Poured today, one good, one disaster

Discussion in 'Lost foam casting' started by garyhlucas, Jan 2, 2020.

  1. garyhlucas

    garyhlucas Silver

    Weather was pretty decent today so I decided to try and pour the last pieces for the CNC router we are building for the FIRST robotics team. The carriage casting came out great but the 4th axis headstock was a total fail. With all the rain we have had my sand got wet. I thought I got the wet sand out but clearly it wasn’t dry because the steam just blew the metal right out.

    So I spent the rest of the afternoon turning piles of scrap into clean ingots. The scrap produces lots of dross but when I melted the ingots for the pour there was very little dross.

    While melting scrap I was heating sand in a stainless bowl on top of the furnace to dry it. Still need to get it all dry and keep it from getting wet again.
  2. garyhlucas

    garyhlucas Silver

    A couple of things I learned today. I was running furnace way too hot. Cutting back the fire I saved a lot of propane and the melting time was no longer. All that heat going out the exhaust.

    When melting for ingots it goes much faster if the crucible is kept partially filled so the next charge goes into a molten pool which melts it much faster.

    The electric ignition on the Mifco furnace is really nice, just push a button start the blower and purge the furnace and open the gas valve and start the ignition. Same for shutdown.
  3. FishbonzWV

    FishbonzWV Silver Banner Member

    I thought you had figured that out months ago when you were dealing with your swiss cheese castings?

    Yep, it's called leaving a heel in the crucible.
  4. garyhlucas

    garyhlucas Silver

    Yes the porosity problem went away earlier by cutting back but today I played with it more and found I could cut back a lot farther yet.
  5. OMM

    OMM Silver Banner Member

    I know what you’re talking about, but.... you’re dipping into a huge engineering efficiency thing. The variables are unlimited!

    Controlling fuel, combustion air, exhaust and exhaust back pressure, and this is all on the fly, if you change crucible sizes, there are even more variables.

    I do strongly believe that the more factors you wish to ignore you can tune in efficiency.

    - you’re not willing or able to change your exhaust port dimensions.
    - you’re not willing or able to change your combustion air.
    - you’re not willing or able to change your furnace dimensions.
    - you’re not willing or able to change fuel flow.
    - you’re not willing or able to change torch tip fuel flow rate.
    - you’re not willing or able to change the atom size of the fuel.
    - you’re not willing or able to create a turbulence chamber for the fuel/air mixture.

    Hey, I’m guilty of quite a few things.... and I have not even made my first fuel melt in a furnace.

    I have made many dozens of melts an electric furnace, and even a few over a camp fire with aluminum.
  6. FishbonzWV

    FishbonzWV Silver Banner Member

    Good for you Gary, saving gas is always a good thing and I bet the quality of your castings went up too.
    That, ladies and gentlemen, is called getting to know your furnace.
  7. garyhlucas

    garyhlucas Silver

    I think I figured out a way to dry the sand. Got a 4500 watt 240 volt water heater element 14” long. On 120 vac it pulls 8.5 amps. Adding some aluminum fins bolted to the U shaped tube and plunging it to the bottom of the can should allow me to heat the sand above boiling and drive all the water out.

    I also came up with a waterproof roof over my foundry. A 12’ flat bottom aluminum row boat upside down! One end sitting on brackets bolted to a fence. The other end when down protects everything, and gets raised up on a 7’ high support when I want to cast, even if it is raining! Fireproof too.
    joe yard likes this.
  8. Tobho Mott

    Tobho Mott Gold Banner Member

    I've never needed a way to make my sand dry out. When you find a way to stop it from drying out, I'll be very interested! :D

    Sounds like that should work well though, and some version of it could be a good method for warming up the sand too, when it is cold enough that the water in it wants to freeze.

    Pretty good use for a rowboat too!

  9. garyhlucas

    garyhlucas Silver

    Well winter is kicking my ass. Two more failed castings of the same part. Wet sand, even went and bought more sand at Home Depot. One bag was dry and the other wet! Steam just crushes the part. Afterwards the sand around the sides of the can is soaking wet, it condensed there.

    My sand drying heater spear overheated and burned up. Dry sand at the center of the can and the vapor condensed against the cold sides!

    Also I put the parts in the sand flat and all the larger flat surfaces on the parts blew out. Didn’t see that before when I angled the parts so no surface was horizontal.

    Unless I can find a way to dry 500 lbs of wet sand I am done for the winter. Bummer!
  10. Patrick-C

    Patrick-C Silver

    Why do need to dry your sand? Well because its too wet, but why?:cool:
  11. Petee716

    Petee716 Gold Banner Member

    It's shipped wet to keep the dust down and to keep it from flowing out of torn bag corners, etc. plus I'm sure it brings the weight up.
    Gary I assume you're pouring lost foam. I've never had any luck drying out playsand by any means other than air and sunshine. I'm in Buffalo, NY so I feel the wintertime blues too. I sure as hell ain't pouring today!
    Your sand isn't going anywhere so you can wait till better weather to dry it out, but in the meantime your best option is probably going to be sourcing what you need to get you through, dry, either by trying to select a different already-dry product at the big box or builders supply, or else consider a different media. I would bet some of their other bagged sand varieties are dry.
    I have used glass bead sandblast media. It has refractoriness and is as fine as sand. A friend of mine gave me a 50lb bucket of it that he had no use for, and it was uncontaminated. Otherwise it's about $40 at Harbor Freight. I wouldn't buy it for that kind of money, but you might be able to source it somehow.

  12. FishbonzWV

    FishbonzWV Silver Banner Member

    Cement mixer and a weed burner. Put a couple gallons in and torch it.
    Surely you don't use 500 pounds at a time so just do a couple hundred to get by until summer.
    Tobho Mott likes this.
  13. Patrick-C

    Patrick-C Silver

    You could use a cheap harbor frieght heat gun, or animal heat lamps over a 55 gallon drum cut lengthwise filed with sand. And as it drys scoop off the dry sand and put in an airtight container.
  14. Al2O3

    Al2O3 Administrator Staff Member Banner Member

  15. garyhlucas

    garyhlucas Silver

    I have no indoor place to keep the sand. Especially after it is used and has that styrene smell. I think the wide temperature swings are condensing moisture on the metal cans. I just got a 2 gallon electric cook pot to see if that will work.
  16. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    A 5-gallon plastic bucket with a snap lid to store sand.....? Inside/outside....no matter. It will be dry, but outside it wild be cold, but you could bring it inside without odor with snap sealing plastic lids.

    I have 5-gallon steel buckets with lock ring lids. I store my sand inside. -No stink when sealed in a bucket. I mold inside (my shop). I can smell the sand while I'm molding it but not afterward. I have bucket dollies with wheels but also carry 5-gal buckets outside just before I pour. I melt inside with resistive electric furnace.

    I clip the garage door opener to my side, walk the crucible full of metal out the overhead door, pour, and walk back in, place the crucible in the furnace and close the door (heated shop). I demold outside by dumping the flask casting and all on a pan. I quench the casting in a water bucket, then walk back inside and leave the sand to cool on the pan. Then I shovel the sand back in the steel bucket, clamp the lid on and take it inside. -Done.

    If you have a heated shop or garage, you could do same except you must melt outside. If you don't have a heated shop then that makes Winter a much bigger drag for casting!

  17. garyhlucas

    garyhlucas Silver

    No heated shop, foundry is out in yard at my grandson’s house. I have an extension cord for power. Started a new job today. We’ll see how much time I have this going forward.
  18. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    60 days til Spring!

    PROSTOCKTOM likes this.

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