An investigation and development of a novel quality control system based on contactless resistivity measurement

Measuring the diameter of a metal product during manufacturing is an important Quality Control activity in many industries including manufacturing of wires, nails, metal tubes and many more. Using manual measuring techniques in such situations is impractical because it is slow and time consuming. Many attempts have been made to automate the monitoring of the diameter of manufactured wires without disruption to the manufacturing process but these systems are either complicated to set-up or very expensive.

This thesis investigates the feasibility of measuring the diameter of a conductive material with circular cross section area (e.g., wires, rods, nails, etc) without making any physical contact with the material itself. Such a measuring system could be extremely useful as a Quality Control mechanism for monitoring the fluctuations in the diameter of manufactured wires, rods or nails without disrupting the manufacturing process. The experimental activity has involved the design, construction and testing of a prototype system to measure the diameter of different metals, both solid bars and hollow tubes, without making physical contact with the samples.

The theory of operation of the proposed system is based on the well-developed Contactless Resistivity Measurement theory used in Solid State Physics where the main interest is to measure the resistivity of the material knowing its dimension. In this project, we are trying to investigate the feasibility of using the same principle to measure the dimension of the sample knowing its resistivity. Results presented in this project proved the possibility of measuring the diameter of a conductive material without making physical contact with it.

Further research will include: Increase the accuracy and reliability of the system; consider the effect of a moving wire on the accuracy and reliability of the measurement; developed a real-time industrial system. Further research will include measuring the thickness of thin metal coats where the physical measurement of thickness is extremely difficult and complicated.