Lets start at the beginning of my casting process. Remember those lathe chucks I cut out of foam in a previous update well I dunked those into a very watery mixture of "polyfilla" It's used to repair cracks in brick walls. I don't know what it would be called where you're from, but it seems to me to be nothing more than plaster of paris.
Oh and don't forget to add a runner as well that is the "tunnel" into which the aluminium will be poured then run into the mold.
This is the "foamy" covered in polyfilla.
Here is the backside of the foamy, you can see the runner sticking out, it's just a piece of styrofoam cut and then glued onto the base. this was done before covering it, so inside that hard crust will be a foam part exactly the shape I want the aluminium to be.
Next I covered the whole part in sand with just the top of the runner sticking out.. I also welded four "feet" to a piece of 120mm pipe, the feet is just to increase the surface area so the pipe cannot fall through the sand into the mold when the styrofoam has been burned out. This is where I will pour the aluminium into, It should stop any spilling from occuring, that will destroy the plastic bucket I'm using. Another benefit is that it will give a bit of fluid pressure to force the aluminium into all the little nooks and crannies I want it to go.
plaster foamy covered in sand with pouring spout
If at this point you're wondering why everything I make seems to be rusted, well the answer is simple .. it's scrap metal... I have a pile of it in my backyard and I use scrap exclusively as a construction material... You simply can NOT beat the price.
The Money Shot!
Okay the next step is one I've shown a few times before, start the furnace and melt some aluminium!! I poured the molten aluminium right into the funnel I made and I was amazed at how little flames the burning styrofoam actually makes.
This is a very exhilirating experience for one you're carrying a very hot steel bucket filled with molten aluminium around, and the anticipation of what might be if this comes out good.. A very odd sensation indeed.
See at least I got some gloves and a leather apron now.
......The wait!
This is an agonising 20 minutes... after pouring you have to wait for everything to settle before messing with it... this 20 minutes felt like an eternity. then finally I figure it's about time I see what is going on in that sand.. I dumped the bucket out to reveal the part.
I saw a heavy lump in the sand and hey it looks like the foam I put in there ... it's just a LOT heavier now... It's still very very hot, but the aluminium has definately set now. The plaster leaves a bit of a crust around it but it comes off really easy with some water.
.... the let down!!!
Okay off to to the tap for rinsing off all the plaster.. and the I see it ... it was a failure :( ...After all this effort and anticipation I have just created a very interestingly shaped ingot to be melted down later.
It looks like it came out good ... just the runner that needs to be cut off...
But NO... the aluminium made it through the cracks in the plasterand since the sand didn't fill those cavaties completely it messed up the casting.
*Look at the detail one can clearly see the beads of the styrofoam on the casting.. In the top picture you can see the cut levels from the cnc process.
So hence the title of this post... The learning process..
I should have used 4 runners with the slots pointing upwards. Well it was a great learning exercise...
Oh and since you may think this is the one and only failure ... you're wrong! Before I welded the feet onto the pouring funnel the first attempt was a complete failure the funnel fell through the sand and into the casting cavity, I was also too hasty to pull it out of the sand and I pulled the whole runner out and messed it up good... at least I knew it was a failure before since the funnel fell through.
A really good mess I made with this one..
But hey it takes 8 minutes to cut another one from foam ... so well worth the time.
So apart from these 2 castings most of my time was used cutting down that rim and making ingots.
Posts
No comments:
Post a Comment