screen printing > General Screen Printing

New to sim process? This is for you.

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Dottonedan:
I typed much of this up for a customer that is new to printing sim process and thought that it could be helpful to other people just starting out. I've tried to generalize as best I can see. It may not be 100% accurate, but this is a good start. Feel free to chime in or correct. That's what we are here for.




Print the films out at 55lpi-65lpi. For sim process and for sim process pocket prints I really prefer 65lpi-75lpi and 305-355 mesh, but if this is your first go at it, a 55 and 305 mesh will be better for you.

230 on base, and 305 mesh on top colors. Flash the base, print the rest wet on wet.

I suggest using hard (70-90) or triple duro (70-90-70) and new or sharp squeegees, print at near vertical angle. The inertia/momentum of the print stroke will add 3-5 degrees alone. We want to start out at about 3-5 degrees and with the stroke momentum, end up about a 6-10 degrees. Near vertical angle, holds more detail by cutting the ink onto the shirt rather than smudging it on with the angle out further. You can adjust this as you go, but these are all starting points. Start at near vertical.

Off contact on cotton tees should be 1/16" for mesh that has lower than 25n. This gets to be a band aid for lower tensioned screens. Try to keep them at optimum.
Lower off contact to 1/32" if all of your mesh tension is at or higher than 25n. (Lower is better. Tighter reg.

In general, most want to be between 35lb and 45lb of pressure.
Start out at a print stroke in mid speed range. 6 on an M&R.

The three most important things in my opinion about sim process;

1, WHITE BASE
The base is intended to support the top colors. It's white, but when printed on high mesh like a 230 mesh, it doesn't show up as super bright. People tend to over print this base thinking it needs to be super bright white. It doesn't. If it shows up as a light grey, that's a good (base) white for sim process.

12, INKS
The top colors (for sim process) will sit on top of the base white...and be very close to it's true color where it sits on white. As it rolls over into shirt color...it will darken. A gold will become dark gold or brown. It needs to do this. Therefore, you must use semi thin inks. Typically any ink type that is designed to go through a 305 mesh is a sim process ink. If you have very opaque inks, (what most solid spot color logo type printing is done with), you will need to add in 10-20% curable reducer, also known as soft hand, Finesse, or even just simple CLEAR base. The clear base will thin down the ink and this will work, but the more you add, the more you take away from the integrity of the ink.

3, Screens
To me, the most important part of a good sim process is the screen and not just good seps. I can't do anything with great seps and great inks and great printing techniques...if I don't have great screens, but you can work around the rest of sep issues, ink issues, and printing techniques.

Most people just starting out from solid logo printing, and going into sim process find that the need to make a lot of changes. Things that they never noticed before, because of the type of printing you were doing. Like emulsion thickness and exposure time. More than likely, your emulsion coating process will need to change (in order to hold the smallest detail of a 3-5 dot or very thin line work. Most people when starting out, will see that they are not holding the detail they are looking for, so they then do another screen and decrease the exposure time. This helps hold more detail, but is a band aid and not the proper procedure because if you do this and your order is for 50 shirts, you may not have any issues and think this is the answer. If the order is for 500 or 1000 shirts, your screens may break down and will for sure, at 3000 or 5000 shirts or more. It's not properly cured and durable. So the real answer, is to properly coat for that particular higher mesh (thinner)...and to then do an exposure calculation test. Most like the Stouffers 21 step test and look for a hard #7. On a DTS and no glass exposure, you would be looking for a step #6.

A common coating procedure for high mesh (200 mesh and above) is a 1:1. You can do 1:2 but the goal is to get a good thickness (that holds the detail (and is a proper cure) at the same time. It's not really how you get there.

You can add or reduce thickness by slowing or speeding up the coat process, (too fast leaves air in emulsion). You can also switch from round edge, to a sharp edge.  Sharp often puts too little emulsion down. Regardless of the method, your goal is to get that stencil to be thinner in general, than your normal coating. Then test for proper exposure...and proper detail. (You may not get a 3% dot in a 65 line screen on a 305 mesh, but you will get MORE than before and most of them.

Feel free to add comments and preferences.

lancasterprinthouse:
Thanks for this. I’ve manually printed a few (some of which you sep’d) and we got our first auto installed last week. We have a reprint coming up and this info is helpful as a starting point. Particularly the squeegee angles as I would have tried to run it at 10 degrees or more.


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easyrider1340:
Thank you Dan!


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ABuffington:
Great stuff Dan.  Sim Process is a less is more type of print approach.  With a higher mesh count in 350 range, it helps to recognize that it takes several shirts for the colors to build up on the bottom of the screens in the print.  Too often printers look at the first registration print and want to see more ink color and up the squeegee pressure.  It can take 8-10 prints for a 350 mesh to build up ink on the following screens and achieve the amount of color intensity wanted.  If the first registration print is adjusted with too much squeegee pressure to get color, it can cause unwanted dot gain and kill very fine negative dots of shirt color in the 70%-95% range.  The higher the line count the easier this it is to collapse fine negative dots of shirt color. This is a common issue on the base plate print as well.  S mesh does help avoid using too much squeegee pressure and helps print the tonals as close to the film image as possible. 

Linearization is another area that helps sim process.  20% dot gain to film is possible with ink jet, then another 10-20% on print can lose the important tones above 60% if the pre press imagery is not controlled to compensate for dot gain.

SEPSINK:
This is awesome, Dan. Well done!

It can be a real brain bender explaining all of this to someone who is new to the process.

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