3 ms·

right now, I'm trying to figure out if fabricated steel with the right design can accomplish a functional analog of what cast iron can. the objective is to leve

right now, I'm trying to figure out if fabricated steel with the right design can accomplish a functional analog of what cast iron can. the objective is to leverage flat pack laser cut pieces instead of castings.

kragen 3y ago
it can certainly be equally rigid if that's what you're after; they have very close to the same young's modulus. thermal stability and vibration absorption is more challenging i think castings often come out closer to net shape than weldments and thus need less final machining, but i could have that backwards. they both shrink as they cool, but weldments don't need draft
- abakker 3y ago
  Weldments have less shrinkage/distortion than castings, but not none. In machine tool applications, it's the vibration damping that everyone cares about, but my ultimate objective will be to find out whether it matters if you engineer in sufficient rigidity. Theoretically, for the vibrations to be an issue you'd need to get some resonance, so if you tune that out in the design spec it should be something that can be ignored. Nothing like empirical testing, though.
  - kragen 3y ago
    i see, thanks! i wonder if sand bonded with sodium silicate could provide vibration damping at a much lower cost than cast iron or epoxy granite? you'd want to use much more sodium silicate than you normally use in foundry practice to get a continuous silica hydrogel phase without air-filled porosity, and as with epoxy granite, you could make the members much thicker and probably heavier than you would with steel or cast iron in order to achieve the same rigidity. and sodium silicate should make an excellent bond to either quartz or carborundum (or other silicate aggregates like basalt fiber) i think people also care about rigidity because side-loading induces tool deflection, which hurts precision, not just because of chatter but i don't know anything

kragen 3y ago

it can certainly be equally rigid if that's what you're after; they have very close to the same young's modulus. thermal stability and vibration absorption is more challenging i think castings often come out closer to net shape than weldments and thus need less final machining, but i could have that backwards. they both shrink as they cool, but weldments don't need draft

abakker 3y ago
Weldments have less shrinkage/distortion than castings, but not none. In machine tool applications, it's the vibration damping that everyone cares about, but my ultimate objective will be to find out whether it matters if you engineer in sufficient rigidity. Theoretically, for the vibrations to be an issue you'd need to get some resonance, so if you tune that out in the design spec it should be something that can be ignored. Nothing like empirical testing, though.
- kragen 3y ago
  i see, thanks! i wonder if sand bonded with sodium silicate could provide vibration damping at a much lower cost than cast iron or epoxy granite? you'd want to use much more sodium silicate than you normally use in foundry practice to get a continuous silica hydrogel phase without air-filled porosity, and as with epoxy granite, you could make the members much thicker and probably heavier than you would with steel or cast iron in order to achieve the same rigidity. and sodium silicate should make an excellent bond to either quartz or carborundum (or other silicate aggregates like basalt fiber) i think people also care about rigidity because side-loading induces tool deflection, which hurts precision, not just because of chatter but i don't know anything