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.
Image location and manipulation We ordered the PETG stock at the time we began work on the tooling so the sheets would be ready and waiting for the completed mold. Ordering custom-run sheet is very important to the success of a distortion-forming project. For example, when heated in a vac-form press, extruded sheets stretch more across their length (the direction of extrusion), than their width (the transverse direction of the extruder). This differential can cause a lack of consistency from sheet to sheet. One way to minimize this issue, providing the extruder can accommodate it, is to call the sheet’s longer dimension its width—thus, its shorter dimension becomes its length. The sheet stock for our project is square, so we have a different problem—we must make sure each sheet is oriented the same way (relative to its direction of extrusion) from screen printing through forming.
We’ve asked our PETG supplier to add a scribe line to each sheet—another advantage to ordering a custom-run material. As the sheet is being extruded in a continuous line, a pen or stylus is mounted above the line, about a quarter of an inch in from one side and allowed to mark the stock as it flows past the instrument. After the material is cut into sheets, each one is marked with a scribe line that indicates the sheet’s extrusion direction. The scribe line becomes an orientation guide for our square sheet, delineating length from width and top from bottom.
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