The original design featured three ingates: one main ingate at the bottom center and two lateral ingates to provide fresh melt into the thin-walled area from the sides. The assessment of the filling temperature results in the simulation revealed that this concept did not work. During filling, most of the melt flowed primarily through the center ingate and further through to the top of the casting. The lateral ingates did not contribute much to the filling of the die at all. Consequently, the melt temperatures in the thin-walled area dropped too quickly and significantly, increasing the risk of cold shuts. In addition to the predominant center bottom filling, this design created another problem. The velocity of the melt originating from the lower ingate was too high and generated splashing during the filling process.
The Surya TOTO engineering staff concluded that a change of the die design was necessary to improve the situation. However, due to the resources required for die changes, the modifications were requested to be as small and as easily realizable as possible. As part of the reduction of effort in the tool shop and on the shop floor, possible variations of the existing design were developed and analyzed using numerical simulation before starting modifications. Based on the earlier conclusions for the existing design, the lower ingate as well as the filling pressure curve were selected to be changed. However, instead of lowering the flow rate at the main ingate by a reduction of the diameter or width, the Surya TOTO engineering team decided to try and remove the ingate completely. This solution would, if successful, not only solve the problems observed, but also increase the yield and improve the overall cost effectiveness of the production process. To test and validate the new design, the engineers again consulted the filling temperature and air pressure results of MAGMA5. The simulation-based optimization also included the improvement of the filling pressure curve for this new design to minimize splashing of the melt and air entrapment.
The results for the new design were promising and indicated significant improvements. The filling temperature profile for the thin-walled area was considerably more advantageous, keeping the melt in the section of the casting in danger of cold shuts above the liquidus temperature long enough to eliminate the risk for defects. Also, splashing and turbulence were both reduced considerably by filling exclusively through the lateral gates. Consequently, the danger of blow holes was significantly reduced. Based on these results, the engineering team decided that this design was worth the effort and ready for an actual shop floor trial.