Non-contact measurement of velocity and length in paper, cardboard and packaging production

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 cutting length control, length measurement, velocity difference. 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 remains intact too.

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

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Practical examples:

Polytec LSVs are used for various velocity measurement tasks in the paper, cardboard and packaging industry:

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

Non-contact LSV velocity sensors in paper production

A Polytec LSV was installed in a paper factory because of frequent downtime when changing rolls of paper in its coating machine. Integrating the LSV into the process control allowed rolling velocities to be aligned exactly with one another with an accuracy of 0.1 %. This resulted in a significant reduction of tension fluctuations when joining the paper webs and has already led to savings equivalent to the investment costs in under a year.

Cut-to-length and velocity control of non-metallic products

Polytec LSVs carry out measurements on materials such as wood, cardboard, film, wire, plastic profiles, construction materials and textiles. One specific example is the length measurement of corrugated board sections.

High-precision detection of velocity differences

In processes which involve the elongation of products, any desired velocity difference should be regulated accordingly. In other processes differences are undesirable since they can lead to backlogging or may even damage the product – due, for example, to the slippage of drive rollers or because tension is generated in the product. The velocity difference is calculated by measuring the velocity at different points in the process and comparing the readings with one another.

Using several laser surface velocimeters (LSV) allows you to accurately determine the velocity at the relevant points in the process, thereby enabling you to optimize it.

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 remains intact too.

The increased accuracy of velocity measurement allows you to monitor the velocity difference more closely. As a result you are better able to adhere to the end product requirements. The result: You increase quality while at the same time reducing waste.

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Polytec laser sensors for paper production

Polytec LSVs are used for various velocity difference measurement tasks in the paper, cardboard and packaging industry:

• synchronization of individual sheets in longitudinal cutting processes
• synchronization of roll and sheet in winding and unwinding processes
• tension monitoring 

A Polytec LSV was installed in a paper factory because of frequent downtime when changing rolls of paper in its coating machine. Integrating one of the LSV into the process control equipment allows allowed rolling velocities to be aligned exactly with one another with an accuracy of up to 0.1 %. This results resulted in a significant reduction in of tension fluctuations when joining the paper webs and has already led to savings equivalent to the investment costs in under a year.

Cut length control on roll-fed material

Determining the length and velocity provides the basis for controlling the cutting length (link to velocity measurement and length measurement applications). If the sheet materials are not to be stopped in order to perform the cut, then the cutting device must move along with the sheet material for a straight cut, in other words it should be a "flying cutting device". The speed of the sheet material is measured for velocity synchronization

Laser surface velocimeters (LSVs) from Polytec are ideally suited for cut length control because they measure both velocity and length at the same time and can display the values on different interfaces. The LSVs work on almost any surface and 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 remains intact too.

The Polytec LSV offers increased cutting precision compared to other methods and therefore allows reduced safety margins to be added to the preset cut length. This will save costs on every cut.

Another benefit of Polytec systems is the flexible interface concept – it enables length and velocity readings via encoder output, serial interfaces, LAN, Profibus and Profinet. The digital outputs feature a pre-warning signal that indicates when the cutting length is about to be reached, as well as the cut signal for triggering the cutting process.

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Practical examples:

Polytec LSVs are used in various applications in the paper, cardboard, & packaging industry as a means of controlling cut lengths of paper and cardboard products.

Cut-to-length and velocity control of non-metallic products

Polytec LSVs carry out measurements on materials such as wood, cardboard, film, wire, plastic profiles, construction materials and textiles. One specific example is the length measurement of corrugated board sections.

Position tracking on sheet materials and piece goods

Position tracking plays an important role in the paper industry if a certain position on the object being measured is essential to the process.

Length measurement can trigger a working step at regular intervals in the process, e.g. printing labels or attaching lettering and logos.

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 remains intact too.

The increased accuracy of velocity and length measurement allows you to determine positions with more precision. As a result better adhesion to the end product requirements is achievable. The result: You increase quality while at the same time reducing waste.

Practical examples:

Polytec LSVs are used in the paper, cardboard and packaging industry for determining positions in printing processes.

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, simultaneously. The product being subjected to the measurement remains intact too.

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

Documents

Practical examples:

Polytec LSVs are used in various applications in the paper, cardboard, & packaging industry as a means of regulating tension:

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

Non-contact LSV velocity sensors in paper production

A Polytec LSV was installed in a paper factory because of frequent downtime when changing rolls of paper in its coating machine. Integrating the LSV into the process control allowed rolling velocities to be aligned exactly with one another with an accuracy of 0.1 %. This resulted in a significant reduction of tension fluctuations when joining the paper webs and has already led to savings equivalent to the investment costs in under a year