Metal Melter

[Onoff]

Looking at @Kram 's fire clay/element build...

Thinking to:

3D print the inner of a mould with a spiral on the outside. Should allow the element to sit perfectly, In segments for easy removal.

Then place in a large container and fill the gap with this stuff:

Vitcas Refractory Castable Grade 1600°C-Refractory Concrete

Castable Refractory (Refractory Concrete) is used for repairs to boiler linings, boiler doors and incinerator linings. For use where localised temperatures are higher; for example in gas or oil burner blocks and where forced air is being used.

shop.vitcas.com

 

[h-dom]

That stuff is good but you can buy big bags of it on eBay etc much cheaper.

25KG 1400DC Dense Castable Refractory Furnace Kiln Forge Lining Pizza Oven | eBay

This is a very good quality castable which contains 40% alumina and is rated to 1400°C. 25KG 1400DC. Can be used for all sorts of kilns, forges, furnaces and pizza ovens! This should be cast at least 50mm thick and is 2000KG/m³.

www.ebay.co.uk

I say cheaper, but you get more for your money is what I mean. And you have to mix it.

 

[Pete.]

Looking at @Kram 's fire clay/element build...

Thinking to:

3D print the inner of a mould with a spiral on the outside. Should allow the element to sit perfectly, In segments for easy removal.

Then place in a large container and fill the gap with this stuff:

Vitcas Refractory Castable Grade 1600°C-Refractory Concrete

Castable Refractory (Refractory Concrete) is used for repairs to boiler linings, boiler doors and incinerator linings. For use where localised temperatures are higher; for example in gas or oil burner blocks and where forced air is being used.

shop.vitcas.com

If you're gonna do that you could also print some coil supports to stop the element drooping out of the spiral when it gets hot.

 

[Onoff]

@Kram , where did you get your element from?

Cheers

 

[Onoff]

Something like this in guessing?

3000W Heating Element Coil Heater Wire Line 3KW Kanthal A1 Furnace Resistance | eBay

Find many great new & used options and get the best deals for 3000W Heating Element Coil Heater Wire Line 3KW Kanthal A1 Furnace Resistance at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

 

[Kram]

If you wait a week I should have some learnings I can share.

The listing is gone but look for one that is kanthal instead of nichrome.

This is the clay Im using, sold out but lots of sellers have it.

25kg Bag of Fire Clay to Make Refractory Furnace Kiln for sale online | eBay

Find many great new & used options and get the best deals for 25kg Bag of Fire Clay to Make Refractory Furnace Kiln at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

The link above to the refractory castable stuff is probably better but I believe that uses a setting cement binder, where as clay is only set by heat.

However, clay/castable is only good for the elemement holder. It is dense and transmits far too much heat as insulation. 15mm wall is about the maximum around my element. Its a lot of mass to be heated before the heat goes into the cruicible.
Insulation use perlite and sodium sillicate

Sodium Silicate 20 Litres (Water Glass) Concrete Sealer, Adhesive, Automotive Gasket sealant : Amazon.co.uk: DIY & Tools

Sodium Silicate 20 Litres (Water Glass) Concrete Sealer, Adhesive, Automotive Gasket sealant : Amazon.co.uk: DIY & Tools

www.amazon.co.uk

https://www.amazon.co.uk/gp/product/B097F1B2QY/

Ideally you'd mix in plenty of alumina blasting grit, and also make up a alumina/sodium sillicate mix as a hot facing instead of the clay. However I have not found alumina cheap without buying massive bags, and I already had the clay.

Clay and castable are likely to have cracking as it dries unless you knkw what your doing with pottery - I dont. It shouldnt matter too much if it does. Perlite/SS is much more fragile but it will dry fine without cracks.
Perlite you must use a respirator mask.


I may be interested in slme 3d printed spirals.

 

[h-dom]

I don't know if it helps but I have loads of ceramic fibre insulation wool, 1" thick. Let me know if you want to use that too. My forge I am building (I know it's different) is 3mm steel shell, 2x1" layers of ceramic fibre and then 1" castable refractory.

 

[Kram]

I had another go at this tonight. Drilled my thermocouple hole, worked out how to do the tails, tapped cylinder for the terminal blocks. I think its ready to mix the insulation. The tails are 4mm OD copper tube with a 1.5mm dia copper wire and the element tail inside. The copper will be crimped on and remove the resistance and any heat from the tails. Thermocouple needs to be shortened.

Insulation, Id already mixed up some fireclay and perlite but it is clumping up from mixing wet - should have done dry! I know the bulk of it will not get hot enough to vitrify the clay so I might abandon the idea, and use perlite and sodium sillicate alone or just a small amount added.
Ratio is 140ml per litre of perlite.
First need to test the ratio with a 1.3L cake tin to make a round brick.

 

[Kram]

Insulation is in. I added a little clay to the mix. Its taken roughly 27L of perlite and 3 8L of sodium sillicate to fill up. I may put a layer of clay to protect the top.

A bit of reading suggests theres 3 ways to set sodium sillicate. Microwave, heat/dehydration, and CO². CO² is much weaker than the others, microwave quickest and strongest, but wont work with a huge metal cylinder. It seems the best option is just to run it!

I drilled the thermocouple hole far too low but wasnt sure how much. Half hour with die grinder and Im getting close. Not happy with that at all !

Im likely to modify it or do a version 2, so ordered another element. This measures ~15.6R which is around 4kw as it is. I think next version Id have a small coil on the bottom in series which would bring it down to 13-15A.

Heating Element Coils Wire AC220V 3000W Kiln Furnace Heating Coils Element High Resistance Dryer Restring Wire Heater Coil Wire : Amazon.co.uk: DIY & Tools

Heating Element Coils Wire AC220V 3000W Kiln Furnace Heating Coils Element High Resistance Dryer Restring Wire Heater Coil Wire : Amazon.co.uk: DIY & Tools

www.amazon.co.uk

Just remebered Id forgotten to add a couple more crimps onto the tails

 

[Kram]

I left it heating for a couple hours at 134w, running off 49v. Its getting to 200c inside, outside cold. When I tried on mains it instantly tripped the house RCD, too much water in the perlite that I need to boil off.
Found the centre of element and thats giving me 530w, its upto 500c and climbing. The outside 14c.

 

[Kram]

I put the melter away still hot after baking. Today theres about 100ml of thick clear alkaline goo collected under the bottom drain hole which I assume excess sodium sillicate.
The clay pot has lightened to an orange, and it seems dry for a proper test!

Getting around 3300w at 13.28A

 

[Kram]

Im testing using a SCR dimmer unit, so the wiring is a mess. Heating up slowley with a new cruicible. I had it set 700- 1500w for most of the run. I did try full power but not for long.

It appears the thermocouple is reading 200-300c low, it may be connected wrong or just the position. This was showing around 450c, and theres a small puddle of liquid alu in the bottom.

I havent yet finished the tongs so a proper melt may be tomorrow or in the week..

The SCR is good, just about fits.

I want to add a power meter in the lid, I think theres just about space.

It holds the heat very well and was still 400-500c an hour later, when I saw it starting to rain and had to pack away quick.

 

[Misterg]

Looking good - You are going to fit an interlock to the lid when it's finished, aren't you? (Just in case anyone forgets to turn it off before sliding the lifting tongs in...)

 

[Kram]

No need for an interlock as I have a nice big illuminated switch on the side, however I do need to sort out a proper lid.

First pour was detailed here, if anyone interested has missed it, www.mig-welding.co.uk/forum/threads/stuff-you-have-made-today.67127/page-1035#post-2007078

Today I wanted to try brass. The plan was just to use a tiny amount - four wood screws and a few 13a plug pins.

I had a few issues with the RCD tripping so stopped for today and need to investigate the element and control box. It did melt, as I could see the shiny surface when I poked it, it did look fully molten however the result shows it was not, and cooled down a lot before I tipped it out.

 

[daleyd]

 

[Kram]

Tonights attempt, gentle heat to 200c for half hour while messing on lathe, then 2.2kw, under half hour had it around 900c. Its not slow! I had prepared some brass bits to melt, two old bathroom taps.

I heard that 50hz buzz of mains electrickery escaping and the element was off

Not a big suprise as it had badly oxidised and had been bent around a lot while testing. Too hot to examine and now its bloody raining so had to pack away.
It'd been off a minute or so for the photo.

Tomorrow will examine, possibly fit a spare element, possibly remove the clay pot and work out a new design. The element needs to be retained better!

Anyone interested in 3d printng a shaped spiral?

 

[Onoff]

Anyone interested in 3d printng a shaped spiral?

That was my idea post #1!

Give me a sketch and we'll get straight on it here.

 

[Kram]

I'll have a think how to do it. Ive got an idea that, instead of making a solid pot, likely to crack - it has cracked all over, which was expected... to make small profile sections that can be glued in, maybe 2 inch long.
Then it will be a 3d printed mould and clay or alumina bricks rather than spiral form.
These small peices would be easy to do a controlled fire in the current version.

 

[Onoff]

Right then, someone recommend me a plaster of Paris type...plaster of Paris that I can pour over my 3D print here to make a mould for brass casting.

 

[123hotchef]

are the flints all set in the wall?