gold melting furnace to recommend

ok, i've finally decided to get a gold melting furnace, either putting inside the shop or my home to melt scrap we buy at the shop. Any recommendations for something compact, yet doesn't take forever to heat up? Does furnace need good ventilation? Does furnish have any chance of explosion? that's my biggest fear as shop has inventory. need something doesn't take forever to heat up and commercial grade as we buy scrap. What size melts are you looking at doing? Up to about 15 ounces can easily be done in a melting dish with a torch and it is very quick. It will also melt Platinum, which gas furnaces will not.
And a good positive ventilation is necessary.

What size melts are you looking at doing? Up to about 15 ounces can easily be done in a melting dish with a torch and it is very quick. It will also melt Platinum, which gas furnaces will not.
And a good positive ventilation is necessary.

what you think of this kind https://www.amazon.com/Melting-Auto...44-79bb02bd9f8f&ref_=pd_gw_ci_mcx_mr_hp_atf_m I have never seen one of those 1 kilo hand pour furnaces last. I have never bought one but I have been given 3 by clients who did not like them and I used them a few times until they just burned up, all 3 of them. There are some propane gas furnaces on amazon that are less costly and will last a long time.
https://www.amazon.com/Masters-Prop...ocphy=&hvtargid=pla-&psc=1

I am not a big fan of the insulating wool used on these furnaces and would suggest replacing it when it wears out with a refractory castable cement. But the light weight of the refractory wool make it affordable to ship over here (probably from China) but would be high on my first thing to improve list.

ok, i've finally decided to get a gold melting furnace, either putting inside the shop or my home to melt scrap we buy at the shop. Any recommendations for something compact, yet doesn't take forever to heat up? Does furnace need good ventilation? Does furnish have any chance of explosion? that's my biggest fear as shop has inventory. need something doesn't take forever to heat up and commercial grade as we buy scrap.

Hi,

If you want a safe and secure furnace for melting, which is fast and doesnt take forever, you should search for Induction melting furnace. They come in all shape, power and sizes. For larger quantities (approx 1kg gold) you should look for a 4-5 kW up to 10kW power furnace (you will not necessarily use it at maximum power, but should you consider a bigger melt later on, you will have sufficient reserve power to do that).

I hope this helps.

Pete

Hi,

If you want a safe and secure furnace for melting, which is fast and doesnt take forever, you should search for Induction melting furnace. They come in all shape, power and sizes. For larger quantities (approx 1kg gold) you should look for a 4-5 kW up to 10kW power furnace (you will not necessarily use it at maximum power, but should you consider a bigger melt later on, you will have sufficient reserve power to do that).

I hope this helps.

Pete

Pete,
you mean induction technology corporation as in Lift & Swing Melting Furnaces - Induction Technology Corp.

Pete,
you mean induction technology corporation as in Lift & Swing Melting Furnaces - Induction Technology Corp.

Whatever design or manufacturer you like. There are many manufacturers world wide, some expensive some cheaper and there are the chinese ones (disadvantage for these machines is the poor service and spare part supply). The positive side of this technology, is the high efficiency, low operation cost.

That's sort of what I suspected. You don't get something for nothing and you cant put 15kw of power into a melt when you're only pulling half that much out of the electrical service.

My problem is I melt up to 60lbs of AL in an A60. It used to be that an A10 covered 90 % of my melts but now it's often A20 and up. With a low power induction system, it's hard to get a coil around those crucibles let alone with a coil those systems could handle. I figure realistically I need a real 25-50kw induction system, but am stuck with low voltage residential power 240vac single phase and that would eat my entire 200 amp service. I could get higher power service but even so, the current is getting a bit sporty for that voltage and 480 3ph just isn't happening residentially.

Resistive electric is slow(er), and I can manage that but being limited to aluminum our bronze at the fringe is a bummer. The cost of the imports don't bother me but they're really not melting systems. I'd love to have a real induction Power Supply and furnace but can't justify it pricewise and couldn't power it if someone gave it to me. Sooooo, here I am.

Best,
Kelly

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.

Thanks Lou, wish I had commercial melting equipment and the knowledge to properly use it.....

Agreed, but here's what that means with residential 240vac single phase power.........208 amps! Now I could have a 400 amp service installed, at a cost, but after all, the utilities are in the business of selling electricity, and they will, BUT, that would require very large conductor and not practical. Now I could step that up with a pricey transformer, and maybe even use an RPC to have 480 3ph, but that would require a very high investment, and I still don't have an induction melter. That kind of power really doesn't belong on a portable power cord.

The other problem I have, my equipment needs to be portable or at least on wheels. Even if I had the space to permanently dedicate, which I don't, it's not the right kind of space for such a piece of equipment because it's a 9ft ceiling with 24'x24' drywall stick construction with a lot of other stuff in there and fire hazard would be just too high. If I had a pole barn, at least this part would be different.

With only ambitions of Al, Cu, and Fe alloys, all I really have to gain is speed of melt and iron capability. There have been remarks about induction being more efficient than resistive elective, but I don't think it is........faster yes, but 4x the power to melt in 1/4 the time is the same energy consumed. Resistance heating is very efficient and clean. Alas, a fuel fired furnace is much more practical choice given all of the above........ . As a caster I still have induction envy.

Best,
Kelly

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 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.

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 (< $) 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 (> 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.