Some miscellaneous printed sprue info I found interesting…If only I had a 100k sand printer to play with. Helical Sprues in 3D Printed Sand Moulds The helical path uses friction and centrifugal force to slow the metal down, ensuring it enters the mold below the critical 0.5 m/s threshold. Reduced Inclusions By preventing "splashing" at the base of the sprue, it can reduce globular oxide inclusions by up to 35% compared to straight sprues. Defect Reduction Case studies on 17-4 stainless and Al-alloys show that conical-helix sprues can reduce overall casting defects by up to 99.5%. Pressure Stability It provides a "cushioning" effect, preventing the "back wave" or "burping" that occurs when a straight sprue suddenly fills.
Looks like they're still experimenting. Second one simplified the coil but complicated the runner. And what's with the dead end vent looking part off the runner? I wonder if a horn gate could replace the runner.
The leading edge will form a skin on the wall but the sand soon comes up to temp and remelts the skin. When I did a vertical casting and had too small of a tube it just inhibited topping off the riser. Increasing the tube 1/16th of an inch topped the riser.
