Using Surface Defect Detection Systems for Steel Processing

By AZoNano

Table of Contents

Introduction
Overview of the Surface Defect Detecting System MSC9000
Image Processing Function
Conclusion
About ULVAC Technologies

Introduction

Development commenced only to respond to the demands from coil centers, which are users of the control systems from ULVAC. It is possible to control length and position accuracies to a certain degree if control systems are kept in good condition and machines are maintained well. Even if the accuracy after processing is poor, it is considerably easy to detect abnormalities by observing the appearance of processed products.

It is not easy to detect abnormalities on product surfaces. After processing, it becomes difficult to check material surfaces since products are piled in shear and other lines. Also in slitter lines, slit products are coiled again, making it difficult to detect abnormalities on product surfaces.

Coil centers had to take special measures for products to be supplied to users who have strict surface quality requirements. One such measure is to assign dedicated inspectors for checking unevenness, scratches, rust and other defects on coil surfaces. Checking rust is shown in Figure 1. Another is to reduce the line operation speed to 1/4 of the normal speed to enable visual inspection of surface quality.

Figure 1. Rust

The MSC (Material Surface Checker) 9000 was developed to operate with the company’s other specialties, "line drive applications" and "servo applications" to expand control capabilities.

Overview of the Surface Defect Detecting System MSC9000

The MSC9000 is a surface defect detection system composed of defect inspection cameras, lighting equipment, and their control system. It is known as a surface defect detection system, not a surface inspection system since the latter collects large amounts of surface inspection data, part of which cannot be analyzed.

Top priority is given to simple operation by carefully selecting functions and improving defect detection accuracy. A new concept has been developed with the MSC9000, which is specializing in detecting defects rather than merely checking the surface. This means that its design is more of an intermediary system between a surface inspection system and sensor system. Automatic tuning and various other functions have been developed and adopted to minimize complex configuration settings, which are troublesome for line operators.

Certain key functions are detailed below:

  • Automatic Start Function - This function automatically determines along with the movement of the objects for inspection, when to start and stop inspections.
  • Illuminance automatic tuning function – This function automatically sets the illuminance of the lighting equipment according to the surface treatment of the material to be inspected. To create a stable surface inspection environment, the illuminance is controlled to keep an appropriate level of brightness that can slightly change depending on the objects for inspection.
  • Automatic mask setting function – This function detects automatically the area to be targeted for inspection based on the processed images of the inspection objects, setting the mask area automatically. This function detects slit positions precisely and set masks automatically (patent pending 2011-209503).
  • Maintenance function - This monitor function is used to promptly conduct maintenance of the cameras and lighting equipment. The system has a monitor to check the installation conditions of the cameras and lighting equipment and convert the results to numerical values in order to enable early detection of failures that may be caused by removing and reassembling the system components. This monitor is also used to reduce the time required for installation and adjustment of the system (patent pending 2011-213163).

Image Processing Function

The MSC9000 is a system that processes image data sent from the cameras at high speed and reassigns the data in the database. The core of the MSC9000 is the integrated software that controls the defect detecting cameras and the lighting equipment. This system uses line sensor cameras instead of the area sensor cameras generally used for defect inspections. The line sensor cameras used for defect detection are the company’s own original products based on "ALI-6000" intelligent camera made by AVAL DATA as shown in Figure 2.

Figure 2. Line sensor cameras

The system uses linear high-intensity LED lighting equipment. It plays a key role in creating an environment for surface defect inspection as shown in Figure 3.

Figure 3. Lighting equipment

LEDs were adopted since they have a long service life and stably provide a large quantity of light, which are essential characteristics for maintaining good inspection environments.

The cameras and lighting equipment are positioned so that the light emitted from the lighting equipment reflects off of a material under test and enters a camera as shown in Figure 4.

Figure 4. Positions of camera and lighting equipment

Based on test results the company believes that this method of taking photos is most effective for recognizing the uneven-ness of material surfaces being inspected. The MSC9000 basic installation frame is used to optimize the relative positions of the cameras and the lighting equipment as shown in Figure 5. When using the MSC9000, users must also install the MSC9000 basic installation frame on the inspection surface.

Figure 5. MSC9000 basic installation frame

Figure 6. Connection between MSC9000 and PSC7000

Field tests were conducted on this system by installing it in a slitter line. The test results indicate that the system produced good results when it was installed between a belt bridle and a pinch roll before winding materials. However, depending on line operating conditions, there is a possibility that slippage between the bridle belt and the material cannot be kept constant due to changes in friction and slight vibration may occur. In this case it is necessary to install a vibration damper roll.

In shear lines, the system produces good results when it is installed before a pinch roll before shearing. This is because the pinch roll basically serves as a vibration damper. Nevertheless, it may be necessary to install a vibration damper roll depending on the line configuration.

Advantages of incorporating this system in lines are the increased inspection speed, the reduced burden on dedicated inspectors and reduction in the additional operational burden of line operators. In addition, this system allows users to keep inspection records (for example, by saving records in the database and printing inspection results after completion of inspection). These records can be utilized to prevent complaints from occurring, and also to quickly locate the cause of a defect to facilitate processing of affected products. With these advantages, this system is expected to increase the surface defect inspection efficiency without annoying operators with troublesome operation after the system is incorporated into lines.

Conclusion

The image processing technology used for this system is still under development. It is important to keep up with increasing photography speeds and faster image processing. After incorporating the system into lines, users can utilize inspection results in many different ways. We need to turn our attention to these different ways of utilizing inspection results.

About ULVAC Technologies

Founded in Japan in 1952, ULVAC is an international corporation that designs, manufacturers and markets equipment and materials for industrial applications of vacuum technology. Today, ULVAC is a leading global supplier of production systems, instrumentation, pumps and vacuum components used in the semiconductor, flat panel display, disk/magnetic media, and industrial manufacturing markets.

The corporation is comprised of some 36 individual companies engaged in all sectors of the vacuum industry. The ULVAC name is derived from the company's conceptual foundation - "The ULtimate in VACuum Technology".

This information has been sourced, reviewed and adapted from materials provided by ULVAC Technologies.

For more information on this source, please visit ULVAC Technologies.

Date Added: Jun 14, 2013 | Updated: Jun 14, 2013
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