Pattern/Rapping fail Sailboat Part

Discussion in 'Sand Casting' started by Tops, Jun 12, 2022.

  1. Melterskelter

    Melterskelter Gold Banner Member

    I'd use the 1/2" having done a lot of aluminum castings of roughly that size with the 1/2" straight sprue and having had it work reliably. I can't think of when I've use a sprue larger than 5/8." I'd be interested in other folks' experience.

    Denis
     
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  2. SRHacksaw

    SRHacksaw Silver

    Those are wide shallow cores, maybe what 10" x 8" x 1.75" deep I'd probably ram them fairly hard, as well. Deep narrow cores are where the problems with too hard ramming come in. It's a judgement call how hard for what configuration.
     
  3. SRHacksaw

    SRHacksaw Silver

    If you pour large castings with half inch dia sprues you have to pour hotter than necessary in order to fill the mold. Your casting is dull gray in the photo, and that says to me you pour hotter than I like to. Different folks different strokes.
     
  4. SRHacksaw

    SRHacksaw Silver

    65 pounds in that...... is that an iron pour? It's hard to imagine 65 pounds of aluminum even in a casting that size and shape.....


    Edit:

    Yeah the sprue looks like iron, I guess you switched gears from aluminum here, so gray is the norm.
     
    Last edited: Jun 15, 2022
  5. FishbonzWV

    FishbonzWV Silver Banner Member

    The sprue you used did a fine job of filling the part.
    No need to change.
    Soft ramming between the flanges keeps it from locking in. The rest of the pattern, ram as normal.
    Edit: The same applies to the cup shape there, ram the center of the cup and as you get closer to the edge you back off the ramming.
     
    Last edited: Jun 15, 2022
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  6. Melterskelter

    Melterskelter Gold Banner Member

    Those are shallow wide patterns not cores. Cores are

    "A core is a preformed, bonded, sand insert placed into the mold to shape the interior of a casting or a part of the casting that cannot be shaped by the pattern. Cores are frequently used to create hollow sections or cavities in a casting."

    I beg to differ that I am pouring hotter than needed. the casting shown was poured at 2525F---a very commonly recommended temperature for iron. And for aluminum I routinely cast at 1300 to 1350 F + or -. If you look down through this thread I casted a lot of parts of equal or greater mass using sprues less 1/2" diameter. You can just see them in a couple pics and you can see the indentations form the ends of them on couple of molds.

    http://forums.thehomefoundry.org/index.php?threads/free-3d-flask-pattern.1300/page-5

    I am not saying anyone is casting too hot, too cold, too large a sprue or too small. I am simply saying that my experience does not square with some other reported experiences. So the reader should take both with a grain of salt and decide what works for them. (I would be cautious about saying someone is casting too hot or cold without even knowing what temps they are using. And sand molds the same whether used for aluminum or iron---an illustrative pattern can be used from either to make a point.)

    Denis
     
  7. FishbonzWV

    FishbonzWV Silver Banner Member

    I use vents on my large plaques to keep from getting sand float. My venting tool is a piece of aluminium arrow. I'll lay the cope on the bench, top down and push the arrow though from the cavity. Nice clean hole.
     
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  8. SRHacksaw

    SRHacksaw Silver

    Hey Melter, greensand cores. Look that term up.

    And your iron pour photo in the middle of a post about aluminum was confusing visually. Apologies for the misjudgment. Also, impressive to me that you did pour 65 pounds of iron through that 1/2" sprue. I'll remember that.
     
  9. SRHacksaw

    SRHacksaw Silver

    Gingery: "A core that is left in the mold by a pattern is called a green sand core"
    Aspin: "The sand core in it's most elementary form is that which is simply left in the mould in greensand by a hollow in the pattern itself. Greensand cores need to be well penetrated by the venting rod."
    And,

     
  10. Tops

    Tops Silver Banner Member

    Fumbled around a bit in the garage and sorted/added to the sprue can, indexed by inch mark:
    tops_o14_sprues_etc.jpg
    10. same as 11 but shorter, printed a couple weeks ago, don't see a need for this one
    11. used before, original tapered sprue print based on Olfoundryman channel on YT
    12.-14. each 1/16"(1.6mm) larger on small end than previous, printed last night, need to sand, fill, wax, graphite
    15. 1/2" EMT, tried, did not like. did not seem to cut, maybe too dull or thick or deformed
    16. remembered I had this old brake line, cut off flare, beveled end
    17. found a 1/2" (12.7mm) dowel in the dowel can
    18. forgot I had this old brush handle already in the foundry stuff
    19. found this 1/2" ID copper tube deep in a cabinet
    20. 5/8"(16mm) used before or at least coated in wax and graphite seems big to me now
     
  11. Melterskelter

    Melterskelter Gold Banner Member

    I have looked the terms up in the past and I relooked today at your suggestion.
    Now I will suggest you look up "Core" and "Mold" and "Pattern"
    In the following resources:
    1) American Foundry Society Glossary of Terms
    2)US Navy Foundry Manual
    3)Atlas Foundry Glossary of terms
    4) C.W. Ammon's books
    4) Ask any commercial foundryman his definitions. Ask anyone on this forum how they use those terms.

    You will find unambiguous definitions of those terms that all line up and certainly do not agree with Gingery. So, if Gingery uses terms in a very peculiar way, I am surprised, but that is his option I guess and yours as well. On the other hand, it may cause confusion as I believe that is not the way they are used by 99.99% of people interested in foundry work.

    Denis
     
  12. Melterskelter

    Melterskelter Gold Banner Member

    Well, that should cover most needs...:)

    Denis
     
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  13. Tops

    Tops Silver Banner Member

    Circling all the way back to this, specifically #3 :

    I see a pattern in my ramming (?!?) in that I 'chicken out' for making runners of any length. This one the sprue dropped down into a splash basin and the metal only 'ran' for about 3/4" (19mm) each way before a corner and a small gate into the flanges. I was trying to sneak it into a part of the part that would file/sand easily and it also seemed to keep the more critical sections in the drag and in hot metal. Is there a guideline for how much 'run' to have? Should I have drove a couple more inches before going into those ends or gated somewhere else on the pattern?

    I really do not need multiples of the part but it would be nice to try/use the work into the pattern. Would there be any merit in converting it to a match plate after detailing some of the fillets and smoothing the flat surfaces that ate sand last time? Would that prevent over-ramming in some places or make it altogether easier or harder to pull? I have yet to try one.
     
  14. FishbonzWV

    FishbonzWV Silver Banner Member

    I use runners on most of my patterns. I have a 4" one that I use quite frequently. I'll place it so there is an inch for the metal to flow past the gate. That's for any sand wash to get trapped in the end and not flow into the cavity. I used to use splash basins but got rid of them on the advice from Olfoudryman. It's a place to ingest air into the melt. My runners are tapered on both ends for a smooth flow from sprue and no 'wall' at the far end to cause a shock wave.
    No, that was perfect.
    Match plates are usually used for production runs. For a one-off it's a waste of time and effort.

    My little 4" runner, cross section of runner should be close to sprue cross section.
    IMG_2979.JPG
    IMG_3865-horz.jpg IMG_3860-horz.jpg
     
    Last edited: Jun 16, 2022
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  15. Tops

    Tops Silver Banner Member

    Awesome, thanks. I love the torpedo/bullet/eagle cleats. What does the other piece do?
     
  16. SRHacksaw

    SRHacksaw Silver

    Melter, we all learn casting from someone. The three brilliant men I learned from used the term the way I do now. Terms vary in trades and crafts, and change over time, geography, etc. I don't want to bog this thread down with semantics and who is "right". You do understand now what I was saying, and that's the main thing. I will probably continue to use the term greensand core the way I do, and have for 20 years. Likewise I respect your choice not to. If need be I'll be more explanatory in posts where it might create confusion.
     
  17. FishbonzWV

    FishbonzWV Silver Banner Member

    Amacetta1 small.jpg
     
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  18. Tops

    Tops Silver Banner Member

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  19. Tops

    Tops Silver Banner Member

    Decided to add Bondo to the places that grabbed sand and can take a larger fillet. I also ordered some spot putty to try the spray method outlined by Rocketman. I am getting into a 'Bondo' state of mind, enjoying the process and the added weight to the 3D printed patterns. Need to figure out how to sand the small recess between the flanges...
    Tops_o14_bondo2.jpg
     
  20. Melterskelter

    Melterskelter Gold Banner Member

    A card scraper can be used to remove most of Bondo and if shaped with a radiused (or several different sized radius corners) can go a long way towards "taming" bondo fillets as can thinning the bondo with a little polyester resin prior to application. I use scrapers to get the Bondo close to shape and then use small torn off rectangles of 80 or 120 grit SiC paper gripped with fingers and pushed by my index finger to reach down into such places. Or contact cement it to a piece of dowel. I have three special screwdriver-like scrapers with the tips bent down and sharpened for reaching into crevices. A Dremel or Foredom is helpful. Lots of ways to skin the cat.

    Pics of home made scrapers later---I used o-1 tool steel, but I think some random screwdrivers with the tips bent at a near right angle and contoured as desired would be an easy way to make them.

    Card scraper sharpening:


    He is showing a rectangular scraper. But he could also have radiused all four corners and sharpened them too. I have a nice little rectangle about 3/4 by 2 inches with radii. Nice for reaching into recesses.

    Added: Pics of what I use
    Scrapers.JPG
    Here is an image of my rectangular scraper in a piece of wood used as a crutch to help me keep the face perpendicular to the stone as I sharpen it. Not really required, but makes the job just a little easier. The bent scrapers are sharpened freehand using the same stoning and burnishing method as shown in the vid. The small scraper gets used most often when making pattterns and that funny little rounded protruberance in the right upper corner is the part of it most commonly used. Any hardenable steel will make a durable scraper and even soft steel can make a very serviceable one. A soft one will just need more frequent sharpening.
    Scrapers2.JPG


    Denis
     
    Last edited: Jun 17, 2022
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