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T-Shirts to Medical Trays: An Intro to IR Conveyor Dryers

(June 2013) posted on Tue Aug 06, 2013

The IR conveyor dryer has a home in applications beyond screen-printed garments.

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By Mark Vasilantone

Infrared radiation is measured in terms of wavelength (not temperature), which is expressed in microns (μm). For most screen-printing inks, the optimum frequency is 3.2 μm, which is at the top end of the mid-micron range. At this frequency, the infrared radiation is readily absorbed by the ink, causing its molecules to vibrate and generate heat. However, most quartz tubes in dryers for screen-printed items generate infrared radiation in the mid-micron range, which can make them less efficient for curing of screen-printing inks.

Cold spots
An infrared panel is powered by a long, electric wire routed back and forth in a parallel pattern across the panel, with the distance between the wires determining its core density. Because the temperature between wires spaced widely (2 in.) can drop by approximately 100°F, you should specify a heater having wires spaced at approximately 0.75 in., to provide sufficient core density to prevent the ink from cooling as it passes between wires.

Dryer width
It is advisable to specify a wide dryer if budget permits so that you can dry large garments or two small garments side-by-side, as well as blankets, signage, binders, metal parts, advertising specialties, and other screen-printed items. A dryer with a 30-in.-wide belt, for example, cannot cure an overall-printed shirt that measures 40 in. sleeve-to-sleeve.

If your budget is limited, the higher cost of a wider dryer can be offset by purchasing a shorter (less costly) dryer initially and then adding heating chambers, if possible, at a future date to increase capacity as you grow.

Applications beyond garments
It is typically less expensive to purchase a dryer that offers greater capabilities than you need today, than it is to purchase a larger dryer when you require greater capacity or the flexibility to expand beyond garment printing.

Consider that the same screen-printing presses and dryers used daily by thousands of garment printers worldwide are also used to print and dry a range of signage and hard goods.

One example is screen printing on medical-delivery trays (Figure 2) that contain and identify surgical instruments. Because the trays are used several times per day, they are sterilized in autoclaves where they are subjected to pressurized steam after each use, placing rigorous demands on the screen-printed graphics.

Screen printing has long been the industry standard for printing on instrument-delivery systems because of the need to use highly specialized inks that stand up to repeated autoclaving and due to the varying shapes of the trays. This application requires uncompromising quality standards, while others involve irregularly shaped items, extra large (heavy) screens, extremely short runs that have fast setup and microregistration, extremely tight multicolor registration, and other future requirements that may hinge on the capabilities of your screen-printing equipment. It is therefore prudent to select equipment that will expand, rather than limit, opportunities that may arise during your screen-printing career, even if you cannot use some of the equipment's capabilities at the onset.

Mark Vasilantone is president of Vastex International, Inc., Allentown, PA.  All photos courtesy of Vastex International, Inc.





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