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Reliable cleaning processes are an absolute prerequisite to ensure the production of safe foods. In particular, the cleaning of heat exchangers is a crucial process step since temperature induces t...

Abstract Leather, which is regularly tanned from whole hides of up to 5 m2, needs a constant thickness over the entire surface in order to be processed into high-quality consumer goods such as shoes, furniture and car interiors. Precise adjustment of the thickness is achieved by shaving. On an industrial scale, rotating knife rollers are used to remove chips from the flesh side of semi-finished leathers whereby adjusting the specified thickness and generating a smooth surface. Care must be taken to prevent the temperature from rising above the denaturation temperature of the leather during shaving in order to avoid any loss of quality. Beside this, temperature rise is always a sign of friction showing avoidable energy expenditure. In order to localize the source of friction during shaving, actual temperature development at the roller knife is studied. Different measuring methods are used to evaluate the temperature increase at the blade roll of the shaving machine. The finite element method is used to thermally simulate the process. Measured temperatures, the geometry of the blade roll and process data are taken into account for modelling the temperature development close to the blade edge. The obtained results enhance the understanding of temperature generating processes during machine operation and allow conclusions about potential improvements in the design of the machine and blades. Graphical abstract

The removal of film-like deposits is a challenge in many fields of production. For environmental and economic reasons, the cleaning processes need to be optimized. An optimization by means of computational fluid dynamics seems to be beneficial, but is subject to some restrictions, especially in industrial context. General modeling ideas, a subdivision into sub-processes and the significance of time dependent soil behavior are discussed as well as specific concepts related to four basic cleaning mechanisms, namely diffusive dissolution, cohesive separation, viscous shifting and adhesive detachment. Cleaning experiments in fully developed plane channel flow, resembling a simplified plate heat exchanger, are performed with model soils (starch, petroleum jelly, ketchup) which were chosen to represent an almost ideal form of one of the basic cleaning mechanisms.

To evaluate the influence of different normal pressures and the fiber orientation on the in-plane compression behavior of paperboard during the deep drawing process, a new method was developed. In addition, the influence of the wrinkle formation on the dynamic coefficient of friction and the bending resistance was examined. To evaluate the eligibility of the in-plane compression testing method, a validation strategy was developed to compare the results from the new alternative tests with the punch force profiles from the deep drawing process within an empirical model.

Die wesentlichen Eigenschaften eines technischen Systems werden bereits in der Konzeptphase durch die Auswahl von Lösungsprinzipien vorbestimmt. Bei der Entwicklung automatisierter Produktionsanlagen stehen dabei die vier Zielgrößen Qualität, Zeit, Kosten und Flexibilität im Fokus. In der Literatur wird angenommen, dass zwischen diesen Anforderungen ein Zielkonflikt besteht, der von den Eigenschaften eines technischen Systems herrührt und die gleichzeitige Optimierung einer Anlage bzgl. aller vier Zielgrößen unmöglich macht. In diesem Beitrag wird deshalb ein methodischer Ansatz zu Diskussion gestellt, der die Untersuchung des Zielkonfliktes im konkreten Anwendungsfall ermöglicht und eine Entscheidungshilfe bei der Auswahl von Lösungskonzepten bieten kann. Ausgangspunkt ist ein dynamisches Systemmodell der Wechselwirkung zwischen Produkt und Produktionsanlage, sowie ein Ansatz zur Konzeptauswahl auf Grundlage der Polyoptimierung. Mit Hilfe parametrischer Modellbildung und Simulation kann die Entwicklungsaufgabe als mehrkriterielles Optimierungsproblem formuliert werden.

The cleaning behavior of a pre-wetted soil is studied experimentally and modeled numerically for the prototypical case of plane channel flow. One of the channel walls is soiled with a food-based mo...

Presently the lack of methods for fast quality evaluation of deep-drawn paperboard containers limit the industrial applicability of the deep-drawing process. This work presents an inline method for quality evaluation of deep-drawn paperboard containers. Two images of the deep-drawn sample are taken immediately after forming within the forming machine. The images are scanned and compared with a template of an ideal wrinkle structure. Calculation of the local cross-correlation of image sections and the template allows the detection and localization of wrinkles in the wall section of the deepdrawn paperboard container. The quantity of detected wrinkles and the evenness of the wrinkle distribution on the sample can be used as a quality measure. The accuracy of the method described in this work is validated against previously applied methods for wrinkle detection. The new method outperforms the previous methods in evaluation speed by a factor of 50 without significant loss of accuracy and thus is potentially applicable for laboratory and industrial applications.

In processing machines, technological tasks are implemented using suitable processing solutions. Those processing solutions can in turn have very different characteristics and specific advantages and disadvantages, e.g., concerning sensitivity to changing operating speed. In state-of-the-art processing machine controls, executing one single processing solution is supported. The execution of various processing solutions together and the combination of their advantages is currently not supported at all. In this article, a motion control approach is discussed that allows combining seemingly incompatible process solutions for a given technological task into a hybrid process solution, using the example of processing machines. The objective of this approach is to increase the achievable process window of the machine in terms of operating speed. It is shown that combining different process solutions can merge their advantages and compensate for their disadvantages. The article brings together the lessons learned from previous work in a new application to exploit advantages and compensate for disadvantages.

Operator assistance systems can help to reduce disturbance-related machine downtime in food production and packaging processes, especially when combined with machine learning algorithms. These assistance systems analyze the available sensor signals of the process control over time to help operators identify the causes of disturbances. Training such systems requires sufficient test data, which often are hardly available. Thus, this paper presents a study to investigate how test data for teaching machine learning algorithms can be generated by numerical simulation. The potential of using virtual commissioning (VC) software for simulating disturbances of discrete processes is examined, considering the example of a friction and collision-afflicted sub-process from an intermitting wrapping machine for confectionary. In this study the software industrialPhysics (iP) is analyzed regarding accuracy of static and dynamic friction and restitution. The values are verified by setting up virtual substitute tests and comparing the results with analytically determined values. Subsequently, prerecorded disturbances are classified, and seven selected elements are simulated in VC software, recording visual effects and switching the characteristics of sensors. The verification shows that VC software is generally adequate for the assigned task. Restrictions occur regarding the computing power required of the built-in physics engine and the resulting reduction of the machine to be simulated.

The non-degradability of most plastic packaging materials and the deficiency in recycling infrastructure on a global scale causes huge environmental problems. To address this problem, packaging materials produced from natural macroalgae polymers are a very promising alternative. The cultivation potential for macroalgae is huge and they are not in competition to food crops. Although the basic idea of using macroalgae polymers for thin film production was already described in 1934, the innovation has not established itself in the market. The primary reasons include lack of social and political interests, and insufficient technical solutions for industrial production. This review presents an overview on the changing attitudes of the populace towards the indiscriminate use of non-biodegradable packaging materials and the state-of-the-art processes for solid and flexible packaging production from natural macroalgae polymer. A novel and promising approach – semi-dry extrusion, to produce a 100% algae-based packaging material is presented here. The semi-dry extrusion of minimally processed algal biomass into different packaging products presents several benefits in terms of production cost, efficient use of water and energy resources, increased variety of products and reduced negative environmental impacts.

Because of the viscoelastic and therefore time-dependent properties of many foods, cutting at high velocity is a complicated process that may lead to undesired fracture and deformation and, thereby, reduce cutting quality. In addition, the analysis of the process is difficult because of the limited availability of commercial equipment for high-speed testing. This work reports on the development of a test station for high-speed cutting that enables a cutting velocity of up to 10 m/s; process analysis is realized by force and video data capturing. Using a bubble gum matrix as example, the increase in cutting velocity (from 10 −4 –10 1 m/s) as well as the decrease of sample temperature resulted in a decrease of the viscous contribution of the material and an increase of elastic effects that was reflected by reduced material deformation and brittle fracture during cutting. The holistic description of these effects was realized by interpreting cutting forces, video data, and results of dynamic mechanical analysis. The described test station with high-speed process analysis represents a prominent tool for demonstrating the sensitivity of viscoelastic foods towards temperature and mechanical stresses caused during cutting.

Hohe Kosten für die Reinigung von Maschinen und Anlagen führen zu Bestrebungen, diese hinsichtlich Reinigungszeit und ‐flüssigkeitseinsatz zu optimieren. Ein Ansatz ist die Anwendung diskontinuierlicher Flüssigkeitsstrahlen. Hierfür wurden zwei Strömungsarten hinsichtlich ihrer effizienzsteigernden Wirkung für zwei Lebensmittelbestandteile Xanthan und Stärke untersucht. Im Ergebnis konnte der Reinigungsflüssigkeitsverbrauch für einzelne Betriebspunkte um die Hälfte gesenkt werden. Die Reinigungszeit sank bei der Xanthanverschmutzung ebenfalls, wohingegen sie bei Stärke gleich oder höher war.

The visual and mechanical quality of paperboard packaging components formed by deep drawing closely corresponds to the wrinkle distribution within the material wall section. Assessing this quality of paperboard packaging components currently relies on very slow or even subjective methods. Therefore, counting the number of wrinkles and measuring the mean distance between wrinkles proved to be a sensitive strategy for the evaluation of quality levels in deep drawing formed paperboard containers like cups or trays. A method introduced by Hauptmann proposes the measurement of the distances between 10 wrinkles in machine direction and 10 wrinkles in cross direction for each sample. However, this method is unsatisfactory because it can only observe a small part of each sample and is subject to deviation through the individual judgement of the person carrying out the survey. Further methods, as well as their respective application range, are listed in Table 1. Hence, it is desirable to automate the wrinkle survey to be carried out without operator influences to the measurement. This paper introduces such an automated measuring method. The given method relies on recording the sample surface topography through laser-distance measurement. An evaluation algorithm, which enables the detection of wrinkles in the topographic data, is proposed. Furthermore, it is shown that the method yields feasible results and is capable of generating reliable quality information in considerably reduced time frames. Copyright © 2017 John Wiley & Sons, Ltd.

The deep-drawing process of paperboard has experienced essential improvement in the recent past; however, the technological advancements have not been transferred to packaging machines yet. Two of the most important issues with regard to the reliable production of high quality 3D shapes are the use of elevated moisture and defined blank holder force profiles. This paper examines a roll preparation method for applying additional water to the paperboard and analyses a spring-loaded blank holder solution with regard to its achieved accuracy and reliability of the force characteristics. A two-sided roll application of water on the paperboard using a sponge rubber cover on one of the rolls produces a water intake of up to 12%. The effect of moisture applied by roll preparation is higher compared to conditioning under controlled climate conditions, and the preparation time is reduced to a few seconds. The spring-loaded blank holder introduced in the paper completely works in position control and avoids the switch over to force control as well as the problem of small position steps, which were necessary during force control. A harmonic oscillation of the blank holder while the material is drawn out of it could not be observed up to an output of 150 cycles per minute. An application of a roll-based moisturization unit and a spring-loaded blank holder force in modern packaging machines appears feasible and favourable according to the results of this paper and maintains the capabilities of this 3D forming technology to a large part. Copyright © 2016 John Wiley & Sons, Ltd.

We estimate the orientation of wood fibers in porous networks like paper, paperboard or fiberboard by computing digital thermal conductivity experiments on micro-computed tomography ( μ CT) images with artificial isotropic thermal conductivity parameters. The accuracy of mechanical and thermal constitutive models for porous wood fiber based materials crucially depends on knowing the wood fiber orientation. Unfortunately, due to the high porosity, the micro-heterogeneity of wood fibers, the high carbon content of organic materials and the unknown additives present in industrial paper, μ CT-scans often exhibit low contrast and strong artifacts. Conventional image processing approaches encounter difficulties, as they rely upon convex fiber cross sections. We propose a solution by circumventing the segmentation of single wood fibers in μ CT images, by performing thermal conductivity simulations on binarized wood fiber structures, where an artificial isotropic thermal conductivity is associated to the fibers and the pore space is considered as isolating. The local and global temperature fluxes are assembled into a fiber orientation tensor. This method overcomes the limitations of the mentioned local image processing approaches, as individual fibers need not be resolved and convergence for increasing resolution is a consequence of abstract mathematical theory. We use our novel method to analyze large three-dimensional μ CT-scans and a synchrotron scan of a paperboard sample, serving as the starting point of an accurate micromechanical modeling of the effective anisotropic mechanical behavior of paper and paperboard. These results are crucial for calculating the mechanical strength of deep-drawn paperboard, which will be accomplished in a subsequent article.

This article presents the study of the thermal and acoustic effects occurring in polymer samples of different thicknesses receiving high-intensity focused ultrasound (HIFU). Whereas the heating mechanisms in polymer plates immersed in water are well known, the physical mechanisms enabling the heating of polymer films using a solid waveguide transducer remain not fully understood. A coupled acoustothermal finite-element simulation is conducted to model the sound field and the heat generation inside polymer samples of different thicknesses. To validate the acoustic model, the acoustic particle velocities at the transducer waveguide tip are measured by vibrometry and compared with the simulation results. The heating effects in the samples are monitored using an infrared thermography system and compared with the measured particle velocities and with the acoustic and thermal simulation results. Correlations among particle velocities, sound intensity, and polymer heating are investigated. A qualitative and quantitative correlation between the simulation and the measurement results is found. Experiments show that the heating effects depend on the sample thickness. In samples thinner than 1 mm, the maximum temperature is lower than the one observed in samples thicker than 1 mm but rises faster. The simulation shows that the sound intensity in polymer samples thinner than 1 mm decreases sharply with the decrease in the thickness of the sample. This study contributes to the understanding of the challenges in heating thin polymer films by HIFU in a dry environment, using only a force to couple the transducer to the polymer films.

The effect of stand-off distance (the distance between a stationary nozzle and a soiled surface, L) on cleaning by a water jet generated by a 3 mm nozzle (diameter, dN) was studied. Two nozzle gauge pressures, pN = 2.0 bar and 4.0 bar, giving jet Reynolds numbers of ReJet = 43800 and 61600, were investigated, for four soils with different cleaning behaviour (petroleum jelly, ketchup, mustard, starch + diatomaceous earth). For long times, of tc = 10 min and 20 min, the area cleaned increased with L due to jet break-up increasing the area exposed to impact. For soils which are easy to clean (here ketchup) at shorter time scales (tc ≤ 0.1 min) a stand-off distance of L = 2 m gave optimal cleaned area. Soils which are hard to clean required small stand-off distances with short cleaning times. The cleaning results are compared with jet break-up, impact force and impact pressure results presented by Fuchs et al. (2018). Jet break-up gives a larger impact area which results in a more efficient cleaning for most soils. However, results of the cleaned area only correspond to measurements of jet impact area in the case of soils that are not swellable and hard to clean. Binding forces within the soils were determined with a micromanipulation apparatus. Results show that the basic cleaning behaviour of the soils can also be determined on a laboratory scale without using a water jet. This allows the prediction of cleaning behaviour without extensive cleaning tests as well as preselection of cleaning devices.

In this paper, deep‐drawn paperboard cups are characterized in terms of their elongation along the cup wall. For this purpose, a method for the non‐destructive determination of the elongation was developed and tested. Using the presented method, a parameter study of the process parameters blank holder force, forming temperature, material moisture content, drawing velocity, and clearance ratio was performed. The influence of the process parameters on the cup wall elongation was determined by statistical design of experiments. Using the determined relationships between the process parameters, it was possible to achieve a shape‐specific characterization of the elongation along the cup wall. The parameter study showed a significant influence of the blank holder force, the forming temperature, and the material moisture content to the elongation along the cup wall.

A physical-numerical simulation model for the cleaning of swellable soils by diffusive dissolution or cohesive separation of small soil particles, which was developed targeting a low computational effort, is presented and validated. The flow calculation, based on the Reynolds averaged Navier Stokes equations (RANS), and the calculation of the soil transport, modelled following the unsteady RANS concept, are performed successively. The behaviour of the soil is modelled as a transient Dirichlet boundary condition, its parameters being determined in laboratory experiments using plane channel flow. A validation is performed for a coherent water jet impinging vertically on a substrate, which is covered by a starch-based model soil, at a distance of 100 mm to the nozzle. Using a nozzle diameter of 1.69 mm and pressures in the nozzle ranging from 1.5 to 5 bar, corresponding to Reynolds numbers between 17700 and 55600, the wall shear stress in this configuration exceeds the values given in the laboratory tests by two orders of magnitude. Despite this difference, the simplicity of the model and the complexity of the test case, the simulated cleaning times correspond very well to the measured values. Thus, the targeted scalability and transferability of the model to other flow configurations are ensured.

This paper deals with the task of conveying open containers filled with liquids in processing machines. It is experimentally shown that the process indicates a significant dynamic behavior. Such behavior leads to undesired effects like residual vibration. Common motion profiles cannot avoid these vibrations. Due to this a limited usable machine operating speed range results. For increasing this range, the necessity of operating speed dependent motion profiles is explained, for which an approach is constructed by using a special motion law. Eventually, the success of this approach is experimentally shown.

Whey protein has been used extensively to investigate the efficiency of procedures for cleaning dairy production equipment owing to the chemical reaction it undergoes at high temperature, similar to the formation of fouling deposits during heat treatment. In addition to the chemical and thermal aspects, a detailed understanding of the fundamental mechanical and fracture mechanisms that significantly influence the success of the cleaning procedure is indispensable. Consequently, to determine the basis for the mechanical detachment of whey protein isolate, in the present study, the mechanical characteristics and fracture properties of whey protein gels (WPGs) with a protein content of 15% and a treatment temperature of 80 °C were determined. For purely mechanical characterisation, axial compression and compression relaxation experiments were performed. The results suggest a non-linear stress–stretch behaviour combined with time-dependent mechanical characteristics. To characterise the fracture properties of WPGs, wire cutting experiments were performed. Based on a viscoelastic numerical model and the corresponding parameters identified from the experimental investigations, the cutting procedure of WPGs was simulated by assigning a fracture criterion, and the critical stress was determined based on the measured cutting forces.

Ein im Hinblick auf geringen Berechnungsaufwand entwickeltes, physikalisch-numerisches Simulationsmodell für Reinigungsvorgänge durch diffusives Auflösen oder kohäsives Trennen kleiner Verschmutzungsteilchen wird vorgestellt und validiert. Die Strömungs- berechnung auf Grundlage der Reynolds-gemittelten Navier Stokes Gleichungen (RANS) und die Berechnung des Verschmutzungstransports mittels eines instationären RANS- Ansatzes erfolgen entkoppelt. Das Verschmutzungsverhalten ist als transiente Dirichlet-Randbedingung modelliert, deren Parameter aus Laborexperimenten in einer ebenen Kanalströmung bestimmt werden. Die Validierung erfolgt für die Konfiguration eines senkrecht auftreffenden, kohärenten Flüssigkeitsstrahls für den Düsendurchmesser 1,69 mm und Drücke in der Düse zwischen 1,5 und 5 bar, d.h. Reynolds-Zahlen zwischen 17700 und 55600. Gemessen an der im Vergleich zu den Parametrierungsexperimenten um mehrere Größenordnungen höheren Wandschubspannung, der Einfachheit des Modells und der Komplexität des Testfalls wird eine sehr gute Übereinstimmung der simulierten Reinigungszeiten mit den Messwerten erreicht. Die angestrebte Skalierbarkeit sowie die Übertragbarkeit des Modells auf andere Strömungskonfigurationen sind somit gegeben.

Thermoforming is a process for the cheap mass-production of thin-walled plastic parts. A sheet of plastic is heated for increased deformability, and then deformed by overpressure into a mold with the end product’s shape. The main drawback is the inhomogeneous wall thickness distribution resulting from the common process. The authors believe that it is possible to improve these inhomogeneities by locally influencing the highly temperature-dependent material strength using directed jets of pressurized air for local cooling. As the high number of potentially influential parameters renders purely experimental parameter studies infeasible, a computational model that couples the flow of the pressurized air with the structural simulation of the deforming plastic is set up. With the combined results of experiments and simulations, a parameter study can be conducted, which allows for an optimization of air flow parameters for a more evenly distributed wall thickness.

Process development for the production of paperboard cups requires methods to capture the shape accuracy with fast, reliable and easy to apply measurement procedures. This publication aims to present a measurement method and an analysis of the influence of important parameters on the shape accuracy of deep drawn cups. Therefore, a shape accuracy analysis is developed and the precision of the measurement and influence of the operator are examined in detail. The method is applicable for cylindrical and non-cylindrical shapes and outputs a value to characterize the shape accuracy of a sample. A parameter studies is presented that covers the most important influencing parameters: blankholder force, punch and die temperature and moisture content. The temperatures of the forming tools are found to have a significant effect on the deviation from the required form. Furthermore, the results indicate that the blankholder force, which is highly important to control the formation of wrinkles, does not have a significant effect on the shape accuracy.

An explicit finite element model of the deep-drawing of paperboard has been developed utilizing a custom yet simple material model which describes the anisotropy and plasticity of paperboard. The model was verified with a variety of tests and was then utilized to compare the punch force that was measured during the deep-drawing experiments to the punch force that was calculated during the deep-drawing simulations. All material parameters were calibrated based on individual experiments; thus, no parameter fitting was utilized to match the experimental deep-drawing results. The model was found to predict the experimental results with reasonable accuracy up to the point when wrinkling began to dominate the material response. Since most failures during paperboard deep-drawing occur before wrinkling begins to play a major role, this model can probably be utilized to study and predict the failure of deep-drawn paperboard cups. The overall trends and the effects of major process parameters are predicted by the model. The process parameters that were varied and compared for both experiments and simulations were: blankholder force, die temperature, and thickness. The model was utilized to discover that friction of the blankholder and die have significant effects on the punch force and thus the stress, implying that low-friction dies and blankholders can considerably reduce the failure probability and thus also improve the quality of deep-drawn paperboard cups.

The aim of this paper is to contribute to an improved understanding of deformation mechanisms of paperboard in the deep drawing process with immediate compression which reaches the highest degree of formability. Experiments with different fiber types and material structures were conducted on a laboratory and pilot scale to determine the major material-related influences on the formability of paperboard. The different fiber type combinations were studied together with different additives. The results show that increased pore volume and fiber-to-fiber mobility significantly increase initial wrinkle height which is significant for the quality of the drawn three dimensional (3D) structure. A material structure consisting of a mixture of cellulose fibers and a low percentage of stiff regenerated cellulose or synthetic staple fibers in combination with alkyl ketene dimer or cationic wax as an additive leads to a wrinkle-free wall until a forming ratio (forming height divided by base diameter) of at least 0.22 is reached. Accordingly, the process can be broken down into three phases. In the first phase, the cellulosic structures are deformed or broken, and the material density is reduced due to fiber-to-fiber movement. Refining and wet pressing decrease pore volume, increase the number of bonds in the material, thereby obstructing fiber-to-fiber movement. In the second phase, wrinkles occur. The introduced bending stiffness index together with the tensile index provides an indication of the material behavior in these two phases. The third phase is a restructuring of the material structure and a fixation of wrinkles by creating new bonds in the limited wrinkle areas. The experiments indicate that refined fibers make significantly higher wrinkle strength possible and thus better fixation of the final 3D structure shape. Additives with low melting temperatures can also contribute to improved wrinkle strength even in a low mass percentage of 0.5 %.

High-intensity focused ultrasound (HIFU) is increasingly getting in focus of interest for polymer layer joining [1]. It has been found that HIFU is able to heat polymer layers with a temperature rise of over 680 K · s−1 [1]. However the physical mechanisms causing the heating of thin polymer layers using ultrasound with a solid wave guide ultrasonic transducer are still unknown. In this paper, the correlation between sample thickness, particle velocity at the top of the solid wave guide and heating behaviors are investigated by means of scanning Doppler laser vibrometry and infrared thermography. The study showed that the heat generation induced by high-intensity focused ultrasound with a solid wave guide depends on the distribution of the particle velocities at the top of the wave guide for samples thinner than a half wavelength in PMMA. However for the samples thicker than a half wavelength, the heating of the sample depends on the particle velocities distribution at the top of the wave guide, as well as on the sound waves focused by the transducer. The findings are relevant for processes in which solid polymers need to be heated quickly and locally such as in welding or forming.

The cleaning behavior of a soil with physical properties that depend on the wetting time is studied experimentally via the local phosphorescence detection method and simulated numerically in fully developed plane channel flow for Reynolds numbers up to 30,000. A computationally inexpensive general cleaning model is proposed, adopting an existing removal model and coupling it to the turbulent flow field. The influence of the soil on the flow is neglected and the transient behavior of the soil during cleaning is modeled in the form of a transient Dirichlet boundary condition. This approach is innovative for computational fluid dynamics of this phenomenon. The way of determining the model parameters from the experiment is described. The comparison of the simulation results with experimental data reveals very good suitability of the model in the case of a starch soil. A similar good agreement is found for data for a model protein foulant in tube flow from the literature.