Page 39 - Demo

37GENERAL DRILLING HANDBOOKPressure Vs. FlowThe main heat formation is around the cutting edge of the drill. To remove heat efficiently it is necessary to flow coolant at high speed as close as possible to the cutting area.The flow velocity in a channel can be defined by: v = Q A Where:v = Flow velocityQ = Volumetric flow rateA = Cross section of coolant channelBased on the formula it can be concluded that there is a direct relationship between volumetric flow rate and flow velocity and the higher the volumetric flow rate, the higher the flow speed.Another conclusion that can be drawn is that the larger the diameter of the drill used, the higher the heat generation (and MRR) and we will need a higher coolant volumetric flow rate.QDcWhere:Q = Volumetric flow rateDc = Drill diameterFor a certain tool, there is a relationship between volumetric flow rate and pressure that can be defined by:P=k%u00d7Q2Where:P = Pressurek = Hydraulic resistance of the toolQ = Volumetric flow rateThe higher the coolant pressure provided at the inlet of the drill, the higher the coolant flow through the drill and vice versa to transfer higher flow through the drill, it is necessary to increase the pressure at the inlet to the drill.In cooling systems there is a limit to the pressure that can be generated in the system, as soon as the pressure of the liquid is higher than what the system defines a pressure discharge valve will open, and this will be reflected in a limitation of the flow rate. The aim is to supply liquid with maximum flow and for this purpose it is necessary that the pressure in the system will not exceed the upper limit defined in the cooling system.