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Centrifugal casting splashing

Thanks for the welcome.
Can somebody help with this problem please. My spring driven casting machine is splashing.
I am casting medallions (220g 7.7oz) in silicone bronze .i only wind 11/2 winds as they are largish casts. Also a big sprue leading into the cast. Every time I let it go it splashes on the left side of the flask. The spin is anticlockwise so the splash is on the left side of the flask .
Prior to cast I set the balance correct. Also the crucible lines up centrally . Any advice greatly appreciated

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Is it splashing out from the crucible or between crucible and flask? When I’ve had this happen, it was because the arms on the casting machine were slightly torqued and the sprue opening wasn’t truly lined up with the hole in the crucible. Metal was hitting the wall of the button forming area and slinging back out. The cradle for the flask can be distorted as well. Make sure the hole in the crucible isn’t blocked by excess flux glass too. If that’s not heated and melted out, the metal can’t leave the crucible in a straight line.

Ruthanne

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The only time i’ve ever had a catastrophic flask cast was when I had the flask arm on the opposite side of its L position. And I have an extra 24" tall containment extension that caught everything. Let’s say, THAT never happened again.

Eileen

Is that all the closer the crucible will slide toward the ring?

Does your machine have a broken arm?

Apologies for length of time in reply and thanks for information and taking the trouble to help with my issue.
I solved it by increasing the size of the sprue leading in and by increasing the header size by taking a wax from a larger rubber base and welding that in place before attaching medallion on.I didn’t want to use where the wax was taken due to unnecessary amount of material due to larger flask size.I believe the main sprue that I welded the medallions on was far to thin.it was the same size as from the wax injector. A very basic mistake to make. Cheers ,and and now my only other problem is my dewaxing kiln is ramping up to fast . Got an electrician sorting it today. Happy casting

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Hope I get this right, I’m uploading an example of the medallions I am making. They are 250 grams (8.8ozs) and are at the top size I have been putting through the centrifuge and too swallow to put through a normal gravity ceramic shell cast(upload://nXXWeBb29Rxp2Kh8BlWifhaY5oX.jpeg)

![image|240x320](upload://nXXWeBb29Rxp2Kh8BlWifhaY5oX.jpeg)

Hi I’m back …and back with problems. I’m on another run of 10 medallions- 318grams (11 ozs) each, and I am coming in on the medal edge wide entry (see pic) so no problems now with spillage . But after casting 4 I get one side clean and green and the other side somewhere on the surface a miscast. (pic). It has happened 4 times running now!!. I only need 10!
What I"m thinking … At present …I wind my spring loaded centrifuge one and a half turns . Maybe I should wind it 2 and half turns ? Throw the metal in harder even if it is a heavy cast. Then again the medals are domed and maybe too thick through the middle and its retraction? I just don’t know . Any suggestions.? My dewaxing the flasks are 10hrs and early stages very slow .Also dropping down to 482 centigrade (899 Fahrenheit) casting temp. .I am using Silicone Bronze.
I don’t have a way of checking my melt temperature - never bothered before just made sure the slag was skimmed off before spin.
Apologies this all seems long winded and rambling it’s just I’m Thinking I should have stuck with Kayak fishing

You might making a sacrificial element that gets cast and that extends past the medallion. The metal will flow past your design and slide the contraction of metal from the middle. It’s probably at the limit of what your centrifuge will do already. Think of adding something that will take the extra metal you need and pull it back INTO your piece as it cools. Maybe a smaller main sprue or doing to two. An extra crank of the spring. I always do 3. Sometimes you have to fool the casting to adjust the metal pulling from the thickest part (or somewhere inconvenient). It’s more cleanup but it might help.

Large, thin …and flat shapes are somewhat challenging.

Good luck.

Thanks for that Eileen. I cast again today and both were successful . I did a 3 wind otherwise everything the same as the failed casts

Yes I think I must be at the top end of of my centrifuge . Asking a lot of it.I should really cast them with the Ceramic Shell process .so as it cools and the metal contracts so feed into the thickest part . ?

11 ounces! How much does a complete medallion weigh? This size may need to cast 3x the final weight. 11 ounces is a lot for a centrifugal casting machine. Doing that?
If I read correctly the medallion is thicker in the center, sort of discus shaped? Your final soak temp might be low.
You could have these cast by a casting service; but that would raise the final cost.

Thanks David , I’m so aware that I’m sitting at the limit of my centrifuge. I should have just gone the ceramic shell way . Sounds reckless , but I’m too far in with deadlines delivery etc. I cast again yesterday and both medals successful.
The thickness through the middle causing retraction…? They wanted them domed and on hindsight I domed them too much. So I’ve put my production mould aside and instead am pouring waxes out of front and back moulds out of my first rubbers taken off the porcelain etched design . Means I assemble and tidy edge - more work, but reduce dome, drop weight. Also best of all my production mould loses a bit of detail with injection. Now taking out of original rubbers detail is wonderfully sharp.

Just rereading all this… above…? My wife will be pleased. She is tired of being used as a sounding board

If those are really 11 oz each, you probably don’t need to use the centrifuge, and its limited melting capacity is restricting the size of your sprue button, which is why you’re getting shrinkage problems that are softening your detail. I’d say try gravity-pouring them with a much larger pour-cup, and see if they don’t come out better.

The cast medallions weigh 9 ozs (259 g)

Yes thanks ,I should have done that . …next time the gravity pour for this size. The cast medals are 9 ozs

You need to end up with a large “button” on the cast sprue - works as a reservoir or you need to use a pressurized casting machine. IMHO having made 4 was luck.
Can you cast halves and join them after casting. What’s the dia?

The buttons are 82 grams (2.8 oz) and diameter 0.25 inch (6.35 mm) and yes I have put 2 halves together and they cast . I’ll tig them

Using a longer sprue that is a larger diameter than the coin will help with the metal shrinkage you are getting in the center. Without a sprue the casting and button will solidify at the same rate and pull metal from each other.

Keith