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技術信息

技術信息

Door to Screen-Printing

- SCREEN-PRINTING BASIC LECTURE -

BASIC SCREEN-PRINTING

Q1
What are the three and an additional essentials of screen-printing?
  • A:
  • It is said that screen, ink and squeegee are the three essentials of screen printing, along with workpiece to be printed with ink.
Q2
Which in the three essentials of screen-printing is the most important?
  • A:
  • The most important thing in screen-printing in the nature of printing is ink. Ink and workpiece will be retained with features given. A product is characterized by the two elements, while the condition is decided by the screen and squeegee. However, the ink decides if the workpiece is printable or not.
Q3
What does paste rolling mean in screen-printing?
  • A:
  • It means that paste rolls between the screen and squeegee. If the roll is unstable, the paste does not go through the screen stably.
Q4
What does screen peeling mean in screen-printing with a mesh screen?
  • A:
  • It means that a screen is separated from a workpiece right after ink is printed by the squeegee when a clearance (gap) is made for a mesh screen. The screen needs to be separated little by little as the squeegee moves.
Q5
What is a clearance (gap) in screen-printing?
  • A:
  • It is a space between the screen and workpiece, which is necessary for good printing (and peeling).
Q6
How does ink go through a mesh screen in screen-printing?
  • A:
  • Ink sticks in the meshes of screen, and the meshes and workpiece scramble for the ink. At this, the ink is transferred onto the workpiece being squeezed out by the squeegee pushing and by the roll of the ink, and being separated by the tensioned screen.
    To understand how ink goes through meshes is important to solve a printing condition/printing problem.


BASIC SQUEEGEE

Q1
What tyoes of squeegees are there?
  • A:
  • There are three types generally: flat, square and sword.
Q2
What is a squeegee generally made of?
  • A:
  • Urethane rubber generally is popular. However, each maker has rubber with different feature by slightly changing the mixture.
    Furthermore, there are squeegees made of silicon rubber, synthetic rubber, metal, plastic, etc., which are rather exceptional.
Q3
What is the most popular type of mesh screen?
  • A:
  • Flat type squeegee. Flat type squeegees are generally used while some industries use square or sword type sqheegees. NEWLONG also recommends flat type squeegees since they are regrindable and enable easier maintenance of uniform edges.
Q4
How many degrees does squeegee rubber range in hardness?
  • A:
  • Basically, there are three kinds of hardness: 80, 70 and 60 degrees.
    There are rubbers with hardness of 90 degrees or of units of 5 degrees, yet rubber varies widely in hardness. According to the rubber makers, the variations of hardness are between -5 and +5 degrees.
    NEWLONG presently considers the hardness control of rubber to be within -0 to +5 degrees.
    The hardness of squeegee rubber is indicated by a hardness tester complies with the JIS K6031 standard in Hs (Shore hardness).
Q5
What is an attack angle of squeegee?
  • A:
  • It is an angle of squeegee fixed for printing.
Q6
What are the average quantities of ink squeezed out of a screen by the (attack angle of) squeegee stood and laid down
  • A:
  • The quantities of ink squeezed out increase with a squeegee stood and decreases with a squeegee laid down.
Q7
Considering the hardness of squeegee rubber alone, which is suitable for printing sharp lines, soft squeegee or hard one?
  • A:
  • Harder squeegee rubber is more suitable.
Q8
What is the elasticity of squeegee? (namely, flexibility)
  • A:
  • It is not hardness but pliability of squeegee rubber when force is applied to a flat squeegee at a certain angle.
    It is sensorily measured in general. Even if squeegees are made of the same urethane, the elasticity of squeegees, which affects the printing condition, vary according to the makers and kinds of squeegees
Q9
What is the solvent resistance of squeegee?
  • A:
  • It indicates to what extent squeegee rubber withstands a solvent etc. that ink contains or how rubber changes in quality.
    To measure it, soak a fragment of squeegee rubber in a solvent for about 24 hours and see corrosion of the rubber.
Q10
What is the grindability of squeegee?
  • A:
  • A flat type squeegee is ground for printing with the edge of squeegee rubber. The sharpness of the edge of squeegee rubber at grinding is called "grindability of squeegee".
Q11
What is the wear resistance of squeegee?
  • A:
  • As printing is performed repeatedly, the edge of squeegee rubber wears down. The durability of rubber in such cases is called wear resistance.


BASIC MESH SCREEN

Q1
What is the line size?
  • A :
  • It is the diameter of threads that make a gauze of a screen.
Q2
What is the gauze thickness?
  • A :
  • It is the thickness of threads that make a screen, in other words, thickness of gauze woven with the warp and weft. Therefore, it depends on the line size of the gauze. It normally is a value measured (at a point that the warp and weft cross) without tension.
Q3
What is the emulsion thickness?
  • A :
  • It is the thickness of a part plugged (from the underside of a gauze) so that ink is not squeezed out of a screen.
Q4
What is the total thickness?
  • A :
  • It is a value that the gauze thickness and emulsion thickness added together.
Q5
What is the number of meshes in a mesh screen?
  • A :
  • It is the number of meshes in 1 inch (25.4mm).(It indicates the texture density of a screen.)
Q6
What is an opening?
  • A :
  • This is a value that indicates the size of a mesh. It is the length of one side of a mesh.
Q7
What is the opening area?
  • A :
  • It is the ratio(%) of the area of meshes to a necessary area.
Q8
What is permeative volume?
  • A :
  • The volume of ink that goes through a gauze in actual printing. (Beware of the unit.)


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