Robert Campbell Jr.
Diamond
- Joined
- Aug 20, 2006
- Location
- Hesperia, SoCal
I have need to cast a couple of small parts that cannot be sand molded, as parts of a larger Petro-Bond casting. I know that the foundry industry uses expanded polystyrene foam, because of the near instantanious and residue free void left as molten metal comes in contact. My foam patterns must be formed over irregularly shaped sodium silicate/CO2 sand, (or any other kind) cores.
In spite of the fact that modern automotive foundry practice utilizes millions of intricate lost foam patterns, patterns that because of their intricacy and volume, must be formed in molds, I can't seem to track down the exact process, nor base materials.
My searches seem to indicate that expanded Polystyrene is distributed as tiny pre-expanded beads that are somehow delicately fused in molds, but the proccess escapes me. I guess my question is, "how do you make a Styrofoam coffee cup?
Yes, I've whittled and smoothed Styrofoam patterns but accuracy and surface finish is lost and volume approaches nil.
I tried Polyurethane spray foam in a mold, it made a foam pattern with fine detail, however, it's not nearly as afraid of molten aluminum as Styrofoam and leaves nasty residue and mal-formed castings, in spite of the fact that I provided large passage ways, (and will for the Styrofoam) to vent the large volume of generated gasses.
No, in this project, large blobs may not be cast and excess machined away. Billet is not an option.
I've haunted foundry forums to no avail, so all answers much appreciated, even those that start, "Are you stoopid?" then list a thousand easily attained, spot on links, or, "Did you look in the 1918 edition of Machinerys Handbook where an entire chapter....." My ego doesn't bruise easily, my need is much greater than my pride.
Checked one more time, yup, still says, "Welcome to the Manufacturing Forum." Note; this is my very first request for help, still, no need to be kind, just informative.
Again, thank you very much in advance, Bob
In spite of the fact that modern automotive foundry practice utilizes millions of intricate lost foam patterns, patterns that because of their intricacy and volume, must be formed in molds, I can't seem to track down the exact process, nor base materials.
My searches seem to indicate that expanded Polystyrene is distributed as tiny pre-expanded beads that are somehow delicately fused in molds, but the proccess escapes me. I guess my question is, "how do you make a Styrofoam coffee cup?
Yes, I've whittled and smoothed Styrofoam patterns but accuracy and surface finish is lost and volume approaches nil.
I tried Polyurethane spray foam in a mold, it made a foam pattern with fine detail, however, it's not nearly as afraid of molten aluminum as Styrofoam and leaves nasty residue and mal-formed castings, in spite of the fact that I provided large passage ways, (and will for the Styrofoam) to vent the large volume of generated gasses.
No, in this project, large blobs may not be cast and excess machined away. Billet is not an option.
I've haunted foundry forums to no avail, so all answers much appreciated, even those that start, "Are you stoopid?" then list a thousand easily attained, spot on links, or, "Did you look in the 1918 edition of Machinerys Handbook where an entire chapter....." My ego doesn't bruise easily, my need is much greater than my pride.
Checked one more time, yup, still says, "Welcome to the Manufacturing Forum." Note; this is my very first request for help, still, no need to be kind, just informative.
Again, thank you very much in advance, Bob