Screen printing 1000 questions (11-20)

â–¼11. What is a tension meter?

The tension meter is an instrument for measuring the mutual traction force between the interior of the wire mesh and the fixed wire mesh contact body when the wire mesh is subjected to a pulling force. Tension meters are available in both mechanical and electronic versions. The unit for measuring tension is expressed in Newtons/cm. Tension can also be expressed as a relative value. The centimeter tension meter is a type that expresses the tension with a relative value. It is calculated by the value (mm) of the depth at which the screen sinks by the weight of the tension meter. The tension value can be obtained directly from the indicator disc or indirectly from the control panel. get. Tension meter has two kinds of manual operation and mechanical operation. Tension meter is an important test instrument for checking the quality of screen printing plates. In order to ensure the tension required for plate making, a tensiometer should be used during stretching or after stretching.

â–¼12. What is a mesh ruler and what is its use?

The mesh ruler is also called the density meter. It is mainly used to measure the mesh number of various screens. There are two types of glass ruler: glass plate and plastic plate. The measuring method is: When measuring, first make the screen in a translucent state or on the viewing table, put the mesh ruler on the screen, and then slowly move the mesh ruler on the screen to make the mesh The vertical line on the ruler is parallel to the meridian or weft of the wire mesh. At this time, due to the overlapping effect of the wire mesh latitude and longitude lines and the vertical line on the mesh ruler, a prismatic pattern is formed on the mesh ruler, and the transverse diagonal of the pattern indicates The corresponding scale number on the screen scale is the number of meshes (inches or centimeters) of the measured screen.
Mesh ruler is a common tool for measuring the number of screen meshes. Usually, to maintain the accuracy of the measuring instrument and measure the accuracy of the data, it is necessary to keep the mesh ruler clean and prevent scratches and bumps on the mesh ruler after use. Wipe the instrument clean and keep it properly.

â–¼13. What is a density meter and what is the purpose of the density meter?

Density meters are the original manuscript measuring instruments commonly used in printing plants. It is an optoelectronic measuring instrument that measures the grayscale value of black and white originals and measures the continuous tone or dot value. Densitometers are classified into transmission densitometers and reflection densitometers. Transmissive densitometers are suitable for measuring transparent manuscripts and reflective densitometers are suitable for measuring solid manuscripts. Densitometer measurement range is 0-2.5, the greater the number, the higher the blackness. The basic principle of the measurement is to measure the degree of blackening after light exposure and development of the photosensitive material. At the time of plate making, the silver bromide on the photosensitive material is exposed to light, and after development, it is reduced to metallic silver to form a certain degree of opacity. Darkness, high density; darkness, low density. A meter with a filter can also measure the color density of a color document. The measurement principle is similar to the above basic principle.

â–¼14. What is a colorimeter and what is its use?

Colorimeter is also called colorimeter. It is an instrument that measures the color characteristics of a material. The main purpose of the colorimeter is to measure and analyze the color, hue, and color values ​​of the measured materials. If the colorimeter is connected with a computer, the analysis and processing ability of the color can be improved, and the user can search and call out various data for color matching from the color storage of the microcomputer as needed.

â–¼15. What is a hardness tester and what is its use?

The hardness tester is an instrument for measuring the hardness of an object. According to the degree of complication, it can be divided into two types, a simple hardness tester and a complex hardness tester. The hardness meter is widely used in the rubber industry. In the screen printing process, the hardness meter is mainly used to detect the hardness of the scraper material.

â–¼16. What is the purpose of the scraper gauge?

The blade pressure gauge is a display instrument that measures the friction between the blade and the screen according to the blade pressure. The unit of measurement is kg/cm. The test method is: Place the test strip between the wiper and the wire mesh, and use the pressure gauge to perform the pull test method. During the measurement, according to the number indicated on the dial, the friction value is obtained.

â–¼17. What is the purpose of the scraper and what is the specific coating method?

The scraper is a tool for coating a sensitizer on a screen, and is also referred to as a masher. Commonly used scrapers are made of stainless steel. This kind of scraper has the characteristics of light weight, light weight, strong corrosion resistance, no rust, and easy fabrication.
There are two uses of the scraper, one for applying sensitized adhesives and the other for sealing nets. When applying the emulsion, the photosensitive emulsion is poured into the scraper first. Generally, the amount of the emulsion does not exceed 1/2 of the scraper capacity. When using, stretch the net frame of the net by about 70 degrees, and lean against the fixed bracket, and place the edge of the scraper placed in the emulsion horizontally against the bottom of the net frame, and then make the scraper slightly upward. Tilting makes the sensitizer contact with the Internet. Then make a smooth movement from bottom to top. In order to make the photosensitive film and the screen firmly integrated. The coating is applied on both sides of the frame. The number of coating outside the frame is more than the number of coating inside. The specific method of operation is: draw once, dry once. In order to ensure the uniform thickness of the coating film, the position of the mesh frame is switched back and forth after each application of a scrape, and it is reciprocated in accordance with this method of operation until the desired thickness of the film is reached.

â–¼18. What are the main technical specifications and requirements of the scraper?

From the foregoing, it can be seen that the scraper is an important tool for coating the photosensitive adhesive, and the quality of the scraper directly affects the quality of the screen printing plate. It should be noted that there are the following aspects: The first is the edge of the blade where the scraper is in contact with the wire mesh. A high degree of flatness must be ensured and no traces of bruising can occur. If the flatness is low or there is a bump, the streak or thickness of the film layer will be uneven after the coating is applied, so that the burr and the thickness of the ink layer are uneven after the printing. The second is the requirement that the edge of the edge be smooth. If this is neglected, it will cause the consequences of damaging the screen when coating. The third reason is that because the stretched screen has a certain degree of elasticity, the thickness of the film tends to be uneven when the coating is applied, that is, the film thickness is thin in the middle and the film is thin on the four sides. In order to avoid such problems, the side of the contact screen is usually purchased in a certain arc shape when the squeegee is manufactured, so that the phenomenon of uneven film thickness due to the elasticity of the screen can be avoided. The fourth is to use rust-free, corrosion-resistant, light-weight stainless steel materials when making scrapers.

â–¼19. What materials are used to make the frame and what are the characteristics of these materials?

The materials used to make the frame include wood, hollow aluminum profiles, cast aluminum molding frames, and steel materials. The most commonly used is the frame made of aluminum. However, all kinds of network frames have their own characteristics. When selecting, different network frames can be selected according to different situations.
The wooden net frame has the characteristics of simple production, light weight, convenient operation, low price, and simple stretching method. This frame is suitable for manual printing. However, the wooden frame of this wooden material is poor in solvent resistance and water resistance, and is easily deformed after being immersed in water, which affects the printing accuracy. This kind of mesh frame was commonly used before and it is rarely used nowadays.
Hollow aluminum profile net frame and cast aluminum molding net frame have the features of easy operation, high strength of net frame, firm deformation, high resistance to solvents and water resistance, and beautiful appearance.
Suitable for mechanical printing and manual printing.
The steel net frame has the characteristics of firmness, high strength, and good resistance to solvents and water, but it has the disadvantages of being bulky and inconvenient to operate, so the scope of use is very small.

â–¼20. What are the conditions for selecting a frame?

The network frame is one of the important materials for making screen printing plates. The appropriateness of the selection of the frame has a direct influence on the plate making quality and on the printing quality. In order to ensure the plate making, printing quality and other requirements can be selected based on the following conditions.
1 The frame must have some strength. Because when the net is stretched, the wire mesh has a certain tension and pressure on the net frame. This requires the frame to withstand pressure, can not be deformed, to maintain the frame size accuracy.
2 Under the condition of ensuring the strength, the net frame should be chosen as light as possible for easy operation and use.
3 The mesh frame and screen bonding surface must have a certain degree of roughness in order to strengthen the adhesion of the screen and the frame.
4 The sturdiness of the frame. In the use of the network frame, it is often in contact with water and solvent, and is affected by changes in temperature. This requires that the screen frame is not skewed, so as to ensure the repeated use of the frame. This will reduce waste and reduce costs.
5 The network frame with different specifications should be configured in production. When using, the appropriate frame can be determined according to the size of the printing size, which can be less wasteful and easy to operate.

--Qi Lu Graphic Arts