Gradients for Screen Printing

[PrintedGear]

I created an image with a gradient. I sent it to the screen printer and he had difficulty creating the screen. First, the film printed with lines going through the image and then when he burned the screen chunks came off when he "blew it out". Is my resolution (ppi) on the gradient set too high?

 

[itchybug]

PG:

We may need a little more detailed information to help you.

1. What type of substrate are you printing on? T-shirt printing requirements are quite different from printing on plastics and metal...

2. The "lines" in the image, did they occur in a pattern? Were they perhaps bands rather than lines?

3. The resolution as in ppi (pixels per inch) is largely irrelevant to the screen making process, you should be talking about lpi (lines per inch), the number of halftone dots that appear per inch.

It disturbs me that your screen printer did not try to educate you a little bit...

As to the "blowing out", and chunks of emulsion coming off, that sounds like a poorly calibrated exposure unit or too much pressure when rinsing out the screen.

All in all, it sounds like you may want to seek out a more capable and/or knowledgeable screen printer. But first, answer the questions above so we know what we're looking at.

Bert

 

[PrintedGear]

Thanks for the reply...

1. They're printing on a clear film with an epson 2200. Their graphic designer walked out on them which ultimately put me in this bind.

2. They were vertical lines (top to bottom primarily) and I guess you could say it's a pattern. It goes all the way through the half-tone and is not as noticable on the spot color text part.

3. Are there different settings I should look for when it comes to screen printing when using AI?

I do have multiple screen printing vendors, but don't want to be trapped in a situation like this again. In the past I had provided the artwork (half tones and all) and their graphic designer fixed whatever I didn't do at no cost.

Are there any "screen printing with AI" books or videos I can consult in the future??

Thanks!!

 

[itchybug]

PG:

Substrate meaning what are you ultimately printing on, T-shirts or other things?

The banding issue may be resolved by rasterizing the gradient first. Also, there may be a problem if the printer is postscript 2 instead of postscript 3.

Bert

 

[apepp]

...have you tried to output with 'compatible gradient and gradient mesh printing'?

...this is in the output options of illustrator...

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Printing gradients, meshes, and color blends

Files with gradients, meshes, or color blends can be difficult for some printers to print smoothly (without discrete bands of color) or at all.

Follow these general guidelines to improve the printed results:
Use a blend that changes at least 50% between two or more process-color components.
Use shorter blends. The optimum length depends on the colors in your blend, but try to keep blends shorter than 7.5 inches.

Use lighter colors, or make dark blends short. Banding is most likely to occur between very dark colors and white.
Use an appropriate line screen that retains 256 levels of gray.

If you create a gradient between two spot colors, assign different screen angles to the spot colors when you create color separations. This is because if two spot colors have the same screen angle, they will overprint each other. If you’re not sure what the angles should be, consult your print shop.

Print to an output device that supports PostScript® Language Level 3 whenever possible.

If you have to print to an output device that supports Postscript Language Level 2, or when printing meshes that include transparency, you can choose to rasterize gradients and meshes during printing. As a result, Illustrator converts gradients and meshes from vector objects to JPEG images.

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To rasterize gradients and meshes during printing

Choose File > Print.

Select Graphics on the left side of the Print dialog box, and select Compatible Gradient And Gradient Mesh Printing.

Important: The Compatible Gradient And Gradient Mesh Printing option can slow printing on printers that don’t have problems with gradients, so only select this option if you experience printing problems.

Andrew

 

[apepp]

Setting the proper screen frequency for printing gradients, meshes, and blends

When printing your file, you may find that the resolution of your printer, when combined with the chosen screen frequency, allows fewer than 256 levels of gray.

A higher screen frequency decreases the levels of gray available to the printer. For example, if you are printing at a resolution of 2400 dpi, using a line screen higher than 150 results in fewer than 256 levels of gray.

The following table lists the maximum line-screen setting you can use with printers to maintain all 256 levels of gray:

Final Imagesetter Resolution Maximum Line Screen to Use
300 19
400 25
600 38
900 56
1000 63
1270 79
1446 90
1524 95
1693 106
2000 125
2400 150
2540 159
3000 188
3252 203
3600 225
4000 250