Casting a windmill gear in grey iron

I thought that was a riser, and the metal would be bottom fill/bottom entry via a sprue or something.
But I guess I am thinking in terms of a typical casting, and not lost PLA.

Lost PLA is still rather foreign in my mind as to how it goes together/works.

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With respect to gate freezing, from my perspective, a .700 opening is huge for sand casting. Obviously the iron has to push the vaporizing plastic out of the way for David, so a large funnel makes some sense and I understand is based on DavidF’s experience. In contrast for green sand, I bottom gate a 10 pound casting (19 pounds including pour basin, runner and blind riser) that is somewhat thin-walled through a short runner and gate about 1/2” x 3/8” The flow through the .7 gate would be more or less 80 times (in theory Poiseuille's Law ) that through a gate I used. At least it would be an order 20 to 40 times greater.

So, freezing on the basis of gate size hopefully won’t cause trouble. Of course, nature is the final arbiter of theory. Watch it freeze off! ;-)

Denis

 

Oooohh. I missed that!

Then that funnel is the equivalent of the fuel port on an Indy car. The mold will fill in 1 sec or so.

Denis

 

OIF is doing greensand
Pat tried resin bonded
Melterskelter will try NaSi
DavidF is pouring in shell
ESC will try greensand and/or linseed oil bonded and maybe lost foam if I get a pattern.
Anybody I missed?Kinky Friedman. Or molding method? This is going to be great. Blues Brothers?

 

LOL, this is pretty interesting thread and will be interesting to see the different processes. I knida feel guilty for putting you all through this!!

ESC, I am getting caught up (well belt on mower deck broke) so maybe I can print tonight or tomorrow. Do you still want that stripping plate? If so I will have to figure out how to draw that up.

If that involute cutter was here, I would try and see if I could cut the foam on the mill. It might work considering the 3.5" cutter could generate a fair bit of SFM.

 

Mr. Ed-
You have created an unofficial "casting competition", but I guess it is more of a comparison of methods.
I hope to cast my mold, such as it is, for comparison to the other methods.

And I really like this application because it pushes the limits on making parts for working things, and thus a lot of attention has to be paid to shrinkage, mating of parts, accuracy, etc.
This is my kind of thread, and win, lose or draw, I will learn a lot from threads like this.

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I think Chvorinov's rule is going to say the cylinder has a modulus of about .7x1.5/(.7x2+1.5x2) =0.24 in. The 0.7" circle would have a modulus of 0.7 area divided by circumference or about 0.18. So the gate is smaller, maybe not by much. And since it is the small end of a cone, and next to a large flat surface, it will not cool as fast as an isolated cylinder. And since the cylinder has a small ID it won't get full cooling on the interior. If it were a full cylinder the modulus would be about 0.75. It's probably borderline but will work. Chvorinov's rule is surprisingly easy to apply with a few shortcuts on simple shapes. My foolproof solution would to add a 1/2" long cylinder to the end of the gear to be machined off.

 

Green sand update.

Here's my pulling rig. I just couldn't get the mold out of teh sand without wiggling it. No action picture, I was too focused on getting it done.



The little weight slides up to rap the pattern vertically after it's rapped into the sand radially. Worked like a champ after I added a sleeve into the wood to get the tolerance down.

Ed: For the stripping plate start with the large end gear profile and create a sketch then use the offset function (I used 0,060" and it was none to big) under the Sketch menu. Just scaling it up does not work.

I had the same problem with this pour, and upon deflasking I see I barely had a connection at the bottom of the sprue. Poor sand ramming. But the gear looks OK.



I had a little mold offset but it's in the mail.

 

Yep, I was thinking bound sand. My error.

It should all solidify about the same time, I assume, so you can't help shrinkage issues. Is that true?

 

The big difference to me is as it all cools slowly it should reach the mushy stage at about the same time, lower temperature gradient across the casting. Then grey cast iron doesn't shrink upon solidification so, cool, or hot, should be a stable transition.

 

A short video of the cast iron gear pour in green sand.

 

That is a good video Andy. It looked like it was still on the cool side when you went to the ingot mold. I have been able to get good castings at cooler than optimum temperatures, but I had larger sprues and runners.
I went back to the video and a big chunk of slag falls to the lip, but they usually float and since the sprue was choked I don't think it got down the sprue. Any other post pour evaluation?

 

That gear looks very good.

That was a sizable hunk of slag. Practically nothing solid could pass though the sprue chokepoint. Without the chokepoint I think that sprue and runner should have worked.

One thing I could not see (might have been there) was a shiny surface on your metal in the crucible. That would indicate 2550F for adequate pouring temp.

I have adopted your sheet metal angle shield to prevent burning of the flask by radiation from the crucible. Works quite well unless I slop which I do a lot less since I have cut ridiculously large square pouring basins.

Denis who is still fooling around with the triangular hollow pattern and thinking about making the silicate mold for the gear. One of these days I’ll get off the dime and actually make a mold....

 

I tell you guys what, I am in awe of all of you. I am learning so much just reading. The biggest thing is I need to get the boatload of other projects completed, so I can focus on casting.

Andy, I will see if I can figure out the stripping plate tomorrow … supposed to be raining (AGAIN). I think I have used that offset function before.

 

The gear looks good but had some mold shift wo we'll see. I think my sand must have sea coal or a similar component. I'm still struggling with the temperature. I agree it is probably not hot enough. I think I need a smaller slag dipper.

When reviewing the slow motion I'm confident the flow stopped just after the slag falls in. It's a little hard to tell. Maybe it didn't cause the stoppage. I plan to section the pouring basin to see if I can see any indication of slag. I don't know what to look for. The casting looked clean all over, not pock marks and each end machined clean. Ed can tell us more when he bores it. I decided to send it unmachined thinking his standards are a little higher than mine and didn't want to mess it up for him.

I was thinking the slag didn't even make it close to the chokepoint.

What I saw in the crucible was a lot of convection, liquid boiling up from the side of the crucible. I'm not sure what I'm looking for. You mentioned mercury before, does it lose it's orange color and turn silver? When I first scraped slag I thought I saw a very smooth shiny surface like I see on aluminum. I had a lot of slag because there was a lot of rust and scale on parts of the charge.

I've seen the swirling eddies when forge welding and didn't see any of that. The rolling fluid was moving too fast.

The pour was in bright sunshine which of course alters your perspective.

I need to add some Satanite to the brick or change to 3,000F.

I thought the iron had excellent fluidity were it not for the slag dam holding it back. I'm aggravated with myself that I didn't clean it more.

 

That is a great effort Andy.
It seems like every time I do a pour, I learn something new, and I see things I never noticed before.

I played around with iron for the longest time before I was able to get really hot melts (like 6 years on and off).
My new lower mass furnace helps a lot, as does figuring out a good setting for the burner and combustion air (3 gal/hr diesel).

The discovery process is part of the fun, but when pours don't turn out exactly as planned, that can be very frustrating.
Never give up though.
Success means much more when it is not easily achieved (at least it feels that way to me).

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