Printing for silk-screenings - need some help please

[brookemegg]

We have started screen-printing tote bags at our work. We've always sold the bags and outsourced the printing. Now, we're doing the printing. We've been doing ok so far using an Epson 1280 to print the transparencies. We are also actually burning and blowing out the screens ourselves.

We had a customer ask us to try to print a 3-color piece of artwork. That's not a problem, we have the capability to do so.

What I'm stumped on though is that the artwork has spot color percentages in it. For example, it has 3 colors - a red, black and gold. The red and gold have at least 3 percentages, ranging from 30% to 100%. I started off having no idea how to print this on a transparency.

After a couple days of internet research, I've concluded that I either need a Post Script printer to be able to print this or a RIP program to convert it to half-tones for a non PostScript Printer. Aside from the Epson 1280, I also have an HP2200d which is a laser printer capable of PostScript.

When I try to print it though, only the top part of the artwork prints, nothing else at all. It will even jsut run the transparency through and not print on it. I'm lost as to what to do. I've tried printing on the HP and I've downloaded a free trial of AccuRip for the Epson.

I have no idea about how to set-up this file so that it all prints. I've read about separations, trappings, setting it up to print correctly, etc and I'm just lost on all of that. Obviously I don't do much in Illustrator. I usually only work in black and white to set up artwork/logos to be hot-stamped or ink-printed on bags and boxes.

Any help would be much appreciated. I work for my family business and my Dad is pressuring to be able to do this so he can tell the customer yes.

I'd be grateful for any help.

Here are the 4 files - the Original is the art with all 3 colors still together. The individual color named ones have just that color, changed to black, to print on a transparency. I didn't know if I have to do it separate like that or if either Acrobat or Illustrator will separate them to different transparencies for me.

www.tandjadventures.com/images/CountryOriginal.eps
www.tandjadventures.com/images/CountryGold.eps
www.tandjadventures.com/images/CountryBlack.eps
www.tandjadventures.com/images/CountryRed.eps

Thank you!

[warking@mac.com]

Ink jets stink for this kind of work.

Please look into a Xante Screenwriter

http://www.xante.com/support/cswne/

I used this printer at MV Sports as my primary output onto Vellum for screen printing.

Film is better, but Vellum covers a great deal of what you'll be doing.

Thanks
Todd

[lilypad]

First you definitely need an output device that will reproduce spot screens/tints in a dot pattern.

Most inkjet printers reproduce images using a process called FM/stochastic screening, which uses almost randomly placed droplets of ink to create an image.

A laser printer such as the Xante that Todd mentioned reproduces spot color percentages as a dot pattern, and each separations is nice and black so burning your screen is easier.

You also need to be able to match your dot pattern density output to the silk screen that you intend to use. Just like your silk screen, the dot pattern has a value that defines it called "line screen" or "LPI." 85 LPI means that there are 85 lines of dots per inch. There are certain tried and true ratios for silk screen density to LPI output, I just don't have those at my fingertips. If I am not mistaken a 2:1 ratio works (ex: if you have a 60 count mesh, then you can print separations at 30 LPI).

I ran separations of you "original" file and they seem to look good. The only suggestions that I can make about the file are; A) most screen printers I know do not use overprinting for close registration, so you will want to turn OFF all overprinting; and B) if you intend to use your registration marks, you will want to assign them the color "registration". However, you could also use the automated printer marks the Illustrator produces when requested.

- jon

[TORCH511]

The 2:1 ratio works to a point. We have tried everything to be able to be able to reliable and consistantly increase our LPI capabilities. we have gotten it up to 105 LPI with minimal to no effects and that is slightly higher than any literature on the subject says we should get. There seems to be a balance at some point where the size of the dot just can't get any smaller, regardless how many threads it holds. The other issue is % range, but that is a factor when doing gradients, and the example here does not have those.

There are sevices out there that can make the films for you. There are quite a few and probably one local to you. Probably a good idea in this case instead of investing in a printer/imager and RIP software.

They can probably also help with setting up the artwork for you, or will do so for a nominal charge.

[Paths]

If you don't have access to a postscript printer - you can do the halftones yourself by converting each separation document into a bitmap in Photoshop. During the conversion to bitmap mode, you set the output ppi, halftone type, lpi and angle. The dot sizes will be determined by the value of black that each separation provides.

For a 305 mesh (recommended) - I use these settings:
output resolution 300 ppi
55 lpi
45 degree angle
elipse
(this is for a manual press)

I separate out the 100% values ahead of time - so those parts will not get pitted during the halftone, and then combined them with the same colour halftone before printing the separations (on a regular inkject printer onto velum). I also do any trapping or choking first.

Hope that helps :D

[Paths]

A good thing to do first - whether you are using an automated press, manual press, postscript printer or doing your own halftones is:

Make a document with the grayscale on it - listing the tonal values (I made boxes filled with black in values 10% to 90%, with 10% increments - including the labels above each).

Do this for your ideal lpi (ours is 45 lpi - on a manual press with 305 mesh) and for one or two more above and below (I also did 55 lpi - which is our maximum - and 35 lpi to see the more obvious dots).

Burn the scales on one screen and then make two garments:
Black garment with white ink and White garment with black ink.

This will show you the tolerance you have to work with. It showed us that we get our best tonal range at 45 lpi and that most values above 70% go almost solid coverage (because of dot gain / heavy hand) and that values of 10% or less will not hold (are patchy) except on the lowest lpi (35 lpi).

We regularily use these samples to determine values to use when setting up artwork - since we can reasonable predict outcome now.

You could also include text or strokes at different point sizes for a test or with this test - to see how small you can reasonable go as well.

[TORCH511]

Paths, what you just described is what I have come to know as Fingerprinting, or footprinting a press. We use a template like what you described, though far more detailed for both our screen and flexograpic presses, and we have a schedule where we test all our presses too. It is an excellent idea to do just that and understand what you are capable of printing, and adjust artwork accordingly. I spent a good month with the old printroom lead and the best printer we had trying to boost our capablities... could probably write a book on it by now.

The hardest part of the whole process was trying to convince the engineering department and Quality Control that when we make films for printing, halftone edges may appear very jagged on film, but when printed look much different.

[brookemegg]

Thanks for the replies everyone. I still have not had a chance to even work on this problem yet. Hopefully that will happen this weekend.

I'm about to print this thread out and play around. Thank you!!

[Paths]

Paths, what you just described is what I have come to know as Fingerprinting, or footprinting a press. We use a template like what you described, though far more detailed for both our screen and flexograpic presses, and we have a schedule where we test all our presses too. It is an excellent idea to do just that and understand what you are capable of printing, and adjust artwork accordingly. I spent a good month with the old printroom lead and the best printer we had trying to boost our capablities... could probably write a book on it by now.

The hardest part of the whole process was trying to convince the engineering department and Quality Control that when we make films for printing, halftone edges may appear very jagged on film, but when printed look much different.

thanks for the info and in particular the last bit about the halftone edges :D - the studio tells me I'm too fussy - now I know they are right ! :rolleyes:

[Tom Morrison]

Canvas tote bags have a coarse weave, a 30 lpi halftone may work
better than 55 lpi. Screen printing results in dot gain, so a 30%
halftone will look like a 50% halftone; this effect may be amplified
on coarse fabrics. If you want a 10% halftone also use big dots, 30 lpi
because at 55 lpi the dots are so small they may close up when the
screen is expose. Conversely, an 80% halftone may fill in to 100%
when printed ( remember dot gain) so make it 65%. If you have
3 halftone percentages such as 30%, 40% and 50%, try 20%, 35% and
50% because the closer percentages will tend to look the same and
you'll have a print that looks more like it's supposed to by spacing the
percentages more. The print world standards assume offset printing.
Screen printers have to adjust by trial and error. I hope these hints
will help you think about how to adust : they are not rules, just
suggestions. Good luck.

[simon162]

We have started screen-printing tote bags at our work. We've always sold the bags and outsourced the printing. Now, we're doing the printing. We've been doing ok so far using an Epson 1280 to print the transparencies. We are also actually burning and blowing out the screens ourselves.

We had a customer ask us to try to print a 3-color piece of artwork. That's not a problem, we have the capability to do so.

What I'm stumped on though is that the artwork has spot color percentages in it. For example, it has 3 colors - a red, black and gold. The red and gold have at least 3 percentages, ranging from 30% to 100%. I started off having no idea how to print this on a transparency.

After a couple days of internet research, I've concluded that I either need a Post Script printer to be able to print this or a RIP program to convert it to half-tones for a non PostScript Printer. Aside from the Epson 1280, I also have an HP2200d which is a laser printer capable of PostScript.

When I try to print it though, only the top part of the artwork prints, nothing else at all. It will even jsut run the transparency through and not print on it. I'm lost as to what to do. I've tried printing on the HP and I've downloaded a free trial of AccuRip for the Epson.

I have no idea about how to set-up this file so that it all prints. I've read about separations, trappings, setting it up to print correctly, etc and I'm just lost on all of that. Obviously I don't do much in Illustrator. I usually only work in black and white to set up artwork/logos to be hot-stamped or ink-printed on bags and boxes.

Any help would be much appreciated. I work for my family business and my Dad is pressuring to be able to do this so he can tell the customer yes.

I'd be grateful for any help.

Here are the 4 files - the Original is the art with all 3 colors still together. The individual color named ones have just that color, changed to black, to print on a transparency. I didn't know if I have to do it separate like that or if either Acrobat or Illustrator will separate them to different transparencies for me.

www.tandjadventures.com/images/CountryOriginal.eps
www.tandjadventures.com/images/CountryGold.eps
www.tandjadventures.com/images/CountryBlack.eps
www.tandjadventures.com/images/CountryRed.eps

Thank you!

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