel solutions are critical for helping organizations with high-speed printing and copying capabilities enhance their productivity and profitability.

Introduction

High-speed digital printing and copy applications push elastomeric fuser rollers to the limits of their functional capabilities. High dynamic stress at high temperatures challenges even the most advanced elastomer.

Mechanical wear at high temperatures drastically reduces fuser roller stability and performance, resulting in:

• Printing defects, such as streaking, black lines, double images, spots, and smudging
• Paper jams or wrinkling from separator finger toner build-up, wear, and breakages
• Chirping, screeching, or grinding noise from excessive gear wear
• Machines that stop working because they’re plugged with strips of roller coating or have toner build-up

However, novel elastomer technology solutions blending high-performance fusing materials and advanced product construction are the key to maximizing output and minimizing long-term costs.

This white paper will guide you through the scientific and technical process for developing innovative, high-performance, and long-lasting fusing solutions to meet today’s soaring demand. It will also include a case study with the step-by-step development process to illustrate the far-reaching impact of a novel development and manufacturing solution.

Before outlining the novel solution development process, thoroughly examining the problems causing premature fuser roller failures is essential. Next, we’ll discuss these primary causes and how a fuser roller’s materials and construction can contribute to the decline.

Primary causes of fuser roller failure

The mark of a high-performance and long-lasting fuser roller is its stability while in use. If they can resist stability problems when subjected to continuous high temperatures and high cyclic stress, they are more likely to satisfy performance objectives, and we’d expect the roller to have a long and useful life.

However, fuser rollers destined for premature failure are likely to exhibit the destabilizing effects of mechanical and thermal fatigue over time, significantly reducing their useful life. The following are some of the primary causes of premature failure.

Degradative weight loss

Under high-temperature conditions and significant cyclic stress, most fuser roller base cushion layers can exhibit some degradative weight loss without considerable consequences. But when the weight loss becomes significant over time in use, the effect can decrease fuser roller performance and shorten the lifespan.[2]

Loss of peel strength

Peel strength refers to the adhesive strength of a material or the strength of the adhesive bond between two materials.[3] Multi-layer rolls can lose peel strength when exposed to high temperatures and cyclic stress. As a result, the coatings can fail by peeling off their underlayer in sheets, potentially plugging paper paths with coating strips and stopping the machines.

Permanent deformation

High-speed printing parts are prone to deformation when working at high temperatures over a long time, causing machine faults like paper jams and angle folding.[4] For instance, when the pressure roller shape is crown, concave, or another non-cylindrical surface geometry, the fuser roll can permanently deform and conform to the pressure roll’s shape, reducing or losing the benefits of the pressure gradient.

Changes in hardness

Finally, mechanical wear at high temperatures can change a fuser roller’s hardness or elastic storage modulus, which is the ratio of elastic stress to strain.[5] Storage modulus indicates a roller material’s ability to store energy elastically, potentially forcing the abrasive particles radially and affecting the roller’s structure, performance, and lifespan adversely.

Fusing roller materials and construction must provide suitable resilience, peel strength, and hardness to avoid premature failure from degradative weight loss, loss of peel strength, permanent deformation, changes in hardness, and other failure-causing instabilities. Achieving these goals requires a comprehensive, novel, and application-specific development process focused on the technical requirements for a high-performance, long-lasting fusing solution.

The novel solution development process

Crafting novel solutions for high-performance and long-lasting fuser rollers is highly scientific and technical. At the Torrey Pines Research 2^nd Color Electrophotographic Printing Technology Seminar, organizers described the physics of fusing as complex, requiring an understanding of a vast array of disciplines and concepts[6], including mechanical engineering, chemistry/organic chemistry, heat transfer, paper handling, temperature control systems, toner colorimetry/light transmission, toner rheology/viscoelasticity, toner flow, roller coating technologies, fluid coating/fluid splitting, mechanics of conformable nips, and high-performance elastomers designed for high temperature and stress.

Developing novel fusing technologies is a process that centers on a host of considerations, including fuser roller construction, performance, physical characteristics, environmental conditions, and the moving material.

Construction considerations

Single or multi-material rollers that include more than one elastomer with or without adhesives or coatings dramatically influence performance and longevity, making it a critical part of the solution development process.  

• Single material – Silicone, fluoroelastomer, fluoropolymer, EPDM, polymer blends, etc.
• Multi-material – Multi-layer silicone/fluoroelastomer, multi-layer silicone/fluoropolymer
• Multi-material with adhesives or coatings – non-stick, PTFE, etc.

Performance considerations

A fusing roller’s wear resistance, coefficient of friction (CoF), heat resistance, abrasion resistance, and thermal transfer properties can also influence performance and longevity in high-temperature and cyclic stress environments. The following are a few of the performance considerations when developing novel fusing solutions:

• Wear resistance – High mechanical and thermal strength can help avoid degradative weight loss, loss of peel strength, permanent deformation, and hardness changes.
• High CoF – CoF is the ratio of the frictional force resisting the motion of two surfaces in contact to the normal force pressing the two surfaces together.[7] Fuser rollers with sustained high CoF allow them to function optimally in high temperatures with high cyclic stress.  
• Heat resistance – Fuser rollers with high heat resistance allow them to maintain performance despite prolonged exposure to high temperatures of modern high-speed digital printers and copiers.
• Abrasion resistance – Higher abrasion-resistant materials extend the useful life of the roll and reduce debris caused by deterioration of the pressure roll.[8]
• Thermal transfer – High heat transfer properties can help increase production throughput and reduce the processing speed for higher performance and longer-lasting fuser rollers.

Physical characteristics

The roller’s physical characteristics, such as size, hardness, material, release properties, and surface roughness, can also affect performance and longevity when exposed to elevated temperatures and stress. When developing a fuser roller, the following characteristics dictate its suitability in an application environment.

• Outer diameter
• Core diameter
• Length
• Material hardness
• Elastomer material
• Release properties
• Surface roughness
• Chemical exposure resistance

Environmental considerations

A facility’s environment can significantly affect the materials and construction of a fuser roller to ensure they can withstand conditions and factors, such as:

• Temperature
• Humidity
• Liquids
• Chemical exposure

Moving material

Paper, plastic, glass, wood, food, or other moving materials are another critical consideration when developing and manufacturing high-performance, long-lasting fuser rollers that last in high temperature and stress applications.

This vast set of development considerations illustrates the importance of devising novel fusing solutions to maximize performance and longevity when exposed to the rigorous temperature and stress of today’s high-speed digital printing and copying machines.

Case study: The novel approach to developing Xerox fuser rollers

Xerox’s continual desire to maximize the performance and life of its rollers to reduce service time led them to seek a novel fusing solution that would become its signature workplace technology victory. Their goal was to minimize premature failures, enhance fuser roller performance, and promote longer roller lifespans.

After an intensive development process involving a contracted team of chemists, engineers, manufacturing experts, and elastomeric experts, Xerox began implementing an innovative and long-lasting fusing solution to achieve more than a million copies per roll.

However, the result was not without challenges.

Project challenges

• Non-cylindrical surface geometry – The surface geometry of Xerox’s fuser rollers was not cylindrical. Instead, its geometry is crown or concave depending on how it deflects, creating challenges with the roller sleeves.
• Oil absorption – Silicon is an excellent base layer roller because it is soft and compliant. However, it’s also prone to oil absorption, which could compromise the roller’s performance. As a result, the surface required treatment to prevent it from absorbing oil.
• Silicon base layer thickness – The soft silicone substrate needed not to be so thick as to sacrifice compliance.
• Toner affixation – Another challenge was to ensure the necessary surface energy so that the toner only lands on the paper and not the roller. Otherwise, the result is hot offset printing, where the first roll will impart a shadow image onto the next print.
• Roller thickness – Xerox proposed thickening the fuser rollers to help increase their lifespan. However, if the roller is too thick, it can burn up and crack, requiring attention to achieve the precise thickness to transfer heat as quickly as possible.

Project solution

After addressing all the project considerations and challenges, the ideal fusing solution for Xerox was a patented novel spray process[9], where the fuser member has three parts:

• An aluminum core
• A compliant silicone rubber base layer bonded to the core
• An outer fluoropolymer non-stock top coating

While constructing a fusing member with a non-stick material as a top layer and a heat-resistant base layer has been known in the reprophotographic art, the novelty of this process combines the non-stick properties of fluoropolymer resins and the compliant properties of silicone elastomers. This combination helps resist oil absorption, silicone swelling, and susceptibility to mechanical damage, such as print media or pricker finger abrasion and hardened toner that accumulates in the system.

In the following five-step process, Xerox’s fuser roller manufacturing processes included molding, grinding, reheating/sealing, top layer application, sintering, and final polishing:

1. Clean and degrease the aluminum insert’s surface and apply a spray-on silicone rubber primer.
2. Fabricate the fuser roll by liquid injection-molding a silicone compound onto the prepared aluminum insert.
3. Preheat the primed silicone base layer in an infrared oven to dry completely, remove low molecular weight fractions, and transform the primer layer into an oxidized state.
4. Apply a primer to the prebaked rubber and allow it to dry completely.
5. Spray on fluoroelastomer topcoat, a blended primer of silane and a polyamide resin

Results

Before the novel silicone and fluoroelastomer spray-on fusing technology solution, Xerox didn’t have a long-life fuser roller. After this discovery, Xerox fuser rollers can produce over a million copies, with some exceeding 2.6 million copies.

For several decades, Xerox has used these high-performance, long-lasting fuser rollers in its high-speed copiers in hospitals, building centers on Wall St., and even the Screen Actors Guild (SAG).

Summary

In this white paper, we set out to explain the importance of developing novel fusing technologies rooted in scientific and technical principles to promote optimal performance and longevity for maximum productivity and profitability. Competing in the in-demand digital printing and copying space requires machine components developed with exceptional innovation and skill. Contracting with a leader in developing and manufacturing fusing products for today’s high-speed digital printing and copying machines can give companies the novel solutions required to gain a competitive edge.

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[1] Research News & Markets, Global Digital Printing Packaging Market (2022-2027) – Increasing Demand for Flexible Packaging is Driving Growth, PR News Wire, 6/21/22

[2] John J. Fitzgerald, Wayne T. Ferrar, Tonya D. Binga, and John R. Babirz, Fuser Roll for Fixing Toner to a Substrate, Google Patents, 1992

[3] Min Wang and Chong Wang, Bulk Properties of Biomaterials and Testing Techniques, Reference Module in Biomedical Sciences, Encyclopedia of Biomedical Engineering, Science Direct, 2019

[4] Pingping Liu, Fangjun Zuo, Rui Su, et al., Structural Response of an Injection Molding Part of the Fuser Mechanism in Laser Printer Under Thermomechanical Coupling, SAGE Journals, 4/29/19.

[5] Mohd Hanafee Zin, Khalina Abdan, and Mohd Nurazzi Norizan, Structural Health Monitoring of Biocomposites, Fibre-Reinforced Composites and Hybrid Composites, 2019

[6] David Thompson, Xerox and Dinesh Tyagi, Eastman Kodak Company, T14 Fusing Technologies and Toner Materials Relationships, Society for Imaging Science and Technology NIP 24: 24^th International Conference on Digital Printing Technologies, 9/8/2008

[7] Editors of Encyclopedia Britannica and Erik Gregersen, Coefficient of Friction, Physics, Encyclopedia Britannica, 6/24/20

[8] Xerox Corporation, Pressure Roll for Fusing Operation, Justia Patents, 11/7/05

[9] Timothy D. Marvil, Chris F. DelRosario, Stace Moss, John Navarra, and Orville R. Raabe, Jr., Multilayer Fuser Rolls Having Fluoropolymer Coating on a Compliant Base Layer and Method of Forming, United States Patent and Trademark Office, 7/22/03