Andy's heat-treat furnace....

[Martyn]

Read the article here (http://www.britishblades.com/home/articles.php?action=show&showarticle=31).


Many thanks Andy (APG1961).

[DGentile]

While ago I built a similiar furnance.... nice job....

I have ONE important "improvement":
Add a contact on off switch to the door-system... so whenever the door get's opened the power will be off... that way you're on the safe side and it will not cost much more than a few pounds...

daniel

[ZDP-189]

Should an interlock cut power to the elements or the digital control?

[APG1961]

Should an interlock cut power to the elements or the digital control?

I agree with Daniel, the door should have an interlock switch fitted. I was just to eager to get heat treating and ALLWAYS pull the plug before opening the door.

I would put the interlock on the input to the digital control and then your certain power has been cut. If you switch the elements there will allways be an element (no pun intended!) of dought as to if the elements are live or dead.

Andy..

[rapidboy]

Anyone got any info on digital controllers ?
Had a look on the RS site but i don't know what i should be looking for.
Have made a start on an oven and was thinking about using some elements from a storage heater.

[PS_Bond]

Off the top of my head...

Supply voltage: Might as well be 240VAC
Inputs: I'd go for a K type thermocouple for the ranges involved; cheap, cheerful and more-or-less adequately accurate.
Outputs: personal preference, but I'd like a solid state relay that I can use to drive a bigger relay. Depends on what is available.
Range: Most of the controllers max out at 999C, which is OK for most things, but outside the ranges for the "interesting" stainless steels.
PID control (Proportional, Integral, Differential) is nice, especially if the thing can learn; ramp/soak can be nice to have.

I'm sure we've got at least one expert on industrial control on this board?

My suggestion would be to watch EBay & try to get hold of the datasheet for the unit on offer (and make *really* sure you have the exact part number!) & decide from that whether it fits your needs. I've got a couple of units now from doing that - both sub-1kC, unfortunately.

Not certain that your storage heater elements will tolerate the temperatures required...

[APG1961]

Anyone got any info on digital controllers ?
Had a look on the RS site but i don't know what i should be looking for.
Have made a start on an oven and was thinking about using some elements from a storage heater.

You should be looking for a PLC type control that is programed,logic, control.

These will cost a fortune from RS if you can find them.

Have a look on ebay and expect to pay between £30-£50.You need to look for one that reads to 4 digits if you want to HT over 1000 0C

You will also need a relay that can handle at least 15amp plus a K type thermocouple.

Get the book by Dave Gingery " Li'll Berth a compact electric resistance shop furnace. Published by Lindsay Publications. This is the best book on building an HT furnace available.

I would read the book before attempting to use the storage rad elements.

Hope this is of help

Andy..

[APG1961]

Everything Peter said!! He must have been typing his reply at the same time as me :D :D

[Art Lawrence]

Andy,
Now that you have had your funace for several years, is there anything you would do different or in addition to?

[knifemaniac]

APG1961, What speed you have with your oven? What time it takes to make 1050C?