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Prepress & Screen Making



The new year is here again, and with it comes the usual list of resolutions. You know, the ones we try real hard to do for about three weeks, then give up? I don’t know if we just lack spirit and conviction, or if we’re just not disciplined enough to make it happen. But these predictions for the coming year should help motivate us.

First, we will feel continued competition from ever-improving digital-imaging technology. This will mostly be in the form of inkjet output in a variety of dye, pigment, and UV configurations. Run lengths will continue to shrink, necessitating faster setups and quicker changeovers on our part.

Second, inkjet output will be completely color managed, and the resulting consistent, predictable output will attract print buyers. Managed color will largely be the function of color software native to the operating system and RIP. To remain competitive, printers will have to do a better job of controlling variables and managing color.

Finally, printers will need to bring imagesetting in house to realize faster turnaround times and produce shorter runs. The good news is the cost to do this, even in large formats, is a fraction of what it was only a couple of years ago. The same inkjet technology giving us a run for our money is making it possible to image positives and provide color proofing for a very reasonable investment.

There are more competitive forces on the horizon, but these are certainly enough to get us going. With them in mind, I would like to offer ten resolutions to work toward during the next 12 months. All are achievable if we can overcome the inertia within our organizations.

1. Preflight effectively

Incoming files need to fly through preflighting. Long gone is the luxury of waiting a couple of days before opening the customer-supplied file only to discover it won’t work. Customers will continue to supply digital art, and you are responsible for the quality of the jobs you print from it. You must open, analyze, and correct or reject the art in a matter of hours, not days. The sooner you discover any problems, the faster you can react, and the more time you’ll have to fix any problems.

You need to establish a preflight plan, allocate personnel and workstations to do the file checking, and use software fast and powerful enough to get the job done immediately. You need to know what you want and how it is to be delivered. Then, you need to develop plans to handle the files that do not conform to those parameters.

2. Bring imagesetting in house

Shorter turnaround times and small run lengths make in-house imagesetting an absolute requirement. Whether you use film positives or direct-to-screen technology, you need a plan to control this critical area of your workflow. Recent advances on the litho computer-to-plate side will bring us better computer-to-screen solutions in the next couple of years, but for 2004, the least expensive technology for us is high-resolution inkjet.

The 720 x 1440- and 1440 x 2880-dpi output of the current generation of wide-format inkjets is sufficient to image very acceptable halftone positives. While still not quite as good as silver-based imagesetter film, inkjets are great for display work and conventional halftone output up to about 100 lines/in. Most printers still work at 65 lines/in. and below, so this is good news.

Even better news is the price. You can purchase a 40-50 in. wide inkjet, with RIP, for less than $10,000–in some cases several thousands less. Competitive prices may allow you to bring two or more wide-format inkjets in house for making film positives. The film and inks necessary to create waterproof, high-density film positives are available from many different suppliers. The cost is higher than silver-based film, but there are no chemicals or silver to recover.

3. Calibrate and manage color on the front end

I would like to see an entire color-managed workflow, but I’m realistic enough to accept that screen printers still are not ready for this. However, you can still manage color in the front end of the process. This includes handling incoming color profiles and creating your own scanner, monitor, and digital-proofing profiles.

The next step is linear film output, where you produce a predictable dot with your imagesetting equipment. It doesn’t matter if you use inkjet, thermal, conventional laser film, or projection output. Each requires a precise linear output of tone from 0-100%. Once you deliver film, it is up to the print-production department to ensure consistency.

4. Linearize output devices

Great output capability means nothing if your output is not linear or predictable. You’ll need measurement devices like strip readers and transmission densitometers. These essential control instruments allow you to calibrate any output device and monitor performance over time. Every high-end print shop, regardless of what type of printing it does, uses this approach.

Just because you spend a lot of money on an output device does not mean it will work as expected. If you want to do good work, you must linearize every imagesetter under your shop conditions. Having the right instruments, software, and knowledge are critical to your success.

5. Proof with inkjets

Digital proofing is now almost completely inkjet-based. The new generation of inkjet-proofing technology offers many advantages. Among them is true-halftone-screened output. You can now screen the proof with exactly the same halftone dot with which you’ll print. This gives the client a much better feel for how the final print will look.

The color gamut on six-, seven-, and eight-color inkjets is now almost equal to the gamut of the Pantone Matching System. This means the current generation of wide-format inkjets, with appropriate PostScript Level 3 RIP, can output matched spot color accurately. Additionally, you can screen the spot-color output just like you would the process-color output.

6. Create digital templates

Digital templates are the master layout sheets on which all imaged content is composed, and they are the critical underpinnings of a valid pin-registration system. By working from the same established layouts each and every time, you create consistency and speed the delivery of art to press.

The templates are best prepared in page-layout programs like Quark XPress and Adobe InDesign. These programs are optimized specifically to accommodate the embedding of many complex images, both raster and vector files. They also accommodate complex clipping paths. You can produce templates in vector programs like Adobe Illustrator, Macromedia Freehand, and CorelDRAW; however, you may experience problems during output when using vector programs. In short, layout programs are much more efficient and effective than vector-based software.

7. Produce go/no-go test images

Include go/no-go test images along with your digital templates. These are images that will help the screenmaking department check the imaged screen before it heads to the production floor. The idea is to establish quick-check areas on the screen that you can verify before the screen leaves the department. These test areas are set to image the finest printable detail your shop can hold. If the areas image properly, you know the screen is within printable tolerance.

Here’s a suggestion. Establish the width of the stroke on your registration target so it equals the width of the smallest halftone dot you can consistently print. If this is a 10% 65 line/in. dot, make the width of the target crosshair equal to the diameter of a 10% dot. If it does not washout, you know you are losing information. By having the same targets all the time, screen makers become accustomed to that level of detail. The results are greatly improved halftone screens and less downtime on press from replacing stencils that don’t print.

8. Implement pin registration

The need for speed grows greater every year. In our case, speed means faster setups and changeovers. We are paid to print. Since the run lengths continue to shrink, long setups prevent us from recovering downtime costs. The answer is a changeover that lasts seconds, not hours. The two most important elements of a fast changeover are predictable pin registration and mesh tension greater than 20 N/cm.

Most printers have toyed with pin registration, only to give up due to unpredictable results and inconsistent performance. Achieving the goal of accurate pin registration on demand takes time, but the results are amazing. Reduction in per-color setup to 15-30 sec is possible. If you reduce changeover time, your overall productivity will take a big jump up. More importantly, you can realize economic feasibility in smaller jobs that would otherwise be highly unprofitable.

9. Focus on mesh tension

The success of color management, pin registration, and higher productivity all depend on good mesh tension at a level you can consistently repeat. Mesh tension above 20 N/cm is critical for high productivity, and I usually recommend 24 N/cm. Anything below 20 N/cm and the overall system becomes unmanageable and unpredictable. Press operators will continuously adjust the press looking for that sweet spot where everything works. It is elusive and continually changing. As the tension goes up, the variation goes down.

Your productivity will increase along with the screen tension, but the higher you go, the more careful you must be to avoid ripping the screen. I suggest you start with 20 N/cm until you can handle screens without problems. Your work and productivity will improve, even at entry-level tensions. Begin inching tension up over a period of several months. When screens start blowing at a rate higher than normal, you’ll know you’ve exceeded the right amount of tension for your operation.

10. Control dust and dirt

Dust and dirt do more than slow down the screenmaking process. They also create hidden time bombs in the form of pinholes that appear during the run. The screen seems fine when it arrives on press, but quickly begins to degrade under the friction and abrasion of production. The press operators find themselves frustrated and robbed of productivity as they continually stop to tape the pinholes that continuously appear.

Do yourself a big favor and paint the floor of your screenmaking area with a high-gloss epoxy. It costs about $75.00 per gallon and covers approximately 300 sq ft. Alternatively, a high-grade industrial vinyl floor tile will work. Both allow for frequent and repeated mopping. A small amount of effort here pays big dividends on press.

High resolutions

If you make good on these ten prepress resolutions during the next year, you’ll become a more competitive printer. It would not be too bold to say your future may depend on how effective you are at implementing these resolutions. As the economy improves and conservative buyers begin to spend again, they will reward the companies that can deliver with competitive prices, excellent service, and outstanding products. If you can’t do this, there are some very hungry sharks lurking not so patiently for their chance to show they can.


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