First, the structure of the turning tool
The machine clamp indexable turning tool is a turning tool formed by mechanically clamping an indexable cemented carbide insert on a cutter bar, generally consisting of a blade, a knife pad, a clamping component and a cutter body (see Fig. 1). . According to the different clamping structure, it can be divided into the following forms.
The eccentric clamping structure clamps the blade on the arbor by an eccentric mandrel at the upper end of the screw. The structure relies on eccentric clamping, the screw is self-locking, the structure is simple, and the operation is convenient, but it cannot be bilaterally positioned. When the eccentricity is too small, the precision of the blade manufacturing is required to be high. If the eccentricity is too large, the blade is easy to loose under the action of the cutting force, so the eccentric clamping structure is suitable for continuous and smooth cutting.
The lever clamping structure applies the lever principle to clamp the blade. When the screw is turned, the clamping force is generated by the lever, so that the blade is positioned on the side of the sipe. When the screw is unscrewed, the blade is loosened, and the semi-cylindrical spring piece keeps the position of the blade. The structural features are high positioning accuracy, firm clamping, reasonable force, and convenient application, but the processability is poor.
The inner hole of the blade is positioned on the pin shaft of the insert groove, and when the pressure block with the inclined surface is pressed by the compression screw, the wedge piece abuts against the boss on the knife bar, and the other side pushes the blade to the cylindrical pin of the middle hole of the blade. Press the blade up. The structure is characterized by simple and convenient operation, but the positioning accuracy is low, and the clamping force is opposite to the cutting force. Regardless of the clamping method used, the blade must meet the following conditions when clamping: 1 The blade clamping position should conform to the positioning and clamping principle of the cutting force, that is, the combined force of the cutting force must act in the perimeter of the blade bearing surface. 2 blade peripheral size positioning needs to meet the three-point positioning principle. 3 The combined force of the cutting force and the clamping force on the positioning base surface (the blade and the blade body) must be greater than the alternating force caused by the cutting vibration to cause the blade to disengage from the positioning base surface.
ISO symbol (turning tool) CPMS
Description Top clamping cylindrical hole clamping top surface and cylinder
Hole clamping counterbore clamping
Second, geometric parameters and cutting performance
The shape of the indexable car blade is triangular, square, prismatic, pentagonal, hexagonal and circular. It is formed by die-casting of the cemented carbide factory, so that the blade has the geometric parameters for cutting. At the same time, the blade has more than three cutting edges for indexing. When one cutting edge wears, the clamping mechanism is loosened and the blade is indexed to another cutting edge to perform cutting. After the edges are worn out, remove them and replace them with new ones of the same type.
According to the use, the indexable car blade can be divided into outer circle, end face semi-finished car blade, outer round fine car blade, inner hole precision car blade, cutting blade and inner and outer threaded car blade. In addition, the blade is divided into two types: the hole has no back angle and the back has no hole. The hole in the blade is used for clamping the blade. If the blade has a back angle, the blade does not need to be installed in the sipe. Install the rear corner. If the blade has no back angle, you need to install the blade at a certain back angle when the blade is loaded with the sipe. Below are the geometric parameters of two typical machine clamping blades and turning tools.
· Finishing machine clamping knife blade: front angle g=20°, main rear angle a=8°~9°, secondary rear angle a'=6°～8°, main declination Kr=90°, secondary declination Kr'=5°, edge inclination angle l=0°～1°, reverse edge is -5°×(0.05～0.1), transition arc radius R=0.1～0.2mm (see Figure 5). · Semi-finished car gripper blade: front angle g=20°, rear angle a=6°～7°, main declination Kr=90°, 45° and 80°, secondary declination Kr'=10 Both ° and 45°, the reverse edge is -5° × (0.2 to 0.5), and the radius of the transition arc is R = 0.2 to 0.5 mm (see Figure 6). The finishing machine clamp cutter generally adopts a working front angle of 20°, a main rear angle of 8° to 9°, and a wedge angle b≤62°. Through cutting practice, it can be known that increasing the wedge angle will increase the cutting resistance, and vice versa, the cutting angle will be reduced, and the cutting resistance will also be reduced. A smaller wedge angle should be used in the finishing process, so that the cutting tool is sharp and the cutting is light. The blade inclination is usually selected from 0° to 1°. Selecting a small blade inclination allows the chips to be discharged into the back of the blade in the chipbreaker to avoid scratching the machined surface. The secondary relief angle and the secondary declination angle are small, so that the secondary flank surface has a long contact area with the machined surface of the workpiece, and the purpose of trimming the valley peak trajectory and reducing the surface roughness is achieved. The main declination is 90°, which can reduce the radial cutting resistance and adapt to the processing of multi-step parts.
The semi-finishing machine is often used for roughing and semi-finishing. It has many impact loads during cutting. The main deflection angle of the tool with impact load during cutting is usually 45° and 80°. The tool lead angle of the impact load is usually 90°. The semi-finishing machine with a lead angle of 45° and 80° has a sharp angle of 90° to enhance the tip strength; the semi-finishing machine with a main angle of 90° has a sharp angle of 80°. The blade inclination angle is 0° to 1°, the relief angle is 6° to 7°, and the reverse edge is -10° × (0.1 to 0.2). Sometimes it can be sharpened to 0.5 mm width according to the actual cutting conditions.
It can be seen from the above analysis that the principle of the design of the finishing machine is to enhance the sharpness of the tool and obtain a better surface quality. The principle of the design of the semi-finishing machine is to enhance the strength of the tool. Since the angle of the indexable turning tool is a combination of the angle of the blade and the angle of the bottom surface of the insert groove on the arbor, it is the algebraic sum of the geometrical angles of the relevant parts.
Name definition formula
The rake angle of the rake angle indexable tool is equal to the algebra of the rake angle of the blade and the arbor in the orthogonal plane and g0 cutter = g0 blade + g0 arbor
The back angle of the indexable indexable tool is equal to the difference between the back angle of the blade in the orthogonal plane and the rake angle of the toolholder in the orthogonal plane. a0 tool=a0 blade-g0 toolholder
The blade inclination angle of the indexable tool is equal to the algebra of the blade edge inclination angle and the blade edge inclination angle and the ls tool = ls blade + ls tool bar
The lead angle of the lead-off indexable tool is the Kr tool = Kr tool bar determined by the tool nose's main deflection angle.
Third, the conclusion
Through the analysis of the structure, geometric parameters and cutting performance of the indexable turning tool, the blade and the structural parameters of the tool body have a crucial influence on the cutting performance of the entire turning tool. In actual production, the structural parameters of the tool body are basically unchanged. Only by changing the geometric parameters of the blade can improve the cutting performance of the machine tool indexable turning tool, so that the tool can achieve the best cutting state in the production process. .
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Tag: Finishing car Cutting force Clamping force Geometric parameters Eccentricity
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