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    Default Casting Engine Parts

    Hallo,ever since i started making JetTurbines i always used a lathe to make the parts,but i seen that some ppl are casting the parts,i dont know what is better.
    how did they made this part?

    sand casting or what?
    can some one point me to some links about casting like that,and how much does it going to cost me to start casting like them?
    Ofcruse ill use Inconel 713(btw does any one know wheres the best place to buy it?)
    thanks

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    If you mean at home, no, I think it can't be done. Inconel melts at about 1400°C. Many people cast aluminum (lots of info here ) which requires half the temperature. You could e.g. cast the diffuser. But then you would have to machine it to tolerances, so why not machine it from stock?



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    Hi there,

    Those turbine blades are investment cast. I went to a small factory where they make these engines a few years ago and saw all their equipment. I'm not too clued up on the correct naming, but the casting is done in a machine where the mold is spun around (centripetal force) in order to get the metal into all the little corners. The machine was quike nifty. You basically stick the (solid) metal in and the ceramic mold and it makes the wheel (well, almost...). I do know that you need to be careful of bubbles that can potentially weaken the wheel.

    I hope this helps.

    Warren

    Have a nice day...


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    It is called centrifugal (spelling?) casting. It is usally done on investment type castings. I have done it using lead and lead alloys. The molds are round with a center sprue hole with runners going out. Sort of like a wagon wheel. Building one is rather easy, I used a blower motor with a 6" pulley attached to the shaft. Mount the motor so the shaft sits vertical. The mold is sandwiched between a piece of plywood and the pulley, held in place with a series of staybolts around the perimeter. The plywood has a hole in the center that lines up with the center of the mold. The staybolts are just snugged down, this allows the air to escape out of the mold when pouring. Here is a secret that I had to find out the hard way. Mount the assembly in a cut off metal trash can or 55 gallon barrel with the top of the mold at least 12" below the top edge. It is amazing what flying molten metal can do to a pair of jeans when you mis the sprue hole much less to your skin, ouch doesn't even cover it.

    If it's not nailed down, it's mine.
    If I can pry it loose, it's not nailed down.


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    ok so your saying that i can do it at home right?
    do you have a pic from your cast dude?



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    oh just found some think,its goes pretty much like this doesnt it?
    http://www.watchrepairer.co.uk/How%2...0Jewellery.htm



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    I hate to be negative but 2muchstuff said he did it with lead (melting point 328°C). The link you posted was the lost wax method, not centrifugal, and the cast was in silver (melting point 960°C).

    I just can't see how you will be able to melt Inconel at home.



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    ok lets leave the melting part away for a sec.
    in centrifugal casting the muld spins to get the metal to all the parts of the muld right?
    so basickly if ill get some think that can spin it around it will work right?



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    some think like this?

    Attached Thumbnails Attached Thumbnails Casting Engine Parts-wbitcfdshsds-jpg  


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    The nickel based super alloys need to be melted under a controlled environment (Vaccuum?).

    Regards,
    Mark


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    Okay but im not talking about the alloy now
    i just want to know how the centrifugal Machine works.



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    Quote Originally Posted by RotarySMP
    The nickel based super alloys need to be melted under a controlled environment (Vaccuum?).
    why do you think superalloys need to be vacum melted?



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    I think I am confusing this with Titanium? Triple melt in a vaccuum is a requirement for commercial aero Ti disks (compressor). The Super alloy commercial turbine disks are forged.

    Regards,
    Mark


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    Centrifugal casting using centripetal force....so our UK buddy is correct. Basically you melt the metal in some type of melting furnace/crucible. The mold which is either made via the "lost wax process", or "lost foam process" or machined is placed in an item that looks like a centrifuge after it is heated or in some machines I suspect that you can heat it in place (though this would be high buck systems).

    The molten metal is poured into a resevoir in the mold and the centrifuge is turned on and the centripetal force forces the molten metal into the mold.



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    Sorry but I don't have any pictures of my set up. I did this about 10 years ago and since then I have gone on to other methods and materials for my casting. The motor spun 1725 rpm, any faster than this is not needed and is asking for injury if you miss the sprue hole. Your picture shows your sprue hole off center of the motors axis, it must be centered to the axis of rotation. Basically what I did was start the motor spinning along with the mold. Then comes the fun part, pour the molten metal down the spinning sprue hole. You can stop pouring when you see the metal coming up the sprue. By the time you put down the pot and come back you can turn off the motor. Let cool a few minutes and remove the mold and crack open. There is a learning curve regarding the amount of pressure exerted by the hold down screws. Too much pressure and the air won't escape, not enough pressure and metal will escape at the parting line. If you are going to cast something round like the compressor/ blade assembly shown in you first post here, you will want to make your mold in a way such that the center is at the base of the sprue. Otherwise things can get unbalanced and the density of metal will be greater on one side than the other.

    If it's not nailed down, it's mine.
    If I can pry it loose, it's not nailed down.


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    thanks,i need to make a wax model cover it with some kinde of ceramic dressing cover it with fine sand up to 8times and them melt the wax out, put it in the bin that spins in 6000RPM(is the speed right?), and let it spin for (how long?)
    am I right?



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    dude...lol it sounds quite complicated. Good luck with making a perfect mold first.


    I tried making a prop for an r/c boat and every casting come out looking rough and requires major cleaning up/machining. And thats only 2-4 blades.

    lol would be awesome if u can make one. Otherwise, I'd say just save up and buy a professionally made one to save ALL the trouble... really!

    Live life like you never see another day


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    You could possibly do this at home...but only if your pocket is full of 100$ bills and is never ending...its cheaper,safer and just smarter to have work like this hired out to investment casting companies. I have built a furnace, forced air running on 3 propane burners of my own design with a square fireing chamber and fed with O2 bottles and I can get tungsten red hot but it wont melt and it gets oxidized very easily. You would have to do something like that in a vaccumed arc furnace with a crystal crucible (1000$+ USD just for that) You could build and arc furnace but that takes VERY high amps and then to create a decent vaccume on it would be just another pain in the backside that would take alot of backyard enginuity. I'm not saying you can't do it because you can. I'm just saying its going to be expensive and its going to be a long time before you make anything that is "good".



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    I have melted inconel 718 with out a problem. When discussing home methods of doing exotic things like this, it is helpful to remember the methods used by experimental laboratories a while back to achieve such feats. The methods were cheap, efficient, and effective.

    First a little back ground on the alloy inconel 718. It is the alloy most common in use for high creep strength applications such as turbines. It does this by virtue of some additives to the steel. It is based on nickel and iron, but despite the high creep strength at high temperatures it still has a reasonable melting point of 2300F (1260C), this is easily achievable with a home made reverberatory furnace. To put this in perspective cast steel alloy has a pouring temperature of 2822F (1560C) according to http://www.a-m.de/englisch/lexikon/giesstemperatur.htm. Carbon steel such as A36 melts at about 2600F. As you can gather, the heat is not so much of an issue.

    Now to construct a furnace that can be used to melt inconel or steel or other similar metals I would prefer a furnace that is much like a reverbaratory furnace. For small quantities of metal one can gather a firebrick like that used by foundries, and can withstand 3000F. The firebrick is relatively soft and can be carved by a sharp piece of metal. Carve a depression in the firebrick that looks something like a spoon. The cavity should be big enough to hold the desired metal and the carved spout should allow the metal to flow out when the brick is tipped, this will also serve as the exaust of the furnace. Carve a hole in another brick that will extend to the melting depression in the first brick carved. This hole should be big enough to allow the flame of an oxy-acetylene rosebud torch flame to penetrate.

    To operate the furnace you would gather the pieces to be melted into the melting depression. Place the lid brick with the torch hole on the ladle brick. Strike up the touch and hold it over the torch hole. The metal will quickly melt. To reduce the action of oxidation, adjust the torch to have a slightly reducing flame. Since it is hard to describe this flame you will have to look for it on the internet. When the metal melts simply use common sense and a safe mindset to tip the brick and allow the metal to pour into the mold.

    A larger reverberatory furnace can be constructed by using a castable refractory available from Budget casting supply called Versiflow 60 pro (3100F). It costs about $100 for a 55 lbs bag. For anyone who does hobby casting this is a good source for stuff. Anyway keeping with the same principle of the before mentioned furnace can scale the reverberatory furnace to about any size they want.

    On a note: if one cannot find fire brick you can make a refractory your self by mixing silica sand with fireclay. A successful mix for me was about 4 parts sand to 1 part clay. It should fire to a refractory that can handle moderate abuse. This is the cheap way but the results may vary. Buy the mix for less headache.

    cheers!



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    If you are not making parts for a millitary or comercial turbine, You can make them at home without any problem.

    I cant go into all the details but Ill scetch it out here.

    Many years ago I worked at a small prototype shop that made turbine parts for companys that dont exist anymore. We had to make everything ourselves and invented many of the processes that are used today.

    All you need is a 300 amp welder, some carbon electrodes. Some castable refractory, a vacuum pump and a ceramic mold for the part.

    You make a crucible from a piece of pipe by welding a plate on the bottom. Then you drill some holes in the crucible and drive some pins thru the pipe at the bottom that will act as a conductor and are long enough to penetrate the refractory. You also need a hole that is about an inch in diameter in the bottom of the crucible and refractory. This is your outlet for the melted metal. Then line the inside of the crucible with castable 3200F castable refractory. Sinter the refractory. Attach a conductor to the crucible then wrap the crucible with a few inches of 8 lb ceramic fiber insulation.

    Make a top from more castable refractory and sinter it. You will need a hole in it for the electrode to penetrate and a home for a vacuum pump connection. The vacuum pump connection will need to be cooled and the eaisiest way is to attach a 50 ft piece of coiled copper tubing to it and drop that in a barrel of water. Other wise your pump will catch fire. Dont ask me how I know......

    Now you have a vacuum arc furnace.

    You will attach the electrodes to the welder and insert them into the crucible. You can either make a lever system for lowering them or a electronis stepper system that is amp related. we used a lever and amp gage and a young guy to watch the amp guage and lower the electrode as the metal melted and the carbon burned away. You can also use tungstun electtrodes if you can hold a good vacuum.

    Any foundry supply shop has little disks that you can put in the bottom of pouring basins that you puncture after you fill the basin. I forgot what these are called. Put ont of these in the bottom of the crucible with some refractory cement.

    Fill the crucible with metal. Put the top on and start the vacuum pump. Wait a few minutes and then turn on the welder and strike an arc. Keep the arc maintained and the welder at maximum and you will soon melt a quart of Inconell or hastaloy in about half an hour or so.As the electrodes wear down pull them out an insert another one.

    Before you start melting your crucible will be centered on the sprue of the ceramic mold of your part and sealed with some refractory cement. When the metal gets close to temp, turn on the vacuum pump for the mold. When the mold and metal are hot enough, pull out the electrode and insert a sharpened stainless steel rod and puncture the disk at the bottom. All the metal will be drawn out of the crucible and into the mold.



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