Induction coils are crucial components. They are, after all, what actually delivers heat to the workpiece during the heating process. But all too often basic coil maintenance is neglected. The results? Sub-standard performance, off-grade products, unnecessarily high costs and acute production crises. Yet ensuring your coils work optimally during a long life is relatively easy—provided you follow some basic guidelines. Induction coils are normally made from copper tubing. The coil is shaped to match the desired heating zone. Other factors influencing coil shape are the requirements for current/water cross areas, and matching to the frequency converter. Heat is produced by electrical currents that are induced in the workpiece; the current path in the workpiece following that of the coil. Maximum coil efficiency is assured by adjusting and improving the coil design to produce the optimal heating result. Following the desired heat pattern, the ideal coupling distance of 2–3 mm is then set to give the best and most efficient results. The second common solution is to add flux concentrators, produced from thin plate metal or from a special metallic powder set into plastic. Both methods can be used in conjunction but once installed, the performance of the flux concentrators needs to be maintained; the plates can short-circuit or be dislodged and the plastic composite concentrators are sensitive to heat radiation. It is also important to check whether any detergents or fluids remain from previous cutting operations.
Environmentally friendly fluids have a particular tendency to cover the coil with a conductive coating to reduce performance. And the quench medium itself must remain free from impurities to prevent additional coating of the coil and a blocked quench circuit.
Of course, no matter how good the maintenance, your coil only has so long a life span. According to the current, frequency, cooling system, and the size and shape of the copper tube the lifetime will vary. It’s a good idea to be alert and replace a fatigued coil before it causes you production problems. Whatever the make of your induction heater, EFD Induction will be happy to help with that. Just call and we’ll be on our way.