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3.2 The processes in die casting

The die casting process can be broken to many separated processes which are controlled by different parameters. The simplest division of the process for a cold chamber is as the following: 1) filling the shot sleeve, 2) slow plunger velocity, 3) filling the runner system 4) filling the cavity and overflows, and 5) solidification process (also referred as intensification process). This division to such subprocesses results in a clear picture on each process. On the one hand, in processes 1 to 3, we would like to have a minimum heat transfer/solidification to take place for the obvious reason. On the other hand, in the rest of the processes, the solidification is the major concern.

In die casting, the information/conditions down-stream do not travel upstream. For example, the turbulence does not travel from some point at the cavity to the runner and of course to the shot sleeve. This kind of relationship is customarily denoted as a parabolic process (because in mathematics the differential equations describes this kind of cases called parabolic). To large extent it is true in die casting. The pressure in the cavity does not effect the flow in the sleeve or the runner when vent system are well designed. In other words, the design of the diagram is not controlled by down-stream conditions. Another example, the critical slow plunger velocity is not affected by the air/gas flow/pressure in the cavity. In general, the turbulence generated down-stream does not travel up-stream in this process. One has to restrict this characterization to some points. One particularly has to be mentioned here: the poor design of the vent system effects the pressure in the cavity and therefore effects does travel down stream. For example, the diagram calculations are affected by poor vent system design.



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Genick Bar-Meir ||| www.potto.org
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