The most commonly used tool for contour milling is the end mill. The following mainly describes the selection of the size of the milling cutter and the number of teeth.
(1) Dimensions of end mills
In contour milling, the factors that need to be considered for the end mill include: the diameter of the end mill, the length of the end mill, and the length of the spiral groove.
The diameter of the end mill is used first. Because the tool with a large diameter has high bending strength, it is not easy to cause bending and vibration during processing, but pay attention to the tool radius of the end mill must be smaller than the minimum radius of curvature of the part contour, generally Take 0.8~0.9 times of the minimum curvature radius. In addition, the protruding length of the tool should be as short as possible. The longer the length of the end mill, the lower the bending strength and the greater the degree of bending under force, which will affect the quality of processing, and is prone to vibration and wear of the cutting edge.
Regardless of the overall tool length, the helical flute length determines the maximum depth of cut. In practical applications, the cutting attempt in the z direction generally does not exceed the radius of the tool; for end mills with a smaller diameter, 1/3 of the diameter of the tool is generally selected as the cutting depth.
(2) also the number of teeth
Small or medium diameter milling cutters, usually with 2 or 3 co-located teeth (or more). The type of workpiece material to be machined and the nature of the machining are often the determining factors in selecting the number of teeth.
In the processing of workpiece materials with high plasticity, such as aluminum and magnesium, in order to avoid the generation of built-up edge, end mills with few teeth are commonly used, such as two-tooth (C spiral groove) production milling cutters. End mills have fewer teeth to avoid built-up edge when the cut is larger because of the larger chip space between the helical flutes.
The opposite is true for harder materials, as he needs to consider two other factors – tool chatter and tool offset. When machining brittle materials, choosing a multi-tooth end mill will reduce tool chatter and deflection, as more teeth provide a smoother cut.
For small or medium diameter end mills, three-tooth end mills have the advantages of two-tooth and four-tooth tools, and have good processing performance. Keyway milling cutters usually have two helical grooves, which are similar to drills and are cut vertically into solid material.
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