Zeitschrift Kunststofftechnik Journal of Plastics Technology

Transcription

1 Zeitschrift Kunststofftechnik Journal of Plastics Technology archivierte, peer-rezensierte Internetzeitschrift des Wissenschaftlichen Arbeitskreises Kunststofftechnik (WAK) archival, peer-reviewed online Journal of the Scientific Alliance of Polymer Technology Prof. Dr.-Ing. Johannes Wortberg, Dipl.-Ing. Felix A. Heinzler Institut für Produkt Engineering, Universität Duisburg-Essen eingereicht/handed in: angenommen/accepted: by enhanced reversion control The reversing haul-off unit at today`s blown film extrusion lines is supposed to reduce the effects of thickness tolerances during the winding process of film rolls. The thickness profile differences are rearranged along the width of the film roll. Most process setups in the blownfilm-extrusion production do not use the reversion for specific optimization. A new developed simulation model and programmed tool at the University of Duisburg-Essen shows details to critical effects of thickness tolerances in the build-up process of film rolls. In correlation with known winding defects, potentials to optimize the production by a proper reversion control are shown. The optimization ranges from adjusted speed levels according to the roll diameter to timed positioning of very critical areas within the roll-changing process and the start of a new film roll build-up. The optimization potentials are summarized in an enhanced control setup to connect the extrusion process and the winding for good roll and film quality. Optimierter Aufbauprozess von Folienwickeln durch eine erweiterte Reversierungssteuerung Die negativen Effekte von Dickentoleranzen auf die Qualität von Folienwickeln können heutzutage durch den reversierenden Abzug reduziert werden. Die Unterschiede im Dickenprofil der aufzuwickelnden Folie werden über der Rollenbreite reversierend verteilt. Allerdings werden in vielen Produktionen die Möglichkeiten der Reversierung nicht gezielt eingesetzt und für eine Optimierung genutzt. Ein neuentwickeltes Simulationsmodell und Softwaretool der Universität Duisburg-Essen zeigt kritische Effekte des Dickenprofils im Wickelaufbau und mögliche Optimierungspotentiale zur Steigerung der Wickelqualität. Eine erweiterte Reversierungssteuerung reicht von einer Anpassung der Reversiergeschwindigkeit bis hin zu einer gezielte Dickenprofilpositionierung beim Rollenwechsel. Carl Hanser Verlag Zeitschrift Kunststofftechnik / Journal of Plastics Technology 9 (2013) 4

2 by enhanced reversion control J. Wortberg, F. A. Heinzler Today`s state of the art blown film extrusion lines are equipped with a reversing haul-off system. The reversing haul-off unit is supposed to reduce the effects of thickness tolerances during the winding process of film rolls. The reversion shifts the thickness profile according to the rotation speed of the roll and of course the reversion speed itself. The thickness profile differences are rearranged along the width of the film roll during the winding process. Most process setups in the blown-film-extrusion production have a standardized reversing speed or do not use the reversion for specific optimization. To adjust a proper speed or even a speed profile is not taken into consideration to enhance the roll- and product-quality. A new developed simulation model and programmed tool at the University of Duisburg-Essen shows details to critical effects of thickness tolerances in the build-up process of film rolls. In correlation to known winding defects potentials to optimize the production by a proper reversion control are shown. The optimization ranges from adjusted speed levels according to the roll diameter to timed positioning of very critical areas within the roll-changing process and the start of a new film roll build-up. The optimization potentials are summarized in an enhanced control setup to connect the extrusion process and the winding for good roll and film quality. 1 INTRODUCTION Polymer films have very different applications in today`s everyday life. One main sector is packaging with a main share of 39,1 % of European plastic demand in 2011 [1]. Still the primary processed polymers for common applications are polyethylene (PE-LD, PE-HD, PE-LLD) and polypropylene (PP). For the different applications, the polymer composition and thickness of the film varies. It ranges from lightweight food packaging to films for agricultural use. Whether the film is produced on a cast film line or blown film line, the main quality indices are the thickness profile of the film and the recommended arrangement of different material layers. Of course e.g. mechanical or optical properties are also important with respect to the product requirements. In this paper the referred process is blown film extrusion. Nevertheless, in addition to the film properties the thickness profile influences the roll quality during storage and can cause critical damages. Possible damages are high stress levels amplified by shrinkage that cause wrinkles or ridges. Journal of Plastics Technology 9 (2013) 4 161

3 The predominant influences on the thickness profile during a blown film extrusion process are the blow head with the extrusion die and the local stretch ratio considering the cooling of the film. Today s state of the art film lines enable a good process control and stability during the processing of up to 12 layer films. But still current thickness profiles have a tolerance band that has to be dealt with in the processing. To lower effects of the thickness profile and to prevent defects, blown film extrusion machines are equipped with a reversion or rotation system [2]. To show influences of the thickness profile arrangements, a tool for model based process prediction and enhancement has been developed at the University of Duisburg-Essen. In the following the setup of the model, the calculation bases and possible optimizations for the processing are shown in correlation to winding defects. 2 THICKNESS PROFILES IN BLOWN FILM EXTRUSION Within the blown film extrusion process, the polymer melt is conveyed through a film blowing die. In the following process steps the polymer melt will be stretched to reduce thickness and to orientate the polymer chains bidirectional. This important step increases the mechanical properties of the produced film. During this process step, the remaining thickness profile of the film can be assigned to unequal flow resistances within the feeding system and film die, deposits at the die or an inaccurate centering of the blow head. After the extrusion process these differences are amplified by the cooling because of the different local stretch ratios or different local cooling air streams. Along the circumference of the bubble, local varying thickness is quick-frozen after crossing the frost-line. Even if the single most important objective for any blown film extrusion operation is to produce film that meets thickness specification [3] today s high quality multi-layer films have a thickness profile that can cause critical damage if wound-up on the film roll. As the thickness profile is fixed after crossing the frostline, on the one hand a very precise profile with low tolerances has to be achieved, on the other hand the following process steps have to deal with this profile to prevent damaged rolls. With a good process control and thickness measuring systems, today the local cooling of the bubble is influenced to change the local thickness by different cooling rates and stretch ratios. By the reversing haul-off system the fixed thickness profile is shifted along the width of the roll to prevent winding defects. To reduce the effects of wound-in thickness profiles and to prevent gauge bands, plastic deformation or drag down, the modern blown film lines have an integrated reversion. There are several different possibilities for a reversion or rotation-system at a blown film extrusion machine. Today s state of the art is a draw-up with a reversion integrated in the angle bar system. Nevertheless, all reversing or rotating machine parts between the extrusion line and draw-up aim to shift thickness profiles before the winding process. Journal of Plastics Technology 9 (2013) 4 162

4 Within an average film production, blown film lines have got a reversing draw-up which is set to a standard speed. The adjusted speed depends on polymer materials, bubble layers and flexibility of the produced film. If a stable process without any wrinkles in the draw-up is adjusted, the reversion speed will remain at the first setting. The reversion reduces the described critical effects of the thickness profile to roll quality. A certain statement to the range of this effect caused by reversion speed variation cannot be made so far. In the following figure the thickness of a five layer PE-EVOH film with a length of 4500 m is shown. The film has a layer thickness of ~52 μm. The thickness was measured after the production process by unwinding the film, that is why the effect of the reversion is displayed by the shifted thickness profile. Film thickness [μm] 2013 Carl Hanser Verlag, München Nicht zur Verwendung in Intranet- und Internet-Angeboten sowie elektronischen Verteilern. Wortberg, Heinzler Figure 1: Thickness profile arrangement on a film roll According to [4] and as seen in the figure, a film extrusion die line tends to produce a thick caliper area that runs the entire length of a roll or for that matter an entire work shift [4]. This caliper areas are shifted by the reversion but only very slowly. In a common production there are 3-5 reversion runs on 5000 m wound-up film. So the layers stored on the roll still do not compensate the thickness differences by the shifted profiles. The figure shows for example that areas with a high profile are still stored mainly on the right side of the roll. Journal of Plastics Technology 9 (2013) 4 163

5 The effect of the reversion is very small. This is a critical area for winding defects. If the minimized thickness profile is stored on a roll of about m of film, cumulated tolerances multiply profile differences. Some winding defects related to this effect are described in the following. During the winding process, a certain amount of air is wound-in between the different layers of film. This veils the overlapping profiles and their addition during the process. After the roll is finished with the required web meters, the living film shrinks and the air amount between the layers diminishes. Entrained air is needed to compensate wound in stress and shrink. The effects of the resulting stress can be amplified through a critical setup of the thickness profile and veiled by the wound-in air. When wound-in air is pressed out of the roll by increasing stress and shrink, the thickness profiles have no buffer any longer and areas with a strong positive profile add up. Gauge bands or areas with increased hardness occur. 3 WINDING DEFECTS During the winding process a local larger roll diameter is build up through the reinforcement of the thickness caliper. These gauge bands can damage the film and cause problems during further processing. Even though not every diameter difference can be seen from outside the roll, especially local high tension caused by small diameter differences and unequal shrink lead to critical defects inside the roll. Wound-in stress is amplified by shrinkage during the storage. On the one hand shrinkage is mass-dependent and areas with local arranged high thickness profiles have a different shrinkage behavior than areas with lower profiles. On the other hand the remaining air between the film layers is pressed out of areas with larger diameters and the layers get into direct contact during the shrink process after the production. This leads to areas with high stress and high roll hardness. Examples for these defects are shown in the following figure. As the roll needs a level of wound-in tension to be stable, a local tension peak will result in a higher stretch level. When the roll is used for further processing, the film that is locally more stretched will cause drag down or shows plastic deformations. Some winding defects are shown as examples in figure 2. Figure 2: Different winding defects Journal of Plastics Technology 9 (2013) 4 164

6 These critical areas cannot be seen from outside the roll and the damaged layers occur during further processing. To correlate the shown defects, the process conditions and the film thickness parameters, a new model based optimization tool was developed at the University of Duisburg-Essen. To identify optimizations for process parameters and process control, the algorithm and setup of the calculation bases will be discussed in the following. 4 MODEL BASED CALCULATION SETUP The analysis focuses on a longitudinal cut along the width of the roll in cross direction (CD). Within this view, an addition of layers can directly be shown as progress or diagram for every new layer. With the given start setup some mandatory factors have to be calculated. The prognostic tool is based on geometric correlations. Therefore some simplifications and assumptions have to be set to reduce complexity of the winding process of blown film to a manageable prognostic model. The thickness profile of the film will be treated as thickness information spots according to the measuring accuracy. To increase the calculation accuracy, it is possible to approximate the thickness profile with additional calculation spots between the measured values as a spline function. This is important to realize the reversion effect at low roll diameters and high rotation speeds. In a second step the winding process is reduced from an Archimedean spiral to a layer based system. The build-up process is seen as adding new layers above the one before. Every layer n x is seen as a closed ring as shown in figure 3. Nevertheless, the constant influence of the reversion system during the build-up process will be considered and calculated as a shift factor for every information spot continuously. Figure 3: Layer System of the Prognostic Model Journal of Plastics Technology 9 (2013) 4 165

7 Within the analysis of the winding process and through the described assumptions, every local thickness spot can be described as a line being transported from the extrusion die to the winder. Between these processes, extrusion, winding and storage on the roll, the lines are shifted along the width of the film. The following figure shows the reduced setup of the model with the winding process. The distance between measurement of the thickness profile and winder is constant. Therefore, the time difference between measurement of the thickness profile and winding process can be ignored. As an example, the line of one measurement spot being shifted and transferred to the roll is outlined. Of course the outlined transportation way of one spot along the film width is reliant to the setup of the reversion system. This point and possible improvements will be discussed in the following. Figure 4: Layout of the prognostic Model 5 CALCULATION BASES The given thickness profile leads to the average thickness as a mean value. This factor is important for non-local effects within the build-up process such as the average radius r a or diameter d a of the roll. The average radius is calculated via an equitation depending on the core diameter and an addition of the layers Journal of Plastics Technology 9 (2013) 4 166

8 with average thickness h m per process time N s (t). By using the average radius, the time of circulation can by calculated. It does not base on local effects which would falsify the results as the production speed is to be seen as constant. T cir r ( t) ( t) a = 2 π (1) vb The time of circulation T cir is important for the build-up process and the constant speed of the film web. As the first prognostic model will not consider elastic stretch and wound in stress as a result of different local radii, speed differences cannot be allowed within the calculation. Conversely, when a difference in the diameter is located through the analysis, it indicates the critical areas as mentioned before. Higher stress levels can result in defects of the roll and film web indicated by the local layer setup. A good measurement of the thickness profile results in a good prognostic of the profile positioning during the process. By using a shift factor W d, the model calculates whether the profile is shifted at least one thickness block during one rotation of the winder or not. With a high accuracy and approximated splines between the measured values, even small shifts at the start of the process can be calculated. In a first step, the range of the shifting for every measurement point over the circumference has to be calculated through the following equation. W ( t) = T ( t) v (2) d cir rev This equation contains the range of the shifting W d depending on the process time t. The circulation time T cir increases during the process. For every new layer T cir has to be recalculated. By increasing the diameter of the roll, the influence of the reversion increases too. The model only prognosticates the build-up process for a cut along the roll width. Therefore, the shift factor is always calculated for the outer line or the last layer. If the range of shifting is not within the measurement steps, there has to be a curve fitting to decide if a profile block is shifted from one to the next layer or not. This underlines why good measurement accuracy is important to increase the prognostic reliability. Figure 5: Shift factor to calculate the reversion effect Journal of Plastics Technology 9 (2013) 4 167

9 For the last layers, when the shift factor increases to a lot more than 10 blocks, accuracy is no longer mandatory. To reproduce the build-up of the first layers, where only a small shifting takes place, a measurement with very few blind spots is needed to show the small shifting of the profile during the short rotation times of the winder. Within a last step, for every layer and every measurement point, the direction of rotation has to be considered. 6 PROCESS SETUP WITHIN THE CALCULATION MODEL The setup of the tool is very flexible and can be adjusted to the process conditions. The main influencing variables to be adjusted at the start are: measured thickness profile along 360 circumference as a matrix with the number of approximated calculation steps, width of the roll b [mm], winding speed or production speed v b [m/min] and the core diameter r 0 [mm]. It can be decided if the film shall be treated as a web or tube. The reversion speed v rev has to be set as a profile of time and rotation angle. For reproducing the build-up process of standard productions, a constant profile would be sufficient. For the integration of improvements, profiles as shown in comparison in the following figure are required. Figure 6: angle [ ] time [min] Reversion profile setups With increasing time of circulation, the shift of defined thickness profile blocks by reversion can be determined. If you consider one block of the thickness profile being shifted by the reversion, this would result in a time based oscillation of this block over the width of the film web or the rolls. Through different rotation times of the winder the reversion has an increasing effect on the build-up process, since as the oscillation time of the thickness blocks is constant according to the reversion speed. Journal of Plastics Technology 9 (2013) angle [ ] time [min]

10 The thickness profile is imported as a.csv-data. According to the production, an updated profile can be set for different measurement points during the calculation. So it is possible to e.g. update the profile every 1000 m of produced film. As output, a direct figure with the layer setup on the roll is displayed as total profile along the width of the roll or relative profile to the median profile diameter. For detailed views, the calculated results can be exported and the scaling of the figure is adjustable. 7 INFLUENCES AT THE START OF THE WINDING PROCESS At the start of the winding process, new layers are added to the roll very fast. Low reversion speeds will have a very minor effect on the positioning within this state of the process. For the worst case, the layers will be wound-up without a shift of the thickness profile. Especially at the start of the process and the first layers this is very critical. In the following, this part of the roll will have the highest tension by shrink and process setup. So if in this part the profile maximal are stored directly above each other, defects by high stress levels can occur very easy. Investigations of the areas within the rolls, where defects occur most, have shown that on the one hand the sides of a roll and the other hand first layers are critical. At the sides of a roll of i.e. a contact winder system the pressure application is directly passed to the roll. In the middle of the roll, the pressure application and therefore wound-in stress is reduced because of the deflection of the contact roll axle. Possible improvements with these boundary conditions will be discussed with an production example. The thickness profile used for the calculation was randomly measured at a industrial blown film extrusion line for packaging films. thickness profile [mm] Figure 7: film width [mm] Example of a film thickness profile in a production (measured) For a better comparison of the following relative roll diameter, the mean roll diameter for some web meters wound on a roll are shown in table 1. Journal of Plastics Technology 9 (2013) 4 169

11 Web Meter Mean Roll Diameter 500 m ~170 mm 1000 m ~200 mm 2000 m ~374 mm 3000 m ~506 mm Table 1: Mean roll diameter for different wound up web meters To show the described effects of the reversion speed on the first layers, the film profile as shown in figure 1 is used for the calculation. The profile maximum is shifted slowly during the process from left to right on the roll and backwards. Figure 7 shows the thickness profile for the calculation. The process conditions are width of the roll 1200 mm, production speed 200 m/min and a constant reversion speed of 6 min/360. The used core diameter was set to standard 3 cores. Of course, a larger core diameter would increase the effect of the reversion at the start of the winding process, however in the following this setup will be seen as fixed production standards. relative diameter [ ] Figure 8: Final Layer 100m roll width [mm] Relative thickness profile for the first 100 m on a film roll In figure 8, the relative roll profile for the first 100 m wound-up film is shown for every 100 th layer. As shown in the picture, the first layers are added to the roll with nearly no influence of the reversion. So the thickness profile builds up local differences that can lead to high stress levels. Unfortunately, the main peaks of the profile are stored at the edges of the roll, where the applied pressure is at its maximum. If the first 1000 m and every 500 th layer is considered, a slow effect of the reversing haul-off system levels the totalized roll profile. Nevertheless, the roll profile that is build-up with the first web meters cannot be compensated by Journal of Plastics Technology 9 (2013) angle [ ] time [min]

12 the shifting in the following wound-up web meter. As a result there remains a maximum on the left side and a low profile on the right side. relative diameter [ ] Figure 9: Final Layer 1000m roll width [mm] Relative thickness profile for the first 1000 m Even in the following production process, there will still remain the influence of the start of the winding process. The following web meters will be wound on much less layers because of the increasing roll diameter. The effect and shifting of the reversion will adjust the thickness profile much better to the roll, but the first m to the core will mainly be influenced by the direct totalized thickness profile of the film. This far air entrainment and air buffer between the layers are not considered. In a real process, this buffer would compensate a small part of the effects. Nevertheless, the air buffer will be pressed aside at the critical areas and result in a direct contact of the layers. As an interpretation of the results it can be assumed that not every maximum will result in a gauge band. But there will be different hardness levels and the areas with high local amplitudes will result in critical stress. To increase the roll quality and to reduce critical areas within the roll, the first possibility is to increase the reversion speed. The higher speed will shift the profile faster and will have a larger influence on the first wound-up layers. Because of the high rotation speed of the winder and therefore the fast build-up of the first 1000 layers, will be effected by the reversion limited. At a production speed of 200 m/min the first 1000 layers are built up within 6 min with exponential tendencies for the following layers. So the effect of the higher shift rate will have a positive effect but not compensate the defects in the first web meters. In most production processes, the maximum speed is limited by the film material composition and the machine properties. It has to be prevented that the whole bubble is shifted during the extrusion process and turned out of the die. That would influence the process stability. Other effects are wrinkles on the film during the haul-off process. It can be said that the reversion speed is a limited but important process parameter. At the start of the winding process the high Journal of Plastics Technology 9 (2013) angle [ ] time [min]

13 rotation speed recommends the maximum reversion speed to adjust the film profile on the roll properly. Limited by the described process requirements and fixed process setup for the thickness profile and a maximum production speed, advanced process control is necessary to reduce possible defects. Because of the continuously increased roll diameter during the winding process, the reversion affects the adjustment of the thickness profile with increasing influence. Unfortunately, the outer layers and last web meter of the roll are not critical in reference to the described defects. That implements possible improvements to prevent winding defects by compensating the bad adjusted thickness profile within the first layers and web meters. 8 ENHANCED PROCESS QUALITY BY OPTIMIZED REVERSION CONTROL The described investigations to winding defects have shown that the defect occurrence at the edge of a roll is much higher than in the middle. That can be explained by the deflection of the contact roll and therefore the lower wound-in tension or pressure in this area. The remaining air buffer is higher and can compensate local tension and shrink. The first improvement to reduce the defect occurrence, if the film profile and production process is considered as fixed, is to prepare the start of a new roll during the last web meters of the previous roll. The last web meters of a roll can be used to adjust the critical high local thickness profile to the middle of the roll at the start of a new winding process. The large diameter of film rolls at the end of a winding process enables a very precise positioning without reducing the roll quality or disturbing the production process. For the new roll an optimized setup to reduce the tension in critical areas is configured. With the proper adjustment, the reversion speed is at its process-depended maximum and local thickness peaks are located at the middle of the roll width. An example is shown in the following figure. The film profile is identical to the one of the previous example but the positioning on the roll is adjusted. The resulting maximums are setup in the middle of the roll width to reduce the defect possibility. Journal of Plastics Technology 9 (2013) 4 172

14 relative diameter [ ] Figure 10: Final Layer 1000m roll width [mm] Relative thickness profile with adjusted maximum position The second improvement is an adaption of the reversion direction to the actual roll thickness profile. Because of the servo drive that powers the reversing hauloff it is possible to change the rotation direction as fast as the film bubble remains stable. It is not necessary to turn the haul-off system 360 until the rotation direction is changed. By an advanced process control, the rotation direction and speed can be adjusted to optimize the resulting roll thickness profile. It is important to prevent areas with high local amplitudes which result in high tension peaks and winding defects. This improvement cannot influence the first 1000 web meters because of the high winding speed and small roll diameter. By a continuous calculation and direct control of the reversion, the film profile can be used to even the differences during the following build-up process. Of course a random effect to even the profile occurs with normal reversion setups, however this effect can be mandatorily improved by a direct control. This directly increases the roll quality and reduces critical local tension peaks. To show this effect, an example calculation with just a small change in the reversion profile is shown in figure 11. The reversing haul-off does not rotate 360 but follows the profile and changes the rotation direction at 180 again. Of course, the first layers are not influenced by the setup but as shown in the figure, the effect starts at layer 2000 where the difference is reduced from a maximum of more than 6 to less about 5,6. The main effect can be seen in the following 2000 m added to the roll. Because of the optimized reversion profile, the total thickness profile on the roll is equalized and will reduce the tension differences. This small improvement shows the potential of a direct reversion control to optimize the total roll thickness profile linked to the actual extrusion process. Journal of Plastics Technology 9 (2013) angle [ ] time [min]

15 relative diameter [ ] Figure 11: Final Layer 3000m roll width [mm] Relative thickness profile with adjusted maximum position and reversion profile As the reversion speed is limited to the process properties and produced film, the reaction time of this control system is limited too. To enhance the roll quality further on, the cooling of the bubble has to be integrated into the control chain. Today, the film profile can be influenced by the cooling system to adjust a better thickness profile. If the local peaks are overcompensated, a local maximum will be followed by a local minimum in the same area. If the reversion cannot react fast enough to even the roll profile, this is another possibility to secure proper film roll quality. In the simulation, this can be integrated by an update of the used thickness profile for the calculation. 9 DISCUSSION AND CONCLUSIONS Reasons for roll defects depend on very different factors. Even the described influence of the reversion is only one part and cannot be seen as a single task. It is a combination of the cooling, the quality of the die and the maintenance of the extrusion line and the accurate setup of the winding parameters for the product. The described tool can display influences between the resulting thickness profile in the extrusion- and cooling process and the winding setup. The prognostic of the build-up process indicates critical areas and optimization potentials. Still, this is no automated process, but the machine operator gets another indication to optimize the machine parameters for production. In combination with hardness measurement, existing defects can be analyzed and solved with a calculation for different reversion setups. Even though the tool does not consider influences of air entrainment, the results indicate the critical process areas and show effects of parameter variations. To Journal of Plastics Technology 9 (2013) angle [ ] time [min]

16 consider thickness profile positioning within the process by adjusting the cooling process, new profiles can be read in to be considered in the calculation. By this a direct integration would be possible. First results within the research project underline the important role of the thickness profile positioning within the winding process. To prevent defects, it is important that thickness profile spreading has to be compensated on the roll. Otherwise, the error probability increases. The developed tool does not automatically solve this problem but shows optimization potentials if defects occur within the production and a possibility to setup a control chain for enhanced roll quality. It is recommended that the possibility to optimize the start process for new rolls, is integrated into today s blown film line control. In addition, the calculation and online optimization to control the reversion profile for an optimized thickness profile on the film roll has to be integrated as a new process control option. Acknowledgements This project is supported by ERDF European Regional Development Fund Investition in unsere Zukunft NRW Ziel-2 Program CheK.NRW Chemie und Kunststofftechnik Title: Maßnahmen zur Erhöhung der Rohstoffeffizienz bei der Kunststofffolienherstellung In cooperation with: Windmöller & Hölscher KG (Lengerich, Germany); Kobusch Sengewald GmbH (Halle/Westfl., Germany) Journal of Plastics Technology 9 (2013) 4 175

17 References [1] PlasticsEurope An analysis of European plastics production, demand and waste data for 2011 [2] Wortberg, J.; Saul, K. PlasticsEurope Market Research Group, 2012 Potentials of energy-efficiency film-extrusion Packaging Films, 2011 [3] Cantor, K. Blown Film Extrusion [4] Good, J. ; Roisum, D. [5] Heinzler, F.A; Wortberg, J Carl Hanser, München, p. 126, 2006 Winding- Machines, mechanics and measurement Lancaster, DEStech Publications, 2008 Thickness profile effects on the build-up process of film rolls Society of Plastics Engineering Annual Technical Conference (SPE Antec), , Orlando (USA) Keywords: reversion, haul-off, winding defects, optimized process control, roll quality Stichworte: Reversion, Folienabzug, Wickeldefekte, optimierte Prozesskontrolle, Rollenqualität Journal of Plastics Technology 9 (2013) 4 176

18 Autor/author: Dipl.-Ing. Felix A. Heinzler Prof. Dr.-Ing. Johannes Wortberg Universität Duisburg-Essen Institut für Produkt Engineering Lotharstr Duisburg Herausgeber/Editor: Europa/Europe Prof. Dr.-Ing. Dr. h.c. Gottfried W. Ehrenstein, verantwortlich Lehrstuhl für Kunststofftechnik Universität Erlangen-Nürnberg Am Weichselgarten Erlangen Deutschland Phone: +49/(0)9131/ Fax.: +49/(0)9131/ Adresse: ehrenstein@lkt.uni-erlangen.de Verlag/Publisher: Carl-Hanser-Verlag Jürgen Harth Ltg. Online-Services & E-Commerce, Fachbuchanzeigen und Elektronische Lizenzen Kolbergerstrasse Muenchen Tel.: 089/ Fax: 089/ Adresse: harth@hanser.de -Adresse: felix.heinzler@uni-due.de Webseite: Tel.: +49(0) Fax: +49(0) Amerika/The Americas Prof. Prof. h.c Dr. Tim A. Osswald, responsible Polymer Engineering Center, Director University of Wisconsin-Madison 1513 University Avenue Madison, WI USA Phone: +1/ Fax.: +1/ Adresse: osswald@engr.wisc.edu Beirat/Editorial Board: Professoren des Wissenschaftlichen Arbeitskreises Kunststofftechnik/ Professors of the Scientific Alliance of Polymer Technology Journal of Plastics Technology 9 (2013) 4 177