Relationship between Paper Smoothness and Printing and Its Measuring Instruments (III)

Smoothness meter

Smoothness has a huge impact on the quality of prints. In the papermaking process, it is necessary to try to improve the smoothness of the paper. When printing, it is necessary to select papers with different degrees of smoothness according to the quality requirements of the prints. This requires the quantification of smoothness. In the national standard, "seconds" is used to quantify them, and the corresponding instrument is a smoothness meter. Due to the importance of smoothness in papermaking and printing, it is necessary to accurately measure it and put higher demands on the instrument.

In order to assess the surface smoothness and print smoothness of paper, many previous researchers have studied a number of assessment methods and designed a variety of corresponding measuring instruments. The smoothness meters produced according to different measurement principles include: air leakage method, optical contact method, needle tracing method, and water trace method. In the application, the most practical and most widely used is the measurement of paper smoothness by the air leakage method, which is represented by a Buick smoothness meter.

1. The structure of the Buick smoothness meter

The Buick smoothness meter consists mainly of pressure members, glass plates, vacuum vessels, vacuum pumps, vacuum solenoid valves, sensors, peripheral displays and keyboards. The Buick Smoothness Meter currently used is not suitable for the determination of paper and paperboards with a thickness of more than 0.5 mm or very high air permeability because a large amount of air passing through the test surface will affect the test results.

Compression components are: heavy weight, pressure plate and pad. At present, most of the domestic use of heavy pressure to carry out pressure, the pressure is applied to the paper sample to be measured through the heavy pressure, the size of the pressure is (100 ± 2) kPa. Pressure plate is a flat surface of the diameter of 45mm circular plate, the plate is fixed The pressure is in contact with the sample. The pad is a circle with a diameter of not less than 45mm or a square with a side length of not less than 50mm, a thickness of (4±0.2)mm, a maximum thickness variation of ±0.05mm, and a hardness of (40±5)IRHD (International Rubber Unit). Resilience is at least 60%.

The glass plate (shown in Figure 2) has a ring shape with an effective ring area of ​​10 ± 0.5 cm2. The center hole of the glass plate can be connected to a vacuum vessel and can also be disconnected. The test surface is precision polished, no scratches and cracks, and should be kept clean during use. A support column is placed in the hole in the center of the ring, and its upper surface is flush with the surface of the glass plate to prevent the sample from being sucked into the hole. There are 4 radial slots on the support column for smooth air passage.

Vacuum vessels, vacuum pumps, vacuum solenoids, and sensors are the devices that control the operation and measurement of air. The vacuum vessel includes a large vacuum vessel and a small vacuum vessel, which can be evacuated to 53.35 kPa and kept sealed. They are each connected to a glass plate. The volume of the large vacuum vessel is (380±1) ml, and the volume of the small vacuum vessel is (38±1) ml. The vacuum pump is used for vacuuming to ensure that the required vacuum is met. degree. The vacuum solenoid valve is used to control the flow of gas and disconnection, through which you can control the measurement in the pre-pressure or measurement phase. The sensor is used to measure the pressure inside the vacuum container, and the working range is 50.66-48.00kPa or 50.66-29.33kPa.

2. The function of Buick smoothness meter

At present, most smoothness meters use high-precision vacuum sensors to measure the vacuum degree of the vacuum container, thereby replacing the mercury pressure gauge. Therefore, the instrument is a mercury-free smoothness meter and will not cause any harm to humans. The instrument uses vacuum mercury to draw vacuum from the vacuum container and can reach the required vacuum in a very short time and is controlled by the single chip microcomputer. The instrument uses a single-chip microcomputer also has a powerful data processing function: not only can measure the smoothness value of a single sample and automatically store, but also can count the experimental data of multiple samples in the same group, and calculate the maximum and minimum of the same group of samples. Values, averages, standard deviations, and coefficients of variation are stored in the data memory and can be displayed on the LCD screen. In addition, the instrument also has a printing function: according to the international GB/T456-1989 requirements for the smoothness test report, the statistical data of the tested samples are printed according to the requirements of the experimental report.

The above analysis shows that the smoothness of the paper surface will have a great impact on the printing quality, which is why paper mills and printers pay attention to the smoothness of the paper. Therefore, in order to obtain high-quality prints, it is necessary to quantitatively evaluate the smoothness of the paper, that is, use an instrument to measure it objectively so that it can meet the printing requirements; at the same time, the instrument is also very practical in the paper industry and can guide manufacturers. Create qualified paper.