Performance parameters of squeegee
In the selection of suitable performance of the squeegee, need to consider the following four factors.
(I) Hardness
Gelatine is usually made from polyurethane and its hardness is measured using a durometer.The size and blade shape determine the bending, flexibility and pressure of the squeegee.The hardness range is 55~-90°, and the hardness value is measured by Shor A hardness meter.
Ink transfer and graphic reproduction is related to the hardness of the scraper, generally in the hard substrate printing, you can use soft scraper, so through the pressure applied when the scraper can make the layout and substrate contact enough to improve the printing effect.On the contrary in the printing of soft substrate, to use hard scraper so that the layout and substrate contact is good, the truth is the same.Due to a variety of substrate, substrate materials are not the same, the smoother substrate generally choose a harder scraper;On the contrary, with a softer scraper printing effect will be more ideal.Squeegee at the time of squeegee printing due to the application of a certain pressure, the squeegee will have a certain bending, therefore, when using the squeegee, the bending fatigue and mechanical strength of the squeegee should be considered.Require the plate to be provided in a certain elasticity.Squeegees at the time of squeegees will produce heat due to Morgan, making the hardness change after the degree of withdrawal increases.In such scraper material, the attention should be paid to choose the material that is not susceptible to heat deformation.
(2) Effective width
Effective width refers to the squeegee loaded into the aluminum scraper handle, from the aluminum scraper handle out of the width of the squeegee.This width is important in determining the bending of the squeegee under pressure.The curvature is the cubic value of the effective width, for example, twice the effective width results in a bending greater than 23mm/m.
Squeegees bending will cause two aspects of change, one is the squeegees and screen between the Angle change, the second is the transfer to the substrate printing pressure.For example, the squeegee is compared to a set of springs. When the spring is stressed at a certain Angle, the spring begins to bend and the force transferred becomes smaller and smaller.Squeezer printing Angle decreases, printing pressure is insufficient, printing effect is not ideal.The printing Angle is small, the printing pressure decreases, the ink volume is large, the ink layer thickens (in this case, the printing operator will increase the printing pressure, the squeezing-bending degree increases, the resulting ink layer is still not ideal.The solution is to increase the hardness of the squeegee, squeegee Angle.This is the effective width of the squeegee on the four functions of the squeegee.
Usually the effective width of the squeegee is 20~ 30m.The selection of the best effective width is based on the flatness of the substrate, image resolution of the screen layout and other printing parameters such as squeezer Angle: speed and oil base type. When printing the image of high image resolution force on the flat and smooth substrate, use the squeezer with small effective width (less than 20m) and high hardness, and with appropriate ink for rapid printing.In the uneven, rough substrate, can also be used in the middle of hard, soft on both sides of the three – layer or double – layer scraping.In general, the effective width increases, the printing speed decreases, and the printing Angle increases.
(3) The shape of the squeegee
Squeegees refer to the cross section of the squeegees. Most squeegees are simple square squeegees. Other squeegees are used for specific printing conditions.For example, hard squeegee has better performance than soft squeegee.But the adaptation of the substrate poor, the use of oblique scraping, printing edge deformation.
There are three kinds of squeegees for printers to choose, namely square squeegees, all kinds of slanting squeegees and round squeegees (horn squeegees) square squeegees are applicable to a wide range, which can provide the maximum printing pressure, and the printing Angle is set according to the effective width.Diagonal scraping provides maximum flexibility, reduced printing pressure and a smaller printing Angle than the set Angle.Circular scraping is the least adaptable, provides the least printing pressure, printing Angle can be set freely, the above reasons will affect the amount of ink.
(4) Knife edge
The knife edge is an important part to perform the four functions of the squeezer.The sharpness of the squeegee is a factor that initially controls the amount of ink.The sharp spatula provides the smallest amount of ink and the finest image.Blunt and round force mouth, the amount of ink under the increase, at the same time will affect the color and line fineness.When printing large areas and simple patterns with transparent oil, the change in color and line fineness is not obvious.And printing fine lines and four color dot, with translucent (UV) and transparent ink, will soon find the deformation of the knife edge, printing, printing, can be printed on the first and the last one to compare, you can determine when the squeezes should be polished.