Development Of Non-destructive Eddy Current Testing System For PCB Hard Alloy Rod

The eddy current testing method，based on Faraday’s law of electromagneticinduction，is a nondestructive detection technology, which can be used for the cases ofhigh-precision measurement tasks. Eddy current testing is moving in severaldirections, based on the eddy current nondestructive testing equipment, the price isgenerally high. PCB hard alloy rods are used for PCB drills, and are usually machinedby centerless grinding process. There are some machining defects during centerlessgrinding process, and it is difficult to detect those defects by operators. A new on-linenondestructive eddy current testing method is proposed to detect PCB hard alloy rodsdefects.The PCB detection system includes the eddy current sensor, pre-amplifier, dataacquisition card, combined with self-developed testing procedures and devices; it iseasy operation and high measurement accuracy. The detected signal by eddy currentsensor is transferred to the preamplifier, then conditioning to the enlarged voltagesignal is acquainted by the data acquisition card, and is compared with the referencevoltage in the testing system, at last, the testing results is output. The main content ofpaper is as follows:(1) Electrical impedance analysis of eddy current testing, a mathematical modelto determine the best excitation signal frequency range is set up, and featuresparameters of testing system are determined by the theoretical analysis. Thesimulation of eddy current testing by FEM analysis is carried out and obtained thedistribution map of the magnetic field, the magnetic field flux density(2) According to the actual requirement of the testing, the best signal-extractionprogram is proposed. Software developed by LabVIEW can realize the on-linedetection of PCB hard alloy rod defects. Some additional functions such as saving ofacquainted data, a statistical histogram product distribution are also developed andcan used for centerless grinding process improvements.(3) A detection device is designed using the selected hardware platforms andsoftware programs to verify the two influencing factors of the eddy current testing,the experiments results show that developed detection system is effective to test thedefects of PCB hard alloy rods.(4) The detected signal of defects can be used to select defected PCB hard alloy rods from the production lines, and the productivity is increased greatly.