filler for foam patterns

Discussion in 'Lost foam casting' started by Stevan, Sep 16, 2021.

  1. Stevan

    Stevan Copper

    Anyone got any ideas on a material for filling voids and making fillets in foam patterns. I once had some cheap caulk that worked well burning up with the foam, but most silicone caulk does not burn up fast enough and gives voids on the parts and you don't get the fillets in the aluminum that you made on the foam with the caulk. Wax is hard to use as the melt temp is too high. I understand there is a commercially available "Water based wax" that you can paint you foam patterns with to improve surface finish....has anyone used this?
     
  2. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    You're just using a wax with too high of a melting temp. I use a wax for lost foam patterns that comes in fillet shapes, available from Freeman Supply. It's a about $35/box and near life time supply for an infrequent caster. More commonly available sources of low melt point waxes would be toilet ring seals available at any home improvement store, but you need to apply it with mildly warm ball and scraper tools for a professional appearance.

    Check out this thread.

    http://forums.thehomefoundry.org/in...ssions-of-a-lost-foam-caster-5-years-on.1650/

    Best,
    Kelly
     
  3. Tobho Mott

    Tobho Mott Gold Banner Member

    I've used paste wax a few times to fill in small divots between EPS beads and to make small fillets on lost foam patterns. Seems to work really well used in small amounts, and can be applied with a fingertip. Good luck!

    Jeff
     
  4. FishbonzWV

    FishbonzWV Silver Banner Member

    Hot melt glue burns out cleanly too.
    I once did a push/pull action with the glue gun on a fillet and it came out looking like a stack of dimes weld. :)
     
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  5. BattyZ

    BattyZ Silver Banner Member

    One could really give people the run-around with such "welded" castings. Nicely done.
     
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  6. Stanislavz

    Stanislavz Copper

    I am using just ordinary wax from candles. Some messy to work in, but no problems so far.

    And from logistical point - low temp wax is in candles from sex shop. Seriously..

    But still loking for a way how to make wax paste at home. Which could be aplieed wet and dried after it. Or we need an warm chamber - 35 degree and 33 degree wax.
     
  7. Stevan

    Stevan Copper

    Past wax seems a good idea. With a bit of dawn dishwashing liquid maybe the plaster will stick. I will try it.
     
  8. Thud

    Thud Copper

    Hi, 1st post.
    I have used standard paraffin candle wax for fillets. You can modify the "hardness" with a little petroleum jelly in a melted batch...a little goes a long way.
    I have a couple fist size samples I can soften in a bowl of warm water (or just in your hands like modeling clay) & push it thru a clay extruder to create fillet strips & all the shapes your extruder came with.
     
  9. Wild Irish

    Wild Irish Copper

    Great tip, Thud! I've been using toilet seal ring wax, but it is soooo sticky, and still a little hard to form nice fillets. I'm going to try to find a clay extruder and see how that works for me. Thank you!
     
  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I have used a large (1" barrel) plastic syringe filled with wax, and then use a cheap electric hot plate for warming coffee cups to maintain the wax temp. Just put the syringe in the cup of water. You can also microwave it. The resistive heating ones are better than the inductive ones because you can control them precisely with a dimmer switch. Just cut the syringe opening to extrude the desire size wax rope. I only use it to make 1/16" diameter rope I use for fine details but I'd imagine it would work with the clay extruders too. I also thought about using (low) pneumatic pressure to extrusion. Since I have the commercial LF fillet on hand, I just never put further effort into it.

    Best,
    Kelly
     
  11. Mantrid

    Mantrid Silver

    You can dissolve wax in turpentine to make a wax paste. Alter the amount of turpentine to provide the required consistency
     
  12. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I haven't tried Turpentine but most solvents will attack and melt polystyrene foam so I'd suggest you test it on a small piece of foam first. Alcohol will not attack PS foam. Acetone, Lacquer Thinner, and Gasoline will instantly melt PS foam on contact.

    Best,
    Kelly
     
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  13. Smoking Shoe

    Smoking Shoe Silver

    Got around to wiring up my control box thanks to monsoon season here in the Rockies. Never have found the box of missing parts......

    This got me thinking ahead to some actual lost foam casting that I want to do. I have a need for some large radius fillets - around 13mm radius - that are going to by way to fiddly to cut in the foam short of CNC.
    My thought is that this much wax is going to mean a lot more material to vaporize and may cause problems. My question is:
    Would adding expanded Styrofoam beads, as used in bean bag chairs, to some home brew, low melt, low viscosity, wax be worth the effort to reduce the mass of material?
     
  14. What about a whipped cream dispenser filled with styrofoam dissolved in something volatile like ether and then squirted out so the nitrous oxide expands the styrofoam liquid.....hang on you'd have to use CO2 instead of nitrous to prevent it from igniting the ether in diesel explosion.
     
  15. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Yes, but before you go to the trouble, you might want to try to cut strips of foam with either a slightly undersized fillet or triangular cross section, glue it in place to fill the majority of the fillet volume, then just apply a skin coat of wax to finish the fillet. You can cut the fillet profile with a router bit and hot wire off strips of fillet stock. It will be quite flexible and formable but in very tight radii, you may need to make relief cuts in the fillet to make it conform.

    Best,
    Kelly
     
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