New possibilities for highly dynamic thickness control
The new “VTLG” laser strip thickness measuring system is compact and robust, and thanks to its design features is the only laser strip thickness measuring device that measures the strip thickness in the mill during rolling. With this new system, the Friedrich Vollmer Feinmessgerätebau GmbH is giving new impetus to highly dynamic strip thickness measurement.
The new strip thickness gauge combines the benefits of many thickness measuring systems – but without their disadvantages: VTLG measures irrespective of the alloy and as precisely as contact gauges, but at the same time contact-free like X-ray and isotope gauges.
It is the only optical thickness gauge that is so compact and robust that it can be installed in the mill in the immediate vicinity of the roll gap. It thus opens up completely new possibilities for quick and precise thickness control and for quality assurance. With an internal scanning rate of 50 kHz, the scalable analog output provides the input signal for the high-speed thickness control within milliseconds.
VTLG measures the absolute thickness of the strip – just like the contact gauges for which Vollmer has been renowned worldwide for decades – but contact-free and from a safe distance. With a measuring accuracy of +/- 1 μm per millimetre strip thickness, it achieves the same precision as the tactile and X-ray gauges.
It offers different measuring ranges from 0.015 to 12.0 mm thickness. Thanks to its compact design and robust construction, it is suitable for installation in the mill. With an air gap of the C-frame of 125 or 285 mm, the sensors are positioned at a safe distance from the strip. The measuring depth lies between 400 and 1200 mm, depending on the gauge type.
But Vollmer has developed the VTLG not only for measurement in the mill – it is equally suitable for use on production lines, such as on the annealing line, in the finishing shop, on strip millers or in shear lines.
Four design features contribute to the high precision of the systems: The temperature stabilisation of the measuring frame, the automatic check of the calibration before each strip, the air cleaning systems and the synchronicity of the measured value recording.
1. Vollmer compensates the thermal expansion of the C-frame by means of an intelligent temperature management system. This ensures that the measurement of the strip thickness in the mill, at the exit from a furnace line or on the annealing line is just as accurate as in an air conditioned laboratory.
2. Furthermore, the system checks the adjustment of the gauge using a calibration normal integrated into the C frame before each strip pass: At the start of the measurement, the C-frame moves automatically into the line and on its way there measures the thickness of four captive certified gauge blocks representing the thickness spectrum of the respective mill. The VTLG thus constantly monitors itself and makes any necessary corrections automatically.
3. The fact that the two sensors operate absolutely synchronously contributes significantly to the high precision of the systems. VTLG eliminates the influence of the strip movement during the measurement.
4. Air cleaning systems ensure reliable operation even under the rough environmental conditions in the mill: Both the entry and exit windows of the transmitting and receiving lenses and the beam path are constantly flushed with clean air so that vapours or mists from the mill do not affect the measurement.
The lasers conform to laser protection class 3B. This means that no additional measures are necessary for protection of the personnel.
VTLG is designed so that it can be installed in most production lines and mills without modification. The resulting series production enables Vollmer to offer the system at an attractive price.
The system has all the common interfaces for communication with the line controller: PROFINET, PROFIBUS, hardware interface or TCP/IP. Operation via a touch panel is simple and intuitive, extensive diagnostic functions support the operator.
Vollmer at Metec 2015
(June 16 to 21, 2015, Düsseldorf):
Hall 04, Stand D 18
About Friedrich Vollmer Feinmessgeräte GmbH
The development in 1963 of the world\’s first strip thickness gauge that was able to measure the thickness of strips with an accuracy of a few µm during rolling in the cold stand marked the start of the company history. Vollmer was also one of the first companies to enable shape measurement on the passing strip.
Over the course of the years, Vollmer has developed various contact gauges as well as isotope and X-ray systems for thickness measurement on strip, shape measuring systems and roll measuring gauges. Today more than 1,000 strip thickness gauges and over 100 shape measuring systems are installed in mills worldwide. Vollmer has also equipped more than 100 roll grinding machines with roll measuring gauges. The modernisation of mills, including the changeover to hydraulic screwdowns and the installation of systems for thickness control (AGC) and flatness control (AFC) of strip round out the Vollmer portfolio.
Vollmer has roughly 100 employees at its headquarters in Hagen. Partners and subsidiaries in more than 30 countries are available to support the customer and provide quick on-the-spot service.
Friedrich Vollmer Feinmessgeraetebau GmbH
Dipl.-Ing. Elke Vollmer
Verbandsstraße 60 b
58093 Hagen / Germany