Non-contact measurement is more precise and more reliable

Elongation process control with laser precision

For processing steps which involve elongating (extending) products, it is important to measure and monitor the degree of elongation – since this has a substantial influence on product quality and further processing. If the degree of elongation is too low, requirements for subsequent processing steps may not be met. If, on the other hand, the degree of elongationis too high, this can have a negative impact on product characteristics or, in the worst case, the product may be damaged. In order to determine the elongation, the velocity is measured both before and after the processing step and the degree of elongation is calculated based on the results of the velocity measurements.

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 accuracy of the velocity measurement allows you to monitor velocity difference and elongation 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.

Skin-pass and stretch degree measurement

Polytec LSVs are used in the metal industry for measuring the skin-pass degree in skin-pass or stretching mills. The skin-pass degree in cold strip skin-pass rolling is determined by the difference in strip velocity at the input and output of the roll stand, which in the past has been measured mechanically using tachometer generators. Using two Polytec LSVs prevents the occurrence of measuring errors owing to slippage and wear and the skin-pass degree measured may be used as a control parameter for adjusting the rolls. Using an LSV a major German stainless steel manufacturer confirmed an uncertainty of just ± 0.02 % of his skin-pass degree measurement.

Speed synchronization in aluminum production

In the largest aluminum smelting and rolling plant in the world, the length and velocity of aluminum sheets in the manufacturing process are measured simultaneously using non-contact laser Doppler measurement technology from Polytec. Several Polytec LSVs are integrated in the manufacturing process and provide readings for plant control.

Velocity difference measured with laser precision

In processes which involve the elongation of products any desired velocity difference should be appropriately regulated . 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 (LSVs) allows you to accurately determine the velocity at the relevant points in the process, thereby enabling you to optimize it. ProSpeed 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.

As the measurement is free of slippage you can control the process to ensure high reliability, even during start-up processes and right up until deceleration, thereby increasing product output. The increased accuracy of velocity measurement allows you to monitor the velocity differencemore 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.

Speed measurement in c frames of rolling mills

The metal processing industry has high standards when it comes to the dimensional accuracy and quality of steel and aluminum products. Modern rolling mills are now frequently controlled using the mass flow principle to further reduce the thickness tolerances of rolled strips. Laser surface velocimeters (LSVs) are easy to integrate and enable reliable measurement of the velocity component.

Synchronizing speed in aluminum fabrication

In the largest aluminum smelting and rolling plant in the world, the length and velocity of aluminum sheets in the manufacturing process are measured simultaneously using non-contact laser Doppler measurement technology from Polytec. Several Polytec LSVs are integrated in the manufacturing process and provide readings for plant control.

Polytec LSVs are used for a variety of velocity difference measurements in the metal industry:

• in reversing and tandem mills for mass flow regulation in cold-rolling mills,
• skin-pass and stretch degree calculation in skin-pass and/or stretching mills,
• with a high temporal resolution for roll gap control in tailored blank flex rolling mills
• synchronization for welding control

Roll-fed material and piece goods velocity measurement

Velocity measurement is indispensable for process control and optimization in many industrial processes. It is the basis for countless 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 also remains intact.

Another plus point of Polytec systems is the flexible interface concept which enables velocity readings via encoder output, serial interfaces, LAN, Profibus and Profinet.

C-micrometer in rolling mill with integrated velocity measurement

The downstream manufacturing industry also has high standards when it comes to the dimensional accuracy and quality of steel and aluminum products used. With a view to continually reducing the thickness tolerances of rolled strips, modern rolling mills are regulated using the mass flow principle. Laser surface velocimeters (LSVs) are easy to integrate and enable reliable measurement of speed components.

Synchronize speed in aluminum production

In the largest aluminum smelting and rolling plant in the world, the length and velocity of aluminum sheets in the manufacturing process are measured simultaneously using non-contact laser Doppler measurement technology from Polytec. Several Polytec LSVs are integrated in the manufacturing process and provide the necessary readings for plant control.

Rotary motion control

Two Polytec LSVs are used in a stainless steel rolling mill to regulate a planetary cross-rolling mill. The simultaneous measurement of rotational and translational velocity at the outfeed of the rolling mill allows any hot steel rod rotation to be offset automatically.

Rotary tube saw control

This is increasingly being used in tube rolling mills. The saw blade is moved around a circular course at the speed of the tube. The movements must be exactly synchronized, with speeds of up to 10 m/s. The Polytec LSV measures tube speed without slippage or wear as a means of controlling the rotary tube saw. As well as an exact vertical cut, using the LSV also makes it possible to achieve the smallest length tolerances.

Measure speed in production processes

Polytec LSVs are laser precision sensors which are used for a variety of velocity measurement processes in the steel, metal and aluminum industry:

• holding time determination in coating and surface treatment systems
• cutting device control/synchronization in cutting-to-length applications
• drive and belt tension synchronization in roll stands
• cooling process monitoring, e.g. in laminar cooling mills
• skin-pass degree determination in skin-pass or stretching mills
• mass flow regulation in reversing and tandem mills.

Improve the mass flow control

Mass flow control is essential for processing metals. Controlling and improving mass flow means that the width of the roll gap is controlled so that the material thickness of the end product remains as constant as possible. If the thickness before the roll stand and the velocity before and after the roll stand are known, the roll gap, which determines the thickness of the rolled product, can be adjusted in accordance with the desired conditions.

The strip thickness is measured using C-frames with an integrated, compact LSV Laser Surface Velocimeter, measuring the velocities upstream and downstream of the roll stand. Because the speed measurement is extremely accurate, you can monitor and control the roll gap more precisely using the LSV and thereby obtain better compliance with the thickness specification of the end product. The result is increased quality and, consequently, increased product output.

Laser speed sensors from Polytec measure on almost any surface, even on contaminated surfaces. The non-contact measuring technique eliminates slippage, wear and provide laser precise, reliable production control without influencing the product surface.

Skin-pass and stretch degree measurement

The skin-pass degree in cold strip skin-pass rolling is determined by the difference in strip velocity at the input and output of the roll stand, which in the past has been measured mechanically using tachometer generators. Using two Polytec LSVs prevents the occurrence of measuring errors owing to slippage and wear and the skin-pass degree measured may be used as a control parameter for adjusting the rolls. Using an LSV a major German stainless steel manufacturer confirmed an uncertainty of just ± 0.02 % of his skin-pass degree measurement.

C-Frame in rolling mill with integrated speed measurement

The metal processing industry has high standards when it comes to the dimensional accuracy and quality of steel and aluminum products. Modern rolling mills are now frequently controlled using the mass flow principle to further reduce the thickness tolerances of rolled strips. Laser surface velocimeters (LSVs) are easy to integrate and enable reliable measurement of the velocity component.

Speed synchronization in aluminum production

In the largest aluminum smelting and rolling plant in the world, the length and velocity of aluminum sheets in the manufacturing process are measured simultaneously using non-contact laser Doppler measurement technology from Polytec. Several of such optical speed encoders are integrated in the manufacturing process and provide readings for plant control.

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Automation of non-destructive materials testing

A number of methods are used to detect defective material quickly and reliably, ultrasound or x-ray, for example. On the one hand the aims are preventing defective products from being put on the market, and on the other hand guaranteeing the functionality of the products in use.

If a defect is detected, it is mandatory to identify the position of the defect on the examined object. You can ascertain this by measuring the velocity and length using a laser surface velocimeter (LSV). This in turn enables the automation of non-destructive materials testing, saving you time and money.

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 measurement 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.

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A practical example:

Non-destructive testing of steel tubes

Two Polytec LSV-1000 velocimeters are integrated in a test system. The first of these provides a millimeter clock to determine the length of test pieces and to log the flaw location, which is then color-marked. The second LSV is required to register speed variations in the test pieces.

Cut length control on roll-fed material

Determining the length and velocity provides the basis for controlling the cutting length. 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 (LSV) 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 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 alsoremains intact .

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

Practical examples:

• Control of torch cutters in continuous casting
• shear control in metal service centers
• control of flying shears in bar mills
• cut length control in section rolling mills
• saw control in tube rolling mills

Rotary tube saw control

These are increasingly being used in tube rolling mills. The saw blade is moved around a circular course at the speed of the tube. The movements must be exactly synchronized and that with speeds of up to 10 m/s. The Polytec LSV measures tube speed without slippage or wear to control the rotary tube saw. Using the LSV allows for an exactly vertical cut and reduces the length tolerances to a minimum.

Optical speed measurement in continuous casting processes

High-precision non-contact measurement systems are the benchmark when it comes to keeping material loss to a minimum in the continuous casting of steel, copper alloys or aluminum. In addition to the length measurement, measuring the velocity is also extremely important when cutting the strand in order to guarantee a clean, straight cutting edge. The precise measurement of the velocity and length of the strand is therefore essential to process and cost optimization.

Optical speed control in continuous casting: non-contact and wear-free

That is why the ProSpeed LSV from Polytec is the sensor of choice. This optical measuring system has been specially developed for precision measurement in harsh conditions. It is wear and maintenance-free even in permanent operation. In addition measurement data can be easily integrated into the process control system.

The ProSpeed LSV uses the differential laser Doppler technique and measures the laser light scattered back from a moving object. Your benefit in comparison with standard non-contact methods is that the LSV measures from standstill and reliably detects the direction of movement.

ProSpeed as cost-efficient sensor solution

The high repeatability offered by non-contact measurement improves the quality of production and increases the output. Your original investment will pay off quickly: If the safety factor is reduced by just a few millimeters when cutting to length, your original investment costs will be recouped within roughly a year. Another advantage: Despite the hot environment no additional efforts are required to cool the measuring system. The protective aluminum housing with embedded stainless steel cooling water pipes is designed for ambient temperatures of up to 200 °C and has a very high cooling capacity.

In brief: Robust, high-precision, non-contact laser surface velocimeters like the latest ProSpeed optical sensor generation from Polytec can help you to significantly increase the efficiency and process reliability in any continuous casting process.

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