In this example Flow Service played a key role in optimising the die during the design phase, as regards the balance of cavity filling. This result was achieved thanks to simulation, some results of which are shown below. The case examined is an 8-cavity family die.
The study focused on modelling the runners so as to obtain a good balance between the cavities. The die has eight impressions of the same part; to avoid differences between parts of the same shot it is therefore necessary, first of all, that the metal reaches the gates of the various parts at the same time, as far as possible, while still in the first phase.
As the following pictures show, the first (standard) runner solution proposed led to a clear imbalance.
The lower cavities are almost completely filled while the metal has not yet reached the other, upper gates.
Changes to both geometry and process were therefore needed. In the following simulations, besides testing different runner geometries, a higher than usual first phase velocity was used, to counter the effect of gravity as much as possible.
The pictures show the second geometry proposed, obtained with a fairly large fillet radius on the secondary runners, in the direction opposite to the flow.
The upper front is further ahead than in the previous case, but still very far from the cavities to be filled.
The effect of opposing the flow direction was therefore increased as much as possible in the design of the secondary runners, as shown in the following pictures of the third and final solution proposed.
As the pictures show, the balance during the first filling phase was greatly improved; the second phase (high velocity) can thus start in a situation much more consistent with a "good filling" of the cavities.
There will therefore be far fewer air entrapments caused by turbulence, and the parts of the same shot will be much more similar to each other. Note that the different colours in the pictures are not related to different temperatures, but only to the different colour scales used.