Always the “one-before-last” casting on
each runner-end shows misrun or coldlap
defects in about 5% of the molds. It is
proven that some pourers achieve nearly
zero-defects, while others have up to 5%
defective castings.
The defect can be explained by the filling
pattern of the gating system. A nonpressurized zone is built in both runners
exactly where the defective castings are
located in the mold. This allows the melt to
enter the castings partially, rest and then
continues to fill. If the temperature on the
melt front is high enough, nothing happens.
If the temperature drops slightly, the defects
show up.
¬ The slow-down can be seen in the filling
animation, but also using filltime plots
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