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cryogenic machining, plausible?

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  • cryogenic machining, plausible?


    http://www.youtube.com/watch?v=1khOVee8rnk
    12 minute speech here http://www.youtube.com/watch?v=SG2c5MvSnJ4

    -320F through the spindle, at approx $0.10/liter you may want to try this. My interest is how a machine designed to operate at room temperature deals with thermal expansion through the spindle, let alone on the differing contours and chip loads.
    Last edited by Elninio; 11-17-2012, 05:19 AM.

  • #2
    They use a vacuum lined tube that delivers the LN2 to the tooling though that so the LN2 does not come in contact with the spindle. Basically a tubular thermos.

    Kind of neat. I do have access to a 50L dewar. Sounds like a hot summer project though!

    .10/l is only in bulk. This last summer it cost me about $80 to fill up that 50L dewar.

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    • #3
      Best to make sure your ventilation is working
      Amount of experience is in direct proportion to the value of broken equipment.

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      • #4
        And if you though carbide was brittle before... hah!
        Can't see it being much good except on plastics and rubbers. (keep your rubber frozen!)
        And yea, as Jaakko says, Seems like a good way to die. walking into a room full of nitrogen won't make you feel sufficated, you just suddenly become weak and your vision goes black and then you fall over and are dead. And anyone who runs in to rescue you will likey fall over and die before they can drag you out. Its not like holding your breath, inhaling pure nitrogen will actualy leech oxygen out of your blood just like breathing will infuse it, Its becomes the opposite of breathing.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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        • #5
          Originally posted by Jaakko Fagerlund View Post
          Best to make sure your ventilation is working
          Some of that footage was at IMTS -- you can see the crowd walking by the booth

          So they're using liquid nitrogen as coolant -- what's the advantage over flood? I could imagine that it would reduce BUE...
          "Twenty years from now you will be more disappointed by the things that you didn't do than by the ones you did."

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          • #6
            At a former employer I regularly did "cryogenic" machining in the sense that we dipped rubber and plastic items in liquid nitrogen prior to machining for an instant freeze. I dont recall the reason, but we also did that with some ceramics as well.
            "I am, and ever will be, a white-socks, pocket-protector, nerdy engineer -- born under the second law of thermodynamics, steeped in the steam tables, in love with free-body diagrams, transformed by Laplace, and propelled by compressible flow."

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            • #7
              Steels and many other metals undergo a ductile to brittle transition at low temperatures. If the nitrogen is sufficient to cool the metal being machined below the critical temperature, it will go brittle and definitely alter the dynamics of cutting it. If you are using a cutter that doesn't undergo the same ductile to brittle transition as the material being cut, the cutter won't suffer but the dynamics change. Specifically, you could get chips that failed by brittle fracture instead of ductile fracture. Brittle fracture requires much less energy for most materials than ductile fracture and the area around the cut that is disturbed is smaller. I predict that less spindle power is needed at low temperature based on the above argument. It also may make for a finish that one couldn't get warmer.

              One example of the same effect used differently is that cryo tanks are frequently made from aluminum because it doesn't undergo a ductile to brittle transition.

              Tiffiepedia Link for you enjoyment:
              http://en.wikipedia.org/wiki/Ductili...on_temperature

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              • #8
                It's true that aluminum doesn't have a glass transition but it does increase in strength and ductility goes down with temperature. That is particularly the case for unalloyed aluminum which is difficult to machine. At LN2 temps it becomes something like twice as strong and half the ductility which makes it much easier to machine.
                Free software for calculating bolt circles and similar: Click Here

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                • #9
                  Those tools are coated with frost all the way to the toolchanger flange, and how do they set CNC zeroes when those tools will shrink during operation?

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                  • #10
                    Originally posted by Elninio View Post
                    Those tools are coated with frost all the way to the toolchanger flange, and how do they set CNC zeroes when those tools will shrink during operation?
                    Take the shrinkage to account while programming? The same thing as when machining a big mold base, lots f material removed so the workpiece will heat and warp and you just have to take this to acount while programming.
                    Amount of experience is in direct proportion to the value of broken equipment.

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