7.5 Design Process

Now with these pieces of information how one design the process/runner system. A design engineer in a local company have told me that he can draw very quickly the design for the mold and start doing the experiments until he gets the products running well. Well, the important part should not be how quickly you get it to try on your machine but rather how quickly you can produce a good quality product and how cheap ( little scrap as possible and smaller die casting machine). Money is the most important factor in the production. This design process is longer than just drawing the runner and it requires some work. However, getting the production going is much more faster in most cases and cheaper (less design and undesign scrap and less experiments/starting cost). Hence, for given die geometry, four conditions (actually there are more) need to satisfied

(7.47)

(7.48)

the clamping force, and satisfy the power requirements.

For these criteria the designer has to check the runner design to see if gate velocity are around the recommended range. A possible answer has to come from financial considerations, since we are in the business of die casting to make money. Hence, the optimum diameter is the one which will cost the least (the minimum cost). How, then, does the plunger size determine cost? It has been shown that plunger diameter has a value where maximum gate velocity is created.

General relationship between runner hydraulic diameter and plunger diameter.

A very large diameter requires a very large die casting machine (due to physical size and the weight of the plunger). So, one has to chose as first approximation the largest plunger on a smallest die casting machine. Another factor has to be taken into consideration is the scrap created in the shot sleeve. Obviously, the liquid metal in the sleeve has to be the last place to solidify. This requires the biscuit to be of at least the same thickness as the runner.

(7.49)

Therefore, the scrap volume should be

(7.50)

When the scrap in the shot sleeve becomes significant, compared to scrap of the runner

(7.51)

Thus, the plunger diameter has to be in the range of

(7.52)

To discussed that the plunger diameter should not be use as varying the plunger diameter to determine the gate velocity