Selection of milling cutters and milling methods for milling machines

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

The first is down milling, the rotation direction of the milling cutter is the same as the feed direction of the cutting, the milling cutter bites the workpiece and cuts off the last chip at the beginning of cutting.

The second is reverse milling, the rotation direction of the milling cutter is opposite to the feed direction of the cutting, the milling cutter must slide on the workpiece for a period before starting cutting, starting with a cutting thickness of zero, and the cutting thickness reaches the maximum at the end of cutting.

In three-face milling cutters, some end 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 the cutting force should be paid special attention to. In down milling, the cutting force presses the workpiece to the worktable, and in reverse milling, the cutting force makes the workpiece leave the worktable.

Since down milling has the best cutting effect, down milling is usually preferred. Reverse milling is only considered when the machine tool has thread clearance problems or problems that down milling cannot solve.

Ideally, the cutter diameter should be larger than the workpiece width, and the cutter axis should always be slightly away from the workpiece centerline. When the cutter is placed directly opposite the cutting center, burrs are very likely to occur. Metalworking WeChat. The direction of the radial cutting force will change constantly when the cutting edge enters and exits the cutting, the machine tool spindle may vibrate and be damaged, the blade may break and the machined surface will be very rough, the milling cutter is slightly off center, and the direction of the cutting force will no longer fluctuate - the milling cutter will obtain a preload. We can compare center milling to driving in the center of the road.

Every time the milling cutter blade enters the cutting, the cutting edge is subject to an impact load, the load size depends on the cross-section of the chip, the workpiece material and the type of cutting. Whether the cutting edge and the workpiece can bite correctly when cutting in and out is an important direction.

When the cutter axis is completely outside the width of the workpiece, the impact force during cutting is borne by the outermost tip of the blade, which means that the initial impact load is borne by the most sensitive part of the tool. The milling cutter finally leaves the workpiece with the tip, that is, the cutting force acts on the outermost tip from the beginning of cutting to the end of cutting, until the impact force is unloaded. Metalworking WeChat When the center line of the milling cutter is exactly on the edge line of the workpiece, the blade leaves the cutting when the chip thickness reaches the maximum, and the impact load reaches the maximum when cutting in and out. When the axis of the milling cutter is within the width of the workpiece, the initial impact load when cutting in is borne along the cutting edge by the part far away from the most sensitive tip, and the blade exits the cutting relatively smoothly when retracting.

For each blade, the way the cutting edge leaves the workpiece when it is about to exit the cutting is important. The remaining material near the time of retraction may reduce the blade clearance to some extent. When the chip leaves the workpiece, an instantaneous tensile force will be generated along the front face of the blade and burrs will often be generated on the workpiece. This tensile force endangers the safety of the chip edge in dangerous situations.