Ferrous Patterns

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Russ Hanscom
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Ferrous Patterns

Post by Russ Hanscom » Fri Feb 14, 2014 12:11 pm

Can anyone tell me whether lost foam or similar process are applicable to casting ductile iron or steel?

I need to reproduce some rocker bearings for an RPO swing bolster. The part of interest is 17" long and 4 1/2" wide and we need to make at least four. It seems equally easy to make a male or female model, via CNC, and if lost foam or something similar would work, it might be easier to mold than using the conventional method. The chalk line on the one part indicates the probable original parting line.

Just looking for options at the moment.

One photo includes the mating part, that is an easy one to pattern.
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steamin10
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Re: Ferrous Patterns

Post by steamin10 » Fri Feb 14, 2014 5:15 pm

You need to talk to the job boss at the foundry of your choice. Parts like what I see are often produced from free molding patterns. They are not on match plates. Being that one part seems to be broken in the curved flange area, it would have to be repaired with auto body filler or some such temporary shaping material. Shrink will be a small problem, but parts usually come out close enough to be usable. Any repairs should be marked with orange or red paint, so the apparent master is not manhandled and redamaged before it is cast. Not a problem if the handlers and molders are aware.

I have not done foam casting, and cannot advise you along that line. All I know is , dont use a finishing material on the outside of foam, like paint, plaster, tape, or some filler. The outside finish is the surface you will see and it must be fully open to be burned away by the metal. Otherwise anytape or repairs will make a carbunkle on the surface of the casting.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
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RONALD
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Re: Ferrous Patterns

Post by RONALD » Sat Feb 15, 2014 8:58 am

I did some ductile iron casting awhile ago, and decided it was not worth my time, and switched to C99700 White Tombasil high strength yellow brass for my castings.

I did two Delta Trailing Trucks in lost foam and the first one failed because I had no way to measure pouring temperature.

I, of course, had to first make up the patterns, which is a project by itself: First photo.

I had use of a rotary arc furnace for melting iron, but the only way to determine pouring temp was weight of iron verses a watt-hour meter. I had gone to Wells Mfg., where the metallurgists gave me the nodules and told me how to mix them in the molten iron. Everything went according to plan, but we poured at too cold a temperature, the results shown in photo 2.

I tried a second with better results: Photo 3. I tried once more and then decided it was not worth the time for me to pour iron.

I did do more iron castings, but I poured them at one of two local foundries. I brought my flasks ready to pour to the foundry.

Yes, Lost Foam does work with iron.

Note: the first photo is not of that first set, it's of the second set which I poured in brass.
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steamin10
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Re: Ferrous Patterns

Post by steamin10 » Sat Feb 15, 2014 3:19 pm

I see the cold runs that are so promenant with thin bodied castings in iron along with cold shuts.

Fro my part I limit my casting to nonferrous, Al and Brass/bronze, being tough enough. Otherwise any iron will be worked out at a foundry willing to deal with a knowledgeable hobbiest/ Ameteur.

A crucible furnace as I have will just about destroy itself getting to iron temperatures. The thermocouple I have for nonferrous is useless in iron, and will be eaten. So for me it is just an undoable deal. Know when to say Uncle and let a pro do it.

The pics say it all , thanks.
Big Dave, former Millwright, Electrician, Environmental conditioning, and back yard Fixxit guy. Now retired, persuing boats, trains, and broken relics.
We have enough youth, how about a fountain of Smart. My computer beat me at chess, but not kickboxing
It is not getting caught in the rain, its learning to dance in it. People saying good morning, should have to prove it.

Russ Hanscom
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Joined: Wed Mar 15, 2006 11:10 pm
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Re: Ferrous Patterns

Post by Russ Hanscom » Sat Feb 15, 2014 5:48 pm

Ronald,

Nice results after you got it dialed in. The surface finish looks good. Several questions; first, I am assuming you had a mold and shot it full of foam? If so, what kind of foam?

Russ

RONALD
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Re: Ferrous Patterns

Post by RONALD » Sat Feb 15, 2014 9:32 pm

No, that's all made out of flat Styrofoam. It's just like making a wooden pattern, only you use foam. Of course, unlike wood, the pattern is destroyed by the molten metal. You can lose many hours of work when you have something go wrong like a cold shut.

Yes, that experiment was the only time I tried pouring iron by myself, I would not attempt to pour iron with the equipment I have now.

If you browse back thru this section of the Home Machinist, you will find a lot of good information on casting in Lost Foam, or EPS as it was first called.

If you have the November 1984 copy of Live Steam there is an article on the subject, or if you send me your email address by PM I will see if I can send you a copy.

Russ Hanscom
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Re: Ferrous Patterns

Post by Russ Hanscom » Sun Feb 16, 2014 5:17 pm

Thanks, I will call the foundry tomorrow and get their comments.

dolfa
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Re: Ferrous Patterns

Post by dolfa » Fri Feb 21, 2014 8:06 pm

The best would be to make a wood pattern, split it in the middle as in the photo#2, core the inside, mount 2 patterns on plywood boards with 2 self moulding locators and pour it through a riser in the middle between the 2 patterns with ingates through the cores and vents over each end. Ductile iron is easy to cast in the foundry, for steel you would need a sprue, runner and 2 risers on each pattern.
Dolfa

Russ Hanscom
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Re: Ferrous Patterns

Post by Russ Hanscom » Sun Mar 02, 2014 1:33 pm

The foundry we are working with does not do lost foam so it is on to a pattern.

At first the curved ends seemed a challenge until I had an aha moment and they became the easy part. Make a donut of the correct profile and cut out segments and glue to the straight pieces. I used a bit of 1/4" thick O-1 plate for the profiles and did not bother to harden them for the few pieces that will be needed. The test piece was made of layers of particle board, it has a few errors but the concept works.

The part has three arcs, each of the cutters has one and a half since that was the size of the available plate. The arcs were done on a rotary table and relief was ground on the back

Now to glue up a couple of proper blanks.
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Russ Hanscom
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Re: Ferrous Patterns

Post by Russ Hanscom » Thu Apr 24, 2014 8:36 am

Well, a bit closer. The two patterns are roughed out in wood, just a lot of finishing remains. The larger part has a two part pattern for mounting on a board; it will also require three cores or one very complex one.

The smaller part is mounted on a work board; it makes the pattern a lot easier to handle and I do not have to get the fingers quite as close to the router bits and other sharp cutters.

One of the other fellow is working with the foundry and he will make the core boxes and mount everything to the match plate.
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