Some of the most impactful display graphics owe much of their appeal to the painstaking process of distortion printing. This article uses an actual job to describe the demanding workflow.
If an image is printed on the sheet prior to vacuum-forming, that image will stretch and distort with the sheet as it becomes malleable. To combat this distortion and to register specific image areas to targeted locations on the mold, the image must be manipulated or counter-distorted in prepress. A properly distorted image, while still unformed, may look more like road-kill than the finished 3-D part it becomes. This image manipulation is the core of distortion forming and will make or break a project.
A real-world example
Joliet Pattern recently completed a signage project for the Kentucky State Lottery that involved 400 two-sided, distortion-formed outdoor signs. Each sign consisted of two identical, 32-sq-in., vac-formed panels (front and back), bounded by an aluminum frame (Figure 3).
Substrate selection A clear substrate is preferred for a project like this, because it allows us to print second-surface, which affords the screen ink a layer of protection from the elements and cleaning solvents. We chose polyethylene terephthalate glycol (PETG), a clear thermoplastic, for several reasons. It is strong and rigid, has fairly high impact strength, weathers well, UV-ink adhesion is rock-solid, and it vac-forms easily and predictably. Each sign panel must be rigid enough to be self-supporting, so we chose 0.10 in. as a starting gauge—thick enough to give the finished panel adequate mass, yet thin enough to allow mold detail to show through the substrate.
Tooling We fabricate a production mold using the traditional method, starting with a male pattern made of wood. In this case, the use of male tooling places the finished sign panel’s front surface away from the tool, so the substrate’s naturally glossy surface will not be affected by contact with the mold’s surface.
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