CN1986151A - Grinding method for superhard silicon carbide ceramic nano mirror - Google Patents

Abstract

The superhard silicon carbide ceramic nanometer mirror grinding process includes grinding the workpiece with dressed and shaped coarse diamond wheel in Z direction for plastic domain grinding with the cutting depth controlled within 100 nm; shifting the coarse diamond wheel in X direction for the distance fx and performing the next grinding so as to form envelope trace of height he on the surface of the workpiece and form flat smooth nanometer mirror. In the conditions of proper grinding wheel diameter Dish washer, fx smaller than 100 microns, the envelope trace height he will smaller than 15 nm. The present invention makes it possible to realize super precision surface machining in the machine tool of only micron level or submicron level precision. The present invention has low cost, great grinding ratio and high machining efficiency.

Description

A kind of method for grinding of superhard silicon carbide ceramic nano mirror

Technical field

The present invention relates to the surface of ultra-hard material processing technique field, be specifically related to a kind of method for grinding of superhard silicon carbide ceramic nano mirror.

Background technology

The nano mirror feature of finished surface shows as surface roughness R _aBeing that 20 nanometers are following does not have brittle break with the microcosmic finished surface.It is the important indicator that satisfies precision parts and the requirement of precision die mechanical performance.

Usually adopt the polishing agent finishing method that superhard materials such as superhard silicon carbide ceramic, converted steel are processed into minute surface.But polishing agent finishing method efficient is very low, and cost is very high, and seriously polluted.Therefore, adopt the ultra-fine diamond emery wheel to realize the mirror grinding processing of superhard material parts.But the dressing of ultra-fine diamond emery wheel is difficulty very, promptly is difficult to make micron-sized diamond abrasive grain to go out sword from grinding wheel bond.Though ELID (online electrolysis) can carry out the dressing of ultra-fine diamond emery wheel, realize the mirror grinding of ultra hard ceramic material.But the ultra-fine diamond abrasive particle comes off easily, and grinding ratio is low, and efficient is lower, and complexity such as dressing device, electrolysis power cost an arm and a leg, and technical difficulty is higher, and practicality is relatively poor.

In addition, adopt #120, the thickness skive of #240 and #500 carries out the silicon carbide ceramics grinding, can obtain surface roughness R respectively usually _aBe 200～600 nanometers, 150～550 nanometers and 120～450 nanometers.If realize the R of silicon carbide ceramics _aBe the following mirror grindings of 20 nanometers, then need carefully to arrive the skive of #3000.But fine grain diamond wheel grinding processing like this, its process technology difficulty is very high, thereby its processing charges is also very high.

Summary of the invention

The objective of the invention is to overcome the shortcoming of prior art, a kind of employing brait emery wheel (#180) is provided, process surface roughness less than 20 nanometers, and the nano mirror method for grinding of the superhard silicon carbide ceramic that processing cost is low, working (machining) efficiency is high.

Purpose of the present invention is achieved through the following technical solutions:

A kind of method for grinding of superhard silicon carbide ceramic nano mirror, emery wheel moves along the z axle of vertical emery wheel cutting direction, and workpiece is carried out grinding, and grinding is cut continuously by emery wheel upper blade abrasive particle, abrasive particle excision depth d _cBut the parameter of through type (1) control:

$d_c=\frac{2V_f\sin \left(\frac{\mathrm{\θ}}{2}\right)}{n_{g}N}---\left(1\right)$

In the formula, N is a grinding wheel speed, V _fBe the emery wheel speed of travel, n _gBe effective abrasive particle number, θ is the drift angle of abrasive grain cutting sword;

Control excision depth d _cBe 100 nanometers and following, can make the excision degree of depth of abrasive particle in grinding excise critical depth, make finished surface not have brittle break less than plastic region;

After finishing the axial grinding of z, along emery wheel cutting direction x-axle, emery wheel displacement f _xAfter when carrying out next grinding again, forming at surface of the work highly is h _eThe envelope mark, envelope mark height determined by the parameter of formula (3), wherein, D _wBe grinding wheel diameter:

$h_e=\frac{D_w-\sqrt{D_w^2-f_x^2}}{2}---\left(3\right)$

When selecting suitable grinding wheel diameter D _w, make the x-direction of principal axis move f _xDuring less than 100 microns, the envelope mark height h of grinding skin _eLess than 15 nanometers, can form smooth, ultra-smooth superhard silicon carbide ceramic nano mirror.

When control excision depth d _cBe 100 nanometers and when following, grinding face surface roughness R _aReach below 20 nanometers, wherein surface roughness R _aParameter by formula (2) is determined;

$R_a=\frac{v_f}{8n_{g}N\tan \frac{\mathrm{\θ}}{2}}---\left(2\right)$

In the formula, N is a grinding wheel speed, V _fFor grinding wheel spindle to the speed of travel, n _gBe effective abrasive particle number, θ is the drift angle of abrasive grain cutting sword.

During grinding, control emery wheel feeding depth a is less than 5 microns, in case the grinding vibration.

The present invention compared with prior art has following advantage and beneficial effect:

(1) compares with adopting ultra-fine diamond emery wheel mirror grinding, can save fine grinding and fine grinding technology, can more significantly improve the nano mirror working (machining) efficiency;

(2) because ultra-fine diamond abrasive particle work in-process constantly comes off, and brait emery wheel abrasive particle weares and teares gradually, so the brait emery wheel has bigger grinding ratio.

(3) abrasive particle of the grinding method of the present invention excision degree of depth does not rely on the emery wheel feeding depth, therefore can utilize Numeric Control Technology to realize ultra-precision surface processing on the lathe of micron order or submicron order, and need not adopt expensive nano-precision lathe.

(4) because diamond particles is thicker, do not need to carry out the galvano-cautery dressing, therefore, attachment device is simple, practical, and technology is grasped easily.

Description of drawings

Fig. 1 is a nano mirror grinding method schematic diagram of the present invention.

Fig. 2 is the abrasive grain cutting schematic diagram of nano mirror grinding.

Fig. 3 is the sem photograph of embodiment 1 microcosmic finished surface.

Fig. 4 is the coarse profile diagram of embodiment 1 finished surface.

The specific embodiment

For better understanding the present invention, below in conjunction with embodiment the present invention is done detailed description further, but the scope of protection of present invention is not limited to the scope that embodiment represents.

As shown in Figure 1, the method for grinding of superhard silicon carbide ceramic nano mirror is that the z axle of the vertical emery wheel cutting direction in skive 1 edge moves, and silicon carbide ceramics face 2 is carried out grinding, the coarse profile 3 of grinding.After finishing the axial grinding of z, along emery wheel cutting direction x-axle, emery wheel displacement f _xAfter when carrying out next grinding again, forming at surface of the work highly is h _eThe envelope mark, envelope mark height determined by formula (3) parameter, wherein, D _wBe grinding wheel diameter:

$h_e=\frac{D_w-\sqrt{D_w^2-f_x^2}}{2}---\left(3\right)$

When selecting suitable grinding wheel diameter D _w, make the x-direction of principal axis move f _xDuring less than 100 microns, the envelope mark height h of grinding skin _eLess than 15 nanometers, can form smooth, ultraphotic sliding surface.

As shown in Figure 2, skive 1 moves along the z axle of vertical emery wheel cutting direction, and the coarse profile 3 of grinding is will go out the sword profile duplication after being cut continuously by emery wheel 1 upper blade abrasive particle 4 to form abrasive particle 4 excision depth d on workpiece 2 _cBut the parameter of through type (1) control:

$d_c=\frac{2V_f\sin \left(\frac{\mathrm{\θ}}{2}\right)}{n_{g}N}---\left(1\right)$

In the formula, N is a grinding wheel speed, V _fBe the emery wheel speed of travel, n _gBe effective abrasive particle number, θ is the drift angle of abrasive grain cutting sword;

Control excision depth d _cBe 100 nanometers and following, can make the excision degree of depth of abrasive particle in grinding excise critical depth, make finished surface not have brittle break less than plastic region.The excision depth d _cBe 100 nanometers and when following, grinding face surface roughness R _aReach below 20 nanometers, wherein surface roughness R _aDetermine by formula (2) parameter;

$R_a=\frac{V_f}{8n_{g}N\tan \frac{\mathrm{\θ}}{2}}---\left(2\right)$

Embodiment

Go up the #180 brait emery wheel that adopts diameter 180mm at CNC precision grinder (SMRART B818), utilize CNC system drive emery wheel along the emery wheel axial traveling, (RB-SiC) carries out the nano mirror grinding to reaction sintering silicon carbide ceramic.Adopt the #180GC grinding stone that the #180 skive is carried out dressing, make the diamond abrasive grain of emery wheel working surface fully go out sword, keep certain height of protrusion.The dressing condition is: N=1500r/min, V _f=600mm/min, f _x=5mm, a=0.3mm, ∑ a=4mm, BM2 grinding fluid.Behind the dressing, adopt cast iron that the skive working surface that goes out sword is repaired, improve effective abrasive particle and count n _g, increase abrasive particle and on average go out the sword vertex angle theta.Cast iron finishing condition is: N=3000r/min, V _f=1500mm/min, f _x=0.1mm, a=5 μ m, ∑ a=0.1mm, BM2 grinding fluid.

In grinding process, adopt N=3000 rev/min of grinding wheel speed, V _f=5 millimeters/minute, emery wheel feeding depth a=5 micron, accumulative total emery wheel feeding depth ∑ a=0.6 millimeter, zero grinding 2 times and BM2 grinding fluid.

As shown in Figure 2, emery wheel 1 vertical emery wheel cutting direction (z-direction of principal axis) vertically moves, and workpiece 2 is carried out grinding, traditional grinding direction parallel with the emery wheel cutting direction (x-direction of principal axis).When emery wheel moves f along the x-direction of principal axis _xAfter when carrying out next grinding again, form the envelope mark on workpiece 1 surface, move f when the x-direction of principal axis in this example _xBe 100 microns, the envelope mark height h of grinding skin _eBe calculated as 13.9 nanometers according to formula (3), testing result workpiece 1 surface forms smooth, ultraphotic sliding surface as shown in Figure 3, and its envelope mark height h is described _eLess than 15 nanometers.

As shown in Figure 1, at the z-direction of principal axis, the coarse profile 3 of grinding is will go out the sword profile duplication after being cut continuously by emery wheel 1 upper blade abrasive particle 4 to form on workpiece 2, in this example, and N=3000r/min, n _g=120 and θ=125 °, V _fBe 20mm/min, abrasive particle excision depth d _cThrough type (1) is calculated as 98.6 nanometers, and from processing microcosmic surface shown in Figure 3, the no brittle break in workpiece 1 surface shows that abrasive particle excises the degree of depth and excises the degree of depth less than 100 nanometers at plastic region.The plastic region that can realize superhard material according to the ductile grinding theory excises processing, its surface roughness R _aBe calculated as 3.6 nanometers according to formula (2).Obtain the mirror finish effect.

After present embodiment carried out grinding to the superhard silicon carbide ceramic of reaction-sintered, the microcosmic finished surface after the processing did not have brittle break, after testing, forms minute surface as shown in Figure 3, the coarse profile of finished surface as shown in Figure 4, average surface roughness R _aBe 16.3 nanometers, less than 20 nanometers.Because process is subjected to the equipment vibrations, the grinding fluid ambiguity, the influence of the stability of power supply, theoretical value surface roughness and actual value that formula (2) is calculated are variant slightly, and this difference is within the zone of reasonableness that influenced by processing environment.

Claims (4)

1, a kind of method for grinding of superhard silicon carbide ceramic nano mirror is characterized in that: emery wheel moves along the z axle of vertical emery wheel cutting direction, and workpiece is carried out grinding, and grinding is cut continuously by emery wheel upper blade abrasive particle, abrasive particle excision depth d _cBut the parameter of through type (1) control:

$d_c=\frac{2V_f\sin \left(\frac{\mathrm{\θ}}{2}\right)}{n_{g}N}---\left(1\right)$

In the formula, N is a grinding wheel speed, V _fFor grinding wheel spindle to the speed of travel, n _gBe effective abrasive particle number, θ is the drift angle of abrasive grain cutting sword;

Control excision depth d _cBe 100 nanometers and following, can make the excision degree of depth of abrasive particle in grinding excise critical depth, make finished surface not have brittle break less than plastic region;

After finishing the axial grinding of z, along emery wheel cutting direction x-axle, emery wheel displacement f _xAfter when carrying out next grinding again, forming at surface of the work highly is h _eThe envelope mark, envelope mark height determined by the parameter of formula (3), wherein, D _wBe grinding wheel diameter:

$h_e=\frac{D_w-\sqrt{D_w^2-f_x^2}}{2}---\left(3\right)$

When selecting suitable grinding wheel diameter D _w, make the x-direction of principal axis move f _xDuring less than 100 microns, the envelope mark height h of grinding skin _eLess than 15 nanometers, can form smooth, ultra-smooth superhard silicon carbide ceramic nano mirror.

2,, it is characterized in that when control excision depth d according to the method for grinding of the described a kind of superhard silicon carbide ceramic nano mirror of claim 1 _cBe 100 nanometers and when following, grinding face surface roughness R _aReach below 20 nanometers, wherein surface roughness R _aParameter by formula (2) is determined;

$R_a=\frac{V_f}{8n_{g}N\tan \frac{\mathrm{\θ}}{2}}---\left(2\right)$

In the formula, N is a grinding wheel speed, V _fFor grinding wheel spindle to the speed of travel, n _gBe effective abrasive particle number, θ is the drift angle of abrasive grain cutting sword.

3,, it is characterized in that controlling emery wheel feeding depth a less than 5 microns, in case the grinding vibration according to the method for grinding of the described a kind of superhard silicon carbide ceramic nano mirror of claim 1.

4, according to any method for grinding of described a kind of superhard silicon carbide ceramic nano mirror of claim 1～3, it is characterized in that adopting grinding stone that skive is carried out dressing before the grinding, make the diamond abrasive grain of emery wheel working surface fully go out sword, keep certain height of protrusion; Behind the dressing, adopt cast iron that the skive working surface that goes out sword is repaired, improve effective abrasive particle and count n _g, increase abrasive particle and on average go out the sword vertex angle theta.

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