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Metal Stuff / Re: 100Kw CFEI Induction Furness
« Last post by vintageandclassicrepairs on Today at 08:31:22 AM »
Hi Andrew and All,
Not directly related to this thread but it reminded me of when I worked on Alstom Generator rotors
Induction heating is used to expand  the rotor end bells for removal and refitting
Water cooled cables are wrapped around the end bell and fed from 2 phases of the station standby diesel generator, I cannot remember the power needed but the diesel engine was a V12 with a massive turbo on each bank of cylinders, It was such a smooth running engine a 50p coin sat on edge on the engine block stayed there, the noise was something else though !!!


Metal Stuff / Re: 100Kw CFEI Induction Furness
« Last post by eskoilola on Today at 06:19:22 AM »
I am rather surprised that I quessed correctly the setup of the heater coil in relation to the crucible. There is a reason why it sits on top of it instead of being casted as a part of the crucible. Thremal expansion of copper is quite a lot larger than that of the crucible material. Built this way the crucible will not crack as the coil can expand when it warms up.

Thanks for these pictures !
Metal Stuff / Re: 100Kw CFEI Induction Furness
« Last post by awemawson on Today at 05:56:34 AM »
It is very tempting Matthew but there are things ahead of it on the 'round-tuit' list
Gallery / Re: Annoying sprung handles on machines
« Last post by mattinker on Today at 05:47:19 AM »
I did something similar on my mill for Z axis. Just don't forget to unlock! Imagine how I know!

Regards, Matthew
Metal Stuff / Re: 100Kw CFEI Induction Furness
« Last post by mattinker on Today at 05:45:18 AM »
Great stuff Andrew, this was the project where I got to "know" you, please resurrect!!

All the best, Matthew
Metal Stuff / Re: 100Kw CFEI Induction Furness
« Last post by awemawson on Today at 05:36:35 AM »
In fact I have two 'furnace bodies' - one is arranged to tilt to pour in a conventional manner, where as the other inverts - the mould being clamped to the top so the metal is never exposed to the atmosphere.

The pouring one I totally rebuilt and upgraded the tilting mechanism using 'air over hydraulic' control

It would be fun to get it all fixed up again sometime . . . . .
Gallery / Re: Annoying sprung handles on machines
« Last post by jb3cx on Today at 05:29:35 AM »
Hi Joules,
            Years ago I had a KRV 3000.the handles used to fold flat against the hand wheel .the guy I bought the machine off had them fitted as he got caught up a couple of times ,seemed to solve the problem for him,
Metal Stuff / 100Kw CFEI Induction Furness
« Last post by awemawson on Today at 05:28:59 AM »
eskoilola's thread on building his induction furnace awakened my interest in this subject, and to my amazement I found that I still have pictures of my setup from 2006 when I was working on mine before we moved here 11 years ago.

Rather than hijack his thread I thought I'd post the pictures here.

. . . . maybe when / if I've finished the Beaver TC 20 CNC lathe this might be the next resurrection thread  :ddb:

The big blue box takes in 3 phase 415v AC power, and rectifies it and resonates a tank circuit, the coil of which is wrapped around the crucible, and the capacitor bank is in the box. The resonant frequency is determined by a microprocessor that pings the tank - measures the frequency then excites it at this frequency - the required frequency varies with the charge of metal in the pot

The 'furnace body' is remote from the driver and connected via 70 mm CSA cables that are threaded inside rubber 'brewers hose' that have water pumped down to prevent the cables melting (huge circulating currents involved). There is a separate chiller unit that keeps the water cool.
Project Logs / Re: Induction heater project
« Last post by awemawson on Today at 04:05:55 AM »
The coil needs to be closely associated with it's resonating capacitor bank - the circulating currents are enormous. Mine adjusts resonance frequency dependant on the charge in the crucible, but is nominally 3kHz

The tank capacitors need very careful specifying if they are to survive

Rather than hijack this interesting thread I have started another with some pictures of my 100kW furnace here :,12596.0.html
Project Logs / Re: Induction heater project
« Last post by eskoilola on Today at 03:35:08 AM »
Here is my interpretation of an induction heater.

This device needs two separate power supplies. First, the high power supply delivering juice to the heater coil through the driver. The other power supply is for all other functionality like control logic, water pump and fans. The high power supply can be switched on/off by the control logic whereas the auxiliary power supply has a real user operated switch.

The high power supply needs a soft start circuit which consists of two relays and a resistor. This is because the transformer I have is a toroid transformer and that devil will blow the fuse every other time if cold connected to mains. The high power supply will be switched on only when needed.

The rectifier and smoothing is just a couple of full bridge rectifiers connected in parallel using resistors (0.1 ohm). I have a box full of 10 amp rectifiers and if I connect 10 of these in parallel that should be more than enough for this application. The smoothing consistsa of 2 capacitors size of a Chevrolet piston each worth of 100.000uF.

Voltage sensor in just a resistor divider. The current sensor I probably make out of a hall sensor glued on top of a wire. If the sensitivity is not enough just cut a gap in a ferrite toroid and stuck the hall sensor in there. The wire then goes through the toroid hole. These sensors are used to cut off the driver in case the voltage is too low or the current is too high.

The FET array switch is a bunch of FETs connected in parallel. I have another box full of 30A/150V fets. Having 10 of these in paralle should do it. With FETs there must be quite a lot of margin as the FET resistance grows when it heats up which again raises the temperature ....

The fans and the pump will be ran only when needed. The temperature sensor is used to switch the heater off if the temperature raises too high. The flow sensor is used to see that the coolant is really moving. The level sensor is used to check that there is enough coolant in the system. These should cover all probable scenarios of overheat, coolant blockage and other situations when cooling is not functioning properly.

The control logic will most likely be a MCU board having an Atmel AtMega64 on it. The user interface is power switch, current (average) and temperature meters, power adjustment, ontime adjustment, heat on/off buttons and indicator lights. Should do it. Will show the desighn of that one later.
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