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How to Optimize Your Flash Curing

(August/September 2017) posted on Tue Sep 12, 2017

Learn ways to increase your production while reducing cost, heat, and wasted energy.

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By Mark A. Coudray

First, use highly tensioned mesh with an off-contact distance of 1.5 millimeters (0.06 inches). Mesh tension of 25 newtons per centimeter is sufficient to minimize surface contact between the screen and the wet printed ink film. If you can limit the point of surface contact to the squeegee blade, there will not be enough force to lift the ink off the garment. While some transfer is inevitable, the vast majority of ink will remain on the garment.

Second, the critical ink film to flash is the underbase, which has different requirements than the surface or overprint layers. The primary objective with the underbase is to cause enough ink to penetrate into the garment to provide an anchor with the knit of the T-shirt. This ensures excellent washability for many cycles. But at the same time, we want the thinnest ink deposit possible.

Proper mesh selection is essential in meeting those requirements. My favorite is a 225/40 “S” thread mesh, which delivers excellent ink release with minimum squeegee pressure. It gives you a very thin, opaque layer of ink with minimum penetration into the garment, which will be very important once we apply heat to it. Our goal with the flash is to gel the ink just to the point where it won’t transfer. We definitely do not want to cure it completely because this creates a whole new set of problems. You know you have the right amount of gel when you can lightly touch the ink surface after flashing with no ink transferring to your hand.

To achieve this with the lowest amount of heat and shortest time, you need to preload heat into the system – a fancy way of saying to preheat your platens and warm up the ink. The key to maximum efficiency is to consider how much heat is actually needed to gel the ink. In shops that don’t understand this, flashes are too long, garments get saturated with heat, energy is wasted, and presses must be slowed down to deal with the consequences.

Plastisol ink is thermally sensitive. The colder it is, the higher its viscosity and the more unstable it will be on press.


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