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@ Tommy ... I haven't seen the plans for the DIY heater, but if it is modular it may be possible to fit some of the parts to your heater. Your power supply is functioning. It may be that all yours needs is to replace the control circuits. I'll have to promote this thread to a start page... :>)

 

paul

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Hi, John DeArmond here. Chief Engineer of Fluxeon. I agree with your advice that the Roy is not a suitable forging heater for anything but the smallest items. While it will "hold up", it simply wo

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I too have one of Grants machines that has croaked. If you find them fixable please contact me. Would be happy to sell it as is too.

Tommy, it may be. However those machines have a lot of discreet components so trouble shooting would be a challenge. I might be interested in fixing it for you just to establish a benchmark on the level of repair complexity and rate of failure in commercial units. I'm not really interested in owning a commercial unit when I'm making my own. PM me if you would like to discuss it, I would do parts only and estimate before replacing anything major.

 

 

That is really an awesome project so far! I appreciate your work and looking forward to building one when it's available. One question i have is, will it be possible to control the Induction Heater with a computer? Like sending commands to it via Matlab to change power or to receive actual and target values for power, current and voltage?

 

Thank you very much in advance!

Yes, I am doing that already. There is a bluetooth module in this one that was communicating with a Processing application to log data and graph it as well. I don't use that application to send commands much anymore since the hardware user interface is working, but the layer is there if it's needed. 

 

 

that is really impressive, it is good to see what can be done at lower power levels as in some parts of the world it is very hard to get a 200 amp supply.

thank you for the update on this and looking forward to more news soon.

iron d, This unit runs on 240 Volts and can be set to use as much or little current as you can safely deliver (up to about 100A). In the video the current never peeked above 34 amps which is on par with an electric cloths dryer or a welder and would be the typical operating range for the final product. It could be easily modified to run on 120 Volts and still performs very well. I run it on 120V often when I'm testing new code. I know I you haven't seen it yet but I have plans for a 120 Volt version that uses power equivalent to a personal space heater (1400-1800Watts).

 

 

In the video below I wired a custom, high current 65A circuit in Daniel's old shop (not typical for a 220/240V single phase circuit). This was the first version that operated standalone and did not have current limiting capability beyond the preset matching transformer ratio. Wide open it would suck about 85A so he had to be carful not to run it without a load. Daniel did not have access to 3 phase power which was the reason for needing high current. Since then I have made improvements that allow the forge to make better use of the low end power (when the work piece is cold) and control the current once the piece is heated up sort of like shifting gears. This current control also allows you to use the forge on any circuit and set the maximum current to not exceed what the outlet can provide.

 

https://www.youtube.com/watch?v=fOJRu9ayc24

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If you are still interested in a wrap for your coil. 3M nextel 440 sleeving.  Not sure about its insulating properties, but working with it now developing a gasforge application and it handles the heat well (rated for 2500F continuous).   Saw it an one link for it at about 0.77 per inch. i'm sure you can find it cheaper if searching for quantity.  Not good for copper at heat,but your coil should never be at that heat(would not recommend forging copper inside).  Looking forward to your kickstarter.

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Found some on Alibaba that appears to have better performance than fiberglass sleeving. It's made of amorphous silica not Alumina-Borica-Silica like the 3M stuff but still better than the cheap glass. It's only sold in bulk obviously, which is what I was looking for anyway. 

 

Good quality high silica sleevings

"Our High silica sleeving is composed of continuous filaments of amorphous silica, the materials are capable of operating continuously at 1000ºC and at up to 1600ºC for limited periods, they will not melt or vaporize until temperature exceeds 1700ºC, and have a high resistance to thermal shock."

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can you use 1mm ceramic paper ?

Absolutely, rolled up and inserted into the coil or just covering the bottom half of the coil so the work piece can rest on it if you have a horizontal work coil. I have some ceramic fiber paper that I got to try just that. 

 

Like this:

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It is great to see some activity here, I am now more hopeful of seeing something avaliable this summer maybe.

 

have heard on another IH discussion about changes in the tank when steel reaches the curie point as it becomes non magnetic, as this is a point which is very useful to smiths can the changes easily be detected and used to get metal that hot and stop there before it burns

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You can use fibreglass woven sleeving. I use this:
http://www.mcmaster.com/#sleeving-insulation/=scinyf

Once you cover the coil, it needs to be stretched tight, and then coated with sodium silicate (water glass). This hardens the wrap to a rock like surface, it's less than a buck per foot, and holds up well.

The silicone fibreglass that I use, sized for 1/4" tube, also works well, but is affected by the radiant heat... after 7 years my original coil is pretty tattered, but still functions. This is quicker, but does not stand up as well as the coated fibreglass sleeving, buts its a lot quicker... kind of fits with the idea of induction heating... I have no patience :>)

paul

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the ceramic paper alway ends up sticking to the piece that i'm heating...  i found it to be annoying

 

if you do lots of forgewelding .. ( like i do )  then i don't see the fiberglass holding up for long ...    just have to have a steady hand to hold the sucker

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It is great to see some activity here, I am now more hopeful of seeing something avaliable this summer maybe.

 

have heard on another IH discussion about changes in the tank when steel reaches the curie point as it becomes non magnetic, as this is a point which is very useful to smiths can the changes easily be detected and used to get metal that hot and stop there before it burns

Iron Dwarf,

Yes you are correct once carbon steel reaches 1200℉ to 1400℉ depending on the makeup it will become austenitic and loses its magnetic properties. The short answer to your question is yes, one of the items in the design goals is to develop a low cost automatic optical pyrometer for measuring and feeding back temperature data to the forge for the purpose of controlled heating applications. The control board already accepts such input and I have the parts and theory worked out for the pyrometer. If that doesn't work out you can use a thermocouple. Which would also be useful for temperatures below the point at which black-body radiation emissions are in the visible wavelength. Unless I also couple it with infrared detection for that range, lots of ideas floating around that right now but there are to many other things to focus on for the time being to get into that. The forge will have an input to accept control from such devices.

 

 

You can use fibreglass woven sleeving. I use this:
http://www.mcmaster.com/#sleeving-insulation/=scinyf

Once you cover the coil, it needs to be stretched tight, and then coated with sodium silicate (water glass). This hardens the wrap to a rock like surface, it's less than a buck per foot, and holds up well.

The silicone fibreglass that I use, sized for 1/4" tube, also works well, but is affected by the radiant heat... after 7 years my original coil is pretty tattered, but still functions. This is quicker, but does not stand up as well as the coated fibreglass sleeving, buts its a lot quicker... kind of fits with the idea of induction heating... I have no patience :>)

paul

Brilliant, I'll have to try that. Isn't sodium silicate an intumescent (swells in heat), pretty sure I remember it from a product or experiment that expanded with heat. Either way like you said it really should only need to stand up to radiant heat and occasional momentary contact. And getting the fiberglass sleeve to slick down to the tube would help a lot. It seems to want to bunch up and separate from the tube then when a red hot work piece touches it with no copper behind it to keep it cool it melts instantly. Did you come up with that or is it a common solution (in certain circles)?

 

 

the ceramic paper alway ends up sticking to the piece that i'm heating...  i found it to be annoying

 

if you do lots of forgewelding .. ( like i do )  then i don't see the fiberglass holding up for long ...    just have to have a steady hand to hold the sucker

Yes it does, I had to scrape it off that bar with a razor which is not good because the little fibers float up if the bar is still hot right into your face. It's not asbestos but it's still a dangerous particulate. And as you indicated, it is a one time use thing. After heating it because brittle and breaks down into individual short fibers.

 

In a way the whole point is a bit moot because the forge can detect and deal with shorts. In fact, I was using a copper bar to short out turns in a large coil the other day to focus the power down to a smaller area. It automatically retunes to the new resonant frequency and continues to operate as long as all other parameters are within limits (current, temperature etc). I just don't like the sparks, they make you jump and could cause you to drop the work piece.

 

I've got a coil with baked on Rust-Oleum 2K℉ heat resistant paint I'm going to put through the ringer. We'll see how it holds up, not getting my hopes up. If I use a coating of any type, heat resistant or not I think it needs to be pretty thick to stand up against the mechanical stress of metal hitting it constantly. 

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suggested the tank monitoring for the curie point as it would be difficult to optically  measure very high temps or so I have heard.

( more important to get the thing avaliable and maybe do upgrades and add ons later IMO but whilst waiting ideas can be thrown around to be considered or discarded )

 

maybe other things to try as a coating.....

 

 

sodium silicate with or without  vermiculite dust, if it can be just dipped and then heated it could be easily re applied when needed

 

Refractory use

Water glass is a useful binder of solids, such as vermiculite and perlite. When blended with the aforementioned lightweight aggregates, water glass can be used to make hard, high-temperature insulation boards used for refractories, passive fire protection and high temperature insulations, such as moulded pipe insulation applications. When mixed with finely divided mineral powders, such as vermiculite dust (which is common scrap from the exfoliation process), one can produce high temperature adhesives. The intumescence disappears in the presence of finely divided mineral dust, whereby the waterglass becomes a mere matrix. Waterglass is inexpensive and abundantly available, which makes its use popular in many refractory applications.
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So in talking about temperature I wanted to demonstrate how easily one can control the temperature of the workpiece using induction heating, even manually by adjusting the power slowly. I thought tempering would be a good application for this since the results are apparent and well known, it's also something that has always fascinated me.

 

Application: Tempering

 

I cut 5 pieces of 1018 1/2" bar stock into 1/4" slugs.

 
Each piece was heated to an exact temperature by measurement with an infrared thermometer and visual inspection of workpiece color.
 
Power was controlled manually and heating starts at the low end. This allowed me to increase the temperature of the workpiece by only a few degrees per-second, allowing uniform heating of the entire piece and enabling me to stop the instant it reached the target temperature. 

 

I added two more slugs, one for control color which was not heated and one to show heating just beyond the tempering range of this material. Tempering temperatures vary with the composition of the workpiece and the specific application but the temperatures below are what I found to be most common in the documentation available on the subject (not an expert in this area so I could be off). Beyond about 620℉ the workpiece begins to turn grey and lose the temper or normalize as it approaches the annealing temperature at which point any tempering and or hardening of the workpiece is lost.

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cool

 

but be aware that tempering requires time at that specific temperature ...    eg) when making knives i'll temper at 450 F for 2hrs ...   cool to room temp...  and repeat

 

a short duration tempering is not something i'd ever trust

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cool

 

but be aware that tempering requires time at that specific temperature ...    eg) when making knives i'll temper at 450 F for 2hrs ...   cool to room temp...  and repeat

 

a short duration tempering is not something i'd ever trust

Greg,

Your right, I was talking to Daniel about that last night. Later I'm going to experiment with wrapping flexible litz wire around work piece, affixing a thermocouple or two and wrapping the whole thing with insulation. I found that even when treating items this large (1.5" square x 4") the IH requires very little power to heat the work piece up to the tempering range. Pulling only 1Kw I was able to reach a stable 500℉+ range very quickly. In practice I would assume you probably want to reach that point slower to ensure uniformity, which lowers the power requirements even more. The litz wire works great at these low power levels, and the heat generated by in work coil just adds to the efficiency since normally the heat generated in the work coil is carried away by the cooling water. 

 

 

It would be trivial in software to write a control loop with a two input parameters target temperature, and holding time at the target temperature. You could keep of course going and add parameters such as speed of initial heat, slower cooling times by ramping down the power/duty cycle and even program specific temperature curve vs time profiles. 

 

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Thank you very much for your fast reply Josh. Being able to send commands sounds awesome! Another question I have is, will it be possible to add and remove capacitors to change the frequency?

 

Best wishes

Yes you can. As I'm sure you're already aware, changing the capacitor value or the inductance value of the work coil will change the resonant frequency. The controller can support a range of zero to about 160KHz, the driver I'm currently using works up to about 125KHz and the IGBT's range varies depending on model (minimum = 1/ton+tr+toff+tf). The ones I am using right now work great up to between 95 and 110KHz depending on dead time.

 

I don't think you will need to add or remove caps to change the frequency

Your right, the frequency can be set manually but the natural resonant frequency is determined by the capacitor and inductor value. You want to operate at or near resonance to transfer full power to the load.

 

That being said, there are a few different topologies for the high power section that also effect frequency. Some are more conducive to changing the resonant frequency easily. We have not 100% settled on one as their are pros and cons to them all. 

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