lost wax casting in sand ?

[kadora]

Hello friends
is possible to use sand instead of investment for lost wax casting?
Investment needs to be burned in high temperatures
what is for me impossible so i am looking for
a simpler solution.
thank you

 

[cgabel]

The reason for using cristobolite based investment is that it is rigid as well as porous. Burnout leaves the cavity void. However a high temp burnout of 1000 degrees F is needed to completely clear the mould of wax. If you just melt it out at low temperature the porosity is "clogged", and the molten metal will react with the wax causing gasing and imperfections in the casting. Bonded sand, such as used for the making of cores, might work, but you would still have to go through the burnout process. For simple burnout, a gas ring (old-fashioned type used for canning fruit maybe) can be used. A heavy duty bunsen burner works too. Two tin cans one smaller than the other placed over the casting flask can provide an insulating cover, and high enough temperatures are reached to produce a snow white mould. Cheers. Chris

 

[Tin Falcon]

Sand casting and investment /lost way castings are two different processes.

Sand casting uses a reusable pattern a two piece mold needs good draft cores for holes etc. Sand casting is more economical.

Investment casing allows for more detail and better surface finish but more expensive.
Tin

 

[Dave Sohlstrom]

If you do not have the equipment to burn out for investment casting there is another way to do it.
Do a search on Lost Foam Casting. You make your pattern in foam. Then you add risers and sprues. You place your pattern in a container of fine loose sand with a tall pour cup to give extra head to the pour. Melt your metal and pour fast and non stop. Have a fan set up to blow the smoke away from you.
DO NOT use the foam you can get in a pressure can for sealing cracks in you house. It is toxic when burnt. Use pink or white foam board for your pattern.

There is a lot of info on the internet about lost foam casting.

Dave

 

[kadora]

Thank you guys
On the base of your knowledge is clear that lost wax casting
in sand is not advised .
But i will bury one my wax pattern into sand just for my curiosity .
I will inform you about result.
Sending pictures of my wax pattern.

 

[Dave Sohlstrom]

Have all your safety gear on when you do that because there is a good chance that bad things will happen when hot metal hits cold wax.
It normally take several hours in a burn out oven to remove all of the wax from a flask. Metal is generally poured into the flask with vac assist and the flask is at about 300 degrees F.

Good luck

 

[mcostello]

That may get flaming interesting in a hurry!

 

[kadora]

I am going to melt wax out in kitchen oven then pour hot metal.

 

[Buchanan]

That should work fine, ram your mold real hard and keep it in the oven until there is no more smoke! The sand being hot stops the metal cooling quickly so you should get real good detail.

Buchanan

 

[kadora]

Hello
Sending pics from my pour.
I forgot to install raiser before pouring so that missing parts are
probably results of it.
I am so unhappy.

 

[kf2qd]

Actually, for a first time that really came out rather well. And you learned something in the process. The detail came out pretty well, just need to work on the differing thicknesses. Some of that void near your sprue is because of shrinkage of the material in your casting as it cooled. Might need to use a taller and larger diameter riser to compensate. And maybe the riser needs to feed out towards those ends that did not fill well. What happened suggests that you could also have cooled off you rmetal too quick and it was not able to flow out into those areas, but it could also be that you need to pour more metal.

 

[Wizard69]

Hello

Sending pics from my pour.

I forgot to install raiser before pouring so that missing parts are

probably results of it.

I am so unhappy.

Unhappy??? That is a pretty impressive first for development of a new process. Yes I know the casting isn't perfect but it isn't bad either considering you are experimenting with something that could end up being very useful to the hobby.

As it is to me it looks like your melt might have been on the cool side or you poured too slowly. I'm far from being an expert when it comes to sand casting so take my comments here with a grain of salt. In any event you may be on to something and frankly I'd like to hear more details about how you are doing this.

 

[bmac2]

Hi Kadora.
I have to agree with KF2QD and Wizard. I would have thought that burning out the wax would have dried out the sand too much for it to hold up but your results are actually pretty impressive with a good surface finish. If all you had for a sprue is the bit at the top of the pattern, it’s very impressive. Thm:

A simple way to increase the head pressure is to extend your sprue and vent using 2 cans rammed up with green sand with a hole through the middle. If large enough (I like ¾”, 19mm) this will also help feed the casting as it cools.

I think I might have to give this a try. scratch.gif

 

[kadora]

Thank you guys for your encouraging words.
I have casted a few small obiects to observe what is going on .
I have found that sand soaks 50%-70% of molten wax and probably
during wax soaking on the walls of the sand cavity are created small lumps
and cracks.
I think wax pattern must be separated from sand in some way to protect sinking molten wax into sand.
I got idea to spray wax pattern with thin layer of High Temperature paint.
Surprisingly wax is easy to paint with HT paint spray /for exhaust pipes 650 Celsius/ .
So pattern is painted /Forgot to take picture/ burried in sand and today afternoon
i want to melt wax out of the sand and pour aluminium faster than last time./thanks Wizard69/
I will inform you .

Kadora

P.S.
all your reminders and advices are welcome.

 

[kadora]

Hello
Pictures from today.
On the first pic. you can see separation silver layer of HT paint stick to the sand.
On the last pic is visible that edges are sharper as on previous casting
and casting surface is smoother .
Now i need to find some better separator material.
Any idea ?

 

[Swifty]

It's certainly looking very promising, the surface finish looks great. Just have to overcome that problem area.

Paul.

 

[barnesrickw]

Most of that looks like a very fine casting. Alcoa, once Howmet, Misco, uses lost wax, but then dip the wax blank into a ceramic coating. Sand would be a great deal easier.