Induction Melting Furnaces for The Hobbyist

a bit unrelated, but I got to see an induction hardening system in a Rockwell plant where they were making ring and pinions for semi trucks. The pinion had cross sections in the 3-4" area. The coil looked like a electricians fish tape that lowered over the pinion and changed power at each surface (bearings, seal, splines, etc) and sprayed coolant as it went according the the heat treat desired. The whole cycle took maybe 10 seconds, and you could hear when something went wrong in the cycle. A couple of times I was quick enough to look over and see that pinion turn yellow hot and fall out of the centers. It was fed by 440vac 3 phase, and each phase had a 100A breaker. Mostly ran around 10kHz, but varied for different sections of the part. Manly machine.

 

Kelly,

I looked at what is probably best described as a melting system that you have on Youtube. Really nice job. All I can say is I wish we had a guy like you on the team at work!!

When referring to "cheap induction heaters on eBay" meant to say orange and blue not orange and yellow (that's the furnace temperature thinking!). They're junk.

You aren't kidding when you say it's getting pretty sporty...lots of amps. The electrical engineering behind running that on homeowner/residential service is beyond me. Tim Williams would know what best to do. He used to be on all the metal casting fora way back when, now I believe he designs induction systems for a living. I'm guessing single phase would be the problem.

I think 60 lbs of aluminum (or bronze) would easily be manageable in the 35-50 kW delivered range.

 

Melting aluminum, bronze or copper can even be done in a slower resistance furnace, as long you use proper Kanthal A1 grade wires / elements. Chamber and crucible temperature can reach 1250 C.

 

For my cook top I know it is more efficient............but that is apples and pineapples. Our resistive units have the advantage of insulation that my cook top doesn't. There may still be a slight advantage but for the few electrons saved I'm thinking you would have to do some very precise experimenting to find/prove the difference.

400 amp service is even more expensive to install with the 2020 NEC. That means 2 200A disconnects at the meter now. Parts, in my part of the world, are "Not in stock. On back order". Same for new 200A service.

 

It is funny how all of us hobbyists like induction furnaces. Because over the last six months I have done tons of research on them. And I didn't find a lot but I kept my eyes peeled and found this video the other day. In my opinion, it is really really cool.

Patrick

 

Okay, well the principles are there. And I think with some modification it would work fine. I also think it is helpful that he does have all of the parts listed. When I get a little ahead I will try that build and see how it works. I just found it to be the most informative induction project I have seen to date, which after tons of searching I found pretty cool.

Patrick

 

Yeah, but importing is not that easy nowadays. So in the long run I think it would be cheaper to build it, and then another plus is knowing your machine inside out.
Patrick

 

Indeed, Backyard Scientist is more a Youtube star, but his experiments are really cool (or hot!) !
For me, an induction furnace is still out of reach, as the cheaper ones (< $1000) on ebay are crappy and are usually not protected against overloading, with frying the Mosfets as a result. Moreover, these small units don't get hotter than resistance furnace or a fuel fired furnace.
When I really need high temperatures (> 1500 C) I still use my DC welder and then for small quantities only (e.g. making synthetic rubies or melting stainless steel).
The really nice ones of which e.g Lou tells which allow melting Platinum, are brutally expensive for hobbyists as they are for commercial use.

 

I am not sure how much you know about building induction furnaces so I will give you some tips that I wish I knew before I tried to build one. The power supply (inverter) and the heating coil which surrounds the crucible need to be matched. To give you a real world example, using a electric motor to drive a load with a mismatched transmission will stall the motor. The electric motor is the inverter and the transmission is the heating coil. The only difference between the motor and the inverter is the inverter will not tolerate overloads but an electric motor will run with an overload a lot longer than a inverter. If you can get a old induction cook top and take the cover of and see how many turns of copper wire are on the heating coil. Then make another heating coil with six turns for a small crucible and connect it up to the induction cook top power supply. Two things can happen, you will destroy the inverter or a inbuilt circuit breaker will trip and shut the cooker down before the inverter is destroyed. Frequency and voltage control the number of turns and the size of the coils. If you want learn about building induction heaters I made two videos about the subject, the first video is about modifying a inverter microwave to make a simple induction furnace. the second video shows how to test large I.G.B.T. transistors which are perfect for high power induction furnaces. Induction cook tops and inverter microwaves are great places to start to understand how induction heating works.

 

Have you talked with Steven Maxx of Maxx casting in Kalona, Iowa? He uses an induction furnace mostly for bronze and occasionally for iron. His crucibles are large. His website shows two just outside his front door.

 

I think you mean Steven Maxon. I have a feeling Spellcheck may have “helped” you here

https://max-cast.com/

 

I was reacting to your 'wish' and thinking be careful of what you wish for.
Installing a permanent power source feed for an adequate induction furnace for hobby purposes is probably more costly than can be justified even if possible. Given that most of your time is spent preparing the molds and that melting and casting is pretty quick, I think that renting a generator to power the furnace might be a viable plan. A 1,000 kW, three phase generator fits on a 40' trailer.

 

Thousand kilowatts ? What are you going to cast ? That looks more like an industrial setup...

 

Don’t even bother now with induction no electronics in sale for this kind of setup. Most out of stock. With war raging in Europe and china preparing a new one it will be a while till new components will be available to the open market . Even if you manage to get them think about spare parts.