User login

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.


click an image below to view slideshow

By Mark A. Coudray

Unfortunately, blackbody panels are not particularly responsive and their cycle times are pretty broad. Temperature is usually controlled by retracting the unit away from the printing platen. The panel cycles in for the flash and pulls back after some designated time interval. This is fine for plastisols printed on cotton, but definitely not satisfactory for more sophisticated inks and fabrics.

The solution came with the introduction of quartz tube flash units, which use incandescent tungsten filaments. Think of them as incandescent light bulbs on steroids. They are highly accurate, instantly responsive, precise, and controllable – but they are also much more expensive than panel flash units. They can be controlled with percentage timers, thermostats that measure bulb temperature, or surface thermo probes that shut the lamps off when the desired surface temperature has been reached.


FIGURE 2 Presses with quartz flash units and thermo probes that interface with the control panel allow the surface temperature of the platens to be continuously maintained during a run.



Quartz flash units are very popular because they can be cycled down to a standby temperature and almost instantly energized to the target IR frequency. Because they are highly controllable, we can use Planck’s law to precisely calculate how much energy we need to get the job done. Better yet, they allow the use of thermo probes to monitor surface temperature continuously and adjust lamp intensity based on the target temperature. As platen temperatures rise during the run, the thermo probes reduce the flash cycle time to only raise the surface temperature to the target level. (See Figure 2.) This is a major advantage when dealing with temperature-sensitive materials like rayon (tri-blends), acrylics, and sublimation-prone polyesters.

Quartz units operate in what’s known as the near- to medium-IR region. In flash curing, IR frequencies do the work and are invisible to us. The light you see emitted from the bulbs is waste energy and is a function of the operating temperature of the bulbs. As the temperature of the filament increases, it begins to emit color – first a deep red, then red, orange, yellow, and finally white as it reaches very high temperatures. The shorter the wavelengths emitted (tending toward white), the more reflective the energy becomes.


Terms:

Did you enjoy this article? Click here to subscribe to the magazine.