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2:31 pm
May 13, 2010
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I would think for a lot of things doing things in stages makes a lot of sense I often work that way using gas and coal. But for the odd job where you need to reheat a shape that has changed quite a bit I think I have seen some pictures on the net(Grant's I think) where there are two different coils formed in the same piece of tubing. You probably lose some efficiency but you probably gain it back in retained heat in the steel and work flow.
3:16 pm
June 16, 2010
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Very hot/cool!
I was wondering, what should your shop conditions be like before installing one of these units? Being that these have extensive electronics, should the shop be fairly dust/smoke free? Should you keep grinding activities to a minimum around the induction unit? Should the ambient temperatures in the shop be fairly consistent?
I can't imagine it would be very wise to store/use it in an unheated shop at -30. I guess -30 would also mess with your water cooling system too.
3:24 pm
June 9, 2010
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Here's another coil building resource.
http://www.ameritherm.com/PDFs.....design.pdf
And here is a thread where Dr. Sarver lays out how to form a pancake coil.
http://forums.dfoggknives.com/.....#038;st=60
I think you hit on the only downfall of the unit, switching the coils. I also remember seeing a coil that had two round sizes rolled in sequence that looked useful.
3:28 pm
June 9, 2010
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I can't imagine it would be very wise to store/use it in an unheated shop at -30. I guess -30 would also mess with your water cooling system too.
I had mine in an unheated shop in a cold winter and everything was ok. I used antifreeze in the cooler.
4:51 pm
March 26, 2010
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Mike B;2098 wrote: You could use a water-water heat exchanger. For example, circulate antifreeze through the heater and a coil, then submerge the coil in a bucket with tap water circulating through it. Not sure why you'd want to, though, except maybe as a way to get the waste heat out of the shop.
Hey Mike, I LIKE that idea. My slack tub has got an overflow running of to the drains and a hose/tap to fill it. It allows me to spray water over big bits of steel I want to cool in a hurry and I don't have to carry buckets of water to fill it (I also use the hose to top up the bosch on my water cooled coal forge)
I guess what I should do (till I find time (if ever) to build a big cooler) is use my little TIG water cooler as a closed loop with antifreeze in it but take the return (supply?) pipe through a large matrix/coil of copper tube that sits at the bottom of my slack tub. If it's big enough bore it wont affect the flow of the cooler.
When I'm using the induction heater intermitantly the TIG cooler and slack tub will take out enough heat but when I want to cane the heater I turn the tap on that fills up the slack tup The slack tub acts as a (big) heat exchanger and takes away a lot of heat. As an added bonus, it takes it out of the workshop.
Because of the business of cold water sinking, hot rising, the bottom of the slack tub is the best place for it and it wont take up too much space interfer with the slack tub.
I DO like this idea, there's already pump in the TIG cooler, the slack tub and fill/overflow is already there in my workshop so I'm not loosing anymore (very valuable) space. All it takes is coil of copper tubing and one extra pipe in the circuit. I don't have to worry about things freezing. When I'm only using interemittantly I won't be wasting water. When I do turn on the tap, I'll feel a little green guilt but hell golf course and lawn hose pipes waste a LOT more water.
Aren't forums great ways of exchanging info. Thanks Mike.
5:04 pm
March 26, 2010
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JNewman;2101 wrote: I have seen some pictures on the net(Grant's I think) where there are two different coils formed in the same piece of tubing. You probably lose some efficiency but you probably gain it back in retained heat in the steel and work flow.
John, yeah seen it and will play around with it. I was always under the impression that very tight coupling (close hugging coil) was needed but playing around the the 50mm diameter coil, I find this will heat small stock such as 12mm. A bit slower mind but it would be a good "general pupose coil". I was going to spend today experimenting with coil shapes but I got side tracked by life. I want to look at flat square shapes, conical shapes, grant pancake shape ...... As Dr Sarver said I've got build up my empirical database, in others spend a day messing around 🙂
5:08 pm
March 26, 2010
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Mark;2104 wrote: Very hot/cool!
I was wondering, what should your shop conditions be like before installing one of these units? Being that these have extensive electronics, should the shop be fairly dust/smoke free?
The electrically conductive metal particles in grind dust do worry me .... a lot. I've started a thread about it both here and on IFettleIron. All suggestions/comments gratefully recieved
5:11 pm
March 26, 2010
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nuge;2106 wrote: I had mine in an unheated shop in a cold winter and everything was ok. I used antifreeze in the cooler.
Hi Nuge and welcome (even though I'm a few thousand miles from the NorthWest ;))
Thanks for the links. What cooler do you use with yours and what sort of duty cycle can you use it with. Boy oh Boy these machine suer are the dog's danglers
2:37 am
June 24, 2010
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David,
I'm glad the heat exchanger idea may work for you. (And glad I posted it, despite my uncertainty about its usefulness.)
9:45 am
March 26, 2010
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finally got to grips with Youtube.
The top figure on the display is the elapsed time. The lower is the current in the coil, this starts around 600A and then gets up to over 1000A.....thats a LOT of Amps....even more are flowing around as an eddy currents in the bar.
The bar is 40mm diameter.
Note how the heater heats the outer layer of the bar and this heat is transferred by conduction into the centre, rather like an eletrical gas torch.
Note also the sparks coming off at around 1.20. This machine ROCKS
1:45 pm
May 13, 2010
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I just have WAY too many questions about this magic tool. I am impressed with how fast that machine heats up the heavier bar. Do you know what the maximum diameter that can practically be heated is with the high frequency machine? ( I would assume that once you get too large you would burn the outside while the inside is still relatively cold). Can it be set to run at full power, stop for a few seconds while temperature equalizes and then kick back on to continue heating.
The largest bar I am currently regularly heating is 2 3/4" (70mm) or sometimes 3" (76mm), but a lot of my work is around 1" (25mm) and I am thinking of trying to produce a line of high end laminated steel woodworking chisels which would be much thinner. Any heavier than the 3" except in short pieces is starting to get too heavy to handle until I get a jib crane anyways.
In a little reading I have been doing online one of the supplier's website mentions that the coil voltage on a medium frequency machine is at a dangerous voltage and the coils need to be isolated from the user. The high frequency machines seem to be fairly safe as I have seen poeple hand holding steel and even touching the coils in youtube videos. Do you know anything about this? Setting up isolated coils would not be a problem for high production but seems to be getting complicated for runs of 100 or so parts.
3:43 pm
June 9, 2010
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david hyde;2110 wrote: Hi Nuge and welcome (even though I'm a few thousand miles from the NorthWest ;))
Thanks for the links. What cooler do you use with yours and what sort of duty cycle can you use it with. Boy oh Boy these machine suer are the dog's danglers
I use the one Grant recommended, the dynaflux. They are a US company and if you call with questions some old dude in the shop is happy to chat. Never had any duty cycle problems and I have abused it at times. I try to be cautious with long runs on hot days but that's about it.
3:55 pm
June 9, 2010
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Do you know what the maximum diameter that can practically be heated is with the high frequency machine?
I have the smaller, single phase 15kva (david's is 25kva)machine and i would say 1 1/4" round is the top end of practical heating. You can do bigger, but the machine doesn't really "like it". One trick i have used to do upsets on 1 1/2' bar is preheat in the forge (just to color) and use the inducter to isolate the juicy heat. On bigger stuff it doesn't like to start from cold, but once theres heat in there its good to go. Reheats are sooooo quick.
10:46 pm
March 26, 2010
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JNewman;2123 wrote: I just have WAY too many questions about this magic tool. I am impressed with how fast that machine heats up the heavier bar. Do you know what the maximum diameter that can practically be heated is with the high frequency machine? ( I would assume that once you get too large you would burn the outside while the inside is still relatively cold).
John I used all the coupling nuts that came with it making rectangular and long coils so didn't get chance to try making bigger coils. Yeah I did worry about burning the skin before the core got hot but you can alter the current that goes in.
It's one of those case's where a more powerful one can always do anything a less powerful one can (re rate of energy input) I'm kicking myself for not getting the next one up. I might even looking into selling this and "upgrading" in a year or so if it proves as useful as I think it will.
Grant's the man to speak to about suitable power/freq for what size of metal. As you saw on the video the 40mm skin does spark, but by this time the core is at well over yellow heat.
I don't know what the upper limit is (but I WILL find out) I suspect it will be good for a tleast 50mm round, maybe even square.
Re electric shocks, I've only ever had one minor tingle whilst holding the work. As far as I know it's a Very high current/ Low voltage device.
10:54 pm
March 26, 2010
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nuge;2127 wrote: I have the smaller, single phase 15kva (david's is 25kva)machine and i would say 1 1/4" round is the top end of practical heating. You can do bigger, but the machine doesn't really "like it". One trick i have used to do upsets on 1 1/2' bar is preheat in the forge (just to color) and use the inducter to isolate the juicy heat. On bigger stuff it doesn't like to start from cold, but once theres heat in there its good to go. Reheats are sooooo quick.
Preheat is a good idea.
I want to play around putting a thin sleeve of creamic paper between the work and coil. This won't affect the transfer of energy via electromagnetism but to my way of thinking this should
1. cut down on the heat that is radiatied from the work into the coils (and taken away by the cooling water), the work should heat up quicker and the water cooler has less cooling to do
2. You can use a coil that "hugs" the work more closely without worrying about shorting as you pull the work back and forth. This allows a better coupling of energy between the work piece and machine .... faster heating (as if it wasn't fast enough)
As mentioned my cooler needs "upping" hence this interest in cutting down on radiated heat.
I'm curious as to where all the heat that the cooler removes comes from, is it from heat radiated via the work as mentioned above or is it the heating effect of passing 100s of Amps throught the copper coils. If so, upping the tubing bore from 5mm to say 8mm will up the Xsectional area and cut down on the resistance and so heat generated by the current flow (but be a pig to bend), but will the increased diameter affect the electromagnetic field.
Grant ..... your experience needed here.
11:00 pm
March 26, 2010
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nuge;2127 wrote: I have the smaller, single phase 15kva (david's is 25kva)machine and i would say 1 1/4" round is the top end of practical heating. You can do bigger, but the machine doesn't really "like it". One trick i have used to do upsets on 1 1/2' bar is preheat in the forge (just to color) and use the inducter to isolate the juicy heat. On bigger stuff it doesn't like to start from cold, but once theres heat in there its good to go. Reheats are sooooo quick.
Nuge, I think your's puts around 600 Amps through the coils (and more as eddy currents in the work). Mine 1000Amps. Now schoolboy physics isn't generally applicable in the real world of engineering, but the fact that for a given resistance, the power disapated is proportional to the square of the current is kinda consistent with the heating ability observed with the different machines. Used to be maths/physics teacher many years ago ...... hated it.
11:08 pm
March 26, 2010
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david hyde;2058 wrote:
Amazingly quick on 1/2" round stainless, quite good on 12mm silicon bronze, little effect on 1/2 copper (too good a heat and electricity conductor ????).
They do say "read the manual" for a good reason, guess I should have done that. Manual says use 7 turns for Bronze/Copper with a 20mm coil.
I did just that, very slow to heat a 1/2" copper bar at 600Amps but "just about right" at 1000Amps. I say "just about right" because you don't want it to heat too fast because you want to catch the colour befor it melts. The great thing about copper is because its' such a good conductor of heat, the core is not far off the temperature of the skin (unlike steel)
The video below shows the 7 turn/ 20mm coil used with a piece of 16mm steel. I didn't video copper because it's not as spectacular to video as steel :smoke:
11:10 pm
March 26, 2010
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nuge;2127 wrote: . On bigger stuff it doesn't like to start from cold, but once theres heat in there its good to go. Reheats are sooooo quick.
I've noticed even when I've dialled in "full power" mine often starts off around 500-600 Amps which the grows to about 1050Amps as the work gets hot. Is this what you're referring to Nuge?
11:33 pm
June 9, 2010
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david hyde;2140 wrote: I've noticed even when I've dialled in "full power" mine often starts off around 500-600 Amps which the grows to about 1050Amps as the work gets hot. Is this what you're referring to Nuge?
It wont hit full power until the Curie temp. Not sure why. I find it really odd that you still feel magnetic properties in the workpiece at very high heats. Thought steel was non magnetic after 770 Celsius.
I was talking about working material sizes that are at the high end of the capabilities of my machine. Mine will reset when asked to heat something to large for the coil/machine. However, if you preheat that same material the inductor will take it the rest of the way.
1:55 am
May 13, 2010
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So 1 1/4" seems to be the limit for the smaller machine but David's seems to have no problem with the 1 1/2" (40mm) bar. Now I realize that 3" is 4 times the amount of steel as 1 1/2" but maybe a 50kva machine could handle it as long as the burning outside is not an issue.
Right now it is all just tire kicking though as I have a few higher priorities right now. A bender or bigger press, a forklift if my neighbor decides to retire and a little bit of a cushion in the bank. But the day will come when I get one, I hope I can get a 550v 3phase one, as that is the common industrial voltage around here, I do have 220v three phase as well but I am approaching the limit on that panel.
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