Connect with us

Prepress & Screen Making




“And this is where we prepare screens,” you say, rushing valued clients who just popped in for an unannounced visit past the doors to your cleaning and reclaiming area. “Let’s head to the production floor, where we actually print your jobs. It’s much more interesting!”

“And this is where we prepare screens,” you say, rushing valued clients who just popped in for an unannounced visit past the doors to your cleaning and reclaiming area. “Let’s head to the production floor, where we actually print your jobs. It’s much more interesting!”

Why are you deflecting your customers’ attention from your screen room? Is it because solvents and other chemicals are flying all over the place? Could it be that your employees spend way too much time incompletely cleaning and reclaiming screens or damaging the mesh by using tools improperly or mishandling the frames? Whatever the reason, you’re missing out on a prime opportunity to show your clients how well you can manage an early step of the workflow that ultimately determines the quality of the prints you produce for them. This article describes the types of automated screen-cleaning and reclaiming systems available today and how they can boost consistency and efficiency in this key area of your operation.

Manual vs. automatic

Let’s get one point out of the way before we start our discussion about these ma-chines: A screen cleaner is a tool that removes inks from screens that will be used again for the same job. A screen reclaimer, on the other hand, comple-tely removes the stencil and dehazes and degreases the mesh, thereby leav-ing you with a screen that you can use on another job.

Completely manual cleaning and reclaiming units can be as straightforward as open-chamber booths or dip tanks into which you load screens that either need to be washed for reuse or prepped for new stencils. They can be quite economical and effective in getting the job done, provided they’re used properly. These tools require more human intervention than automatic cleaning and reclaiming systems.

The basic reclaiming workflow involves ink removal, emulsion re-moval, and a high-pressure washout. Users who manually wash and reclaim screens must be careful to monitor chemical strengths and soak times and closely control the ways in which they use related cleaning tools—high-pressure washers, for example. Employee safety also is paramount. Eyes, skin, lungs, and clothing can damaged by exposure to some of the chemicals commonly used to clean and reclaim screens. Care also must be taken in handling and transporting screens. Properly tensioned mesh can easily be rendered unusable when it’s not given the attention it deserves.

Chris Williamson, equipment marketing manager for Image Technology, Anaheim, CA, cites several benefits to using automatic systems, from quality to ecology: “You’re going to get a consistent screen and your mesh consumption is going to decrease as your handling of the screens decreases. Depending on how you processed your screens before having the machine, the automatic will speed up production time and screen turnaround, shorten labor time, and—in some instances—it can save on che-micals and decrease the amount of effluent going down the drain.”

Some manufacturers offer automatic screen-cleaning and reclaiming systems separately; some produce them as modular units that can be connected to work as a cohesive, inline system; and some engineer complete turnkey screen-preparation solutions that wash screens, reclaim, dry, coat with emulsion, dry, image via a computer-to-screen device, and develop—all inline (Figure 1). In other words, a screen comes off of a press and is loaded into one end of the system. It comes out the other side ready to return to the press for a completely different print run.

“In general, automatics take out the guesswork, and they allow the operator to walk away and do something else,” says Andrew Weidenhamer, US and Canadian equipment sales manager for Sefar, Lumberton, NJ. “You know your ink system. You know your mesh count. Inputting those parameters allows the machine to determine the best cycle. There’s some trial and error, but there are enough benchmarks for optimum cycle times, given proper chemistry for reclaiming.”

Employee health and safety and the protection of the environmental have grown in importance over the past several years. Sylve Ericsson, executive vice president of Passaic, NJ-based Interchange Equipment, says automatic screen-cleaning and reclaiming systems offer printers a powerful tool in that department, because they reduce exposure to the chemicals and tools used in the process. He also notes that automatic systems reduce chemical usage and waste.

“Most find the working environment for manual screen reclaiming the worst place to be,” Ericsson says. “An automatic reclaiming system minimizes the evaporation of fumes from chemicals because they are kept in a confined environment in the machine. It also saves on consumables—chemicals. A machine uses chemicals more thoroughly. They have a longer mileage.”

Types of automatics

The starting point for automatic screen cleaning and reclaiming is the standalone, non-conveyorized, self-contained unit. You load the screens in, the machine cycles, and then you unload the screens to move them to the next step.

“A non-conveyorized system contains an ink-removing chamber and an emulsion-removing chamber. Those are for small to medium shops, whether graphics or textile. They want to automate, but they don’t have the money or space for a full-blown unit,” Williamson explains. “The systems require manual loading and unloading and transport. There are two dip tanks. Workers load a screen into the ink washing section, then they pull it out, dip it into fresh water, and then dip it into a tank that has emulsion remover. It softens the emulsion, and then they put it into the high-pressure rinse section, and then put another screen into the ink-wash section, and shut the door. When one screen is de-inked, the other screen has its emulsion removed.”

The next level in automation is the inline system. Two configurations are available. One keeps the screen stationary during each stage of cleaning and reclaiming and automatically moves the screen down the line upon completion of each step. The other keeps the screen in constant motion the entire time, stopping only when the operator unloads the screen at the end of the line.

“When you have an inline system where the screen is always moving, you have a smaller footprint—but your operated costs are much higher. The solvent and/or the water is always transferring from chamber to chamber,” Weidenhamer explains. “The advantage to an inline system where the screen starts in one chamber, and you have ink removal, then it indexes to the next chamber, is that you get a much more cost effective system because you don’t have as much solvent transfer into the water. It’s much more cost effective with chemistry.”

Chemical application is handled by high-pressure spray nozzles or brushes. Some manufacturers say spray nozzles do a better job of protecting the mesh and that brushes can excessively abrade screens. Others say brushes are more effective because brushes work the chemicals into the mesh and use less chemicals than spray nozzles. Ericsson says mesh is very tough and that it isn’t normally harmed by the brushes or high-pressure spray. “Only when you apply high pressure manually, then you can harm the mesh—especially when you go in very close to the corners,” he says.

Chemicals applied in automatic screen-cleaning and reclaiming equipment must constantly be kept as useful as possible in order to keep up with the pace at which the systems operate and break down inks and emulsions as expected. Recirculation and filtration facilitates the reuse of solvents. Some systems use pressurized filtration vessels. Others employ a filter that spans the length of the machine. Another option is a centrifuge (Figure 2) that spins waste to separate solids from liquids. Opening the centrifuge reveals a dry cake of waste solids.

A modular inline system allows you to leave yourself an opening for future add-ons. For instance, if you want some automation right away but can’t afford every piece of processing equipment at once, you can start with an automated screen-washing unit, add a reclaiming unit the next year, and hook up a dryer after that. From there, you can integrate an automatic coater, computer-to-screen system, stencil developer, and more. Whichever route you take, be sure to investigate the ways in which each piece of screen-cleaning and reclaiming equipment will protect employees.

“You have standard stop/go buttons. In the case of a jam, a safety clutch would prevent the machine from trying to index a frame,” Weidenhamer explains. “You have sensors that monitor screen movement and prevent operation in the case of blockage. Door-override locks prevent people from arbitrarily opening doors either physically or by the push of a button when the machine is in use. If you’re spraying a solvent at 30 bars (435 psi), it’s going to atomize. If you open a door, you’ll get sprayed. Safety systems keep that from happening.”

Volume and size decisions

When is the right time to upgrade to an automatic screen-cleaning and reclaiming system? Is it when the frames you use get so big that your whole prepress department has to join in lifting and carrying them? What about when you have so many screens that you have a path from your presses to your screen room that looks like the yellow brick road?

“If you have very large frames, maybe 20 a day, you might have a need for an automatic unit,” Ericsson says. “In medium sizes, if you’re doing 35-40 frames a day, you should look into automation.”

Williamson explains that automated systems can move frames along at speeds from a foot to three feet per minute, thereby enabling a shop that specializes in grand-format graphics to process oversized screens in a matter of a couple of hours. He says garment shops have different requirements and that 250-300 screens per day is a good time to start checking out conveyorized automatics. Garment screen printers who process that many screens typically use magazines or gang screens in master frames to increase the number of screens that can be processed in each machine cycle. “A lot of people who have conveyorized units for garment screens are washing anywhere from 400-600 or 700 screens per shift,” he notes.

Most manufacturers build automatic screen-cleaning and reclaiming systems according to customer specifi-cations. How big should you go? Consider the machine’s footprint, given the sizes and quantities of frames with which you work, in relation to the shop space you have available. Don’t forget that you need plenty of room at the loading area to present the screens—or magazines, cartridges, and master frames, as shown in Figures 3a and 3b—to the cleaning and reclaiming system, as well as ample space to unload them at the other end.

Tips for first-time buyers

“Go see the systems operating,” Weidenhamer advises. “And don’t go to one that’s only been around a couple months. Go see one that’s been around for a while. Then you get a true feeling of what’s involved. And remember that nothing is maintenance free—equip-ment is equipment. The type of system you choose should fit the screen throughput you need, and be sure to pay attention to operating costs. Solvents can get really expensive over time.”

Do you believe that if a little is good, then a lot must be great? If so, Williamson urges you to slow down and consider what’s involved with your first investment in automatic screen-cleaning and reclaiming technology. “You want a machine that’s not overcomplicated, and you want to be sure that parts are readily available,” he says. “The machine has to really suit your operation. Some people get a one-machine-fits-all, but that doesn’t work for everybody. And I don’t know that you need to buy the most machine you can afford.”

As you can see, automatic screen-cleaning and reclaiming systems might not be for everyone. But should the need arise—whether you specialize in garments, graphics, or industrial applications—these automated machines can streamline a critical part of your production flow, improve environmental conditions for workers, minimize waste, and help ensure that every screen is in top shape before it moves on to press.

Automatic Screen-Cleaning/Reclaiming Systems

A.W.T. World Trade, Inc.
4321 N. Knox Ave.
Chicago, IL 60641
Fax: 773-777-0909

Chemical Consultants, Inc.
1850 Wild Turkey Cir.
Corona, CA 92880
951-735-5511, 800-753-5095
Fax: 951-735-7999

Chemisphere Corp.
2101 Clifton Ave.
Saint Louis, MO 63139
Fax: 314-644-1425

Grunig-Interscreen AG
Distributed by Sefar Printing Solutions Inc.
120 Mt. Holly By-Pass
PO Box 679
Lumberton, NJ 08048
Fax: 609-267-1750

Hydro Engineering Inc.
865 W. 2600 S.
Salt Lake City, UT 84119
801-972-1181, 800-247-8424
Fax: 801-972-3265

Image Technology, Inc.
1380 N. Knollwood Cir.
Anaheim, CA 92801
714-252-0160, 800-554-6243
Fax: 714-252-9436

Interchange Equipment Inc.
90 Dayton Ave.
Passaic, NJ 07055
Fax: 973-473-4485

PO Box 5426
Sarasota, FL 34277
Fax: 651-686-9745

1219 W. 11th St.
Los Angeles, CA 90015
213-747-7799, 800-433-7799
Fax: 213-747-8270

Screen Systems
4204 E. Lake St.
Minneapolis, MN 55406
612-729-7365, 800-221-4079
Fax: 612-729-6647, 800-544-7022


Most Popular