Simple Solutions That Work! Issue 12

48 THE DESIGN PROCESS The general design process consists of the following steps: • Simulation of the ‘Naked’ Casting • Gate Sizing and Feeding Design • Rigging Geometry Creation • Verification via CFD/Solidification Simulation DAVID C. SCHMIDT Vice President FINITE SOLUTIONS, INC. ARTICLE TAKEAWAYS: • Gate and feeder bar sizes are determined based on thermal modulus data from simulation • Gates are positioned to provide feed metal to the areas that need it • • Simulations for design purposes take only a fewminutes FEEDING SYSTEM DESIGN BASICS FOR INVESTMENT CASTINGS “NAKED” SIMULATION The first step in the rigging process is to run a simulation of the part ‘naked’; without any rigging system. Simulation results show the effects of the part geometry on the overall solidification. In this simulation, filling analysis is typically not done, which provides extremely rapid results, and can point out preferred gate locations which promote directional solidification. All that is required for the initial simulation is a casting model, normally provided by the customer in STL file format, and basic process details such as casting alloy, shell material, pouring temperature and shell preheat temperature. GATE AND FEEDER BAR DESIGN The data from the unrigged simulation can be used to design the rigging components. The gates are typically designed first, followed by the feeder bar. The software uses the progression of solidification, along with a pattern recognition algorithm, to determine the separate feeding paths on the casting. The software can find the last points STL model of a step block casting. ‘Naked’ simulation results, without filling.