The state of the sand on the basis of the PS plate is the grain size of the aluminum plate after the roughening of the surface. The sand grain structure of the PS plate determines many properties of the plate, and it has an important influence on the printing plate strength. In order to investigate the relationship between the state of the PS plate grain and the printing plate resistance force, we designed the PS plate grain abrasion experiment and conducted an in-depth study.

PS plate sand wear experimental design 1. Experimental content (1) Using a surface roughness measuring instrument to measure the domestic part of the brand PS plate surface roughness of the sand value, analysis of its characteristics.
(2) Using a surface roughness measuring instrument to measure the roughness value of the PS plate before and after printing, and analyzing the change of the grain size before and after printing.
(3) Use a surface roughness measuring instrument to print the contour plots of the PS plates before and after printing to analyze the change of the sand profile curve.
(4) Through the electron microscopy experiment, the state of the sand structure of the PS plate before and after printing was photographed, and the wear of the microstructure was analyzed.
2. Experimental apparatus (1) Surface roughness measuring instrument 1 Instrument accuracy: ≤10%.

2 Measurement method: Measurements were made at different positions of the PS plate before and after printing. Each position was measured at three angles of 45°, 90°, and 135°, and the arithmetic average was taken as the final roughness value.
(2) AMRAY-1000B scanning electron microscope 1 Magnification: 20,000 times.
2 Resolution: 6nm.
(3) PlateDot type X-RiteDot (ccDot) measuring instrument Experimental process and result analysis 1. Measure the roughness and the same plate difference of the PS brand sand in some brands
Some of the domestic brands of PS version of the sand roughness and the size of the same version of the difference in Table 1. It can be seen from Table 1 that the sand roughness of the PS plates of each brand is very different, and the same version difference control of the large-scale PS plate production plants is well controlled, mainly because the production lines are reel production lines and the relative stability is good.
2. Measure roughness of PS plate before and after printing
By measuring the roughness of the sand before and after printing on a PS plate, the wear rate of the sand was calculated, as shown in Table 2. The sand profile curve of the PS plates before and after printing was measured using a three-parameter surface roughness measuring instrument. Combining the data and the sand profile curve to analyze the change of the sand profile curve before and after printing, the following conclusions can be obtained.
(1) Before the printing, the fluctuation of the profile contour curve of the PS plateau sand is larger, and the profile curve of the fine sand on the surface of the sand spot is clear, and the crest and trough are obvious.
(2)
The sand profile curve of the PS plate after printing was relatively flat, the wear at the crest was serious, and the upper fine sand was subject to greater wear and the number of crests was reduced relative to that before printing.
3. Electron microscopy analysis of the status of the PS plates before and after printing Scanning electron microscopy images of the PS plates before and after printing were obtained as shown in Fig. 2.
The two electron micrographs in Figure 2 were compared and the conclusions are as follows.
(1)
Before the printing, the sand structure on the PS plate shows an obvious honeycomb structure. The coarse and fine sand structures overlap each other, and they are scattered at high and low levels, and the crests are clearly defined. Fine micropores are also compounded at the bottom of the sand, greatly increasing the specific surface area.
(2)
The overall structure of the PS plate sand after printing has been greatly abraded, the sand peaks have been worn down, and even some of the fine grit at the peaks have been flattened and the entire surface of the sandstone becomes relatively smooth.

Before printing, the sand head structure generally has both coarse sand and medium sand and fine sand. Coarse sand has good water retention, which can make the printing plate not easy to get dirty. The sand spot can not only improve the printing performance of the printing plate during the printing process, but also guarantee the wear resistance of the printing plate during printing, and improve the printing plate's resistance to printing force. The fine sand mesh greatly improves the hydrophilicity and water retention performance of the printing plate without changing the surface roughness parameters of the printing plateau, and can maintain a large ink even when the printing plate dampening fluid volume is small. The quantity ensures the balance of water and ink during printing and makes the printing plate have good printability.

Through the analysis of the roughness of the sand before and after the printing, the change of the profile curve of the sand, and the photographs of the sand before and after printing, the following conclusions can be drawn: After the printing, the sand is worn and the entire sand structure is destroyed. The abrasion of the coarse sand peaks is heavy, the surface of the upper layer of the sandstone becomes relatively smooth, the abrasion of the fine sand spots is serious, the sand spot wears partially, the hydrophilicity and water retention performance of the sand is reduced, and the printability of the printing plate is affected. When printing, it is easy to produce printing defects such as stencil and dirt.
4. Changes in printing plate before and after printing
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