Friday, May 29, 2015

My first aluminum pour! [Again!]

After revamping my flasks and (especially) the Petrobond arriving I've been anxious to ram up some molds (I think that's what the cool kids are calling it) and pour some aluminum.

I decided to not get too carried away and just went with something simple: the epoxy patterns of the Old Filthy keychains. 

Got them rammed down in the drag and the parting line dug down to about half the thickness of the pattern. Two of them managed to shift while ramming. Hopefully it won't be a problem but I'll need to be more mindful of this in the future.
I assembled the flasks and packed the cope portion complete with a riser and vent tube. I didn't pack it all the way to the top because I didn't want to use all of my Petrobond in one pour. It still had a good 1 1/2 inches on top of it.
Then I separated the flasks to reveal a somewhat reasonable parting line.
The sprues were cut to the riser and vent in a somewhat haphazard manner. I don't think these are super critical as long as they are a reasonable diameter and don't zigzag all over the place. By varying them slightly, it will give me something to compare and contrast after the pour to see if I am correct in my assumption.

I also made an extended riser to keep additional pressure on the molten metal (via gravity) as it cools and contracts. I know this wasn't my only problem when I tried the lost wax/plaster molds but I think it was a contributing factor.
Speaking of the plaster molds, it was time bring the furnace up to temperature and preheat the alumumin pieces before melting them down. I decided the first things to get melted down would be the failed pieces from the plaster mold attempt which I guess was technically my first pour making the title to this post somewhat inaccurate. The little blob at 3 O'clock was from an overpour while making muffins.

Since the failed pieces were made of mostly Lone Star cans, and I didn't want to come up short on aluminum, I decided to add a muffin from the scrap I melted a couple of weeks ago. And then it was a matter of waiting for everything to be ready to pour.
The aluminum in the furnace was ready. (That's 1355 degrees Farenheit!)
The mold was ready for the aluminum.
And the author was almost ready to pour. (One more swig for good luck.)

The pouring part was mostly uneventful though I did get carried away and some aluminum blew out below the extended riser and the top of the sand. (Relax. Shortly after taking this pic, I moved the riser and blew out the flames.) Between the cardboard tube and the wooden flask it seemed to smolder and smoke so bad I thought for sure the neighbors were going to call the fire department.

And then... more waiting. Thirty minutes later, the center of the mold was still 325 degrees F.
Finally, it was cool enough to bust open and reveal my creation! I was careful to keep the chared Petrobond seperate and scraped it into a seperate container. I'll need to figure out how to reclaim that, if possible.

And here's the casting. It definitely isn't perfect but it came out much better than I expected. There is some cleanup that needs to be done at the parting lines and in some of the features and I'll post more pics after I do that. But, for now I am VERY glad to have something come out that I didn't immediately feel like remelting.

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