In screen printing, scraping blade has a great influence on the quality of printing quality.Should be familiar with the performance characteristics of scraping blade, to master its use points, to ensure that used in the printing.

A, scraping blade production materials and main performance

1, production materials

At present, scraping blade mainly with rubber and steel sheet, aluminum alloy plate, etc.Different material properties is different, the applicable scope is also different.In rubber materials (including natural rubber, neoprene, polyurethane rubber and synthetic rubber, etc.), the wear resistance of natural rubber and chloroprene rubber is not good, color is deeper, but the price is low, so the more used in manual printing.Polyurethane rubber scraping blade has good abrasion resistance outstanding characteristic, the color with deep light color (generally the lighter the better its quality), the best quality with light yellow, its wear resistance, solvent resistance, the better.Aluminum alloy is used mainly for distributing knife, has many characteristics, such as lightweight, easy to loading and unloading.Sheet steel material is mainly used to produce fabric scraping blade on the silk screen printing machine.

2, performance indicators,

To determine the quality of scraping blade performance indicators mainly include hardness, wear resistance and chemical resistance.

A and c said the hardness and elasticity of the scraping blade, refers to the degree of deformation scraping blade pressure.Hardness is generally expressed in shore hardness value, the higher the value, the greater the hardness, hardness conversely.For screen printing, the printing ink transfer and graphic reproducibility are associated with the hardness of scraping blade.Hardness is small for scraping blade contact with wire mesh, to fill the ink has a good effect, but the scraping blade bending resistance is poor, easy to make scraping knife and web plate Angle changes, affect the printing quality stability;High hardness, good resistance to bending of scraping blade, but contact with the silk screen, is not conducive to fill the ink, and printing on the web version of the frictional force was also big, make wear silk screen is bigger, sometimes can also affect the printing precision.

According to the hard and soft contact with better characteristics, at the time of printing, if it is a soft material, such as paper, plastic film, etc.) or more smooth substrates, can choose a hard scraping blade.And if it is a hard material (such as glass, metal, etc.), or relatively coarse substrates, choose hardness of scraping blade.

Because the scraping blade when scrapping printing under pressure and bending, therefore, want to consider the bending fatigue of scraping blade and mechanical strength, require scraping blade has a certain flexibility.Scraping blade when scrapping printing due to the friction heat production, make its temperature hardness change, therefore, should choose is not easy to deformation of the heated material scraping blade.

For scraping blade material hardness, usually can be divided into soft, neutral, rigid three blade.Soft blade hardness for 45 to 50, should the blade hardness is 75-90, generally choose 60-80 as well.Such as printing precision and quality requirements of high color screen printing, the scraping blade hardness is 70.

B, abrasion resistance is mainly used to measure the scraping blade service life.Because the scraping blade, direct contact with web plate is every time scrapping printing have friction (in screen printing with a long up to tens of thousands of times), therefore requires better scraping blade abrasion resistance and mechanical strength.In addition, scraping knife also has certain lubricity, so when scrapping printing can reduce friction, in order to prolong the service life of scraping blade.

C, chemical resistance, main is to guarantee scraping blade in contact with the ink, solvent, etc without chemical change, keep the original quality.Scraping blade in use is not only to contact all kinds of printing ink, but also in contact with the solvent (such as ethanol, gasoline, etc.).Because of solvent affinity for all kinds of rubber material is different, so the scraping blade hardness and the change of volume, solvent volume expansion after the contact deformation.And scraping blade inflation can reduce the edge of the scraping blade precision, makes when printing ink uneven and affect printing quality.Generally speaking, the high hardness of the rubber crosslinking density is big, printing ink and solvent molecules into rubber molecules, so the expansion coefficient is relatively small, so can consider when choosing scraping blade on the premise of meet the requirements of printing, try to choose high hardness rubber scraping blade, in order to make deformation is reduced to a minimum.

In addition, the performance index of scraping blade and wet resistance, corrosion resistance and heat resistance, etc.All in all, require scraping blade must have resistance to mineral, vegetable oil and naive, and can withstand inks is contained in the influence of the composition such as metal oxide.

3, the blade shape

Scraping blade mouth shape basically with a square head, point, and round head.Different substrates, should choose different when printing blade scraping blade shape.

A, printing is the most commonly used planar substrates lag scraping blade, the blade Angle is 90 °, the shape of the cross-section for the rectangle.Coach scraping blade, most widely used grinding is convenient, its four edge strip can be used, usually choose the straight blade scraping, no defects.

B, pointed scraping knife blade has 45 °, 60 °, 70 ° several shapes, usually used for surface printing.Under the condition of without considering the ink viscosity, viscosity, the smaller the Angle of scraping blade mouth, is through the less of printing ink, the clearer the mark also.But the smaller the Angle, grinding the harder to fix, scraping blade service life is short, so when using the acute Angle of blade scraping blade, should choose high hardness and wear resistance of scraping blade strip.

C, round head, scraping knife blade is arc shape, has the branch of truss head and a small round head.Small round head low scraping blade are used for printing ink viscosity, printing precision is not high print to print;Truss head scraper is suitable for large area ground printing fabric.

Choose the scraping blade edge shape, from the ink viscosity, printing method, scraping blade material, shape of substrates and substrates, considering printing precision, etc.

The use of the two, scraping blade technology

Manual printing with scraping knife scraping handle generally made from wood, its shape to adapt to the request of the manual, scraping and distributing two role.Machine with scraping knife scraping handle generally made from metal, the shape of it to conform to the requirements of the installation of screen printing machine.

Installing a scraping blade, scraping blade strip out the length of the scraping handle by strip hardness, printing ink viscosity and other printing condition decision.General printing with a soft rubber scraping blade loading part want to some more, larger scraping blade rubber hardness less loading part, which show the part should be some more as well.Attention should be paid to the following:

A, ze blade, one end of the straight without defect for A difference in A handle at the end of the edge.

B, when cannot damage the blade.

C, when installing scraping blade on the screen printing machine, screw don't twist too tight so as not to damage the scraping blade, and scraping blade to contact with the surface.

D, scraping knife scraping handle light height is miniaturization: printing requirements and decide, if you need scraping blade soft, can reveal more (25 to 30 mm), if you need scraping blade a bit hard, but with less (10 to 25 mm).