Spend the money on mold filling simulation analysis and allow the mold flow analyst to do the same things that create the variation, analyzing potential variables and review the results with your part designers, this will allow one the “wiggle” room needed for the best outcome. For example:
1. After running basic mold filling simulations – based on best practices or using molding parameters based on previous similar designs – start making simulation changes that allow one to understand the limits of the design tolerances based on varying the process – change materials, change the pressure, change the mold/process temperatures, change the filling parameters and gate freeze options to understand desired effects and those molding parameters that result in unwanted solutions. Each part geometry has its own optimized solution.
2. Always run the full analytical mold flow process – basic pressures, gate freeze, sheer/stress and so forth and the full analytical package (mold cooling, warp as needed) – as some folks only run the basics and miss the opportunity to learn about the specific influence(s) that are affected by part geometry, gate & runner size/location, wall thickness transitions, multiple cavity influences, venting and so forth.
3. All these parameter changes in the hands of a skilled mold flow analyst, can be used to guide design changes early in the due diligence process, for best outcome.
4. Correlate simulation work with real results, again this takes skill and careful statistical feedback but certainly help to improve predictive outcome. In my experience, always take a person off the injection floor that has tooling, molding and injection machine set up experience with a variety of materials and teach them mold flow – many times, my mold flow expert says this analytical results makes no sense based on my floor experience, and sure enough errors were found in the model set up thus improving accuracy and improving desired results.