It's been a really long time since I did a lost foam casting. As many of you know I'm pretty much a dyed-in-the-wool conventional greensand caster. And I actually like making wooden patterns -- maybe as much as casting metal itself.
Nevertheless, there are some things you can do with lost foam that are difficult or impossible with conventional casting. Complex undercuts, deep draftless and narrow dimensioned parts, and big changes in dimension with a resistance to forming shrink cavities.
The drawbacks to lost foam are foam dust, foam melting fumes, the need to make up a new pattern for every part cast, more rapid contamination of sprue and supporting metal for remelting, and very different orientations and methods for getting sound castings. I don't find lost foam casting pleasant. But occasionally it serves a purpose, at least for me.
So this time, I wanted to give it a try again for a water-cooled hot air engine block casting in aluminum. This is an adjunct for my No. 83 engine experiments. If I build a much larger engine in the future, lost foam casting may become important to reducing the thickness and weight of aluminum needed, compared to a model sized engine.
For the present, I'm still working with an average 1" bore size engine, as a test of lost foam methodology. I drew up the shape I wanted in the old free Google SketchUp and then through a long series of graphic transformations got that shape into a cutting file for my old foam wing cutting software, JediCut. This runs on my CNC hot wire foam cutter.
I won't go into all the work I had to do just to get that shape to cut, but it was NOT the most fun part of this project! I could have made 10 wooden patterns by hand in the time I spent eventually getting one CNC foam pattern cut

Anyway, here it is, finally....with some flaws. There's a piece of excess at the top, a bad lower left hand corner (defect in the scrap foam piece I was cutting from) and two gaps where the wire had to cut through to get to interior hollows. Those will all be plugged with glued foam bits.