Web Tension Research Articles

Analysis of wrinkles and corrugations in the electrode calendering process

ABSTRACT Calendering is a crucial process in manufacturing of lithium-ion batteries electrodes. Wrinkles and corrugations are the main manufacturing defects in the calendering process. This study aims at studying the formation mechanism of wrinkles and corrugations. Corrugations and wrinkles of the electrodes were revealed to be more dependent on the difference between the front and back tensions. The tortuosity of corrugations was reduced by 34.2% when the tension difference decreased from 20 to 5 N. The increase in the tension difference led to a linear increase of the shear displacement δ, causing severe wrinkles in the uncoated area of the electrodes. The analytical prediction model for wrinkles during calendering was established based on the shearing of a rectangular membrane. The optimal web tension conditions, at a tension difference of 17 N, was achieved to obtain the optimal calendered electrodes.

Effect of spider's weight on signal transmittance in vertical orb webs.

Spider orb web is a sophisticated structure that needs to fulfil multiple roles, such as trapping prey and transmitting web-borne signals. When building their web, heavier spiders tend to increase the pretension on the web, which seems counterintuitive since a tighter web would decrease the chances of stopping and retaining prey. In this article, we claim that heavier orb-weaving spiders increase tension on the web in order to reduce the attenuation of the vibratory signal coming from the bottom part of the web. We support our claim by first building a detailed spider web model, which is tuned by a tension-adjusting algorithm to fit the experimentally observed profiles. Then, the effects of the spider weight and the web tension on the signal transmittance properties are investigated using state-of-the-art finite element analysis tools.

Web tension AI modeling and reconstruction for digital twin of roll-to-roll system

AbstractDigital twins (DT) are gaining attention as an emerging technology in Smart manufacturing systems. These DTs comprise various units that enable simulation, monitoring, and prediction of the manufacturing process. This study introduces a predictive model for web tension and a tension reconstruction algorithm for the DT of the roll-to-roll (R2R) system. The observed web tension signals from tension sensors decomposed into a mean component, a sinusoidal wave, and a random noise. Utilizing deep neural networks, the predictive model integrated various sub-models to forecast statistical (mean, standard deviation) and frequency domain (main frequency, signal-to-noise ratio) features of the web tension signal. Through fivefold cross-validation, 23 model architectures were optimized, with selected architectures ranging from 16-32-32-1 to 16-32-64-32-1 nodes per layer. Overall, R2 scores on the test set ranged from approximately 52 to 100%. The proposed reconstruction algorithm generated tension signals from the model’s predictions that closely resemble the original tension signals, indicating credible reconstructions. The proposed predictive model and reconstruction algorithm were integrated into the DT of the R2R system, offering a valuable tool for monitoring and optimizing the R2R process.

Electrostatic charging of material webs in gravure printing presses

This paper deals with the electrostatic charging of material webs in production machines. Measurements were made with a special measurement setup inside a gravure printing press and the results were analyzed and interpreted. In order to gather as much information as possible, the electric field strength of a free-spanning web was monitored at different positions inside the machine and under different production conditions. The measurement results confirmed theoretical principles and practical experience, such as the fact that the type of material, printing inks, coatings, machine speed, web tension, printing process and corona pretreatment have a significant effect on the level and polarity of the electrostatic charging. During the series of experiments, peak field strengths of up to 300 kV/m resulting from the charge on the web were measured and changes in the sign were detected within a very short period of time.

Study on Multi-Span Tension Coupling Relationship of Gravure Printed Electronic Equipment

To improve the performance of the tension control system in gravure printed electronic equipment, it is necessary to study the tension system model of gravure-printing electronic equipment. This paper focuses on the coupling characteristics of multi-span tension systems. Firstly, based on the single-span tension model, the mathematical model of the printing tension subsystem is established and simplified into a general multi-span tension coupling model. Then, using the relationship between the inputs and outputs of the system, the coupling model is simulated using MATLAB/Simulink and verified through experiments on the gravure printed electronic platform. Finally, the coupling relationship and influence laws among multi-physical quantities of the system are analyzed. The research results show that changes in the input web tension of the multi-span system will affect the steady-state tension values of all subsequent spans. Moreover, the speed change in a roller in the multi-span system will not only affect the steady-state tension value of its own span, but also cause transient tension fluctuations in all subsequent spans. The findings of this paper provide an important theoretical basis for the research of the tension system in gravure printed electronic equipment, contributing to the enhancement of printed electronic product quality.

Local buckling of the bottom flange in steel-concrete composite beams with trapezoidal corrugated webs subjected to end restraint at high temperatures

Steel-concrete composite beams with trapezoidal corrugated webs (SCBCW) are prone to rapid failure at high temperatures due to local instability of the bottom flange. The failure mechanism of SCBCW, which is an integral part of the holistic structure and subject to axial and rotational restraints from adjacent members at elevated temperatures, differs from conventionally simply supported steel-concrete composite beams with straight webs. To investigate the evolution of local buckling in the compressed flange of SCBCW under high temperature conditions, a composite beam model with frame restraints was developed using ABAQUS finite element software. In this model, the composite beam is connected to restraint frame columns through high-strength bolts. The changes in axial stress, bending moment, and deflection of the compressed flange of SCBCW were analyzed as temperature increased. Results indicate that at elevated temperatures, additional bending moments occur in the flange plane due to axial restraints, section temperature gradients, section negative bending moments and accordion effect caused by corrugated web on compressed bottom flange of SCBCW. This leads to a gradual increase in axial compressive stress before local buckling occurs followed by a decrease due to internal force redistribution upon onset of buckling. Studies show that initial buckling of bottom flange occurs on one side of flat section of web where axial compressive stress is relatively high while restraint effect on web is low; Subsequent local buckling of the beam then appears on opposite side adjacent flat section of web after initial buckle occure on one side. After local buckling appears on both sides of web tension bands appear on both sides where bottom flange experiences localized bucking. The setting of longitudinal stiffeners (LS) can effectively improve the local stability of the bottom flange of the composite beam, while the setting of transverse stiffeners (TS) has no significant impact.

Cooperative compensate register control for mechanical shaft driven roll-to-roll printing system with dancer rolls

In mechanical shaft driven roll-to-roll (R2R) printing systems, tension propagation caused by the regulation of dancer rolls increase the control difficulty of the whole system. In this paper, a cooperative compensate control (CoComC) method is proposed for the R2R printing systems to attenuate tension fluctuation and reduce the register errors. Specifically, a mechanical model is established to quantify the relationship among the web tension, linear velocity of dancer roll and register error. Based on the model, a well-tuned feedback control law is designed for each dancer roll, and a cooperative matrix is proposed to coordinate the feedback control to attenuate the tension fluctuation and reduce the register error in the corresponding printing unit. Further, the stability and convergence condition of the proposed control system are provided and proved via Lyapunov stability theory. The effectiveness of the proposed control method is demonstrated by experiments. Comparisons of the existing control method are carried out to show the superior performance of CoComC, i.e., higher register accuracy, superior fluctuation attenuation performance and less waste of printing material.

Float-stacked graphene–PMMA laminate

Semi-infinite single-atom-thick graphene is an ideal reinforcing material that can simultaneously improve the mechanical, electrical, and thermal properties of matrix. Here, we present a float-stacking strategy to accurately align the monolayer graphene reinforcement in polymer matrix. We float graphene-poly(methylmethacrylate) (PMMA) membrane (GPM) at the water–air interface, and wind-up layer-by-layer by roller. During the stacking process, the inherent water meniscus continuously induces web tension of the GPM, suppressing wrinkle and folding generation. Moreover, rolling-up and hot-rolling mill process above the glass transition temperature of PMMA induces conformal contact between each layer. This allows for pre-tension of the composite, maximizing its reinforcing efficiency. The number and spacing of the embedded graphene fillers are precisely controlled. Notably, we accurately align 100 layers of monolayer graphene in a PMMA matrix with the same intervals to achieve a specific strength of about 118.5 MPa g−1 cm3, which is higher than that of lightweight Al alloy, and a thermal conductivity of about 4.00 W m−1 K−1, which is increased by about 2,000 %, compared to the PMMA film.

Analysis of longitudinal wrinkle formation during calendering of NMC811 cathodes under variation of different process parameters

The requirements for the lithium-ion battery (LIB) are constantly increasing. In the nearer future, batteries need to be even more powerful, safer and cheaper. One lever is the optimization of the production in order to minimize production scrap rates. In electrode manufacturing, calendering is an essential process step to adjust the volumetric energy density. However, this process leads to undesirable defects that result in production scrap. In this paper, the formation of longitudinal wrinkles is analyzed using a statistical experiment design. Electrode density, web tension and temperature are varied in two levels during calendering and are examined for their significance with regard to the geometry of the longitudinal wrinkles. Furthermore, the strain and the deformation of the electrode are analyzed. A complex interaction of material and process is revealed with respect to the formation of longitudinal wrinkles. A better understanding of these interactions contributes to optimize the calendering process and to find a solution to avoid longitudinal wrinkles.

Measurement of web tension using ambient vibrations in roll-to-roll manufacturing of flexible and printed electronics

Abstract Web tension measurement and control are important for the quality control of flexible and printed electronics fabricated by roll-to-roll (R2R) manufacturing. The distribution of tension within a R2R web can be calculated from the values of the web’s mechanical resonance frequencies. Typically, such measurements require an active external forcing to be generated and applied to the web. In this work, we show it is possible to obtain the web’s resonance frequencies from forcing due to ambient noise present in the test environment. This result broadens the applicability of noncontact resonance methods for computing web tension as currently available methods of active external forcing cannot be applied to all web materials and all R2R operating environments. We validate the ambient excitation method by comparing it to speaker-based acoustic excitation at atmospheric pressure and find the two methods agree within 0.5%. A calculation of the experimental motion of the web due to finite temperature effects suggests the observed vibration is generated from air-borne or structure-borne noise in the test environments. To show the effectiveness of the approach, we demonstrate the use of ambient excitation at five externally applied tensions, on three different web materials, and at both atmospheric and vacuum pressures.

A Roll‐to‐Roll Gravure‐Printing System for Manufacturing Near‐Field Energy‐Harvesting Labels

Billions of costless near‐field communication (NFC) sensor labels per day are demanded to practically enable edge computing between smartphones and everyday objects. However, to activate the billions of NFC sensor labels daily, providing an inexpensive manufacturing method for billions of wireless energy‐harvesting labels (WeHL) per day will become a decisive issue for realizing the practical applications. Herein, a roll‐to‐roll (R2R) gravure, a typical high‐throughput additive manufacturing method, is explored to print WeHLs where six diodes and six capacitors are integrated. To meet the high‐throughput manufacturing speed (90 mm s−1) of the R2R gravure system, six different electronic inks are formulated to print the WeHLs to harvest ±10 V from the smartphone's NFC carrier. To attain a practical device yield under the given printing speed, the web tension, nip force, doctor blade angle, and overlay printing registration accuracy are well controlled and optimized to print six different layers within a high overlay printing accuracy, while printing patterns to connect two electrodes with a height difference greater than 3 μm. The fully R2R‐printed WeHLs can successfully harvest energy from the smartphone's NFC carrier with the conversion efficiency of 50%.

A Real-Time Supervisory Control Strategy for Roll-to-Roll Dry Transfer of 2D Materials and Printed Electronics

With the advancement of manufacturing technology in transfer printing and two-dimensional materials fabrication, roll-to-roll (R2R) dry transfer by mechanical peeling is becoming a promising process for efficient transfer of thin film materials from a donor substrate to a target substrate for device fabrication. As a key process variable, the peeling angle determines the loading condition of the R2R dry transfer process and thus the quality of the transferred material. Controlling the peeling angle is challenging in a R2R process because of the adhesion energy and peeling front velocity in addition to the flexible substrates involved in the peeling process. In this article, a real-time supervisory control strategy is developed for the R2R mechanical peeling process. A strain energy-based peeling process model is employed to estimate the peeling front velocity and the adhesion energy. The real-time estimation is then used to generate reference signals for web tension controllers to track the desired peeling angles. The proposed control strategy is demonstrated with both simulation and experimental results.

Li-Ion Battery Electrode Manufacturing Control System in Winding Process: Tension Control in Industrial Complex Roll-to-Roll Winding Machine Via SMC-FLC Hybrid Control Method

Abstract This paper introduces a new control method for web tension control on a complex roll-to-roll winding machine used in battery production. A traditional web tension control method cannot perform well enough under high winding speed: the parameter tuning process is time-consuming, the disturbance rejection performance is not satisfying, and the control performance is not stable. A hybrid control method is proposed, and it is easy to be implemented on common programming platform for commercial winding machines with an easy tuning process, while providing superior control performance to the traditional control method. The system modeling used in the control method is much simpler than the modeling in most of the tension control researches, providing better feasibility for industrial application.

Paper bending stiffness and web tension measurement from a running web using a vacuum and computer imaging

A novel method for measuring the bending stiffness of paper online during manufacturing is intro-duced. The method uses photometric stereo imaging to detect the shape of the deflection surface caused by a controllable pressure difference over the paper’s surfaces. The hardware for the measurement is based on a combination of two existing sensors, which has accelerated and facilitated the development of the implementation. The deflection and loads are tied together by the governing differential equation for the bending of an orthotropic elastic plate with selected simplifications. An approach to resolve material parameters and in-plane loads without knowledge of traditional boundary conditions is suggested. The presented method was tested in a paper mill during manufacturing. For bending stiffnesses measured online, correlation coefficients 0.88 and 0.92 were obtained compared to state-of-the-art laboratory measurements. However, the results gained from a moving web are noisy and the data requires correction of the slope and an offset. Although several issues remain to be resolved before the method can be considered as an accurate measurement for industrial use, the theoretical background, the performance of online implementation, and the results are promising. Possible causes for the observed discrepancies and the future development of the method are discussed.

Towards Digital Twin Implementation in Roll-To-Roll Gravure Printed Electronics: Overlay Printing Registration Error Prediction Based on Printing Process Parameters

Roll-to-roll gravure (R2Rg) has become highly affiliated with printed electronics in the past few years due to its high yield of printed thin-film transistor (TFT) in active matrix devices, and to its low cost. For printing TFTs with multilayer structures, achieving a high-precision in overlay printing registration accuracy (OPRA) is a key challenge to attain the high degree of TFT integration through R2Rg. To address this challenge efficiently, a digital twin paradigm was first introduced in the R2Rg system with an aim to optimize the OPRA by developing a predictive model based on typical input variables such as web tension, nip force, and printing speed in the R2Rg system. In our introductory-level digital twin, errors in the OPRA were collected with the variable parameters of web tensions, nip forces, and printing speeds from several R2Rg printing processes. Subsequently, statistical features were extracted from the input data followed by the training of a deep learning long-short term memory (LSTM) model for predicting machine directional error (MD) in the OPRA. As a result of training the LSTM model in our digital twin, its attained accuracy of prediction was 77%. Based on this result, we studied the relationship between the nip forces and printing speeds to predict the MD error in the OPRA. The results indicated a correlation between the MD error in the OPRA and the printing speed, as the MD error amplitude in the OPRA tended to decline at the higher printing speed.

Influence of Electrode Corrugation after Calendering on the Geometry of Single Electrode Sheets in Battery Cell Production

Calendering is an essential process step in battery cell production. By selective compaction of the material, the performance of the battery cell can be optimized. During processing, corrugations can occur in the machine direction, which are characterized in this article in relation to the material systems LiNi0.8Mn0.1Co0.1O2 (NMC811) and LiNi0.6Mn0.2Co0.2O2 (NMC622) as well as the rate of compaction and the web tension. It is shown that the corrugations are strongly dependent on the rate of compaction. The material system and the web tension show a weaker influence on the corrugation characteristics. Subsequently, single electrode sheets are cut from the coils and their geometry is investigated. It is shown that the corrugation hardly propagates further into the single electrodes, which is explained with the storage time of the electrodes. Rather, the coil bending strongly influences the electrode sheet geometry. It is shown that the position of the conductor tab also has an important influence.

Model‐Based Optimization of Web Tension Control for the Flexible Cell Stack Assembly of Lithium‐Ion Battery Cells

The transformation toward electromobility presents a significant challenge to the battery cell production processes. It is, therefore, necessary to establish efficient and robust operations and machines to meet the forecasted demand for manufactured cell capacity. Currently, the development and ramp‐up phases of production machines, especially for cell stack assembly, are characterized by high material scrap rates and large personnel expenses. Aspects such as the web tension of electrodes or separator materials during separation and stack assembly have a significant influence on the subsequent intermediate product properties, and therefore present a key challenge. Herein, the optimal methodology for the web tension control of electrode materials is determined via a model‐based approach by the means of a digital twin. The focus is hereby set on a production machine for the flexible cell stack assembly. Appropriate control methods are implemented and validated on the real system, thus reducing material scrap rates and overall costs. The control of the web tension by means of an unwinder and material storage was found to be optimal on the basis of the model and confirmed experimentally.

Auto-Tuning PI Controller Design Using Fuzzy Logic Controller for Web Tension Control in Roll Rewinder System

Paper has a very important role, because it increases the productivity of pulp and paper companies in Indonesia. The company's development in 2018 increased by 2.1%, this was indicated by increasing consumer demand. Therefore, paper becomes a necessity in everyday life. The criteria for the paper to be produced are paper with a flat surface and cannot be wrinkled. However, errors in paper production that often occur are a lot of wrinkles and uneven paper surfaces. This happens because of a discrepancy in the dynamics of paper tension with the standards that have been set. The paper record is caused by the dynamics of the web tension in the Rewinder Roll system. In order for the web tension to remain stable, a controller is needed. The controller used is Auto-Tuning PI controller using Fuzzy Logic Controller (FLC). The controller can be said to be successful when it is able to perform automatic tuning of setpoint changes. The results showed that the system was able to achieve setpoint values, overcome overshoot and steady-state error (Ess) with response time values, namely Tr=0.3151 seconds, Ts=0.3750, Td=0.0721, overshoot=0.0044%, and Ess=0 N.

Dynamic behavior of axially moving web in multi-span roll-to-roll microcontact printing system

This article presents theoretical dynamic analysis of a vibrating axially moving web of a multi-span / multi-roll microcontact printing system and experimental measurements of the system’s frequency response. A unique lab-scale microcontact printing machine with high-speed web handling capabilities is used. The axially moving web is modeled as a string and as a membrane. Then, numerical results of both models are compared with experimentally obtained response. The experiment is run for both case of constant axial speed and varying axial speed with time. Although both models are in good agreement with the experimental results, the values of frequencies obtained from the string model are found to be in closer agreement with those obtained from the experimental findings. It is found that increasing the web tension and decreasing the axial web speed increase the system’s frequency.

A method to estimate adhesion energy of as-grown graphene in a roll-to-roll dry transfer process

The interfacial adhesion energy of as-grown graphene on its metal growth substrate is an important variable in designing, monitoring, and controlling a roll-to-roll (R2R) graphene transfer process using mechanical peeling. In this study, we develop a novel method to estimate the adhesion energy of as-grown graphene during the R2R dry transfer process. An energy balance model is established to derive the adhesion energy based on web tension and bending curvature measurements. Experiments were conducted under various mechanical peeling conditions. The adhesion energy of as-grown graphene on copper foil was determined to be from 1.22 J/m2 to 2.58 J/m2 depending on the peeling front geometry. The developed adhesion energy estimation method is compatible with the R2R process and can be used to monitor and control the large-scale graphene transfer process with in-process measurements.