JP6553906B2 - Machine tool and its tool rotating device - Google Patents

Description

  The present invention relates to a machine tool, a tool rotation device thereof, and a spindle thermal displacement correction method, and more particularly, to an apparatus for correcting thermal displacement in the rotation axis direction of a tool rotation shaft in a machine tool that performs cutting, grinding, and polishing using a rotary tool. And a method. The rotation axis direction or the turning axis direction is defined so as to call the axis as the rotation axis direction when the object rotates around a certain linear axis.

  In general, in a machine tool that performs cutting using a rotating tool, when the operating state such as the rotation speed of the tool is changed, the heat generation state of the rotary motor and the bearing that freely supports the rotating body and the contact angle of the bearing change. And the position of the cutting edge of the tool is displaced. Among these, especially regarding the change in the heat generation state, the settling time from the change tends to be as long as several hours to several hours (see, for example, Non-Patent Document 1).

  Therefore, conventionally, in general, it takes time from the change of the tool rotation state to the start of machining, so-called warm-up operation, or close rotation speed of rough machining and finishing machining, etc. Measures have been taken, such as devising ways to reduce the impact.

  On the other hand, when time such as warm-up operation cannot be allowed, a method of suppressing the displacement by correction is employed (for example, see Patent Document 1). That is, in the conventional example (first conventional example) described in Patent Document 1, the temperature of a plurality of parts of a machine tool and the machining dimensions of the workpiece are measured, and the change in the measured temperature of the plurality of parts and the machining dimension of the workpiece are measured. The correlation between the changes in the machine tool is obtained by multiple regression analysis, the part of the machine tool whose correlation value obtained by the multiple regression analysis is higher than a predetermined value is selected, the change in temperature of the selected machine tool part and the workpiece The relational expression of the machining dimension change is obtained from multiple regression analysis, the machining dimension of the workpiece is predicted from this relational expression, and the feed rate of the machine tool is corrected based on the predicted machining dimension of the workpiece. Yes. However, in reality, elements other than heat may be displaced, and there is a problem that the displacement component cannot be dealt with. In addition, non-contact displacement meters built into the tool shaft and measuring the displacement of the rotating body are also available on the market, and depending on the machine tool, the function of automatically offset and compensate the displacement based on the output of such a displacement meter. There is also the one having the second prior art.

Sai et al., “Measuring method of thermal displacement of machine tool due to high-speed rotation of spindle”, Journal of Precision Engineering, Vol. 65, no. 3 (1999) 396.

JP-A-8-141883

  However, for example, even in a tool axis rotating device incorporating a displacement meter as in the second conventional example described above, depending on the position where displacement is incorporated, for example, the displacement of the rotating body based on the position of the head is grasped. In the case where such a mechanism that supports such a head is displaced, it is difficult to accurately grasp the displacement around the spindle of the machine tool and correct it. For this reason, development of an apparatus or a method having a higher-performance displacement compensation function that enables accurate grasping and correction processing of the displacement around the spindle of the machine tool has been awaited.

  Furthermore, when a displacement meter is used as in the second conventional example described above, a displacement meter having a large measurement range must be used for a rotational axis that generates a relatively large displacement, and the correction resolution is also maintained. As a result, a high-resolution analog-to-digital converter (ADC converter) is required, resulting in a problem of high costs. For this reason, development of a technique capable of obtaining the same function as described above at lower cost has been awaited.

The present invention has been made under the circumstances as described above, and an object thereof is to provide a technology for providing a low-cost, high-performance axial thermal displacement correction function in a tool rotating device for a machine tool. It is.

As a result of intensive research from various viewpoints on the possibility of the technology for achieving the above-described low-cost and high-performance axial thermal displacement correction function, the inventor of the present invention has found that the heat-related part of the displacement is a serial connection By performing signal processing (shown in the block diagram of FIG. 1 described later) using a series combination of such first-order delay elements to the signal whose displacement has been measured. It has been found that the thermal displacement correction in the axial direction is possible.

That is, in the present invention, a tool rotating device having a rotating shaft and a tool attached to the rotating shaft and rotated by the rotating shaft, and the thermal displacement of the rotating shaft in the tool rotating device in the axial direction in a noncontact manner A machine tool comprising a displacement gauge for detecting, wherein a combination of a predetermined first-order delay element with respect to an output of the displacement gauge is configured to estimate a thermal displacement caused by the tool rotation device. Is obtained.

Further, in the machine tool, further, a probe of the displacement meter in the to be measured displacement gauge target in a portion opposed, intentionally rocking or holes provided for converting the output of the displacement meter and the target An analog-to-digital converter and a digital low pass filter may be provided.

Furthermore, in the present invention, it is also possible to configure as a tool rotation device that utilizes the intentionally provided hole of the target for balance adjustment.

  Needless to say, the signal processing by the combination of the predetermined first-order lag elements may be performed after digital conversion.

  Moreover, the structure which uses the target part without a shake without using the target part which provided the shake and the hole is also possible. Thereby, although a cost is disregarded, a simple configuration can be realized.

Furthermore, the hole of the target of the displacement gauge can also be used as a hole for adjusting the balance of the rotating body which remains as a screw hole and leaves a set screw. Here, the meaning of "use as a hole for balance adjustment" will be briefly described. Heretofore, it has been practiced to correct the unbalance in rotation of the grinding wheel by attaching a weight to a correction surface provided on the grinding wheel flange of the grinding apparatus. For example, when using a grinding device, when attaching a grindstone to a flange, place the grindstone on a static balance table, and if there is uneven mass in the circumferential direction, the heavy (large mass) side is slightly outward due to centrifugal force. As it rotates as it comes, a correction weight is attached to the flange so as to cancel the nonuniformity. That is, “use as a hole for balance adjustment” is a form of such balance adjustment, in which a plurality of holes are provided at equal intervals along the entire circumferential direction at the peripheral portion of the flange. By fixing a correction weight such as a screw or the like in any of the holes, it means that the static imbalance is corrected. As described above, according to the present invention, an intentional vibration component and a hole are provided in a component that is a target of a displacement meter, and a digital low-pass filter is provided for a digital signal after ADC input. Although the influence on compensation can be reduced, by fixing a weight for correction such as a screw in this hole, it can be used as a hole for adjusting the balance of the rotating body to correct the static imbalance.

  The signal processing by the combination of the predetermined first-order lag elements and the digital low-pass filter may be provided with a PLC or special signal processing hardware corresponding to the calculation, or configured by a software program of a numerical control computer (CNC). Also good.

The present invention is not always necessary to compensate for the thermal distortion may be utilized in applications to estimate the stability of the thermal displacement.

According to the present invention, in the tool rotating device of the machine tool, it is possible to correct the thermal displacement in the axial direction after the change in rotational state with higher accuracy or lower cost. In addition, the resolution of the analog-to-digital converter can be improved by providing intentional shake components and holes in the parts to be targets of the displacement gauge and providing a digital low-pass filter to the digital output signal after input to the analog-to-digital converter It is possible to reduce the influence on the thermal displacement compensation due to the shortage.

It is a block diagram showing signal processing given to a displacement signal. It is an example of processing of a displacement gauge target, and an example of displacement gauge installation. It is an example of the displacement meter target of FIG. 2, and the effect of a low pass filter. It is a figure explaining the example of application of this invention. It is a figure explaining the example of application of this invention.

  First, the outline of the present invention will be described with reference to FIGS. 1 to 3. The present invention makes use of the fact that the heat-related part of the displacement acts like a serial combination of the first-order lag elements, and the series connection of the first-order lag elements is used for the signal measuring the displacement. By performing signal processing (shown in the block diagram of FIG. 1), it is possible to perform high-performance axial displacement correction. FIG. 1 is a block diagram showing signal processing that is a feature of the present invention, that is, signal processing using a serial combination of first-order lag elements performed on a signal representing displacement, and FIG. 2 is a diagram of a displacement meter target. FIG. 3 is a diagram illustrating a processing example and an installation example of a displacement meter, and FIG. 3 is a diagram for explaining the effects of the displacement meter target and the low-pass filter of FIG.

  As shown in FIG. 1, in the present invention, an output signal ΔZest (t) representing a processing result is obtained by performing signal processing using a serial combination of first-order lag elements on a signal ΔZsense (t) representing a displacement. Get. Note that the coefficients K1, K2, K3, and K4 in FIG. 1 are correction coefficients for thermal displacement, and some of these K1, K2, K3, and K4 can be set to zero. Further, in the example shown in FIG. 1, a three-stage signal processing system is configured, but it may be configured in more stages. The correction coefficient does not have to be a positive value.

In the present invention, the target for measuring the thermal displacement by the displacement meter is not limited as long as it is a workpiece (workpiece), but as shown in FIG. 2 (a), the target of the displacement meter is processed. Is preferred. That is, in the example shown in FIG. 2A, a plurality of holes 299 are machined at equal intervals along the circumferential direction on the outer edge portion of the annular workpiece 300 that is the target of the displacement meter. An annular workpiece 300 as the target is installed as shown in FIG. 2C, and a displacement meter probe 301 is provided as shown in FIG. FIG. 2 (c) shows the upper half of the cross section around the main axis of the machine tool to which the present invention is applied. FIG. 2 shows a tool clamping device 311, a displacement meter probe 301, and an annular workpiece 300. An arrow AA cross section in (a) is shown, and includes a mechanism portion for rotating the tool while fixing the tool on the left side of the tool clamping device 311.

  As shown in the figure, the displacement meter is installed so that the probe 301 corresponds to the position of the hole 299 of the annular workpiece 300. As shown in FIG. 2B, the displacement meter probe 301 is connected to a controller 302, an analog input module 303, and a programmable controller 304 via a sensor cable 301c. Furthermore, it is connected to a numerical control computer (CNC) 107. A signal detected by the probe 301 of the displacement meter is converted into a voltage by the controller 302 and output, and further converted into a digital signal by the analog input module 303. When this digital signal is input to the programmable controller 304, it passes through a digital filter by a program of the programmable controller 304, and signal processing is performed. The value up to the signal processing by the programmable controller 304 is transferred to the CNC 107, and an offset is automatically given in the Z-axis direction of the machine tool without notifying or notifying an operator (not shown). Compensation for displacement is completed.

  In addition, in the annular workpiece 300 that is the target, a hole 299 is intentionally provided in a portion where the probe 301 of the displacement meter faces, and an analog-digital converter (ADC) that converts the output of the target 300 and the displacement meter. By providing the digital low-pass filter, it is possible to reduce the influence on compensation due to insufficient resolution of the ADC described later. As described above, according to the present invention, an intentional vibration component and a hole are provided in a target component of the displacement meter, and a digital low-pass filter is provided for a digital signal after ADC input, thereby compensating for insufficient resolution of the ADC. To reduce the impact of The positions at which the holes are lined up may be arranged in a range where the probes face each other without any deviation, or may be shifted. The design of the low-pass filter is facilitated by shifting the signal so that a slight signal change appears in the displacement meter output.

  FIG. 3 shows a state in which a signal having a slight shake component and a signal having no shake component are passed through a low pass filter (LPF). FIG. 3A shows only noise, and FIG. 3B shows a case where a signal obtained by adding the controlled shake component and noise passes through the LPF. Thus, the combination of the intentional shake component and the low-pass filter has an effect of hiding the lack of resolution.

  According to the present invention described above, in the tool rotating device of a machine tool, the axial displacement after the change of the rotation state can be used with higher accuracy or lower cost.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. 4 and 5. As shown in FIG. 4, the machine tool 100 according to the present embodiment includes motor drivers 101, 102, 103, 104, and 105 that control driving of each axis, and drivers for these motor drivers 101, 102, 103, 104, and 105. A CNC (computer numerical control) device 107 is provided for controlling each of the axes and numerically controlling the rotational speed, feed rate, etc. of each axis. The CNC (computer numerical control) device 107 includes data for numerical control ( A machining program capable of inputting the specifications of the workpiece in, for example, an interactive format is incorporated. That is, as shown in FIG. 5, the machine tool 100 according to the present embodiment includes five axes composed of three axes of linear motion XYZ and two (axis) directions (not shown) of rotations A and C. A motor driver 101 that drives the head 122, to which the tool rotating device 121 is fixed, in the X-axis direction, a motor driver 102 that drives in the Y-axis direction, a motor driver 102 that rotates in the A-axis direction, A motor driver 103 that drives the work table 112 in the Z-axis direction, a motor driver 104 that rotates in the A-axis (around the X-axis), a motor driver 105 that rotates in the C-axis (around the Z-axis), and a CNC (computer numerical value) Control) device 107, and CNC (computer numerical control) device 107 controls driving of motor drivers 101-105 in each axial direction according to a predetermined machining program. By Rukoto like, the workpiece W can be processed into a desired shape. Needless to say, the CNC (computer numerical control) device 107 can also control the rotational speed of the tool.

The machine tool 100 has a structure as shown in FIG. 5, for example, and is configured such that the tool rotation axis 201 and the Z-axis direction 202 are parallel to each other. Each motor driver is connected to an X-axis motor 111, a Y-axis motor 112, a Z-axis motor 113, an A-axis motor 114, and a C-axis motor 115. Each motor is provided with a detector (not shown) for detecting rotation, and an angle and displacement detector (not shown) is provided for each axis according to the required accuracy to perform servo control. Be able to. As described above, the machine tool 100 having the above configuration further includes the tool rotating shaft 201 and the probe 301 that can detect the displacement in the rotating shaft direction in a non-contact manner with respect to the tool rotating device 121 (see FIG. 2). The displacement caused by the tool rotating device 121 can be estimated by combining the first-order lag element shown in FIG. 1 with respect to the output of the displacement meter. In addition, in the example of FIG. 5, it has the grindstone 209 as a tool.

  The tool rotating device 121 incorporates a probe 301 of a displacement measuring device (displacement meter) shown in FIG. 2, and the signal is converted to a voltage by a controller 302 (see FIG. 2) that outputs a signal detected by the probe as a voltage. After conversion, the analog input module 303 converts it into a digital signal. The digital signal is subjected to digital filter and signal processing in a program of the programmable controller 304. Then, the value up to signal processing by the programmable controller 304 is transferred to the CNC 107, and an offset is automatically given in the Z-axis direction shown in FIG. 5 without notifying or notifying the operator (not shown). Thereby, the correction for the displacement in the Z-axis direction is completed.

201 axis of rotation, 209 tools (grindstones), 121 tool rotation devices,
301 displacement gauge probe, 10, 20, 30 first-order lag elements,
100 machine tools, 300 targets (annular workpieces), 299 holes,
303 Analog to Digital Converter (Analog Input Module),
304 Programmable controller (digital low pass filter)

Claims (3)

A tool rotating device having a rotating shaft, and a tool attached to the rotating shaft and rotated by the rotating shaft, and a displacement gauge for detecting the axial thermal displacement of the rotating shaft in the tool rotating device without contact. A machine tool characterized in that a thermal displacement caused by the tool rotation device is estimated by combining a predetermined first-order delay element with respect to an output of the displacement gauge. Oite the machine tool according to claim 1, further in the portion where the probe of the displacement meter in the to be measured displacement gauge target faces, a shake or holes provided intentionally, the displacement gauge and the target machine tools for the analog-digital converter for converting the output of further comprising a digital low-pass filter. The tool rotation device for a machine tool according to claim 2, wherein the intentionally provided hole of the target is used for balance adjustment.

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