When machining workpieces on a milling machine, we often use reverse milling and milling two methods.When the feed direction of the workpiece is opposite to the cutting speed of the cylindrical milling cutter, it is called reverse milling. When the feed direction of the workpiece is the same as the cutting speed of the cylindrical milling cutter, it is called milling.
Milling is conducive to improving the durability of the tool and the stability of the workpiece clamping, but easy to cause the table to move, and even cause accidents. Therefore, the milling machine should have a means to eliminate the gap between the screw and the nut, and the milling range should be limited to the non-crusty workpiece. In the fine processing, the milling force is small, difficult to cause the table of the channeling, and more use of milling. Because the milling does not slip phenomenon, the surface quality after processing is better.
When milling, the milling cutter always has a downward force to compress the workpiece, making the milling smooth. The cutting thickness of each knife is reduced from the maximum to zero, easy to cut into the workpiece, and cut out when the working surface of the extrusion friction is also small, slower blade wear, processing surface quality is higher. The power consumed in the direction of the feed movement is small. The cutting edge is cut from the outer surface of the workpiece, and the blade is easy to wear and damage when the workpiece is crusty with crust and impurities. Milling cutter on the workpiece's horizontal component and feed the same direction, it will pull the table, when the screw and nut, bearing the axial clearance is large, the table is pulled will make the cutter per tooth feed suddenly increased Large, causing the teeth to break, knife shaft bending, workpiece and fixture movement, and even damage the milling machine.
Reverse milling is used for roughing, processing of crusty castings, forging blanks and so on. In the case of milling machines without screw nut adjustment mechanism, reverse milling should also be used. In the case of reverse milling, since the cutting edge is not cut from the outer surface of the workpiece, the workpiece has a hard skin on the milling surface and has little effect on the damage to the blade. However, the cutting thickness of each blade is increased from zero to the maximum, As the edge of the knife teeth always have a certain arc, so the knife teeth contact the workpiece after a distance to cut the workpiece, the blade easy to wear, and the machined surface by the extrusion and friction, affecting the quality of the surface processing.
When reverse milling, the horizontal component and the workpiece feed the opposite direction, will not pull the table, screw and nut, the bearing is always kept in close contact without loosening, but reverse milling will produce upward vertical force, so that the workpiece has a rising trend.Therefore, must make the workpiece clamp firmly, and the vertical component in the cutting process is changing, easy to produce vibration, affecting the workpiece surface roughness. In the reverse direction, the power consumed in the feed direction is large.
Understand the milling machine two different milling methods, select the appropriate milling method, in order to achieve the best processing results.