Just thought it might interest some RYPN'ers that the LMS Patriot Project in the UK have just had the middle cylinder for their loco cast using the lost foam process. There are some photos of the pattern and screenshots of the CAD work here:
https://www.national-preservation.com/t ... 46/page-15
and of the casting here:
http://www.prw.com/subscriber/featured2 ... redid=2916

The difference in price for the pattern was quoted as £2800 (~$4400) for the polystyrene pattern, and £35,000 (~$55,000) for the traditional pattern, so that was a significant saving. The caveat (as I had commented on at NatPres) was that the CAD work was done by a volunteer, so they were saving a lot of cash on design work that way.

Worth investigating for those complex castings, though.

Ed- Very interesting. The one thing I didn't see explained was how was the polystyrene pattern made? It seems like it should be possible to use 3D printing for this.

I believe the pattern is made on a 5-axis mill, in layers so that the mill has access to the part.

At the size we're talking about, 3d printing would be an incredible expense!

Never a better time to build a new locomotive........imagine if General Steel Castings had the ability to do things like this in 1940?

I think we had a headlight bezel 3DP'd a little while ago....I'll find out about it. Eventually.....when I can get to the right people.

dave

There's also a low budget version of it shown here:
http://www.buildyouridea.com/foundry/lo ... howto.html

Essentially - take some insulation foam, carve your part (with shrinkage allowance!), pack with green sand and off you go!

The technique has been around a long time, at least since the early 70's. I remember my art teacher in high school showed us an aluminum casting she'd made using this technique to represent a branch, leaves, and seed pod from a gum tree.

They can do high-volume production of castings this way too, because you can die-cast the polystyrene patterns, making it very easy to turn out many patterns quickly.