Trends in Metal Casting

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This part was originally made as a multipiece weldment that required machining of the welded surfaces.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

[crueby]

I've made molds using the two-part silicon molding goop from SmoothOn. No stinky fumes, and it since its a two-part mix it will harden in any thickness. They also have additives for thinning it to allow a good fine detail layer on the part, and thickeners for the outer shells, which make an easy alternative to buyilding boxes to hold the mold shape. Have done several RC boat molds that way for laying up fiberglass hulls, would work fine for casting molds too.

[Jasonb]

Layer lines on castings from printed patterns which I also hate can be dealt with in a similar way to fuming PLA with Acetone. The makers of Polycast Filament make their own Polysher

Couple of videos one about the whole process, the other about the Polysher

https://polymaker.com/product/polycast/

https://polymaker.com/product/polysher/

[CI]

Generally speaking, I make castings when I get a rare break from work projects.
A typical casting session starts perhaps 2:00 PM, when I make molds.
The molds take about an hour to set up/make, then a hour to full cure.
Then ceramic mold coat, burn-off, flaming the mold, adhering the mold halves together, and then start the furnace, so perhaps another hour.
Cast iron melts require about 1 hour, with a pour at the end of that time period.
After than the mold sits overnight, so it is just a matter of covering the furnace and burner, and I am done for the day.
I generally let the sun get mostly down or fully down before I start the furnace, due to how hot it is in these parts.

So I can walk out, do a session in an afternoon, and have a cast part or parts in the early PM of the same day.
I have started leaving most of the casting equipment out in the driveway, and have remote mounted my combustion air blower so that it can always be located indoors.
Dragging all of the foundry equipment in and out of the shed every time is too time consuming, so the non-critical items remain outdoors under a cover.

With investment casting, there is no way I can have a casting in the mold in four hours.
I suspect investment casting may be a multi-day affair.

With bound sand, the probability of getting a good casting is very high, since there is not a problem with shell cracking, etc.

I think the greensand folks could make castings in less than four hours, in iron, especially with a coated ceramic blanket-style furnace.
The molding takes more time than the melt/pour, for me.

The lost PLA is problematic due to the lines that occur in the castings.
I see Jason has found one solution to the line problem.
I have seen some who apply something to the exterior of perhaps PLA to smooth it, but I don't like the melted look of those PLA patterns, since it degrades the sharp lines, and as Jason mentions, you can't reuse the pattern repeatedly.

With bound sand, multi-piece molds can be made and adhered together, so there are not too many things that investment will do that resin-bound sand cannot do.
One does not necessarily have to be able to pull the entire pattern from a mold; it can be molded in sections.

Investment casting is for super high quality surface finish, lettering, etc., and a very complex casting.

.

[vtsteam]

Speaking of wax for casting, I'm going to try using wax fillets on patterns soon. Haven't tried that before. I've got beeswax and what we call paraffin (hard wax) here, and I'm going to mix my own and extrude it.

[CI]

I have seen someone recently (can't remember where) using wax and/or leather fillets.
I think the wax fillets are smoothed with a heated ball.
I can't recall all the details; seems like there were strips of wax.

.

[Jasonb]

The preformed strips need a heated tool to apply. You are basically ironing them into place with a hot ball which not only melts them onto the surface buut softens them so the follow curved junctions. You buy the wax in different radii.

https://www.artisanfoundry.co.uk/product_info.php?products_id=195

Beware the softer wax that comes in a block and is often sold for composites, this softens in the hand and is pushed into the corner like a putty then smoothed with a unheated ball. It is a lot softer so you may get problems with raming the sand and in Pats climate it will stay even softer.

The other option is you want to avoid sanding is to use a 2 pack putty, mix roll into a sausage and push into the corner. Then take a ball dippe din water and pull along the junction. This forms the radius and leaves the excess either sid ewhich is easily removed. Finish blend with a bamp paint brush. White Milliput used in the images below to get a cast look on fabrications