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This shows that it is necessary to maintain proper process pressure during the printing process. It makes the deformation of the pad greater than the sum of the deviations formed by the various components, so that a good ink transfer rate and satisfactory print quality can be obtained. The process pressure zone p2 to p3 is a relatively large pressure range, and satisfactory print quality can be obtained within this range. However, we always strive to work at the minimum pressure p2, ie, the optimum printing pressure, while considering both the quality of the printed product and the machine load.
In the printing process, the ink transfer rate is affected by many factors, such as the printability of paper, ink, and the printability of other materials. Herein, only the relationship between the printing pressure and the ink transfer rate is analyzed.
The formation of printing pressure is achieved through the printing press's embossing mechanism. Therefore, people in foreign countries call the press a press, which means that the imprinting mechanism is the core part of the printing press, and the printing pressure is the printing press. One of the basic parameters.
Use π to indicate the ink transfer rate, then: where: GG print - the amount of ink on the print; GG plate - the amount of ink on the plate.
According to experiments, the relationship between the ink transfer rate and the printing pressure (kg/cm2) is as shown in Fig. 1 when the printing speed, the ink supply size, the paper conformability, and other various conditions remain stable.
When the printing pressure starts to increase from p0 to p1, the ink transfer rate increases from π0 to π1, and the ink is transferred to the print less. This is due to the fact that the printing pressure p1 is too small to allow the ink in the embossing contact zone to be pressed into full contact with the paper to the extent of mutual adsorption. At this time, the image on the plate cannot be completely copied onto the substrate. There is a clear “emptiness†phenomenon on the substrate. As the printing pressure increases from p1 to p2, the ink transfer rate increases proportionally with pressure. At this stage, as the ink transfer rate increases, the image on the plate can be more completely copied onto the substrate. However, due to the different surface smoothness of the substrate (such as paper), the ink printing pressure is too low to cause the ink transfer rate to be too low and uneven printing occurs. Incomplete copying and exposure of original defects such as plates, gaskets, printers, and paper. On the other hand, if the printing pressure is too high (above the critical pressure p3), the reproduced graphic distortion and color inconsistency will occur due to the “spreading†of the local ink. In halftone printing, the middle tone to the dark tone is blurred. In embossing, too much embossing force will cause the back of the paper to be uneven and even cause incisions, affecting the back of the print and the appearance of the product. Pressing too much pressure will also cause a large deformation of the various components of the press (such as rollers, printing plates, bearings, etc.), thus shortening the working life of these parts, and accelerating the printing plate as compared with normal pressure. And blanket wear.
Listed in the same offset printing press using three different pressures, under the same conditions for the other two different smoothness of the paper, the red ink supplies four printing the measured value of the field value.
Within a certain pressure range, the solid density (indicating the size of the ink transfer rate) increases as the pressure increases.
The National Quality Supervision and Inspection Center for Printing and Decoration Products is a state-level quality inspection center established according to the requirements of the State Administration of Quality and Technical Supervision (now renamed the General Administration of Quality Supervision, Inspection and Quarantine), Jianfa (1988) 056 Document. Since its establishment, the center has strictly established various centers in accordance with the spirit of the relevant documents of the State Bureau, and has passed CNACL (National Laboratory Accreditation in China), CAL, and CMA certifications. Authorizes the supervision, inspection and certification of printing and decorating products and the raw materials involved. The National Quality Supervision and Inspection Center for Printing and Upholstery Products was affiliated with the Tianjin Product Quality Supervision and Inspection Institute and repeatedly undertook the tasks of quality supervision and inspection conducted by the General Administration of Quality Supervision, Inspection and Quarantine. It successively used inks, textbooks, student books, envelopes, national flags, and national emblems. Hong Kong and Macao SAR regional flags, regional emblems and other products were subject to quality supervision and spot checks. And responsible for the identification of new products, the development of relevant national standards, ISO9000 certification and consulting, product quality certification testing, instrument comparison testing, testing equipment configuration consulting, provide relevant standards, technical training consulting services. The center also undertakes the arbitration inspection and quality appraisal commissioned by the State Bureau and local courts and technical supervision departments. As a national laboratory, it also accepts commissions from major domestic companies to provide technology and quality inspection services for enterprises.
The testing center has a constant temperature and humidity laboratory, a chemical analysis room, and an instrument room. It has strong technical force and is equipped with sunshine and weather fastness testers, washable testers, and digital products produced in advanced countries such as the United States, Japan, the Netherlands, and West Germany. Ink viscosity measuring instrument, printing fitness instrument, atomic absorption spectrophotometer, GC/MS, spectrophotometer, gloss meter, densitometer, microprojector and many other high-precision instrument equipments, as well as print and ink And the inspection of harmful elements in related products and the formulation of mandatory standards.
Small talk about ink conversion rate and printing pressure
The 12th floor is difficult to guarantee the same thickness, and there will be “emptiness†in some places. Only when the imprint force is increased to p2, the ink transfer rate can be increased to π2 to obtain satisfactory results. The embossing force continues to increase from p2 to p3, and the ink transfer rate is approximately constant. At this stage, the ink transfer rate tends to be saturated. In the saturation stage, a relatively stable print quality can be obtained. If we continue to increase the pressure to p4, we will “print out†the graphic imprint to the blank part of the non-graphic text, causing the distortion of the printing dots and distortion of the image and destroying the quality of the original print. Conventionally, p2 is called the process pressure (also called the optimal process pressure), p3 is called the critical pressure, the pressure zone of p2~p3 is called the process pressure zone, and P3~p4 is called the overpressure zone.