If you have a desktop 3D printer based on FDM / FFF technology you probably know how the extruder heating works and that the design principle has not changed for many years. The common extruder hot end is based on resistive heating where DC electric current causes heating up of a heater element. This solution is simple, well researched and cheap but it’s bulky and takes some time to reach the desired temperature.
An inductive heating hot end is a more complex hot end which needs high frequency AC for induction coil but it requires much less insulation mass and reaches desired temperature almost instantly. Less mass on an extruder would result in higher movement speeds and precision with much better temperature control.
Main disadvantage of an induction heated extruder is that it takes much more complex control and drive electronics / electric subsystem with possible inductive interference from the coil “leaking” into environment and interacting with a 3d printer build platform or other devices.
Wikipedia defines induction heating as:
Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, through heat generated in the object by eddy currents (also called Foucault currents). An induction heater consists of an electromagnet, and an electronic oscillator which passes a high-frequency alternating current (AC) through the electromagnet. The rapidly alternating magnetic field penetrates the object, generating electric currents inside the conductor called eddy currents. The eddy currents flowing through the resistance of the material heat it by Joule heating. In ferromagnetic (and ferrimagnetic) materials like iron, heat may also be generated by magnetic hysteresis losses. The frequency of current used depends on the object size, material type, coupling (between the work coil and the object to be heated) and the penetration depth.
An important feature of the induction heating process is that the heat is generated inside the object itself, instead of by an external heat source via heat conduction. Thus objects can be very rapidly heated. In addition there doesn’t need to be any external contact, which can be important where contamination is an issue. Induction heating is used in many industrial processes, such as heat treatment in metallurgy, Czochralski crystal growth and zone refining used in the semiconductor industry, and to melt refractory metals which require very high temperatures. It is also used in induction cooktops for heating containers of food; this is called induction cooking.
There are only a few sources of information on the internet about this inductive heating extruder type but there are several people trying to develop it. Most of publicly known solutions are rough homemade hot ends and it will take some time for this technology to reach standardization and wide implementation.
One of the people who published their working induction heated extruder is RepRapBuilders user “SB” who posted about his inductive hot end extruder done as a master thesis project:
Here is his extruder and schematics:
There is also a YouTube user from Turkey, Bulent Unamis, who published this video of a working model extruding the filament:
Induction heated extruders certainly have a future in 3D printing hot ends and they will probably find their way into some machines be it in industrial or home setting. Advantages are too many to ignore it. Until the technology is commercially developed and taken seriously by a bigger company it will remain in the domain of hobbyists and 3D printer hackers.
We hope you learned something new about 3D printing technology by reading this article. Feel free to post any questions you may have in comments!