The Die Therm Solution


The die casting industry has to date, at best, loosely controlled the thermal aspect of the die casting process.  Die Therm provides comprehensive control for this aspect of the process.  The key to Die Therm’s approach is focusing on heat rather than temperature. 

 

In principle, the approach that the Die Therm System takes is straightforward: 

 

1.   Based on the geometry of the die, calculate targeted heat to be removed in total and for each cooling channel.

 

2.   Measure coolant inlet temperature, outlet temperature, and flow rate for each coolant line/channel during production.

 

3.   Control the coolant flow to achieve desired heat removal, which achieves the desired die surface temperature (the key is control of heat not temperature)

 

In practice, the Die Therm software is a tool for calculating and controlling the target amount of heat to be removed for each cooling channel.  Coolant temperature is measured by a resistive thermal device (RTD), which is accurate to within 0.01oF.  Coolant flow is measured by either a solid state or paddle-wheel flow monitor.  Flow is controlled by a solenoid valve.  All of these are used independently on each cooling channel. 

 

The following shows this schematically:

This solution provides real-time data, the most important of which is actual heat removed for each cooling channel.  Further, the valve controls coolant flow per channel, thereby providing continuous control over heat removal. 

 

This approach rapidly achieves an operating die surface temperature, which is maintained by gradually increasing coolant flow rate as bulk heat builds in the die.  This is shown graphically as follows:

Compare the above to the typical die casting process .

 

The above graph shows flow gradually being increased during startup.  Once sufficient bulk heat has built up in the die, the process operates in “Automatic” mode, in which bulk heat has reached equilibrium, to which the Control System controls, maintaining consistent thermal conditions in the die.

 

For a hot start, the same process occurs—flow is increased as bulk heat builds up in the die.  However, because the die is already hot, the Control System will increase coolant flow much more rapidly until operating in “Automatic.” 

 

Porosity location can be controlled merely by adjusting the targeted heat removal of the various cooling lines.  Further, because the Control System precisely removes heat, porosity location can consistently be located in non-critical areas of the casting.  The result is consistent quality throughout the die casting process. 

 

This control over the thermal aspect of the die casting process has numerous benefits to many aspects of the process.