Announcement

Collapse
No announcement yet.

LOST STYROFOAM CASTING

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • LOST STYROFOAM CASTING

    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

  • #2
    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
    grace & peace
    will

    Comment


    • #3
      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

      Comment


      • #4
        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

        Comment


        • #5
          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

          Comment


          • #6
            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.

            Comment


            • #7
              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

              Comment


              • #8
                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

                Comment


                • #9
                  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

                  Comment


                  • #10
                    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

                    Comment


                    • #11
                      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).]

                      Comment


                      • #12
                        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

                        Comment


                        • #13
                          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

                          Comment


                          • #14
                            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

                            Comment


                            • #15
                              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?

                              Comment

                              Working...
                              X