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Trends in Metal Casting

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CI:
I follow the journal "Casting Source", and they do a good job of detailing recent advancements in metal casting.

Here is one example from an article by Jiten Shah, Product Development & Analsysis (Naperville Illinois).

The alloy is ASTMA743/CF8c stainless steel.
Overall size is 6.7 in. x 4.3 in. x 2.8 in.
Casting weight about 1.0 lbs.
Investment casting method.

This part was originally made as a multipiece weldment that required machining of the welded surfaces.

The ceramic shells are preheated, which allows for thinner walls in the casting.
Looks like the minimum wall thickness is 0.04 in., which is exceptionally thin for a casting.

Multi-piece wax dies are used with little or no draft angle.
Multiple random parting plane orientations.
Pressure tested for leakage to 51 psi.

I have also seen similar articles about other weldments converted to the ductile iron casting process, also with near-net size, minimal and sometimes no machining required, lighter castings with as much or more strength than steel, and a less expensive casting due to the lower melting point of iron, and a more simple casting process.

Photo from Jan/Feb 2026 Vol. 28 of "Casting Source".

I have been researching how to make ductile iron, and also have been searching for additives to use for that process.
I have located some nickle-mag, and also found some ferro-mag.
I think both will work with making ductile iron.
All I need now is a bit of time to make a reaction chamber.
Crankshafts are the main thing I would like to cast in ductile iron, but there are other things that may also be a good use for this material.

Edit:
The ceramic shell process is several steps more complicated than I want to go at this point, but I think I can get some decent castings with bound sand molds with ceramic mold coat that may be close to what can be done with ceramic shell, but not quite as thin as the example above.
I have seen some pretty good results with small castings using vacuum assist, so that may be a consideration.
Bound sand is not particularly porous, and so I am thinking the vacuum would have to be applied to the top of the cope, with a shop vac or something similar.
The pressure would have to not be too excessive, else you could end up entraining a lot of air into the molten metal stream as it fills the mold cavity.
.

Jasonb:
If you used something like Polycast filament to print the "waxes" rather than use dies to cast the multiple pattern pieces then you could do away with all the parting lines as you don't have to get the waxes out of a mould. Also saves having to assemble the waxes a syou would just print as a single part as printing does not need to work about undercuts or draft etc

Even if you did use traditional wax some time spend cleaning up the waxes after assembly would again do away with all parting lines that can be seen in that photo.

Dies and cast waxes are probably more economic for mass production but for home then a printable wax would be a better bet.

vtsteam:
Printable wax would be good for home investment casting if the print lines were finer than what I typically see on home 3D PLA printers -- at least affordable ones.

I've never been attracted to lost wax because of the requirements for much time and heat energy for burn-out and the need to recreate a pattern every time you cast -- but I can see why high value small intricate and undercut castings like detailed replica engine parts, jewelry and statuary are done that way.

I do basically crude large castings of substantial metal weight, and also (this isn't often mentioned, but extremely useful aspect of home foundry use) casting stock rectangular bar stock, heavy wall tube, rod, and disk from scrap like disk brake rotors. For these purposes sand casting using patterns that can be reused immediately, or in several flasks at once, comes into its own. Particularly for iron, where investment methods on a home scale are still not ....I don't want to say viable, but at least not well documented compared to sand casting.

For more more intricate medium to large size home castings with undercuts where absolute fidelity of wax investment isn't required, I think lost foam has a place in the arsenal. Especially if you have a cnc wire cutter. It does not require burn out as a separate operation.

CI:
I have to agree with what others are saying; the investment process burns up the pattern with each casting, but also requires one to make a permanent mold that is used to make the wax pattern.
And the commercial investment slurry material is said to have a short shelf life.
I have resin binder that still worked after 10 years in a hot and cold shop environment.

The burnout process is another step, and uses fuel (as mentioned above), and I have read that the investment often cracks during the burnout process.
There is definitely a place for investment casting, but it is many steps above sand casting, and some of those steps are financial; other steps are are time involved.
With the investment process, I presume a very good pattern is made first, and then the mold used to make the wax parts must be cast around the pattern in a hard plastic or something similar ?

I am good with using bound sand, and I see that as an economical and time-effective middleground between regular greensand and the investment process.

I am definitely interested in vacuum assist, given all the thin walls on the Ball Hopper Monitor.
For the water hopper, I will use a gate around most or all of the bottom of the hopper, without vacuum assist first.
If that works, then no need to use vacuum.
You know my adage with foundry work: "Don't fix problems that you do not have".

.

Jasonb:
You usually use RTV silicon to mould from the master. Makes it easier to peel away from the wax and allows a small amount of undercut. You would not be able to do that with a hard plastic.

Certain mass produced items may cut metal dies rather than make a master and rubber moulds as the metal is more durable but like pulling a pattern from sand only works with certan shapes. That is why in your article it talks of multiply dies, each being used for a part of the main wax to ease removal.

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