Screen Printing

[Brian Robison]

OK, I know nothing about screen printing but!!!!?
Why can't a laser be used to make the screens?

[Doug Griffith]

I can think of a few quick reasons:

1) "silk" screen mesh is not metal and would burn right through.

2) flm positives used to burn the screens is a clear film and would burn right through.

3) the diameter of the laser dot is significantly larger than the screen mesh.

Cheers,
Doug

[Mike Null]

Brian

You might want to have a look at this site. Some of these methods are primitive and photo emulsion is the one to use for professional results.

http://www.reuels.com/reuels/Silk_Screen_Printing_Instructions.html#PSM

[David H. Mitchell]

Years ago, when we used rubylith for stencils, a laser would have been great.
As Mike pointed out, today we use a photopolymer emulsion to make a screen. A laser back then would have saved a lot of time.



Dave

[Dan Hintz]

3) the diameter of the laser dot is significantly larger than the screen mesh.
They screen print at dot sizes smaller than 1.5 mils? I was not aware of that...

[Doug Griffith]

They screen print at dot sizes smaller than 1.5 mils? I was not aware of that...

If I remember correctly, my screen print system (for plastic sheet) used between 240 - 280 mesh. This link shows some mesh counts and equivalent mesh openings.

Cheers,
Doug

[Dan Hintz]

This link shows some mesh counts and equivalent mesh openings.
Blond moment? :p

[Doug Griffith]

Aw, cheese and rice. Here it is:
http://www.ryanrss.com/2MeshDisplay.html

125 mesh equates to around .005"
240 mesh equates to around .002"

I think the average laser dot size is .005"

[Dan Hintz]

Aw, cheese and rice. Here it is:
http://www.ryanrss.com/2MeshDisplay.html

125 mesh equates to around .005"
240 mesh equates to around .002"

I think the average laser dot size is .005"
For a 2" lens, that's correct. But add in an HPDFO lens and you're in the 280 mesh area... at the very least, a 1.5" optic is approaching the 240 mesh area.

[Doug Griffith]

Lets just say we have some type of film capable of being processed into a film positive with a laser. Or even screen mesh and emulsion that works with a laser. Creating halftones with uniform rosettes and no moire is difficult to achieve even with high resolution digital printers printing variable sized or stochastic dots. Lasers "print" with fixed dot sizes and a linear pattern. It would be next to impossible to get good results.

[Mitchell Andrus]

Lets just say we have some type of film capable of being processed into a film positive with a laser. Or even screen mesh and emulsion that works with a laser. Creating halftones with uniform rosettes and no moire is difficult to achieve even with high resolution digital printers printing variable sized or stochastic dots. Lasers "print" with fixed dot sizes and a linear pattern. It would be next to impossible to get good results.

Agreed. My Dad's been a screen printer for 50+ years, We spend a good amount of time and the results are NOTHING like the standard photographic process.

We could cut and apply the stencils and shoot the screen. But the lines were nowhere near smooth enough for any use but printing on the sides of 55 gallon drums.

Exposing film with lasers has been done, and we did get some good results, (green lights at night so we could see) but halftone test were a bust even at large resolution. Had a blast trying though.
.