Field of the invention
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The present disclosure relates to roller card system comprising a plurality of carding rollers being arranged in a roller card configuration and to methods for the operation of such roller card systems.
Description of the Related Art
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A carding machine is a commonly used machine in the textile and nonwoven industry to transform staple fibers into a uniform web with a homogeneous area weight in cross and machine direction. The machines takes a heavy pre-web, opens the fibers and converts it into an even nonwoven web with a defined area weight. Especially in the nonwoven industry these machines are running at high capacities and high production speeds. These so called roller cards have a significant impact on the quality of the final nonwoven product. Besides an even weight distribution, the fiber opening achieved in the card ensures a homogeneous web appearance. Fibers commonly used on these machines are for example cotton, wool, PES, PP, PLA, viscose or lyocell fibers in different length and diameter or mixtures of such fibers. Depending on the final application other fiber types are processed as well.
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At many Nonwoven production lines the roller cards represent the bottle neck to further increase the capacities of the lines. This is especially true for production lines where one or several cards directly feed the entangling unit. In these lines the unbonded web receives no further treatment, no so called crosslapper or any other machine is influencing the web design before bonding. Typically the capacity of these lines is described by either the achieved production speed at a certain product weight or as by the mass of fibers consumed per hour per meter working width of the card (capacity). The maximum production speed or capacity is reached, when a further speed increase would decrease the quality of the final product so that it does not meet the requirements any more. Currently, the product quality is either assessed by judging the visual appearance of the final product or by camera systems continuously detecting the homogeneity of the nonwoven web somewhere downstream after the exit of the card. Other commonly used systems are continuously detecting product properties like web weight, web thickness and moisture content. Also known are camera systems that are installed directly at the outlet of the carding machine to detect the orientation of the fibers.
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There is a constant need to increase the production capacity of roller card systems, to optimize the quality of the nonwoven products produced on a card and to improve process stability.
Summary
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When operating a roller card, a plurality of parameters are impacting the product quality and by this the maximally achievable capacity. The present inventors noticed that the amount of fiber fly in the carding machine is a good indicator of the process stability and often correlates with the quality of the nonwoven product being produced. The fiber fly is usually visible between the casing of the card and the rotating cylinders beside or underneath. The cylinders are usually referred to as breast roller(s), main cylinder, workers, strippers and doffers and can also comprise other rollers such as transfer systems or the like. All of these rollers are covered with so called card wires and rotate at speeds that can usually be adjusted individually. The fiber fly is depending on the machine design, for example roller diameters, the chosen card wire, direction of rotation, etc., but also on the machine settings, such as the rotation speed of the rollers or the material flow through the machine (which directly influences the capacity of the card). Further, the amount of fiber fly depends on the features and qualities of the processed fiber materials and also on the ambient conditions, especially the temperature and the humidity.
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Fiber fly can already be detected at low line speeds (and low capacities) and is increasing with an increase of the line speed (and capacity). Fiber fly can lead to unfavorable fiber aggregations in the form of bundles or longer tubes of fibers. Such tubes of fibers can collect at different places of the machine, very much depending on the machine design. Typical positions are at gaps of two or three rollers when their rotating directions and speeds fulfil certain requirements. The aggregations collect more and more fibers and at a certain point in time they get hooked and picked up by the wiring of a roller and end up as an agglomeration of fibers in the final product. These undesirable agglomerations create a disturbance in the homogeneity of the final product and are an important quality criteria. The less disturbances the better.
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With exceeding a certain number of disturbances, the produced materials have to be downgraded.
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To avoid fiber fly, some cards comprise suction systems that suck off excessive flying fibers. Nonetheless, this cannot completely rule out the formations of fiber agglomerations.
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According to current praxis, fiber fly is only visually detected by highly trained and experienced operating staff.
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The present disclosure is based on the idea to provide systems and methods that allow for a quantitative determination and record the amount of fiber fly.
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Such systems and methods could be used to find the optimal card settings for a specific product, support the optimization of machine components and to develop staple fibers and fiber mixtures specifically with the aim to improve the product quality and/or to increase the machine efficiency and its capacity.
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In one aspect, the present disclosure relates to a Roller card system comprising a plurality of carding rollers being arranged in a roller card configuration, wherein the roller card configuration is at least partly enclosed by at least one housing, wherein at least one area of possible fiber flight is defined within the housing, wherein the roller card system comprises at least one sensor system responsive to the fiber flight within the at least one area of possible fiber flight.
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With this system, the coverage of flying fibers in a specific area can be observed and measured either at a specific point in time or over a time period and an average coverage over a defined time period can be calculated. This coverage can be used as a quality assessment parameter, which can be expressed as a single figure describing the amount of fiber fly. The fiber fly depends on various factors, such as the specific build-up of the roller card system, the chosen operational settings (especially the speeds of the carding rollers and relative velocities or the carding roller surfaces), the surface structure of the carding rollers (also referred to as "card clothing"), the gaps between carding rollers facing each other, the current climate conditions and the properties of the fiber raw-material, i.e. the fiber blend fed to the roller card system. If one or more of these factors are changed in a systematic manner, the measured values allow for a quantitative statement on how much the fiber fly has improved (became less) or worsened (became more).
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According to a preferred embodiment, the at least one area of possible fiber flight is defined as the area where the highest fiber flight is expected at the intended maximal production speed.
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Fiber flight can occur on several areas in the roller card system and different areas can be more or less affected at different production speeds. Most relevant is the area of the highest (i.e. strongest) fiber flight under operation conditions, i.e. at the intended maximal production speed. But also other positions can provide valuable information about the production process.
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According to one preferred embodiment, the at least one area of possible fiber flight is located in the periphery of the main cylinder after the first worker at cylinder and before the first, second or third stripper at cylinder.
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Installing a sensor system responsive to the fiber flight in this area usually provides for a meaningful measurement result for many roller card designs.
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According to another embodiment, a plurality of areas of possible fiber flight can be defined within the housing, wherein the roller card system comprises at least one sensor system responsive to the fiber flight within each area of possible fiber flight.
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When observing more than one area, a more detailed analysis of the operation conditions can be obtained. This produces a plurality of measurement values, each characteristic for a different area of possible fiber flight, which can be used as a data set or combined to a single quality assessment parameter (e.g. by calculating a weighted or unweighted average). These values can be used for various optimization strategies. For example, the settings can be optimized to reduce fiber flight peak values and/or to reduce overall fiber flight.
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According to another preferred embodiment, the sensor system can be a light-based sensor system, preferably selected from a list comprising light sensors, light sensor arrays and camera systems.
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Such light-based sensor systems are easy to install and are available at reasonable costs. The light-based sensor can be combined with a backlight-device that is located on an opposite side of the area of possible fiber flight and oriented towards the light sensor. Fibers flying in the area of possible fiber flight obstruct the "view" of the sensor and darken the sensor so that the amount of light observed by the sensor is inversely proportional to fiber flight. A more detailed result can be acquired by the use of sensor arrays or camera systems. Camera systems have the additional advantage of providing a visual display of the area.
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According to another aspect, the present disclosure relates to an online control tool for a roller card system as disclosed herein, wherein the online control tool is adapted to receive at least one quality assessment parameter which is determined based on the measured fiber flight in an area of possible fiber flight, and to output at least one adjustment value for the adjustment of a quality affecting parameter.
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Such an online control tool can automatically suggests or implements setting changes based on the detected fiber fly to secure a constantly high process quality. Further, the adjustment value can be fed back to a control device of the roller card system to implement a closed-loop control system. It is also possible to quickly detect malfunctions at the card. The term "online", as it is used in this context, relates to a device that is connected to the roller card system during normal operation of the roller card.
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According to another aspect, the present disclosure relates to a method for providing at least one quality assessment parameter related to the operation of a roller card system, wherein the roller card system comprises a plurality of carding rollers being arranged in a roller card configuration, wherein the roller card configuration is at least partly enclosed by at least one housing, wherein at least one area of possible fiber flight is defined within the housing, and wherein the method comprises the step of measuring at least one measurement value representative for the degree of fiber flight within the at least one area of possible fiber flight and determining a quality assessment parameter based on the at least one measurement value.
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The method allows for an optimization of the operating conditions of a roller card system which can lead to a higher product quality and/or higher production speeds.
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In one preferred embodiment, the measurement value can be measured with at least one sensor system responsive to the fiber flight within the at least one area of possible fiber flight.
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For example, the measurement value can be a coverage rate, which allows the quality assessment parameter to be expressed as an average coverage rate.
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According to another preferred embodiment, the measurement value can comprise a light intensity measured by the sensor system.
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The light intensity is an easily observable parameter that is characteristic for the fiber flight in the direction of view of the sensor system, as the fibers obstruct the "view" of the sensor.
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According to one embodiment, the sensor system can be selected from a list comprising light sensors, light sensor arrays, camera systems or a combination thereof.
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Such sensor systems based on light are simple, resilient, economical and easy to install.
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According to another aspect, the present disclosure relates to a method for adjusting at least one quality affecting parameter of a roller card system as described herein, the method comprising the steps of determining at least one quality assessment parameter according to a method as described herein, and adjusting the at least one quality affecting parameter based on the assessment parameter.
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This allows for a systematic approach for an optimization of the operation of the roller card system. Further, this allows for the implementation of an online control tool at a production line that automatically suggests or implements setting changes based on the detected fiber fly.
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According to one preferred embodiment, the adjustment can be implemented as a closed-loop control system.
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Thereby, a quality control can be achieved that optimizes operation parameters during operation.
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According to another embodiment, the quality affecting variable can be selected from a list comprising a rotating speed of at least one carding roller, a fiber material feeding mass, a fiber material feeding speed, a fiber raw material property, such as a quality or a nature of the fiber raw material, an average fiber length, a fiber length distribution, a fiber blend composition of the fiber raw material.
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This allows for a systematic approach for optimizing the production line.
Brief Description of the Drawings
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Hereinafter, exemplary embodiments of the invention are described with reference to the drawings, wherein
- Fig. 1
- is a schematic drawing of a roller card system and
- Fig. 2
- is a diagram showing the results of a trial of a system as described herein.
Detailed Description of the Drawings
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Fig. 1 shows a schematic representation of an exemplary roller card system 1 . The roller card system 1 comprises a plurality of carding rollers 2 that are arranged in a roller card configuration. The carding rollers 2 are operated within a housing 3. Many different roller card configurations are possible and they are well-known by the skilled practitioners. Therefore, and for the sake of brevity, only the most important parts and their functions shall be shortly described herein.
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The roller card system 1 shown in Fig. 1 comprises one main cylinder 6 with five working units, each working unit comprising a stripper 7 and a worker 8. Two doffing units are arranged at the main cylinder 6, each doffing unit comprising a doffer 9, a pair of stuffing rollers 11 and a take-off roller arrangement 12. Further, a breast roller 15 is arranged in front of the main cylinder 6, the breast roller 15 comprising two working units.
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During operation, a pre-web 13 is fed to the roller card system 1 at a drawing in roller 10. The pre-web 13 is generally prepared by opening and mixing the raw material fibers in an opener and mixer (not shown) and fed to the roller card system 1 in the form of a rather thick but unstable fiber layer. The fibers are then first fed to the breast roller 15, where they are pre-oriented by the two working units, and then transferred to the main cylinder 6 where they are carded by the five main working units. Each doffer 9 detaches a layer of carded fibers from the main cylinder 6 and transfers it to the stuffing rollers 11, where the nonwoven material is condensed. The material is then stripped off by the take-off roller arrangement 12 and transferred to a transport unit, such as a moving belt arrangement, a roller arrangement or the like, which transports the still unbonded nonwoven web 14 to the next processing steps, which could be, for example, a spunlacing unit or any other device for bonding the fibers and strengthening the web.
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During operation and especially at high production speed, fibers tend to detach from the carding rollers 2 and fly around within the housing 3. This effect usually is strongest in the area of the first working units at the main cylinder. To surveil this area, an area of possible fiber flight 4 is defined slightly outside of the gap between the first two working units at the main cylinder 6. In this area of possible fiber flight fibers are detected by a sensor system 5, which is only schematically shown in Fig. 1. In a practical implementation the measuring direction of the sensor system 5 could be arranged essentially parallel to the axes of the carding rollers 2.
Examples:
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Three different fiber types were tested on a pilot line comprising a fiber opening and mixing system, a single roller card and a spunlacing unit with a dryer. The roller card system used in the pilot line was essentially of the type described above in connection with Fig. 1. All tests were conducted at the Institute for Material Science at Hof University under the supervision of Prof. Dr. Claus-Ekkehard Koukal and his team in collaboration with the inventors.
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A camera (model Keyence CA-H500C with a Keyence CA-LHR50 lens and respective controller equipment and software Keyence Vision Terminal) was mounted at the housing of the roller card system with the camera axis facing in a direction parallel to the rotational axis of the card rollers. The camera was oriented to face an LED area lamp arranged on the opposite side of the housing. The area between LED area lamp and the camera was located to cover an area of possible fiber flight in the periphery of the main cylinder shortly after the first worker at cylinder. With the carding equipment used, this was observed to be the area of increased fiber flight. Nonetheless, with other types of roller cards different areas could be more affected.
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The objective of the camera was focused to about the middle of the length of the rollers and the aperture was set to a small opening to maximize the depth of field. To reduce motion blur, the exposure time was set to a value where the motion blur is less than about 40% of the smallest particles to be detected.
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The operating team first compared the processing performance of all three fiber types visually. All of the three fiber types were tested at different processing speeds (50, 75 and 100 m/min) with the same product weight (50 g/m). Machine settings, fiber preparation and climate conditions were kept constant for all tests. In the visual assessment, fiber types 1 and 3 were judged by the operating team to have very similar processing behaviors, while fiber type 2 was judged to have a significantly better processing behavior. It is a well-known fact that with increasing processing speeds (equals to increased line capacities at constant product weight) the quality of the final product decreases. Therefore, it was expected that the rate of fiber fly also increases at higher speed. This expectation was confirmed by the visual impressions of the operating team. Fiber 2 was rated to show the best performance at all operating speeds (capacities). Fiber 1 and fiber 3 were rated to be similar in performance at increasing operating speeds (capacities).
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Each measurement consisted of 20 photos taken in a 0,5 s interval. For each photo, the percentage of pixels darkened by fibers was determined. The term "darkened", in this context, means a light intensity of less than 50% of the unobstructed light intensity. The average coverage rate [%] was calculated as the average percentage value of all 20 measurements.
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It should be noted that the measurement protocol as described above is given only as an example. According to the teachings disclosed herein, many different ways could be found to determine a meaningful and informative value that is representative for the fiber fly in a given roller card environment. It is not important to strictly follow one given measurement protocol, rather it is important to have a consistent measurement for a given roller card environment or a given type of roller card. This allows for a comparison of measurements made with different fiber materials and/or with different card settings, such as roller speeds, production speed and mass, roller distances, roller surface configuration etc. Based on the results, production procedures can be optimized.
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The results from the camera trials are shown in the diagram of Fig. 1. The diagram shows the measurement results for the three Fiber types during the previously described trial with the operating team at three different speeds, which are 50 m/min (dark grey), 75 m/min (light grey) and 100 m/min (medium grey). Fiber 2, the fiber with the visually better rated processing behavior, also shows significantly lower coverage rates at all speeds (capacities) when measured by the camera. The coverage rate increased from 3,06% at 50 m/min to 13,94% at 100 m/min which is inline with the expectation and the visual result.
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For Fiber 1, the coverage rate increased from 8,95% at 50 m/min to 48,14% at 100 m/min, while for Fiber 3 the coverage rate increased from 9,06% at 50m/min to 61,74% at 100 m/min. This confirms the visual impression but also indicates a performance difference between Fiber 1 and Fiber 3 at 100 m/min. This result shows that with the measurement of the fiber flight a different behavior of Fibers 1 and 3 could be determined, which was not observable by visual inspection. This gives reason to believe that the measurement of the fiber flight can allow for a better assessment of the production quality than it is currently possible with the visual inspection of highly experienced operating personnel.
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The trial set up described above and the results showed that the camera system is a reliable tool to measure the processing performance of a nonwoven roller card at defined conditions. With the value of the coverage rate it is possible not only to describe the differences qualitatively but also quantitatively with one figure. A higher coverage rate indicates a poor carding performance, while a lower coverage rate is a signal for a better performance. The values supplied by the camera system showed the expected impact by the chosen raw materials (fiber types) with all other conditions kept constant.
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A sensor system as described herein can also be used to analyze the impact of changing machine settings. In the trial set up described above, the line capacity was increased in three steps and the coverage rates increased as expected. This can be used to determine optimal machine settings for various fibers raw materials and/or fiber blends and give an indication on the quality of the produced nonwowen material.
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The trial proved that the camera system is suitable to reliably measure the fiber fly in a nonwoven roller card. The result can be output as a single value, i.e. the average coverage rate. The coverage rate enables the user of the system to directly judge the impact of any change of the raw material processed or ambient climate changes. It will as well allow to measure the impact of chosen machine settings (capacity, rotating or surface speeds, etc.) or the machine set up (gaps, card wires, diameters, etc.).
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The systems and methods described herein can be used for different applications, such as:
- Measuring the processing performance of raw materials at same machine settings (titer, cut length, finish, cross section, blend, etc.)
- Use known correlations between a pilot line and a production plant to apply insights won at the pilot line to the production plant
- Measure the processing performance of different card designs (cylinder diameters, arrangement of rollers, roller surface, etc.)
- Measure the performance of different components (card wire, fiber suction, casings, etc.)
- Optimize the card settings to maximize line throughput
- Implement a quality control tool based on the detected fiber fly during production
- Implement an online control tool at a production line that automatically suggests or implements setting changes based on the detected fiber fly
List of reference signs
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- Roller card system 1
- Carding rollers 2
- Housing 3
- Area of possible fiber flight 4
- Sensor system 5
- main cylinder 6
- stripper 7
- workers 8
- doffer 9
- drawing in roller 10
- stuffing roller 11
- take-off roller arrangement 12
- Pre-web 13
- Unbonded nonwoven web 14
- Breast roller 15