Sunday, September 13, 2020

Nearly flat

So the casting came out pretty flat. But taking it to machine flat is (as expected) a lot of work.

Next time I'll make the cores a 1/2 mm too short. I think they were slightly too long and pushed up the center of the sand a fraction.

I've been working so far with a wood rasp, then a coarse diamond stone to remove burrs. I tried a woodplane, but it didn't really work very well.


Saturday, September 12, 2020

Hands again

 I found that if I use a gas torch from the Large propane tank, and dump a LOT of heat into the ceramic, the wax melts out without breaking the shell. So I have 2 bronze hands. There's still flaws, both have a damaged finder tip. I think this is from the way I've been resting the ceramic shell on the bottom of the pot of slurry while I've been coating the hands, I think they are probably good enough. I'll clean them up over the next day or two and decide.

I may get a small oxy-propane kit and braze some silicon bronze onto the end of the fingers and then file it to shape. See how that turns out.



I think that worked

 The cast used up 2.3 kilos of aluminium including the sprue and risers. I had enough aluminium left over for about 6 muffin ingots. It's a big crucible, it felt like I just kept adding more and more scrap.



Thursday, September 10, 2020

My biggest, most complex cast yet

 

This casting is 60cm (2 feet) long, and has 4 cores, it needs to be dead flat, so I can't live with any shrinkage. A liberal coating of talc to make sure everything separates, I'd hate to do all that work and have the whole thing stick together like a previous smaller casting did.
It's all rammed up, with a tapered sprue, and some pretty big risers over the ends and over the webbing.


It separated cleanly, with the pattern stuck in the cope. Not a huge surprise, and not a problem.

 I cut the gates, and the pattern came out cleanly, I used the split patterns the I made the cores with to make sure the cores were placed correctly.

And now it's all closed up, and waiting for the pour.
 
Cores in place 
Gates Cut 
Pouring Basin 
Clamps Locked 

I know that I have left very little room around the pattern, I have no more sand, I was left with about 2 mugs full of sand when I finished ramming this up. I also know that my pouring spout and center riser are too close to the flask. It will catch fire. I'll chuck some sand over it. I hope I only need to pour this once. If I mess up, then by the time I chuck out the burnt sand, I won't have enough left for another try so I'll have to shell out and buy another bag.
Wish me luck