After selecting the appropriate grinding fluid and its management system, the next priority is how to correctly inject the grinding fluid into the grinding area. The grinding fluid should be injected into the cutting arc area, rather than simply into the joint between the workpiece and the grinding wheel. Generally, only a small part of the poured coolant enters the cutting arc area. The rotating grinding wheel acts like a blower to throw the grinding fluid out of the outer circle of the grinding wheel.
The hole of the grinding wheel can not only hold chips, but also carry grinding fluid. In this way, the grinding fluid is brought to the cutting arc area by the grinding wheel itself. Therefore, at an appropriate speed, the grinding fluid poured into the outer circle of the grinding wheel will be brought to the cutting arc. In addition, the nozzle shall be specially designed so that the grinding fluid can be injected at the correct injection point at a proper speed. The nozzle size shall cover the whole width of the grinding wheel.
When the width is known, the opening height (d) of the nozzle can be calculated. If the nozzle width is 1.5”, the nozzle area is 1.5din2. If the grinding speed is 5500 (1676m/min), it must be multiplied by 12 to get 66000 in/min. Therefore, the flow rate of grinding fluid at the nozzle is: (1.5din2) × 66000in/min=99000din3/min. If the oil pump pressure is 110psi (0.758MPa), the liquid flow per minute is 58gpm (58 gallons per minute, about 219.554 liters/minute), and 1 gallon=231 cubic inches), so the oil pump flow is 231in3 × 58gpm=13398in3/min.
Obviously, the flow at the inlet and outlet of the oil pump should be equal, that is, 13398 should be equal to 99000d. The nozzle height d can be calculated as 0.135” (13398/99000). The actual nozzle opening height can be slightly smaller than the calculated value, because the speed of grinding fluid will be reduced after leaving the nozzle. When the nozzle is not facing the grinding wheel, it is particularly important to consider this factor. Therefore, the nozzle size in this example is 0.12 "×1.5” is better.
The pressure of the oil pump is to push the liquid to flow in the pipeline system. Sometimes the resistance of the system may exceed the rated pressure of the oil pump by 110Psi, because the nozzle is often manufactured incorrectly, and the pipelines, joints, movable rotating arms, etc. are twisted or blocked.
Post time: Feb-13-2023