Design Of Thickness Detection System Of Iron Printing Coating Based On Double Laser Probes

With the continuous development of iron printing industry, the higher requirements are proposed for coating thickness detection technology in the area of sheet metal printing. At present, the method of weighing coating after drying to estimate its thickness is used commonly in enterprises, but the measuring accuracy of this method is not high and it lags. In addition, some coating thickness instruments are sold in the market, such as magnetic, vortex, laser type, etc. The advantages of these instruments are easy to operate and cheap. And the disadvantages are mostly handheld, contact measurement, and measurement points limited, which can not realize thickness automatic measurement and uniformity assessment of the entire sheet metal coating.To achieve high-precision and non-contact automatic coating thickness detection of sheet metal entire surface, the thickness detection system of iron printing coating was designed based on double laser probes combined with mechanical servo devices. The main works are listed as following:1. A coating thickness measurement and uniformity assessment method of sheet metal was proposed based on double laser probes. The influence of metal sheet's Z position changes and mechanical vibration on the measurement results can be reduced by differential measurement principle of double laser probes. Combined with mechanical servo system, the non-contact surface measurement can be achieved by the double laser probes scanning measuring. And coating thickness uniformity can be assessed according to the measured data.2. The thickness detection system of iron printing coating was designed based on double laser probes, including mechanical devices and the hardware and software. The mechanical devices consist of a frame, X-directional transmission mechanism and Y-directional scanning thickness measurement institutions. The composition and design ideas of each part were described. The control system hardware includes the selection and wiring of double laser probes and stepper motors. The main functions of software are film thickness measurement, data processing, and three-dimensional fitting and so on.3. A film thickness assessment algorithm was proposed to assess the uniformity of coating thickness. The least-squares principle and cubic spline interpolation was integrated to fit the discrete thickness data into three-dimensional graphics. And the measurement uncertainty of the system was assessed based on gray theory. The problem was solved that the accuracy was not high of limited measurement data assessing the thickness uniformity of entire sheet metal surface.4. The accuracy of the system was analyzed and tested. The linearity, repeatability and acquisition synchronization of double laser probes were analyzed. The factors of the mechanical device, such as the accuracy of the transmission mechanism, measurement platform flatness, were tested and improved. The coating thickness of sheet metal specimen was measured, and the measurement results were evaluated based on the film thickness assessment algorithm.The results show that the detection system is stable and reliable, the range of coating thickness three-dimensional graphics is 1.4?m and the measuring uncertainty is 1.6?m, which meet the needs of enterprises.