Lost Foam casting makes it possible to cast some parts that would require some very intricate wood patterns. I use foam for those types of castings. If it does not turn out, cut some more foam! Actually, it is great for some "quick and dirty" castings as well. If surface finish is not critical, lost foam can produce "one off" castings faster than making wood patterns. To date, the few lost foam castings I have done all turned out as hoped. These castings are normally done in "loose sand", no ramming, and the sand is dry. The only place for some moist sand might be around the sprue so it does not collapse. Using thin aluminum tubes (soda cans, etc), for sprue holes, makes it easier. I am using fine grit sandblasting sand at present. My first lost foam was done in Petrobond, but the burned foam does not do much good for the Petrobond sand. There is much more to be said regarding lost foam, I would suggest checking some of the excellent websites out there. Thats what I did.
Using foam for patterns requires a means to cut it. A "hot wire" cutter is the most popular, so I built one. It has some nice features, and others that I should include if I ever make another. It would be nice to be able to tilt the cutter wire for angles, as well as adding a good fence to guide the foam as it is being cut. Presently I clamp a straight edge to the table, OK but not very repeatanble.
The wire is connected to an adjustable spring loaded nut. The spring keeps tension constant, the knurled knob adjusts tension.
This is an auxillry cutter made from heavy wire, to cut curved shapes. The wire is easily replaceable, and the loop can be adjusted vertically.
The power supply uses a Variac, 0 to 56 Volts, and a 24 V transformer for isolation. The Variac was left from a project abandoned long ago, finally has a good use. I presently have screw terminals to connect the cutter, but will be putting some sockets for jacks as a better method of connecting.
I used lost foam castings for both my IC engines ; there are pics of them on those pages. Shown below is my very first lost foam casting.
Not knowing better at the time, I made the pattern of white "bead stryofoam". It has a tendancy to produce a lot of texture on the surface, undesireable in most cases. This pattern still needs a sprue. The resulting casting (with sprue attached) is shown on the right.
The casting after milling the top and feet flat. It was used as a base for the water jacket on my Atkinson Engine..
One item that is high on my "to do" projects list is a small lathe to hold foam pieces for cutting circular shapes, such as pulleys, etc. I saw the concept for one on another website, and it has lots of potential.
