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

This is the first installment of what I hope will be a series of updates on making a pouring basin plug using sand and sodium silicate and catalyst. Later, in thhis thread, I will show the lift and trigger mechanism I am building.

First the plug. I decided to make my plug from clean Olivine sand plus sodium silicate and catalyst. I could also have used CO2 for a hardening agent, obviously, but I am making these at my home shop and the CO2 resides out at the barn 16 miles away. I have an oven here for heating the sand/silicate to hasten hardening.
Another material that might be useful for plugs would be graphite. It is easily turned to shape and machines well. Disadvantages are that it is relatively expensive and, because you might need to source different sizes should plug design change, it is a little less easily tweaked. An advantage is that I would expect it to last for many many pours. The sand plugs not so much. They will probably last a few pours or maybe only one.

I am using a an aluminum mold turned on my lathe to shape the plug. I coat it inside with a generous application of Crisco. It has a few degrees of draft and a cap on the small end so I can push the solid sand plug out. I will have a 1/4-20 stud in my plug. Its use will be more apparent later.

The NaSi is mixed 10 parts to one part catalyst. I am using ChemBond 210 (an ester catalyst). Increasing the ratio of catalyst to NaSi does not accelerate the hardening.

Here is the setup.

The plug hardens rock-hard as I am using no sugar for weakening the Sodium Silicate bond.

It takes about 1.2 teaspoon of sodium silicate to .125tsp catalyst to harden a tablespoon and a half of sand.

I will use epoxy to glue in the stud as it will hold better with epoxy than just making a sand-to-stud bond (I think based on experience so far.

The mixed sand and hardener sets up in less than an hour in an oven at 175F. If I were more patient, I could just leave it at room temp and it would harden in a few hours.

Denis

 

Here is a preliminary video showing some of the work done on the mechanism that is intended to pull the plug out of the pouring basin when metal fills the basin. I work alone and really think there is likely significant benefit from allowing the pouring basin to fill prior to pulling a plug on the sprue. So, I needed a practical way to lift the plug.

You will see one of the NaSilicate plugs made above that is supposed to be attached to the weight that will keep the plug in the hole preventing premature opening due to floating of the sand plug.

Realize this is a work just lightly tacked together and very much still in progress. Springs are not yet installed. The rod that connects to the "fuse" wire is way to long on both ends. There is no lifting weight on the long steel arm etc. But by tomorrow evening those problems should be fixed. And, of course, I do not know how well the fuse wire will work or exactly what gauge will be needed. Fun stuff.



Denis

 

Denis-

That is a pretty far-out arrangement, but clever.
I think I will use a foot pedal approach, and it will be something crude for a first try.
I am planning on using a piece of graphite for the plug, and sand it into a pyramid shape.

I am not sure what I will use to lift it; I guess a piece of stainless rod, but that is going to get coated in iron very fast.

I guess I will try everything else first (ie: a designed pour basin, sprue, runners, gates, etc per Bob/John), and then add the plug if I feel like I am still aspirating too much air.

.

 

A foot pedal would be a simple approach, indeed. But, I figure with my trolley and the care needed to get the metal into the basin, the last thing I need is to be balancing on one leg and fishing around with a foot at the precise moment to lift the plug as well.

Looking back, I am quite sure that my pouring setup without a plug results in a lot of air aspiration at the sprue. I will be using basin/sprue/runner/gate mods too to the extent possible. But I am convinced a lot of my bifold generation starts as the metal enters the mold. Then again, just cuz I’m convinced does not make it so.

Denis

 

Well, Bob Puhakka makes some incredible castings, and he makes them in all sizes, and large quantities.
I think his casting quality is second to none, and so you can rest assured I am going to pay close attention to what he is doing.
It makes perfect sense to try and use whatever information that can be gathered to improve our process.

.

 

I just saw this thread. Nice idea.

Could you put the head of a long stainless steel bolt in the plug then lift from the top of the bolt?

 

Yes, not a bad idea. If correctly sized, it would have enough weight. It could be 1/2” or 5/8” diameter. With a couple or a few nuts on the shank it would add enough weight to prevent premature floating. Might just incorporate that idea. Thx!

Denis

 

Another way to trip the plug lifter with no wire or trigger mechanism:

Suppose the beam that lifts the plug were a 1/2" ID tube and arranged so that it just tilted a few degrees downward toward the plug when the plug was in the hole. Now imagine putting 5 or 6 steel, brass, or lead balls in the tube so that gravity holds them toward the plug end and plugging both ends of the tube. Now as molten metal raises the plug, balls roll to the non-sprue end of the tube balancing it tail-down, plug-up. Now there is no danger of plug, unplug, plug like there might be were the plug intended to simply float up on its own.

Another method might be to make the plug so that it would fall over and remain on its side when it first is raised off the sprue. I have not yet come up with what sounds like a reliable fall-over method.

More than one way to skin the cat. the hollow tube end gets "points" for simplicity as does the "fall-over" method.

Denis

 

Some progress was made on the Mousetrap today.

Here is a 60 second video.
It will be interesting to see if the .010" steel wire really does fail almost instantly as the molten metal comes up in the pouring basing and covers it. I am guessing it will break in a second or so.

You can see the counterweight on the lifting arm. It is a friction fit. So it can be moved up or down the arm to adjust the lifting force. The fuse wire just twists onto the anchor I will place in the pouring basin and then onto the trigger bar. I made the triggering mechanism longer than the minimum so that setting the trap is tolerant of a fairly wide range of fuse wire lengths so that setting it up is not unduly fussy. My plan for the anchor in the basin is to drill a small hole in the side of the flask and thread a piece of coarse wire (probably tie-wire) with a loop on its end from the basin and through the hole. Bending as it exits the flask will prevent it pulling back out.



I hope to be trying it out in a few days. In the meantime I have some work to do on runners and gates etc.

Denis

 

Good ideas! I like the rolling balls, or ball. If it's almost balanced when the ball is home it can gain a lot of leverage at the end of the tube.

I had thought a fixed counterweight holding it in the open position, then jam the plug lightly in to the sprue opening. When the liquid lifts it there's no going back.

 

I am thinking about solutions for green sand casting. So I am wondering about jamming a plug into a sand sprue without dislodging chunks of sand. Perhaps incorporate a hard bound- sand pouring basin into the green sand mold? And the other question would be how one could know how tightly to jam the plug so it would dislodge neither too early nor late (or not at all).

The balls in a tube idea sounds pretty good as long as it would not stutter as it opened as the drag of down-rushing iron might pull the plug downward in the early phase of opening.

Denis

 

I think it's one of those things that has to be tried to know. A plug gently tapered slightly more than the tapered sprue would stick nicely just trying it into place, I think. It might take practice to figure it out. I made one bound sand basin and three green sand ones and I'm sticking with green sand if at all possible. It can be made as you're ramming up your mold. With what i'm doing I don't need the extra head so I'm thinking about incorporating the pouring basin into the flask.

The balls in the tube I have no qualms, as long as you're adding iron faster than the sprue is taking it the plug will pop like cork. It might work with a steel plate as well, like the foil plug discussed elsewhere. A piece of 30 gauge steel plate (or thinner) will not absorb much heat as it melts. Aluminum foil has worked well with aluminum melts, placed between teh pouring basin and the sprue.

 

Yes, Andy, I too thought quite a bit about using thin sheet metal like the .0015" thick 6 X 1000" shim stock sheet that is available very inexpensively

https://www.ebay.com/itm/0015-Steel-Shim-Stock-Roll/351446927393?
hash=item51d3de8821:g:HcQAAOSw3ydVmsn4&frcectupt=true

My imagined concern (might not be a problem in practice at all) is that it might melt open in such a way as to allow a wad of partially melted steel to be pushed ahead at the moving front of the molten iron. That is probably not something that would actually be a problem. But my castings do have narrow passages... The other concern was the melt-through time might be more or less than desired. But the foil method is extremely simple and opening time could be adjusted by varying foil thickness or maybe even the number of layers of foil. And that simplicity should be a strong factor in favor of its consideration.

With the wire fuse method the metal has to get to the depth of the wire before the wire will melt and fail...I should add "I think." And it is easy to set that depth as you set up the mold.

Just hashing over some of the things I churned around in my head. I appreciate the thoughts fellow foundry enthusiasts as discussion helps clarify ideas and often presents new avenues of attack.

Denis

 

The trap is set and the soup is on the stove!

 

If this goes right the first time, I’ll be amazed. I am worried runners are too thin and she’ll freeze up midway. And maybe the wire won’t melt quickly. Oh boy!

 

Are you done yet?

 

It worked. Not my prettiest pour. But wire snapped very soon after contact. Video later when I upload it to YouTube. Busy with melt 2...

 

OK, the video you East Coast guys have been staying up late to watch (well maybe not)



Overall I am very pleased with the plug lifter. It is unfortunate how degraded the video as depicted on YouTube is vs the original, but you may be able to see that the dammed portion of the basin fills first as it is supposed to and then metal spills over to the sprue side. Once the sprue side is pretty well filled metal contacts the fuse wire and it breaks in a fraction of a second and then the metal starts running down the sprue fast enough that I have to pour pretty fast to keep up. I guess that is pretty much what I hoped for. I did a second melt and a second mousetrap test which was nearly identical to the first.

Comment: I was better able to keep the sprue pretty well choked for the entire pour. These pours are better choked than I can generally do with my prior round basin and larger runner and sprue. The runner and gates I used in this pour were "tee" shaped and each of the two runner arms was 1/4 x 1" and had four gates each arm. It diminished in size by about 1/4th as the runner passed each gate. Ill show pics tomorrow.

For the pour shown I used 41 pounds of iron and a 25 second pour. I am anxious to dig the castings out of the sand and see what they look like. Both molds seemed to take the expected amount of iron.

Denis

 

I was waiting up in Oklahoma

And posting

A lot of mechanism but it worked great.

It looked like you didn't quite keep the sprue filled, you said you did on the next pour?

That's a lot of hot soup. Your crucible handling system sure works well.

Do you skim in the furnace? Any cover flux?