Main geometric angles and selection of cutting too

2022-06-11
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The main geometric angle and selection of cutting tools

the structural elements and geometric angle of the cutting part of metal cutting tools have many common characteristics with axes and other tools. As shown in Figure 1, all kinds of multi tooth tools or complex tools are equivalent to one tool tooth, so the resolution R is 1.5 of the variation range plus the tool head of one incremental axe. Now take the familiar turning tool as an example to illustrate the main geometric angle of the tool

Figure 1 cutting part of the tool

1. Composition of the cutting part of the turning tool

the cutting part of the turning tool is composed of the rake face, the main flank, the auxiliary flank, the main cutting edge, the auxiliary cutting edge and the tool tip (as shown in Figure 2)

Figure 2 carbide external turning tool

(1) the surface on which the chip flows on the rake face tool

(2) the surface on the main flank tool opposite and interacting with the machining surface on the workpiece is called the main flank

(3) auxiliary flank the surface of the tool opposite and interacting with the machined surface on the workpiece is called auxiliary flank

(P) the intersection between the main cutting edge and the upper cutting edge (P>)

(5) auxiliary cutting edge the intersection of the upper rake face and the auxiliary flank of the tool is called auxiliary cutting edge

(6) the intersection of the main cutting edge of the tool tip and the auxiliary cutting edge is called the tool tip. The tool tip is actually a small section of curve or straight line, which is called rounding tool tip and chamfering tool tip

2. Main angle of turning tool cutting part

(1) auxiliary plane for measuring the cutting angle of turning tool

Figure 3 auxiliary plane for measuring turning tool

in order to determine and measure the geometric angle of turning tool, three auxiliary planes need to be selected as datum, which are cutting plane, base plane and orthogonal plane, as shown in Figure 3

1) cutting plane PS cutting plane is a plane tangent to a selected point of the main cutting edge and perpendicular to the bottom plane of the cutter bar

2) base plane PR base plane is a plane passing through a selected point of the main cutting edge and parallel to the bottom surface of the cutter bar

3) the main section of orthogonal plane P0 is a plane perpendicular to the cutting plane and the base plane

it can be seen that the three coordinate planes are perpendicular to each other to form a spatial rectangular coordinate system

Figure 4 main angle of turning tool

(2) main geometry of turning tool and its selection

1) rake angle the included angle between rake face and base plane measured in orthogonal plane. The positive and negative directions of the rake angle are indicated as specified in the figure, that is, when the rake surface of the tool is below the base surface, it is a positive rake angle, and when the rake surface of the tool is above the base surface, it is a negative rake angle. The front angle is generally selected between - 5 ~ 25

selection principle of rake angle: the size of rake angle mainly solves the contradiction between the firmness and sharpness of cutter head. Therefore, the front angle of 5 - 5 00kn should be selected according to the hardness of the processing material. The hardness of the processed material is high, and the front angle is taken as the small value, otherwise the large value is taken. Secondly, the size of the rake angle should be considered according to the processing nature. The rake angle should be taken as the small value during rough processing and the large value during finish processing

2) the included angle between the main flank and the cutting plane measured in the orthogonal plane. The back angle cannot be zero or negative, and is generally selected between 6 and 12

selection principle of back corner: first consider the processing nature. During finish machining, the rear angle takes the large value, while during rough machining, the rear angle takes the small value. Secondly, consider the hardness of the processing material. The hardness of the processing material is high, and the main rear angle is taken as a small value to enhance the robustness of the cutter head; On the contrary, the back angle should be taken as the smaller value

3) the included angle between the projection of the main cutting edge on the base plane and the feed direction measured in the base plane. The main deflection angle is generally selected between 30 and 90

selection principle of main deflection angle: first consider the rigidity of the turning process system composed of lathe, fixture and tool. If the rigidity of the turning process system is good, the main deflection angle should be taken as a small value, which is conducive to improving the service life of turning tool and improving heat dissipation conditions and surface roughness. Secondly, the geometry of the workpiece to be processed should be considered. When processing steps, the main deflection angle should be 90, and for the workpiece cut in in the middle, the main deflection angle is generally 60

Figure 5 symbol of edge inclination

4) the included angle between the projection of the auxiliary cutting edge on the base plane measured in the base plane and the opposite direction of feed movement. The deflection angle is generally positive

selection principle of auxiliary deflection angle: first consider that the turning tool, workpiece and clamp have sufficient rigidity, so as to reduce the auxiliary deflection angle; On the contrary, the larger value should be taken; Secondly, considering the processing properties, the secondary deflection angle can be 10 ~ 15 during rough processing, and about 5 during rough processing

5) edge inclination s is the angle between the main cutting edge and the base surface measured in the cutting plane. When the main cutting edge is horizontal, s = 0; When the tool tip is the highest point on the main cutting edge, s> 0; When the tool tip is the lowest point on the main cutting edge, s <0 (as shown in Figure 5). The blade inclination is generally selected between - 10 ~ 5

selection principle of edge inclination: mainly depends on the processing nature. During rough processing, the impact of workpiece on turning tool is large, S 0. During finish processing, the impact of workpiece on turning tool is small, S 0, generally s = 0

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