Doming is a finishing process that not only enhances the appearance of printed items by producing a three-dimensional look, but it also makes them more durable.
Doming is a finishing process that not only enhances the appearance of printed items by producing a three-dimensional look, but it also makes them more durable. The doming process relies primarily on three components: a dispensing system, resin, and a product with surface tension sufficient enough to accept and control the liquid doming resin during and after application.
Essentially, the dispensing equipment draws or receives the doming resin from dedicated containers and then deposits the resin on the surface of a receptive product. Cutting a product to its final shape creates the requisite surface tension. Cutting a printed decal in a rectangular shape, for example, naturally sets up that decal to support a dome of the same shape. Once dispensed, the resin flows to the edges and stops at the boundary created at the cut (Figure 1). The end result is a lens-shaped coating—a dome—on that product.
Dispensing equipment is available in numerous configurations and can accommodate products of varying shapes and sizes and job orders large and small. Here are some terms—associated primarily with machines that dispense two-part polyurethane resins—that you’ll likely encounter in your research:
Meter-mix Also referred to as meter-mix-dispense, this means the dispensing machine meters (measures) the resin components by volume and then mixes the components before depositing the resin onto the products.
Static mixer This refers to the dispensing machine’s mixing unit, which is responsible for blending resin components. A static mixer is often a simple, rigid, plastic tube that houses a series of helical elements. As both components of a two-part polyurethane resin enter the static mixer, they’re sheared and blended together when they pass over each element. The result is a homogenous mixture ready for deposit. Static mixers are common in dispensing equipment, whether entry-level or fully automated.
Dynamic mixer The dynamic mixer is similar to the static version in that it relies on the helical elements, but it also consists of a pneumatic motor that is integral to the dispense head. This motor complements the static mixer’s shearing and blending effect with rotary motion, which provides additional mixing.
Piston-metering systems Some dispensing machines rely on pistons to measure the resins. The pistons’ cylindrical housings are sized to conform to the volumetric ratio of the resin components, 1:1 and 2:1 being the most common. Upon actuation, the pistons push the precise amount of each toward the mixer.
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