Pouring Basin Sand Plug (Sodium Silicate) and Plug Lift Mechanism Fabrication

Discussion in 'Foundry tools and flasks' started by Melterskelter, Mar 7, 2019.

  1. Melterskelter

    Melterskelter Silver Banner Member

    No cover flux. I did skim prior to starting the video.

    I kept the sprue choked most (smile) of the time. There is a learning curve as the basin is at first filling filling filling then spills into the sprue side and continues to fill almost to overflowingand then SNAP, the plug pops and now it’s draining rapidly. I need to anticipate that and fight the inclination to slow as the basin fills. I have no complaint about the plug puller. I did a lot better with it than I could have done without it.

    Denis
     
  2. _Jason

    _Jason Silver

    Looks like a successful pour.

    That's quite a system you have worked out there as well. A lot of thought and trial-and-error must've gone into that.
     
  3. Melterskelter

    Melterskelter Silver Banner Member

    Here is pour number two with the mousetrap. Did not keep the sprue cooked as well as I’d like. Practice should help. Lots of new stuff happening. I think the timing of the plug pull is just right.

    And you are right,Jason, a fair bit of work has gone into this whole process and there’s a ton yet to do.

    Denis
     
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  4. Melterskelter

    Melterskelter Silver Banner Member

    I pulled the castings out of the sand today. to my amazement the "tiny" runner and gate system worked perfectly on the 36" straight edge and nearly satisfactorily on the 18. I'll just upoload some pics for now. More c Mar14Result (2).JPG Mar14Result (3).JPG Mar14Result (5).JPG Mar14Result (7).JPG Mar14Result (8).JPG omments later.
     
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  5. Melterskelter

    Melterskelter Silver Banner Member

    A few more images Mar14Result (9).JPG Mar14Result (10).JPG Mar14Result (1).JPG
     
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  6. Melterskelter

    Melterskelter Silver Banner Member

    Couple of things learned in the last couple days:

    1)Shrink defects occur preferentially on concave surfaces. I guess this should come as no surprise as it is well known that a dome or A-frame roof is quite capable of load bearing where a flat or concave surface is not well suited to load bearing. How does that apply to the castings I did yesterday? The voids that occurred in the 18" SE are not a totally new phenomenon and are not related to the runner system size as I have had problems in the same general area previously. BUT, they always occur on the inside of the SE on the concave surface an never on the A-frame roof surface of the SE. They happen where they do because at the junction of the two broad surfaces of the SE there is quite a bit of metal that freezes last. I forgot to use the the blind riser forms as I was ramming up the mold (thinking too much about all the other "new" stuff) and hand cut smaller than usual blind riser by hand leaving convex domes on them----not a good idea but hard to avoid under the circumstances. So the riser tops sustained the suction of the shrink but the nearby concave surface that failed did not. That surface must be several times weaker than the convex surfaces nearby. I really had not put this concave/convex strength relationship together formally in my mind until today---slow student I guess. But it is confirmed by other observations that shrink defects always occur at the inside corner of a junction of two members, on a concave surface like this one, or on the flat top of a riser vs the flat cylindrical (strong arch) side.

    Planned response: Be darned sure to use the riser forms AND turn those forms and other blind risers in the future as well so that they are concave to make them unequivocally the weakest surface in the region. I like blind risers since they are not subject to being accidental entry point for a slopped bit of iron at the onset of a pour and they don't let other debris into the mold either.

    2) The runner/gate system for the 18 was not quite adequate as evidenced by incomplete filling of the upper outer corners of the SE. Those corners almost filled, but not quite. The metal was 2600 degrees as it left the furnace and so would usually be plenty hot for a good fill. So, I will adjust the runners and gates at the outer ends by 30% or so. As it is, there may be significant pressure loss in the runner as it is pretty thin and pretty long. So, enlarging it should counter that problem.

    3) I am not at all happy with the definition of the letters on the 18. I think that has to do with the way the mold likely fills from the near side to the far side. Metal must cascade over the mold to the far side as well as passing between the lobes of the drag and passing over the lettering as it cascades and slightly erodes the letters. That could indicate a need to ram the sand harder, but in the recent past I have been misting on some sodium silicate (also forgotten this time for the same reason listed above) onto the letters using an air brush. I then use a little CO2 to kick off the NaSi. The sand holds up very well if I do that and the letters are very crisp.

    This is a casting thing is just one long learning process! But I am very glad to have tried the plug which I intend to continue to use. It is also so good to have pushed the lower limit of runner/gate size. My current system probably weight about 20% what the old one did. I suspect this is a better setup for all the reasons Puhakka has put forth. And, yes, I know I ma not following his recommendations exactly, but the current setup much more closely approximates it than what I was doing before. One other advantage of the thinner gates is that removing the residual gate in prepping the casting is much simpler and the risk of a shrink defect occurring at that junction is greatly reduced.

    By the way, simply pushing an "L" shaped piece of common concrete tie-wire into the sand near the pour basin provided an adequate and super-simple anchor for the fuse wire.

    If the images posted are unclear or the text doesn't make sense, I trust I will hear about it. ;-)

    Denis
     
  7. oldironfarmer

    oldironfarmer Silver Banner Member

    I'm following with interest.

    I have a novice question. Why do you not gate into the pattern at the apex of the piece instead of one leg. Would that minimize metal flow distance?
     
  8. Melterskelter

    Melterskelter Silver Banner Member

    I guess I would hesitate (not certain I understand exactly what you are suggesting) to have the metal pouring down into the mold from the apex down. It would be falling onto the lettering, and the randomly traveling to one side or the other of the mold possibly alternating for periods of time. If I am understanding the qustion that scenario seems to be opposite the bottom-up minimal turbulence principal. That was my reasoning anyhow.

    I have been thinking some about trying to pour it with the apex down and the legs up. Not impossible. Lettering would be on the upper surface looking down that way. Still might be OK. Also have been pipe dreaming about standing it on end and gating bottom up.

    Denis
     
  9. oldironfarmer

    oldironfarmer Silver Banner Member

    I was thinking about the exact orientation you have now, one side flat and the other leg slightly up. Just have enough head on your pour to fill the leg up.

    Edit: OK, now I'm confused. I forgot you have a straight edge and a prism.

    [​IMG]

    [​IMG]

    You are coming in a one leg with the apex up (lettering under the top), right? I was suggesting you lay it on one side and pour from the apex (outside of the lettering).

    By the way, what are those round bosses? Are they required? It seems they could be the source of the shrinkage.

    [​IMG]
     
    Last edited: Mar 16, 2019
  10. Melterskelter

    Melterskelter Silver Banner Member

    I like the idea of pouring with the prism on its side. I would have done it that way had I been able to mold it in that orientation. But I still don’t see how to do that. Ideas?

    The “round bosses” you refer to I assume are the two bosses near the lettering. Those need to be there as they provide mounting points for pear-shaped handles. I do not think they are the source of shrinkage. The problem is the amount of metal included at the junction of the two prism faces. That is the most massive part of the casting by far so it freezes last. Metal has to come from somewhere. Previously shrinkage occurred (if no risers) in the corner where the two rib meets the concave inside radius where the lettering is. So I filleted it more there. So now the failure moved from the junction to a more lateral location :eek: I had weakly hoped filetting might solve the shrinkage so that risers would not be needed.

    Those two misshapen lumps outside the casting at the apex were lame attempts at hand cutting blind risers which were poorly shaped being convex and too small.

    Remembering to use my blind risers solves the problem.

    Later I’ll section a casting and the thickness at the apex will be more evident.

    From a purely utilitarian aspect the shrink defect doesn’t matter. But for some odd reason folks balk at buying a casting with such a defect.

    Denis
     
  11. oldironfarmer

    oldironfarmer Silver Banner Member

    To pour on it's side I guess you'd mold it like you do but cut the sprue out the side of your flask, then roll the flask and pour through the side of the flask. It might take some binder in the sand. That would be quite an overhang and you wouldn't want to roll it cross country but set up to roll it at your pouring station. And it would take a flask modification. Just an idea. I assume three large "lightening" holes near the apex would be unacceptable. But they would give you a means to support the sand (and would also provide hand holds).
     
  12. Melterskelter

    Melterskelter Silver Banner Member

    Yes, this mold involves some serious overhangs unless it is oriented with the lettering up. I don't even try to pour it inverted as the "mountains" of sand that create the invaginations of the lettered side would be hanging down. As is, it is tricky to get it to pull cleanly. You have to pull perfectly vertical and level or you crack off the mountain tops. I can do that now. But, that is with gravity on my side. I am nearly certain I would fail 3 out of four times in another orientation.

    Lightening holes unfortunately are not going to be OK.

    Denis
     
  13. oldironfarmer

    oldironfarmer Silver Banner Member

    I realize it's likely not possible, but i was envisioning molding it in the orientation you do now then rolling it 90* to pour.
     
  14. Melterskelter

    Melterskelter Silver Banner Member

    Actually, rotating it to pour would be very easy as the flask is held cope-to-drag with a bracket that has a stud at the balance point horizontally more or less. I use it to rotate the molds in the ramming and finishing process and for general lifting. Its the sprue and runner arrangement would be the challenge. See the pic below which is not an ideal photo to show the stud feature, but you get the idea.

    Flask (4).JPG
    IMG_4870.JPG IMG_4872.JPG
     
    Last edited: Mar 17, 2019
  15. Melterskelter

    Melterskelter Silver Banner Member

    6411E54D-DBF5-4427-9E39-7E17DF65FB34.jpeg Here’s a pic of the fractured prism showing the void—-got lucky as it broke with a 10# maul right where I hoped. You can also see how much metal hides in the apex causing it to freeze last and thus predisposed to shrinkage defects. Remembering to use blind risers prevents the shrink defect!

    Denis
     
  16. Melterskelter

    Melterskelter Silver Banner Member

    Here is a pour today using just a square basin and small dam but no plug.



    I think the shadows are kind of interesting and the square basin with dam clearly works better for me than a round basin did. I was nearly able to keep the sprue choked the whole time. It looks like I could decrease my runner gate system even more as this was only a 15 sec pour and that is about as fast as I feel comfortable pouring.

    On my prior pour today the mousetrap did not fire. It looks like a blob of molten iron by very odd chance landed on the fuse wire as the wire crossed the frame and and "soldered" the wire in place. I guess the moon and the planets lined up just right for that to happen----seems like a 1:1,000,000 chance, but there you are. You'd think such a blob would just fall off or sever the wire. Nope, glued it down. I ended up kicking the mousetrap arm and resuming the pour. Not hoping for much from that fiasco...

    I am thinking about making a full-size set-on-top green sand basin that would allow the entire pour to be run into the basin and then pull the plug probably using a mousetrap. That would solve the drama of keeping up with the sprue as you pour as rapidly as possible while avoiding molten metal overflows.
    One could also use some sort of refractory instead of sand and that might be better. That is why I am interested in the refractory used in the coupolette operation PatJ references in DavisF's coupola thread begun today. I am thinking the sand or refractory would be enclosed in a sheet metal box. Just in the pipe dream stage right now. It could be that the floor of the basin could have a step down area at the drain much like the square basin with weir. You could pour the basin with 90% of expected metal required and then just finish up with a little metal added from the crucible as needed to trim out the pour. It seems like that last 10% goes in fairly slowly and does not present the challenge of the early part of the pour. Knowing exactly how much metal might be needed on a new pour might be tricky but getting it 80-90% right should be doable.

    Denis
     
  17. oldironfarmer

    oldironfarmer Silver Banner Member

    Interesting! Too bad about the mousetrap failure. I hope you got a good pour.

    From the camera perspective, the flask could be higher, or your pouring cart hinge elevation lowered.

    Have you considered a foam plug?

    The beauty of the pouring basin cut into the sand it's quick and easy and lowers the head which is good for avoiding turbulence and keeping the sprue full. They get easier every time.
     
  18. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Actually looked like a decent pour MS. Not sure how it might compare to your non-basin pours. Phone recording in horizontal vs vertical position will always create better video.

    Best,
    Kelly
     
  19. Melterskelter

    Melterskelter Silver Banner Member

    But, the more important question is, will horizontal position result in a better POUR? ;-)

    Denis
     

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