Factors to be considered in ink layer control in t

2022-10-18
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Factors to be considered in ink layer control in silk printing

release date: Source: China paper

in various processes of packaging and printing, some key nodes in silk printing need to be effectively controlled. Today, China's paper industry starts with silk printing. Let's introduce in detail the issues that need to be considered

let's first review some of the problems we have in the past in printing: 1. When printing color blocks, the color is dark and light. 2. The printing time point of eye tone is enlarged (with moire phenomenon). 3. Color difference change during batch printing. When these problems are serious, they will affect the production progress and batch return, and bring inconvenience to our work normalization. So how to control and replace the jaw at this time to prevent these problems is a problem worthy of our printing workers to discuss. The following are the variables we should know in printing

first, analyze the theoretical ink transmission:

there are two methods to analyze the ink transmission of silk, one is to calculate the theoretical ink transmission of silk, and the other is the actual printing ink transmission. The following formula is used to calculate the theoretical ink transmission:

the opening ratio is: l

the thickness of the wire is: d

the theoretical ink transmission is: m=l × D ÷ 100%

the above formula is only a theoretical method to calculate the ink penetration of silk. Once applied to practical printing, the data will change, but it is proportional. Let's look at the following factors:

1. The mesh number of wires (directly determines the hole width and opening rate). The higher the mesh number of wire, the smaller the hole width, and the hole opening rate will decrease. For example, the hole width of 355 mesh wire is 31 μ m. The opening rate is 26%, and the theoretical ink penetration is 14.3cm3/m2. 305 mesh wire hole width is 45 μ m. The opening rate is 35% and the theoretical ink penetration is 16.3cm3/m2

2. Wire diameter of wire (directly affects thickness, opening rate and hole size). It refers to the diameter of the unwoven wire diameter, and the braided wire diameter will become oval. Will affect the size of the hole. Different wire diameters with the same mesh number will also affect the opening size and opening rate

for example, the wire diameter of 305 mesh wire is 31um, the opening rate is 35%, the hole width is 49um, the thickness is 49um, and the theoretical ink penetration is 17. 2cm3/m2。

305 mesh wire diameter is 34um, the opening rate is 29.6%, the hole width is 45um, the thickness is 55um, and the theoretical ink penetration is 16. 3cm3/m2。

305 mesh wire diameter 40um opening rate is 20. 1%, the hole width is 37um, the thickness is 65um, and the theoretical ink penetration is 13cm3/m2

3. The thickness of the silk (directly affects the ink layer). We can use a thickness gauge to measure the thickness of the stretched version. Because the silk produced by each manufacturer has its own weaving process, the warp and weft threads have different bending degrees. The greater the bending degree, the thinner the silk will become, and vice versa. In the stretching process, due to the influence of external force, the wire diameter is stretched, which will eventually affect the thickness of the wire

4. The hole width of the wire (directly affects the ink amount). We know that the wider the hole, the greater the amount of ink under it. In the stretching process, the higher the tension, the lower the mesh number, the wider the hole, and the greater the ink transmission

5. The opening rate of silk (directly affects the ink amount). The so-called open hole rate refers to the ratio of ink transmission area to the total area in the unit area of silk. For example, for the silk with a hole opening rate of 35%, the ink permeable part is 35%, and the part that is impervious and blocked by the silk is 65%. The higher the hole opening rate, the greater the ink amount of the silk

calculation formula:

hole width: k

mesh number: m

inch unit: y

opening rate: l=k × M÷Y2 × 100%

6. The pressing plane of the wire (directly affects the thickness and hole width)

imported wires above 355 mesh are mostly flattened. The flattened wire will obviously become thinner and the hole will become smaller. When the flattened silk is stretched, let's take the following examples: stretching the pressing plane towards the ink scraping surface can save ink by 10% - 15%, and stretching the pressing plane towards the substrate surface can save ink by 15% - 25%

II. Actual printing ink penetration:

1. The tension of the plate (affecting the size of the opening, the number of wire meshes, the wire diameter, and the thickness). In the process of stretching, with the increase of tension, the technical parameters of the wire itself will change accordingly. First, the mesh number of the wire is affected. The higher the tension is, the greater the mesh number decreases (until the plastic deformation of the wire occurs). Next, it will affect the hole width of the wire, the hole will become larger, the wire diameter will become thinner, and the cloth will become thinner. These factors will eventually lead to the change of the ink amount

2. The thickness of the film (determines the amount of ink). If we use photoresist to make plates, we also need to consider the solid content of the photoresist itself. After making plates, the film will be?? The water is volatilized, and the film will become thinner. So we can only use a thickness gauge to detect the overall thickness of the plate

3. Ink type (indirectly affects the ink layer thickness). We know that solvent based inks will volatilize after printing, and eventually the ink layer will become thinner. After printing, the resin solidifies instantly after being irradiated by ultraviolet light, so the ink layer remains unchanged

4. Viscosity of ink (indirectly affects the thickness of ink layer). The lower the viscosity of the ink, the thicker the ink layer will be in the printing process, because the ink itself contains less solvent, on the contrary, the thinner it will be

5. The hardness of the scrape (indirectly affects the thickness of the ink layer). In the printing process, the higher the hardness of the squeegee, the less likely it is to deform, the smaller the amount of ink, and on the contrary, the larger it is

6. The tolerance of the scraper (directly affects the ink amount). It is easy to operate. If the blade of the scraper is at a right angle, the amount of aluminum ore and its concentrate imported from China is 55.692 million tons, which is small. If it is at an obtuse angle, the ink amount is large

7. Angle of scraper. (indirectly affect the ink layer thickness). During printing, the smaller the angle between the scraper and the plate, the greater the amount of ink, because the scraper and the plate are in face contact. On the contrary, it is small

8. The pressure of the scraper (directly affects the ink amount). During printing, the greater the pressure on the scraper, the smaller the inking. The reason is that the contact terminals of the ink connecting column cannot mix together and have been driven away before being completely extruded out of the hole. On the contrary, it is small

9. Pressure of inking knife (direct inking volume). The greater the pressure applied to the ink return knife, the greater the amount of ink, because a small amount of ink has been squeezed out of the hole by the ink return knife before scraping. On the contrary, it is small

10. Scraping speed (indirectly affects the ink layer thickness). The faster the printing speed is, the smaller the inking is, because the ink has been squeezed out before the hole is fully filled, causing ink supply interruption

11. Printing materials. (directly affects the ink layer thickness). The surface flatness of the substrate will also affect the thickness of the ink layer, and the rough surface ink will penetrate (such as woven fabrics, leather, wood). On the contrary, it is large

12. Printing environment (indirectly affects the ink layer thickness). A problem that we have been easy to ignore is the change of temperature and humidity in the printing workshop environment. If the temperature of the printing environment changes too much, it will affect the ink itself (such as the viscosity and fluidity of the ink)

III. how to calculate the thickness of the ink layer

through the above discussion, we know that if a certain link changes in the printing process, it will eventually lead to inconsistent inking volume, so how should we calculate the thickness of the ink layer? One method is to weigh the wet ink. First, try to keep every link in the printing unchanged. After printing, weigh the weight of the substrate, and then subtract the original weight of the substrate, and the obtained data is the weight of the wet ink. The other method is to measure the thickness of the ink layer. Use a thickness gauge to measure the thickness of the substrate after inking, and then subtract the original thickness of the substrate, and the obtained data is the thickness of the ink layer

IV. how to control the thickness of the ink layer

how to control the thickness of the ink layer has become a problem faced by printers. The first thing we need to do is to use the existing measuring equipment to ensure the accuracy and objectivity of the measured data; Conditional factories can use automatic coater to complete the gluing process to ensure the thickness of the adhesive layer. The next thing to do is to ensure that every link in plate making and printing is kept unchanged as far as possible. Every printing parameter should be recorded to provide ideal data for finding the appropriate ink layer thickness

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