A Figure of Screen With Squeegee
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| Mechanisms of Screen Printing ©Textile Pad |
Description of the Figure
Here,
F = Downward force/ hydrodynamic pressure
b = Base length of pressure zone
V = Speed of movement of the squeegee
θ = Squeegee angle
r = Radius of the pore
l = Length of the hole
η = The viscosity of the print paste.
Fundamental Characteristics of Screen Printing
- In the screen printing process, hydrodynamic pressure is built up in the print paste between the squeegee and screen surface through which the paste is passed. Here, hydrodynamic pressure appears to be proportional to the squeegee angle. So F ∝ θ; more pressure creates a larger squeegee angle.
- The hydrodynamic pressure is inversely proportional to the radius of the screen pore. So, F ∝ (1/r).
- Hydrodynamic pressure is directly proportional to the viscosity of the paste. So, F ∝ η.
- The base length of the pressure zone also plays a role. More base length of the pressure zone requires more pressure. So, F ∝ b.
- The hydrodynamic pressure is directly proportional to the speed of movement of the squeegee. So F ∝ v. More pressure will increase the speed of movement.
- A higher length of hole required more pressure. So F ∝ l.
The Flow of Paste Depending Factors
- The flow of paste is directly proportional to the hydrodynamic pressure. So Q ∝ F.
- The flow of print paste is inversely proportional to the viscosity of the print paste. Less viscosity causes more flow of print paste. So, Q ∝ (1/η).
- The flow of paste is proportional to the screen pore radius. So, Q ∝ r.
- A higher length of the hole of the screen causes a lesser flow of print paste. So, Q ∝ (1/l).
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Printing