JP2006021275A - Machining device, machining method and shape measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform quick measurement, while stably measuring a surface shape of a workpiece ground and machined by using a coolant. <P>SOLUTION: This device has a holding means 6 for holding the workpiece 5, a machining means 7 for grinding and machining the workpiece 5 by using the coolant 8, a shape measuring means 10 for measuring the surface shape of the workpiece 5, a driving means for relatively moving the holding means 6, the machining means 7 and the shape measuring means 10, a coolant temperature measuring means 15 for measuring the temperature of the coolant 8, a workpiece temperature measuring means 16 for measuring the temperature of the workpiece 5, and a holding means temperature measuring means 17 for measuring the temperature of the holding means 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a machining apparatus and a machining method for machining a workpiece formed of an optical element and a molding surface of a mold for molding the optical element, and a shape measuring method for measuring the shape of the machined workpiece.

  When machining an optical element or a molding surface of a mold for molding an optical element as a workpiece, processing is performed using an ultra-precise machine equipped with a numerical control device. Since the above workpieces require high surface accuracy, in order to satisfy this requirement, shape measurement is performed by an external shape measuring machine after processing, and the surface accuracy requirement is not satisfied The shape correction processing is performed by feeding back the measurement result of the shape measuring machine to the processing program.

  FIG. 5 shows a processing apparatus described in Patent Document 1 in order to perform such a shape measurement and shape correction processing cycle with high accuracy and without requiring a long time.

  5 includes a spindle spindle 120 having a holder 110 such as a chuck for holding the workpiece 100, and a tool spindle 140 having a tool 130 such as a grindstone for grinding the workpiece 100. It arrange | positions on the base 150 so that it may oppose. In addition, an on-machine measuring machine 160 that measures the shape of the workpiece 100 ground by the tool 130 is provided on the base 150. The on-machine measuring machine 160 has a probe 170 that comes into contact with the surface of the workpiece 100, and the probe 170 comes into contact with the workpiece 100 rotated together with the spindle 120 by driving the indexing device 180, thereby grinding the workpiece. The shape of the workpiece 100 after processing is measured.

In such a processing apparatus, since the shape of the processed workpiece 100 is measured on the machine, it is not necessary to remove the workpiece 100 from the main spindle 120. For this reason, shape measurement and shape correction processing can be performed with high accuracy in a short time.
JP-A 63-306856

  When processing a workpiece, cutting may be performed while spraying coolant on the workpiece. When the above-described processing apparatus is used for grinding using a coolant, water droplets of the coolant adhere to the workpiece 100, the holder 110 of the workpiece 100, and the spindle 120. When the attached water droplets evaporate, the heat of vaporization at the time of evaporation takes heat energy from the workpiece 100, the holder 110, and the spindle spindle 120, and these temperatures may fall below the ambient temperature.

  When there is such a temperature drop, the temperature drop part shrinks thermally. For this reason, when measurement is started by the on-machine measuring device 160 immediately after processing, there is a problem that the relative position between the workpiece 100 and the on-machine measuring device 160 is fluctuated due to the effect of thermal shrinkage and stable measurement cannot be performed. appear. In addition, in order to perform stable measurement, it is necessary to wait for a certain period of time until the temperature of the workpiece 100 and the holding tool 110 is stabilized after processing, and a new problem that the lead time becomes longer is newly introduced. appear.

  The present invention has been made in consideration of such problems, and can perform shape measurement of a workpiece after machining without waiting for a certain period of time, and can perform stable shape measurement. It aims at providing a processing apparatus, a machining method, and a shape measuring method.

  The machining apparatus according to the first aspect of the present invention includes a holding means for holding a workpiece, a processing means for grinding the workpiece using a coolant, and a shape measuring means for measuring the surface shape of the workpiece. Driving means for relatively moving the holding means, the processing means, and the shape measuring means, a coolant temperature measuring means for measuring the temperature of the coolant, and a workpiece temperature measuring means for measuring the temperature of the workpiece. And holding means temperature measuring means for measuring the temperature of the holding means.

  In machining, the coolant is sprayed on the workpiece to be ground and the holding means for holding the workpiece. Therefore, the temperature of the coolant affects the workpiece and the holding means, and the displacement due to the temperature change is subject to the workpiece. Occurs in the workpiece and holding means. In the first aspect of the present invention, since the temperature measuring means measures the temperature of the coolant used for grinding, the temperature of the workpiece, and the temperature of the holding means, it is possible to cancel the influence of the temperature of the coolant. As a result, even if the shape measuring means measures the surface shape immediately after processing the workpiece, it is possible to perform stable measurement and to reduce the lead time without having to wait for a certain period of time until it becomes stable. .

  A machining method according to a second aspect of the present invention is a machining method comprising a machining step of grinding a workpiece held by a holding means using a coolant, and a shape measuring step of measuring the surface shape of the workpiece. Then, the temperature change of the workpiece is measured with the coolant temperature as a parameter, and at least the coolant temperature at which the workpiece temperature is substantially constant from the end of the machining process to the end of the shape measurement is determined. It is characterized in that a workpiece is processed using a coolant having a temperature substantially equal to this.

  In the invention of claim 2, the coolant temperature at which the temperature of the workpiece from the end of machining to the end of shape measurement is substantially constant is obtained by experiments or the like, and a coolant having a temperature substantially equal to this temperature is used. The workpiece is processed. As a result, the temperature change of the workpiece can be suppressed, so that the temperature difference of the workpiece from the workpiece shape measurement start time to the measurement end time can be extremely small, and the workpiece based on the temperature change can be reduced. The contraction and expansion of the workpiece are extremely reduced, and fluctuations in the measured value can be suppressed. For this reason, it is possible to perform stable shape measurement on the surface of the workpiece.

  According to a third aspect of the present invention, there is provided a shape measuring method comprising a processing step of grinding a workpiece held by a holding means using a coolant, and a shape measuring step of measuring a surface shape of the workpiece. The temperature of the workpiece and the holding means is measured in synchronization with the surface shape measurement of the workpiece, and the measured temperature data, the predetermined physical property value of the workpiece and the predetermined physical property value of the holding means are The surface shape data of the workpiece is corrected.

  In the invention described in claim 3, in order to measure the temperature of the workpiece and the holding means, and to correct the surface shape data of the workpiece from the temperature data and the predetermined physical property values of the workpiece and the holding means, The influence of the coolant on the physical properties of the workpiece and the holding means can be canceled. Therefore, even if the surface shape of the workpiece is measured immediately after processing, stable measurement can be performed, and it is not necessary to wait for a certain period of time until stabilization, and the lead time can be shortened.

  The invention according to claim 4 is the shape measuring method according to claim 4, wherein the predetermined physical property value includes at least a thermal expansion coefficient of the workpiece and a thermal expansion coefficient of the holding means.

  In the invention according to the fourth aspect, since the physical property value of the workpiece and the holding means is used as the thermal expansion coefficient, the displacement of the workpiece and the holding means due to the temperature of the coolant can be canceled reliably.

  The invention according to claim 5 is the shape measuring method according to claim 4, wherein the surface shape of the workpiece is measured when the workpiece exhibits a predetermined constant temperature, and the surface shape data and the workpiece are measured. A value obtained by calculation using the temperature data of the object and the temperature data of the holding means is used as the predetermined physical property value.

  In the invention according to claim 5, since the value obtained from the surface shape data of the workpiece and the temperature data of the workpiece and the holding means is used as the physical property value, the displacement of the workpiece and the holding means due to the coolant temperature. Can be canceled reliably.

  According to the machining apparatus of the present invention, since the temperature of the coolant, the temperature of the workpiece, and the temperature of the holding means are measured, the influence of the coolant temperature on the workpiece can be canceled, and the workpiece is processed. Even if the shape measuring means measures the surface shape immediately after that, it is possible to perform stable measurement, and it is not necessary to wait for a certain time until it becomes stable, and the lead time can be shortened.

  According to the machining method of the present invention, since the workpiece is processed using a coolant having a temperature at which the temperature of the workpiece becomes substantially constant, the workpiece is processed from the shape measurement start time to the measurement end time. The temperature difference between objects can be made extremely small, and fluctuations in measured values based on temperature changes can be suppressed. For this reason, the shape measurement of the surface of a workpiece can be performed stably.

  According to the shape measuring method of the present invention, since the surface shape data of the workpiece is corrected from the temperature data of the workpiece and the holding means and the predetermined physical property values of the workpiece and the holding means, the workpiece is processed immediately after the processing. Even if the surface shape of an object is measured, stable measurement can be performed, and it is not necessary to wait for a certain period of time until the object becomes stable, and the lead time can be shortened.

  Hereinafter, the present invention will be specifically described with reference to embodiments illustrated in the drawings. In each embodiment, the same members are assigned the same reference numerals.

(Embodiment 1)
1 to 3 show a first embodiment of the present invention, FIG. 1 is a plan view of a machining apparatus, FIG. 2 is a flowchart for measuring a shape, and FIG. 3 is a graph showing temperature and time during surface shape measurement. It is a graph which shows a relationship.

  The machining apparatus shown in FIG. 1 is an ultra-precision machining lathe 1 as a machine tool for machining an optical element or a mold for molding an optical element. This super-precision lathe 1 is a machine as a shape measuring means for measuring the surface shape of a spindle 5 having a spindle rotation axis A, a tool spindle 4 having a tool rotation axis B, and a processed workpiece 5. The upper measuring machine 10 is arranged on the base 1a.

  The spindle spindle 3, the tool spindle 4 and the on-machine measuring machine 10 are controlled to move relative to each other by driving means. In other words, the drive means includes two axes of a parallel axis Z parallel to the spindle rotation axis A and a vertical axis X orthogonal to the spindle rotation axis A as operation axes for moving the spindle spindle 3 and the tool spindle 4 relative to each other. . For the on-machine measuring machine 10, the driving means includes a slide (not shown) that moves in a direction parallel to the parallel axis Z.

  A workpiece gripping tool 6 as a holding means for gripping the workpiece 5 is attached to the tip of the spindle spindle 3. In this case, the coefficient of thermal expansion of the gripping tool 6 is made known by using one type of material for the gripping tool 6. A tool 7 as a processing means for grinding the workpiece 5 is attached to the tip of the tool spindle 4.

  Reference numeral 21 denotes a coolant nozzle. The coolant nozzle 21 discharges the water-soluble coolant 8 for improving the temperature stability and slipperiness of the workpiece 5 and the tool 7 during the grinding process. The workpiece 5 is sprayed. As will be described later, the coolant 8 is discharged to the tool 7 and the workpiece 5 in a state in which the temperature is controlled.

  The on-machine measuring machine 10 includes a probe 22 that contacts the workpiece 5 at the tip of a slide that moves in a direction parallel to the parallel axis Z. The probe 22 measures the surface shape of the workpiece 5 by contacting the surface of the workpiece 5. A scale that measures the amount of movement of the slide is attached to the slide. A personal computer 13 that captures the amount of movement of the probe 22 obtained from this scale and the coordinates of the vertical axis X and parallel axis Z at that time as on-machine measurement data is connected to the on-machine measuring machine 10 via a cable 14. The personal computer 13 is provided with software storing a program for executing a flow chart shown in FIG. 2 that can analyze the shape from the above data and express an error from the ideal shape as point sequence data.

  A coolant thermocouple 15 as a coolant temperature measuring means for measuring the liquid temperature of the coolant 8 is disposed in the discharge portion of the coolant nozzle 21. Further, a gripping tool thermocouple 17 as a holding means temperature measuring means for measuring the temperature of the gripping tool 6 after grinding is attached to the gripping tool 6, and the workpiece for measuring the temperature of the workpiece 5 after grinding. A workpiece thermocouple 16 as temperature measuring means is attached to the workpiece 5. In addition to this, a reference block 18 is disposed at a position outside the base 1a where no coolant is applied, and a reference block thermocouple 19 for measuring the temperature of the block 18 is attached to the reference block 18. . In order to collect the temperatures of the coolant thermocouple 15, the gripper thermocouple 17, the workpiece thermocouple 16, and the reference block thermocouple 19, these are connected to the personal computer 13 via the cable 14.

  FIG. 2 shows a flowchart executed by a program stored in software installed in the personal computer 13. In this software, physical property data 20 of the workpiece 5 and the gripping tool 6 is input in advance. This physical property data 20 is composed of the size of each of the workpiece 5 and the gripping tool 6 and the thermal expansion coefficient. And the thermal expansion amount D of the to-be-processed object 5 and the holding tool 6 can be calculated by the following conversion formula C using the physical property data 20 with a program from the temperature data by which temperature was collected. Further, the software has a function of subtracting the thermal expansion amount of the workpiece 5 from the measurement data 9 of the on-machine measuring machine 10.

(Conversion formula C)
Thermal expansion amount D = shape coefficient α × shape size h × thermal expansion coefficient γ × [workpiece temperature (or gripping tool temperature) T−reference block temperature T0]

  Next, shape measurement according to this embodiment will be described with reference to FIG.

  The spindle spindle 3 and the tool spindle 4 are rotated while the workpiece 5 is gripped by the gripping tool 6. Further, in a state where the coolant 8 is applied to the workpiece 5, the workpiece 5 and the tool 7 are relatively moved so that the workpiece 5 has a target shape, and the grinding process proceeds. After grinding, the surface shape of the processed surface of the workpiece 5 is measured by the on-machine measuring machine 10 (step S1).

  Simultaneously with the measurement of the surface shape, temperature measurement by the workpiece thermocouple 16 and the gripper thermocouple 17 and temperature measurement of the reference block 18 by the reference block thermocouple 19 are started (step S4). In this case, the temperature measurement is performed so as to be related to the position coordinate of the vertical axis X of the shape measurement. Then, the temperature measurement is ended simultaneously with the end of the shape measurement (step S2 and step S5), and these data are collected (step S3 and step S6).

  Thereafter, for the workpiece 5, the temperature data of the workpiece thermocouple 16 measured for each point on the vertical axis X is used as the displacement amount (thermal expansion amount) of the workpiece 5 using the physical property data 20. Conversion is performed (step S7). The vertical axis X of the temperature measurement and the vertical axis X measured by the on-machine measuring machine 10 are made coincident, and the displacement amount of the workpiece 5 at that point is subtracted from the measurement data measured by the on-machine measuring machine 10 for correction. Perform (step S8).

  Similarly, for the gripping tool 6, the temperature data of the gripping tool thermocouple 17 is converted into the displacement amount of the gripping tool 6 using the physical property data 20 (step S7). The vertical axis X of the temperature measurement and the vertical axis X measured by the on-machine measuring machine 10 are matched, and the displacement of the gripping tool 6 at that point is subtracted from the measurement data measured by the on-machine measuring machine 10 for correction. (Step S8).

  The shape analysis is performed on the measurement data corrected as described above (step S9), and the shape error is visually displayed on the display of the personal computer 13 as a graph. If the shape error does not satisfy the standard, the shape error is fed back to the machining program and correction processing is performed. On the other hand, when the shape error satisfies the standard, the processing is terminated.

  According to such an embodiment, when measuring the surface shape of the workpiece 5 by the on-machine measuring machine 10, the on-machine measurement is performed in order to correct the displacement due to the temperature of the processed workpiece 5 and the gripping tool 6. Measurement by the machine 10 can be performed stably. In addition, since the measurement can be started immediately after the processing without waiting for a certain time until the displacement amount of the workpiece 5 or the gripping tool 6 is stabilized after the processing, the lead time can be shortened.

(Embodiment 2)
In this embodiment, as in the first embodiment, the workpiece 5 is machined using the ultra-precision machining lathe 1 shown in FIG. 1 as a machining device. It differs in that it sets the temperature.

  FIG. 3 shows temperature changes at measurement points of the workpiece 5 and the gripping tool 6 that are measured after the machining of the workpiece 5 is completed. When the liquid temperature of the coolant 8 and the environmental temperature are different, the workpiece 5 and the gripping tool 6 transition to the environmental temperature after the processing is completed. The solid line in FIG. 3 is, for example, the case where volatile coolant 8 is used. In this case, the temperatures of the workpiece 5 and the gripping tool 6 decrease with time due to the heat of vaporization when the coolant 8 evaporates. Finally, the ambient temperature is reached. The dashed-dotted line in FIG. 3 is a case where the low temperature coolant 8 is used, for example, and the temperature of the to-be-processed object 5 and the holding tool 6 rises with time, and finally becomes environmental temperature. Therefore, in any case, as shown in FIG. 3, a temperature gradient is generated from the measurement start time to the measurement end time of the surface shape of the workpiece 5, and the workpiece is processed based on this temperature change. It shrinks and expands.

  In this embodiment, before processing the workpiece 5, the temperature of the coolant 8 is obtained in advance by experiments or the like, and the workpiece 5 is processed using the coolant 8 at the determined temperature. That is, in the experiment, the coolant 8 is applied to the workpiece 5 and the gripping tool 6 to adjust the workpiece 5 and the gripping tool 6 to the temperature of the coolant 8, and then the coolant 8 is stopped. The temperature of the coolant 8 at which a temperature gradient between the workpiece 5 and the gripping tool 6 does not occur is obtained from that time until a certain time.

  And the workpiece 5 is processed using the coolant 8 of the temperature calculated | required by this experiment, and the surface shape of the workpiece 5 is measured with the on-machine measuring machine 10 after a process. Thereby, since the temperature difference of the workpiece 5 from the measurement start time to the measurement end time can be extremely reduced, the shape change such as contraction and expansion of the workpiece 5 due to the temperature change is extremely reduced. , Fluctuations in measured values can be suppressed. Therefore, stable shape measurement can be performed on the surface of the workpiece.

  In this embodiment, the influence of the temperature of the coolant 8 is also taken into consideration for the gripping tool 6 of the workpiece 5. However, when the temperature of the workpiece 5 is constant, generally the gripping is performed. Since the temperature of the tool 6 is also constant, it is not necessary to consider the influence of the gripping tool 6.

(Embodiment 3)
FIG. 4 shows Embodiment 3 of the present invention. In this embodiment, before the workpiece 5 is ground, the temperature of the workpiece 5 is measured in advance using the workpiece thermocouple 16 and the displacement amount at that time is set parallel to the parallel axis Z. Measured using the Microsense 23. Then, the relationship between the temperature and the displacement amount in the workpiece 5 is stored in the personal computer 13 as the physical property data 20.

  Similarly, the temperature of the gripping tool 6 is measured using the gripping tool thermocouple 17. At this time, the displacement amount in the direction parallel to the parallel axis Z is also measured using the microsense 23. The measured relationship between temperature and displacement in the gripping tool 6 is stored in the personal computer 13 as physical property data 20. The above is the difference from the first embodiment.

  In this embodiment, a temperature that matches the temperature data of the workpiece thermocouple 16 measured for each point on the vertical axis X is searched from the physical property data 20, and the displacement amount of the workpiece 5 at that time is derived. Similarly, for the gripping tool 6, the temperature matching the temperature data of the gripping tool thermocouple 17 is searched from the physical property data 20, and the displacement amount of the gripping tool 6 at that time is derived. This is a difference from the first embodiment in which the value of the thermal expansion coefficient described in the literature is used as the physical property data 20. As a result, in this embodiment, it is possible to carry out corrections that are more practical than in the first embodiment.

It is a whole top view of the machining apparatus in Embodiment 1 of this invention. It is a flowchart for performing the shape measurement of a workpiece. 6 is a graph showing a relationship between temperature and time in surface shape measurement in the second embodiment. FIG. 10 is a plan view of a machining apparatus in a third embodiment. It is a front view of the conventional processing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lathe for ultra-precision machining 3 Spindle spindle 4 Tool spindle 5 Work piece 6 Gripping tool 7 Tool 8 Coolant 10 On-machine measuring machine 13 Personal computer 15 Coolant thermocouple 16 Workpiece thermocouple 17 Gripper thermocouple 18 Reference block 19 Reference Block thermocouple

Claims (5)

  A holding means for holding the workpiece; a processing means for grinding the workpiece using a coolant; a shape measuring means for measuring the surface shape of the workpiece; the holding means, the processing means, and the shape measuring means; Driving means for relatively moving the coolant, coolant temperature measuring means for measuring the temperature of the coolant, workpiece temperature measuring means for measuring the temperature of the workpiece, and holding means for measuring the temperature of the holding means A machining apparatus comprising temperature measuring means. In a processing method comprising a processing step of grinding a workpiece held by a holding means using a coolant, and a shape measuring step of measuring the surface shape of the workpiece,
Measure the temperature change of the workpiece with the temperature of the coolant as a parameter, and obtain the coolant temperature at which the temperature of the workpiece is substantially constant at least from the end of the machining process to the end of the shape measurement, A machining method characterized in that a workpiece is machined using a coolant having a temperature substantially equal to this. In a measuring method comprising a processing step of grinding a workpiece held by a holding means using a coolant, and a shape measuring step of measuring the surface shape of the workpiece,
The temperature of the workpiece and the holding means is measured in synchronization with the measurement of the surface shape of the workpiece, and the workpiece is determined from the measured temperature data, the predetermined physical property value of the workpiece, and the predetermined physical property value of the holding means. A shape measuring method comprising correcting surface shape data of an object.   5. The shape measuring method according to claim 4, wherein the predetermined physical property value includes at least a thermal expansion coefficient of the workpiece and a thermal expansion coefficient of the holding means.   Obtained by measuring the surface shape of the workpiece when the workpiece exhibits a predetermined constant temperature, and calculating using the surface shape data, the temperature data of the workpiece, and the temperature data of the holding means The shape measuring method according to claim 4, wherein the value is the predetermined physical property value.

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