Knowledge about milling cutters

To understand milling cutters, we must first understand milling knowledge.

The blade of the milling cutter is another important factor in optimizing the milling effect. It is advantageous to have more than one blade at the same time in any one milling process, but too many blades at the same time are disadvantageous. It is impossible for each cutting edge to be cut at the same time, and the required power and the number of blades to be cut at the same time are required. The position of the milling cutter relative to the workpiece plays an important role in chip formation, cutting edge load and machining results. In face milling, with a milling cutter about 30% larger than the cutting width and positioning the cutter close to the center of the workpiece, the chip thickness changes little. The chip thickness cut in is slightly thinner than that in the center cutting.

In order to ensure that a sufficiently high average chip thickness/feed per tooth is used, the number of teeth of the milling cutter suitable for the process must be determined correctly. The distance between the teeth of the milling cutter is the distance between the effective cutting edges. According to this value, the milling cutter can be divided into 3 types -- dense tooth milling cutter, sparse tooth milling cutter and special dense tooth milling cutter.

The main deflection angle of the face milling cutter is the angle between the main cutting edge of the blade and the surface of the workpiece. There are mainly 45 degrees, 90 degrees and circular blades. The direction of the cutting force changes greatly with the main deflection angle: the main deflection angle of the 90 degree milling cutter produces radial force. Used in the feed direction, this means that the machined surface will not withstand excessive pressure and is more reliable for milling weaker structures.

The radial cutting force and axial force of the 45-degree main deviation milling cutter are approximately equal, so the pressure produced is more balanced, and the power requirement of the machine tool is relatively low. It is especially suitable for milling the short chip material workpiece which produces chips.

The milling cutter with a circular blade means that the main deflection angle varies continuously from 0 to 90 degrees, depending on the cutting depth. This kind of blade has very high cutting edge strength, because the chip produced along the direction of the long cutting edge is thin, so it is suitable for large feed, along the direction of the radial cutting force of the blade is constantly changing, and the pressure generated in the process of machining will depend on the cutting depth. The development of modern blade geometric groove makes the circular blade have the advantages of stable cutting effect, low power demand for machine tools and good stability. Today, it is no longer an effective rough milling cutter. It is widely used in face milling and vertical milling.

Milling method


There are two ways relative to the feed direction of the workpiece and the rotation direction of the milling cutter.

Milling and reverse milling

The first one is downmilling. The rotation direction of the milling cutter is the same as the feed direction of the cutting. At the beginning of the cutting, the milling cutter bites the workpiece and cuts off the final chip.

The second kind is reverse milling. The rotation direction of the milling cutter is opposite to the cutting direction. The milling cutter must slip a section on the workpiece before starting cutting. The cutting thickness begins at zero and reaches the maximum at the end of cutting.

In three side milling cutters, some vertical milling or face milling, the cutting force has different directions. In face milling, the milling cutter is just outside the workpiece, and the direction of cutting force should be paid more attention. When milling, the cutting force will press the workpiece to the worktable, and the cutting force will cause the workpiece to leave the worktable.

Because of the best cutting effect, the forward milling is usually preferred. The reverse milling is considered only when the machine tool has the problem of thread clearance or the problem can not be solved by the forward milling.

Ideally, the diameter of the cutter should be larger than the width of the workpiece, and the center line of the cutter should always be slightly away from the center line of the workpiece. Burrs are prone to burrs when cutting tools are placed in the cutting center. The direction of the radial cutting force changes as the cutting edge enters and exits the cutting. The spindle of the machine tool may vibrate and damage. The blade may fragment and the machined surface will be very rough. The milling cutter will deviate from the center slightly, and the direction of the cutting force will no longer fluctuate. The milling cutter will get a preload. We can drive the center milling ratio into the center of the road.

Each time the milling insert enters the cutting process, the cutting edge must bear the impact load, which depends on the chip cross-section, workpiece material and cutting type. When cutting out, it is an important direction to correctly bite between the cutting edge and workpiece.