Inspection methods

Automatic sorting machines from KROB SCANNERS s.r.o. employ several methods for the checking of the surface and sub-surface of steel bearing balls. For this purpose, for each method, special probe-testers have been developed. The most important methods are:

• EOT – Electro-Optical Tester
• EOTW – Electro-Optical Tester Wet*
• ECT – Eddy-Current Tester
• ECTW – Eddy-Current Tester Wet*
• EVT – Electronic Vibration Tester
• EVTW – Electronic Vibration Tester Wet*

*Used only on Ball Scanners Wet.

The EOT tester illuminates the surface of the ball using a laser beam and then senses the intensity of reflected light. After comparing the expected (calibrated) and real value of the intensity of reflected light the machine evaluates the quality of the measured ball using optical method and sorts the ball using operator set sensitivity either through the OK or EOT outlet. There is a special EOT probe for wet and dry machines (EOT / EOTW) which differ in shape and design.

EOT and EOTW testers are used on all automatic sorting Ball Scanner machines to evaluate the surface of the balls using two methods:

• EOT1 – for the detection of point defects (absolute or relative)
• EEOT2 – integrated method (measurement of shine and polish)

EOT/EOTW is an encapsulated laser device operating in the visible wavelenght range of 660±20 nm and luminosity up to 1 mW. It is therefore Class 1. laser device.

The ECT Tester exploits the ferromagnetic properties of the material of which the tested balls are made. Using the Eddy-Current method it can detect surface and sub-surface defects all the way to a predefined depth of material depending on the setting of the excitation frequency.

Each ECT tester checks the ball using two independent systems – ECT1 and ECT2. Both systems, thanks to separate phase frequency setting, excitation frequency and amplification can simultaneously focus on different defects such as point defects, cracks, shape defects and others. In addition, both ECT1 and ECT2 systems let you choose the best sorting method based on the size of the signal of the defect compared to the size of the noise.

Each ECT module contains a graphical interface for precise adjustment of the distance between the tester and the surface of the ball.

The EVT tester, using the accelerometer on the main lever of the sorting machine, measures the vibration generated by the movement of the ball at the measuring point during the scan.

Using this supplementary method the machine evaluates the geometrical shape of the ball and, simultaneously, this method can be used for monitoring the wear of some elements of the sorting machine (for example bearings of the functional elements of the monitoring point).