Mixed results on shell castings today

Hello Forum,

I am posting some pictures from today's casting. All parts were invested in Suspendaslurry, the patterns were jewelry wax from a silicone mold I have used before. The results were 1 piece OK 3 not but with different defects. All wax patterns were burned out in my repaired electric oven and then allowed to cool. They were reheated to 500F in the oven and remained in the oven until just prior to pouring. Shells were set in casting sand 1-2 minutes before pouring.

You can see the investment had a really good take on the wax patterns. Last picture is ones I cast in Pertobond a long time ago with the original pattern, used to make the wax samples used here.

Brand new aluminum, from ingot. No recycled material. Was using a digital pyrometer. Made sure the charge was hot in the crucible before pouring.

Any constructive suggestions would be appreciated. Do not need comments that are, "You did it wrong".

Thanks,

 

What is the sprue pattern? Aluminum is pretty light metal and needs a tall feed sprue to generate enough pressure to force it into details like that.

 

That is a very good point that I did not consider. I made the sprue pattern (shown here) with my 3D printer and using a 2 piece mold, cast them in wax. This was my first attempt at using this "idea" of casting sprues. I would definitely make them wider and taller.

 

What temp was the aluminium at when you poured?

 

I try to keep the charge at 1450 F measured with a digital pyrometer. I watch the material in the crucible and I wait for it to be all melted.
I check the temperature during the melt and just prior to taking the crucible out of the gas foundry. Any thoughts. It was warm, here yesterday
when I was doing this pour.