Entry Level Casting.

Home enthusiasts discuss their Foundry & Casting work.

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wildun
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Location: Auckland, New Zealand.

Re: Entry Level Casting.

Post by wildun »

steamin10 wrote:As I know it, Shell molding is a wax process where the wax mandrel with the needed parts are in a tree, is dipped in a ciramic slurry, and then an air fluidized sand box to coat the slurry goop, and the dipping process is repeated as often as needed to build up a shell. This shell is then hung upside down in a burnout furnace, where the shell not only dries but bakes the ciramic hard, and dewaxes.
STEAMIN.
I do believe that we are talking about different things here and the possibility of there being a difference in terminology between different English speaking countries may account for us talking at cross purposes, (no offence). - You have done a very good description of lost wax investment casting.

What I am discussing is different, it needs to be sorted and I will endeavour to find something which will explain what I'm trying to describe, - and don't think for one minute that I think I know best, just a misunderstanding you understand! :?
The 'Blawknox' process does sound similar I must admit - what did they call that process?

These are just a couple of sites where it explains it the way I knew it. (American spelling too.)

jkimberln has got it right in his post on the subject, (to my way of thinking).

http://en.wikipedia.org/wiki/Shell_molding

http://www.youtube.com/watch?v=uGQbJchXySM


Cheers,
Will.
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Harold_V
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Re: Entry Level Casting.

Post by Harold_V »

wildun wrote: You have done a very good description of lost wax investment casting.
While the processes are similar, the one where the wax is dipped in fluid, then coated with sand, is not the typical investment casting known here in the US. The investment, here, if not there, is a slurry which is poured to a flask, with the wax contained within. After pouring, the flask is subjected to a vacuum environment, to remove any entrained air, eliminating the risk of surface irregularities in the final product. This system is that which is used by jewelers in casting jewelry, where fine detail is expected. There is no flask for shell molding, and investment, without a flask, isn't conceivable, at least to me.

The wax (for an investment casting) is supported on a sprue base, which is the bottom cover of the flask, and is removed after the investment has solidified. There is no sand involved in this process, unlike the shell mold that is created by dipping and coating.

The problem I'm having with the notion that a shell mold is created by tossing sand on a heated form is the one whereby, once completed, how does one end up with two uniform halves, and how are they assembled in proper orientation? Neither of those issues are a problem with a coated wax, which remains a single piece. At some point these two halves must be married, otherwise you have no mold. If the shell is made as one piece, the pattern can not be withdrawn. Something is not being reported. The process sounds to me more like a core making affair, not a mold, but I'm open to further instruction and explanation, so I might better understand how a casting is poured. Mean time, the only shell molding I've seen is the one I described, which is in lock step with the process described by Big Dave.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
wildun
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Re: Entry Level Casting.

Post by wildun »

Harold_V wrote: At some point these two halves must be married, otherwise you have no mold. If the shell is made as one piece, the pattern can not be withdrawn. Something is not being reported.
The process sounds to me more like a core making affair, not a mold, but I'm open to further instruction and explanation, so I might better understand how a casting is poured. Mean time, the only shell molding I've seen is the one I described, which is in lock step with the process described by Big Dave.

Harold
HAROLD.
Each side is actually baked on a seperate pattern, with registers to locate it on the other half.

Yes, it can be a 'coremaking' affair too.

I can not explain it any better than in the links I gave you.

Ask GM or any of your big manufacturers who use it every day and no doubt they will explain it further.

Meantime I just want to get back to learning about the oilsand/greensand moulding process in the home foundry environment! :)
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steamin10
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Re: Entry Level Casting.

Post by steamin10 »

Harold: following up on your definition and observance, (paralelling mine) The two coremold halves usually have what amount to a truncated cone and pocket for alignment, or what would appear as round bump and pocket, like a marble of inch size was used on the master, to produce alignment keys, half marble to half hole. This was common.

It just was not named shell mold, to my knowledge. The Wiki defination is off a bit too, sounding like a blind man trying to describe a swamp.

I will defer, and only say what my experience is, never having poured a shell mold, but many times a Coremold process, and hand rammed Green sand and Oilsand methods for aluminum, from match plate patterns.

I was developing the capability of lost wax, when the last money crunch arrested progress.
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.
wildun
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Re: Entry Level Casting.

Post by wildun »

steamin10 wrote: It just was not named shell mold, to my knowledge. The Wiki defination is off a bit too, sounding like a blind man trying to describe a swamp.
:lol: Liked the description of the Wiki! - yes they can be like that, but it was just the first (of many) descriptions of the process I came across.
Anyway, no doubt you guys will find out more on it somewhere - It's common practice these days.

Will.
RONALD
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Re: Entry Level Casting.

Post by RONALD »

I have a Dependable-Fordath Co. Shell molding machine sitting in the corner of my foundry taking up space. I foolishly dragged it home when I cleaned out one of the foundries at the high school where I taught physics.

Like all bureaucracies, the story of this machine goes way back. In the late 60's, the foundry teachers, four at that time, decided they would order a shell molding machine, and submitted a requisition. After years of paperwork and delays, the machine, finally arrives in 1986, at a cost of $15,900, but now it has to be installed.

By 1986, there were only two foundry teachers left, and the then principal thought it might be too smelly, and installation was delayed by that and the paperwork/permits needed to get it up and running, so the machine stood in one of the closed auto shops still on its original skid.

By 1990, one of the two foundry classrooms was closed, and the guy who ran it was out of a job (He had not prepared himself by getting a certificate in another subject.)

In 1996, I was given the go-ahead to clean out that foundry, so for $1500, I got everything. The Shell Molding machine was scheduled to be sold to a scrapper, and rather than see that happen, I paid $300, for the machine and about 3000 pounds of resin treated sand.

So ~ 28 years later that machine still sits, never having been lit off, but who knows, one day I may yet light it off (I got so far as connecting up the natural gas to it.)

Here is one of their machines in action, I think the company is now out of business. I should add that the company was in Oregon, not to far from Harold.

http://www.youtube.com/watch?v=GJLRE9CRu7A
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wildun
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Re: Entry Level Casting.

Post by wildun »

RONALD wrote:
In 1996, I was given the go-ahead to clean out that foundry, so for $1500, I got everything. The Shell Molding machine was scheduled to be sold to a scrapper, and rather than see that happen, I paid $300, for the machine and about 3000 pounds of resin treated sand.

So ~ 28 years later that machine still sits, never having been lit off, but who knows, one day I may yet light it off (I got so far as connecting up the natural gas to it.)


http://www.youtube.com/watch?v=GJLRE9CRu7A
RONALD,
Interesting story,
I hope you can get it going! it would be a pity to see it eventually going to scrap.
Maybe in your retirement years you could combine your teaching skills with new found (shell moulding) foundry skills and offer them to a group of enthusiasts who might be interested, maybe even rent it or sell it to someone in a small engineering shop.
Someone will be interested, that's for sure.
wildun
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Re: Entry Level Casting.

Post by wildun »

We have certainly got off the subject of 'entry level casting' using simple oilsand type moulding, but it's been very interesting nonetheless.

Probably most of what can be said about simple casting has been said and the rest is probably up to me to put it into practice (which I have been trying to do as time permits).

Thanks to all of you for your suggestions and help and of course, any more suggestions are welcome, but I'll need to get on with it, as I feel (for the first time) that time is starting to run out and there's so much to do, question is can I do it? :)

Cheers,
Will.
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steamin10
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Re: Entry Level Casting.

Post by steamin10 »

Henry Ford of the famous auto maker line, told a group of engeneers in his employ, "Whether you think you can, or cannot do it, you are right!"

It might be noted the only Shay that worked the River Rouge plant as a switcher, had a centered boiler, and a large concrete weight opposite the engine side, to balance the locomotive. It seems Mr. Ford did not want the boiler offset, as normal on a Shay and ordered it that way.
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.
jkimberln
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Re: Entry Level Casting.

Post by jkimberln »

wildun wrote:We have certainly got off the subject of 'entry level casting' using simple oilsand type moulding, but it's been very interesting nonetheless.

Probably most of what can be said about simple casting has been said and the rest is probably up to me to put it into practice (which I have been trying to do as time permits).
-------------
Well, I'm going to do my usual 'blob' casting tomorrow. It is supposed to be a very nice day so I can open my garage and occupy some of the floor right near the door. I have found that getting small pieces of brass or bronze can be very expensive in either time or in money. So when I need some small piece I just make a quick wooden pattern, varnish it, then ram it up in petrobond. The top is left open - no drag and cope here - and just pour into the open end. I have patterns, if you can call them that, in round, square, rectangle, hex, of several sizes and lengths. Then I can just machine what I need out of them.

Tomorrow I'm going to make four large blobs for a water pump that will go on my Shay loco plus a couple of top hat looking round things for bearings for a hay baler I'm building. When I do the machining, I'll save the chips as best I can for remelt.

This type of casting is probably about as simple as one can get.

JerryK
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steamin10
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Re: Entry Level Casting.

Post by steamin10 »

For the sake of clarity, and to tip my hat to the board, it is obvious to me there is another definition of 'shell molding' that I was not particularly aware of. Persuant to the steadfast denial about what I knew, I spent some time on U-tube and had a time deciphering many posts.

I have to acceed to the name being used for flat molded forms made in a heated press, going by the same name. This is somewhat of a bit of news to me, and have to recognize the new information. It is what it is, and I hope this board understands we are doing what is intended, sharing correct information.

So with that, I will try to atone for my limited vision, and remove my foot from my talking oriface. Thanks, for the information.
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.
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Harold_V
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Re: Entry Level Casting.

Post by Harold_V »

You are not alone in the new revelation. To be quite frank, I'm shocked that I had not been exposed to this casting procedure, as I've done my share of reading and investigating. I fully expect that it may be the result of not having been around a production facility, but what ever the reason, I feel I have learned something new, and am thankful for the information. It is also quite clear that it would most likely not lend itself well to the home foundry, much like the other shell molding process.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
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