7 Uses for an Induction Heating Machine + How to Make One

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About: Electromechanical Engineer, Product Designer, Maker. I love to make prototypes and teach others in the process. I graduated from UCF and spent two years working at NASA.

In this instructable, I will show you how to make an induction heating machine and 7 different applications for it. Induction heating has many practical applications and making one is incredibly simple. First, I will go over the applications and then you can decide if you want to make one of these awesomely useful machines.

Step 1: Induction Case Hardening Steel

In this video I show you how to cryogenically case harden your low carbon steel parts with the induction heater. What you end up with is a material that has a ductile inner core with a hard outer shell. Parts that require impact resistance as well as abrasion resistance are great candidates for case hardening. Low carbon steel does not harden well on its own. When heating the part up and submerging it in a carbon compound, carbon gets impregnated into the surface of the material. This results in a hard outer surface.

Gears, Firing pins, Engine Camshafts, Lock Shackles, Security Fasteners, and Self Drilling Screws are all commonly case hardened. The method of case hardening used in the video is also known as carburizing with a cryogenic treatment. Liquid nitrogen is usually used but I used a isopropyl alcohol dry ice bath. Liquid nitrogen would provide even more benefits by converting even more retained austenite to martensite. Also, if you don't mind the darkness of the part after the hardening process, it's best not to polish it for even more rust protection. The method used in the video can be repeated multiple times until the desired hardness is achieved.

Induction is particularly good at case hardening. This is because of the skin effect discussed in the next step. The same high frequency skin depth that is seen in the working coil is also seen in the part being heated. The higher the frequency, the more the current is flowing on the outside of the material. For steel in this case, the current is only flowing about 6 thousandths of an inch deep. This is perfect for case hardening.

This process should only be used with low carbon steel so I'll show you a way to determine what type of steel you have.

In this video, I'll show you an easy way to determine the carbon content of your steel parts by observing the spark profiles. You can use this technique to find which of your parts would benefit from the case hardening method used in my last video. This is not the most accurate way of determining the composition of the steel, but many welders use this technique when welding unknown materials and is a good test for most non-critical jobs. This technique is known as spark testing.

Step 2: Induction Cooktop

In this video, I make a pancake coil attachment and boil water in about 10 seconds. It works by pulsing the DC at a high frequency(about 160kHz). This creates a constantly changing magnetic field that induces eddy currents in the cast iron skillet. Induction heating is more efficient than many other methods because there is less wasted heat. For example, induction cooktops are more efficient than electric and gas stoves.

The use of my wire choice is quite important here. I used what is known as Litz wire. Litz wire consists of many individually insulated wires. It is the preferred wire for use in high frequency application due to the skin effect.

The skin effect is the tendency of current to flow on the outside of a conductor at high frequencies. The higher the frequency, the shallower the skin depth will be. Using Litz wire will result in much more efficient working coils for your system. Not only does it transfer the energy more efficiently, it also generates less heat of its own. If you have 10amps flowing through 260 strand Litz wire, that's only 38mA of current in each wire. 10amps through a single conductor will generate substantial heat depending on the size.

If you do not want to use Litz wire, the next best thing is copper tubing. It has more surface area for the current to flow so it is more efficient than an equivalently sized solid core wire.

Step 3: Induction Kiln for Melting Metals

In this video, I melt the first pieces of aluminum in my 1000W inductive furnace attachment with my graphite crucible. It works by pulsing the DC at a high frequency. This creates a constantly changing magnetic field that induces eddy currents in the graphite crucible. Graphite makes for a great susceptor because of it's ability to absorb electromagnetic fields and convert them to heat. That's why it's used in many crisper sleeve for microwavable foods. A susceptor is a material that is used for its ability to absorb electromagnetic energy and convert it to heat.

Step 4: Induction Solder Pot

In this video, I explain the material choices I made for my 1000W induction solder pot. I used a steel conduit coupler with a steel plug wrapped with aerogel infused fiberglass exhaust wrap. I made the working coil with litz wire and secured it in place with kapton tape. For an even better solder pot, you could use a graphite crucible like in the last step. In this next video, I show you how to use the solder pot. I feel it really demonstrates the usefulness of the solder pot.

Step 5: Loosening Seized Bolts and Hardware

A torch is commonly used when you can't loosen a seized nut or bolt. By heating the nut with the induction heater, the metal will expand and you can free the seized hardware. Using a torch is dangerous in confined areas and using flameless heat prevents damage to the surrounding parts such as, wire harnesses, fuel lines, anything plastic, anything volatile and flammable. Induction heaters are often used by aircraft mechanics when using a flame would be a bad idea.

Step 6: Induction Levitation

In this video, you can see that the coil is levitating the aluminum. The works because of Lenz's law. This means that when it is introduced to a constantly changing magnetic field, the induced currents in the aluminum create an opposing field to that of the coil. This is the same thing that is happening when you drop a strong magnet down a copper pipe. The magnet is slowed down due to the opposing field that the copper is producing.

Step 7: Battery Powered!

In this video, I test a 16.8V, 33.6V and 50V battery pack for the induction heater. This could be used as a portable induction machine for use with any of the above applications.

Step 8: How to Make One

Minimum Materials You Will Need:

1. Adjustable Power supply or battery pack.

2. ZVS Driver with coil

You can get by with just those parts but I recommend using Litz wire and a power meter as well as some protective equipment. Here are some links to recommended equipment for this project:

ZVS Driverhttp://amzn.to/1NqHSaw

Meanwell RSP-1000-48 Power Supply http://amzn.to/1NqHOYz

4S Quadcopter Batterieshttp://amzn.to/1PqNWSz

Litz Wire for Custom Induction Coils http://amzn.to/1kIG6IA

Graphite Crucible http://amzn.to/1Mdj34M

Temperature Meter 2000F(1300C) http://amzn.to/1NqHV6j

Power Meter 100V 50A http://amzn.to/1XnFMNv

Cast Iron Mini Skillet http://amzn.to/1MfaT5y

Aerosol Fire Extinguisher http://amzn.to/1NwFLlx

Bullet Connectors http://amzn.to/1MfaYX7

Fiberglass Exhaust Wrap http://amzn.to/1kIxt0K

XT-60 Battery Connectors http://amzn.to/1Hvb23H

Battery Cell Monitor http://amzn.to/1kxxi81

Heat Resistant Gloves http://amzn.to/20K3xBP

Assembly is as simple as connecting the +terminal of your power supply to the +terminal of the ZVS driver and the -terminal of your power supply to the -terminal of the ZVS driver. The polarity of the working coil does not matter. I recommend an adjustable power supply and using a power meter to give you better control on your heat output.

Step 9: How Does It Work?

This induction heater works by pulsing the DC at a high frequency(about 160kHz). This creates a constantly changing magnetic field that induces eddy currents in conductive materials near the coil. Ferromagnetic materials will also heat up due to hysteresis. This is the heat produced from rapidly changing magnetic fields in the material. Induction heating is more efficient than many other methods because there is less wasted heat. For example, induction cooktops are more efficient than electric and gas stoves. I'll be making more attachments and demonstrating more practical uses for inductive heat.

It's a common misconception that induction heaters don't work for aluminum and other non-ferrous metals. This is not true. This induction heater will heat up aluminum and copper just fine, but not as fast as ferrous metals. This is mainly due to their lower resistivity. The higher the resistivity of the conductive material, the more it generates heat when current is passed through it. The higher resistivity of most ferrous metals coupled with the heating due to hysteresis makes them ideal for induction heating, but they are not the only metals affected by induction.

The three main components of the machine are the power supply, the ZVS driver, and the working coil. The ZVS driver,(Zero Voltage Switching) was invented by Vladmiro Mazilli. It uses resonant zero voltage switching (also know as ZVS) to pulse the power supply very rapidly. This means the MOSFET's are designed to switch (on or off) when the voltage across them becomes zero. Since the MOSFET's switch when there is no voltage across them, they generate very little heat. The main source of heat is caused by the MOSFET's internal resistance and the capacitors constantly charging and discharging. The circuit is fairly simple consists of just two MOSFETs, 6 capacitors, and a few resistors and diodes. You can build the circuit yourself, but it is cheaper to buy a premade board.

Step 10: Thank You

Another great application would be to use it in a tankless water heater. A coil could be placed around the pipe and heat up the water as it passes through. This machine could also be used for wireless charging and powering applications.

Thank you for reading my instructable. I spent a great deal of time on this inductive heating series so I would really appreciate you sharing this with your friends as well as voting for me in the Epilog contest above. I if had a laser cutter it would help me create more educational content for you guys.

Thank you,

Anthony - Proto G

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First Prize in the
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2 People Made This Project!

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134 Discussions

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BartF10

Question 6 months ago on Step 10

Ive got a 12v to 48v induction heater system from ebay with a 70mm diameter coil wich is about 10cm long. I want to replace that coil for a longer one of around 20cm long. Will this still work or do i need to change something? Thx for your help

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twestheimer

10 months ago

Great instructible ! We are in Thailand and it gets cold in the winter 30-40 F . Not like the US but there are no heaters in rooms or cars. In our room we have an induction hot plate. Any suggestions on a "hack" to use it as a temporary heater? Boiling water makes the room too humid :-( I was thinking of putting rocks etc in a pot? Any suggestions would be appreciated!

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manicmonday

3 years ago

I challenge you to make an induction coil that will sweat copper plumbing fittings inside of a wall. Normally when a copper repair has to be done it is sweated using a propane torch that CAN cause heat damage to fiberglass bathtubs and in extreme cases can burn down a house. Is it possible that induction could be a safe and workable alternative to propane heat for copper plumbing repair?

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Kevanf1manicmonday

Reply 3 years ago

I think I would look at using one of those clamp type, electrically heated soldering irons for that job if there was a risk of fire. I'm sorry I am not sure what they are actually called but the main part of the tool opens up on a hinge and then it is wrapped around the copper fitting. There are different sizes for different fittings - 15mm, 22mm and 28mm (not sure about the old imperial equivalents). No flame, very low possibility of a fire. Though, to be honest I don't remember using a soldered fitting on a bathtub anywhere near where it would be a problem. When I was a plumber I always used compression fittings :)

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Proto GKevanf1

Reply 3 years ago

What you're reffering to is a resistance soldering machine. I have one and they do work well.

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Kevanf1Proto G

Reply 3 years ago

Nope, sorry I think we are talking about different machines here :( The ones I mean are a proper electric soldering iron with a heated tip. It's just that the tip is not a tip as in a normal soldering iron but a round attachment that fits onto what are essentially insulated pliers.

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Proto GKevanf1

Reply 3 years ago

Are you sure? See this video:

That is a resistance soldering machine.

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Kevanf1Proto G

Reply 3 years ago

Sorry no that is not the same as the tools I have seen. It looks very similar to the way a spot welder works. The tools I have seen actually heat all around the fitting enabling it to be soldered just like using a butane/propane/MAPP gas torch. Got to say, that pipe seems to get a lot hotter than when I solder a pipe. But, if it is actually being brazed as opposed to soldered then it would have to be significantly hotter. I have never come across a situation where a copper pipe and fittings would need to be brazed in a domestic situation. Maybe for industrial use?

Some interesting differences on how plumbing work is done here (UK) and in the USA :) Another one, totally unrelated to this thread is the use of a flexible 'doughnut' when installing a toilet cistern onto the bowl. It is very different to how we do it. The closest is for a close coupled suite.

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maddscienceKevanf1

Reply 1 year ago

Copper pipe needs to be brazed when used for an oxygen line; silver brazing works well. The fluxes from normal soldering are flammable.

Brazing of copper is also useful when using dissimilar metals, such as joining SS fittings.

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Proto GKevanf1

Reply 3 years ago

That video I just posted works exactly how a spot welder works; with resistance. It pumps high current through the metal to heat it up. It may not be that same brand or model but those machines have many attachments and they work the same as a spot welder.

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W0nkyProto G

Reply 3 years ago

This is a common heating tool for soldering copper pipes.

image.jpgimage.jpg
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Proto GW0nky

Reply 3 years ago

I know what it is. It's a resistance soldering tool. I have one. It works the same as the video I posted.

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manicmondayKevanf1

Reply 3 years ago

Never heard of the soldering tool you mentioned. Also never heard of a plumber using compression fittings for anything inside of a wall. When copper fails it's due to corrosion which would attack compression fittings more than sweated fittings. The newer product is an expandable memory plastic tubing called worsbo (I'm sure I've spelled that wrong), but I'm talking about repair because many older homes still have copper, and access it tight and difficult with repairs

But these differences are explained due to the big pond between us. I"m in America, and your use of metric measurements shows that you are not. I do think it's stupid for America to not use the metric system which is obviously much better than ours. The older people that are in charge are used to the old system and are unwilling to change.

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my wookiemanicmonday

Reply 3 years ago

im a sort of "apprentice" on a maintenance team at a dairy my "master" is an industrial plumber, they ultimately learn to work around that stuff with a torch but usually we use a thing called pro press ( https://www.ridgid.com/ph/en/pressing-technology ) just did a big project last year, had a couple of guys with a torch and one guy with the pro press, it did twice as many fittings with no leaks and the torch guys had 15 leaks

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Kevanf1my wookie

Reply 3 years ago

Now that's interesting 'my wookie'. I take it these 'Pro Press' tools somehow squeeze the pipes/fittings together? They look exactly the same as the heated soldering tools I have seen. Or are they also a soldering tool? If so then that technology has come along a fair way since I last looked at it.

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my wookieKevanf1

Reply 3 years ago

nope these just squeese it together

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Kevanf1my wookie

Reply 2 years ago

Hmm, now I have never seen or heard of this type of tool :) We both learn something then. Good talking to you :)

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Kevanf1manicmonday

Reply 3 years ago

I've used compression inside what you would term a rockwall faced hollow wall. We call rockwall 'plasterboard. For a bath I have always used compression fittings to attach to the taps and then usually there is enough distance in the pipework to be able to use soldered fitting for the main runs of pipe. We have started to use more plastic fittings for both cold and now hot water systems here. I presume you have push fit in 1/2", 3/4" etc? It certainly makes plumbing a house a lot, lot faster than the old copper pipe route. Mind you, there are push fittings for copper too as I have used them. In fact it's a good job I have the old lead pipe skills still. We have lead in parts of our house :) I've had to join copper to lead in a few places... Thankfully not drinking water outlets.

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manicmondayKevanf1

Reply 3 years ago

We use lead free for all plumbing. I also enjoy electronics and they are trying to restrict that to lead free and that is BS.

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Kevanf1manicmonday

Reply 3 years ago

They have pretty much eliminated lead in solder over here too. I honestly don't have a problem with the lead free stuff. Clean the joints, flux them and heat and then let the solder run :) The lead I referred to was actual lead pipe. Our house is over 100 years old and this is from when it was first built. As I said though it is outside terminating in a garden tap not an indoor one :)