Don't you hate it when all you get is a lump...

Discussion in 'Lost foam casting' started by garyhlucas, May 24, 2019.

  1. garyhlucas

    garyhlucas Silver

    That looks just like the part!

    Tonight was our first melt and pour. Did lots of things wrong, and was really expecting the worst. Trying pulling the part from the sand too early and pulled the sprue and pouring cone right off. So imagine my surprise when this is the result!

    The aluminum was scrap 6061 and a little 6063 maybe. Not supposed to be good for casting. I saw that the big difference between the 6061 and 386 casting grade was about 7% silicon. So I purchased a lb of silicon off ebay and mixed in about a third of it to the 8 lbs of aluminum. I have a pyrometer but for some reason it was bouncing all over the place. When it bounced up near 1500 F we shut of the furnace and poured. As you can see from the saw cut it looks pretty solid and I got 100% fill and few small bumps where the spackle was a little thin. The foam was straight off the CNC with no sanding or filling of any kind. Sloppy job of coating it with spackle too.

    I shot a video of the pour which I haven't downloaded from my camera yet. It'll show you all the mistakes we made. Like not realizing it filled completely really fast and we poured about half the melt on top of the sand!

    This is a housing for a peristaltic pump I am designing. The foam was CNC cut to the exact size I wanted with no allowance for shrinkage. So I figured I'd cast it up and measure it to see how much it shrinks in each direction.

    So I am really psyched now.



    sIMG_3528.jpg sIMG_3530.jpg sIMG_3531.jpg sIMG_3532.jpg sIMG_3533.jpg
     
    _Jason and Tobho Mott like this.
  2. Lost foam casting is deceptively easy.

    Nice job!

    I like to pull my sprue a little green to save trimming. I don't find much shrinkage with lost foam. But I cast straight extruded materials like window frames. Not even 6061, and I add nothing. And get good results.
     
  3. garyhlucas

    garyhlucas Silver

    I was fully expecting a partial fill, float up ,porosity, and all kinds of other issues. It just worked! I can see what I need to improve on so the next one should be easier. I can see that 10 lbs of aluminum is quite a lot of parts so I really need some more sand containers so we can pour multiple parts in one session. Junk yard has some nice little steel drums with clamp on heads for $6. They are a little deeper than a five gallon bucket.

    Next pour will be same part and no silicon added so I can compare.
     
  4. Steel drums are great. Looking forward to your pour without added silicon.
     
  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Good job Gary. Everybody's first impression is.....this will never work.....then.....

    Better grab those. They are great. With metal buckets you don't need to worry about melting through the side and the sealable lid means you don't have to smell the sand when it is stored. I made myself a base with wheels and a vibrator on the bottom. Then you can just lift the buckets on and off of the base to vibe and pack multiple molds.

    You could get by with a much smaller contact area on your part and not have to extend it into the casting interior. -Makes degating and clean up easier. Probably get by with much smaller sprue in general depending upon what/if you are using some sort of pouring cup/basin.

    What type of silicon did you use? Did it seem to dissolve ok? If it was lump, it helps to pulverize it. Most aluminum foundries use master alloy silicon waffles that are already alloyed with ~%50 aluminum. They melt and go into solution much faster. Also, no Fe in it. Most of the eBay stuff is lump Ferrosilicon. It will definitely help fluidity but Fe will reduce aluminum strength. Not sure what you paid for the FeSi but most of the eBay sellers are >$10/lb delivered so it ends up being at least $.7o/lb of metal dosed.

    Best,
    Kelly
     
  6. garyhlucas

    garyhlucas Silver

    sDSC01355.jpg IMG_3335.JPG Kelly,
    The silicone came from https://www.ebay.com/str/jetsjewele...-Making-Supplies/_i.html?_storecat=2499557014
    He claims it is 98% pure and the cost with shipping for one pound was about $25. Just wanted to experiment and didn't really spend lots of time looking. It seem to dissolve into the melt okay, I stirred it well with a stainless rod.

    I know what you mean about the pouring sprue. The rectangular shape was a waste and at the time I'd didn't have a good way to make round pieces. It just dawned on me I have some long small end mills and I can just bore them right out of this soft stuff. I made a sheetmetal pouring cup but I like your idea of a reusable refractory one.

    The one photo here shows my vibrator strapped to the metal can. It did a good job, the sand flowed like water. The other photo shows what I did to the tongs I got with the furnace. I didn't like the idea of pulling a red hot crucible of molten metal out of the furnace, setting it down in the pouring ring, picking it up again and making a pour, setting it down again and picking it with the tongs and returning it to the furnace. Seemed like a long process and lots of chances to tip the crucible over. With this setup we grab the crucible, pour and return it right to the furnace.
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Rectangular sprues are fine. I can't really say one is any better than the other as far as rectangular vs round. I bought a set of woodworking plug cutters. The largest will cut 1" diameter by 2" long. I bought them mostly to make bosses for foam pattern making but I use them for sprues too.

    1_1 Plug Cutter.JPG

    For a couple years I just used a 2 1/2" D by 4" long piece of muffler pipe and foil tape to transition from the cup to sprue. I made a reusable pouring basin because the cup and cone seemed to aspirate air. I only have a couple dozen pours on the reusable pouring well but seems to work well. I have a couple different versions of them now.

    http://forums.thehomefoundry.org/index.php?threads/reuasbale-offset-pouring-basin.688/

    I'd like to see more pictures of that. I use an open ring shank and have a lift off furnace so accomplish same.....snatch, pour, and replace with one tool.

    Best,
    Kelly
     
  8. Gary: Are all your pours two man pours?
     
  9. garyhlucas

    garyhlucas Silver

    All the tools that came with the furnace from a school are two man tools. I am working with a 15 year old so I think the two man pours are safer at the moment. Here are some frame grabs from the pour video we shot. 5ceadae5.jpg 5ceadb38.jpg 5ceadb95.jpg IMG_3341.JPG IMG_3343.JPG IMG_3346.JPG
     
    Tobho Mott likes this.
  10. Looks like you've got good help.

    If he was helping me I'd make him wear long pants and heavy leather shoes though. An unfortunate accident could leave him disabled for life.
     
  11. garyhlucas

    garyhlucas Silver

    You are right, we need more safety gear. I think a fire resistant apron and heavy shoes are needed.

    Wonder a bit about the heavy shoes. I was cutting with a torch one time and a blob of molten metal went down my 9” high laced up boot and got lodged under the ball of my foot. Ever try removing a laced up boot while screaming in excruciating pain? I hobbled around for six months before it healed. Loafers might have been nice that day!
     
  12. Tobho Mott

    Tobho Mott Gold Banner Member

    When I splashed some bronze and a drop got in through a hole in the side of my shoe, the whole pouring area was covered in red hot bronze BB's from the splash, no safe place to step if I had kicked my shoe off. Besides, I was carrying a mostly full crucible so the safest thing to do seemed to be to just pour the molds, do a second melt (aluminum) as planned, pour that mold, put everything away safely, then go inside and have a look at my foot. Oddly, it was another drop that had merely bounced off the top of my shoe that gave me a bit more serious of a burn.

    I'd tuck your boots into your pants leg to keep anything from falling into them. You could also get some of those spats (I think that's what they're called) to cover your laces.

    Jeff
     
  13. Jason

    Jason Gold

    I wear leather steel toed boots, but with no laces. I can kick them off if the need arises.
     
  14. I just bought some foundry boots but keep forgetting to wear them.:eek: Normal is steel toed boots with spats for brass and up.
     

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