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machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment.

Tag: metal casting

Brass Melt. Dangerous!

Today I received by mail 2 new crucibles for my furnace, so I tried a melt of brass.

The source of the brass was machining offcuts, machining failures (quite a few of them), and machining swarf.   The swarf was not very clean, probably containing some aluminium, cutting oil,  dirt and grunge.

It was an interesting experience.

Firstly, the temperature had to increase to 1000ºc.  Later increased to 1050ºc.  It is very hot.  And the impurities came off as smelly fumes, and dross.

But, I poured some ingots.

PANA3976

PANA3977

And I made another remelt.  And later remembered something which I had read somewhere…..   molten metal and water is dangerous.

After making a few brass ingots, and quenching the moulds so I could remove the ingots, I proceeded to another brass melt.

When I poured the molten brass  into the mould, IT EXPLODED!

IDIOT!!!!

FU**ING IDIOT!!!

I had caused a steam explosion.  Probably the mould was still damp.  And when the molten brass entered the mould, it EXPLODED.   I kid you not.  It went BANG.  Luckily, none hit me, but some of the molten brass had landed up to 2 meters away.

OK.  Lesson learned.  Molten metal must be treated carefully, with respect.  And NEVER put it in a container which is not thoroughly dry.

And after inspecting those brass ingots, I will never try to melt dirty brass, or any other dirty metals.

Meanwhile, preparing for another aluminium pour.

PANA3972

Here is the next tree.  You might note that there is a spaghetti appearance of wax tubes added to the tree, to allow efflux of air from the cavities, as the melt enter them.

Next aluminium pour on Thursday.  Fingers crossed.  Stay tuned.

Getting Ready for Casting

Setting up for casting molten metals into shapes for my model Armstrong cannon.  Still getting ready.

Today I made some moulds for dealing with any left over metal melt.  Not a big deal, but it does have to be done before the first melt.  No point realising that there is nowhere to put the left over aluminium or bronze during the pour.  It has to go somewhere.

So today I made some ingot moulds, in readiness.

PANA3872

The ends of the moulds are sloped to allow easy ejection of solidified aluminium or bronze.

PANA3875

4 ingot moulds.  Made from 40mm ID thick wall pipe, with long handles.  The diameter of my crucible is 48mm ID, so any ingots made should fit into my crucible later for remelting.

It seems a long time since I have done any welding, and the welding of these items was pretty ordinary.  But the joins seem water tight, so hopefully they will be OK.

Today I fired up the casting oven, to 850ºC, and the load was some ordinary food tins.  They are the correct diameter for investment moulds.  I wanted to see if the tins would cope with these temperatures. (after removing labels of course).

PANA3870

3 ordinary food tins, at 850ºC.

It became apparent, that the tin joins were welded not soldered.  And the inside and outsides of the tins were covered with some sort of paint or plastic, because it flaked off.  But the metal cans remained intact.  Admittedly, when hot they were VERY soft, but when cooled they retained their shape, and were quite stiff.   I would be prepared to try these for single use moulding projects.

I have realised that my investment plaster mixing bowl is too big for the vacuum chamber which I had bought.  So I have ordered another vacuum chamber, and waiting for it to arrive before starting a mix.  I am using the delay to gather items like the ingot moulds above.

It will probably be another couple of weeks before I am ready to cast.   Meanwhile my 2mm rivets have arrived at last, so I will get back to the riveting.

TURKISH BOMBARD – a-post-script. And metal casting setup ready.

I made this 1:10 scale model of the Turkish Bombard which currently resides in the Royal Armories Museum, Portsmouth, in 2016.  I specify “currently” because I originally saw this cannon in 1979 at The Tower of London.  And long before that it was used in Turkey, guarding the Dardanelles.  Quite likely used in anger in 1805 against a British fleet, approximately 340 years after it was made for Sultan Mehmet “the conquerer”. 

And I re-visited the original in May 2019. It seems like half a lifetime ago. Mainly I visited the UK to see the Trevithick dredger engine in the London Science Museum, but the Turkish bombard was the second reason. I could not find a photograph of the touch-hole in the bombard anywhere. And my requests to the museum went unanswered.

The original bombard in the Royal Armories Museum, Portsmouth, UK.

So, here is my photograph of the touch hole, in case anyone else is inclined to make a model. I guarantee that this is the only photo of the touch hole which you will find, with my hand anyway.

The Turkish bombard touch hole
My 1:10 scale model of the bombard. I still have not added the touch hole.
The Arabic script around the muzzle. Not as good as in the original. But as good as I could manage in 2016.
and the large thread between the barrel segments


So, I made this model, in wood, as a practice run, intending to make a bronze model eventually.

The reason for this post script is that I had a question from a reader about a remark which I had made in 2016. And I could not find my original photographs. So I took some more, as you have seen.

And……… very excited to announce that I now have a foundry setup, and could possibly make a bronze example of the bombard. But first I intend to obtain some casting skills, by making parts for my 1:10 Armstrong cannon.

I replaced the analogue controller with a digital type in the potter’s oven which I had recently purchased, and today my wiring was checked by an expert before we ran a test run. (thanks Stuart!) All good, up to 750ºC, which is enough for preparing the investment molds.

Here is a shot of the oven, and the metal melting furnace.

PANA3860

from the right, the melting furnace which should be adequate for 3kg of brass/bronze,  and the investment oven. The oven might also be useful for metal tempering. Note the Hebel bricks behind the oven.

Hopefully, the first attempt at a casting session in a couple of days.

 

Repairing Failed 3D Prints

As a beginner, I have a fair percentage of unsatisfactory prints.

Print breaks free of plate.

Supports fall over.

Overhanging areas insufficiently supported.

Holes appearing due to wrong settings.

etc. etc. etc.

Most of the time I just bin the failure, change the settings or setup, and make another print. And wait another 2, 9, 12 or 24 hours……  Not a huge financial cost, but does involve waiting.  And I am not very good at that.

I used to grow olives and make olive oil.

Sometimes the bottles of oil were sealed with wax.  Melting point 85ºc.

After a failed print of 6 items today, due to inadequate supports of overhanging areas, I wondered if the holes and thin areas could be fixed with the bottle sealing wax.  After all, lost PLA casting is just a descendant of the lost wax method in the metal casting process.

So I found the left over remnants of the bottle sealing wax, and heated up a soldering iron.

IMG_8520

One of the failed prints.  This is a wheel trolley bracket for the model Armstrong cannon.  The moth eaten area was overhanging, and the support had fallen over.  The area was thinned and the holes were not properly formed.   If a brass or bronze casting was made from this, it would have been unusable.

IMG_8522

The 850g slab of bottle sealing wax, and soldering iron.  I do not know if this supplier is still available.  It was not expensive.

The soldering iron is heated, dipped into the wax, and the molten wax carefully dripped onto the deficient area of the print, gradually building it up.

The wax can then be shaped with the soldering iron, or a heated knife, or even a finger or thumb.  I also tried a blade shaver and sharp knife.  I think that my soldering iron, and finger were the best tools.

 

IMG_8521

The repaired area.  It looks unsightly, but of course the wax will all disappear during the casting process, along with the PLA.

I am probably reinventing the wheel with this idea.  Again.  But have not seen it used anywhere else.  So there it is.  I think that it will be useful to me.

PS>. 12 hours later.  I now realise that this is so old hat that I am embarrassed that I posted this.  Reinventing the wheel,… that’s me.

 

 

Bronze Casting. 1.

My model Armstrong cannon has some components which will be difficult to machine, and would involve silver soldering many tiny pieces.

For example, the steel brackets in which the wheels are supported, and the centre column.

rear trolley

There are 4 trolleys like this.  Each one has 2 or 3  wheels.  It is a Z shaped profile with 3 gussets visible and 2 more inside.

IMG_8411

The centre column.  It could be fabricated.  

But being basically lazy and always looking for the easy way out, I have decided to investigate the possibility of casting these parts.  And some others.

So I have printed them in PLA filament, with a view to a “lost wax” type of casting process.  It will be “lost PLA” of course.  Maybe doing the casting myself.  But also checking the possibility of having it done professionally.

The PLA printed parts which will be melted and burned away in the casting process, have to be as well finished as possible.  So I have been experimenting with various settings in 3D printing.  One problem is that the molten plastic thread has to be supported.  Overhangs up to 45º or even 60º can self support.  And even horizontal overhangs can self support if the gap is not too big.

print unsupported threads

But this gap, about 20mm, proved to be too big…

print unsup oblique

The threads are partly bridging the gap…

print unsup end

Horrible.  It is the underside, but even out of sight, it is unusable.

So, I am printing up some supported versions, even as I type this.  And I am going to look at some casting equipment which I might be able to borrow.  Apparently the gas furnace is very noisy, and it needs a home with no close neighbours.   List…. a furnace capable of melting bronze, a crucible, investment casting powder,  protective gloves, helmet or face mask, leather apron, tongs, slag ladle, a casting box.   There are many YouTube videos on the subject of lost PLA casting.    Watch this space.  But if the quote for professional casting from my printed molds is not too fierce, I will probably take that path.

HOW TO MAKE A FULL SIZE STEAM ENGINE

Click on the link to watch a movie-documentary from the 1930’s.
If you are a steam head, you will love it.

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