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Component Care

(August 2004) posted on Sat Jul 31, 2004

Find out how to ensure a long and useful life from the tools you employ most frequently.


By Rick Davis

As I've visited various screen-printing companies over the years, I've been continually amazed at the condition in which employees leave work areas and equipment. In such shops, managers don't seem to realize that if any one component of the process fails, then production can come to a halt.

It may seem a trivial thing, but proper upkeep of every tool and piece of equipment in your facility has a significant impact on the overall efficiency of your operation. Equipment that is warped, nicked, contaminated, or uncalibrated will not deliver the performance or accuracy you need to meet your customers' demands.

In this installment, we will look at some of the more basic but crucial components of the garment-printing process and the procedures needed to properly care for them. Considering that the final product is a result of each part of the printing process working together, every piece of equipment in prepress and production should be properly cared for to ensure success.

Inside the screenroom

In the screenroom, few tools are taken for granted as frequently as one that is used day in and day out: the manual emulsion-coating trough. This simple piece of formed aluminum is easy to overlook, yet when it is damaged, you are no longer able to accurately and efficiently coat your screens with emulsion.

The first sin of improper coater care is wreckless handling, which can lead to nicks in the coater's straight edge. It's true that accidents happen, and coaters are easy to drop when they are wet from cleaning. However, taking your time during coating operations and cleaning will most likely eliminate the problem. Once a coater's edge has been nicked or deformed in any way, it will no longer be capable of producing a perfectly even coat, and your prints will suffer the consequences.

The need for coater care also applies to automated coating equipment. As with manual coating, the results of automated coating are only as good as the edge of the coating trough itself. Of course, you can file a nick off the edge of the coater, but once done, you will have an indentation in the edge that will now deposit a greater amount of emulsion than before the unit was damaged. Your only real options in such a situation include sending the trough out for remachining, investing in special grinding equipment to refinish the damaged edges yourself, or simply replacing the coating trough.

Exposure tables are another element of the process that take regular abuse. The most common type of damage that occurs with exposure units is that the glass table is scratched. This usually occurs when screens are slid into position across the surface of the glass. The damage can occur with screens using aluminum frames, retensionable frames, and even wooden frames from which staples may project.

Once a vacuum table's glass is scratched, you run the risk that the scratch mark will be reproduced onto all of your stencils. On screens, the scratch will manifest either as pinholes that require touching up or a weakened image area that can break down on the press.

The simple way to avoid this problem is once again to take your time and be careful when handling screens. Set the frame straight down onto the table glass and try to avoid moving it across the glass once you have it in position.

On the press

The components of garment presses that require regular care and maintenance (and seldom get it) are squeegees, floodbars, and platens.

Squeegees are the most fundamental components of the press that see daily use. Not surprisingly, they are also the press components that require the greatest care. Although today's squeegee materials are better than ever, they are still susceptible to damage from a number of sources, including the plasticizers and solvents used in inks and cleaning chemicals.

Squeegees should be removed from the press and cleaned of all residual inks and chemicals whenever the press is not in use--even if the press is down for only one shift. Polyurethane squeegees can resist solvents for as long as 8-16 hrs at a time, but if a squeegee sees frequent and repeated exposures like this, it may begin to absorb the plasticizers and/or solvents. This eventually causes the squeegee to swell and begin to lose its shape and rigidity. Most production employees would rather replace squeegee blades once any sign of wear or deformation occurs rather than add a few minutes to the daily setup or breakdown routines to remove and clean the squeegees or resharpen them.

In the name of preventive maintenance, squeegees should be removed from the press if the machine will be left set up over a weekend. Leaving the squeegees soaking in ink for two days will definitely deter the performance of the blades. Since most shops already take ten minutes or so at the end of a shift to clean up screens and other press components, this would be an ideal time to remove and clean squeegees as well.

The same care should be applied to squeegees in the cleaning area. When squeegees are removed from the press and sent to the cleaning area, they should be cleaned no later than the end of that day, then dried and returned to their regular storage area. I have been in quite a few printing facilities where squeegees are regularly left soaking in the solvent cleaning tank for days at a time. Exposing them to cleaning solvents for such long periods of time will seal their fate and likely leave you with blades that resemble Jell-O rather than squeegees.

Floodbars do not pose nearly the same challenges that squeegees do since they are impervious to inks and solvents. Unfortunately, they are susceptible to the same wear and damage as your emulsion-coating troughs. Most floodbars are made of aluminum and dent and nick easily. Damage usually occurs when floodbars are thrown onto the cleaning cart, where they bang into squeegee holders and other floodbars, resulting in nicked and damaged edges. This can result in problems such as uneven distribution of ink during the flood stroke, or, in the worst cases, ripped screens on the press.

The latter scenario means you'll have to stop the press while the screen is replaced or repaired--downtime that few shops can afford. That's why it's important to be careful when handling the floodbars, keeping them free of nicks and gouges and optimizing your shop's productivity.

Platens are the last component I would like to cover. Platens face two conditions that can be detrimental to their longevity. First is when ink is left on the platen for long periods of time. Depending on your printing conditions, which might include thin substrates, excessive squeegee pressure, and/or low-tension screens, you may find yourself with residual ink buildup on the platen surface. Many platens today incorporate a rubber surface that can absorb plasticizers and solvents in much in the same manner as squeegees do. As this occurs, the surface of the platen can swell, producing an uneven plane that can draw even more residual ink from subsequent prints and wreak havoc on fine-detail prints or halftone work.

The greatest deterrent against plasticizers or solvent absorbency is platen peel, a thin, protective adhesive paper that covers the platen and can be replaced daily. Shops that don't use it need to keep rubber platten surfaces free of inks and solvents and clean them whenever an ink film becomes apparent.

Another destructive force to platens is improper storage. When platens are stacked for storage, the metal clamps used to affix the platens to the press can leave indentations on adjacent stored platens. To avoid this situation, utilize a rack that stores the platens without allowing them to touch.

Conclusion

Ensuring the effectiveness and efficiency of your production process depends on employing proper handling, cleaning, and storage methods on an ongoing basis. Establishing regular cleaning and maintenance schedules as part of your standard operation procedure will help keep production snags at a minimum and your facility running smoothly.


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