Web Guiding And Spreading Systems
Web guiding and spreading systems offer improved quality and productivity in the textile industry.
Udo Skarke
T
oday, the manufacturers and users of processing machines for web-type materials are
confronted with ever-increasing demands, such as faster and more precise production processes,
improved product quality; and reduced personnel, waste and, above all, downtime. Web guiding
systems decisively fulfill these requirements.
Principle
Typically, web-type materials are fed from a reel to the machine, processed and then rewound. During these stages, various position errors may occur. Web guiding systems are designed to eliminate these negative process influences and assure permanent, precise web alignment and winding. Depending on the type of material application and task, a wide variety of systems are specially designed to improve quality and increase productivity.
In web guiding systems, a sensor detects the web position compared to a reference point. This is usually the web edge, but it may be a printed line or a strong color contrast on the web. The current actual web position value is compared with the set value by the controller, which then sends the difference of these two values as a signal to the system-actuating element, which, in turn, corrects web travel.
Detection Systems
With progressive technology, detection systems have come a long way from being simple mechanical sensors to sophisticated digital infrared sensors, wide-band arrays, or charge-coupled device (CCD) cameras. The right choice of sensor specific to the application is important to guarantee optimal results.
Infrared sensors are in wide use, for example, in tenter infeed systems, highly accurate edge guiding on printing lines, and center-positioning on laminating processes. These sensors typically have a very narrow detection range and, therefore, provide highly accurate detection of any type of edge. In principle, an optoelectronic, infrared edge sensor distinguishes itself by a highly compact and stable construction with an integrated CCD chip. Due to the permanent adjustment of the sensor to ambient conditions, practically all webs can be reliably scanned, including those with very little light reflection.
Wide band sensors allow various-width materials to be processed without mechanical sensor position changes (See Figure 1). The sensor operates with infrared transmitters and receivers placed on opposite faces of the web, and senses the edges using special scanning techniques. It is, however, not as accurate as a stand-alone infrared edge detector and is primarily used for guiding applications in which less precision can be tolerated. Detection accuracies can vary from 3 to 7 millimeters (mm), depending on the technology used. Wide band sensors can be used for edge detection and center guiding, and, because of their construction, also as width monitors.
Figure 1: Wide band sensors can be used for edge detection, center guiding and width monitoring.
Correction Devices
There is a wide range of different correction devices available in combination with the different detection systems to make a perfect fit to any process in the textile industry. Subject to the application and the fabric type, the device may be a segmented roller guide, a steering roller, a pivoting frame or a web guider.
The most economical guiders - the well-known two-roll edge guiders - have been around for decades. The web edge is detected either mechanically by a sensor lever or without contact using optoelectronics. The sensor signal controls a diaphragm cylinder or a lifting magnet that presses the control roller against the counter pressure roller. The web edge is controlled by roller offset and nip pressure. For more accurate edge guiding, a built-in broadband sensor with web edge fluctuations up to +/- 80 mm is available due to the large scanning range - 120 mm - of the infrared sensor system. For delicate webs, an additional electrical drive for the top roller ensures that the friction torque on the rollers is compensated and stretching of the web is avoided.
A steering roller assembly consists of two or more rollers and performs two different movements in one correction procedure (See Figure 2). First, it tilts toward the web direction of travel to achieve a continuous righting of the moving web. Second, it assumes a lateral offset vertical to the web direction of travel to effect an immediate reparation. This rectifying action is achieved by a lever system as shown in the sketch. The web must be friction-locked to the guide rollers.
Figure 2: Steering roller assemblies perform two different movements in one correction procedure.
The segmented roller guider is the optimum web guiding system for all applications across the entire textile-processing spectrum (See Figure 3). It guides woven, knitted, and, to a certain extent, nonwoven fabrics in dry, damp or dripping wet conditions, in steamers exposed to high temperature and finishing chemicals. In the event of major corrections, the guider maintains a uniform distribution of tension across the web, thus minimizing weft distortion. The web rests on the guiding slats along its full width. The slats carry the web around the roll while moving laterally, providing a minimum offset - thus eliminating the risk of a skewed web. The guide rollers can be designed with split slats and perform web guiding and web spreading simultaneously. Scroll rollers or pneumatic uncurlers can also be added for uncurling and additional spreading capability.
Figure 3: Segmented roller guiders maintain uniform distribution of tension across woven, knitted or nonwoven webs.
A good degree of friction between the segmented roller guiding slats and the fabric web is essential for an efficient web guiding process. Many modern quality fabrics feature extremely sensitive surfaces that may be slightly impaired by the contact areas of the guiding slats should these be too aggressive. Various slat coverings offer the possibility to process these fabrics safely.
Tenter rail guiding systems ensure precise positioning of tenter frame clips or pins to the edges of the fabric at the infeed of the tenter frame, which is critical to producing quality fabric with consistent width (See Figure 4). As speeds have greatly increased, this control has been improved through the development of highly accurate infrared edge sensors, digital controllers, and positioners with encoder feedback. The rails can be moved at rates from 120 to 180 mm per second to exactly follow the fabric edges.
Figure 4: Tenter rail guiding systems ensure precise positioning of tenter frame clips or pins to the fabric edges at the infeed of the tenter frame.
Many textile processes require the use of unwind or rewind systems to properly control the fabric into the process and to produce rolls of fabric with uniform edges at the rewind station. Various sensors - such as edge, line, or center-guiding - can be used; and various actuators are available for different strokes and forces.
A range of control systems consisting of sensors, controllers and actuators can be adapted for many other positioning applications, such as coater-dam positioning and slitter positioning, for example.
Heightened Control
Despite a consistent specialization in web guiding systems for the various automation and production processes in the textile industry, a broad range of products, from individual mechanical components to multifunctional systems, is available to meet the requirements. This means that even the most complex projects may be completed cost-effectively. These efficiency solutions provide manufacturers with heightened control of processing variables, which ultimately increases productivity, reduces waste, and improves the quality of the end product.
Editor's Note: Udo Skarke is CEO of Erhardt + Leimer Inc., United States.
October/November/December 2009
Principle
Typically, web-type materials are fed from a reel to the machine, processed and then rewound. During these stages, various position errors may occur. Web guiding systems are designed to eliminate these negative process influences and assure permanent, precise web alignment and winding. Depending on the type of material application and task, a wide variety of systems are specially designed to improve quality and increase productivity.
In web guiding systems, a sensor detects the web position compared to a reference point. This is usually the web edge, but it may be a printed line or a strong color contrast on the web. The current actual web position value is compared with the set value by the controller, which then sends the difference of these two values as a signal to the system-actuating element, which, in turn, corrects web travel.
Detection Systems
With progressive technology, detection systems have come a long way from being simple mechanical sensors to sophisticated digital infrared sensors, wide-band arrays, or charge-coupled device (CCD) cameras. The right choice of sensor specific to the application is important to guarantee optimal results.
Infrared sensors are in wide use, for example, in tenter infeed systems, highly accurate edge guiding on printing lines, and center-positioning on laminating processes. These sensors typically have a very narrow detection range and, therefore, provide highly accurate detection of any type of edge. In principle, an optoelectronic, infrared edge sensor distinguishes itself by a highly compact and stable construction with an integrated CCD chip. Due to the permanent adjustment of the sensor to ambient conditions, practically all webs can be reliably scanned, including those with very little light reflection.
Wide band sensors allow various-width materials to be processed without mechanical sensor position changes (See Figure 1). The sensor operates with infrared transmitters and receivers placed on opposite faces of the web, and senses the edges using special scanning techniques. It is, however, not as accurate as a stand-alone infrared edge detector and is primarily used for guiding applications in which less precision can be tolerated. Detection accuracies can vary from 3 to 7 millimeters (mm), depending on the technology used. Wide band sensors can be used for edge detection and center guiding, and, because of their construction, also as width monitors.
Figure 1: Wide band sensors can be used for edge detection, center guiding and width monitoring.
Correction Devices
There is a wide range of different correction devices available in combination with the different detection systems to make a perfect fit to any process in the textile industry. Subject to the application and the fabric type, the device may be a segmented roller guide, a steering roller, a pivoting frame or a web guider.
The most economical guiders - the well-known two-roll edge guiders - have been around for decades. The web edge is detected either mechanically by a sensor lever or without contact using optoelectronics. The sensor signal controls a diaphragm cylinder or a lifting magnet that presses the control roller against the counter pressure roller. The web edge is controlled by roller offset and nip pressure. For more accurate edge guiding, a built-in broadband sensor with web edge fluctuations up to +/- 80 mm is available due to the large scanning range - 120 mm - of the infrared sensor system. For delicate webs, an additional electrical drive for the top roller ensures that the friction torque on the rollers is compensated and stretching of the web is avoided.
A steering roller assembly consists of two or more rollers and performs two different movements in one correction procedure (See Figure 2). First, it tilts toward the web direction of travel to achieve a continuous righting of the moving web. Second, it assumes a lateral offset vertical to the web direction of travel to effect an immediate reparation. This rectifying action is achieved by a lever system as shown in the sketch. The web must be friction-locked to the guide rollers.
Figure 2: Steering roller assemblies perform two different movements in one correction procedure.
The segmented roller guider is the optimum web guiding system for all applications across the entire textile-processing spectrum (See Figure 3). It guides woven, knitted, and, to a certain extent, nonwoven fabrics in dry, damp or dripping wet conditions, in steamers exposed to high temperature and finishing chemicals. In the event of major corrections, the guider maintains a uniform distribution of tension across the web, thus minimizing weft distortion. The web rests on the guiding slats along its full width. The slats carry the web around the roll while moving laterally, providing a minimum offset - thus eliminating the risk of a skewed web. The guide rollers can be designed with split slats and perform web guiding and web spreading simultaneously. Scroll rollers or pneumatic uncurlers can also be added for uncurling and additional spreading capability.
Figure 3: Segmented roller guiders maintain uniform distribution of tension across woven, knitted or nonwoven webs.
A good degree of friction between the segmented roller guiding slats and the fabric web is essential for an efficient web guiding process. Many modern quality fabrics feature extremely sensitive surfaces that may be slightly impaired by the contact areas of the guiding slats should these be too aggressive. Various slat coverings offer the possibility to process these fabrics safely.
Tenter rail guiding systems ensure precise positioning of tenter frame clips or pins to the edges of the fabric at the infeed of the tenter frame, which is critical to producing quality fabric with consistent width (See Figure 4). As speeds have greatly increased, this control has been improved through the development of highly accurate infrared edge sensors, digital controllers, and positioners with encoder feedback. The rails can be moved at rates from 120 to 180 mm per second to exactly follow the fabric edges.
Figure 4: Tenter rail guiding systems ensure precise positioning of tenter frame clips or pins to the fabric edges at the infeed of the tenter frame.
Many textile processes require the use of unwind or rewind systems to properly control the fabric into the process and to produce rolls of fabric with uniform edges at the rewind station. Various sensors - such as edge, line, or center-guiding - can be used; and various actuators are available for different strokes and forces.
A range of control systems consisting of sensors, controllers and actuators can be adapted for many other positioning applications, such as coater-dam positioning and slitter positioning, for example.
Heightened Control
Despite a consistent specialization in web guiding systems for the various automation and production processes in the textile industry, a broad range of products, from individual mechanical components to multifunctional systems, is available to meet the requirements. This means that even the most complex projects may be completed cost-effectively. These efficiency solutions provide manufacturers with heightened control of processing variables, which ultimately increases productivity, reduces waste, and improves the quality of the end product.
Editor's Note: Udo Skarke is CEO of Erhardt + Leimer Inc., United States.
October/November/December 2009
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网引导和伸展系统
今天，网状材料的生产商和加工机械的用户遇到了不断增长的要求，例如更快、更精确的
生产加工，更高的产品质量，减少人员和浪费，以及减少停工期。网引导系统可以完全满足
这些要求。
原则
网状原料通常是通过卷筒向机器喂料、加工并重新绕线。在这些步骤里，各种位置错误可
能发生。网引导系统的设计就是为了消除这些不利的加工因素，确保固定的、精确的网线
对齐和卷绕。根据原料应用和任务类型的不同，有各种特殊设计的系统用来提高质量和改
进生产力。
在网引导系统中，传感器可以通过与参照点比较而探测到网的位置。这通常是网的边缘，
但它也有可能是印花线或者是网上一根相比之下颜色更深的线。目前实际的网的位置值
通过控制器与设置值进行比较，控制器再把两个值的不同之处通过信号向系统激活元素原
件，这样反过来校正网的移动。
检测系统
随着技术的进步，检测系统也经过了一个漫长的发展历程，从简单的机械传感器到复杂的
数字红外线传感器，宽带阵列，或电荷耦合装置（CCD）摄像头。针对不同应用选择正确的传
感器对确保最佳结果非常重要。
红外线传感器被广泛使用，例如，在拉幅机给料系统，在印花线上的高精度边缘导向，以及
层压加工中的中心定位。这些传感器通常来说检测范围非常窄，因此对任何种类的边缘都
能提供非常精确的检测。原则上，光电的红外线边缘传感器通过一个非常袖珍的、稳定的
结构，加上一个集成的CCD芯片显示出自己的独特之处。由于传感器根据周围环境做了永
久性调整，实际上所有的网都能够可靠的被扫描，包括那些反光非常少的网。
宽带传感器可以支持各种幅宽的原料，而无需对传感器的位置做机械调整
（见图1）。这种
传感器通过安装在网上对面的红外传输和接收器进行操作，通过特殊的扫描技术感应边缘。
但是，它不像独立的红外边缘探测器那么精确，主要被用在可以容许不太精确的地方做引
导。根据所用的技术不同，探测精确度的范围从3-7毫米（mm）。由于它们的自身构造，宽带
传感器能用在边缘探测和中心引导，也可以当做幅度监控器。
图1：宽带传感器能被用于边缘检测，中心引导和宽度控制。
校正装置
结合不同的检测系统，有大量的不同的校正装置适合在纺织产业的任何加工过程中使用。
根据应用及面料的种类，这种装置可能是一个分段皮辊导向，一个转向辊，一个绕轴旋转架
或是一个网引导器。
最经济的引导器——著名的双辊边缘引导器——已经有数十年的历史了。网的边缘要么通过
传感器杠杆机械的探测，要么通过光电技术非接触的探测。传感器信号控制一个膜片气缸
或一个起重磁盘挤压控制辊与反压辊相互作用。网的边缘通过皮辊偏移和钳压进行控制。
要达到更精确的边缘导向，可以用一个内置的宽频传感器，网的边缘波动不超过正负80毫
米——这是由于红外线传感器系统的最大扫描范围120毫米决定的。对于精细的网，需要在
顶部的皮辊上加一个额外的电子驱动，确保皮辊的摩擦转矩获得补偿，以及避免网的拉伸。
一个转向辊组合包括2个或更多的皮辊，在一次校正过程中执行两个不同的移动 （见图2）。
首先，它倾向网移动的方向以获得对移动的网的不断的校正。其次，它承担一个与网的移
动方向垂直的横向偏移，来影响一个即时的修补。这一矫正行动是通过草图上所显示的杠
杆系统来实现的。网必须与导线辊进行摩擦闭合。
图2：一个转向辊组合在一次校正过程中执行两个不同的移动。
分段皮辊导向器对于整个纺织加工范围的所有应用都是最佳的网导向系统 （见图3）。它可
以引导梭织、针织，以及在一定程度上引导非织造织物，可以在干、潮湿以及湿透的条件
下运行，也可以在暴露于高温和整理化学助剂的蒸筒里引导。在主要的校正活动中，导向
器保持了整个网上张力的统一分配，由此最大程度减少了纬纱变形。网顺着它的宽度在导
向板上搁置。横向移动时，条板带着网绕着皮辊，提供最大的偏移——这样就消除了歪斜的
网的风险。导向辊可以与两片条板设计到一起，同时进行网引导和网伸展。螺旋开幅辊或
气动解卷曲器也能够添加上去，以实现解卷曲及额外的伸展功能。
图3：分段皮辊导向器保持在梭织、针织或非织造网上统一的张力分配。
在分段皮辊导向条和织物网之间的好的摩擦度对于一个有效的网导向过程非常关键。很
多带有非常敏感的表面的现代优质织物，其表面在导向条接触过的区域可能被轻微的破
坏，非常挑剔。不同的条板包覆物提供了安全加工织物的可能性。
拉幅机轨道引导系统确保了拉幅机铗或针在拉幅机中进料的织物的边缘的精确定位，这对
生产始终如一幅宽的优质面料非常关键 （见图4）。由于速度已经大幅提升了，随着高度精
确的红外线边缘传感器、数字控制器以及带有编码器反馈的定位仪的发展，这一控制方式
也提高了。轨道可以以每秒120-180毫米的速度移动，精确的跟随织物边缘。
图4：拉幅机轨道引导系统确保拉幅机铗或针在拉幅机中进料的织物的边缘的精确定位。
很多纺织加工要求使用退卷或重卷系统来恰当的控制织物进入加工工序，在重卷位置生产
有统一边缘的一卷卷的织物。可以使用不同的传感器——例如边缘、线性或中心导向，对不
同的撞击和力量有不同的调节器。
包含了传感器、控制器和调节器的各种控制系统能适应很多其它的定位应用，例如涂层器
坝的定位和切条机定位。
提高控制
尽管在纺织行业中不同的自动化和生产过程的网引导系统在不断的专业化，市场上有范围
广阔的产品——从独立的机械组件到多功能的系统来满足需求。这意味着即使最复杂的项
目都能够经济的完成。这些有效的解决方案为制造商提供了对加工变量更高的控制力，这
最终能够提高生产力，减少浪费，并改进最终产品的品质。
编辑注：Udo Skarke是美国Erhardt + Leimer公司的首席执行官