3D Printering: Induction Heating

Every filament-based 3D printer you’ll find today heats plastic with resistive heaters – either heater cartridges or big ‘ol power resistors. It’s efficient, but that will only get you so far. Given these heaters can suck down only so many Watts, they can only heat up so fast. That’s a problem, and if you’re trying to make a fast printer, it’s also a limitation.

Instead of dumping 12 or 24 VDC into a resistive heater, induction heaters passes high-frequency AC through a wire that’s inductively coupled to a core. It’s also very efficient, but it’s also very fast. No high-temperature insulation is required, and if it’s designed right, there’s less thermal mass. All great properties for fast heating of plastic.

A few years ago, [SB] over on the RepRap blog designed an induction heater for a Master’s project. The hot end was a normal brass nozzle attached to a mild steel sleeve. A laminated core was attached to the hot end, and an induction coil wrapped around the core. It worked, but there wasn’t any real progress for turning this into a proper nozzle and hot end. It was, after all, just a project.

Finally, after several years, people are squirting plastic out of an induction heated nozzle. [Z], or [Bulent Unalmis], posted a project to the RepRap forums where he is extruding plastic that has been heated with an induction heater. It’s a direct drive system, and mechanically, it’s a simpler system than the fancy hot ends we’re using now.

Electronically, it’s much more complex. While the electronics for a resistive heater are just a beefy power supply and a MOSFET, [Z] is using 160 kHz AC at 30 V. That’s a much more difficult circuit to stuff on a printer controller board.

This could be viewed as just a way of getting around the common 24V limitation of common controller boards; shove more power into a resistor, and it’s going to heat faster. This may not be the answer to hot ends that heat up quicker, but at the very least it’s a very neat project, and something we’d like to see more of.

You can see [Z]’s video demo of his inductive hot end below. Thanks [Matt] for the tip.

13 thoughts on “3D Printering: Induction Heating

    1. That’s doable, but it would require quite a lot of power. And the nozzle would have to be made of ceramic of some kind. And with bigger power requirements whole nozzle assembly would be too heavy to move with precision. Also how one would manage all the heat from molten steel?

    2. The problem with 3D-Printing metals is not about getting them to melt, but about getting them in a soft but not fluid state where it can be extruded.

      You face a lot of problems like surface tension when extruding fluids.

      1. I would think bonding would be an issue too. You would have to have the whole print platform surrounded by inert gas, or apply some kind of shielding/flux. And as you said getting them soft enough. When welding both the base and the filler are heated to a liquid state. Unless the print chamber is heated to just below the melting state where the new layer will heat and bond with the previous layer, I see it as a no-go.

        1. Given the generating coil would be quite close to the nozzle outlet and so the point of contact, I wonder what sort of ‘flux spill’ there would be. Critically, would the effects of the field be enough to cause sufficient heating, not just in the metal currently being extruded but also the landing site.

          I suppose, if the heating of the base where the semi-molten metal is being placed, is sufficient, then there’s a risk that it (the wall being added to) may deform under its own weight (or at least sag).

  1. One issue might be whatever radio regulatory agency where you are may consider this a transmitter and I dont think 160KHz is a ISM band. Maybe change the frequency to 450khz or 13.56MHz, both are common ISM bands. Metcal soldering irons work at these two frequencies, it might be possible to adapt one or the other to work.

  2. Sorry, but what is the point?
    since you don’t use induction to heat the plastic directly but a metal core I don’t see the difference with the classic resistive things… driving resistance at 24Vdc and use regular caridge rather than a custom plastic heating chamber is the limitation in most designs, but nothing prevent someone to drive a more powerfull 230Vac heater… without having to mess with induction heating…

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