Research on Image Quality Control Technology of Pad Printing

Objective: In this paper, the factors that affect the printing quality of pad printing images are studied, and the pad printing products with excellent printing quality are obtained. Methods: Using electronic depth of field microscope to measure the dot cell depth of different pre exposure plates on the solid plate and dot area ratio, the effect of cell depth on the transfer process of pad printing ink was analyzed; Use the software Photoshop to draw the measurement and control strip, then which are used to make the printing plate and proofing, at last the spectrophotometer is used to test the dot area rate of the sample, analyze the difference between the output dot area rate and the tested dot area rate, establish the compensation curve of the image original in the software Photoshop. Results: With the extension of pre exposure time, the cell depth at the same dot area ratio on the printing plate decreased; the cell depth at different dot area ratio on the printing plate decreases gradually with the decrease of dot area ratio. The dot area ratio of 60–100% and less than 30% has an approximate linear relationship with the cell depth, and the cell depth at the dot area ratio of 30–60% has little change. For the unadjusted image originals, there is a large gap between the actual printed dot area rate and the output dot area rate, which is also the main reason for the printing quality problems. After the compensation curve adjustment of the image originals, the density value of the measurement and control strip obtained from proofing is basically consistent with the expected value. Conclusion: If the thickness of the transferred ink layer is too thick, it will be difficult to completely dry, which will lead to printing failure. Therefore, controlling the cell depth at the solid plate of the printed matter is an important means of printing quality control. The cell depth at the solid plate should be controlled at about 35 microns; the printing quality of the image originals adjusted by the compensation curve is greatly improved.