Combined crack and grinding burn test with single sensor and array sensor on bearing rings and rolling elements

Non-contact, fast, high-resolution and efficient

In addition to a wide variety of tasks from industry, a current topic is crack and grinding burn testing on bearing rings and rolling elements. This customer requirement can be solved semi-automatically and also fully automatically. Depending on the test task, single probes or array probes can be used.

In the example shown, the inspection of rolling element components requires the detection of minute cracks and grinding burn. In order to meet the required cycle time in automated testing systems, array sensor technology is increasingly being used in these applications.

In the present case, an 8-fold sensor array is used for testing on the inner and outer ring. Six sensors are arranged in two staggered rows for testing the tread. For testing the side surfaces (rims), one sensor each is angled at 90°. The sensor array is controlled accordingly by the ELOTEST PL650 and the sensor elements required for the respective test are selected.

8-fold sensor array KDA-129 with six sensor elements arranged in two rows for testing the running surface of rolling bearing rings and two sensor elements arranged at 90° to each other for testing the thrust ribs.

Each sensor is a combined differential / absolute sensor. The absolute winding can be used both for electronic liftoff / distance compensation and (simultaneously) for additional testing for planar grinding burn.

The sensor array is connected to a test channel of the ELOTEST PL650 via a fast 8-fold multiplexer.

The ELOTEST PL650 is a digital eddy current tester and is ideally suited for all types of eddy current testing such as crack, heat treatment, (opens in new tab)material mix-up and grinding burn testing.

It has a connector for active sensor arrays with up to 64 sensors per channel. The high multiplex rate allows very high test speeds and thus significantly reduces the cycle time of the test and increases the throughput of the test system.

The ELOTEST PL650 with its array sensor technology is therefore ideally suited to implement fast and efficient crack and grinding burn testing in automated systems.

Source: Rohmann GmbH, internal application report.

Abbildung 8-fach Sensorarray KDA-129

8-fach Sensorarray KDA-129 mit sechs in zwei Reihen angeordneten Sensorelementen zur Laufflächenprüfung an Wälzlagerringen und je zwei 90° hierzu angeordneten Sensorelementen zur Prüfung der Anlaufborde.

Abbildung C-Scan-Darstellung einer Lauffläche

C-Scan-Darstellung einer Lauffläche mit zwei 1 mm Laserpunkten zur Simulation von Schleifbrand, gescannt mit den stirnseitigen Sensoren des Arrays. Darstellung und Verarbeitung im ScanAlyzer.

The EMDC technology – exact inspection results for all parts

With our EMDC technology (Electro Mechanical Distance Control), for which an international patent has been filed, you can easily solve even difficult testing tasks. In the case of out-of-round parts, complex geometries, parts that are difficult to center, or fundamental runout problems, the distance between the sensor and the test piece is controlled electromechanically. That’s why our electromechanical distance control offers you consistently high test sensitivity and near-perfect compensation, even with large distance changes. The combination with the ELOTEST PL650 makes it a testing system with highest flexibility.

The Eddy+ test method – Heavy Plate Hard Spot Testing according to ROHMANN

In steel production, local hardening can sometimes occur on the surfaces of semi-finished products. Curing causes disturbances during further processing and can even lead to component failure. Here, the Eddy+ method we developed provides reliable non-destructive testing for surface hardening. This method identifies hardness differences quickly and easily. For this purpose, hardware and software specially developed for this application and a special sensor perform a partial remagnetization with a two-pole magnetization pulse. At the same time, the actual eddy current sensor measures the associated permeability change. The great advantage of our method is the cancellation of interfering influences (for example by a rolling skin in a conventional eddy current test) at the same time as high test speeds of up to 1m/s. An international patent has also been filed for this new test method.

Path-dependent filters – reliability at any test speed

Varying speeds and fixed filter settings during testing often lead to problems in defect detection. The use of our path-dependent filters, such as in ROHMANN’s ELOTEST PL650, provides reliable test results even up to standstill and ensures speed-independent testing with constant signal quality. No retesting of the material is required after a shutdown. The test can be continued directly after a standstill.

Abbildung C-Scan-Darstellung einer Lauffläche

Electronics is the heart of our test systems

In daily use, the electronics of eddy current test systems in the measurement chain between sensor and signal evaluation must meet the highest requirements for precision, dynamics and load capacity. ROHMANN manufactures sophisticated electronic functional groups from state-of-the-art components. These are built under high requirements with powerful CAD systems, then tested according to strict in-house regulations and fully documented. The digital technology used facilitates the complete simulation of electronic assemblies. It also enables integrated function control, automated alignment and computer-aided calibration of our products.

Software is the life of our test systems

Today, modern electronic systems are programmable at all levels by software. Their programmability makes our electronic systems exceptionally powerful and flexible. ROHMANN has a highly qualified staff of experienced specialists for programming. Programming systems and development tools, from assembler to complex high-level language, from CAD-supported development systems for electronics and mechanics to tools for graphics-oriented programming of application-specific solutions – ROHMANN software makes our test equipment more powerful, smaller, less expensive and simplifies the implementation of customer-specific solutions.

Mechanics is the moving apparatus of our test systems.

We realize all levels of mechanical systems – from simple mechanical guiding aids to automatic testing mechanisms and robotic handling. We always manufacture sensor technology and mechanics in CNC precision for reasons of highest accuracy and constant quality. To ensure these high standards, ROHMANN regularly performs mechanical and electronic calibrations according to national and international standards. A separate, internal calibration system was introduced for this purpose.

Sensor technology is the vision of our inspection systems.

Sensor technology detects the eddy current signals in the test material and for this reason is the first important link in an entire measurement chain. This is because only what the sensor system records can later be processed in the measurement chain. A high level of sensor vision is therefore irreplaceable. All ROHMANN sensors are optimized for the detection of physical effects, the detection of defects. At the same time, however, they also meet all testing requirements in terms of material, geometry and complexity of the test part structure. ROHMANN has developed pioneering sensors for this purpose, which have now become the standard worldwide.