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1. Application of milling cutter

Milling for a variety of cutting methods in a larger, more versatile cutting. Therefore, whether it is a slot, a concave cut, a flat surface or even a variety of modeling surfaces can be processed, and a better and accurate size of surface brightness can be obtained through milling. Milling cutter is a round cutting tool with multiple cutting edges. The principle of milling is to use the rotation of multiple cutting edges of the milling cutter to produce cutting effect. Therefore, although the cutting tool cuts deeply into the workpiece, the cutting amount of each cutting edge is not large. Therefore, the cutting thickness of each cutting edge can still be kept very thin, the resulting machining surface is also good, and the tool life can be maintained very long. Good cutting efficiency, a wide range of uses, so the milling cutter in the current metal processing occupies a very high component.

As the milling cutter can almost replace most of the traditional cutting tools in the current cutting process, no matter in the material, shape, structure of the milling cutter... And so on the design and manufacture, not only a very wide variety and complex. Now only the following types of milling cutters commonly used in general mold milling are described.

2. Types of milling cutters

In mold milling, because the mold itself is a complex shape of the workpiece, in consideration of cutting efficiency, tool life and workpiece shape... Under such factors, it is impossible to use only a single shape of milling cutter to complete the mold. Therefore, milling cutters of different shapes are often used in mold processing. Generally, there are three types of milling cutters commonly used in mold processing: A, end milling cutter; B. ball cutter; C. round nose cutter.

Features of 2.1 end mill

When milling a 2D shaped workpiece, since the region in contact with the workpiece is the outer edge and the bottom surface, it is possible to use extremely efficient numerical values for both the tool pitch and the cutting depth. On the other hand, if the mold is used for milling 3D shapes, you can find that the area in contact with the workpiece is almost always near the sharp point, so you have to reduce the tool spacing or cutting depth, so the processing efficiency is reduced.

The shape of the end mill is shown in the right figure. The milling cutter has milling teeth on the outer edge and the bottom surface to form the cutting edge, so it can be used to mill the vertical plane and the vertical plane of the workpiece. The shape of the end mill is very complex and is suitable for all kinds of machining, such as milling planes, grooves or contour surfaces... And so on, can be said to be used more widely a milling cutter. Generally speaking, end mills are very suitable for 2D shaped workpieces, but they are not so applicable when applied to 3D shaped molds. We explain the problems that occur when end mills are applied to mold processing for the following reasons:

1. the area indicated in the box below, you can see that there is a sharp dot here. So it's very fragile, and once the cusp here collapses, the life of the milling cutter is over. So the life of the end mill is not very stable.

Therefore, in mold processing, end mills are generally used to process 2D areas in the mold, such as vertical and horizontal planes or sharp corners in the mold. In the traditional way of mold processing, end mills will also be used for roughing. The following icons are examples of actual machining of an end mill.

2.2 ball knife

As shown in the figure below, the milling cutter with a ball shape at the bottom is a ball cutter. Ball cutters are used quite frequently in the current mold processing, especially when milling 3D molds, ball cutters are indispensable tools.

Compared with the former-end mill, because the ball cutter does not have a sharp edge like the end mill at the bottom, but a blade with an R angle, the blade of the ball cutter is stronger and not easy to collapse. In other words, the life of the ball cutter will be more stable than the end mill. In addition, the ball cutter and the workpiece contact area for the R angle of the blade, so in the finishing knife spacing can be used more numerical, the processing surface also has excellent effect.

Therefore, whether it is tool life or processing efficiency, ball knife is a good choice in mold processing! But the same, the ball knife in the mold processing will also encounter some problems. When milling 3D mold ball cutter and the workpiece contact area is the R angle of the blade, but the actual contact position will change with the shape of the workpiece, this difference will bring the following effects:

2.2.1 Cutting speed

The more basic concept of cutting is to give the cutting edge and the relative speed of the material being cut. When the material of the cutting edge is harder than the material being cut and the cutting speed is reached, the area where the material being cut contacts the edge will be removed. Therefore, the cutting speed is very important for the cutting effect of the tool. If the cutting speed is not enough or too low, the cutting edge is not cutting the workpiece, but grinding the workpiece. In order to produce cutting speed, so in turning is rotating the workpiece to produce cutting speed; in milling is rotating the tool to produce cutting speed. The ball knife as shown in the figure below,

When rotating, 1, 2, 3 points of the position of the corresponding cutting speed are not the same, even 2 this point of the cutting speed is almost equal to 0. Therefore, the disadvantage of the ball knife is that the cutting speed is not stable. In the following example,

You can see that when the ball cutter is milling a 3D workpiece, the position of the blade in contact with the workpiece will constantly change, so the cutting speed is always changing. The cutting speed is stable at points a and c, so this area is where the blade is cutting the workpiece and a good machined surface can be obtained. However, at points B and D, the cutting speed is too low or even no cutting speed will cause the cutting edge to rub the workpiece, and the quality of the machined surface will of course be greatly affected.

2.2.2 Tool loss

When the ball cutter is milling a relatively flat area, it is as follows: at this time, most of the positions in contact with the workpiece are a, B, and c. So the bottom of the ball cutter is actually used in milling the workpiece. When the whole area of the workpiece is very large, in addition to the low cutting speed at the bottom of the ball cutter, the blade at the bottom will wear quickly, and the blades on both sides are not used, so the machining surface is not only low in quality but also because of the relationship between tool loss, the accuracy of the machining surface will also be affected.

Ball cutters are more commonly used for milling in mold processing.

Ball cutters are more commonly used for milling 3D molds in mold processing, especially in finishing and angle cleaning, but they are not suitable for milling flat areas, because the contact area with the workpiece is small, and the cutter spacing cannot be increased. The following icons are examples of actual machining of ball cutters.