Induction heating coil offer

[BrevaParticipant @breva]

I spotted this little gadget and wondered if it would be useful for hardening and tempering small items.

**LINK**

Some interesting items on their site.

John

[BrevaParticipant @breva]

[JAParticipant @ja]

I have just had a quick look at this before going to the workshop. More than interesting.

Google "ZVS induction", there are quite a few web sites including some with circuitry. It looks as if the home electronics fraternity are interested.

JA

Edited By JA on 16/04/2016 14:22:23

[John RuddParticipant @johnrudd16576]

I read on another site that the item linked to in the first post suffers from reliability issues, has a tendency to blow its power switching devices….

How true this is, I couldnt say, but it would be remiss of me not to tell……..

[AjohnwParticipant @ajohnw51620]

The one mentioned in this thread is likely to be a better option.

**LINK**

A look around on the web should show what it and others can do.

John

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[JAParticipant @ja]

I am trying to work out how I missed the earlier thread. Mind you, it was only "open" for less than 2 days.

Has any one tried using an induction heater for model engineering work?

JA

[John FieldingParticipant @johnfielding34086]

Has any one tried using an induction heater for model engineering work?

A few years back I was offered the job of designing these things for SKF Bearings, but I declined the job. They are used extensively in the bearing industry to heat up the bearing to slip the bearing onto a shaft. IIRC correctly SKF wanted a 1 to 3kW version designing for the larger bearings, but I had other more interesting work in the pipeline. Today the small electric stove hotplates use the same principle for heating pans.

Be very careful with this sort of thing. A good friend of mine spent a long time designing these and ended up having all his stomach removed as long term exposure whilst bench testing boiled his internal organs!

[JohnFParticipant @johnf59703]

Breda, I have had an interest in this type of heating for some time and recently saw this unit on an American site. I have purchased one but not had time to play with it yet, I'll report back when I have

John

Edited By JohnF on 17/04/2016 15:14:16

[jaCK HobsonParticipant @jackhobson50760]

I got one and blew it up in minutes. I wasn't very careful.I was hoping it would be good for horology. I got another but have not tried it yet. I can at least vouch for reasonable delivery times

I notice you can buy induction heaters intended to loosen rusty nuts. Probably similar electronics inside.

I also got a much bigger one for £20 but I need to rig up a high current 40V supply… I was thinking of using my welder and rectifying the output but not sure what capacitors to use.

Edited By jaCK Hobson on 17/04/2016 15:17:19

[John RuddParticipant @johnrudd16576]

Posted by jaCK Hobson on 17/04/2016 15:16:40:

I got one and blew it up in minutes. I wasn't very careful. I got another but have not tried it yet.

I also got a much bigger one for £20 but I need to rig up a high current 40V supply… I was thinking of using my welder and rectifying the output but not sure what capacitors to use.

Edited By jaCK Hobson on 17/04/2016 15:17:19

You may find the output of your welding transformer too high…..you need to measure the ac voltage.

Then you will need some big diodes……capacitor wise, the working voltage will be based on the output of your welder…capacity wise, depends on how much ripple the induction unit can tolerate….if its small, then big capacitors….

Three 12v car batteries will power it….for a while…..

[Douglas JohnstonParticipant @douglasjohnston98463]

Posted by John Fielding on 17/04/2016 13:48:07:

Be very careful with this sort of thing. A good friend of mine spent a long time designing these and ended up having all his stomach removed as long term exposure whilst bench testing boiled his internal organs!

Where does the danger lie with the use of these devices? I can't see how internal organs can be damaged but perhaps someone knows better. I would like to keep my stomach intact.

Doug

[David JuppParticipant @davidjupp51506]

I have one of these **LINK** – have used it for freeing bolts etc., also for warming a hydraulic jack body after degreasing to make sure all water evaporated before re-assembly. I haven't yet tried it as a heat source for silver soldering, I think it might work for that.

It's a potentially handy piece of kit, but difficult to justify the cost for occasional use.

[JAParticipant @ja]

The only occasions I have seen induction heating used in industry – tube manufacture, melting exotic alloys in a vacuum and melting silver solder to fill sealing rings – the operations has either been effectively screened or the operators were quite some distance away.

I don't know the physiological effects of strong alternating magnetic fields but blood does contain iron.

JA

[MuzzerParticipant @muzzer]

The limits seem remarkably low. I've worked with automotive wireless chargers (up to 30kW or so) and stray fields are one of the restricting factors that the developers have had to contend with but they are not insurmountable.

Having spent most of my career in power electronics, I can safely(?) say that I've been exposed to much stronger fields on a very frequent basis. Seems that heating of the organs is considered to be the main risk (rather like microwaves) due to the fact that most of the fluids in our bodies are conductive hence prone to induced currents. However, I've never noticed any kind of discomfort.

The skin thickness at frequencies of 50-200kHz where most of my work was done is dependent on conductivity but that should be fairly high (ie conductive), so you'd think it wouldn't be more than a few cm, so in my case I'd expect my fingers (also much closer to the source of the stray fields) would be the first to tell me.

Murray

[jaCK HobsonParticipant @jackhobson50760]

I finally tried mine on 12v lead acid. Results were a bit dissapointing. It can get a 3mm screwdriver just red hot but I don't think it is really hot enough for an ideal heat treat. It gets stuck at that heat as, depending on the steel, it starts to lose mangentic properties and the heating becomes less efficient.

My bigger one should be better… if I can get a 40V DC supply…

[AjohnwParticipant @ajohnw51620]

There is a fair amount of info on people playing around with them on the web Jack. The screwdriver seems to be pretty typical or similar sized things. Some people play with connecting high current supplies in series to get more volts. One person I noticed used to server power supplies in series. These are usually 12v and lots of amps. As they are made by companies such as HP they are also well made. Usually there is a need to find out how they switch one after being plugged into the server. There is some information about that on the web because model aircraft people etc make high powered battery chargers out of them. It usually just means jumpering a couple of the connection in their socket.

Connecting them in series involved opening them up to isolate the chassis. The units can be surprisingly cheap on ebay.

I wonder if people are confusing microwaves with boiling stomachs etc. Induction heaters operate at much much lower frequency than microwave cookers. Those use one that causes water molecules to vibrate and generate heat – the frequency is not far off what one of the mobile phone bands use. As I understand it induction heating works by causing current to flow in the part. With enough power they can make things glow very red hot. Past cherry I would say.

John

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[JAParticipant @ja]

Induction heating is used for melting high temperature alloys, Nimonics etc, in a vacuum furnace. These alloys are non-magnetic.

JA

[SandgrounderParticipant @sandgrounder]

This is me on the right of the picture in around the early 1960's at Mullard Ltd casting a similar alloy to Nimonic with an induction furnace, I think it was around 10KW, not quite sure of the frequency but it wiped out the BBC Light programme when running.

John

Edited By Sandgrounder on 02/05/2016 19:33:24

[John RuddParticipant @johnrudd16576]

Posted by Sandgrounder on 02/05/2016 19:32:49:

This is me on the right of the picture in around the early 1960's at Mullard Ltd casting a similar alloy to Nimonic with an induction furnace, I think it was around 10KW, not quite sure of the frequency but it wiped out the BBC Light programme when running.

John

Edited By Sandgrounder on 02/05/2016 19:33:24

Nice picture….

Iirc, the Light programme became Radio Two, 1500m or 200kHz….

Edited By John Rudd on 02/05/2016 20:05:00

[AjohnwParticipant @ajohnw51620]

From memory and room for error it's circa 100 odd khz. Likely to increase as semiconductors do. It's likely to be a essentially a square wave drive which means that there will many higher harmonics.

I've seen parts going along a production line suddenly glow red hot as they pass through the field off the coil. Bulpitt who used to make Swan brand items. Their site was the pits but some of the technology they produced was amazing. Bought out by Moulinex eventually.

John

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