|Home | Site Map | Buyer's Guide Search|
|Event Calendar||Article Archive||Message Boards||Classifieds||Product Showcases||News||Advertise||Search||Join Now|
Screen or Digital Which Method to Choose...An Imaging Technology Decision
By By Dan Marx, SGIA V.P. of Markets & Technologies
Here it comes, like a rocket from your sales department. It’s a brand new job, all set for your company to print and deliver. The nature of the job allows you the opportunity to run it using either your screen printing presses or your digital presses, and the customer just wants it done. How do you choose which process to use, and what are the factors you must consider to ensure you make the best, most profitable choice for you company?
Many say the choice is all about run length, and if you have spent any time talking to wide-format inkjet sales representatives, you’ve surely noticed that run-length comparisons — that eternal quest to find the “sweet spot” between screen printing and digital output — must be very important. So, let’s deal with the issue of numbers, then move on to a discussion that allows us a bit more consideration and complexity.
The sweet spot is the point where the speed of screen printed output surpasses the speed of digital output. Screen printing is a complex process, and many steps are required before the squeegee can push ink through mesh, making the first acceptable impression of a print run. Because of this, screen is slow to start, and a great deal of time can pass between the time you receive the customer’s files and the time you’re ready to print. However, once the job is ready, a screen press running full-bore can do many impressions per hour.
Conversely, digital is quick to start, and derives strong benefit from a relatively simple process. Therefore, once you have received your customer’s files, you need only preflight the job before printing can begin. Once the job begins, however, inkjet is a relatively slow imaging process. So even though digital printing can start almost immediately, screen will catch up in relatively short order. Most people I’ve talked to about a quantified “digital vs. screen” sweet spot say it’s currently somewhere between 100 and 150 printed pieces.
Great! You have your rule of thumb, and you can go with it, right? Well, no, because easy-to-calculate, generalized figures such as the one presented above rarely reflect the real world of production. Consider that the number featured above assumes a few important factors: The first is the assumption the job can be done using both processes, which we’ll discuss later. Also, the speed of screen presses is highly variable. Instead of taking someone else’s word for it, do some research, and then calculate your own speed figure based on the equipment used in your facility.
Lastly, consider the efficiency of your screen activities. Depending on factors such as training, quality standards, efficiency and production management skills, the amount of time it takes a given company to get a job up and running on a screen press is also highly variable.
Another major factor affecting run-length calculations is that digital imaging equipment continues to get faster. In fact, as wider arrays of print heads become increasingly common, the figure mentioned earlier could double or triple. Digital imaging equipment is constantly under development, and should be considered a “moving target” as it relates to run length calculations. Conversely, the continued refinement and automation of screen printing has led to higher efficiency and sharp process improvement, which has served to make screen competitive at increasingly shorter run lengths.
When the Choice is Yours
The first and most basic question to ask is what will you print? What will the end product be? Based on the equipment and ink technologies you’re using with each process, are you confident that each process will work equally well to create the desired end product? Surely, an inkjet device running aqueous-based inks and a screen press running heavy solvent are both capable of creating acceptable prints, but would not be considered equals in relation to durability and substrate/media compatibility.
Both process screen printing and inkjet digital printing have the CMYK color set in common, and in a perfect world, the gamut and capabilities of these color sets would be equal as well. While color management is always a concern, regardless of the process you are utilizing, it is important to consider that for most shops critical color management is easier on the digital side.
The complexity of the screen printing process brings with it many opportunities — among them the making of positives, emulsion coating, curing, squeegee pressure — to send color outside any customer’s acceptable limits. So, if color is highly critical and you don’t have a significant degree of confidence in your four-color process screen work, digital may be the ticket.
As a direct tie-in with color, print quality is also a factor. A significant amount of today’s retail display work comes with customer expectations of perfect color and photographic or near-photographic quality. Once again, the complexity of the screen printing process comes into consideration. Companies that have established a firm control of screen printing and can deliver the high-quality work expected by the client, have a choice. Those who can’t control the process don’t.
If all things are equal, meaning your facility can produce and deliver the project successfully using either screen printing or digital, you have one very advantageous decision to make, and it will be based on cost issues. If your facility has reliable and sophisticated job cost accounting, then you should determine which process is most economical for your company, and which will allow your company to earn the best profit margin. Do your math, and then make your choice.
Depending on the run lengths specified, turnaround time in both processes can be a major consideration, especially considering the “need-it-yesterday” expectations from most of today’s customers. For many facilities, short turnaround may also mean using a digital solution — up to a certain point — and then the screen printing process if your company is able to manage the job quickly enough. As digital solutions increase in speed, print deadlines will continue to become tighter and tighter.
Though opportunities for this type of solution may be infrequent, a number of companies have integrated both screen and digital processes into certain jobs. By using both processes, these companies are able to take full advantage of the unique strengths and capabilities of both processes. For instance, a job may utilize the high-volume production aspects of screen, then use digital to customize the prints for a variety of purposes.
When Job Defines the Process
This first factor, easy but certainly worth mentioning, is to decide which process is available. If your screen or digital presses are bogged down with multiple jobs or a long run, then you may be forced to use the other. It’s simple, but true.
Performance considerations are highly important, not only for the process used to create a job, but also for the ink system used, as well as the substrate upon which the image is printed. This is because most end products are designed with a specific length of life in mind — a life that automatically specifies a certain process. These products include those that are exposed to harsh conditions. A stop sign is a good example: It must not fade; it will be exposed to full sunlight, and undergo harsh weather conditions; and it is expected to last many years before being replaced. Because of these extreme performance requirements, heavy-solvent screen printing is the default process.
The screen printing process is unique in the graphic arts industry because the process allows for a relatively thick ink layer, which provides a high degree of color opacity. Because of this reality, some jobs with specific color density requirements, such as backlit displays, may only work using the screen process. Digital printing’s relatively thin ink layer can lead to opacity challenges, especially on dark substrates, where a background application of white ink must precede the application of process color.
The screen process also allows for easy color use outside of the CMYK color set. The use of specific spot colors, out-of-gamut PMS colors, fluorescents, metallics and other special effects give screen printing a unique edge for certain jobs. While spot colors can be used on certain systems in the inkjet industry, there are few available units. Also, the lack of an in-house “color kitchen” for inkjet inks leaves digital processes beholden to ink manufacturers and suppliers, while most screen facilities are able to mix specialty colors in-house as needed.
Certain jobs that come into your facility may dictate a process based solely on print quality. When the required job resolution is high, you may have no choice but to run the job on your digital press at the highest possible resolution. When doing so, it is important to remember high-resolution printing is much slower than printing done at a standard production-grade resolution, and to allow additional time to complete the job.
Sometimes, choosing your process requires looking toward finishing, which occurs at the back end of your process, because not all prints for all processes can be finished equally. Consider what must be done before the print is transformed into the finished product. For instance, only a small number of digital solutions allow for successful vacuum forming of a printed product. This is a case where finishing requirements would dictate the imaging process, as vacuum forming has been performed successfully for decades in screen printed products.
In other conditions, the choice between processes is not yours to make because of firmly established OEM, manufacturer or military specifications. With these jobs, your choice is to do the work as specified even if the process you have to use is not the most effective or most economical for you or the client. But you can try to work with the client to rewrite or update the requirements for future jobs.
What Matters and What Doesn’t
In a recent discussion among representatives of multi-process facilities, it was agreed that while the printing industry pays a great deal of attention to the possibilities, liabilities and opportunities of one process or another, the customer generally is not interested in the discussion at all. In fact, what the customer wants from companies such as yours is a finished product that meets the expected quantity, quality and durability within budget and within deadline. If your company can fulfill these needs effectively and reliably, while making an acceptable profit, then your company has successfully managed the best of what multiple processes — screen, digital or otherwise — have to offer.
This article appeared in the SGIA Journal, 2nd Quarter 2007 Issue and is reprinted with permission. Copyright 2007 Specialty Graphic Imaging Association (www.sgia.org). All Rights Reserved.
© Copyright 1999-2013, All Rights Reserved.