Current simulation tools account for the physics of fluidity, and should be capable of predicting castability too. Investigating thermal resistance shot sleeve heat loss effect of conventional HTC values.
Excerpt from the December 2014 article from Foundry Management & Technology by R. Bhola and S. Chandra
The term "thin-wall castings" for the HPDC process has been investigated for well over two decades. However, the perception of what is considered a thin-walled part has changed over the years and continues to change. Historically, 3-mm wall thickness was considered a thin HPDC part and that number decreased over the years to 2 mm, and further to 1 mm. Currently, there is a push for even thinner walled parts in the electronics industry, with thickness demands as low as 0.6 mm. The automotive industry has been looking to make ultra large castings (ULC) using various processes, including semi-solid, permanent mold, and HPDC processes, with target thickness in the range of 1 to 2 mm.
Thin-walled parts are difficult to cast because the melt cools rapidly upon contact with the relatively cold die steel and can solidify quickly before die filling is complete. The distance a given molten material travels before it freezes and stops moving is commonly referred to as "fluidity". The dominant variables affecting fluidity are: thermophysical properties of the melt; the temperature of the melt above liquidus (superheat); and mold coating release agent[3,4]. Much of this work on quantifying fluidity was based on experiments under low pressures, generally not exceeding 15 psi to force the liquid metal through a passage.
Further, die temperature and the heat-transfer coefficient at the die surface do not seem to be considered properties that define fluidity, though Dewhirst acknowledged that the heat-transfer coefficient at the mold surface does play a significant role in the measured flow lengths for a given alloy type under given test conditions.