Inline metal thickness profile and speed measurement systems

Chris Jones, Managing Director at Micro-Epsilon UK comments: "Due to ever-increasing manufacturing tolerances in metal strip production, the need to find higher accuracy, inline measurement solutions is accelerating. In addition, traditional radioactive measurement systems are now being phased out in most processes due to rising costs of ownership - due to stringent health and safety practices, as well as challenges in terms of handling, servicing, maintenance and recalibration. Therefore, "safe' non-contact measurement solutions are being rapidly adopted by the metal processing industry."

Over the past 12 years, Micro-Epsilon's Systems Group has developed a range of innovative, robust, complete turnkey measurement systems that offer distinct technical advantages in terms of measurement accuracy, thermal stability and reliability. This is backed up by installation, servicing, maintenance, technical support with guaranteed response times, retrofitting and upgrade services.

These distinct technical advantages include fully automatic calibration. The system periodically re-masters against a known reference, which is incorporated into the system. This process is fully automatic and requires no user interaction. The system also has integrated measurement sensors in the framework and mechanical parts, which constantly measure the thermal expansion of the system. The software then compensates accordingly, ensuring total system accuracy irrespective of temperature variation.

Solid-state memory

Jones continues: "We manufacture the sensor technology and all other critical parts including the electronics and software. The system mechanical design is also developed and assembled in-house, as this is critical to mechanical stability. All electrical hardware, including the PCs, is industrial-grade with solid-state memory. All these factors enable Micro-Epsilon to guarantee total system accuracy, reliability and to take full ownership of the complete system.

"As well as offering our comprehensive range of inline, non-contact thickness and speed measurement systems for metals, we are providing a dedicated service to UK-based customers, including a 24/7 technical support hotline and a guaranteed on-site, rapid response service. We understand how critical it is for these companies to minimise production downtime and improve their product quality and so our engineers will be on call to assist the customer at all times. We can also provide customers with dial-in communications and remote diagnostics for measurement systems, which speed up our response times and enables our engineers to quickly rectify any issues that arise onsite."

Micro-Epsilon's range of measurement systems for metals comprises the following:

Thickness measurement of metal strip

Part of Micro-Epsilon's thicknessCONTROL MTS 8202 family, C-frame systems measure the thickness profile of flexible metal strip. C-frame systems are modular in their design, offering flexibility and high performance. These systems can be installed in hot and cold steel rolling mills, as well as slitting, coating, casting and cutting lines, providing reliable, high precision measurement results that creates a basis for controlling the production process and product quality.

C-frame systems measure differentially. An application-specific (confocal, capacitive or laser triangulation) displacement sensor is integrated in the upper and lower arms of the C-frame. The thickness of the target material is derived from the distance between the two sensors and the resulting signals. By combining highly efficient signal processing algorithms and visualisation software, the system is able to achieve accuracies in the single micrometre range - typically 1 to 5 microns.

The C-frame can be used as a traversing thickness measurement system on linear axes in order to ensure full width measurements of the target. The control and analysis software is developed in-house by Micro-Epsilon specifically to match the needs of the metal processing industry, providing all the required functions in order to continuously record and evaluate production quality. This includes graphical user interfaces and the ability to store multiple product libraries. Also, the software supports and displays Statistical Process Control (SPC) parameters and other "Process Capability' analysis and reporting methods such as Six Sigma PK and PM. Various fieldbus interfaces are available, which enable integration to the customer's production control systems.

Fully automatic calibration ensures that measurements are not affected by temperature, enabling the system to be installed as a fixed, inline measurement system in harsh industrial environments, without the need for calibration or manual adjustments. All sensor technologies used are non-contact, wear-free and do not use isotopes or X-rays. The C-frame system provides long-term measurement reliability at an affordable price. C-frame systems are able to measure strip widths up to 1m and strip thickness from

Thickness profile measurement of large strip widths

Micro-Epsilon's O-frame systems are suitable for larger strip widths up to 4000mm.

O-frame systems measure differentially and incorporate many of the same features, functionality and software as C-frame systems, but also incorporates the desired measurement sensors (laser, optical, capacitive, etc.) mounted to a mechanical linear guidance system that measures the complete thickness profile of the metal strip by traversing across the whole strip (or the thickness profile of each ring in a slitting line).

Non-contact length and speed measurement

In rolling, cutting, coating and stretch lines, measuring the length and speed of the metal strip is critical. Micro-Epsilon's ASCOspeed 5500 is a powerful speed measurement system specifically developed for this task.

The system operates on the signal phase group measuring principle and is a further development of the proven spatial frequency filter technology. This enables the system to measure the surface of moving metal strip during the production process. It does this by using the precise grid structure of a detector, which is then converted into an electrical frequency, which in turn is proportional to the speed of the material or object.

Protected by a robust, aluminium housing, ASCOspeed 5500 combines a sensor and controller in a single enclosure. Real-time signal processing ensure that each change in material speed is measured precisely. Fast hardware is able to register, verify and compress current speed values in microseconds, for material speeds up to 3000m/min. The sensor also provides a reliable speed signal that minimises signal averaging and output times of 0.5 milliseconds.

ASCOspeed 5500 is designed to easily replace more conventional mechanical systems. The system is freely scaleable with quadrature pulse output channels and so can be used as an alternative to rotary shaft encoders. Synchronous operation provides significant benefits when measuring differential speeds, for example, in mass flow control or skin pass level control. Using trigger pulses from the system controller, several hardware-controlled measuring process devices can operate synchronously, providing the customer with more precise measurement results in acceleration phases.

Automatic inspection systems for welding

Systems are also available for the measurement and inspection of welds and weld seams, such as in the production of pipelines or girders. These systems utilise laser triangulation scanners to measure the weld profile of both semi-finished products that are about to be welded (e.g. pipe ends) and already welded materials. These systems can be integrated to welding robots, enabling improved control of the complete welding process, resulting in faster, more energy efficient welding, as well as improved quality of the final product.

Sensors for metals

As well as providing complete inline measurement and inspection systems, Micro-Epsilon also offers a range of sensors for measuring metals. These include sensors that measure the flatness of rolled steel or aluminium sheet; diameter measurement of coils in rolling mills; the measurement of strip width when trimming metal strips; inspection of pipe weld seams; exact strip speed measurement for metal cutting lines; and sensors for measuring the stretch coefficient in the production of metal strips and foils.

For more information on Micro-Epsilon's range of measurement systems for metals, please email [email protected], or visit the website at www.micro-epsilon.co.uk.