One, milling tool
There are many kinds of milling cutters (most of which have been standardized), and the cutters can be divided into two types: sharp-toothed cutters and shovel-toothed cutters. The back teeth of the tine milling cutter are milled and the flank surface is a simple plane, as shown in Fig. 8-13a. The tool is widely used. The milling cutters for machining planes and grooves are generally designed as sharp teeth. The main difference between shovel cutters and tip cutters is the special flank shape that is made by shoveling, as shown in Fig. 8-13b, and the front rake face is bluntly grinded. The scooped flank ensures that the milling cutter does not change its profile throughout its use. The use of milling cutters is described below. Figure 8-13 Teeth form
(A) milling cutter for machining plane
Cylindrical milling cutters are generally used to machine narrower flats on a horizontal milling machine using a circumferential milling method. Figure 8-14 shows the geometry of its working part. In order to facilitate manufacturing, the cutting edge rake angle is usually specified in the normal plane, denoted by Î³n; for measurement and sharpening, the following angle is specified in the orthogonal plane, denoted by Î±0; the helix angle is its edge angle and Î»s Its leading angle is kr=90?. There are two types of cylindrical milling cutters: cylindrical cutters with coarse teeth have features such as fewer teeth, high cutter tooth strength, large chip space, and more re-grinding times, and are suitable for rough machining; the cylindrical teeth of fine-tooth cylindrical cutters have many teeth, Smooth work, suitable for finishing.
2. Face milling cutter
High-speed steel face milling cutters are generally used to machine medium-width planes. The standard cutter diameter range is 80-250mm. The cutting efficiency and machining quality of carbide face milling cutters are higher than those of high-speed steel cutters. Therefore, hard alloy face milling cutters are widely used to machine the plane.
Figure 8-15 shows the overall welded face milling cutter. The knife is compact and easy to manufacture. However, the whole knife will be scrapped after the cutter tooth wears, so it has been less used.
Figure 8-16 is a machine-welding face milling cutter. The milling cutter is to weld the carbide blade to the small cutter head, and then the cutter is clamped in the cutter body groove by means of mechanical clamping. After the cutter head is scrapped, it can be replaced with a new cutter head, thus extending the service life of the cutter body.
Figure 8-17 shows an indexable face milling cutter. The milling cutter clamps the insert directly into the body groove. After the cutting edge is blunt, the blade can be indexed or replaced for continued use. The indexable milling cutter has the same advantages as an indexable turning tool, high efficiency, long service life, convenient use, stable processing quality, and the like. This type of milling cutter is one of the most widely used tools in planar machining. The indexable face milling cutter has formed a series of standards and can be consulted for relevant information such as tool standards.
(b) Milling cutters for machining grooves
1. Three-edge cutter
In addition to the main cutting edge on the circumferential surface, the three-edge milling cutter also has secondary cutting edges on both sides, thereby improving the cutting conditions, improving the cutting efficiency and reducing the surface roughness. Mainly used for machining grooves and step surfaces. The cutter structure of the three-edge cutter can be divided into three types: straight tooth, wrong tooth and insert tooth.
Figure 8-18a shows a straight-tooth three-blade cutter. The knife is easy to manufacture and easy to sharpen. However, the side blade rake angle Î³0=0?, and the cutting conditions are poor.
Figure 8-18b is a three-edge tooth cutter with a wrong tooth. The knife's teeth staggered to the left and right tilt helix angle Ï‰. Each cutter has only one auxiliary cutting edge at one end, and the positive rake angle of the minor cutting edge is formed by the Ï‰ angle, and the Ï‰ angle makes the cutting process smooth and easy to remove chips, thereby improving the cutting conditions. The overall misaligned cutter will reduce its width after heavy grinding.
Fig. 8-18c is a three-edge insert milling cutter, which can overcome the defect that the thickness of the integral three-face milling cutter becomes smaller after sharpening. The teeth are set in the toothed groove. When the number of teeth of the knife is Z, the number of teeth Z1 in the same direction is Z=Z/2, and the pitch of adjacent tooth grooves inclined in the same direction is shifted by P/Z1 (P is the pitch of the teeth). When the width of the cutter is reduced after re-grinding, the cutter teeth with the same inclination can be taken out and moved into the adjacent co-directional tooth slots sequentially. The width of the adjusted cutter is increased by P/Z1, and then it is restored by sharpening. The original width.Saw blade cutter
Figure 8-19 is a slotted slot cutter for cutting or cutting.
End mills are mainly used to machine grooves and step surfaces on vertical milling machines, and they can also be used to machine forming surfaces. As shown in Figure 8-20, the cutting edge on the circumference of the end mill is the main cutting edge, and the cutting edge on the end face is the secondary cutting edge, so it is generally not advisable to feed in the direction of the milling cutter axis during cutting. In order to increase the strength of the secondary cutting edge, the edge should be ground on the front edge.
4 wave edge milling cutter
Figure 8-21 shows a wave-edged end mill. It is based on the spiral rake face of ordinary high-speed steel end mills, using a special milling fixture to re-spin the spiral rake face into a wavy spiral face, which intersects with the flank face to form a wave-shaped cutting edge. The peaks and valleys of two adjacent wave-shaped edges are shifted by a certain distance along the axis, so that the cutting width is significantly reduced, and the actual cutting thickness of the cutting edge is increased by approximately three times. The cut chips are narrow and thick, which reduces the degree of cutting deformation and makes The cutting edge cuts into the workpiece while avoiding the surface hardening layer. The edge of the wave makes the cutting edge inclination, the working front angle and the cutting load assumed by the cutting edge different. In addition, the pitch of the waveform in the same end section is also different. These factors greatly reduce the periodicity of cutting force changes and make the cutting process more stable. Milling of workpieces with rough surfaces, such as gas cutting steel plates, and wave-blade end mills, in particular, show excellent cutting performance.
5. Keyway milling cutterFigure 8-22 shows a keyway cutter for machining round closed keyways. The milling cutter resembles an end milling cutter, the end mill has three or more cutting teeth, and the keyway milling cutter only has two cutting teeth. The end milling cutting edge is the main cutting edge and the strength is higher; the circumferential cutting edge is the auxiliary. Cutting edge. According to the national standard, the diameter of the straight shank keyway cutter is d=2mm~22mm, and the diameter of the milling cutter of the taper shank keyway is d=14mm~50mm. Keyway cutters have two types of accuracy, eB and dB, and typically process H9 and N9 keyways, respectively. During processing, the keyway milling cutter feeds along the tool axis, so wear occurs only near the end face. Regrind just need to sharpen the end face edge, so after the re-grinding tool diameter unchanged, high precision machining.
(III) Milling cutters for forming surfaces
1. Forming cutter
Forming Milling Cutter is a special forming tool designed according to the shape of the forming surface of the workpiece. It has two types of sharp teeth and shovel teeth, as shown in Fig. 8-23. The former is similar to general tip milling cutters, and the flank of the blunt rear grind cutter teeth has a higher durability and a higher surface quality. However, because the back flank is also a forming surface, it is difficult to manufacture and sharpen. The latter tooth back (back flank) is scooped according to a certain curve, and it is more convenient to re-grind the rake face (planar) after blunt. Therefore, when the forming surface is milled, a spatula cutter is often used.
The key to designing and using a form milling cutter is that after each regrind, the shape of the cutting edge of the cutter teeth is required to be constant and have an appropriate back angle, and the workability is good, and the manufacturing and sharpening are simple. In order to meet these requirements, the scraper profile cutter is often made with a side rake angle Î³f=0? (the rake face is then in the axial plane of the cutter), and the flank of the cutter cutter should be a cutter cut. The surface of the milling cutter is uniformly formed along the radial direction of the cutter while rotating around its axis. The flank faces of the tooth profile forming cutters adopt the Archimedean spiral surface, and the flat body turning tool with Î³f=0? (the blade shape is the same as that of the Î³f=0?cutter, but the convex and concave shapes are reversed), The scraper tooth is made on the shovel lathe.
2. Mould cutter
Die cutters are used to machine die cavities or punch forming surfaces. The die cutter is evolved from an end mill, as shown in Figure 8-24. According to the shape of the working part can be divided into conical flat head, cylindrical ball head, conical ball head three. Carbide die cutters are used for a wide range of applications. In addition to milling a variety of die cavities, they can also replace burrs for casting, forging, and welding workpieces with burrs and grinding wheels, and perform finishing on certain forming surfaces. Wait. The milling cutter can be used on pneumatic or electric tools, and its production efficiency and durability are increased by several ten times compared with grinding wheels and boring tools.
Second, milling machine fixture
Commonly used clamping methods for milling
Milling is a common method of machining planes, keyways, gears, and various forming surfaces. When machining workpieces on a milling machine, the following mounting methods are generally used:
(1) Directly clamped on the milling machine work bench Large workpieces are often mounted directly on the workbench and pressed with studs and pressure plates. This method requires the use of dial gauges, stylus and other tools to align the working surface and the milling cutter. The relative position is shown in Figure 8-25a.
(2) Using a machine tool with a flat vise to clamp the workpiece For small and medium-sized workpieces with a simple shape, they can generally be clamped in a flat vise for the machine tool, as shown in Fig. 8-25b. The use of the vise must be ensured in the machine tool. The correct location.
(3) As shown in Fig. 8-25c, the workpiece is clamped with a dividing head. For workpieces that need to be indexed, they can generally be clamped directly on the indexing head. In addition, it is also very convenient to use a dividing head for processing without indexing the workpiece.
(4) The method of clamping workpieces with V-shaped brackets is generally applicable to shaft-type parts. In addition to having good alignment, it can also withstand greater cutting forces, as shown in Figure 8-25d.
(5) The special fixture for clamping workpieces with a special fixture has the advantages of accurate positioning, convenient clamping, and high efficiency. It is generally applicable to batch and mass production.
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