JP2005262363A - Extra-smooth grinding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an extra-smooth grinding processing method for remarkably improving processing efficiency, when extra-smoothly grinding a surface of a workpiece such as metal and nonmetal. <P>SOLUTION: The processing efficiency is numerically expressed by using a parameter for determining the processing efficiency of a highly smooth grinding method. A practicable maximally highly smooth processing efficiency is determined on the basis of its numerical expression and a practical technology, and extra-smooth grinding processing of finishing surface roughness of 100 nm or less, is performed at a predetermined grinding wheel diameter and grinding wheel peripheral velocity. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an ultra-smooth grinding method for finishing a surface of a workpiece such as a metal such as steel or non-ferrous metal or a non-metal such as ceramic, glass or plastic to a smooth surface.

  In recent years, higher quality and lower prices of equipment are being pushed more rapidly than ever before. In connection with this, the request | requirement about the high precision and high smoothness of components, etc. is increasing. Currently, in order to achieve a high smooth finish in the machining process for metal and non-metal workpieces, first, coarse grinding is performed with a coarse grindstone, and then finish processing is performed using fine and fine grindstones. Finally, it is finished to a highly smooth surface by polishing such as lapping and polishing.

  However, in such a processing method that finishes a highly smooth surface through such a processing step, it is necessary to transfer the workpiece every time the processing step changes, which requires a lot of time. Furthermore, polishing processing that finishes to a high smooth surface by constant pressure processing methods such as lapping and polishing cannot improve the processing accuracy, and the removal speed of the workpiece surface is very low. It takes a long time to process.

  For this reason, the current high smoothing finishing method using polishing requires a great deal of time and labor to finish the final finishing process, and the processing cost is very high. For this reason, the improvement measures are greatly expected in comparison with the conventional demands in addition to the strong demand for reduction of the processing price in the high-quality processing in recent years.

  Conventionally, high smooth finish by grinding has been studied as one method for improving the polishing process by using loose abrasive grains such as lapping and polishing to finish a high smooth surface at a constant pressure. In the grinding process using the grindstone with the abrasive grains fixed, a highly efficient finishing process can be performed by cutting the grindstone into the workpiece and grinding with a cutting device of a highly accurate grinder. Therefore, if a high smooth finish can be achieved by grinding, (1) improvement of machining efficiency and shortening of the total machining time by omitting the workpiece transfer process, and (2) machining with high accuracy in addition to high smoothness. Advantages such as being possible arise.

  Such high-smoothing processing by grinding can lead to a significant reduction in processing time in the polishing process if high-smooth finishing close to that of polishing can be performed, even if it is not an alternative to polishing. For this reason, there are very high expectations for a high smooth finish by grinding.

  However, it is usually not easy to reduce the finished surface roughness to 1 μm (Ry value) or less by the plunge grinding method or the traverse grinding method currently being performed. In particular, it is difficult to obtain a mirror-finished surface of 100 nm (Ry value) or less (Non-Patent Document 1), and it is very difficult to perform highly smooth grinding that can replace polishing.

  For these reasons, the present inventor recently developed a new concept of high smooth grinding (Patent Document 1, Non-Patent Document 2).

Japanese Patent Laid-Open No. 2003-94296 Supervised by Akira Kobayashi: Super Precision Production Technology System (Volume 1) Basic Technology, Fuji Techno System (1995) p.181 Heiji Yasui: Journal of Japan Society for Precision Engineering, Vol. 69, No. 12 (2002) pp.1713-1717

An example of applying the high smooth grinding method developed by the present inventor to horizontal axis angle table type surface grinding is schematically shown in the perspective view of FIG. First, (1) the feed amount f _Gn of the workpiece 2 in the direction perpendicular to the grinding direction per rotation of the grinding stone 1 in the direction perpendicular to the grinding direction of the grindstone 1 or the workpiece 2 (hereinafter referred to as “workpiece perpendicular feed”). The cutting speed of the cutting edge flank 3 perpendicular to the grinding direction 3 wear width w _n (if different cutting edge flank surfaces are considered to be connected, the total flank width) Then, the grinding wheel-workpiece contact width is processed (first requirement). (2) After that, the geometrically calculated grinding wheel-workpiece interference height (corresponding to the finished surface roughness Hp parallel to the grinding direction) is less than the required high smooth finished surface roughness Hmax. The grindstone 1 or the workpiece 2 is intermittently moved by a minute feed amount fp in the grinding direction (second requirement). Then, the next grindstone-workpiece contact width is finished. By repeating this, the entire surface of the workpiece can be finished to a highly smooth surface. This method is a grinding method that can be replaced with a polishing process or finishes a highly smooth surface close to the polishing process.

 When applied to ultra-smooth grinding with a normal horizontal axis table surface grinder as shown in FIG. 1, the machining efficiency is better than that of the polishing method, but the removal rate is as grinding. Is slow and processing efficiency is poor. The same can be said for the cylindrical grinding method and the curved grinding method. For this reason, development of the method and apparatus which can improve processing efficiency markedly is anticipated strongly. This invention makes it a subject to develop the processing method which improves a processing efficiency markedly when performing super smooth grinding.

The present inventor formulates the machining efficiency using the parameter for determining the machining efficiency of the high smooth grinding method, and determines the maximum high smoothing machining efficiency that can be put into practical use based on the mathematical formula and the practical technique. A method of performing ultra-smooth machining has been developed.
That is, the present invention includes (1) various grinding methods such as a surface grinding method, a cylindrical grinding method, an inner surface grinding method, and a curved surface grinding method that use a grinding wheel as a tool to finish the grinding wheel or workpiece in the grinding wheel rotation direction (grinding direction). )), The workpiece feed rate f _Gn per rotation of the grinding wheel is the cutting edge flank wear width perpendicular to the grinding direction (if different cutting edge flank faces are considered to be connected, the total After machining the grinding wheel-workpiece contact width by feeding it to a feed speed less than the clearance surface width), the geometrically calculated grinding wheel-workpiece interference height requires a high smooth finish surface. Repeatedly moving the workpiece or grindstone intermittently by a small feed amount fp in the direction parallel to the grinding direction so that the roughness is less than the roughness, and finishing the next whetstone-workpiece contact width. High smooth grinding method that finishes the entire surface to a high smooth surface ,
Maximum removal speed M determined by the following formula (1) (where t is the grinding wheel cutting depth and Ng is the grinding wheel speed)
M ＝ f _Gn・ t ・ fp ・ Ng ―― (1)
Maximum finished surface roughness determined by the following formula (2) (Hp) _LIM (where Dg is the wheel diameter)
(Hp) _LIM = (fp) ² / 4Dg ―― (2)
Allowable wheel shaft rotation speed determined by the following formula (3) or (4) (where Dp is the wheel shaft diameter to be used) (Ng) max = (Vg) max / π · (Dg) max ―― (3)
(Ng) max = (D · N) max / Dp-(4) (Dp: Grinding wheel shaft diameter)
And a method of performing ultra-smooth grinding with a finished surface roughness of 100 nm or less at a grinding wheel diameter and a grinding wheel peripheral speed.

Further, in the present invention, by finishing the grindstone shaft in a direction perpendicular to the grinding direction at an angle θ, the finished surface roughness Hmax determined by the following equation (5) with respect to the finished surface roughness Hp when not inclined is obtained. (1) The method for performing ultra-smooth grinding according to the above (1)
Hmax = Hp • sinθ = [(fp) ² / 4Dg] • sinθ— (5)

The ultra-smooth grinding method of the present invention has the following effects.
1) The machining efficiency can be increased by 10 times compared to the case where the current general grinding technique using a grindstone with a commonly used diameter is applied to an ultra-smooth grinding method. I can do it.
2) The smoothness formed by the ultra-smooth grinding method is almost the same as that obtained when an ordinary general grinding technique is applied to the super-smooth grinding method with an ordinary grinder.
3) When a small-diameter grindstone is used, the manufacturing cost is low, and there is an advantage that processing is possible with a small and inexpensive grinder.

The ultra-smooth grinding method of the present invention will be described in detail below by taking as an example the case of applying to surface grinding. In order to implement the high smooth grinding method shown in FIG. 1, it is necessary to satisfy the following constraints.
(1) Cutting wheel flank wear width (different cutting distance) when the grinding wheel or workpiece is perpendicular to the grinding wheel rotation direction (grinding direction) and the workpiece feed rate (f _Gn ) per grinding wheel rotation is perpendicular to the grinding direction. If the blade flank surfaces are considered to be connected, feed them so that the feed speed is less than the total flank width)
(2) The work piece or the grindstone is intermittently minutely parallel to the grinding direction so that the geometrically calculated grindstone-workpiece interference height is less than the required high smooth finish surface roughness. (Fp) To move.

Considering the requirement (1), since there is a limit to the flattening of the grinding wheel work surface that can be formed by reshaping and reshaping the current grinding wheel, as shown in FIG. 2, the grinding direction per grinding wheel rotation The workpiece feed rate f _Gn perpendicular to the axis cannot be increased as much as possible, but has a maximum allowable feed rate (f _Gn ) cr (about 40 μm in the case of FIG. 2). Cannot get bigger because it gets worse quickly.

In order to obtain the required finished surface roughness from the requirement (2), for example, in the angular table type horizontal axis surface grinding, the formed finished surface roughness Hp is geometrically Hp = ( Since fp) ² / 4Dg (Dg: wheel diameter) is obtained, it is necessary to determine fp and Dg for obtaining the maximum finished surface roughness (Hp) _LIM using this relationship.

  On the other hand, when the mathematical expression is derived using the grinding condition parameter for the removal speed M of the workpiece, in the example of the horizontal axis table surface grinding shown in FIG. The removal amount per round, that is, the removal speed M, is represented by the following equation, where S is the removal area perpendicular to the grinding direction per grinding pass (see FIG. 1).

M ＝ S ・ v _wn ―― (A) (where v _wn ＝ f _Gn・ Ng: Wheel feed speed, Ng: Wheel rotation speed)
Moreover, the removal area S can be approximated by the following equation, as can be seen from the schematic diagram of FIG.
S ≒ (1/2) ・ l _{c ・} g _max ―― (B) (where l _c = (t ・ D _g ) ^0.5 : contact arc length, Dg = 2Rg: grinding wheel diameter, t: grinding wheel cutting Depth, g _max = fp ・ (4t / D _g ) ^0.5 : Maximum grinding wheel cutting depth)

Substituting (B) into (A) and rearranging, the removal rate is
M ＝ f _Gn・ t ・ fp ・ Ng ―― (1)
It becomes.

Therefore, in the grinding method of the present invention, the removal rate M is determined by the values of f _Gn , t, fp, and Ng, and the removal rate can be improved by increasing these values. Therefore, we will examine the possibility of increasing those parameters. First, it is f _Gn , but since it is necessary to satisfy the above requirement (1), there is a limit to increasing f _Gn at present, and a very small value of about 40 μm / rev is the limit. It is.

  Next, the second grinding wheel cutting depth t is an amount related to the machining allowance and is not an amount that can be appropriately changed. However, if the machining allowance is large, it can be said that the grinding wheel cutting can be increased up to the range where the grinding wheel shaft rigidity can withstand and the range where the bad grinding phenomenon occurs (grinding burn, cracking, etc.) or less.

Third, fp needs to satisfy the above-mentioned constraint (2), and the following equation must be satisfied.
(Hp) _LIM = (fp) ² / 4Dg-(2)

  As can be seen from the above equation, when fp is increased, the same finished surface roughness cannot be obtained unless the grindstone diameter is increased by its square. FIG. 3 shows the relationship between fp and finished surface roughness Hp with Dg as a parameter. The diameter of the grinding wheel is shown in the range of φ10 mm to φ300 mm, but it is usually about φ100 mm to φ300 mm that is often used.

  In addition, when trying to obtain an ultra-smooth ground surface, that is, a ground surface having a surface roughness of 100 nm (Rz) or less, for example, considering a surface roughness of Hp = 100 nm, the range of the grindstone diameters Dg and fp is viewed. For example, in a whetstone of φ10 mm, fp is about 80 μm / rev, whereas in a whetstone of φ300 mm, fp is about 450 μm / rev, which can be increased by about 5.4 times.

  Finally, the rotation speed of the grinding wheel is Ng. This is because the practical maximum grinding wheel rotation speed is the allowable grinding wheel peripheral speed (Vg) related to rotational breakage of the grinding wheel, max = π · Ng · Dg (Dg: normal grinding wheel) In manufacturing technology, the maximum D / N value (D · N) max (currently about 2,500,000) determined by the product of the shaft diameter D and the shaft speed N of the grinding wheel shaft is 100m / s) or less. Is a constraint.

Therefore, it is necessary to calculate and determine the maximum allowable grinding wheel rotational speed (Ng) max using the following formula (3) or (4) and use it at a grinding wheel rotational speed lower than that.
(Ng) max = (Vg) max / π ・ (Dg) max ―― (3)
(Ng) max = (D · N) max / Dp-(4) (Dp: Grinding wheel shaft diameter)

  Since the product of the wheel diameter and the rotation speed is constant, the maximum allowable wheel rotation speed that can be used increases in inverse proportion to the decrease in the wheel diameter. For example, the maximum number of rotations can be increased up to 30 times when a φ10 mm grindstone is used, compared to the case where a φ300 mm grindstone is used.

  As described above, it is considered appropriate to increase fp and Ng in order to increase the removal rate M. However, the maximum permissible values are related to the wheel diameter. The allowable wheel speed can be increased, but the maximum allowable feed can only be increased in inverse proportion to the 1/2 power. From this, the removal speed M can basically be increased more greatly by decreasing the grindstone diameter and increasing the grindstone rotation speed.

  For example, in order to obtain the same surface roughness, the removal speed can be increased up to 5.4 times by increasing the fp of the grindstone having a diameter of 300 mm than by the grindstone having a diameter of 10 mm. On the other hand, from the viewpoint of the maximum allowable wheel rotation speed, the wheel diameter of φ10mm can be 30 times larger than that of the wheel with a wheel diameter of φ300mm. Although it is necessary to reduce fp when rotating at high speed, it can be said that it can increase to a large removal speed.

As described above, the improvement of the removal speed has been examined by taking the case of the angle table type horizontal axis surface grinding as an example. In this case, as shown in FIG. )Met. As shown in the example of FIG. 4 of ultra-smooth surface grinding by vertical surface grinding, when this angle is ground and the grindstone is tilted, the geometric finished surface roughness Hmax is
It is expressed by the following formula.

Hmax = Hp · sinθ = [(fp) ² / 4Dg] • sinθ ―― (5)
Therefore, if the grindstone axis in the case of the horizontal axis grinding shown in FIG. 1 is greatly inclined, the finished surface roughness can be kept small even if the grindstone having the same grindstone diameter is used. If this is utilized, even if a small-diameter grindstone is used as described above, it can be coped with without reducing the grinding direction parallel intermittent feed amount fp. Further, when the equation (5) is modified, it can be rewritten as follows.

(Fp) _r = [Hp • 4Dg / sinθ] ^0.5 ―― (6)
Dg (fp) _r = [Hp • 4Dg / sinθ] ^0.5

  FIG. 5 shows the relationship between the grinding direction parallel intermittent feed amount fp and the inclination angle θ and the geometric finished surface roughness Hp. Note that the inclination angle θ is 90 degrees in the case of horizontal axis grinding with respect to the workpiece, and 0 degrees when it is inclined at a right angle. From FIG. 5, it is understood that when the grindstone axis in the horizontal surface grinding is greatly inclined and the inclination angle θ is decreased, the geometric finished surface roughness becomes very small. For example, if the tilt angle θ is set to about 3 degrees and is close to vertical axis grinding, even if fp = 60 μm, Hmax is 4 nm, which can be sufficiently reduced. In the case of a grindstone diameter of φ100 mm, fp = 40 μm and 4 nm. It can also be seen that when the grindstone axis is tilted, the geometric finished surface roughness can be reduced even if the grinding direction parallel intermittent feed amount fp is increased.

Fig. 6 shows a grinding wheel circumferential speed of 50 m / s as a normal grinding wheel speed. (1) A grinding wheel with a grinding wheel diameter of 100 mm, which is the smaller grinding wheel diameter, is used as a grinding wheel often used in normal grinding. -When grinding to make an ultra-smooth surface with a bull-type horizontal-axis surface grinder, and (2) Grinding with a vertical-shaft grinder with a small-diameter grindstone of φ14mm and a high-smooth surface with an inclination angle θ of 3 degrees. This is a comparison of the removal rate when performing the above. The rotation speeds of the φ100 mm and φ14 mm wheels are about 159 rps and about 1137 rps, respectively.

Note that, in both grinding methods, the feed amount in the grinding direction per rotation of the grindstone is the same as f _Gn = 20 μm / rev. In both grinding methods, the geometric finished surface roughness formed is about 4 nm. For this reason, the grinding direction parallel intermittent feed amount fp is calculated using fp = 40 μm for horizontal axis grinding and fp = 60 μm for vertical axis grinding. From FIG. 6, it can be seen that the removal rate is about 10 times, and the processing efficiency can be remarkably improved.

A small grinding wheel shaft with a diameter of 14 mm was attached to a vertical grinding machine with an ultra-high-speed spindle grinding wheel shaft, and ultra-smooth surface grinding of 10 mm square silicon carbide fine ceramic was performed at an ultra-high speed rotation of 60000 rpm (1000 rps). As the grindstone, a metal bond grindstone having a coarse grain size of # 140 and a concentration of 50 was used. Soluble was used as the grinding fluid. The grinding wheel shaft was attached to the workpiece surface with an inclination of 3 degrees with respect to the vertical direction. The workpiece normal feed rate f _Gn was 5 μm / rev, the grinding wheel cutting depth t was 5 μm, and the intermittent feed rate fp parallel to the grinding direction was 90 μm / rev. The rotation speed of the grinding wheel is 17 times (60000 rpm / 1000 rps) compared to the relatively high speed (3600 rpm / 60 rps) of normal horizontal axis surface grinding. On the other hand, the grinding wheel peripheral speed Vg is about 50 m / s, which is in the category of ordinary grinding wheel manufacturing technology. The removal amount M by grinding per unit time was 0.37 mm ³ / min.

FIG. 7 shows X and Y profiles obtained by two-dimensional roughness measurement of the surface of a silicon carbide fine ceramic workpiece ground according to Example 1 using an optical interference type high precision surface measuring instrument (WYKO). As can be seen from FIG. 7, the grinding surface parallel finished surface roughness actually obtained is 14 μm in PV value (Rt value in FIG. 7) and 3 nm or less in Ra value. The surface roughness is about 23 nm in terms of PV value and about 4 nm in terms of Ra value, which indicates that ultra-smooth grinding can be performed with high efficiency.

  With the method of the present invention, a small-diameter grindstone is attached to a grinder having an ultrahigh-speed spindle grindstone shaft for the purpose of applying to surface grinding, cylindrical grinding, internal grinding, curved surface grinding, etc. Super smooth grinding of metal (ceramic, glass, plastic) can be performed. In addition, a small-diameter grindstone is attached to a vertical grinder or vertical NC grinder with an ultra-high-speed spindle grindstone shaft for the purpose of applying to surface grinding or curved surface grinding, and the grindstone shaft is tilted slightly with respect to the vertical direction. Super smooth grinding can be performed.

It is a perspective view which shows typically the example in the case of applying the principle of the super smooth grinding method of this invention to a horizontal axis angle table type surface grinding. Relationship between workpiece feed rate f _Gn per grinding wheel revolution and finish surface roughness (H _3D : Finished surface roughness for 256 mm square area, Hp: Finished surface roughness for grinding direction parallel measurement length of 256 mm, Hn : Grinding direction perpendicular measurement length is a graph showing the finished surface roughness for 256 mm. It is a graph which shows the relationship between the grinding direction parallel intermittent feed amount with respect to various grindstone diameters, and geometric grinding direction finishing surface roughness. It is a schematic diagram which shows the method of applying to the surface grinding the method of rotating a small diameter grindstone ultra-high speed by the method of this invention, and performing a highly efficient super smooth grinding process. It is a graph which shows the inclination angle (theta) of a grindstone axis | shaft, the grinding direction parallel intermittent feed fp, and geometric finish surface roughness Hmax. When using an ordinary horizontal axis surface grinder for ultra-smooth grinding using a grindstone with a commonly used grindstone diameter, or when using a vertical grinder with a small-diameter grinder and performing ultra-smooth grinding with a small tilt angle θ It is a graph which shows the comparison result of a removal rate. 2 is a drawing-substituting photograph showing X and Y profiles obtained by two-dimensional roughness measurement using a light interference type high precision surface measuring device (WYKO) of a surface of a silicon carbide fine ceramic workpiece ground according to Example 1;

Claims (2)

The grinding wheel or workpiece is rotated one time in the direction perpendicular to the grinding wheel rotation direction (grinding direction) by various grinding methods such as the surface grinding method, cylindrical grinding method, internal grinding method, and curved surface grinding method. The workpiece feed rate f _Gn is less than the cutting edge flank wear width perpendicular to the grinding direction (the total flank width if different cutting edge flank surfaces are considered to be connected). After machining the grinding wheel-workpiece contact width, the geometrical calculation of the grinding wheel-workpiece interference height is less than the required high smooth finish surface roughness. High smoothness that finishes the entire surface of the workpiece to a highly smooth surface by repeatedly moving the workpiece or the grindstone by the minute feed amount fp in the direction parallel to the grinding direction to finish the next wheel-workpiece contact width. In the grinding method,
Maximum removal speed M determined by the following formula (1) (where t is the grinding wheel cutting depth and Ng is the grinding wheel speed)
M ＝ f _Gn・ t ・ fp ・ Ng ―― (1)
Maximum finished surface roughness determined by the following formula (2) (Hp) _LIM (where Dg is the wheel diameter)
(Hp) _LIM = (fp) ² / 4Dg ―― (2)
Allowable wheel shaft rotation speed determined by the following formula (3) or (4) (where Dp is the wheel shaft diameter to be used) (Ng) max = (Vg) max / π · (Dg) max ―― (3)
(Ng) max = (D · N) max / Dp-(4) (Dp: Grinding wheel shaft diameter)
A method of performing ultra-smooth grinding with a finished surface roughness of 100 nm or less at a grinding wheel diameter and grinding wheel peripheral speed. By inclining the grindstone axis in a direction perpendicular to the grinding direction at an angle θ, the finished surface roughness Hmax determined by the following equation (5) is set to the finished surface roughness Hp when not inclined. Item 2. A method for performing ultra-smooth grinding according to Item 1.
Hmax = Hp • sinθ = [(fp) ² / 4Dg] • sinθ— (5)

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