Graphite Spray Technique to Improve Cast Iron Surface Finish? How to?

Discussion in 'Sand Casting' started by Melterskelter, Mar 21, 2020.

  1. Melterskelter

    Melterskelter Gold Banner Member

    Are you using green sand? What is a Disa? I found a few explanations of it as an acronym, but none that seemed to make sense.

    What method did you use to depressurize your gating system?

    Denis
     
  2. rocco

    rocco Silver

  3. Billy Elmore

    Billy Elmore Silver

    There are a lot of methods to use...the least complicated would be to start with the existing gating system and then add as much ingate as possible to your ingate location edge. Sometimes increasing the length and going thinner on contact point is best as it spreads the heat and metal out more evenly. I see a lot of ratios thrown around. Honestly, I have tried them all with varying success. Just watch your temp and do not interrupt the pour if you go depressurized. Not knowing much about your setup I would caution against giving you an exact calculation but you could start with a 1:1:2 ratio and see if there is any difference in your finish. You may have to play around to find what works best for you but as the temp and velocity goes down the finish will get better.

    The Disamatic is a high pressure vertical molding machine. The fastest one we have right now produces on average around 550 molds an hour but is capable of going over 600. Our bigger slower machines can push out around 450 molds an hour. We usually have four castings on each of those plates so we are seeing around 1700 castings an hour off of the one machine. We have two big Disas at 450 m/p/h and one small one at 550 m/p/h running everyday 20 hours a day. We also have two older machines we use to run small orders and experiment with that are capable of running around 350 to 400 m/p/h.
     
  4. Billy Elmore

    Billy Elmore Silver

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  5. Billy Elmore

    Billy Elmore Silver

    We use synthetic silica sand....we are currently experimenting with AccuCast ID ceramic sand on the old small machines.
     
  6. Melterskelter

    Melterskelter Gold Banner Member

    Your world and my world are worlds apart. My more complicated molds made in green sand take 2.5 hours for a single castable impression.

    Denis
     
  7. Billy Elmore

    Billy Elmore Silver

    You are right....I complain about having to wait 45 minutes for our sample castings to come through our shakeout system.LOL I could not imagine how making a single mold could take 2.5 hours...We would have made around 4500 castings on one of our slow machines in that length of time. Are you guys gluing a bunch of cores in place or something?
     
  8. Billy Elmore

    Billy Elmore Silver

    I failed to mention in the first post, but we tested out a lot of things to try and improve on our casting finish but the thing that made the biggest difference is our grain size on our sand. We went smaller and it made a huge difference. We did have to adjust some gating systems and had to add some vents to the castings on some jobs after we made the change but it was well worth it. If you choose to use a smaller grain just watch out for less permeability in your sand. We are now able to pour at hotter temps with the smaller grain without getting rough castings.
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    This is a cope, drag, and cheek 300 pound mold with a fair bit of hand cutting in gates, runners, pouring basin, and risers. Just flipping the mold requires bolting cope, cheek, and drag together, raising with a lift, flipping and then unbolting. There are 18 loose pieces to meticulously remove after the primary pattern is pulled. I guess I must be kinda slow. But if I hurry, I make a bad move, damage the mold, and have start over. That is a huge bummer.

    Resin bound sand would simplify the process. And making this part in volume would justify a few changes that would shorten process time. Since I will be surprised if I cast more than 3 or so if this part, hand work is the most expedient approach for me.

    Denis

    Denis
     
  10. Billy Elmore

    Billy Elmore Silver

    Yeah...that is a complicated mold! We dont even set cores anymore and want to maintain a machine cycle time of under eight seconds. We used resin bond sand on some horizontal molds we had produced at Chattanooga Foundry and transported them here for us to pour with our base iron. They had pretty good finish but were still not as good as we get on the disa with synthetic silica sand....but we did not pour them immediately after making the molds and they sat for several hours before we poured them. We felt they would have had better finish had we poured them sooner.
     
  11. Sawyer massey

    Sawyer massey Silver

    Green sand sprayed with alcohol and graphite
    Way better then my normal finish lol
    No let's see how hard they are
    The small ears on the top are like glass usually have to drill them with carbide the rest is nice gray iron
    Todd
     

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  12. Melterskelter

    Melterskelter Gold Banner Member

    I had trouble with a 1/8" thick 2X3" grey iron box chilling as it was so thin. A little trip to my kiln and a warm up to 1750F with a slow cool down changed its attitude. It came out as nice soft iron.

    I also tried a while back spraying some powdered graphite in alcohol onto silicate cores---enough to turn them nearly black. I could not see that it did anything.

    Denis
     
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