The up milling is safer and most commonly used despite its disadvantages. Whereas in the down, it starts removing metal immediately it reaches the job, the material is removed without sliding. In up, the cutter doesn’t begin cutting as soon as it touches the job and hence the surface appears wavy after milling. Whereas in the down, the chip disposal is automatic and does not interface in cutting. In up, the chip accumulates at the cutting zone and interferes with cutting, spoiling the surface. But in down, the coolant can easily reach the cutting edge. The up milling is difficult for efficient cooling. But in the down, The force of cutting is directed downwards and keeps the job pressed against the table. In up, The force of cutting tends to lift up the work since it is directed upwards. Whereas in the down, the cutting force varies as a maximum at the beginning and minimum at the end. In up, cutting forces vary from a minimum at the beginning to a maximum at the end. Whereas in the down, the cutting forces vary as a maximum at the beginning and a minimum at the end. In up, the thickness of the chip is minimum at the beginning of the cut and it reaches to maximum when the cutting ends. Whereas in the down, the direction of the cutter rotation coincides with the feed direction. In up, the direction of the cutter rotation is opposite to that of work done. Read Also: 22 Types of Lathe Machine Operations Difference Between Up Milling and Down Milling The maximum chip load is related to the specified feed per tooth in both situations.For similar conditions, the total volume of the workpiece material removed on the up milling side must match the total volume of the workpiece material removed on the down milling side.In both situations, the same milling cutter can be used, but the orientation may vary.When performing a full immersion end-milling operation (slot cutting), each rotation for each tooth involves both up-milling and down-milling happening one after the other.No matter whether it is up milling or down milling, the machining process requires three process parameters: speed, feed, and depth of cut.Similarities Between Up Milling and Down Milling The following sections provide a table with various up- and down-milling similarities and differences. The sea action is repeated as soon as the next tooth engages the work. The backlash error causes the work to be pulled below the cutter when the cut begins and leaves the work free when the cut is terminated. This operation has so many advantages that cannot be used on old machines due to the backlash error that may be present between the feed screw of the table and the nut. This results in an improved surface finish and diminishes the heat generated. The coolant can be applied directly to the cutting area where the cutting force is maximum. The chips are also disposed of easily and do not interfere with the cutting. In this process, the fixture design becomes more accessible as the direction of the cutting force is such that it tends to seat the work firmly in the work holding devices. The cutting force in this operation is also variable throughout the cut, it is maximum when the tooth begins its cut, and it reduces to the minimum when the tooth leaves the work. The cutter tooth starts removing metal immediately on reaching the work surface, without slipping as it can apply a sufficient cut on the work. The thickness of the chip is maximum when the tooth starts its cutting, and when the cut is finished, it becomes minimal. It is the process of removing metal by a cutter which is rotated in the same direction by a cutter which is the workpiece rotated in the same direction of travel. It is the process that is also called climb milling. Read Also: What are the types of lathe machine? Down Milling The process is safer, and is still commonly used despite having so many disadvantages. The teeth slide through a minute distance at the beginning and then cut is started. The surface milled by up milling appears to be slightly curved the cutter teeth do not begin their cut as soon as they touch the work surface. The surface, milled by this operation, appears to be slightly curved as the cutter spoils the work surface. As the cutter progresses, the chip expands the cutting zone and may carry over with the cutter spoiling the work surface. In this process, due to the typical nature of the cut, the difficulty is experienced in pouring coolant just on the cutting edge from where the chip begins. The cutting force is directed upwards, which tends to lift the work from the fixtures. As the chip thickness per tooth is not uniform, the cutting in this operation increases from zero to the maximum value per tooth movement of the cutter. The thickness of the chip in this process is minimum at the beginning of the cut, and it reaches the maximum when the cut ends.
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