Lost Wax Investment Castings
Lost Wax Investment Castings
(OP)
What is the difference between silicon and water glass in an investment casting. The water glass method seems to be much cheaper and poorer surface finish. Secondly, what is the the Investment cast process that yields the best surface finish and closest to "near net shape" . The parts are approximately 5 in. in Dia. and valves for a pump and therefore need to be very smooth. See drawing attached.





RE: Lost Wax Investment Castings
There are a number of different slurry wash systems. How the metal reacts with the shell is important also.
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Plymouth Tube
RE: Lost Wax Investment Castings
Getting a near net shape by investment casting is possible and a discussion with die maker and the foundry will help.
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"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year
RE: Lost Wax Investment Castings
I'd expect considerable difficulty filling the investment cavity without producing lots of flaws, but I'm not a founder.
Similar parts almost always extend the guide ribs all the way to the valve plate proper, without necking things down to a shank like the .900 diameter. I suspect there's a reason.
Mike Halloran
Pembroke Pines, FL, USA
RE: Lost Wax Investment Castings
It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.
RE: Lost Wax Investment Castings
Cast parts in general, but more important in gravity fed than pressurized(diecast, centrifugal etc.). Try to avoid areas like the .900" central shaft because it restricts the flow of material during cooling and will result in large amounts of porosity in the area beyond the restriction.
Comprehension is not understanding. Understanding is not wisdom. And it is wisdom that gives us the ability to apply what we know, to our real world situations
RE: Lost Wax Investment Castings
RE: Lost Wax Investment Castings
RE: Lost Wax Investment Castings
With shell if you go to finer sand to improve finish you get less venting and may have more gas defects. It is a delicate balance.
With investment they can pick a particle size for the first coats to give surface and then move to coarse to give enough strength.
They can also change the mold temp at pour to control fill and solidification.
Investment will cost more but has the chance to deliver a vastly superior part.
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Plymouth Tube
RE: Lost Wax Investment Castings
For surface finish the most important factor is the prime coat. Thicker slurries give better finish, as do finer stuccos. As previously pointed out, however, both these factors can lead to gas defects.
With this part in particular, it may be a lengthy development process as the part has a chunky section in the middle and no easy way of gating to it through a thick section.