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roberlt
12-31-2001, 04:08 PM
A friend of mine (a long time ago) described how,When in art school ,He made a styrofoam model,put clay around it, dissolved the styrofoam with laquer thinner and then poured aluminum in the clay shell to make a casting.
Is anyone familiar with this? what clay do I use? problems,suggestions,improvements,books to read about this?
Thanks,
Rob

willjordan
12-31-2001, 09:04 PM
When I was younger, all-knowing, and immortal, we did lost styrofoam casting without disolving the styrofoam with anything other that the molten aluminium.

We made some journal boxes for a small locomotive crane, building them up out of styrofoam, packing it with sand, then finishing the mold with more sand.

Lots of vents and gates, and stand upwind and outdoors.

It's amazing how many beer cans it takes to cast a journal box.



------------------
grace & peace
will

Thrud
01-01-2002, 12:51 AM
Rob

Saturn uses styrofoam forms for precision casting of their engine blocks (you can see the plastic's expanded bead pattern in the aluminum - real nice job). The procedure is the same for Investment Casting of Jewellery but on a larger scale. I believe the plastic is melted out in Saturn's case. Call them and ask them - show up in a Saturn - they like that...

Dave

roberlt
01-01-2002, 10:14 PM
Dave,
I understand Saturns blocks are done by the method Will describes.
I want to make a large (for me) casting. With sprues & risers I am looking at a little over 3 Qts. of aluminum.
I DON'T want to burn out the styrofoam due to the smoke involved (I have all ready been visited by the local community pollution control officer and don't want to see him again) Lost wax is out because I don't have a furnace big enough to fire the clay and melt the wax.
Thanks for the responses.
Rob

Thrud
01-02-2002, 02:39 AM
Rob,

I do not think they would just pour the aluminum in the mold with the styrofaom present this would cause voids and impurities in the casting from vaporization and breakdown of the plastic. They may disolve it out using water with a starch based foam (non-toxic biodegradable). Phone them and ask them - seriously.

I do not think the EPA would allow burning it out with molten metal.

Maybe you should consider a green sand casting instead - should get great results with a little extra work. If you are going to recycle aluminum an intake manifold is a better alloy to cast with - if you can score enough metal.

If you do try it I would like to know how it turns out for you. Good luck - be safe.

Dave

roethej
01-02-2002, 03:33 AM
Lost foam is a pretty precise way to cast aluminum parts with pretty intricate shapes and thin cross-sections. Many Briggs & Stratton aluminum flywheels and even some crankcase housings were (and maybe still are) made this way. When examined closely you could see the outline of where the beads were, then replaced by the molten aluminum. The finished products surface finish (as cast) look just like a styrofoam coffee cup. Pretty smooth to the touch, but the expanded polystyrene bead shape can be visible.

Generally the process involves molding a styrofoam part, or a composite part made of multiple styrofoam parts glued together as one to form the final part. This foam part then needs sprues and risers glued on to it for the molten metal to be poured into and the gasses to escape. The part, gating, sprue, riser (foam assembly) is then coated with a refractory coating (sand and a binder) that is either sprayed, brushed or part dipped in the solution. The refractory is put on on one or more coats to get a buildup necessary to withstand the molten metal until the metal solidifies. This varies depending upon many factors like pour speed, cross section, metal being poured, etc. The refractory coated assembly is then placed in a vessel large enough to hold it, and a generous amount of dry sand. Dry sand is poured into the vessel around the part up to and surrounding the sprue and risers. The vessel, sand and refractory coated foam assembly is vibrated to compact the sand around the assembly (more sand is added if needed) to support the refractory and form the mold for the pour. Molten metal is poured down the foam sprue (no refractory on the top end of the funnel shaped sprue to allow the molten metal to burn away the foam and fill the resultant hollow cavity) until the gasses and metal exits the risers. If the refractory coating was just the right thickness, it breaks down just after the skin of the metal is solidified enough to hold the shape and surface finish of the foam part. Other than removing the gating, sprue and riser system, the part is virtually finished "as cast" in many cases, like the small gas engine parts discribed earlier. Hope this is helpful.

kap pullen
01-02-2002, 02:29 PM
Live steam had a story about casting passenger car trucks this way 10 to 15 years ago. The parts were cast in sand not clay.
Just don't tell the E.P.A.
I used foam to cast voids in concrete machine foundations for hold down screws years ago.
Used gasoline to melt the foam out. Looking back, not a good idea.
Kapullen

pabbott
01-02-2002, 05:56 PM
All of this discussion has been very informative but I have one question that doesn't seemed to have been answered. Where the master has been build up using multiple pieces of styro how is the styro "glued". I have used styro in the past and the glue I used would not disolve in any solvent or melt, well not to the extent that it completely disappeared.

Paul A

roberlt
01-02-2002, 11:16 PM
What I want to make is a oil tank for a (very) custom motorcycle. It will hold appx 3 1/2 Qts. (with air space), Mounting brackets will be cast in, Oil filter boss will be cast in, and the tank will be finned so (hopefully) I don't need as oil cooler.
Glue to hold foam.??? My friend (years ago) THINKS he used a very small amount of "super glue" to hold the foam together. As I understand it it vaporizes at appx. 400F. however he said he was able to shake the "blobbies" out after dissolving the foam.
Does anyone know any books, SAE papers, or anything on this?
Thanks again.
Rob

Thrud
01-02-2002, 11:21 PM
Water based contact cement should work - that being said, I have not tried it.

I am still doubtful if Saturn would do it that way (burn out the foam with the pour), I can understand B&S flywheels, but not a $1,000 block where quality is an issue. I am also curious as to using bronze and iron pours using this method. It would make things a heck of a lot easier to do than the traditional green sand method!

dave

Thrud
01-04-2002, 01:51 AM
If you are worried about cooling for your motorcycle (Harley,eh?) you can cool the engine better just by using a full synthetic lubricant with polyalphaoelifin (POA) base stocks. These lubes will drop the temperture 20-50* C. Because of the higher film strength they protect the engine better from cold start ups and greatly reduced friction.

Sounds like a tough project, have you thought about building one with plate and TIG welding it - the "billet" look? However you do it, have fun at least (Ride with a proud smile - bugs are a nice snack on the road - lots of protein ya know...).

dave

[This message has been edited by Thrud (edited 01-04-2002).]

roberlt
01-04-2002, 11:08 PM
Nope NOT a Harley.
1972 Triumph 650 with a factory 750 kit, 750 cams, Mikuni carbs,and lota of other goodies including a twin plunger oil pump with check valves to put pressure to babbitt,roller and ball bearings
I don't know who built the frame, I got it as a "1982 reconstructed vehicle" but the numbers match, so the state, the police and I am happy.
I have (I think) enough billet on it allready Forward controls with shift linkage and brake setup, engine mounts, parts of the front fork ect.
Saturn is supposed to be getting back to me. Also waiting to hear back from the school about this.
How do you tell a happy bike pilot?
The bugs in his teeth

Thanks again,
Rob

Thrud
01-05-2002, 01:19 AM
Robert

You Triumph guys are genuine die hards. I know I would go nuts with the mix of Metric, Imperial, and Whitworth fasteners I have seen on them (and heard so many complaints about). You really have to be in love with the machine to put up with that (me, I like Ramblers - no kidding). I have a customer with one of the new Triumph Daytona's - awesome machine - scary fast!

Good luck - post a picture when you finish it!

Dave

roberlt
01-05-2002, 07:56 PM
You forgot a thread form.
The cylinder base nut are CEI (old brit motorcycle thread allegedly abandoned in 1932).
Check out the (long) discussion on Saturn blocks on rec.crafts.metalworking, it's intresting.
When I get more info I will post it.
Take it lite,
Rob

farmwrench
01-05-2002, 11:08 PM
Get a cat. from LINDSAY PUBLICATIONS (free) lindsaybks.com The have just the book you are looking for on how to do your project. I have not ordered anything from BUGIT CASTING SUPPLY But they will have what you need for supplies (can't remember URL) Saw a great site for a home made hot wire a while ago (crs again). Nice project will you cast it one piece or will it have a side or bottom that bolts on so you can clean it an look for chunks?

roberlt
01-05-2002, 11:17 PM
Thanks for the info.
Do you know which book? they have a bunch on casting.
Tank will have a open top so I can clean it out,run the oil return at a tangent to the curved wall, and put in the plumbing for the rocker box oil lines.
Thanks again,
Rob

Thrud
01-06-2002, 03:23 AM
And I thought I was doing pretty good mixing metric and imperial on my lathe! It amazes me that a motorcycle built in a pretty hip (machinery wise) country like Great Britian would be that goofy. Maybe they had some Canadian choosing the bolts! (we have a warped sense of humour...)

roberlt
01-18-2002, 10:56 PM
This is what Saturn E-mailed me
Dear Robert,
Thanks for writing to Saturn. We are experiencing some circumstances outside of our control which
are preventing us from responding to email in a timely manner. I apologize for the delay in our
response and for any inconvenience this may have caused you.

I do have some information I would like to share with you. Saturn is the first company to use
lost-foam casting to make car components on a large scale. We use lost-foam casting polystyrene
molds to create powertrain components like engine blocks, cylinder heads, and crankshafts
(polystyrene is a material that looks like Styrofoam). The molds are packed in sand, molten metal
is poured in. The intense heat of the hot metal causes the foam mold to evaporate instantly, hence
the name "lost foam." When the foam evaporates, it leaves behind a perfect iron or aluminum
imprint-a Saturn car part!

Lost-foam casting is more precise than traditional sand casting. Less machining and fewer parts are
required, and that means there's less waste. By producing components with this method, we're able
to cast more complex parts and design more features into a single mold. For example, rather than
mounting a separate bracket to the engine block in assembly, we can design the supporting pieces as
part of the block, thereby adding structural strength and saving an operation.

Lost-foam casting makes it easier for Saturn engineers to make quick design changes. They can meet
the fast pace of technological advances without massive retooling. The lost-foam process saves time
and money and contributes to the technological sophistication and competitive price of the Saturn
vehicles

That's how (they say) they do it!
Rob

Thrud
01-19-2002, 01:29 AM
Robert,

Cool! (Pun intended) I am still amazed the foam would burn out that clean. If you try it I would like to know how it turns out for you as far as porosity and the as-molded quality goes. If they can do this with aluminum, cast iron should also work - maybe better? Thanks for looking in to it - very interesting.

Dave

T Wright
03-04-2002, 12:47 PM
When I was in undergraduate school, I did quite a bit of lost styrofoam casting (direct burnout) in making sculpture. We used Dow blue insulating styro. The forms were glued using rubber cement and for smooth surfaces covered in butchers paper or a lightweight brown wrapping paper. Using 55 gal. drums cut down to about 18 inches we could then stack them according to the height needed (you need some height for velocity) for each piece (flair the tops and taper the bottom edge to allow stacking the flask). We used fine silica sand rammed (vibrated with pneumatic bench rammer), as the mold material. my sprues were usually about 1.5 square at the top, tapering to about 1 inch at the connection to the piece.I usually bottom fed the forms. Vents (use a lot of them) were about .5 inch square rods, some came to the top of the flask , others were blind vents to assure full flow to thinner edges and such. Put a steel tube to use as a cup to pour into, you can later melt any aluminum out that's left in the cup. Melt your al. and your ready to go. Always use respirator, eye and face protection,gloves and other safety gear. Fans are a must, expect volumes of black smoke. I don't know the EPA regs about this process and I don't for one minute doubt that you will create a hazardous gas. That being said, we were never casting on a production basis and had no immediate neighbors to complain or harm. Sorry for the long post so late in the thread.

roberlt
03-04-2002, 10:29 PM
Thanks for the info.
I am looking into using plaster of paris around the pattern. Will let you know how (if) it turns out
Rob

gc-john
03-08-2002, 09:35 AM
check out the hobbicast group on Yahoo. http://groups.yahoo.com/group/hobbicast

Theres lots of discussion on lost foam as well as some links to people who are doing it. Styrofoam is mostly air so there isn't that much to burn out.

John

roberlt
03-08-2002, 08:29 PM
Thanks for the info.
I have been checking them out for a while, no info on what I asked but LOT'S of good stuff. (like how to make a inexpensive thermocuple, hot wire cutter etc.)
Thanks'

Rob

Rotate
03-08-2002, 09:11 PM
Check out this website

http://www.dansworkshop.com/

Albert

CompositeEngr
03-12-2002, 12:28 AM
Epoxy is just about the only way to glue Styrofoam.
Just a dot of the 5 min cure stuff, placed toward the middle of the chunks you want to join.
If you must get the little epoxy chunks out before you cast:
Gasoline will melt the styrofoam, but that makes for some nasty nasty waste...
Styrofoam melts at 465 degrees F, so you might be able to burn it out in an oven, depending on part size.

roberlt
03-12-2002, 12:41 AM
Thanks for the info.
Contact cement will also glue foam, also a friend claimes Elmers glue works, will see
Laquer thinner dissolves foam a lot safer than gas.

Rob