Infrared
Infrared emitters heat the product surface without any contact – usually as a fast-reacting complement to hot air, or as a preheating zone right after the extruder. Which wavelength and which emitter arrangement work best depends on the profile; the number of emitters can also be adjusted per module, and together these choices determine how deep the heat penetrates and how evenly it spreads.
How it works
Infrared emitters heat the profile surface without contact, purely through thermal radiation. Unlike with hot air, no equilibrium is reached within typical process times: as long as the radiation keeps acting on it, the surface just keeps getting hotter, rather than levelling off at some fixed temperature the way it does with convection.
Influencing factors in detail
Fourth power (Stefan-Boltzmann law)
Under the Stefan-Boltzmann law, the heat flux transferred grows with the fourth power of the temperature difference between the emitter and the profile surface. In practice, that means even a small change in emitter temperature has an outsized effect on heating power.
Continuous rather than bounded increase
Because no equilibrium is reached, radiation applied for too long or too intensely can overheat the surface all the way to decomposition. In practice, emitter power is often stepped down along the line once the surface has been shocked once, hard – after that first pulse, a gentler touch is enough.
Scientific basis
- IKV HeatStraD
- At RWTH Aachen's IKV, the heating of EPDM profiles via infrared and hot air was measured side by side — near the surface and in the profile core. Result: infrared keeps heating the surface continuously, while hot air reaches a temperature plateau. These measurements fed into the dissertation of project lead Dr.-Ing. Florian Lemke, "Vulcanization Strategies for Sulfur-Curing Rubber Profiles" (RWTH Aachen, 2022).
