Waterjetting 4" A36 Plate
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    Default Waterjetting 4" A36 Plate

    I need to make two spacers, 4" thick and approx 17" X 13" square with a large part of the center cut out. Should I expect these plates to move around a bunch after cutting? I would guess water-jetting results in much less stress than O/A or plasma would. These spacers will need to be surface ground after cutting and I don't know if I need to normalize them in a oven first. I'm guessing that would be the smartest move.

    Stuart

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    waterjet is super low stress inducing but it depends on tour material. In my experience cold rolled sheet stock, up to 10 ga say stays flat but I have cut 1/2"x4" cold rolled bar for example that has both the cut part and remaining material move in different ways. 1/2" hot rolled plate from which we gave cut larger parts seems to stay flat. So normalizing might be a good idea but maybe cut the parts and see. 4" steel is pretty thick for waterjet though. I suppose you've thought about a weldment if it was a simple shape if you were going to normalize and grind anyway.

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    My experience say that 4" thick plate has stress's in it right now.

    Cutting even with a waterjet (or bandsaw etc) will allow warping.

    So if you have to pay for stress relief anneal anyhow, might
    as well go with the cheaper Oxygen process.

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    Quote Originally Posted by digger doug View Post
    My experience say that 4" thick plate has stress's in it right now.

    Cutting even with a waterjet (or bandsaw etc) will allow warping.

    So if you have to pay for stress relief anneal anyhow, might
    as well go with the cheaper Oxygen process.
    I've thought about that but am hoping the finish edge with waterjet will preclude any post cut machining..O/A at this thickness would probably need a clean up to look decent.

    These spacers are for a Haas GR510 gantry router which has flame or jet cut parts in abundance..good edge finish. I want to at least match that.

    Stuart

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    Quote Originally Posted by atomarc View Post
    I've thought about that but am hoping the finish edge with waterjet will preclude any post cut machining..O/A at this thickness would probably need a clean up to look decent.

    These spacers are for a Haas GR510 gantry router which has flame or jet cut parts in abundance..good edge finish. I want to at least match that.

    Stuart
    This statement makes NO sense.

    If your wanting to MATCH flame cut, then why aren't you
    having it flame cut ?

    Have you seen what a good operator can doo flame cutting 4" plate ?

    I had a chunk cut one time 9" thick and it was just fine.

    The most obvious "ugly" will be the rolled over edge on top, from
    the preheat flames.

    If your going to Blanchard grind, blue the bottom, grind that side
    to clean up.

    Take the majority from the top (to get to size) and most of
    that round over will be gone.

    Also, stress relief anneal followed by steel shot rotoblast
    will blend things pretty good.

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    digger, what 4" plate did you find has internal stress, and how much? like it warps 8 thou a foot on a thin slice, (say a 6" wide strip?), or worse.. like it turned into a banana? what material and cutting method?

    for the 17 X 13" size, I would think a hot rolled plate would be reasonably stable if you stay away from the edge of the plate (depending on how much of the center is cut out, and how symmetrical). the cooling rate would be pretty slow for that at the mill, even with water spraying on the slab.

    as far as the cutting method, Oxy-fuel is the only way to go, for something surf groung after cutting, water jet is going to be slow, slow, and very expensive, and may warp anyway.( unless it has a very complex or intricate profile)

    having a hard time thinking why stress relief is justified.. what is the flatness tolerance you are trying to hit? how narrow is the skinniest bit?

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    It was a long time ago, and I always had it stress relief annealed
    to avoid the problems.

    Other employees did not order stress relief, and I heard the complaints,
    how much I can't recall.

    So as I wrote before, I would anneal anyways, as a safeguard
    to all the time put into machining it.

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    I haven't had much cut via waterjet, but I have done plenty of 4" on an oxyfuel torch. The torched edge IMO is a little nicer looking, outside of the point where the torch lines intersect, which can be cleaned up with an angle grinder in short order.

    I would not want to pay for waterjet on 4" thick steel when oxyfuel is an option.

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    How thick has it got to finish? ......too much warp - which you will get how ever it's cut (only the amount varies ) and you could run out of thickness in Blancharding.

    FWIW I would definitely stress relieve, .even taking the skin off one side of HR will curl it, then you're left ''chasing'' it flat again.

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    as always,it all depends on the tolerance you are going for. yes, if .002" is going to matter, normalize. I wonder how much a slab of 4" HR would move around if you "skinned off one side"? just curious at this point..

    HEY, Limy, you have about an hour to go, but happy new year!

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    Quote Originally Posted by cyanidekid View Post
    as always,it all depends on the tolerance you are going for. yes, if .002" is going to matter, normalize. I wonder how much a slab of 4" HR would move around if you "skinned off one side"? just curious at this point..

    HEY, Limy, you have about an hour to go, but happy new year!
    And to you and yours Cyanide.

    As to how much 4'' plate will move when skinned? IME when skinning almost anything it will move, how much depends on a multitude of factors that are outside our control, .....I've had bits of HR flat bar change how much they react down the length of a single 10 or 20 ft bar,......like 1 bit 0.005'' okay we can handle that, etc etc ..only to find the next piece move more or less.

    Aluminium and plastics can be / are even worse, and I've had bronze castings move almost beyond recognition.

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    There is no arbitrary finish thickness..only that the spacers are flat and the same thickness. I do not want to fuck around cleaning up the edges of these things..if a flame cut edge in 4" material can come out comparable to a flame cut edge in 5/8" material then I could live with that. I'm not familiar with cuts in plate that thick but the few I've seen were not that nice..maybe it was operator error!

    So it appears the answer to my original question is, that whether jetted or flame cut, it would be prudent to normalize before grinding to assure a flat plate in the end.

    Stuart

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    You've got it Stuart FWIW a good burner - that knows his job, will get a good edge on material of almost any thickness.

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    I have a 600# piece of 4340, 8" thick, where the flame cut edges are not significantly rougher than the top and bottom.

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    Everything I have had waterjet had slightly tapered sides rough from the abrasive. I also vote for flame cutting.

    metalmagpie

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    I bought a large section of sawed mystery iron from a rem yard once. 3-4" thick. Didn't take long to figure out it was a piece of a very large forklift fork I had just bought and it was surgically torched on the ends. Nice enough to look sawed at a glance. They did give me my money back.

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    Quote Originally Posted by atomarc View Post
    There is no arbitrary finish thickness..only that the spacers are flat and the same thickness. I do not want to fuck around cleaning up the edges of these things..if a flame cut edge in 4" material can come out comparable to a flame cut edge in 5/8" material then I could live with that. I'm not familiar with cuts in plate that thick but the few I've seen were not that nice..maybe it was operator error!

    So it appears the answer to my original question is, that whether jetted or flame cut, it would be prudent to normalize before grinding to assure a flat plate in the end.

    Stuart
    Stuart,
    When you folks were here last year, I could have shown you a 3½" thick ring of A36 ready to be turned in my big lathe. It was setting right there by the lathe. The shop south of here has one of the nicest burners around. It ain't the finish like we're used to seeing.

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    Ray,

    That was the reason behind the waterjet thought..a good edge finish. I haven't seen enough thick plate burned with a CNC torch to realize that they could achieve a nice edge finish. It looks like flame cutting by a experienced shop will be the best and most cost effective choice.

    Stuart


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