JP2013000867A - Deflection accuracy measuring method and grinding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a deflection accuracy measuring method for measuring vibration precision while grinding and a grinder for performing contact removal grinding and cutting in accordance with a deflection amount measured.SOLUTION: A displacement change Δs=s-sat a prescribed angle Θof rotation and a warp change Δti=t-ti being an amount of change of warp are used to calculate a radius size change corresponding to the angle Θof rotation with a surface position sof a processing part at point A satisfying Θ=0 measured by a surface position measuring device 85 during one rotation of a workpiece W in the midst of grinding and warp tas reference. Deflection Fis calculated by adding to the radius size change correction of a decrease (D-D) in a diameter of the workpiece by grinding and cutting which is measured by a workpiece diameter measuring device 83, and a maximum difference in value of deflection Franging from Θ=0 to Θ=360 is defined as deflection accuracy Fm in the processing part. On the basis of the deflection accuracy Fm, a deflection removal grinding and cutting process is performed.

Description

  The present invention relates to a runout accuracy measuring method and a grinder for measuring runout with respect to the center of rotation of a processed part of a workpiece during grinding.

  In the grinding machine, in order to grind the workpiece with high accuracy and high efficiency, the runout accuracy of the processed part of the workpiece is measured on the machine before the start of runout grinding, and the runout grinding is performed based on the data. There is a related art 1 (see, for example, Patent Document 1).

JP 2004-181537 A

  In Prior Art 1, run-out removal grinding according to run-out amount can be performed, but since grinding is interrupted during run-out accuracy measurement, it takes time to finish grinding.

  The present invention has been made in view of the above circumstances, and a runout accuracy measuring method capable of measuring runout accuracy during grinding, and runout removal grinding can be performed according to the measured runout amount, and wasteful grinding time is not consumed. An object is to provide a grinding machine.

In order to solve the above-mentioned problem, the feature of the invention according to claim 1 is the runout accuracy measuring method for measuring the accuracy of the processed portion during grinding of rotating and supporting a cylindrical workpiece to grind the processed portion.
During one rotation during grinding of the workpiece, the surface position, which is the surface position of the processing part facing the grinding point in the cutting direction of the grinding wheel, and the normal grinding resistance acting at this time Measure at the same time,
The difference between the surface position at the measurement start position and the surface position at a position rotated by a predetermined angle Θ from the measurement start position is defined as a surface change Δs (Θ),
The difference between the normal grinding resistance force at the measurement start position and the normal grinding resistance force at a position rotated by a predetermined angle Θ from the measurement start position is defined as a resistance change ΔR (Θ).
The start position diameter D ₀ that is the diameter of the processed part including the measurement start position and the end position diameter D ₃₆₀ that is the diameter of the processed part including the measurement end position are measured, and the outer diameter dimensional change ΔD is expressed as ΔD = D. Calculate with _0- D ₃₆₀ ,
The bending change Δt (Θ) of the processed part is calculated using the rigidity k of the processed part during grinding and the resistance change ΔR (Θ),
With respect to the surface change Δs (Θ), the deflection Ft (Θ) is corrected by using the deflection change Δt (Θ) and the correction value obtained by apportioning the outer diameter dimensional change ΔD according to the rotation angle Θ. And
The difference between the maximum value and the minimum value of the shake F (Θ) is calculated as the shake accuracy Fm.

A feature of the invention according to claim 2 is a grinding machine for rotating and supporting a cylindrical workpiece and grinding a processing portion by a grinding wheel.
A workpiece diameter measuring part for measuring the outer diameter of the processed part;
A position measuring unit for measuring the position of the surface of the processing unit in the cutting direction of the grinding wheel;
A normal resistance measuring unit for measuring normal resistance during grinding;
During one rotation during grinding of the workpiece, a starting surface position measured by the position measuring unit at a measurement starting position, and a starting normal grinding resistance force simultaneously measured by the normal resistance measuring unit, Using the Θ surface position measured by the position measurement unit at a position rotated by a predetermined angle Θ from the measurement start position, and simultaneously using the Θ normal grinding resistance force measured by the normal resistance measurement unit,
The difference between the starting surface position and the Θ surface position is the surface change Δs (Θ),
The difference between the starting normal grinding resistance and the Θ normal grinding resistance is defined as a normal grinding resistance change ΔR (Θ),
Change calculation for calculating the deflection change Δt (Θ) of the processed portion using the equation Δt (Θ) = ΔR (Θ) / k using the rigidity k of the processed portion and the normal resistance change ΔR (Θ). And
An outer diameter dimensional change ΔD that is a difference between a start position diameter D ₀ that is the diameter of the processed part including the measurement start position and an end position diameter D ₃₆₀ that is the diameter of the processed part including the measurement end position is ΔD = D Calculate with _0- D ₃₆₀ ,
A shake calculation unit that calculates a shake F (Θ) corresponding to the rotation angle Θ using the formula F (Θ) = Δs (Θ) + Δt (Θ) + Θ · ΔD / 720;
A shake accuracy calculation unit that calculates the difference between the maximum value and the minimum value of the shake F (Θ) as the shake accuracy;
A control device for changing the grinding process based on the runout accuracy is provided.

  According to the first aspect of the invention, the displacement change Δs (Θ) of the surface of the machined part in the cutting direction of the grinding wheel measured during grinding and the normal resistance change ΔR (Θ) when measuring the displacement change Δs (Θ) By calculating the radial deflection F (Θ) of the processed part using the outer diameter dimensional change ΔD (Θ) of the processed part and the rigidity k of the processed part, the runout accuracy of the processed part can be measured during grinding.

  According to the second aspect of the invention, the displacement change Δs (Θ) of the surface of the machined part in the cutting direction of the grinding wheel measured during grinding and the normal resistance change ΔR (Θ) when measuring the displacement change Δs (Θ) ) And the outer diameter dimensional change ΔD (Θ) of the processed part and the processed part stiffness k are used to calculate the radial deflection F (Θ) of the processed part, whereby the deflection accuracy of the processed part can be measured during grinding. A grinding machine capable of grinding with a desired accuracy in a short time can be realized by changing the grinding conditions using the measured values.

It is the schematic which shows the whole structure of the grinding machine of this embodiment. It is a B arrow line view of FIG. It is a conceptual diagram which shows the measuring method of this embodiment. It is a graph which shows the concept of the correction | amendment of the outer diameter dimension change of this embodiment. It is a flowchart which shows the grinding process of this embodiment. It is a flowchart which shows the shake measurement process of this embodiment.

Hereinafter, an embodiment of the present invention will be described based on examples of a cylindrical grinding machine with reference to FIGS.
As shown in FIG. 1, the cylindrical grinding machine 1 includes a bed 2, supported on the bed 2 so as to be reciprocable in the X-axis direction and driven by a feed motor 9, and a Z-axis orthogonal to the X-axis. A table 4 capable of reciprocating in the direction is provided. The grinding wheel base 3 rotatably supports the grinding wheel 7, and the grinding wheel 7 is rotationally driven by a grinding wheel shaft rotating motor (not shown). On the table 4, a spindle 5 that grips and rotatably supports one end of the workpiece W and is rotationally driven by a spindle motor (not shown), and a center pusher that rotatably supports the other end of the workpiece W A work table W is provided, and the workpiece W is supported by the main shaft 5 and the tailstock 6 and is driven to rotate during grinding. A measuring device 8 for measuring the processed part of the workpiece W is installed on the table.
As shown in FIG. 2, the measuring device 8 is disposed so as to face the workpiece diameter measuring device main body 831 held by the base 81 fixed to the table and the workpiece diameter measuring device main body 831 at 180 degrees. A workpiece diameter measuring device 83 composed of contacts 832a and 832b, and a capacitance type surface position measuring device fixed to a bracket 82 held by the base 81 and measuring the surface position of the workpiece W in a non-contact manner. 85. The contacts 832a and 832b and the surface position measuring device 85 are arranged at the same position in the axial direction of the workpiece W, and can measure the same part of the processed part.

  The grinding machine 1 includes a control device 30 that executes automated grinding and measurement by executing a predetermined program. As a functional configuration of the control device 30, an X-axis control unit 31 that controls the feed of the grindstone table 3, a Z-axis control unit 32 that controls the feed of the table 4, a spindle control unit 33 that controls the rotation of the spindle 5, and a measuring device 8 includes a measuring device control unit 34 for controlling 8, a calculation unit 35 for performing various calculations, and the like. As a function of the X-axis control unit 31, a normal grinding resistance measurement unit 311 that measures a normal grinding resistance force acting on the grinding wheel 7 during grinding from a current value of the feed motor 9 is provided. Further, as a function of the calculation unit 35, a change calculation unit 351, a shake calculation unit 352, and a shake accuracy calculation unit 353 are provided.

First, an outline of the shake accuracy measuring method of the present invention will be described.
Normally, the runout accuracy is measured by rotating the measured object with reference to a rotation reference such as a center hole, and measuring the runout, which is the amount of variation in radius from the rotation reference center of the surface of the measurement unit, for one rotation. The difference between the minimum values is the runout accuracy.
In order to measure the runout accuracy of the machined part during grinding, it is necessary to correct the deflection variation from the rotation reference of the machined part due to the normal grinding resistance. Further, since the machining allowance is removed in a spiral shape in the processing portion being ground, it has a spiral radius variation, and correction of this radius variation is also necessary. The surface position of the processed part being processed is measured for one rotation, and the above two fluctuations are corrected to measure the runout accuracy.

The details of the runout accuracy measurement during grinding will be described with reference to FIG.
A position in the machining portion of a line connecting the rotation center of the spindle 5 and the center center of the tailstock 6 as the rotation reference of the workpiece W at the measurement start position shown in FIG. When the normal grinding resistance acts on the workpiece W, the rotation center of the processed portion is a point O moved from the point P by the deflection amount t ₀ . When the distance between the point P and the surface position measuring device 85 is u, the distance between the point P and the point O is t _0, and the distance between the surface of the processing portion and the surface position measuring device 85 is s ₀ , the processing portion from the point O The surface radius r ₀ is expressed as r ₀ = u−s ₀ −t ₀ . u is a constant value determined by the arrangement of the measuring device 8, the main shaft 5, and the tailstock 6. t ₀ is the amount of deflection of the processed portion of the workpiece W in the cutting direction of the grinding wheel 7 caused by the normal grinding resistance force. When the rigidity of the processed portion is k and the normal grinding resistance force is R ₀ , t ₀ = It can be calculated by R ₀ / k. The stiffness k can be obtained in advance by measurement or analysis. The normal grinding resistance R is measured by detecting the current value of the feed motor 9 that sends the grindstone table 3 in the normal resistance measurement unit 311 and converting it into the normal grinding resistance R.

Here, the diameter of the processed part is measured by the workpiece diameter measuring device 83, the diameter D ₀ of the processing unit including a measurement start point A located at the point A contact 84a as shown in FIG. 3 (b) Measured when rotating up to. Since the phase difference between the surface position measuring device 85 and the contact 84a is Φ, the measured value of the workpiece diameter measuring device 83 when the workpiece W is rotated by an angle Φ from the time of measuring s ₀ and R ₀ of the point A is a point. This is the diameter of the processed part including A. Measurement end point A ₁ becomes a point at which the radius at point A and the same phase decreased by grinding removal amount of one rotation, the diameter of the working portion including A ₁ is measured when the workpiece from the start of the measurement is rotated (360 + Φ) of The

The surface radius at the measurement start point A and r _0, the r ₀ for each predetermined rotation angle ΔΘ calculated one rotation surface radius to r _n, the diameter of the processed portion including the point A and D _0, after one rotation When the diameter of the working portion including a measurement end point a ₁ and D _360, a graph of surface radius variation as shown in FIG. 4 (a) is obtained. This graph is the difference in _{r n} in the value and the point _{A 1} of _{r 0} at point A in _{(D 0 -D 360)} / 2 correction according to the rotational position is regarded as the radius reduction by grinding removal during one rotation Then, the graph shown in FIG. 4B is obtained. Specifically, the correction amount at the i-th rotational position Θ _i (degrees) from the point A is Θ _i · (D ₀ −D ₃₆₀ ) / 720, and the correction surface radius r _{i at} this time is r _i = u−. It can be calculated as s _i −t _i + Θ _i · (D ₀ −D ₃₆₀ ) / 720.
Here, when calculating the deflection _{F i} of i-th surface to the difference or the point A of the i-th corrected surface radius based on the value of point _{A F i = s i -s 1} + t i -t 1 -Θ i (D ₀ −D ₃₆₀ ) / 720, and the shake can be calculated regardless of u. Difference between the maximum and minimum values of F _i in one revolution of the workpiece W becomes the deflection accuracy Fm.

A grinding process for correcting the runout of the processed part by back-off grinding using this runout measurement process in the grinding machine 1 will be described based on the flowchart of FIG. Here, the back-off grinding means that the grinding wheel 7 is moved backward during grinding, and the workpiece W and the grinding wheel 7 are moved forward again from a position away from the grinding wheel to perform grinding. In this way, only the large runout portion of the machined portion with runout is selectively ground and removed, and the runout can be corrected by minimizing the decrease in the workpiece diameter.
First, in a state where the workpiece W and the grinding wheel 7 is rotated at a predetermined rotational speed, fast forward the grinding wheel 7 until the grinding start position X = X ₀ (S1). The grinding wheel 7 is fed to perform rough grinding (S2) until X = X ₀ −f ₁ which is a predetermined rough grinding finish diameter. Grind for one rotation of the workpiece under the grinding conditions for medium finish grinding. The grinding wheel 7 is fed by Δf ₂ which is the feed amount per rotation of the workpiece (S3). The shake measurement process shown in the flowchart of FIG. 6 is started (S4). It is determined whether or not the runout accuracy Fm measured in the runout measurement process is greater than the allowable value C. If Fm> C, the process moves to S6 to start backoff grinding, and if Fm ≦ C, the process moves to S7 (S5). After moving the grindstone table 3 back to the back-off grinding start position X = X ₀ −f ₁ −3 · Δf ₂ + Fm, the process moves to S 3 (S 6). Medium finish grinding is performed until the diameter of the processed portion of the workpiece W reaches the start of finish grinding (S7). Finish grinding is performed (S8). The wheel head is moved backward to the machining start position X = X ₀ + X _f (S9).

Next, the run-out measuring step in the grinding machine 1 is an example in which 361 surface radii from i = 0 to 360 for one rotation are measured for each degree of rotation (ΔΘ) of the workpiece, and the flowchart of FIG. Based on FIG. 3, it demonstrates concretely with reference to FIG.
First, the rigidity k of the processing part of the workpiece W and the phase difference Φ between the surface position measuring device 85 and the contact 84a shown in FIG. 3B are read into the calculation part 35 (S11). The value of the workpiece rotation angle Θ is reset to 0 and the value of the data count i is reset to 1 in the calculator 35 (S12). As shown in FIG. 3A, the surface position s ₀ of the point A, which is the measurement start position, is measured by the surface position measuring device 85, and at the same time, the normal grinding resistance R ₀ is measured by the normal resistance measuring unit 311. Then, it is recorded in the calculation unit 35 (S13). The workpiece is rotated once (S14). The surface position s _i is measured by the surface position measuring device 85, and at the same time, the normal grinding resistance force R _i is measured by the normal resistance measuring unit 311 and recorded in the calculation unit 35 (Θ = 1 to Φ) (S15). 1 is added to the value of the data count i. i = i + 1 (S16). It is determined whether i ≧ Φ + 1 (the measurement start point A has reached the position of the contact 85a). If i <Φ + 1, the process moves to S14, and if i ≧ Φ + 1, the process moves to S18 (S17). As shown in FIG. 3B, the workpiece diameter D ₀ at the measurement start position point A is measured by the workpiece diameter measuring device 83 and recorded in the computing unit 35 (S18).

The workpiece is rotated once (S19). The surface position s _i is measured by the surface position measuring device 85, and at the same time, the normal grinding resistance R _i is measured by the normal resistance measuring unit 311 and recorded in the calculation unit 35 (Θ = Φ + 1 to 360) (S20). 1 is added to the value of the data count i. i = i + 1 (S21). It is determined whether i ≧ 361 (measurement start point A has made one revolution). If i <361, the process moves to S19, and if i ≧ 361, the process moves to S23 (S22). Resistance change ΔR _i = _R 0 -R _i, deflection change Δt _i = ΔR _i / k, calculates the surface changes Δsi ₌ s 0 -s _i by the change calculation unit 351 records the calculation unit 35 (S23). Simultaneously with the start of S23, the workpiece is rotated by Φ degrees. Here, the calculation time in S26 is shorter than the workpiece rotation time in S24 (S24). As shown in FIG. _3D , the workpiece diameter D ₃₆₀ at the measurement end position point A ₁ is measured by the workpiece diameter measuring device 83 and recorded in the calculation unit 35 (S25). The shake F _i is calculated by the shake calculation unit 352 using the formula F _i = Δsi + Δt _i + i · (D ₀ −D ₃₆₀ ) / 720 (for i = 1 to ₃₆₀ ) (S26). The shake accuracy Fm is calculated by the shake accuracy calculation unit 353 as the difference between the maximum value and the minimum value of F _{1 to} F ₃₆₀ (S27). Simultaneously with the start of S26, the workpiece is rotated (360-Φ) degrees. Here, the calculation time in S26 and S27 is shorter than the workpiece rotation time in S28 (S28).

  As described above, by using the runout accuracy measuring method of the present invention, the runout accuracy of the machined part can be measured without being affected by the normal grinding resistance force during grinding, and an optimum runout grinding process is performed according to the result. Can be implemented. For this reason, the machining allowance for run-off grinding can be minimized, grinding time can be shortened, and wear of the grinding wheel 7 can be reduced.

In the above example, the current value of the grindstone feed motor 9 is detected and the normal grinding resistance is measured. However, a load measuring sensor may be installed on the spindle stock 5 and the tailstock 6 for measurement.
Although the non-contact type surface position measuring device 85 is used, a contact type measuring machine such as a differential transformer type may be used.

W: Workpiece 3: Whetstone stand 4: Table 5: Spindle 6: Tailstock 7: Whetstone wheel 8: Measuring device 9: Whetstone feed motor 30: Control device 35: Calculation unit

Claims (2)

In the runout accuracy measuring method for measuring the accuracy of the processed part during grinding for rotating and supporting the cylindrical workpiece and grinding the processed part,
During one rotation during grinding of the workpiece, the surface position, which is the surface position of the processing part facing the grinding point in the cutting direction of the grinding wheel, and the normal grinding resistance acting at this time Measure at the same time,
The difference between the surface position at the measurement start position and the surface position at a position rotated by a predetermined angle Θ from the measurement start position is defined as a surface change Δs (Θ),
The difference between the normal grinding resistance force at the measurement start position and the normal grinding resistance force at a position rotated by a predetermined angle Θ from the measurement start position is defined as a resistance change ΔR (Θ).
The start position diameter D ₀ that is the diameter of the processed part including the measurement start position and the end position diameter D ₃₆₀ that is the diameter of the processed part including the measurement end position are measured, and the outer diameter dimensional change ΔD is expressed as ΔD = D. Calculate with _0- D ₃₆₀ ,
The bending change Δt (Θ) of the processed part is calculated using the rigidity k of the processed part during grinding and the resistance change ΔR (Θ),
With respect to the surface change Δs (Θ), the deflection Ft (Θ) is corrected by using the deflection change Δt (Θ) and the correction value obtained by apportioning the outer diameter dimensional change ΔD according to the rotation angle Θ. And
A shake accuracy measuring method for calculating a difference between a maximum value and a minimum value of the shake F (Θ) as a shake accuracy Fm. In a grinding machine that rotationally supports a cylindrical workpiece and grinds a processing part with a grinding wheel,
A workpiece diameter measuring part for measuring the outer diameter of the processed part;
A position measuring unit for measuring the position of the surface of the processing unit in the cutting direction of the grinding wheel;
A normal resistance measuring unit for measuring normal resistance during grinding;
During one rotation during grinding of the workpiece, a starting surface position measured by the position measuring unit at a measurement starting position, and a starting normal grinding resistance force simultaneously measured by the normal resistance measuring unit, Using the Θ surface position measured by the position measurement unit at a position rotated by a predetermined angle Θ from the measurement start position, and simultaneously using the Θ normal grinding resistance force measured by the normal resistance measurement unit,
The difference between the starting surface position and the Θ surface position is the surface change Δs (Θ),
The difference between the starting normal grinding resistance and the Θ normal grinding resistance is defined as a normal grinding resistance change ΔR (Θ),
Change calculation for calculating the deflection change Δt (Θ) of the processed portion using the equation Δt (Θ) = ΔR (Θ) / k using the rigidity k of the processed portion and the normal resistance change ΔR (Θ). And
An outer diameter dimensional change ΔD that is a difference between a start position diameter D ₀ that is the diameter of the processed part including the measurement start position and an end position diameter D ₃₆₀ that is the diameter of the processed part including the measurement end position is ΔD = D Calculate with _0- D ₃₆₀ ,
A shake calculation unit that calculates a shake F (Θ) corresponding to the rotation angle Θ using the formula F (Θ) = Δs (Θ) + Δt (Θ) + Θ · ΔD / 720;
A shake accuracy calculation unit that calculates the difference between the maximum value and the minimum value of the shake F (Θ) as the shake accuracy;
A grinding machine comprising a control device for changing a grinding process based on the runout accuracy.

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