The next step for the turntable project was to make the platter. This was the second of the two cast aluminum components to make, and unlike the Technics which is die cast, this too would be sand casted. However, this time I chose a different molding method called "sweep casting" which is applicable to radially symmetric parts like this. This was my first time trying this, and I had relatively favorable results.

The sweep pattern is basically a cross section of the part being casted, which is swept around a central axis to remove pre-rammed sand layer by layer. Think of it like those center pivot irrigation systems, except instead of watering crops, we're removing sand to create a mold cavity.
This has the advantage of saving time since I didn't have to make an entire wooden replica of the turntable platter. I began by transposing the final dimensions of the platter, plus shrinkage allowance, into a flat piece of plate. Pardon the atrocious blueprints