Incomplete casting pour

Discussion in 'Castings, finishing/ repair/ and patina's' started by John Homer, Jun 12, 2021.

  1. John Homer

    John Homer Silver

    Been trying to figure out a match plate pour with bronze. Have tried a couple different setups with no luck. Any ideas or recommended techniques to correct the problem?
    I know one issue was I poured directly into the parts but why didn't it fill the mold?
    Any help is appreciated.

    Thx
     

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  2. HT1

    HT1 Gold Banner Member

    your metal is cold !!!
    it's that simple,
    it appears you are pouring directly into the piece, which is a terrible technique with a drossing alloy like bronze ( I'm assuming tin bronze) but it does give you the best opportunity to fill a thin part

    dont know why you are not using the gating system you created, though it has issues ( leave this dog lie for now)

    pouring technique: looking at your pouring cups, they are too small, so you are probably "dribbling" metal into the cup you need to open up those cups and run them deeper, so you can "hit it hard" get the metal into the mold faster one solid shot

    how thick is your piece??? it looks like you are up against minimum thickness for Bronze on that piece 3/32 in
    if that is the case you have three options :

    1) redesign
    2) change alloys if you are already running a known silicon bronze that is about the best you can do and maintain strength, yellow brasses will pour thinner, but loose alot of strength in comparison
    3) Use a thicker cope, or a separate pouring cut to increase the head pressure

    now a couple of notes on your matchplate , I would have placed the pouring well in the middle of the runner, to get hot metal to all the castings at the same time ( be forewarned it can be hard to hit a sprue in the center of a mold ) i would have placed the parts as close as possible to the runner . for bronze your matchplate looks fine for cast iron, but cast iron is very liquidy


    V/r HT1
     
    John Homer likes this.
  3. John Homer

    John Homer Silver

    I appreciate your feedback. I am using silicon bronze the thinnest part of the piece is comes down to about 1/16 of an inch these parts were made over 150 years ago so I figure there's got to be a way to do it....if I could only go back in time to watch the old timers. I'm trying to do it with a match plate so I can Mass produce these rather than doing one or two pieces at a time.
    I did run a part using the runner but my gating wasn't working properly I've thought about running the gate to the thinnest part of the the piece on both sides to see if that would work but this would cause a lot more clean up at the end.... which I may have to end up doing.
    I also have thought about putting vents at the end of each piece on both sides to see if that would assist in cutting down pressure so the metal would flow better but not sure if this would work. May try that also. Like I said appreciate your feedback I will definitely take your advice into consideration on my next poor thanks again.
     
  4. HT1

    HT1 Gold Banner Member


    ok at 1/16 thick, you gotta increase your head pressure and pour hard, remember in the professional foundry (sand casting) up until the perfection of a no bake sands, 4 inch thick copes where considered minimum , and 6 was very common, watch some of the old videos, you will see guys flipping 12X12 6 inch cope and drag , Molders used to be beasts!!! venting is a good idea, but do it correctly, a vent that fills with metal is NOT a vent a sharpened wire poked down to the pattern , just kissing it is fine for petrobond , better yet, measure, and stop 1/4 inch sort,
    you can also run lines from the mold cavity to the edge of the flasks at the parting line ... this technique you can put directly on the matchplate so you don't forget, but remember the vents do not actually contact the pattern, vents that fill with metal are not vents

    V/r HT1
     
    John Homer likes this.
  5. John Homer

    John Homer Silver

    Thanks. So if I run fence like you said from the part to the edge of the match plate at The parting line you're saying not to touch the part itself stay back 1/8 of an inch or something correct?
     
  6. John Homer

    John Homer Silver

     

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  7. HT1

    HT1 Gold Banner Member

    im note sure I'm making myself clear, I have never said Fence , to vent, you should just scratch line in the rammed mold , with a scribe or the tip of a pencil from just short of the mold cavity to the edge of the flask, this gives the gas a path of least resistance out of the mold, the sand is permeable, it will allow gas to escape, vents are for excessive gas, which is seldom an issue in petrobond,

    i would gate into the sides of the straps , one gate on each side of the center, near, but not at the end, that will present no clean up issues, you may have a shrinkage issue in the center, the original pieces where probably cast with a core to create the hole and the eliminate the shrinkage in that area,

    if the pattern where closer to the runner, heat from the runner would help with the filling , hot sand fills better then cold sand

    lastly, the bottom of splash wells should be flat the rounded cylinder you have will create tons of agitation, though as long as the runner is I think you are OK

    V/r HT1
     
    John Homer likes this.
  8. John Homer

    John Homer Silver

  9. Jason

    Jason Gold

    John, you say the original was just 1/16" of an inch thick and it's 150 years old??? Are you 100% positive it was really cast originally? Now I may be very wrong, but bronze is so soft that for the right craftsman, adding that level of detail would be childs play. If you still have trouble casting it after making changes, just add thickness to the back. Machine it off when you are finished. Even with ceramic shell, I've only been able to reliably cast sil bronze down to an 1/8" for any length of distance.. I'm not saying it can't be done, but 1/16" is REALLY THIN!

    I hope you pull it off. Pouring right at 2100 with some good head pressure is what it's gonna take. Keep in mind if you get much hotter than that, you'll have pink whatever those things are and the finish will be trash. What are they anyways? Looks like some kind of decorative strap for a box or trunk.
     
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  10. John Homer

    John Homer Silver

    I hear you. They were definitely cast. I have an old advertisement thats dated in the 1800s that shows these and lists prices. They are oar locks for a Adirondack Guideboat ( Rowing boat) I am trying to cast these to sell. See pictures of the boats. These were being built in the 1840s
     

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  11. HT1

    HT1 Gold Banner Member


    I would expect 100 year old oar locks to be brass , not bronze , and Silicon bronze is defiantly wrong, silicon bronze was introduced in the 20th century


    V/r HT1
     
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  12. John Homer

    John Homer Silver

    The older ones are very flimsy. Makes sense thanks
     
  13. FishbonzWV

    FishbonzWV Silver Banner Member

    John, I can't help with your casting but...
    I went to a strangers house today to buy an item he had for sale.
    He opened the garage door and much to my surprise, there was a drift boat he was building. It was close to being finished.
    I laughed and told him I had just seen yours today. We had a lengthy discussion.
    What's the odds of seeing two drift boats under construction in one day? :) o_O
     
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  14. John Homer

    John Homer Silver

    Wow cool.
    Iam building Guideboats but the are somewhat similiar
     
  15. FishbonzWV

    FishbonzWV Silver Banner Member

    Oops, I might have insulted you by calling it a drifter.
    Yes, yours is more refined than his with the hard chine.
    His oarlocks were sandwiched between the inside gunwale and an outer gunwale/rub rail. Interesting build.
    Yours is Bee-You-T-Full !!!
     
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  16. John Homer

    John Homer Silver

    No worries. Thanks for sharing your journey
     
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  17. John Homer

    John Homer Silver

    Some success today. I think I just need to move my pour spout to the center and will have this in the bag.
     

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    HT1 likes this.
  18. John Homer

    John Homer Silver

    I moved the sprue to the center but have a couple more issues. Any ideas why the parts didn't fill? I know it definitely needs a larger sprue to push more metal.
     

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  19. HT1

    HT1 Gold Banner Member

    you need to step the runner so the metal fills all parts of the casting at the same time /pressure

    basically as the runner passes each ingate, it's size should decrease by the amount of metal the previous ingate took out of the runner

    Page 10 and 11, just a general good read also
    https://sites.psu.edu/shapelab/files/2017/02/Trad_Casting_Rules_Santosh-2kkxcb8.pdf


    V/r HT1

    P.S. it looks like your ingate contact area to the casting MAYBE choked which is really really bad, it causes pressurization, and metal spray
     
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  20. John Homer

    John Homer Silver

    Appreciate the feed back. Will take all into consideration for sure. Darn frustrating trying to get this one figured out.
    Any recommendations to fixing the ingate contact area you mentioned? Should I taper that area more?

    Thanks again
     

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