Starting In Lost Wax/ Investment Casting

[RONALD]

I started into investment casting in the early 1980's when there was no Internet around with instant knowledge. Luckily, I was already into making larger castings in the school foundry, so the learning curve was not too steep. Also, at the same time I was getting into Investment Casting, Mike one of the schools metal casting instructors was doing the same thing.

In 1984, I drove down to St Louis to pick up an order of casting equipment and supplies from Fred Ellis of Power Models. Fred gave me the best price. At that time, he was operating Power Models out of the basement of his home, he later, as you may be aware was killed in a fire at the building he had moved Power Model to and had other things in that building.

I bought a Kerr Furnace, Vacuum Set, Waxing Pen Set, Injector, Maxi Electro-Melt, and a lot of different waxes, so I spent close to $3K with Fred, but it was a better price than I could get from anybody else because Kerr controlled it's prices at that time.

I later bought a Whip Mix Combination Unit for mixing investment under vacuum from the Whip Mix Corp, and the final major item was a Steam Dewaxer, because my wife was always complaining about the smell of burning wax thruout the house.

You might not want to get started at such a cost, so what would be an easier route, the answer is Art Classes. My local Junior College, called Harper Jr. Col. has offered bronze sculpture casting for artists in their evening classes at various times. It was a great course when I took it, but I took it because they were doing Shell Investment Casting, a slightly different approach. See what your local Junior College has in their Art Department.

Today, there is almost too much information available, on the subject, but a good place to start is with the Rio Grande Co. They can send you a catalog, have all kinds of DVD's on the subject, and will sell you things at their prices. That is one of the advantages we have today, we can search the Internet for the best price, something I could not do in 1984.

http://www.riogrande.com/Category/Tools ... plies/5864

[FLtenwheeler]

Hi Ron

Is it worth purchasing smaller flasks for small items? Or is it better to use a large flask that will accommodate a tree that will take a full charge of the crucible?

The wax has me total confused. There are so many different types.

Do you use Rapid Prototyped parts for your masters? If so what shrink do you plan for? What silicon rubber would you recommend?

I would also like to know about pinned molds for putting small through holes in the casting.

I am planning on building a CNW H16-66 Phase 1 as well as the CNW Group 5 J-Class Mikado. This group has the early style Coles Trailing Truck and Young Valve Gear. My Son is drawing all of the parts that will need to be Rapid Prototyped.

Sorry for all of the questions, it might be more than you bargained for when you started this thread.

Thanks

Tim

[RONALD]

Before you worry about flask size, you should decide on what materials and procedures you will use.

1. You need an Investment: I use Ultra-Vest:
http://www.ransom-randolph.com/jewelry/ ... ments.html
There are lots of others, but I get the best results with Ultra-Vest. Try to find a local source, because shipping can be high. The mixture ratio I use is 41.2 grams of water to 100 grams of Ultra-Vest

2. How will you mix the investment: Investment is best mixed under vacuum, if you do it in air you can introduce lots of bubbles. I use, as I said above, a Whip-Mix unit:
http://whipmix.com/product/vacuum-power ... tion-unit/
There are lots of other mixers, but that is what I use. Because that mixer has a limited capacity, for some large flasks, I have to mix more than one batch; bigger mixers are too expensive.

3. Flask etc.: Flasks come in all sizes as can be seen on:
http://www.ebay.com/sch/i.html?_trkparm ... p=10&_sc=1
Those are only perforated flasks, I have made unperforarted flasksout of steel auto drive tubes that work fine, as seen in that previous photo. The reason you use perforated tube is if you are using vacuum casting, if you build yourself a large centripetal casting machine as Harold suggests you would not use perforated flasks. You want to keep your pattern from touching the side of the flask, so at a minimum I would keep the pattern 1/8" away from the sides; that will determine the diameter of your flask.

4. You need a sprue base to mount your pattern, anything that will burn out can be used as a pattern, whether RP,or hand made.

5. You need a Burn Out Furnace: If I were to buy a newer model, I would buy one with automatic sequence timing, because my Kerr 999 must be manually adjusted for temperature.

6. Pouring: With small parts you really only have two choices vacuum or centripetal. I use vacuum, Harold wants you to use centripetal.
In either case you must get the molten metal into the flask ASAP! The pouring of metal whether several tons, or a gold tooth, can be dangerous wear protective clothing, gloves, and above all EYE Protection.

7. After a few minutes plunge the flask into cold water, and most of the investment will dissolve, and you have your locomotive part!

In a previous post I recommended what you should use for rubber.

[Harold_V]

Harold wants you to use centripetal.

Not necessarily. A great deal depends on the size of flask you are capable of pouring. You are restricted with the Romanoff machine, and much more so on the small manual machines commonly used in the jewelry industry.

I also have a vacuum casting setup----although all of my equipment remains unused at this point (and is still in storage). I'm just throwing out alternatives, and relating experiences I have had in the more than 20 years of experience I had as a precious metal refiner. I served the jewelry industry, where investment casting is routine.

One of my customers had me build a vacuum assist for his centrifugal casting machine. The best of both worlds.

Harold

[FLtenwheeler]

Hi RONALD

Thank you for your reply. It is a great starting point.

Tim Meyer

[RONALD]

Some more comments:

The bigger the flask, the more investment required. Unlike sand casting, you do not get to reuse it, so for $$ reasons it is best to use the minimum size flask that will do the job.

Most of my wax is Injection Wax that is to be used in a Wax Injector, for filling a rubber, wood, water putty, metal, or plaster molds (I have used all those materials to make injection molds.) I do have carving wax, and little wax rods etc., but I seldom use them.

If you know the metal you will be casting, then you should apply the proper shrink to your pattern, and also allowances for machining. I have dreamed of doing RP for a looong time, but as of now my original patterns are wax, styrofoam, wood, or metal which I form into the desired shape.

Harold has had more experience in the business end of investment casting, and I only know what has worked best for me. There is another site that you might go to for even more opinions, and some real "crackpot" proposals.

http://www.alloyavenue.com/vb/forum.php

or

http://groups.yahoo.com/group/hobbicast/

PS, I'm usually outside working this time of the year, but this year there is still too much snow, mud, and cold to work outside, so instead, I sit here and write about casting. We are expecting more snow tomorrow!

[FLtenwheeler]

I am thinking about using Silicon Bronze but am open to recommendations. Bronze is 1-1/2% shrink, but I have been told that some molding rubber shrink as well. Does the wax shrink any?

Tim

[RONALD]

Tim, as you can see below your average Silicon Bronze shrinks 3/16 of an inch per foot, while the C99700 shrinks 1/4 inch. For the parts you show in the photo, which are way less than 1 foot in length it amounts to only a few thousands at the most, and for non-critical dimensions, may not be noticed. Even the professionals at times have to "go back to the drawing board", so you may have to re-do a part if it is too small.

When I make a pattern, like that for a switch frog, because I'm casting C99700 I allow that 1/4 inch shrink, but for real small stuff I just add a smidgin.

The injection wax I use has little shrink, and the RTV, and other molding materials I use I don't worry about, there is nothing I could do short of making a metal mold, that would prevent miniscule shrinkage, or expansion. If you are doing Shell Molding, which is a different form of investment casting, you have to worry about the wax expanding when heated, and cracking the shell just like an egg.

I use the C99700 White Tombasil, because it is easy to cast, easy to machine, and has a sort of gray/silver look when weathered. Of course, all metal today is expensive, when I bought 500 pounds of C99700 in 2011, it cost me $5 per pound, and that was by driving my pickup to Kramer Co.

[FLtenwheeler]

Hi

What will most likely determine the alloy I use will be the ability to purchase one ingot at a time. Budget Casting Supply sells C87300 Everdur.

Again thank you for your input.

Tim

[steamin10]

My experience with Everdure is very positive. I casts and flows well, giving exceptional detail.

I do not know how it reacts to steam related corrosion, due to the Zinc content, as you would have in a steam pump body. I just dont know what everybody else uses for such items as a Westinghouse pump or similar in model sizes, although the cast may be much more detailed . The same question I would ask about cylinder cock bodies, snifters, and water guage parts.

As detailed mechanical parts, I have no qualms whatever in the model field, and hold this alloy as top rate.

[Harold_V]

My experience with Everdure is very positive. I casts and flows well, giving exceptional detail.
I do not know how it reacts to steam related corrosion, due to the Zinc content,

Unless I have bad information, there is no zinc (or lead or tin) in silicon bronze. It should be made up of 3.25-4.5% silicon, up to 1.5% manganese, with the balance being copper.

Harold

[steamin10]

Not so,Mon Amie! Look at the common trade name everdure, and see the zinc component. I was (for a reason I cannot state) was unaware....
That is not what the tables show, as much as 12 % Zn, which can be the problem. Everdure is (9%) but casts well, for detail. I just never knew the formulae, Just that it was very forgiving of nature. Love the stuff, but the question still stands. How is it in life around the corrosive qualities of steam. (I dont have a clue, in practice)... Brass is problematic, not unusable, but demands some watching. So how would Everdure be better in the real trials of steam?

Remember the zinc is the weak link in brass fittings for boilers, and that includes the Everdure, that is so good for details.

This is part of the problem of learning by doing. Somebody suggests the best ever(dure), and you find it is not the best for all purposes. (The reason they have all those other alloys). Bronze is the most prefered (gunmetal AKA phos-bronze etc. which still has aome zinc in various alloys, just look at the charts.).

I am a scrapper, and use something below $7 a pound material for most parts. But if I want the very best, you have to pay attention to what you get, and I am finding Everdure may not be the best for all my applications. ( JEEZE! the smarter I go , the dumber I get!).

I humbly submit, with due experience, I Dunno. !

Brain fart--It is 5%. look at the chart! I was in the mind set that ALL of the most common casting metals used by home guys have a zinc element, many very high. Yellow brasses range up 25% or better, and may be the key point for steam use. Again, I Dunno.