JP4898310B2 - Fine shape processing equipment - Google Patents

Description

  The present invention relates to a fine shape processing apparatus for forming a precise fine shape on the surface of a workpiece.

  Conventionally, a technique for processing a fine shape on the surface of a material has been used in many fields such as an information communication field and a liquid crystal manufacturing field. In these industries, in order to achieve miniaturization, high integration, and high accuracy of products, it is required that fine surface shapes be formed with high aspect ratio and high accuracy. On the other hand, diamond cutting has characteristics suitable for forming a fine surface shape such as a good finished surface, and is therefore used as a main processing technique in these industrial fields together with a high-speed tool positioning device (for example, Patent Document 1).

  Since the fine surface shape formed on the surface of the workpiece is determined by the size of the tool edge, it is necessary to reduce the tool edge to achieve a high aspect ratio. However, in conventional devices such as Patent Document 1, problems that affect shape accuracy such as breakage and wear are more likely to occur as the tool edge becomes smaller. In addition, since it is difficult for the operator to visually determine the contact between the tool and the workpiece, there is a problem that an excessive load is applied to the tool, and damage such as chipping and wear are more likely to occur.

  In particular, in the liquid crystal field, there is a demand for an increase in the fine surface shape in order to cope with an increase in the size of the screen. Since the machining time becomes longer due to the increase in the size of the fine surface shape, it is indispensable in terms of production technology to reduce the load on the tool and to know the state of the tool during the machining.

  In order to respond to such problems and demands, as shown in FIG. 10, the present inventors measured the force applied to the tool 120 to a high-speed tool positioning device used for diamond cutting or the like as a fine shape processing device. The measurement processing integrated device 100 to which the force sensor 150 is attached is proposed (see Japanese Patent Application No. 2004-349434).

JP 2002-166317 A

  Since the force sensor 150 is arranged behind the tool positioning device and is fixed to the base 110 with screws 152 and 154, the force applied to the tool 120 is applied to the force sensor 150 in the measurement processing integrated device 100 shown in FIG. Not only 150 but also screws 152 and 154 are dispersed. For this reason, the sensitivity of the force sensor 150 with respect to the force applied to the tool 120 becomes low, and when trying to measure a minute force applied to the tool 120, it is considered difficult to measure with high accuracy. For this reason, in order to measure the minute force applied to the tool, there is a problem that it is necessary to further improve the measurement accuracy.

  The present invention has been made paying attention to such a conventional problem, and an object thereof is to provide a fine shape processing apparatus capable of measuring a minute force applied to a tool with high accuracy.

  In order to achieve the above object, a fine shape processing apparatus according to the present invention is a fine shape processing apparatus for forming a precise fine shape on the surface of a workpiece, and has a processing portion and a drive portion. The processing unit includes a tool capable of processing the surface of the workpiece, and a force sensor connected to the tool and measuring and outputting a force applied to the tool, and the driving unit includes the workpiece. It is characterized in that the processed portion can be driven relative to the workpiece.

  The fine shape processing apparatus according to the present invention can form a precise fine shape on the surface of the workpiece with a tool by driving the processing portion relative to the workpiece with the drive portion. At this time, by attaching the force sensor to a position relatively close to the tool and connecting it to the tool, it is possible to suppress the force applied to the tool from being distributed to portions other than the force sensor. For this reason, the sensitivity of the force sensor with respect to the force applied to the tool can be increased, and a minute force applied to the tool can be measured with high accuracy.

  By utilizing the output of the force sensor measured with high accuracy, contact between the tool and the workpiece can be detected, and the load on the tool during machining can be reduced to the minimum necessary. Further, it is possible to detect damage such as tool wear or chipping during machining, and it is easy to determine tool replacement, thereby improving productivity. The cutting characteristics of the tool can be examined, the machining conditions can be optimized, and the shape accuracy of the machining can be improved.

  The tool may be any tool as long as it can perform cutting or turning on the surface of the workpiece, such as diamond. The drive unit may drive the machining unit with respect to the workpiece, or may drive the workpiece with respect to the machining unit.

  The fine shape processing apparatus according to the present invention includes a support unit, a displacement sensor, and a control unit, the support unit supports the drive unit, and the drive unit is capable of driving the process unit. The displacement sensor is provided in the support part so as to be able to measure the displacement of the processing part relative to the support part, and the control part is connected to the drive part and measured by the displacement sensor. It is preferable that the drive unit can be feedback controlled based on the displacement. In this case, the tool can be positioned at high speed and with high accuracy by feedback control of the drive unit by the control unit based on the displacement measured by the displacement sensor. The processing accuracy can be further improved by combining the feedback control with the output of the force sensor.

  In the fine shape processing apparatus according to the present invention, the control unit may be capable of controlling the drive unit based on a measured value of the force output from the force sensor. In this case, the position of the tool can be controlled by the measurement value from the force sensor, and productivity and machining accuracy can be further improved. By controlling the drive unit with the control unit so that the measurement value of the force sensor becomes constant, the surface shape of the workpiece can be measured from the displacement of the displacement sensor.

  In the micro-shape processing apparatus according to the present invention, the control unit may include display means provided so as to be able to display a measured value of the force output from the force sensor and a displacement measured by the displacement sensor. . In this case, the measurement values of the force sensor and the displacement sensor can be confirmed. In addition, while confirming the measured value, the machining conditions can be changed and various analyzes can be performed.

  In the fine shape processing apparatus according to the present invention, the force sensor may be capable of measuring forces in three axial directions orthogonal to each other. In this case, the magnitude and direction of the force applied to the tool can be measured in the three-dimensional space.

  ADVANTAGE OF THE INVENTION According to this invention, the fine shape processing apparatus which can measure the micro force added to the tool with high precision can be provided.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1 to 7 show a fine shape processing apparatus according to an embodiment of the present invention.
As shown in FIG. 1, the fine shape processing apparatus 10 includes a support unit 11, a drive unit 12, a processing unit 13, a displacement sensor 14, and a control unit 15.

  As shown in FIG. 1, the support portion 11 includes a cylindrical casing 21 having sensor openings 21 a and 21 b at both ends and a sensor holder 22. The casing 21 has an annular flange portion 21c protruding inward along the front opening 21a. The casing 21 has an annular drive fixing portion 21d protruding inward along the rear opening 21b. The sensor holder 22 has a disc-shaped cap portion 22a having the same diameter as the outer diameter of the casing 21, and a columnar portion 22b provided so as to extend perpendicularly to the surface of the cap portion 22a. The sensor holder 22 is fixed to the casing 21 such that the columnar portion 22b is disposed inside the casing 21 and the cap portion 22a closes the opening 21b behind the casing 21. The sensor holder 22 has a through hole 22c that passes through the center of the cap portion 22a and the center of the columnar portion 22b.

  The drive unit 12 includes a piezoelectric element (PZT) 23 that constitutes an actuator, and a PZT driver (not shown) connected to the piezoelectric element 23. The piezoelectric element 23 has high rigidity and excellent responsiveness, and has a cylindrical hollow shape. The piezoelectric element 23 is inserted into the casing 21 so that the columnar portion 22 is inserted therein, and the rear end is fixed to the drive fixing portion 21 d inside the casing 21 and supported by the support portion 11. The piezoelectric element 23 is disposed such that the outer surface does not contact the inner wall surface of the casing 21 and the inner surface does not contact the columnar portion 22b. The piezoelectric element 23 is adapted to expand and contract along the central axis direction inside the casing 21 by applying a voltage via a PZT driver. The piezoelectric element 23 has nonlinear voltage-displacement characteristics due to hysteresis characteristics and creep characteristics.

  As shown in FIG. 1, the processing unit 13 includes a force sensor 24, an attachment unit 25, a wave washer 26, a tool holder 27, and a tool 28. The force sensor 24 is attached to the tip of the piezoelectric element 23 inside the casing 21. The force sensor 24 can output a measured value of the measured force. The attachment part 25 has a cylindrical holder fixing part 25a and a disk part 25b fixed to the rear end of the holder fixing part 25a. The holder fixing portion 25 a has a diameter slightly smaller than the diameter of the opening 21 a in front of the casing 21. The disk part 25 b has a larger diameter than the holder fixing part 25 a and has substantially the same diameter as the outer diameter of the piezoelectric element 23. The mounting portion 25 has a disk portion 25 b disposed inside the casing 21 so that the holder fixing portion 25 a protrudes from the opening 21 a in front of the casing 21. The attachment portion 25 is disposed so that the force sensor 24 is sandwiched between the disc portion 25 b and the piezoelectric element 23.

  The wave washer 26 has an inner diameter that is substantially the same as the diameter of the opening 21 a in front of the casing 21 and an outer diameter that is substantially the same as the outer diameter of the piezoelectric element 23. The wave washer 26 is attached so as to be sandwiched between the flange portion 21 c of the casing 21 and the disk portion 25 b of the attachment portion 25. The wave washer 26 can apply an arbitrary preload to the force sensor 24 and the piezoelectric element 23. The tool holder 27 has a smaller diameter than the holder fixing portion 25a and is fixed to the tip of the holder fixing portion 25a. The tool 28 is made of diamond and has a fine shape with a sharp cutting edge. The tool 28 can cut or turn the surface 1a of the workpiece 1. The tool 28 is detachably fixed to the center of the tip of the tool holder 27.

  As shown in FIG. 1, the force sensor 24 is connected to the tool 28 via a tool holder 27 and a mounting portion 25. Thereby, the force sensor 24 measures and outputs the force applied to the tool 28. The force sensor 24 may be disposed on the tool holder 27 as long as it is the rear part of the tool 28 or may be directly attached to the tool 28. The drive unit 12 can drive the processing unit 13 with respect to the workpiece 1.

  The displacement sensor 14 is composed of a capacitance type sensor. The displacement sensor 14 is inserted and fixed in the through hole 22c so as to protrude from the tip of the columnar portion 22b of the sensor holder 22. The displacement sensor 14 can measure and output the displacement of the processing portion 13 relative to the support portion 11 by measuring the gap between the protruding tip and the disc portion 25b of the attachment portion 25.

  As shown in FIG. 1, the control unit 15 includes a function generator 29, a lock-in amplifier 30, an AD conversion board 31, a computer 32, and a display unit 33. The function generator 29 is connected to the piezoelectric element 23 and applies a voltage having a predetermined frequency to the piezoelectric element 23 to cause the piezoelectric element 23 to vibrate slightly. The lock-in amplifier 30 is connected to the force sensor 24 and the function generator 29. The lock-in amplifier 30 detects an output signal of a force measurement value output from the force sensor 24. That is, an output signal having the same frequency as that input from the function generator 29 is amplified.

  The AD conversion board 31 is attached to the computer 32, and the lock-in amplifier 30 and the displacement sensor 14 are connected thereto. The AD conversion board 31 converts the output signal of the force sensor 24 amplified by the lock-in amplifier 30 and the output signal of the displacement measured by the displacement sensor 14 from an analog signal to a digital signal, and transmits the digital signal to the computer 32. It is like that. The computer 32 can receive the output signal of the force sensor 24 and the output signal of the displacement sensor 14 via the AD conversion board 31. The computer 32 can perform various analyzes based on the output signal of the force sensor 24 and the output signal of the displacement sensor 14.

  The display means 33 is composed of a monitor connected to the computer 32. The display means 33 can display the force measurement value of the force sensor 24 and the displacement measurement value of the displacement sensor 14 in a table, a graph, a figure, or the like. The display means 33 can display the analysis result obtained by the computer 32.

  The control unit 15 can feedback control the drive unit 12 based on the displacement measured by the displacement sensor 14. That is, the control unit 15 inputs a command value from the computer 32 to a PID controller (not shown) via a DA conversion board (not shown) and also inputs an output signal of the displacement sensor 14. The PID controller compares the command value from the computer 32 with the output signal of the displacement sensor 14 and sends a control signal to the piezoelectric element 23 to feedback control the drive unit 12. The output signal of the displacement sensor 14 is input to the computer 32 via the AD conversion board 31 without using the PID controller, and the computer 32 compares the command value with the output signal of the displacement sensor 14 to calculate the piezoelectric element. The drive unit 12 may be feedback-controlled by transmitting a control signal to 23. The computer 32 can control the drive unit 12 based on the output signal of the force sensor 24.

Next, the operation will be described.
The fine shape processing apparatus 10 can form a precise fine shape on the surface 1 a of the workpiece 1 with the tool 28 by driving the processing portion 13 relative to the workpiece 1 with the driving portion 12. . At this time, the force sensor 24 is connected to the tool 28 via the tool holder 27 and the mounting portion 25, and is closer to the tool 28 than the conventional device shown in FIG. 10 disposed behind the tool positioning device. A force sensor 24 is attached to the position. For this reason, it is possible to suppress the force applied to the tool 28 from being distributed to portions other than the force sensor 24. For this reason, the sensitivity of the force sensor 24 with respect to the force applied to the tool 28 can be increased, and the minute force applied to the tool 28 can be measured with high accuracy. Further, when the same force is measured, the processing force can be measured more directly with higher sensitivity than the conventional apparatus shown in FIG.

  Feedback control of the drive unit 12 by the control unit 15 based on the displacement measured by the displacement sensor 14 can compensate for the hysteresis characteristics and creep characteristics of the piezoelectric element 23, and the tool 28 can be positioned at high speed and with high accuracy. Can be done. Further, the position of the tool 28 can be controlled by the measurement value from the force sensor 24, and productivity and machining accuracy can be improved. By combining the feedback control and the control by the force sensor 24, the machining accuracy can be further improved. The measured values of the force sensor 24 and the displacement sensor 14 can be confirmed by the display means 33. In addition, while confirming the measured value, the machining conditions can be changed and various analyzes can be performed.

  In the conventional integrated measuring and processing apparatus 100 shown in FIG. 10, since the force sensor 150 is disposed behind the tool positioning device, it is necessary to support the tool positioning device in a cantilever manner. For this reason, the rigidity of the whole apparatus has fallen and the apparatus is also enlarged. On the other hand, since the fine shape processing apparatus 10 does not need to support the drive unit 12 and the like in a cantilever manner, the rigidity of the entire apparatus is high and the size can be reduced.

[Contact detection]
The fine shape processing apparatus 10 can detect contact between the tool 28 and the workpiece 1 by using the output of the force sensor 24 measured with high accuracy. That is, when the tool 28 and the workpiece 1 come into contact with each other, the force applied to the tool 28 increases, so that the output of the force sensor 24 increases and the output of the lock-in amplifier 30 also increases. At this time, as shown in FIG. 2, the output of the force sensor 24 from the lock-in amplifier 30 is constantly monitored by the computer 32, and when the predetermined threshold is not exceeded, it is determined that the tool 28 is not in contact. Is further brought closer to the workpiece 1. When the output of the force sensor 24 exceeds the threshold value, it is determined that contact has occurred, and the relative movement between the tool 28 and the workpiece 1 is stopped. In this way, contact between the tool 28 and the workpiece 1 can be detected. Thereby, damage to the tool 28 due to contact with the workpiece 1 can be prevented.

[Detection of tool wear and damage]
Further, by using the output of the force sensor 24 measured with high accuracy, it is possible to detect damage such as wear or chipping of the tool 28 during processing. That is, as shown in FIG. 3, the tool 28 is in contact with the surface 1 a of the workpiece 1 during machining. At this time, when the tool 28 is worn or broken, the contact state changes, so the output of the force sensor 24 changes. By detecting this change, damage such as wear and chipping of the tool 28 during processing can be detected. Thereby, it is easy to determine replacement of the tool 28, and productivity can be improved.

[Measurement of tool wear]
Further, the wear amount of the tool 28 can also be measured. That is, as shown in FIG. 4A, the standard sample 2 is used to measure the contact position between the tool 28 before processing and the standard sample 2. When the tool 28 is worn by processing, the tool 28 does not contact the standard sample 2 at the contact position before processing as shown in FIG. At this time, as shown in FIG. 4C, the tool 28 is moved by the piezoelectric element 23 to contact the standard sample 2, and the displacement from the contact position before processing is measured by the displacement sensor 14, whereby the tool 28 is moved. The wear amount d can be measured. Further, the deviation of the tip position of the tool 28 due to an attachment error when the tool 28 is replaced or an individual difference in the size of the tool 28 can be obtained by the same method.

[Measurement of surface processing shape]
As shown in FIG. 5, the shape of the surface 3 a of the sample 3 can be measured from the displacement of the displacement sensor 14 by controlling the drive unit 12 with the control unit 15 so that the measurement value of the force sensor 24 becomes constant. . In the example shown in FIG. 5, the processed surface 3a of the sample 3 is processed with a sine wave, the wavelength is 50 μm, and the amplitude is 100 nm. Further, the elastic deformation region of the processed surface 3a is within 0.1 nm. At this time, a voltage is applied to the piezoelectric element 23 to make the tool 28 approach the sample 3 stepwise while finely vibrating, and scanning is performed in the X direction while performing feedback control so that the measured value of the force sensor 24 becomes constant. Thereby, the displacement of the displacement sensor 14 becomes the shape measurement result of the surface 3 a of the sample 3. In addition, by using a reference sample whose shape is known in the same manner, the shape of the tip of the tool 28 can be measured, and the processing accuracy can be improved.

[Measurement of tool cutting characteristics]
Further, the cutting characteristics of the tool 28 can be examined by directly inputting the output of the force sensor 24 measured with high accuracy to the AD conversion board 31. Thereby, processing conditions can be optimized, and the shape accuracy of processing can be improved.

[Calibration and sensitivity of force sensor]
In order to compare the force sensor 24 of the fine shape processing apparatus 10 (hereinafter referred to as “force sensor I”) with the force sensor 150 of the conventional integrated measuring and processing apparatus 100 shown in FIG. Another force sensor (hereinafter referred to as “force sensor II”) was attached to the rear of the support portion 11 and the following measurements were performed.

  First, a load is applied to the tool 28 with a weight, and the output voltages (Output Voltage) of the force sensor I and the force sensor II when the load is released by lifting the weight all at once are measured, and the result is shown in FIG. . The force applied to the tool 28 can be calculated from the output voltage of the force sensor I and the force sensor II using the result of FIG.

  Next, the output voltage of the force sensor I and the force sensor II when the piezoelectric element 23 is vibrated at 1 Hz and an amplitude of 20 nm is measured, and a graph of force calculated using the results of FIG. 6 is shown in FIG. As shown in FIG. 7, since the force sensor I is disposed at a position closer to the tool 28 than the force sensor II, it can be seen that the force applied to the tool 28 can be measured with higher sensitivity. As described above, since the force sensor 24 directly receives the force applied to the tool, the fine shape processing apparatus 10 can measure the force with high sensitivity and high accuracy.

[3D measurement]
As shown in FIG. 8, the fine shape processing apparatus 10 may have force sensors 51, 52, and 53 so as to be able to measure forces in three axial directions orthogonal to each other. In the example shown in FIG. 8, the force sensor 51 can measure the force in the X-axis direction in FIG. 8, and the force sensor 52 can measure the force in the Y-axis direction (direction perpendicular to the paper surface of FIG. 8). The force sensor 53 can measure the force in the Z-axis direction in FIG. Thereby, the magnitude and direction of the force applied to the tool 28 can be measured in the three-dimensional space.

  Usually, the Z axis of the fine shape processing apparatus 10 which is the cutting direction of the tool 28 is arranged so as to coincide with the X ′ axis in the radial direction of the cylindrical workpiece 4. In that case, the cutting amount can be given only to the X′-axis of the workpiece 4. On the other hand, as shown in FIG. 9, when the Z axis of the fine shape processing apparatus 10 is tilted by the θ angle with respect to the X ′ axis of the work 4, the cutting amount dx ′ is set on the X ′ axis of the work 4. Not only can the cutting amount dz ′ be given to the Z ′ axis in the axial direction of the workpiece 4 at the same time. Thereby, the cut amount dz obtained by combining the cut amount dx ′ and the cut amount dz ′ can be given to the workpiece 4. Thus, a fine shape that changes in both the radial direction and the axial direction of the workpiece 4 can be created.

  In this case, as shown in FIG. 9, a force Fz in the Z-axis direction and a force Fx in the X-axis direction of the fine shape processing apparatus 10 are applied to the tool 28. At this time, the fine shape processing apparatus 10 can measure Fx by the force sensor 51 and Fz by the force sensor 53. As described above, the force sensors 51, 52, and 53 can measure the force applied to the tool 28 in the three-dimensional space, and can be used to improve the accuracy of the three-dimensional machining shape.

It is sectional drawing which shows the fine shape processing apparatus of embodiment of this invention. It is a flowchart when detecting the contact of the tool and workpiece of the fine shape processing apparatus shown in FIG. It is sectional drawing which shows the use condition in the process of the fine shape processing apparatus shown in FIG. It is a side view which shows the measuring method of the abrasion amount of the tool of the fine shape processing apparatus shown in FIG. It is a side view which shows the measuring method of the surface processing shape of the fine shape processing apparatus shown in FIG. It is a graph which shows the output voltage (Output Voltage) with respect to the load (load) applied to the tool of the force sensor (force sensor I) and the comparative force sensor (force sensor II) of the fine shape processing apparatus shown in FIG. It is a graph which shows the measurement result of the force when vibrating the piezoelectric element of the force sensor (force sensor I) and the comparative force sensor (force sensor II) of the fine shape processing apparatus shown in FIG. It is sectional drawing which shows the modification of the force sensor of the fine shape processing apparatus shown in FIG. It is a side view which shows the use condition of the fine shape processing apparatus shown in FIG. It is sectional drawing which shows the conventional measurement processing integrated apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Workpiece 10 Fine shape processing apparatus 11 Support part 12 Drive part 13 Processing part 14 Displacement sensor 15 Control part 21 Casing 22 Sensor holder 23 Piezoelectric element 24 Force sensor 25 Mounting part 26 Wave washer 27 Tool holder 28 Tool 29 Function generator 30 Lock-in amplifier 31 AD conversion board 32 Computer 33 Display means

Claims (3)

A fine shape processing apparatus for forming a precise fine shape on the surface of a workpiece,
A tool capable of processing the surface of the workpiece, a force sensor for measuring and outputting a force applied to the tool, a first surface to which the tool is attached, and a second surface to which the force sensor is attached And a processing part having a wave washer attached to the first surface ;
A cylindrical hollow piezoelectric element having a first end connected to the force sensor and a second end opposite to the first end; A drive unit capable of relatively driving ,
A first flange portion connected to the wave washer and a second flange portion fixed to the second end portion, and a preload was applied to the force sensor and the actuator by the wave washer. A support part for supporting the drive part in a state;
A displacement sensor disposed in a hollow portion of the piezoelectric element and capable of measuring a displacement of the processing portion with respect to the support portion by measuring a gap formed between the mounting portion and the mounting portion;
A control unit connected to the drive unit and capable of feedback-controlling the drive unit based on a displacement measured by the displacement sensor and a force measurement value output from the force sensor;
A fine shape processing apparatus comprising: The fine shape processing apparatus according to claim 1,
The said control part has the display means provided so that the measured value of the force output from the said force sensor and the displacement measured by the said displacement sensor could be displayed. The fine shape processing apparatus according to claim 1 or 2,
The force sensor is capable of measuring forces in three axial directions orthogonal to each other.

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