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Trends in Metal Casting

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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.

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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.

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