The Benefits of Screenroom Automation
There are some tasks for which a machine may truly be the best man for the job.
In The Automation Issue, we present a collection of expert essays on an important topic in the industry today. Here, Johnny Shell discusses automation in the screenroom.
Automation: It’s happening anywhere a machine or robot can be inserted into a manufacturing process to perform a specific task. It’s being embraced across most industries, around the world, because it increases productivity and output, simplifies workers' jobs, and adds consistency, repeatability, and quality assurance by virtually eliminating errors.
Even screen printers are getting in on the act. Many are automating their screen making operations, adding a range of technologically advanced equipment to counter against competitors, increasingly tight profit margins, and pressure from alternative print technologies. Printers enjoy a wide range of options today for automating virtually the entire screen making process from stretching to reclaiming.
Automatic Frame Cleaning
Before stretching even begins, today’s screen making department can utilize automatic frame cleaning machines that fully strip the gluing surface of mesh and adhesive to ensure optimal bonding between the mesh and the frame. These systems use either abrasive pads or high-pressure water that is jetted at the frame surface at up to 21,000 psi. Systems that use abrasive pads often include a ventilation system to draw dust or fumes away, keeping the work environment clean and the operator safe. For high-volume shops that use static frames and frequently change out the mesh, automatic frame cleaning systems are a good automation choice.
Many small shops order pre-stretched frames from a supplier, but there’s nothing like being in control of your screens (especially the mesh tension) from the start. Manufacturers of stretching systems offer advanced options that automate virtually every step of the process. The operator programs the desired stretching parameters via touch-screen interface and can call up stored job settings whenever needed. Once the mesh is secured in the clamps, the stretcher automatically brings it to the precise tension specified in the program. Some stretchers include a perforated table with movable angular stops so that frames can be set at a specific angle to the mesh before stretching begins. On some units, tension is automatically measured in both warp and weft directions via a multifunctional head that may also include automatic gluing and LED curing. Some manufacturers offer a standalone gluing and curing system that can be added to existing stretching systems. The operator merely has to insert the frames and mesh, secure the mesh in the clamps, press “Start,” and cut the frames out at the end.
Coating machines are one of the best investments for any shop looking to automate. Their repeatability is +/- 1 micron, giving you the ability to achieve a consistent stencil thickness every time, which makes exposure calculation much more predictable and repeatable. You can produce the same stencil thickness across all mesh counts you use, further streamlining the exposure process.
Of course, realizing the full benefits of a coating machine depends on many factors, including the consistency of the mesh tension for a given mesh count and thread diameter from a specific manufacturer; emulsion viscosity and fill volume in the coating troughs; and exposure light source. If those remain consistent for a given mesh count and thread diameter, then automatic coating is a very beneficial way to automate your workflow.
Most automatic coaters allow the operator to choose from a variety of settings, including independent control of the number of passes on each side of the mesh, the speed the troughs move during coating, the amount of pressure exerted at the trough edge against the mesh, and the dwell time (the amount of time the machine pauses after the troughs have been tilted to allow the emulsion to flow to the mesh before coating begins). Some manufacturers offer several coating edge radiuses to give the operator further control over stencil thickness. Many automatic coaters can store job settings to further ensure quality control for shops that use several mesh counts. Instead of a faded, torn piece of paper taped to the wall with the coating procedure for each mesh, they’re stored in the machine’s memory.
Besides their coating consistency, many automatic coaters allow you to coat two or more small- to medium-format screens at once. You’ve just improved productivity by at least 100 percent; keep in mind that the operator who simply loads the screens into the machine, selects the desired program, and pushes “Start” can walk away to handle other tasks. The machine doesn’t suffer the variable conditions that make it virtually impossible to get consistent stencils manually. Workers may get tired toward the end of the day, resulting in variances between screens coated at the beginning and end of a shift. If multiple workers coat screens in your shop, there’s a good chance that the stencil thickness on screens coated by one employee won’t be the same as those done by another.
Computer-to-Screen (CTS) Imaging
Significant advancements have been made to CTS systems over the last five years and the technology is getting lots of attention. One of the immediate advantages with a CTS system is the streamlined workflow. There’s no finding, handling, or filing film; no measuring, positioning, or taping of film to the screen. (That’s right – no tape!) Registration is handled in the art department when the file is generated instead of on press. Art files are accessed (and possibly stored) on the CTS workstation, which is usually networked so that files can be sent effortlessly from the art department to the screen making area. The screen maker merely has to open the file and click “Print.” CTS technology will improve your productivity and yield, reduce waste and press downtime, and increase your quality. Plus, you’ll have some extra shop floor space because you won’t need an area to keep (or misfile) film.
CTS systems come in two flavors: masked (ink/wax) and maskless (light). Masked systems use inkjet technology to print either water-based ink or wax onto a coated screen rather than a piece of film. Their maximum resolution is 1200 dpi, which is capable of handling halftones up to 85 lines per inch. Once printed, the screen is exposed by placing it in front of an acceptable light source (such as metal halide or LED). There’s no need for glass that must be cleaned or time spent waiting for vacuum to be drawn because there isn’t a piece of film that must be sucked into close contact with the coated screen. Remember, time is money.
Most masked CTS units include a pre-registration system that place the screens at the same location inside the unit every time. As long as your art department is registering the art properly in the files, screen-to-screen registration will be nearly perfect. This leads to huge time savings during press setup. Some manufacturers have married CTS technology with onboard LED exposure, further streamlining the workflow by combining stencil imaging and exposure into one step.
CTS systems are one of the best investments a shop can make.
Print speed depends on the number of inkjet heads in the machine, so take this into account when considering a purchase. Speeds are constantly improving, but currently a water-based masked system can print a 14 x 16-inch image in under 60 seconds. You’ll also want to consider your annual film and labor costs associated with filing, finding, taping, positioning, and measuring film, because all that essentially goes away once you put a CTS system in place.
Maskless systems use light to expose the negative areas of the stencil, leaving the positive areas unexposed, to be washed out during stencil development. The units use either LED or DMD (digital micromirror device) technology; both have a maximum resolution of 2540 dpi. So, why consider a maskless unit? They really only have one consumable: the light source. With masked systems, there’s the cost of the ink or wax, but also the expense to replace the printhead, which can be thousands of dollars. Masked systems are priced far lower than maskless system, however, so it’s yet to be determined which technology will reign. I believe both platforms will see marked improvements over the next decade, and that could bring immediate and long-term return on your investment.
Table 1 Typical cost savings from CTS screen making.
Many believe the cost of adopting CTS technology is prohibitive; however, once you account for the labor and cost of generating new pieces of film, it’s easy to see the return. Even if your costs were just half of those projected in Table 1 (above), the return on investment for a $70,000 CTS system could be four years or less. And that only covers the direct cost savings. When you think about the time saved registering screens on press, the number of steps you cut out of the screen making process, and all of the hassles of working with film (let’s not even talk about the tape), you’ll see that this is one of the best investments a shop can make.
As you look at the various CTS options, which begin around $50,000, try to buy at a level you can grow into versus buying a model that only serves your current needs. You’ll appreciate the additional capacity of a more capable system as you grow.
Automatic Screen Cleaning
Advancements in screen cleaning systems have prompted many shops to consider looking beyond post-press cleaning of the screens. These systems come in a wide range of options from simple washing systems for post-exposure stencil development to more complex units that not only develop the stencil, but can also degrease the screen prior to coating and remove the stencil when you want to use the screen for another job. They also come in a variety of sizes from standalone units to modular systems with independent stations for each process (decoating, degreasing, etc.).
As with most of the equipment described here, many automatic screen cleaning systems are programmable, allowing for easy operation and a multitude of options. Screens are loaded into standalone units one at a time and processed individually, whereas on modular systems, screens are transported automatically via a conveyor through each station. The operator loads screens at one end and collects the finished screens at the other.
Keep in mind that several of your vendors are stakeholders when you look into incorporating an automatic screen cleaning system, and not just the company that builds the machine. The companies that make your screen cleaning chemistry and inks are also interested parties, to name just a few, not to mention your providers of electricity, water pressure, drainage, etc. It’s important that all parties be involved in the decision making process and communicate with one another before you make a hefty investment.
Is Automation Right for You?
Advantages of automation include the simple fact that machines can be used for repetitive and boring work, producing more goods in less time with fewer materials and waste, all at a higher quality level. Automation also saves money, which is important for shops facing tighter margins. Automating a process is cost-effective and profitable, if done correctly. It allows a company to employ less staff. Machines don’t need benefits or holiday pay, and they don’t call in sick or ask for personal leave so they can follow their favorite band around the country.
On the other hand, automation usually replaces jobs instead of creating them, and it alters the balance between skilled and unskilled workers. Let’s say you have five people working in a busy screenroom and you determine that automating the processes would only require one operator/technician. You’ll need a more skilled worker, so you’re essentially trading one set of skills for another while employing fewer people. And machines will break down, usually at the most inopportune time. It’s a good idea to keep spare parts on hand for those occasions. You’ll never know when a printhead for your CTS system will break down.
So the first question to ask is, “Can it be automated?” If so, then ask yourself whether the process you’re thinking of automating – cleaning a frame, stretching mesh, coating or reclaiming, etc. – suffers or benefits from human involvement. Take the time to study each process and task at the level of detail needed to quantifiably evaluate the potential application and benefit of automation. All of the equipment discussed here will bring you clear benefits in quality, speed, and improved productivity.
And what about the job cuts that could follow automating your screenroom and the associated damage to your reputation that could follow? Many business owners look for other useful functions their staff could support. If job loss is inevitable, then give as much forewarning as possible to those who will be affected. It’s never an easy decision, but as a business owner, your business is the priority. Keeping it profitable will sometimes mean making tough decisions.
The Automation Issue, Steve Duccilli
Killing Your Top 5 Time Wasters, Mike Ruff
Going Digital: Automating Sales and Marketing, Mark Coudray
5 Steps to Take Control of Your Printroom, Marshall Atkinson
MIS: Whipping Your Data into Shape, Eileen Fritsch
An Automation Wish List for Your Printroom, Marshall Atkinson