Metal Melter

[daedalusminos]

The element needs to be retained better!

Can you not pin the element into the groove - needs to be done on an unfired Kanthal element as they go very brittle once fired a few times.

 

[Kram]

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.

Plaster has a few issues. Hard to get all the water out without it going crumbly. Aluminium is ok bit brass is on the hot side. My first attempts (years ago) were baked for ages and still had a mini steam explosion. If you use plaster I would give it a thin coat, possibly using sodoum sillicate instead of water, but make up the bulk of the mould with casting sand. I havent tried it, might not work.

VOG has a load of YT videos worth watching, he is focused on getting maximum detail out of castings, very relevant for trying a picture.

are the flints all set in the wall?

Flints?

Can you not pin the element into the groove - needs to be done on an unfired Kanthal element as they go very brittle once fired a few times.

They do and I knew that, yet still stretched it a bit after a few fires to get a better fit.
The failure what where Id drilled the clay and added some steel 2.4mm filler wire hooks to retain the element, glued in with an excess of alumina/SS. The alimina caused a hot spot where it failed.

 

[daedalusminos]

Use a piece of Kanthal wire to retain. Any reason you're not constructing from refractory bricks?

 

[Onoff]

are the flints all set in the wall?

Some were...for a short while...

 

[Onoff]

and still had a mini steam explosion

...won't be me pouring the molten metal in...

 

[JMS1972]

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.

You should use investment plaster

Lost PLA casting works pretty much the same as lost wax.

 

[Onoff]

You should use investment plaster

Lost PLA casting works pretty much the same as lost wax.

Touch! I can get 5kg of investment powder locally for a tenner.

 

[JMS1972]

There's lucky

 

[Onoff]

There's lucky

I see it as an investment.

Seriously, never knew the stuff existed. Off to Google the lost PLA method now.

 

[JMS1972]

I see it as an investment.

Seriously, never knew the stuff existed. Off to Google the lost PLA method now.

As someone said above. The Veg Oil Guy is the UK expert on YouTube..

https://youtube.com/c/VegOilGuy

He has a playlist on lost PLA. You'll see why my next welding project is making a burn out oven

 

[Kram]

Ive read that you need an oxygenated /open oven, to convert carbon soot into CO², such that it can burn out. He has a comparison and PLA is poor bit other videos he had good results. Id think better to print a negative mould and make a lost wax positive. Moat of the wax can be collected and reused.

Are there no FDM printers that can extrude hot wax?

Got the element out, the new one prepared, gave pot a coat of SS and now looking like this ready to install. This time Im going to use element wire offcuts to retain it.

 

[Onoff]

As someone said above. The Veg Oil Guy is the UK expert on YouTube..

https://youtube.com/c/VegOilGuy

He has a playlist on lost PLA. You'll see why my next welding project is making a burn out oven

Just been watching some of his stuff thanks.

 

[JMS1972]

Ive read that you need an oxygenated /open oven, to convert carbon soot into CO², such that it can burn out. He has a comparison and PLA is poor bit other videos he had good results. Id think better to print a negative mould and make a lost wax positive. Moat of the wax can be collected and reused.

Are there no FDM printers that can extrude hot wax?

Got the element out, the new one prepared, gave pot a coat of SS and now looking like this ready to install. This time Im going to use element wire offcuts to retain it.

View attachment 332262

You just need a hole in the top and bottom of the oven to let fumes out or your elements get destroyed.

There are lots of specialist (expensive) resins specifically designed for lost resin casting obviously you need a SLA printer for them.

That's the direction VOG has gone as he like ultra detailed miniatures and jewellery.

Depends what you want to cast ...

 

[Kram]

Most of mine will be lathe food. Olfoundryman has good videos for bigger stuff. Explains a lot about aluminium, proper way to do sand casting and quality issues.

https://youtube.com/channel/UC90RoN_IjSRF18jAG0HIA6g

 

[Kram]

That was my idea post #1!

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

Here is a sketch of the paper variety, if thats ok? It will not be removable so, needs to be the minimum fill just to resist crushing while forming the clay, and will be burnt out as part of the drying.

I have enough clay for a couple if you wanted one made up. The element for this needs to be stretched to 220mm which is about right for most on ebay/amazon. *They need to be annealed before stretching*, light stretch then run off an SCR to get it red/orange hot for 30 seconds.

 

[Onoff]

Here is a sketch of the paper variety, if thats ok? It will not be removable so, needs to be the minimum fill just to resist crushing while forming the clay, and will be burnt out as part of the drying.

View attachment 332863

I have enough clay for a couple if you wanted one made up. The element for this needs to be stretched to 220mm which is about right for most on ebay/amazon. *They need to be annealed before stretching*, light stretch then run off an SCR to get it red/orange hot for 30 seconds.

Right, so that's a spiral yes?

I'll get No.1 son on it right now.

Probably want some pokey out sprues at each end for the element connection points?

 

[Kram]

As it was a dryest day of the week here I got stuff done outside!

Lid insulation filled in and by the heater to dry. First couple inches are mostly perlite, tiny bit of the clay mix. Then about half inch of the 20-30% clay mix, followed by 5mm mix of clay, tiny bit of perlite and 700g alumina. Lastly smoothed off with alumina/sodium silicate paste.
When dry this should have very good durability and excellent insulation, I hope!

Same treatment to the cylinder but it was a pain without a form to block the opening.. lots fell in and will need picking out of the element..

Tomorrow plan to warm it up very slow, then melt some brass.

 

[AKN]

Probably a very silly suggestion but would fire clay or exhaust repair paste work for holding the element?

 

[Onoff]

On the back of my wanting to melt metal and @Kram 's electric furnace experiments we've been corresponding for a couple of weeks. I offered to look at making a 3D printed mould/form for the fire clay. So @Kram came up with the fag packet sketch which I gave to my lad and said have at it! He drew various incarnations in Fusion and it went back and forth between @Kram and us. A number of test prints were done.

Much debating as to the best way to print it and how to avoid supports.

As one piece with lots of supports to break out:

At 45 degrees:

Tree supports:

Decided eventually to print the form in two halves like a couple of Anderson shelters!

This, the first completed half in white PLA after an 11+ hour print. Really quite pleased with it. 5% infill, 0.3mm layers. About 200g of white, ZIRO, Pro PLA. First pics are blurry as a moving target!

The spiral form that the heating element will follow:

Next the other half then it's off to @Kram. Both halves will need gluing / bolting together.

Seems a pity to have to burn it out so we're talking about covering it in mould release etc, packing the clay around, then winding it out like a bfo screw for reuse.

Good fun doing this!

 

[Onoff]

Some more gratuitous backdrop shots:

The main "cylinder" is a bit "ribby", like vertical lines rather than super smooth. It's not rough per se.