Radio Frequency (RF) Technology
Since the early days of radio communication experts in the field have known that many kinds of materials in a high-frequency field exhibit a heating effect.
There are two methods of heating, depending on the material to be heated – Dielectric and Induction.
Stanelco are proud to have been developing and supporting a full range of radio frequency applications since the 1950s. Dielectric heating is particularly relevant to welding plastic sheet materials. Radio frequency Induction heating is applicable to precise sealing utilising metal conductors.
Dielectric Heating
Dielectric Heating, is a process for heating electrical insulators. Without forgetting the achievements of Nikola Tesla (1856-1943), Dielectric heating is historically independently attributed to Jacques Arsène d'Arsonval (1851-1940), together with the medical application of high frequency heating, Diathermy.
Most electrically insulating materials are made of molecules which have separate regions of positive and negative electric charge. If the material is placed in an electric field the molecules will rotate to align with the field, in much the same way that a compass needle aligns with the Earth's magnetic field.
Our Dielectric Heating equipment uses an electric field which alternates at radio frequency, typically 13.56, 27.12 or 40.68 million times per second, dependent on the application. The rapidly alternating electric field causes the molecules to vibrate, resulting a heating effect, like food heating up in a microwave oven.
Dielectric Heating is particularly appropriate for welding plastic sheet materials. Traditional heat sealing uses hot tooling to conduct heat into the plastic. To do this the tool must be hotter than the desired fusion temperature. When the tool contacts the plastic, the surface is melted before the weld interface. Surface melting often produces a weak weld with a poor surface appearance.
Dielectric welding uses cold or warm tooling significantly below the plastic melting temperature. High voltage radio frequency power is applied, causing a uniform heating effect in the weld area. Because the tooling is significantly below the melting point of the plastic it cools the surface of the material, allowing the weld interface to melt before the surface. The end product is a stronger, more reliable weld.
Induction Heating
Induction Heating is a process for heating electrically conductive materials. In 1831 Michael Faraday invented the solenoid and independently discovered the principle of Induction, leading to the understanding and exploitation of the related heating effects. In contrast to Dielectric Heating which generates heat uniformly throughout the receiving material, Induction Heating generates heat at the surface. It works like this. If an electrically conductive material is placed in an alternating magnetic field then circulating electrical currents will be induced in the material. If the coil which creates the magnetic field and the frequency of operation are chosen correctly then these currents can cause extremely precise and controllable heating.