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An In-Depth Look at Distortion Printing

(November 2009) posted on Thu Oct 22, 2009

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.


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By Andy Wood, Rick Turner

A profile view of the Kentucky Lottery mold shows it has a 1-in.-wide frame that’s raised about 1 in. above the plane of the perimeter cut line. Inside the frame, a white background is recessed about 0.25 in., and three distinct plateaus—each raised 0.25 in. above the white background—showcase the main graphical components of the art. The newly formed grid sheet is, in effect, a 3-D topographical map of this layout. Strategic x-y coordinates on the 3-D map, such corners of the frame, or key points of the plateaus, may be back-plotted to the original, flat grid sheet retained in the prepress department. The more coordinates that are transferred from the 3-D map to the 2-D flat sheet, the more accurate the registration of the printed image to the mold. 
 

Next, we send the combined grid with logo image file to our Lüscher direct-to-screen system so that we can create the first generation stencil. The logo image is composed of four colors (black, blue-PMS 300, green-PMS 375 and a double-hit flood-coated white background), so we’ll image and expose five stencils. We use a 350-thread/in. mesh for the black, blue, and green. We double-hit the white background to boost its opacity. We use 330- and 380-thread/in. mesh for the two screens dedicated to the white ink. The black screen combines the black components of the logo and the grid.
 

We’ll print six sheets or so for this first attempt. We haven’t removed the guide stops from our screen press, so these sheets—and all subsequent sheets—guide to the same stops as the original grid. Once printed, the sheets are sent to the vac-form press, which has been pre-heated in anticipation of their arrival. 
 

We cycle several scrap sheets through the forming press to simulate conditions of the production run, and the six first-generation sheets are cycled without pause. Generally, the last sheet of the group is sent back to the prepress department for image adjustment. We then compare the newly formed, first-generation part to the Illustrator file and look for areas of the image that do not fit the plateaus properly. 
 

Adjusting the image file becomes a matter of opposite movements. The grid, which was printed atop the logo image, helps to confirm the amount of movement necessary to counter misalignments, but it is not exact. Some guess work is involved. We address the misalignments and send the revised file to the screenroom again for the production of the second-generation screen set (Figure 4). This time, however, we’ll reclaim and remake only the black, blue, and green screens; the white flood-coat screens are unaffected by the distortion process and can be used again.
 



As before, five or six sheets of the second-generation image are printed and vacuum formed. We might be able to correct slight image misalignments at the forming pressby making small adjustments to the sheet’s position in the clamp frames, but going back to the art file to make corrections becomes necessary when substantial movement is required. Some distortion projects, due to image or forming complexity, may take six, seven, or even eight generations of image manipulations to correct. Ultimately, the Kentucky Lottery sign required five moves.
 

Adjustments to the image become too fine somewhere around generation three or four for the grid to be helpful, so we drop it from subsequent generations. Each generation normally takes about six to eight hours to complete from file manipulation to vacuum forming. A complex distortion-forming job may take as long as five or six days to complete.
 

A distortion job requires constant operator attention, no matter how careful we are to manage variables. Ultimately, the variables make for higher scrap rates projects, but a properly managed, dedicated run of extruded sheet helps keep rejects to a minimum. Joliet Pattern completed the Kentucky Lottery job, including installation, within 10 weeks of receiving client approval.
 

Have a comment about this article? E-mail it to the editors at screen@stmediagroup.com.

Andy Wood and Rick Turner
Andy Wood is owner and president of Crest Hill, IL-based Joliet Pattern, Inc. Rick Turner is the company’s senior project manager.


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