At the start of this year's world-leading trade fair for metal machining EMO in Hannover, Walter AG, together with the machine tool manufacturer Starrag AG, have won the MM Award for Innovation for the most innovative exhibit in the category "milling": The production-scale machining of turbine blades with CO2-based cryogenic cooling.
The outstanding feature of the approach developed by Walter and Starrag is the liquid supply of CO2 coolant through machine, spindle, toolholder and tool, right to the cutting edge – all without loss of pressure and therefore at room temperature. Cooling to a maximum of minus 73 °C first occurs at the nozzle, when the CO2, which has been in liquid form until that point, expands. Therefore, users can machine up to 70 % faster in comparison to dry machining. Conversely, the cryogenic CO2 cooling doubles the tool life, as long as the cutting parameters are not increased.
The developers at Walter and Starrag have, however, refined their solution even further: A second media channel supplements the CO2 cooling. This channel can be used for aerosol or minimum quantity lubrication (MQL), for example for milling high-strength alloys for extremely heat-resistant turbine blades.