The most significant breakthrough in flow simulation technology was the advent of true 3-D solid element analysis in 1999.

Prior to this, the only way to perform a plastics flow analysis was using midplane technology based on the Hele-Shaw approximation. In a midplane analysis, often referred to as 2.5-D, the part model is represented by a shell of 2-D triangular mesh elements, which are then assigned an appropriate thickness. Similarly, runner systems and cooling lines are modeled with 1-D beam elements. Since each element represents conditions through its entire thickness, many assumptions are made within the predictive software code, which may or may not skew the final results. Extracting a midplane mesh is a time-consuming, arduous and ambiguous process that can take several days, in some cases accounting for up to 80 percent of the man-hours that go into a given flow analysis project. While this approach works well for simple part geometries with uniformly thin walls, it does not capture the true phenomena occurring in the runner system and mold base. Significant accuracy can be lost on parts with a moderate to high level of detail, variable wall thickness and/or thick and bulky areas.

Bulky parts with varying wall thickness cannot be accurately represented with midplane technology and require a more advanced solution. In a true 3-D simulation, solid mesh elements, predominantly tetrahedral, fill the entire volume of the part geometry, without the modifications and assumptions associated with a midplane. This results in a much better representation of the original part file, and therefore much more accurate simulation results.

The 3-D meshing process is highly automated allowing users to create a solid element model in a fraction of the time spent generating a midplane. However, 3-D models have far more elements than midplane models and require longer solve-times and more computer hardware. This is a small price to pay, considering that 3-D analyses can run on an unmanned PC overnight and offer significantly better results.