Lost Foam Pros/Cons

Discussion in 'Lost foam casting' started by Al2O3, Oct 16, 2017.

  1. Ronald

    Ronald Lead

    I use a Pattern Maker Styrofoam from a place called White Pines Pattern Lumber Co., I bought ten sheets of 4'x8'x2" panels in the 70's, and have used them for everything including that waterbed ever since.

    Yes, I have posted on Chaski and AA, so it's kinda redundant to do it again, but you wanted to see what amateurs had done in Lost Foam.

    I'm not a foundry hobbyist, but a Live Steamer, as can be seen in this project on U Tube:
    I made several castings for those two Turn Tables including the sides and roofs of the shacks.

    Just got thru casting four #8 Switch Frogs, but they were done with a wooden pattern in C99700.
     
  2. cactusdreams

    cactusdreams Copper Banner Member

    What is the coating used in your last photo of the bone shapes pieces?
     
  3. Ronald

    Ronald Lead

    Those are steam locomotive connecting rods made in styrofoam, and coated with ceramic slurry.

    I top gated these because it was easier for me to pour. They also are poured out of C99700. The cross-sections are so large I did not need to preheat the shell when I poured.

    The ceramic slurry was by Remet: http://www.remet.com/range/shell-room/ , and it was at the local junior college Art Department that I did several of these in ceramic slurry castings, including a full size locomotive bell bracket which has yet to be poured out of A319.

    At that time, they had difficulty keeping the slurry in solution, because the mixer would accidentally get unplugged overnight, I have not attempted to use any type of slurry at my home foundry.

    DSCN9757_2.JPG
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Thanks for that Ronald. That turntable is truly impressive. The detail....all those rivets, a true labor of love and excellent result. I'll need to take in more as time permits.

    On the shelled lost foam connecting rods, I presume you just fired the shelled foam patterns and other than your remark about not needing to preheat the shell, just treated it as if it were lost wax but the expendable pattern was foam...correct?

    Best,
    Kelly
     
  5. Ronald

    Ronald Lead

    I finished TT #2 awhile back, it's just a matter of putting that project on U Tube.

    The ceramic slurry covered foam patterns were let dry, and then burned out in the Art Departments large ceramics oven. They poured a mixture of metals in that night school bronze casting class, but I wanted that C99700 alloy, so I took them home to pour in my foundry.

    The Art Departments Chairman, not the Instructor, complained that what I was doing was not art! I told them, art is in the eyes of the beholder, besides, part of my real-estate taxes support this school! Most people were making wax sculptures like human or animal figures, my "art" was just a little different.

    I have two more slurry covered patterns that were never burned out but just let dry. Because the cross sections are large, I will just bury it in sand, and hope that the foam burns out when hit by the ~ 2200'F metal; but that has been a low priority project for a loooong time.
     
  6. HT1

    HT1 Gold Banner Member

    OK from the outside I've only ever done sand cast, about every sand imaginable Petrobond (my only amateur option), green sand, Sodium silicate (CO2 sand), Phenolic Urethane No Bake (PUNB), How much detail can you get from LF Can you get small intricate detail for Plaques???
    generally I was lead to believe detail was in this order best to worst lost wax, Diecast, sand, lost foam..
    of less importance to me but an issue of conversation where is the best dimensional accuracy or for the sake of this thread how dimensionally accurate is lost foam...


    V/r HT1
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Coating the foam patterns with drywall mud reproduces a remarkable degree of detail that rivals lost wax, but not to the degree of the silky jewelry investments. I think the level of detail is limited by the level of detail achievable on the foam pattern and here in lies the limitation because although you can get a surprisingly good finish on the XPS foam, it isn't gloss like flame polished wax. The pore size of the extruded polystyrene is probably the limiting factor but that is a long way down the scale on quality of finish.

    The problem I have is it actually reproduces every surface flaw present on the pattern to the finest detail.

    Again, I think that is limited by the pattern not the process. If the pattern is reasonably rigid, it's a non-issue and the process is as dimensionally accurate as sand and maybe bound sand. If you have a very thin and fragile pattern, it can be difficult to prevent pattern distortion when packing in the loose sand. With care in how you gradually fill and vibe the mold this can be minimized. Gluing fragile patterns to a rigid plate or board with foam standoffs will solve the problem for fragile patterns.

    Best,
    Kelly
     
    Last edited: Oct 22, 2017
  8. HT1

    HT1 Gold Banner Member

    Can you expound on that please specifically lets discuss the pattern if that is the limiting factor, because I have seen lost foam that really looked like chunks of an old cooler, and I have seen work that looked extraordinary, but I have never seen anything I would call fine detail... I can reproduce the texture on a feather in petrobond, litterally by gluing a feather to a pattern, what is the best level of detail obtainable in lost foam???

    V/r HT1
     
  9. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Not sure I'm answering your question because you're asking about surface finish detail but quoting my comments about pattern rigidity and casting accuracy. If you were attempting to produce that fine of detail in the foam itself, the foam I use will not support that. I suspect you would need a very dense foam and that goes the opposite direction of the low density foam you want for burn out.

    In your example, if you glued the feather to a piece of foam, coated the foam with drywall mud prior to casting, I bet the feather would burnout and reproduce well. I've had finger prints in the vicinity of fillet wax cast through but that was the wax, not the foam. I'm making machine parts and sand the foam with worn out 220 grit cloth abrasive. The surface finish of this foam improves with grits as fine as 300. I have not tried to produce finer finishes than that because I'm getting better than most sand casting processes and they're machine parts, not art or jewelry. If you could find a polishable coating that burned out clean and didn't attack the foam you might do better. I'm satisfied with the finishes for my purposes and just haven't had a need to explore that avenue.

    I use wax fillets and appliqués for finer details such as below. Best advice I can offer is to get a chunk of the pink insulation board and carve and sand it to get a feel for the art of the possible. The pink board available in the big box stores is extruded polystyrene (XPS), is about 1.3lbs/ft3, is a good compromise of low density and workability, and it works pretty well. The white stuff is expanded polystyrene (EPS) bead and it works poorly compared to the XPS.

    5 Detailed.JPG
    Logo Detail.jpg

    The casting is dirty and just wire brushed after quenching in a water bucket. I didn't go to great lengths to get this result but you can get a general idea of what casts through but it's basically representative of the surface condition of the pattern. This surface responds well to vibratory media to clean and for consistent coloring.

    Are you thinking about it's applicability to your bronze plaque work?

    Best,
    Kelly
     
    Last edited: Oct 23, 2017
  10. Ronald

    Ronald Lead

    Detail: In the photo attached, the two headlights were made out of foam, then coated with pattern wax, smoothed, and shellacked.

    They were then invested in Ultra-Vest ( difficult to keep from floating up.) and burned out. They then were vacuum cast as I did with all the other little wax Lost Wax castings on this locomotive.

    I think, including bell, hinges, railing supports, door handles, flag holders, etc., there are close to 300 casting I made to super detail this EMD TR-4 Cow & Calf.

    Those headlights are about as best you can do in foam.

    DSCN0199_3_2.jpg
    DSCN0196_2.jpg
     
  11. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    The headlights do look nice. Happen to have a close up?

    I think if you intend to use shell and/or investment and burn out prior to pour, that may open up the possibilities a bit for coating and finishing the foam. I fiddled with shellac but found it didn't seem to burn out very cleanly during a pours through unfired coatings supported by loose sand.

    I run a metal fab business. EMD is my biggest customer. I get around to their manufacturing sites and was just at their corporate supplier's conference last week. Thanks for the post.

    Best,
    Kelly
     
  12. HT1

    HT1 Gold Banner Member

    Yes and No, I'm not going to change my process, because of ease of repeat ability, what I would really like is some apples to apples comparison to point people to so when they ask how to do this? we(The community) can be on the same page... I mean I know the limitations of my process, and I can probably sand cast very complicated pieces with back-draft ect., come on I'm a journeyman molder with a Saucer, cup and spoon under my belt for me to send people down that road is unrealistic... Kind of like the fools that show up for the first time intent on casting steel :)
    saucer cup spoon.jpg

    I've seen people here doing lost foam above what I thought was possible So I would really like to know what the limitations are . Can you cast 25Lbs of brass? if foam is your limit on surface finish what foam is best? is it carvable, gluable? Maybe not here on this thread, but I would really like to see where Foam Shines above other techniques and where it falls short... I know that is hard as most of us specialize in our area of Success But it would make great information for all

    V/r HT1
     
  13. OCD

    OCD Silver

    HT1,

    You actually bring up an ideal solution and group effort whether you realize it or not.

    Maybe, just maybe, if for say a 4 week period or shorter, a select group of individuals or anybody for that matter, were to agree to concentrate on any particular aspect of casting such as foam, CS, etc. and report back with detailed notes, pics, etc., then the community can compare notes and see what the very best procedures are with the best results.

    Make it a contest if that’s what it takes to get more people to participate.

    Just an idea.

    Even a wise man can learn from the village idiot.
    You just never know.
     
  14. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Just wondering if you have had a chance to peruse my other threads in this Lost Foam sub-forum because they and post #1 of this thread are my chronicle of sorts to the process strengths and capabilities. It all being done in dry loose sand that was merely poured in and vibrated in place can offend the sensibilities of skilled Journeyman molder but I find it quite remarkable.

    I can't do 25 lbs of brass because my smaller (A20) oven is electric and I have not built my natural gas burner and fired my larger (A60) fuel fired furnace. I don't have molding sand, flask, nor muller and I haven't rammed up a flask nor packed a core box in over 15 years. I've always been more of a pattern maker than foundryman but a couple years ago I decided to build a home foundry and started chipping away at it. I built the furnace and molten metal handling tools and then in March I got off the highway on the lost foam exit ramp and have been tooling around LF town ever since. Wasn't my plan but I became so impressed with the process, here I am. I do foam because it's presently all I'm equipped to do but could do lost wax and shell in a matter of a few days. Take a spin through my threads and let me know what you think.

    Best,
    Kelly
     
    Last edited: Oct 23, 2017
  15. cactusdreams

    cactusdreams Copper Banner Member

    Interesting questions. For me the decision to go LF or sand is mostly about the shape of the piece, how many I want to make and how time consuming the pattern making is. Not sure how to test the limits of detail but sometimes I'm amazed at the detail of the foam beads captured. The mud will capture any detail you can carve in the foam so the carving is the limitation in my opinion. That said, pink foam sands pretty smooth and a wax coating is another option. As Kelly said you could reinforce longer, thinner pieces by attaching something to it. Never tried it though. I think that's why the big boys use LF mostly for big blocky shapes and not too much surface detail like engine blocks. A brass plaque doesn't seem to lend itself to LF but we might be surprised. I did this in AL once with LF.
    watson 3b.jpg watson 4.jpg
     
  16. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Hey, that's a nice piece Cactus. Did you hot wire those letters and attach them or razor knife?

    I tend to agree with you on the suitability of LF for highly detail artwork plaques, but I bet you could really do some impressive reliefs with even one of those small desk top CNC engravers.....and for house markers for simple things like letters and numbers, pretty hard to beat for one-offs.

    Best,
    Kelly
     
    Last edited: Oct 24, 2017
  17. HT1

    HT1 Gold Banner Member

    In the long run I suspect sand cast traditional pattern process would be better for simple house markers , one set of patterns letters glued to a reusable back, soak the whole thing in water over night after use and you have all your letters back. The rubber stamps not reversed is very easy and inexpensive for any simple 2D plaque, combined with some simple and reusable ornaments and you can do alot at a very low cost... and of course if there is a minor problem with your first try, loose sand , gas , cold metal, you still have a pattern for another try. and if you have a CNC engraver you can cut wood or plastic and use it for a pattern, I've done it

    same back different letters
    https://scontent-mia3-1.xx.fbcdn.ne...=8ce754354bc6be4ce6d3dc1e995c4255&oe=5AAE34C9
    https://scontent-mia3-1.xx.fbcdn.ne...=4be4dc27e6cd61350604337536ba0bfc&oe=5A6743AD
    https://scontent-mia3-1.xx.fbcdn.ne...=d18ef8b43e1b5a61b2bbb3b41e9a59af&oe=5AB03CEC

    Here is a plaque cast from a simple CNC engraved pattern. if I had added a reusable boarder I could have made all kinds of differnt signs
    https://scontent-mia3-1.xx.fbcdn.ne...=716ccec79069a551eb6731488e0d4cb4&oe=5A65C68E


    V/r HT1

    P.S. I'll be very open, the thought of only having one try for the use of a pattern scares the Ht1 Chips out of me :-(
     
  18. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    That's definitely an advantage but the flip side of that is you are not bound in anyway to font, letter size, plaque shape, or any artwork or applique patterns and if it is a one-off, than can provide quite a bit of artistic freedom.

    BTW, as far as simple letters, numbers and profiles go, those same patterns you mention can be used as templates for guided hot wiring foam reproductions.

    Agreed, the pucker factor is high as you tip the crucible above the pattern.....plenty of motivation to get it right! Once you got things dialed for plaques of approximately the same size and wall thickness, I think success rate could be very high.

    Best,
    Kelly
     
  19. HT1

    HT1 Gold Banner Member

    Some sort of Pantagraph sort of operation???

    I did leave one thing out above Lost foam could be used to make a master pattern for sand cast :)

    V/r HT1
     
  20. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    A Pantagraph would be another option but I was thinking more along the lines of using the letters directly as the template and guide pattern such as the methods shown in my machining XPS thread. Changing guide bushings and cutter profile would allow variations on the letters.

    Best,
    Kelly
     

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