One good ant invasion and you will be cured of using sugar in the shop.
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Using a microwave oven to harden a sodium silicate core.
- Thread starter 100model
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100model
Well-Known Member
In theory any glue or adhesive could be used but in the real world a lot can not be used for many reasons. To give you an example Liquid nitrogen could be used to freeze sand with a tiny amount of water to make a core. Pros are quick to make and no need to dig out hard cores because the ice has defrosted so the sand just pours out. The cons are liquid nitrogen is hard to get and precise timing is needed to put the core into the mold before it defrosts. I am sure many others could add to the reasons why they would not use liquid nitrogen.
You would also have the frozen water still in the core which will then boil out and cause problems.
lee webster
Well-Known Member
I would like to know more about the construction and materials used for your core moulds hardened in the microwave. Have you made a video?
100model
Well-Known Member
Green sand contains water and does not cause problems if the water levels are kept below to what sand can pass steam through the sand pores.
100model
Well-Known Member
I do have a video about how I made a plaster two piece core mold in that video. The other core mold was made from pvc conduit pipe with a slot cut down the side so the core can be removed.
Is the moisture not far more of a problem in a core as to escape it will try to pass through iron before the outer sand? Particularly if the core is not properly vented. The "scabs" on this casting go deep and were the result of a poorly vented core
Is the moisture not far more of a problem in a core as to escape it will try to pass through iron before the outer sand? Particularly if the core is not properly vented. The "scabs" on this casting go deep and were the result of a poorly vented core
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I tend to think of cores as the round bound sand cylinders that go in places like the bore for engines, and the space around a round object like your photo I would consider a mold, which could be made of core material.
But your photos still I think demonstrate a valid problem that can occcur on castings surfaces, both interior in bores and external on cylinders.
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100model
Well-Known Member
I NEVER vent my cores for cast iron and never had a problem with cores causing scabs. I did have a problem with a core wash that I used (lots of blowholes). I used that core wash on thin castings which solidify quickly and no problems with blowholes but this casting was 25mm in thickness and cooled very slowly giving time for the blowholes to form under the skin. It was a alcohol based wash from foseco and I did ignite the alcohol. I went back to using no core wash and the blowholes disappeared. Another iron caster near where I live used the same product and had the same problem with his cores.
Well all I can say is that three of those parts were cast and all had a similar fault. recasting with a vent hole down the middle of the 32mm dia core cured the problem on the replacements. It is a long 350mm - 14" cylinder so going to be harder for gasses to make their way out the end of a solid core than your typical length model cylnder jacket or liner.
It was done at a commercial foundry, first batch the young lad was left to do it, second time around a more experienced foundry man took care of things.
It was done at a commercial foundry, first batch the young lad was left to do it, second time around a more experienced foundry man took care of things.
100model
Well-Known Member
Using too fine a sand lowers the porosity on cores so that is why I use a coarse sand for cores and no venting is needed. Have a look at my video about using portland cement to bind core sand. Water is needed to make portland cement harden but any excess can be dried off. No vents and no blowholes after machining.
Thanks, I see you did have to dry the cores to get the moisture right down.
Also the casting I showed had a much longer core compared to that short one so anything that wants to escape will have a harder long route out if not vented. You can see here from the core prints that the diameter is about the same as yours but about 6 times longer. That cylinder is just under 8kg of iron.
This is one of the differences between home casting and using a foundry. If you have to pay for the time to make a special mix, dry it off, etc then your casting will cost more than one where the foundry can use a stock core
Also the casting I showed had a much longer core compared to that short one so anything that wants to escape will have a harder long route out if not vented. You can see here from the core prints that the diameter is about the same as yours but about 6 times longer. That cylinder is just under 8kg of iron.
This is one of the differences between home casting and using a foundry. If you have to pay for the time to make a special mix, dry it off, etc then your casting will cost more than one where the foundry can use a stock core
100model
Well-Known Member
I have often wondered when pouring much larger castings than in a hobby shop methods may have to change.
It costs nothing to vent, does not cause problems, and takes very little time.
My opinion is "When in doubt, vent everything".
Why take chances with what venting may or may be needed, depending on the type of sand that you use?
Cores are traditionally vented through the center, and then both ends of the core vented up and out the cope.
Better safe than have a ruined casting.
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My opinion is "When in doubt, vent everything".
Why take chances with what venting may or may be needed, depending on the type of sand that you use?
Cores are traditionally vented through the center, and then both ends of the core vented up and out the cope.
Better safe than have a ruined casting.
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Quickly become infested with fire ants here in Florida for sure !
Yes, fire ants have become very prevalent here, and are somewhat of a plague really, since there does not seem to be anything that limits them.
I had to bend over and look inside of an open manhole last year, and I felt something crawling on my hand.
I had not noticed that I put my hand down on a low fire ant hill, and so my hand and wrist were covered in fire ants.
I got bitten several times on the hand, and then on my ankles too, from them crawling up my shoes/socks.
Luckily I am not alergic to fire ants (yet), and so just a minor annoyance.
I know some folks who swell up like a ballon and have to rush to the hospital when stung by fire ants or bees.
Insects can be a huge problem in the south, with the warm weather, especially after a mild winter.
And mild winters here are pretty much the norm here.
My nextdoor neighbor got a natural gas house generator, and within a week, the ants had nested on top of the controller.
Had she not opened the unit it check it, the entire enclosure would have been full of ant nestings.
Sort of like feral hogs in Texas.
You can hold their number constant if you hunt them continuously, but you can never eradicate them, and you can't really reduce their numbers.
And you have to use great caution if you eat wild hogs, since they carry all sorts of diseases, that can be transmitted during handling and cleaning.
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So I take it that you gentlemen have no qualms about watching videos of the guys doing aluminum castings of fire ant nests? That is, other than the fact they're pouring molten metal into a hole in the ground?
I am not keen on intefering with the natural order of things, but that being said, there are things that must be controlled, such as invasive species.
Either you control invasive species, or they take over and cancel all the local wildlife.
And ferral hogs are totally out of control in Texas and surrounding states.
The ant nest castings are interesting in that it seems they are all different, even though they are all ants.
Different shapes, sizes, arrangements.
Seems a bit like the tunnels inside of the Eygptian pyramids; sort of meandering all over.
I think you really need to to a lot of digging and use a pressure washer to retrieve those ant castings.
And those castings seem to sell for a fortune.
Too much work for me, but I do admire them.
Not much different than Pompeii, or near Mt.St. Helen when it went off; stuff like that happens sometimes to many creatures.
Note to ants: If you see some bugeyed nerdy looking person coming towards you with a crucible full of hot metal, don't hang around to find out if that creature is friendly; run like heck.
I guess that is where they got that army expression "Bug-out".
I went to a rental house to paint the interior for my boss, and the walls were covered in sheets of cockroaches.
The roaches moved in waves as you walked through the room.
Creepiest thing I have ever seen, and there are not many things that creep me out.
Took 4 treatments to finally clear them all out.
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