Die pre-heating has a beneficial effect on die life, by reducing
thermal shock and stress fluctuations on the die surface. The
findings from this paper indicate that the die surface stress
decreased by 44% when the die is pre-heated to 150°C, and decreases
by 57% when the die is pre-heated to 200°C, in comparison to when
the die is started "cold" with an initial temperature of
20°C.
Changes to the die start-up procedure, by switching off the die
internal water cooling for the first four casting cycles, results
in the die heating to operating temperature in fewer casting
cycles, resulting in fewer castings being scrapped before the die
achieves steady state operating temperature. From this, a saving of
four castings per start-up can be made, reducing scrap by 4.5%,
leading to lower manufacturing costs, reduced energy usage and
increased useful die life. The modified die start-up procedure had
a negligible effect on the die surface stress fluctuation, with a
beneficial reduction in scrap.
The process improvements which were run to improve die life,
show that by modifying the die start-up procedure, the scrap rate
can be reduced making the process more profitable.
