Learn how to calculate the total amount of ink needed for any job based on mesh parameters and run length.
It's inventory time, and with pen and notebook in hand, you set out for the ink department. As you near the inkroom, however, your progress begins to slow. Ink buckets of every shape and size--none of them empty--litter the corridor. Hurdling a final stack, you push through the inkroom door and find yourself confronted with an even larger collection of containers filling every available inch of shelf space and stacked to the ceiling everywhere else. "We have enough ink in here to cover Texas!" you cry. "Where did it all come from?" From behind a wall of half-full five-gallon containers pops the head of your ink technician. "Hi Boss!" he answers. "Just leftovers from the jobs we've been running." If this sounds like a visit to your own inkroom, then you've been paying the price for inaccurate ink estimating. And the price is likely a high one. Not only do you have an expensive inventory that may rival your supplier's, there's no guarantee that you'll find a use for those 13 extra gallons of hot pink Pantone 812 or other custom-color leftovers before the ink goes bad. Poor estimating works in the opposite direction, too. If you're constantly coming up short on a particular color during a long run, you'll see costly consequences in the press time you lose while another batch is whipped up. Then there's the problem of getting the second batch to match the first. It doesn't have to be this way, though. A few details about your screens and a little bit of math can help you avoid the whole dilemma. It just adds up I'll admit it--I'm writing this article because I like math (must be hereditary). But even if you suffer from calcu-phobia, there's really no reason to be intimidated by a few mesh measurements and simple equations, which is all you need to get accurate ink estimates. Most of the numbers you require are readily available from mesh suppliers or sources like our Comparative Screen Fabric Guide (available through ST Publication's online bookstore at www.stpubs.com/stbin/quikstore.cgi). The best place to start when figuring out how much ink you need to run a job is to determine how much ink you'll need per print. The volume of ink that gets printed per image through a particular mesh is determined by five factors: * mesh count (M) * thread diameter (D) * fabric thickness (F) * coverage area (A) weave Stencil thickness may increase this printed ink volume. But with the thin stencils used in most graphics applications, the contribution to ink deposit is small enough to overlook for basic estimating purposes. How Much Ink Do You Need? Your first goal is to determine the wet ink-deposit height (I) delivered by a particular mesh. Wet ink-deposit height is defined as the thickness of a printed ink layer on a substrate after the mesh is no longer in contact with the substrate and the ink has flowed to a smooth, even layer. Over the years, mesh manufacturers and research groups including the Screen Printing Technical Foundation have developed several formulas that can be used to calculate theoretical wet ink-deposit heights for the fabrics they offer. None of these formulas will work with all meshes, but when used with specific mesh-count ranges and mesh types as shown in Table 1, they can be very accurate.
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