Roll Cover Research Articles

Optimization Procedure and Toolchain for Roll Dynamic Geometry

In rolls manufactured from first bent and then welded sheets of steel, the asymmetric distribution of mass due to the weld seam as well as imperfections of the geometry due to the bending may cause the roll cross-section roundness profiles to deform due to centrifugal forces when the roll is accelerated to rotate at its operating speed. This effect is known as the dynamic geometry of the roll. In previous research, it has been shown that it is possible to measure the dynamic geometry in operating speed and compensate for the deformation by grinding a suitable opposite geometry on the roll. This direct approach may work when only little material is removed. Such conditions apply especially for polymer coated rolls, where the dynamic geometry is mostly dependent on the geometry of the much stronger and denser steel body under the roll cover. This paper goes further to investigate the possibilities for compensating the dynamic geometry in cases where the amount of removed material is significant enough to have an effect on the dynamic geometry itself due to altered mass and stiffness. The paper presents a toolchain consisting of a parametric roll CAD model, finite element simulation of the dynamic geometry and a geometry optimization procedure based on minimizing a target function describing roundness errors in cross-sections of the roll. Results of simulation experiments for a case example indicate that the presented optimization procedure can be used to eliminate roundness errors related to dynamic geometry of the roll. Finally, the paper discusses the application of such a toolchain in the manufacturing of rolls.

ESTIMATION OF HARD PLAIN RUBBER ROLL MANUFACTURING PROCESS TIME USING LINEAR REGRESSION METHOD

Competition in the industrial world today requires producers to compete in providing good quality products with short production times and relatively low production costs. This relates to production machines which have an important role to produce products with good quality. PT. Voith Paper Rolls Indonesia is a service and manufacturing company engaged in roll repair and manufacture of roll cover materials. One of the production processes carried out during roll repair is the turning process which is carried out twice. In the turning process, there is often a significant time difference between the actual time and the estimated time obtained from the existing formulation. Therefore, this report will focus on efforts to improve the calculation formulation for the estimation of turning process time on lathe A on hard plain rubber roll by analyzing the effect of surface area on processing time using a simple linear regression method through the IBM SPSS application.

Temperature profile measurement applications of moving webs and roll structures with intelligent roll embedded sensor technology

An intelligent roll for sheet and roll cover temperature profiles is a mechatronic system consisting of a roll in a web handling machine that is also used as a transducer for sensing cross-machine direction (CD) profiles. The embedded temperature sensor strips are mounted under or inside the roll cover, covering the full width of the roll’s cross-dimensional length. The sensor system offers new opportunities for online temperature measurement through exceptional sensitivity and resolution, without adding external measurement devices. The measurement is contacting, making it free from various disturbances affecting non-contacting temperature measurements, and it can show the roll cover’s internal temperatures. This helps create applications that have been impossible with traditional technology, with opportunities for process control and condition monitoring. An application used for process analysis services without adding a roll cover is made with “iRoll Portable Temperature” by mounting the sensor on the shell in a helical arrangement with special taping. The iRoll Temperature sensors are used for various purposes, depending on the application. The two main targets are the online temperature profile measurement of the moving web and the monitoring of the roll covers’ internal temperatures. The online sheet temperature profile has its main utilization in optimizing moisture profiles and drying processes. This enables the removal of speed and runnability bottlenecks by detecting inadequate drying capacity across the sheet CD width, the monitoring condition of the drying equipment, the optimization of drying energy consumption, the prevention of unnecessary over-drying, the optimization of the float drying of coating colors, and the detection of reasons for moisture profile errors. This paper describes this novel technology and its use cases in the paper, board, and tissue industry, but the application can be extended to pulp drying and industries outside pulp and paper, such as the converting and manufacture of plastic films.

Who Did It First: Great Pop Cover Songs and Their Original Artists BobLeszczak. Lanham, Maryland: Rowman & Littlefield, 2014.Who Did It First: Great Rhythm and Blues Cover Songs and Their Original Artists Bob Leszczak. Lanham, Maryland: Rowman & Littlefie

Who Did It First: Great Pop Cover Songs and Their Original Artists Bob Leszczak. Lanham, Maryland: Rowman & Littlefield, 2014.Who Did It First: Great Rhythm and Blues Cover Songs and Their Original Artists Bob Leszczak. Lanham, Maryland: Rowman & Littlefield, 2013Who Did It First: Great Rock and Roll Cover Songs and Their Original Artists Bob Leszczak. Lanham, Maryland: Rowman & Littlefield, 2014Bob Leszczak has delivered three marvelous books that capture much of the history of American popular music over the last seven decades. As the titles indicate, these books are organized around the concept of one singer or group recording (or covering) a song that had already been recorded by another singer or group. Covering is quite common in the music business, and it takes many forms. It could be the hit of an original artist recorded by a subsequent artist who might have as big or even a bigger hit than the original artist. Or it can be a song that initially did not have much commercial success but was taken by another performer- to-hit status. There are many stories associated with cover songs, and Leszczak seems to know close to all of them.One of the more unusual covers-at least in the sense of commercial success (or lack thereof) and history-is Elvis Presley's recording of Mystery Train. Presley's rollicking ride on that train long ago entered the annals of rock history as a masterpiece, and he would still be performing it in concert in the 1970s. The song was written by Little Junior Parker and recorded by Little Junior's Flames in 1953 for Sun Records. The original version was a minor regional hit but did not chart nationally. Elvis would record it for Sun Records in 1955 in what would be his last release on the Sun label. Elvis's rendition also would be a regional hit that did not chart nationally. Nor would its RCA single re-release in 1956 hit the national charts. So here we have a legendary song given a legendary performance by a legendary artist, and neither this performance nor the original enjoyed commercial success in the typical use of that term.In these books, Leszczak discusses 1,173 songs that have been covered. They go as far back as at least 1928 (Al Jolson's My Mammy covered thirty-nine years later by The Happenings), although most are from the 1940s on. More than these 1,173 songs, however, are discussed. Leszczak often takes the opportunity to discuss other songs related to the artists or to the covered song at hand. He also discusses other notable covers (often album cuts) of the song being discussed. These discussions are uniformly informative and interesting. The breadth of Leszczak's knowledge is so great that even the most informed reader will likely come away thinking on more than one occasion, I did not know that.These books are well organized, and everything is readily accessible. At the beginning of each book, there is an alphabetical listing for each song, e.g., Act Naturally by Buck Owens before The Beatles. …

Reverse roll-coating flow: a computational investigation towards high-speed defect free coating

A finite element Taylor–Galerkin pressure-correction algorithm is employed to simulate a high-speed defect-free roll-coating flow, which substantiates a coating process with a free meniscus surface. Findings are applicable across a wide range of coating sectors in optimisation of coating performance, which targets adaptive and intelligent process control. Industrially, there is a major drive towards using new material products and raising coating line-speeds, to address increased efficiency and productivity. This study has sought to attack these issues by developing an effective predictive toolset for high-speed defect-free coatings. Here, time-stepping/finite element methods are deployed to model this free-surface problem that involves the transfer of a coating fluid from a roller to a substrate (of prescribed wet-film thickness). This procedure is used in conjunction with a set of constitutive equations capable of describing the relevant fluid-film rheology in appropriate detail. Quantities of pressure, lift and drag have been calculated streamwise across the flow domain, and streamline patterns reveal a large recirculating vortex around the meniscus region. Such pressure distributions across the domain display a positive peak which decreases as nip-gap size increases. Further analysis has been conducted, mimicking the presence of a wetting line, whilst varying boundary conditions at the nip. Observation has shown that such inclusion would serve as a relief mechanism to the positive peak pressures generated around the nip zone. Here, through an elasto-hydrodynamic formulation, the elastic deformation of a rubber roll cover (elastomer) has also been introduced, which offers fresh insight into the process with respect to nip-flow behaviour, and allows for the analysis of both positive and negative nip-gaps.

Polymer cover induced self-excited vibrations of nipped rolls

As a result of increased speeds, the dynamic instability of rotatory machines including polymer-covered nipped rolls has grown. The instability originates from the viscoelastic behavior of the covers and leads to strong barring vibrations, which limit the operating speed of many machines. In this work, the self-excited vibrations of a nipped two-roll system with a polymer cover on the other roll are investigated using an analytical model developed for the roll system. The viscoelastic properties of the cover are accounted for by the standard linear solid (SLS) model. The numerical results display wave-like roll cover deformation patterns, separate instability regions of the system and moving wave patterns near the resonances. The roll system is unstable when the excitation frequency of the polygonal cover deformation lies in the vicinity of the higher eigenfrequency of the system. By using a speed-up ramp, it is shown that at high speeds the instability regions may become too wide and unstable to be crossed in industrial machines. An experiment was carried out, and a good agreement is found between the numerical and experimental results.

Eric Olson

In his classic fable, The Gnat and the Bull , Aesop (620 BC–560 BC)—that astute observer of human nature—teaches us the sad reality that the smaller the mind, the greater the conceit. One of the things I like about Eric Olson is that he embodies the notion that a truly great mind is free of conceit. Although he is one of the most successful scientists of our time and despite his extraordinary accomplishments and recognitions, Eric has managed to keep a simple, warm, genuine, down-to-earth style. I find this to be overwhelmingly refreshing, and almost as admirable as his scientific prowess. I hope the readers will enjoy this foray into the human dimension of Eric’s rich and well-rounded personality—his life-long passion for science, his work ethics, his love of music, his views on science and faith, his concern for those who entrust their career to him, and his total lack of arrogance. Eric is one of the best role models for young investigators to emulate, not only from a scientific but also from a human standpoint. Although now he is a veritable icon in cardiovascular research, he tells us that it was not easy to get to that point. This should be a good lesson for others. Indeed, it is never easy in science, for anybody. I hope that those who are at the inception of their careers will be inspired by reading how Eric overcame initial challenges and developed a stunning upward trajectory using the old-fashioned (and irreplaceable) virtues of hard work and perseverance. — —Roberto Bolli Eric Olson, Professor of Molecular Biology at the University of Texas Southwestern, Dallas, Tex, knows how to build muscle. Indeed, he has been studying muscle development since he landed his first faculty position in the mid 1980s. Since that time, Olson and …

New approach to the evaluation of the free surface position in roll coating

This paper deals with an industrial three rolls coater. The behaviour law of the elastomer roll cover in different environments is first established in order to be taken into account in the numerical simulation of the process. Cyclic compression tests are performed and compared to the corresponding numerical simulation to precisely determine the viscoelastic parameters. With the identified parameters, a finite element simulation of the process is then performed to evaluate the meniscus stability in real contact conditions. The influence of the determined elastomer behaviour laws on the free surface position is discussed.

Insects in Rock and Roll Cover Art

Insects in Rock and Roll Cover Art

Effect of thickness and viscoelastic properties of roll cover on deformable roll coating flows

Roll coating is distinguished by the use of one or more gaps between rotating cylinders to meter a continuous liquid layer and to apply it to a flexible substrate. Of the two rolls that make a forward-roll coating gap, one is often covered by a layer of deformable elastomer. Liquid carried into the gap develops high enough pressure to deform the resilient roll cover. The complete understanding of the coupling between the liquid flow and roll cover deformation is vital to the optimization of this widely used and simple coating method. Most of the earlier works on deformable roll coating analyzed the action with both the lubrication approximation and the full Navier–Stokes solution of the liquid flow, and one-dimensional elastic models of the roll cover deformation. The effect of the roll cover thickness was not explored and can explain some of the discrepancy observed from the available theoretical predictions and experimental measurements from different researchers. Moreover, rubber and rubber-like materials used as roll covers do not behave purely elastically. Their responses depend to a great extent on the stress history and the temperature of the roll cover. In this work, the flow between a rigid and a deformable rotating roll was examined by solving the complete Navier–Stokes system coupled with a plane-strain elastic and viscoelastic model of the roll cover deformation. The stress at each location of the roll cover was evaluated by an integral of the deformation along the material path of the point being analyzed. The equation system was solved by the Galerkin/finite element method. Results show how thickness of the roll cover and its viscoelastic properties affect the performance of deformable roll nips.

A torque-based analysis of the reverse roll coating process

In a laboratory film coater operated at industrial speed, the torque exerted by the metering rod was used to investigate the hydrodynamics in the metering nip flow. CFD simulations were also performed taking into account the deformation of the roll cover to depict the elastohydrodynamics of the metering nip flow. From the experiments, it was found that the torque increases with transfer speed, load and viscosity. When runnability problems such as spitting were observed, the torque signal decreased. Torque measurements could also predict excessive friction between rod and roll, which may damage the elastic cover. The numerical simulations showed trends similar to the experiments. Regions of positive and negative torque values demonstrated how the fluid interacts with the rod, a phenomenon apparently related to the occurrence of secondary flows in the metering nip. Finally, the numerical results also showed that the minimum nip gap becomes constant at high loads.

Media/Toner Interactions in Laser Printing

According to CAP Ventures, monochrome Print-on-Demand (POD) book publishing is currently a 10 bn industry growing at a rate of 10% each year. Such POD and other electro-photographic applications demand an exceptionally high degree of print resolution as well as good toner adhesion. Controlled particle size distribution of the toners, higher print speeds, and other advances in color laser printing are also placing special demands on the media used for printing. This paper attempts to separate the effects of three different fuser roll cover materials, which impact the nip dynamics, to the print resolution and uniformity as well as the toner adhesion to the substrate. The toner adhesion was characterized by Scanning Electron Micrographs (SEM's). A model has been developed to estimate nip residence time for the fuser roll covers. As shown in the model, this parameter can be affected both by roll cover design as well as print speed. In this limited study where the print speed was held constant and the nip residence time changed only due to roll cover design, it was shown to correlate well with print resolution as measured by image analysis techniques.

A Study on the set seven roalls of the Saddarma Pundarika Sutra Prayed by Yeom Seong-Ik and Script Center

In this paper the characteristics of the script centers golden and/or silver letter center in Koryo Dynasty and a set of seven rolls of the script written in silver letter on blue paper prayed by Yearn Seong-Ik were studied with focusing on the referred records and an epilog of the script. This script was discovered from Namgewon's stone stupa, when it was transported from original site of Daekam Dong, Kaiseong city to Kyungbok Palace in 1919. This script prayed by Yeom Seong-Ik which was written in silver paste on blue papers is a set of seven rolls, the size is 31.1 cm (length) 27.2 cm (width). The cover painting and Beonsangwha(Buddha's preaching picture) were painted out and in the roll cover. This script was written with 14 letters on a line whose characteristic with the style of cover painting and Beonsangwha is similar to the golden and silver scripts prayed by kings of Koryo Dynasty. The person who prayed this script was a powerful vassal of the king Chungyeol period, Yeom Seong-Ik. According to Koryosa(Koryo History) and Koryosa jeolyo(summarized Koryo History), it is described that Yeom Seong-Ik offered his own house which was built by a group of strangers as a 'Writing Place for the complete collection of Buddhist Sutras and the place of the script of the complete collection of Buddhist Sutras. Therefore, it is possible to consider that this script a set of seven rolls of the script of Saddharma Pundarika-Sutra was written to pray for himself as well as his families' fortune at the place of golden script of the complete collection of Buddhist Sutras, and enshrined it in the Namgaewon stone stupa when the stupa was repaired in 9th year of king ChungYeol. Above all the most important point should be centered on that he offered his house as a writing place for golden script of the complete collection of Buddhist Sutras as recorded in Koryosa Jeolyo. The writing place for golden script of the complete collection of Buddhist Sutras should be emphasized on the meaning of its site. It is an important key point to clear that Kumjawon(Golden letter center) would be different from Kumjadejangso(the writing place of golden script for complete collection of Budihist Sutras) with Kumkyungsa(Goldm script place). As considereing the point that this script showed the characteristics of golden and/or silver scripts which prayed by king Chungyeol in Koryo Dynasty as they were, even though this script was manufactured by individual praying, this script follwed in the style of Kumjawon(golden letter center) and/or Unjawon(siIver letter center) as they were, because this script was written in the place of the golden script for the complete collection of Buddhist Sutras. In this paper all of the points described above with focusing on the referred records and an epilog of this script were collectively considered to make clear the characteristics of the script centers, golden and/or silver letter.

Creep, recovery and high strain rate response of soft roll cover materials

Polymer covered rolls are used in paper machines to extend the contact area between two mating rolls and also to damp vibrations excited in the roll systems. On the other hand, viscoelastic covers can also be a source of vibration problems because of incomplete recovery of time dependent deformation between two consecutive compression cycles. In this paper, the viscoelastic behavior of two relatively hard particle-reinforced epoxy based calender roll covers as well as a soft polyurethane based coater roll cover material was studied at different loading rates. Because the high loading rates common in modern paper machine operation cannot normally be achieved using servohydraulic testing machines, a compressive split Hopkinson pressure bar (SHPB) technique was applied. In a roll cover, the stress-state is multi-axial, including also shear components, and therefore compressive SHPB tests do not fully simulate the nip loading but provide, nevertheless, a good basis for comparison of different materials. Also long duration creep tests at different temperatures were made using servohydraulic testing machines to construct master curves, which extend the time scale of creep data up to hundreds of hours.

Numerical simulation of dynamic rolling contact including delay effect from cover layer

The numerical solution of a rolling contact dynamics of two paper machine rolls is discussed. The delay effect of a polymer roll cover layer is included in the system and the vibrations of the contact are studied. The stability of a test delay case is determined by time domain analyses

Experiments in a pilot-scale impulse unit – heat transfer and water removal rates

This is the first paper out of two dealing with heat transfer, water removal and energy efficiencies in an impulse unit in the pilot-scale research paper machine EuroFEX, located at the Swedish Pulp and Paper Research Institute (STFI) in Stockholm, Sweden. The paper produced was made of kraft pulp and with basis weights of 60-120 g/m(2). The roll surface temperature ranged from ambient temperature to 350 degreesC and the press loads were between 400-800 kN/m. The paper was produced at machines speeds of 300-800 m/min. An energy balance was conducted for the impulse unit to determine the different heat flows. It was determined that about 60% of the electrical power input was transferred to the paper web. The major heat loss was caused by wafer cooling of the induction heater. It was concluded that the heat transfer to the paper web was dependent on the roll surface temperature, the machine speed and the ingoing moisture ratio. The heat transfer to the paper web was not affected by the press load the basis weight or the roll cover. The water removal rate depended mainly on the roll surface temperature, the press load and the ingoing moisture ratio. (Less)

Effect of the Soft Roll Cover on the Paper Properties

Effect of the Soft Roll Cover on the Paper Properties

Delay effect from roll cover polymer material in paper finishing units

In this paper the dynamics of a roll-nip system in paper finishing units in the case of polymer covered roll is studied. The delay effect which provides an important additional effect on roll deformation and vibration of the system has been taken into account. The dynamical behavior of this system has been analysed in frequency domain and time domain.

Dynamic compression testing of particle-reinforced polymer roll cover materials

Abstract Two polymer composite roll cover materials were studied using dynamic compression tests. The main focus was determination of viscoelastic properties of the materials and development of mathematical models to describe the behavior of these materials in the contact area between two rolls. The compression tests were conducted using short rise time pulses with different durations in servohydraulic materials testing machines. In the modeling, combinations of standard elastic and viscoelastic elements were used together with the Boltzmann superposition principle. A simple spring-dashpot model was found to fit sufficiently to the experimental data with relaxation (retardation) times ranging from a few milliseconds in transient loading tests to tens of hours in static compression tests

Three-Dimensional Stability Analysis of Free Surface Flows: Application to Forward Deformable Roll Coating

Coating flows, with a few exceptions, need to be steady and two-dimensional flows. Moreover, the flow states need to be stable at the operating conditions chosen. The goal of stability analysis of coating flows is to determine the region in the parameter space at which the flow is stable and therefore the coated layer uniform. To determine the stability of liquid flows, a generalized eigenvalue problem has to be solved. This paper describes a formulation for a linear, three-dimensional stability analysis of free surface flows that reduces the size of the eigenproblem, decreasing the computational cost, with no further simplification, when compared with the methods reported in the literature. This formulation is used to study the instability that arises in film-splitting flows between counter-rotating rolls in a deformable gap. This flow instability leads to nonuniform coating characterized by a wavy thickness profile in the transverse direction. This patterning is usually referred to as “ribs.” This type of instability has received a lot of attention in the literature. However, all previous work has addressed the flow between two rigid rolls. Often, in practice, one of the rolls of a pair is covered by a layer of elastomer. The deformation of the roll cover alters the conformation of the gap, the pressure gradient at the film-split meniscus, and, consequently, the critical parameters at the onset of ribbing change. The results indicate how a deformable cover can be used to delay the onset of ribbing in forward-roll coating.