The digital revolution has its sights on a new challenge, and decorating three-dimensional objects offers no shortage of puzzles or possibilities.
By Debbie Thorp
When thinking about printing onto objects, it can be useful to imagine that shape as being flat. For example, if you take a tube, cut it lengthwise, and lay it flat, it becomes a square or rectangle, depending on its height. The shape is now a familiar one for inkjet printing; the “flat” image just needs to be wrapped around the tube.
Developers use different positioning options for the printheads, depending on the overall configuration of their system. Some want to ensure that inkjet fits seamlessly into an existing process or product-handling mechanism, and this can dictate the way the heads are positioned. Typically, printheads jet downwards, and this is well-suited to systems using mandrels to move the products, but in some systems, items such as beverage containers may be gripped by the neck and presented vertically to the printheads, which means that the heads must be positioned in “skyscraper” mode, jetting sideways onto the object.
A number of systems are now available for printing onto tubes or cylinders. Among the small-format flatbed printers, Mimaki introduced the Kebab option for its UJF series, Roland markets the RotaPrint attachment, EPS offers the Bottlejet, Direct Color Systems has the EasyCyl attachment for its 1024 printers, and AzonPrinter offers the Rotax. Other production tube decoration systems include the Michelangelo KX48P from Martinenghi, launched at MetPack 2013, and the new ServoJet from OMSO introduced at last year’s K Show.
From medical devices to consumer goods, the possibilities for direct-to-object decoration are vast. Courtesy of EPS.
An increasing number of systems can now print not only onto tubes, but also onto conical or tapered shapes as well, which are far more challenging. If you cut a cone lengthwise and lay it flat, you would create a shape that looks like a section of a circle. During printing, as the cone narrows, the resolution changes, as does the speed of rotation under the printhead. In order to print an image successfully onto the whole circumference of a conical object, you must use image compensation software that employs special screening and/or color management techniques to correct for the changes in dot gain. Differences in drop time of flight, nozzle misalignment, and density changes all need to be corrected as well in order to produce a fully compensated image with minimal image artifacts.
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