Accessory Pouring Basin

Discussion in 'Foundry tools and flasks' started by Melterskelter, May 15, 2020.

  1. Melterskelter

    Melterskelter Gold Banner Member

    Today was a very nice day in my part of the world. So, after spending a few hours yesterday molding one of my 30" precision squares I melted 70 pounds of iron losing about 5 pounds to slag and poured the mold using an accessory pouring basin. I use the add-on basin as I tilt the mold about 3 to 4 inches over its 30 inch run in hopes of making the mold fill more evenly. If I did not use an accessory basin, the cope would have to be 9 inches thick and itself would weigh 250 pounds. By adding on a 30 pound basin, the cope can be only 4 inches thick and weighs only 130 pounds as does the drag.

    I have used accessory basins about half a dozen times now and have been surprised how well they work.

    You will also notice in the video that boards that are screwed down onto the top of the mold to prevent the sand lifting. I found out the hard way that the sand will lift on this mold if I neglect to attach those boards.

    I also use small plywood tabs bridging the cope and drag to prevent the cope separating from the drag slightly---those tabs make the difference between a casting with some small but generally acceptable flash and one with virtually no flash at all. On this particular mold I want to keep flash to an absolute minimum as the A25 crucible is within an inch of the brim when carrying 65 pounds of melted iron. The big basin makes it much easier to pour the relatively full crucible as aiming the first bit of metal is less critical with a big target.

    I mold the accessory basin before I draw the sprue pattern plug and then separate the accessory basin from the pattern. I then cut the sprue into the accessory basin. Once the mold is in place out near the furnace I put the accessory basin back on the mold. Because I am concerned about dislodging sand when joining the acc. basin to the mold I put a 4" square of notebook paper on the mold covering the sprue opening and then carefully drop the basin onto the mold. (I know the exact location of the basin as I talc the top of the mold before removing the basin. The talc makes a perfect outline of the basin and its flask. I also intentionally cut a depression about 5" diameter into the top of the mold to help capture and orient the accessory basin.) The paper catches and sand before it has a chance to enter the main mold and I just blow it out of the accessory basin/sprue. That paper disappears instantly with the first drops of molten iron.

    You will also see that I cut a large vent into the top of the mold to allow gases to easily escape as the mold fills and to also give me a visual clue that the mold is full of iron.

    My good wife was kind enough to video the pour and learned how to use the zoom feature on the camera.





    And for those who have not seen the square, here is what it looks like. Dimensions are 30X12X4": IMG_6528[1].JPG IMG_6530[4].JPG

    Denis
     
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  2. FishbonzWV

    FishbonzWV Silver Banner Member

    Wow, that's a lot of iron. It seemed the pour went on forever.
    How many times do you skim before removing the crucible from the furnace?
    I guess a big pot of iron like that will retain the heat pretty good. I kept thinking...pour, pour, pour.
     
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  3. Melterskelter

    Melterskelter Gold Banner Member

    I think I skimmed the crucible 3 times prior to taking it out of the furnace. I had to skim to get enough room for the full charge as the slag was about an inch thick prior to the first skimming. It seems like skimming is easier when the metal is hotter as the slag seems to separate more easily and completely from iron. I also will mention that a heat-shield on the skimmer prevents a smoking glove that tends to happen if I don’t have the about 5x8” 1/8” aluminum rectangle between my hand and the screamingly hot furnace chamber when doing in-the-furnace skimming. This is not so important with the crucible outside the furnace As that last skin is really quick and there is not so much radiant energy from the crucible.

    The pour took about 30 seconds and that was somewhat by design. In a prior 15 second pour I got some sand wash. It wasn’t too bad but visible. With that pour my gate was roughly 1.5” wide and about 1/4” high. This time the gate was almost 4” wide and 1/8” at the thickest in the center and closer to half that at the edges. The hope being to produce more of a river delta flow pattern. The prior pattern may have been causing too much of a river rapids that had to change direction 90 degrees immediately after entering the mold cavity.

    I am about to head out to the foundry and do some digging to see what happened...

    One kind of interesting thing I observed yesterday as the casting slowly cooled in the sand was that a gap in the sand developed at the outer edge of the vent that I had cut on the upper end of the mold. And the sand started cracking. Surely this was due to the contraction of the casting. I Previously measured 3/8” contraction on the 30” side just as predicted by expected shrink rates. Since I almost never (except for this pattern) use an open riser/vent, I have not been able to see this happening right in front of my eyes. Anyway, nothing earth-shatterering, but fun to see.

    Denis
     
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  4. Melterskelter

    Melterskelter Gold Banner Member

    Here is a photo of the contraction effect on the sand

    4C7252EC-91DD-46D7-98C1-1B1C50444ECF.jpeg

    And here are pics of the casting which filled nicely and is usable. However, the sand was seems worse! Now I am trying to figure out my next steps to mitigate this. I am a bit frustrated. B15AE6EC-A554-4BC1-9875-EA007DC7C4A1.jpeg 49319F04-526C-4CEA-980F-F187BE805585.jpeg C792112F-F024-4169-871F-481B6932AC76.jpeg
     
  5. Al Puddle

    Al Puddle Silver

    nice camera work
     
  6. Jason

    Jason Gold

    Is this a second one for yourself?
     
  7. Melterskelter

    Melterskelter Gold Banner Member

    None are for myself. I am selling them to help support my casting habit. I have orders for two more.

    Denis
     
  8. Jason

    Jason Gold

    Orders are a good thing! Good going, that's tough in this economy.
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    It helps that, to my knowledge, this is a truly unique item that fills a niche void.

    Denis
     
  10. Was the iron a bit too hot when poured Denis?. I see it flowed into a thin gap in the mould which would need hot metal to do and the finish of the thin iron flashing is smoother than the rest of the casting. Those last two aluminium castings I did in sodium silicate were poured a bit too hot so I have sand evenly distributed in the metal where it's machined.
     
  11. Melterskelter

    Melterskelter Gold Banner Member

    I wish I knew the answer to what is the optimal temperature for casting this piece. I cast it about 2550F. I usually pour in that neighborhood. If this were a simple plaque or chunky gear or pulley pattern, I think I would go 50 to 100 degrees less. But, since this is a pattern of long thin sections, I am concerned about cold shuts which I did see when I accidentally poured this short a while back and also poured about 2480. It is certainly true that cooler pouring would produce a nicer finish.

    How hot would you pour it? How would you prevent the sand wash?

    Denis
     
  12. Petee716

    Petee716 Gold Banner Member

    Remind me of how you're measuring your temp? Sorry I'm not quaLifted to answer your question, just wondering.

    Pete
     

  13. I'd take the easy way out: polyurethane no bake resin with the added crosslinker additive that boosts heat resistance and mechanical strength at the expense of the glue's life (not an issue here). PUNB pretty much eliminates sand wash and can even let you change the design of the gating as such, so long as you don't have any sharp corners to burn and break off, you're pretty much golden. In the photos below, only the white pouring spouts and shink bobs are made from iron rated PUNB and hold together at aluminium temps well enough to need breaking off with a hammer, at bronze and iron temps the glue eventually chars and disintegrates so the castings fall out of the loose sand in the mould. So for the short duration of the pour no sand comes loose at all. It's hard to get and has about 6-10 month life depending on how old the batch you bought was. The brown sand spouts and moulds in the pics are all sodium silicate.

    That 40? size crucible is really going to hold the heat well, I'm having trouble with second and third castings having cold shuts in bronze with an AX16 sized crucible where pouring with an AX20 or AX25 is a non issue. The last iron pour I did with an A25, I stuffed around for a minute trying to find the glove heat shield while the crucible was out of the furnace and it poured fine, although the thinnest section was 3/8 thick.

    It should be possible to get a two component urethane resin glue and mix Bostik Desmodur RFE crosslinker in to get the same result for small quantities but it's more expensive this way. Desmodur RFE is an isocyanate which is toxic but it breaks down over time into CO2 and water and I believe it will char with molten metal contact. Even after casting with normal PUNB you want to be upwind of the acrid smoke normally but it disperses fast.


    Edit: In your case Denis, it may be possible to use a glue based facing sand with a reasonable cure time and ram it up with your normal sand on the back, once cured the glued sand will be easy to brush graphite over for iron service and after casting the glue sand disintegrates back into loose sand or leaves easily removed chunks. Unlike other sand resins it is considered easy to dispose of and suggested uses include capping off land fill as it breaks down with sunlight and moisture unlike alternatives.


    pouring spout.jpg pouring spout 2.jpg
     
    Last edited: May 17, 2020
  14. FishbonzWV

    FishbonzWV Silver Banner Member

    It looks to me that you had sand float where your pouring basin is. Would it be possible to make a steel plate to screw down on the cope and place the pouring basin on top of the plate?
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    Mark,
    I like the concept a lot and have day dreamed about it some. And I have longed for a practical bound sand solution for a long time. My operation,as small as it is,does not lend itself to use of resin bound sand to make molds fully of bound sand. Larger operations can afford the cost of mixing and reprocessing equipment that are marvels to see in operation. But for me to mix 300 pounds of sand for a one-time use would be cost-prohibitive as well as presenting significant disposal problems.

    Using resin sand for facing sand sounds good if it would work in practice. Concerns that I would have would center around how well the bound sand layer would adhere to the green backing sand, stripping of the bound sand without it wanting to separate from the backing sand, and, if those issues were surmountable, after casting, separating the bound sand from the green sand.

    For me, sourcing the PUNB in small quantities would be a challenge as well.

    Have you ever tried using a combination of resin-bound facing sand and green sand backing? I have used and liked silicate cores. But have never used face/backing combinations. Anyone?

    Denis
     
    Last edited: May 17, 2020
  16. Melterskelter

    Melterskelter Gold Banner Member

    Yes, the ferrostatic pressure did force a bit of separation between the cope and drag at the low (higher pressure) end. So, I will look at the the bottom board (actually sheet metal with a square tube frame) and add in a strut or two for stiffening and look at how I can stiffen the cope as well. I am suspicious the drag may be at fault here. Pics of that when I do it.

    Denis
     
  17. Melterskelter

    Melterskelter Gold Banner Member

    A while back a foundry owner sympathetic to my cause loaned me an immersion pyrometer. Once I realized the disposable tip contained a Type-S thermocouple and simply generated a milli-volt reading, I got busy on my lathe and
    used a piece of stainless tubing and some brass to make a goose-neck tip holder connected to a boxed-in milli-volt meter that works very well to make accurate temp readings of the melt. I took it to two foundries and compared it to their several-thousand dollar pyrometers and mine was in 20-degree agreement with theirs. Good enough for me. I buy tips from the foundry. One tip is about 4 dollars and is good for a few melts (ten readings?) if I am very careful to not bump it.

    I'll write this up when I have time.

    Denis
     
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  18. Petee716

    Petee716 Gold Banner Member

    Thanks for your reply. I've read here about folks not being able to measure iron because of being out of range of their K-type pyrometers. So aside from one-time use methods I didn't know there was instrumentation available for it. If you mentioned it before I must have missed it. I'll look forward to your write-up.

    Pete
     
  19. Peedee

    Peedee Silver

    Who was the guy on AA (probably pre the eventual AA forum) that worked a commercial foundry, he had huge knowledge in bound sands. Made a lot of belt buckles as a side line but got in trouble for using the forum in his spare time. Did a good piece on horn gates.
     
  20. Melterskelter

    Melterskelter Gold Banner Member

    Here are pics of my bottom "board"/transporter.

    Because this mold is too wide for my usual straddle transporter that I use for all of my other molds, I just added removable running gear to the bottom board. When I am pounding sand, the running gear is standing by. And then when the mold is completed, I pin the running gear to the bottom board and bolt on a handle to the flasks and then wheel the whole works out to the pouring area. It is quite easy to roll the 300+ pound assembly to where it need to be. Then I use a jack to raise one end of the assembly off the wheels and slide them off the axle leaving the axle attached to the board and lower the mold to its desired incline for pouring.

    Here is the original configuration of the board that may have been springy enough to allow the flash seen in the last pour. I welded in a few stiffeners. The jack is intended to fit into the square area at one end of the board more or less at the top of this pic. IMG_6631[1].JPG
    Here it is with 4 added stiffeners that I think will be adequate. It is pretty easy to add in stiffeners as needed. Sorry this photo is inverted compared to the first.
    IMG_6632[1].JPG

    Here is the running gear. I attach the running gear while the flask and mold are suspended from the hoist as I am lowering them off the molding bench. The ears and pin in the middle secure the gear to the board. IMG_6633[1].JPG IMG_6634[2].JPG IMG_6635[2].JPG

    We'll see how this goes next time. It feels stiff enough so that no oil- canning of significance is likely. Shoulda done it in the first place. But my main concern on building this was to prevent racking of the flasks and it did that just fine.

    Denis
     

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