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![]() Stretching Your Own Screens: Does It Make Sense for Your Business?
By Bill Stephens
The ability to stretch screens in-house can help boost production, reduce downtime, and give your shop the flexibility to take on a wider range of jobs. It brings with it both improved quality control as well as the ability to take on jobs that are more technically challenging and potentially more profitable.
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The downside is that getting set up for stretching screens can require a considerable investment, both in equipment and training and screen stretching can divert precious resources from core operations like production and marketing. Do you really have to go into screen stretching? Definitely not. Many very large and well-established screenprinters continue to rely on outside suppliers for all of their screens. It’s a judgment call whether or not a screen stretching operation makes sense for your screenprinting business. To help you make that decision you need information and these next few articles will take a look at what’s involved in building screens and setting up your own screen stretching department.
The importance of screens
What stretching your own screens can do for you You’re in the middle of an important production run and your screen rips. Normally, you have one or two backup screens available, but this time you don’t. If your shop doesn’t have the ability to stretch frames, you have few options other than to ship the frame back to your screen stretching supplier as rapidly as possible and wait for him to re-stretch it and return it. Depending on your distance from the supplier and his production schedule, several days may pass before you can get that screen back on the press. With your own in-house screen stretching operation that screen can be back on the press in a matter of hours. How much would that be worth to you?
Flexibility
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Improved quality control This becomes increasingly important as you take on more technically demanding print jobs such as four-color process printing. Successful four-color process printing requires four screens with identical mesh (thread count and thread diameter) stretched to identical tensions. An in-house screen stretching operation allows you to easily meet such specifications. This can also help improve print quality even in less critical jobs, because you can make sure your all screens are stretched with the correct mesh for the job and that mesh is always at the right tension. Screens, if handled carefully, can produce many thousands of impressions. However, mesh is subject to wear. It wears a little every time a squeegee passes over it. As mesh wears it loses tension, and at some point every screen will lose so much tension that print quality will begin to deteriorate. A busy screenprinting operation can wear out a lot of screens. At some point it becomes more cost-effective for that screenprinter to stretch his own screens rather than shipping them out. The savings on shipping costs alone could be a significant factor.
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Who should not do screen building?: Beginners Unfortunately for them, screens may appear simple, but they are also critically important to a screenprinting business and building a good screen is a technically demanding job that few beginners could accomplish. Of course, if someone were prepared to invest in the specialized equipment needed to stretch screens and put sufficient time and money into training, they could certainly do it. But if that person's objective is to become a screenprinter, he or she would be better off pulling prints or going out in search of new jobs than stretching screens. For someone just starting out, stretching screens is not a good way to save money.
Problem number one: Mesh tension presents challenges Today, screenprinters are often reluctant to work with mesh tensioned at less than 20 newtons per centimeter (20 N/cm). Mesh tension is expressed in units of measurement called newtons, a unit of force in the SI [mks] system. A screen frame holding mesh at 20N/cm has to be able to withstand a force of about 6.85 lbs. per linear foot, which means even a modest-sized screen holds enough tension to rip a poorly made frame apart.
Effects of weak frames Tension can also cause warping or twisting in weak frames. These frames can no longer allow lie flat, which means the mesh they contain cannot contact the surface of the substrate evenly. It is all but impossible to produce a good print with a screen that has a warped frame.
Even higher mesh tensions
Frame materials: Wood However, wood is also very weak. It tends to flex under pressure and as higher mesh tensions have become more popular, stronger materials such as steel or aluminum have gradually Wood also tends to warp as it absorbs moisture and unfortunately, screenprinting frames spend a good part of their time soaking wet. Every time an exposed image is washed out or a screen goes through the reclaiming process, the frame undergoes a dousing, often at high pressure. Under such conditions, even the strongest wooden frame will deteriorate.
Why aluminum has become the material of choice Few screenprinting shops, however, are equipped to cut and weld aluminum. So, the popularity of aluminum as a frame material has led to the outsourcing of most frame building to specialists. If you decide to set up your own screen stretching operation, chances are you will be ordering frames from an outside supplier. Next time, we’ll take a look at some of the important specifications to keep in mind when ordering from an outside supplier as well as a few tips that may save you some money.
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