Non-contact detection of velocity and length in the converting and textile industry

Velocity measurement on roll-fed material and piece goods

Velocity measurement is indispensable for process control and optimization in many industrial processes. It is the basis for many other applications such as cut length control, length measurement and velocity difference measurement. In these processes velocity is measured using the laser Doppler technique.

Laser surface velocimeters (LSVs) from Polytec are ideally suited because they can conduct measurements on almost any surface and they are not susceptible to contaminated surfaces. The non-contact measuring technique makes it possible to eliminate any negative influences on accuracy, such as slippage and wear, simultaneously. The product being subjected to the measurement also remains intact.

Another benefit of Polytec systems is the flexible interface concept enabling velocity readings via encoder output, serial interfaces, LAN, Profibus and Profinet.

Practical examples:

Polytec LSVs are used for various velocity measurement tasks in the converting and textile industry:

• dwell time determination in coating and surface treatment systems
• control of cutting devices in cut-to-length processes
• coil synchronization when winding sheet materials

Conveyor and drive belt length measurement

In a specific application, a world leading manufacturer of conveyor and drive belts uses several Polytec LSVs for carrying out length measurements at cutting stations. This means that customer-specific cuts can be automated, simplifying the process significantly. The cut-to-length accuracy using the LSV is independent of the belt surface and achieves a precision of 0.1%

Length measurement on roll-fed material and piece goods

Determining the velocity provides the basis for measuring the length (link to the velocity measurement application). The length is calculated based on the velocity profile while the measured object passes through the measuring location..

A laser surface velocimeter (LSV) independently recognizes whether the material is in the measuring location and can start/stop the length measurement accordingly. To achieve maximum measurement accuracy the LSV offers you the option of connecting light barriers as a means of starting or stopping the length measurement. This means you can link up several light barriers with one another to obtain a variety of application options. This may include, for example, controlling the length measurement using both trigger inputs, thereby increasing accuracy

Laser surface velocimeters (LSVs) from Polytec are ideally suited because they can conduct measurements on almost any surface and they are not susceptible to contaminated surfaces. The non-contact measuring technique makes it possible to eliminate any negative influences on accuracy, such as slippage and wear, simultaneously. The product being subjected to the measurement also remains intact.

Another benefit of Polytec systems is the flexible interface concept – it enables length readings via encoder output, serial interfaces, LAN, Profibus and Profinet.

Practical examples:

Polytec LSVs are used for a variety of length measurement processes in the converting and textile industry:

• winding sheet materials
• cutting-to-length during fabrication
• position sensing in printing processes

Conveyor and drive belt length measurement

In one specific case, a world leading manufacturer of conveyor and drive belts uses several Polytec LSVs for carrying out length measurements at cutting stations. This means that customer-specific cuts can be automated, simplifying the process significantly. The cut-to-length accuracy using the LSV is independent of the belt surface and achieves a precision of 0.1%

Tension control on sheet materials

Processing sheet materials means keeping the sheet tensioned. If the tension is too little, then the product "sags" and may become entangled. If it is too much, then the product can become overstretched and end up becoming damaged or ripped as a result. In order to accurately determine this tension between two different points in the process, it is essential to measure the velocity at both points. You can then calculate the tension from the difference.

Laser surface velocimeters (LSVs) from Polytec are ideally suited because they can conduct measurements on almost any surface and they are not susceptible to contaminated surfaces. The non-contact measuring technique makes it possible to eliminate any negative influences on accuracy, such as slippage and wear, in one go. The product being subjected to the measurement also remains intact.

The increased precision in velocity measurement enables you to monitor the tension more closely, thereby optimizing the process while preventing the product from being damaged by tension fluctuations. The result: You increase quality while at the same time reducing waste.

Practical examples:

Polytec LSVs are used in various applications in the converting and textile industry as a means of regulating tension:

• in joining sheet materials, i.e while changing rolls of film and packaging materials
• when processing sensitive material such as thin films