Wet Coolant
Common names for the liquid used to cool and lubricate the tool/workpiece contact while milling include cooling mixture, cutting lubricant, cutting fluid, and coolant. All cutting causes unwanted friction to develop there. Coolant guarantees that there is less friction between the two surfaces, and lubrication greatly improves the metal removal procedure. The material of the workpiece, the cutting data, and the substrate of the cutting tool are only a few examples of variables that might affect the temperature in the cutting zone during machining. For instance, it is projected that a tungsten-carbide tool will reach a temperature of 1,100° to 1,200° C (2,012° to 2,192° F) at the point where the cutting edge makes contact with the workpiece.
The introduction of coolant decreases the temperature in the cutting zone and lessens the tool’s thermal burden. Additionally, coolant enhances chip evacuation and lowers metal dust concentration. Consequently, a number of significant advantages are directly related to the coolant supply. Because of the significant temperature variations that occur as the cutting edge enters and leaves the cut during interrupted milling, the cutting edge of the tool is subjected to a cyclic thermal load. As a result, the cutting edge of a tool is exposed to extreme heat stress, which is equivalent to repetitive thermal sʜᴏᴄᴋ.
Cutting edges are ᴅᴇsᴛʀᴏʏed by thermal sʜᴏᴄᴋ loads, which are sensitive to cemented carbide, a sintered, powder-metallurgy product. Coolant use when using a carbide tool may exacerbate the “sʜᴏᴄᴋ treatment” and unintentionally cause cutting-edge failure. Extreme temperatures cause the cutting edge to distort plastically, while a variation in temperature causes thermal fractures. When high heat is present, as when milling materials that are challenging to cut, this is even more pronounced. Even though wet machining has many advantages, milling may definitely be a challenge with it.
Dry Machining
When making light cuts during high-speed machining, cooling by air is strongly advised, especially for workpieces with a hardness of 45 HRC or above. In this case, the absence of moist coolant will significantly lengthen tool life. The cost of cooling and workplace safety is further crucial considerations. The portion related to liquid coolants, such as purchasing, maintenance, and filtration, can range from 16 to 17 percent if cutting tool investment in batch production is considered at 3 percent of the entire part cost. A coolant pump, a coolant recycling system, and other pricey machine tool attachments are not required without cutting fluid, which further lowers overall costs.
When using MQL for near-dry milling, the cutting edge of the tool operates in a mist created by compressed air and oil that is sprayed directly into the cutting zone. The mist is provided externally or internally through the milling cutter, depending on the design of the machine tool. MQL’s primary purpose is to lubricate the cutting edge. Because only the appropriate amount of oil is used during the machining process, lubrication is more effective.
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