The study aims to enhance the machining accuracy and reduce the energy consumption of a computer numerical control (CNC) machine. A multiobject cooling control system was devised that can effectively remove the generated heat of two operational spindles in parallel arrangement by employing a varied coolant volume control method. In the multiobject cooling system, the openings of the two-way valves in front of the spindles under different spindle rotating speeds could be adjusted to maintain a constant coolant temperature difference of 3.5 °C ± 0.1 °C between the inlet and the outlet of the spindles. Due to the adjustable openings of the two-way valves, the coolant pressure between the supplied coolant and return ports in the primary loop is variable. A regression equation was established for the supplied coolant volume control in terms of the coolant pressure difference in the primary coolant loop and the driving frequency of the coolant pump for different spindle cooling loads. By adjusting the driving frequency of the coolant pump in terms of the regression equation, the supplied coolant volume can be controlled with the cooling load variations under different rotating speeds of the spindles and the energy consumption of the coolant pump can be greatly reduced as well. In comparison to the traditional case of two spindles with two individual coolers using the constant coolant volume control method, the initial investment in cooling systems could be greatly reduced by the varied coolant volume control of the multiobject cooling system. The accuracy of the spindles could be improved by 5.5 to 41.7%, and the operational power consumption could be reduced by 11 to 34%, while the rotating speed of one spindle varies from 10,000 ~ 22,000 rpm, and the other spindle is 10,000 rpm. The total lifetime carbon emissions can be reduced from 72,981 to 52,595.5 kg under different spindle rotating speeds, and the initial capital cost can be reduced from 8832 to 4729 USD. By using the multiobject cooling system for the two-spindle system, the initial capital cost can be reduced by 46.5%.
Relation:
The International Journal of Advanced Manufacturing 126, p.1807-1825
