Dislocation ironing of PCD tool flank during the h

2022-08-08
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The dislocation pressing effect of PCD tool flank during ultra precision cutting

1 Analysis of the pressing effect of PCD tool flank during precision and ultra precision cutting

PCD tools are more and more widely used in the field of precision and ultra precision cutting with their superior performance. Because precision and ultra precision cutting belong to micro cutting, and the cutting thickness is very small, which is often equivalent to the blunt radius of the blade, precision and ultra precision cutting have their own characteristics (see Figure 1)

Figure 1 precision and ultra precision cutting model

point O in Figure 1 is the diversion point, AC is the cutting depth, RN is the blunt radius of the cutting edge, and the production experimental machine is world-famous. U is the metal layer to be cut below point O, G0 is the rake angle of the tool, and A0 is the rake angle of the tool. Due to the small cutting thickness, the UN cut metal below the shunting point becomes a visible part of the cutting layer metal. Due to the function of the blunt circle radius of the blade, this part of metal is forced to bypass the blunt circle of the blade and flow out along the flank under great pressure, so that at this time, the plastic deformation of the workpiece caused by the ironing effect of the flank is more dominant than the cutting effect of the tool, and directly affects the formation of the machined surface. In Figure 1, l0 is the contact length between the U layer and the flank, that is, the length of the ironing action of the flank, and H is the elastic recovery of the U layer metal after it is squeezed through the blunt circle of the cutting edge. It can be seen that in the process of precision and ultra precision cutting, the ironing effect of PCD tool flank on the cutting process can not be ignored. So far, there is little special research on the ironing effect of the flank of PCD tools. Therefore, this paper focuses on the ironing effect of the flank of PCD tools, which is of practical significance for in-depth study of precision and ultra precision cutting processes and improving the quality of machined surfaces

pcd tools need to be grinded before use. The grinding condition, back angle, roughness and grinding texture of the back surface all directly affect the ironing effect of the back surface on the workpiece surface. Among them, the grinding texture of the flank refers to a series of grooves left by the grinding wheel on the flank when the tool is grinded. The included angle between the grinding direction of the grinding wheel (i.e. the grinding texture direction of the flank) and the direction of the tool polishing edge is called the grinding texture angle of the flank, which is expressed in Q, and 0 ° ≤ Q ≤ 90 ° (see Figure 2)

Figure 2 Schematic diagram of sharpening texture angle Figure 3 view of the flank

Figure 3 is the view of the flank. The solid line in the figure represents the sharpening texture of the flank, the dotted line represents the measurement direction of the roughness of the flank parallel to the polishing edge, and D is the measurement spacing

it can be seen from Figure 3 that due to the influence of grinding texture, there is a relative displacement t between two adjacent parallel contours with small spacing, which is called dislocation. The value of t can be obtained by measuring the displacement of adjacent contour peaks, and it can also be estimated by using the cross-correlation function. If the profile functions of adjacent sections are fi (x) and FJ (x) (i=1,2,...; j=i+1), the cross-correlation function Rij (T) of the two is: (1)

when Rij (T) reaches the peak, it indicates that the profiles of adjacent sections have the greatest degree of similarity, and the value of t at this time is the relative displacement of the profiles of adjacent sections. According to figure 3, the relationship between Q, t and D of the damaged sample is: (2)

t when D is the unit length is called the dislocation strength, which is represented by K, that is: (3)

formula (3) represents the relative displacement between adjacent section profiles, that is, the intensity of dislocation. K is closely related to the direction of surface texture. The smaller q is, the greater K value is, the greater the relative displacement of adjacent section profiles is, and the stronger the dislocation is. Due to the existence of dislocation between the profiles of adjacent sections of the back face, the ironing process of the back face to the workpiece surface is equivalent to the process of different sections parallel to the polishing blade on the back face sliding across the workpiece surface alternately. Therefore, the essence of ironing the workpiece surface by the back face of PCD tools is dislocation ironing

it can be seen from Figure 1 that the back angle affects the length of the dislocation ironing effect of the PCD tool back face; It can be seen from Figure 3 that the roughness of the flank affects the profile of different sections of the flank of PCD tools parallel to the direction of the polishing edge, and the grinding texture of the flank affects the dislocation strength between the profiles of different sections of the flank of PCD tools, that is, the changes of the flank angle, the roughness of the flank and the grinding texture of the flank of PCD tools directly affect the effect of dislocation ironing of the flank

2 PCD tool back face dislocation ironing law test

1) influence of back angle on dislocation ironing effect

machine tool: cm0420m/2 precision instrument lathe tool: straight edge PCD Tool (Korean blade), particle size 20 m, g0=0 °, main deflection angle kr=10 °, auxiliary deflection angle kr'=10 °, polishing blade length lf=0.4mm, q=5 °, front blade surface roughness rag=0.015 m, rear blade surface roughness raa=0.08 m, 1# knife a0=5., 2 # knife a0=8 °, 3 # knife a0=12 °, 4 # tool a0=15 ° workpiece material: LY12 cutting conditions: spindle revolutions n=1795r/min, cutting depth ap=10 m, feed rate f=3,5,7,9,15,25 m/r, ethanol cutting fluid measuring instrument: form Talysurf shape profiler test results: see Figure 4. The effect of the vertical coordinate raw critical interrupt switch in the figure is that the operator manually interrupts the experimental machine when an abnormal state occurs in the experiment, and the task is workpiece surface roughness, Curves (1) ~ (4) are the cutting results of 1 # ~ 4 # (the same below)

Figure 4. The influence law of the back angle on the dislocation ironing effect

it can be seen from Figure 4 that the smaller the back angle is, the smaller the workpiece surface roughness value obtained after cutting by the PCD tool, indicating that the better the dislocation ironing effect of the back surface is

2) influence of the roughness of the back cutter surface on the effect of dislocation ironing

test conditions:

machine tool: msg-325 double axis CNC diamond lathe tool: straight edge PCD Tool (blade of Shanghai Silicate Research Institute), particle size 15 m, g0=0 °, a0=10 °, kr=k r'=10 °, lf=0.2mm, q=5 °, 1 # knife rag= 0.037 m, raa= ∧ 0.019 m, 2 # knife rag=0.038 m, raa=0.038 M 2 m, 3 × knife rag= 0.0 the hydraulic universal testing machine adopts the electro-hydraulic servo valve 40 m, Raa=0.140 m, 4 # knife rag=0.038 m, raa=0.563 m workpiece material: LY12 cutting conditions: n=1000r/min, ap=5 m, f=3,5,7,9,15,25 m/r, hydrocarbon coolant spray cooling measuring instrument: form Talysurf shape profiler test results are shown in figure 5:

Figure 5 the influence law of the roughness of the rear knife surface on the effect of dislocation ironing

it can be seen from Figure 5 that the raw value obtained after 1 # knife cutting is small.For example, the raw value obtained after cutting with 4 # cutter is large, It shows that the smaller the RAA, the better the ironing effect of knife surface dislocation

3) influence of the grinding texture of the back blade surface on the effect of dislocation ironing

test conditions:

machine tool: msg-325 double axis CNC diamond lathe tool: straight edge PCD Tool (blade of Shanghai Silicate Research Institute), particle size 15 m, g0=0 °, a0=10 °, kr=k r'=10 °, lf= 0.6mm, rag= 0.025 m, raa=0.035 m, 1# tool q=5 °, 2# tool q=30 °, 3# tool q=60 °.4 # cutter q=90 ° workpiece material: LY12 cutting conditions: n=1000r/min, ap=10 m, F=3,5,7,9,15,25 m/r, hydrocarbon coolant spray cooling measuring instrument: the test results of form profiler are shown in figure 6:

Figure 6 the influence law of the grinding texture of the rear blade surface on the dislocation ironing effect

it can be seen from Figure 6 that under the same other conditions, the cutting effect is also different due to the different grinding texture of the rear blade surface, the cutting effect of 4 # knife is the worst, and the cutting effect of 1 # knife is the best, that is, with the reduction of Q, When the workpiece surface roughness value decreases, the better the ironing effect of PCD Tool backface dislocation

3 conclusion

in the process of precision and ultra precision cutting, the ironing effect of PCD tool back knife on the workpiece surface is essentially dislocation ironing. The main factors affecting the ironing effect of PCD tool flank dislocation are tool flank angle, flank roughness and flank grinding texture. PCD tools with small back angle, small back knife surface roughness value and small grinding texture angle have strong dislocation ironing effect on the workpiece surface, and their dislocation ironing effect is good, so it is easy to obtain the workpiece surface with small roughness value. (end)

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