JPH11207573A - Tool dimension measuring method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noncontact type tool dimension measuring method that measures tool dimensions, or the length, diameter and taper angle of a tool, precisely and practically without causing any contact of its probe with the tool that is still held in its machining or positively rotating state. SOLUTION: While a tool 8 attached to a main spindle 7 on a machining center is rotated as in normal machining, an electric potential difference is applied between the tool 8 and a probe 11 having a chamfered ridge. In this sate a conduction sensor 10 detects the electrical conduction made by a discharge in this noncontact state and outputs the data to a numerical controller, which in turn reads the coordinate value of the main spindle to compute the length, diameter and tape angle of the tool.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring a tool length and a tool diameter, which are tool dimensions of a working tool used for a machine tool such as a machining center, and more particularly to a non-contact type measuring method.

[0002]

2. Description of the Related Art Conventionally, as a method of measuring a tool size, a method in which a spindle of a machine tool equipped with a tool is stopped while the spindle is stopped.
There is a method of measuring the position of the spindle by making contact with a measuring element having a pressure-sensitive touch sensor to establish electrical continuity. However, according to the conventional measuring method, as shown in FIG. 8, when the main shaft 7 rotates (forward rotation) during machining, the tool 8 has a slight external expansion and contraction and runout, so that the outer shape of the tool 8 is changed to a rotary tool 8 '( (Extremely expressed), errors may occur when the dimensions of the tool length and the tool diameter are compared with the dimensions at the time of stop. The measured pressure is 30
Since it is as large as 0 to 500 g, especially small diameter (for example, φ0.1
(0.2mm), the tool may bend, causing high-precision measurement. In addition, the contact between the contact point and the tool may cause wear of the contact point, wear of the cutting edge of the tool, and damage such as chipping. Therefore, there have been problems such as a decrease in machining accuracy or breakage of the tool.

In order to solve the above-mentioned problems, Japanese Patent Application Laid-Open Nos. 64-16353 and 64-1633 have been proposed.
No. 54 has been disclosed. That is, when an NC machine tool (for example, a machining center) body is used as a conductor and a tool comes into contact with a probe, a touch signal is output from a touch sensor disposed below the probe that moves flexibly left and right downward, and the touch signal is output. The NC device performs signal processing, calculation, storage, etc. based on the above, and measures the tool length and the tool diameter, which are tool dimensions.

[0004]

However, even in the above-mentioned conventional example, for example, the spindle must be stopped when measuring the tool length, and the spindle is rotated (reverse rotation) when measuring the tool diameter. However, since the tool and the probe eventually come into contact with each other, bending, scratches, and abrasion occur, resulting in reduced durability of the tool and the probe. In addition, the measurement accuracy of the tool length and the tool diameter, which are the tool dimensions, was reduced due to the bending, scratching, and wear, and as a result, the processing accuracy of the product (work) was reduced.

Further, in the above-mentioned conventional example, it was impossible to measure the diameter of the tapered tool. On the other hand, as a non-contact type tool dimension measurement method that does not contact the tool and the measuring element, a measurement method using a magnetic sensor or an optical sensor is also known.However, the resolution of the sensor itself is insufficient, There are problems such as the influence of magnetization of tools and products at the time of processing, and a decrease in reflected light due to contamination of machine oil or the like, and this is not suitable for high-precision measurement.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to measure a tool while rotating the tool in the same state as the machining state while rotating the tool forward. A highly accurate and practical non-contact tool dimension measurement method that can measure the tool length and tool diameter, which are tool dimensions, without contacting the probe, and can also measure the diameter and taper angle of tapered tools. To provide.

In order to complete one product (work) using an NC (numerical control) device, a plurality of tools must be
Since it is used by changing with a TC (automatic tool changer), the dimensional accuracy of a single tool is also important, but rather the cumulative error between a plurality of used tools has a greater effect on the size of a product (work). Often viewed as a quality problem. Therefore, if the dimensions of a plurality of tools exchanged and used by an ATC (automatic tool changer) can be measured quickly with high accuracy,
As a result, a high-quality, low-cost product (work) is provided.

[0008]

In order to achieve the above object, a method for measuring a tool size according to the present invention is characterized in that a potential difference is provided between a spindle of a machine tool and a table, and the tool is attached to the spindle. In the method for measuring the size of the tool by detecting the relative position between the tool and the measuring element fixed to the table by electrical conduction, the detection is performed in a non-contact state between the tool and the measuring element. It is characterized by capturing the phenomenon.

Further, at a position close to the upper surface of the tracing stylus perpendicular to the main axis while rotating the tool, the tool length is determined based on the position in the main axis direction detected while relatively moving the main axis in the radial direction. It is characterized by measuring.

Further, at a position close to a side surface parallel to the main axis of the tracing stylus while rotating the tool, at a radial position detected while relatively moving the main axis in a radial direction parallel to the plane. The tool diameter is measured based on the tool diameter.

Further, the rotation of the tool at the time of measurement is substantially the same as the rotation at the time of machining.

Further, the diameter of the tapered tool is measured by using a measuring element having an R formed at a ridge line between an upper surface of the measuring element perpendicular to the main axis and a side surface parallel to the main axis.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for measuring a tool size according to the present invention will be described below with reference to the drawings. First, an example of an apparatus for carrying out the present invention will be described with reference to FIGS. FIG. 1 is a schematic perspective view showing an example of an apparatus according to the present invention, FIG. 2 is an explanatory view of the principle of a conduction sensor, FIG. 3 is a perspective view of a tracing stylus, and FIG.
FIG. 3 (b) has R of two kinds of dimensions.

Referring to FIG. 1, a machining center 1 as a machine tool is disclosed in Japanese Patent Laid-Open Publication No.
And has the same configuration as the machining center disclosed in Japanese Patent Application Laid-Open No. 64-16354 and its detailed description is omitted. First, a bed 3 is provided on the bed 2 and is movable in the Y-axis (arrow Y) direction, and is supported by the column 4 and the beam 5 and is movable in the X-axis (arrow X) direction.
And a main shaft 7 provided on the saddle 6 and movable in the Z-axis (arrow Z) direction. At the lower end of the main shaft 7, a tool 8 according to the processing content is mounted. And
Reference numeral 9 denotes an ATC, which takes out a required tool from a tool magazine 9a installed on the back of the machining center 1,
It is mounted on the main shaft 7. Reference numeral 20 denotes an NC device which controls the machining center 1 and the ATC 9 to perform required machining operations, and reads coordinates of the table 3, the saddle 6, the main shaft 7 and the like as appropriate.

As shown in FIG. 2, a potential difference V is applied between the main shaft 7 and the table 3 with the main shaft 7 as a positive electrode and the table 3 as a negative electrode.
A known conduction sensor 1 composed of a detection coil 10A and a detection coil 10B.
0 is provided. The conduction sensor 10 and the NC device 20 are electrically connected via a control amplifier 21. A closed loop circuit 10C is formed at the moment when a discharge phenomenon occurs due to a potential difference V between the tool 8 mounted on the main shaft 7 and a tracing stylus 11 to be described later. The current is detected and amplified by the control amplifier 21 and transmitted to the NC device 20 as a conduction signal. Then, the NC device 20 reads the coordinates of the spindle 7 at that time, and performs processing, calculation, storage, and various operation commands of the conduction signal.

Further, as shown in FIG.
Reference numeral 1 denotes a substantially rectangular parallelepiped measuring element attached and fixed to the table 3 via a stay 12, and an upper surface 11A, which is a plane perpendicular to the Z-axis direction of the main shaft 7, and a ridge portion 1 between the upper surface 11A.
1C has one side 11B which is a plane perpendicular to the Z axis and parallel to the Y axis and connected to the other side 11B ', which is also mirror-finished. Have been.

Next, a method of measuring a tool length according to the present invention, which is performed by the machining center 1 configured as described above, will be described with reference to the drawings. FIG. 4 is a diagram illustrating the principle of measuring the tool length when viewed from the front of the machining center 1, that is, from the Y-axis direction.
FIG. 5 is a flowchart showing a basic procedure for measuring the tool dimensions.

In FIG. 4, the space directly above the upper surface 11A of the tracing stylus 11 will be referred to as the territory of the tracing stylus. s is a discharge gap when a discharge phenomenon occurs between the rotating tool 8 ′, which is the rotating tool 8, and the tracing stylus 11, and its magnitude can be arbitrarily set to some extent by the applied potential difference V.
In the present embodiment, it is set to 0.5 μm and the NC device 20 is set in advance.
It is stored in. Therefore, the conduction sensor 10 can quickly output a conduction signal without contact between the tool 8 and the tracing stylus 11.

First, the main shaft 7 is rotated in the same state as during machining, and the tool 8 is turned into a rotary tool 8 '(step S in FIG. 5).
1) Then, the rotary tool 8 'is out of the airspace of the tracing stylus 11,
Standby where the X-axis coordinate does not interfere with the tracing stylus 11, the X-axis coordinate is an arbitrary value (not shown) within the width of the side surface 11 </ b> B of the tracing stylus 11, and the Z-axis coordinate is any value Z4 above the tracing stylus 11 It is made to stand by at a position (step S2).

Next, the main shaft 7 is lowered to a predetermined Z5 such that the Z-axis coordinate has a gap t between Z4 and the height Z2 of the plane 11A while maintaining the X and Y coordinates (vertical movement). ), And this is set as a reference position for measurement (step S3). In this case, the position of the tip of the tool 8 is measured by the conventional tool length measuring method of JP-A-64-16353, and
The gap t is set with reference to Z2, which is the height position of the known plane 11A. Here, the size of the gap t is the discharge gap s
It is a meaningful value that is set appropriately as a value that is sufficiently larger and does not unnecessarily prolong the measurement time.
It is 5 μm.

Next, while maintaining the Y and Z coordinates of the measurement reference position, the rotary tool 8 'is moved from the X coordinate X1 of the measurement reference position to the X coordinate X2 of an arbitrary measurement position previously set on the upper surface 11A of the tracing stylus 11. (Step S4), and it is checked whether or not the discharge phenomenon has occurred, that is, whether the conduction sensor 10 has been detected (Step S5). When there is no detection, the rotary tool 8 'is moved to the Z position at the measurement reference position.
With the axial direction as the movement axis, minute feed is performed so as to approach the tracing stylus 11 (step S6).

Then, the fine feed (for example, 0.5 μm)
m) After that, the rotary tool 8 'is reciprocated from X1 to X2 in the X-axis direction (step S4) while maintaining the Z-axis coordinates, and the detection of the conduction sensor 10 is checked again (step S5). In this way, the minute feed (step S6) and the reciprocating movement from the coordinates X1 to X2 (step S4) are repeated until the conduction sensor 10 detects. When the tip of the rotating tool 8 'enters the discharge gap s, the rotating tool 8'
A discharge phenomenon occurs between the contact sensor 11 and the
0 generates a conduction signal upon detection. The Z-axis coordinates at this time are stored in the NC device 20 (step S7).

When the measurement of the sensor detection position Z3 is completed, the measurement result is calculated and stored according to a formula described later (step 8), and the tool length measurement is completed. If the conduction signal is not detected even after a predetermined distance from the measurement reference position, the program is determined to be abnormal and an alarm is sounded.

Here, the Z-axis coordinate Z1 on the upper surface of the table 3 is
The Z-axis coordinate Z2 of the upper surface 11A of the tracing stylus 11 is known in advance, and therefore, the distance | Z1-Z2 | is a known value. Then, the coordinate displacement moved until the tip of the rotary tool 8 'descends from the height Z4 at the standby position and discharges near the upper surface 11A of the tracing stylus 11 to generate a conduction signal is | Z3.
−Z4 |, | Z1-Z4 | = | Z1-Z2 | +
The formula of s + | Z3-Z4 | holds, and if the moving distance | Z3-Z4 | of the rotary tool 8 'is measured, the coordinate displacement | Z1-Z4 | as the tool length can be calculated by the above formula.

In the above embodiment, the "tool length" is the height | Z from the upper surface of the table 3 to the tip of the rotary tool 8 '.
1-Z4 | (tool height at standby position) is measured as "tool length". When "tool length" is interpreted in a narrow sense, it means the length between both ends of the tool indicated by H in FIG. 4, but in the machining operation, the tool height |
It is common to measure Z1-Z4 | and calculate the distance from this height position to the product (work). In a broad sense, the measurement of | Z1-Z4 | is also referred to as "tool length measurement". In the present embodiment, “tool length” is broadly considered.

Next, a method for measuring a tool diameter according to the present invention using the above-described apparatus will be described with reference to the drawings. FIG. 6A is a schematic front view of a main part showing an operation of measuring a tool diameter according to the present invention, and FIG. 6B is a schematic plan view of the main part. FIG. 5 is a process flowchart in the case of tool diameter measurement.
Since this is the same as that of FIG.

As in the case of the measurement of the tool length, first, the main shaft 7 is rotated in the same state as in the machining, and the tool 8 is set as the rotary tool 8 '(step S1 in FIG. 5). 11 and the X coordinate is the side surface 11B (X coordinate X
6B, X3 and Y coordinates apart from the tracing stylus 11 are arbitrary positions Y1 and Y coordinates outside the width of the side surface 11B as shown in FIG. 6B. It is moved to the standby position (step S2). Here, the size of the gap w is sufficiently larger than the discharge gap s and is a value appropriately set as a value that does not unnecessarily prolong the measurement time, and is 15 μm here.

Next, as shown in FIG. 6A, while holding the X and Y coordinates from the standby position, the tip of the tool 8 'is moved to the Z-axis coordinate Z6 within the height range of the plane portion of the side surface 11B. The main shaft 7 is lowered (moved vertically) (step S3), and this is set as a measurement reference position.

Next, from this measurement reference position, the rotary tool 8 '
Is reciprocated in parallel with the side surface 11B from the Y1 coordinate to the measurement position Y2 set in advance within the width of the side surface 11B of the tracing stylus 11 while holding the X and Z axis coordinates (step S4).
Then, it is checked whether or not the conduction sensor 10 has been detected during that time (step S5). If there is no detection, the rotary tool 8 'is minutely fed toward the side surface 11B with the X-axis direction of the measurement reference position as a movement axis and is approached (step S6). Then, the measurement position Y2 is calculated from the Y coordinate Y1 of the reference position. The tool 8 'is made to approach the tracing stylus 11 while repeating the reciprocating movement (step S4) until the conduction sensor 10 detects and generates a conduction signal (step S5).

After the above process, the conduction sensor 10 generates a conduction signal (sensor detection position) X4.
Is stored by the NC device 20 (step S7). The following steps are the same as those in the case of the measurement of the tool length, and the description will be omitted.

In the above embodiment, the distance from the sensor detection position X4 to the X-axis coordinate X5, which is the side surface 11B of the tracing stylus 11, is | X4-X5 |, and the tool diameter D is the rotation axis of the rotary tool 8 '. Since the distance from C to the outermost end 8'A of the rotary tool 8 'is twice, the formula D = 2 (| X4-X5 |
−s). Therefore, the X-axis coordinate X of the side surface 11B
5 is known, the outermost end 8 'of the rotary tool 8'
When A discharges near the side surface 11B of the tracing stylus 11 and measures the X-axis coordinate X4, which is the rotation axis C of the rotating tool 8 'at the time when the conduction signal is generated, the tool diameter D is calculated by the above relational expression. it can. As described above, only the measurement on one side surface of the tracing stylus 11 makes it possible to measure the tool diameter D which is substantially the same as that at the time of machining.

It is conceivable that the coordinates of the main shaft 7 may cause slight errors in the X and Y axis coordinates with respect to the set values due to the thermal displacement caused by rotation. If this cannot be ignored, FIG. ), The main shaft 7 is moved to the reference position X3 'for measurement on the side surface 11B' side, and
For B ', the sensor detection position X4' is measured through the same process as that for the side surface 11B side and stored in the NC device 20, and D
= | X4-X4 '|-(b + 2s) can absorb this error. Here, the discharge gap s and the opposing side surface 1
Since the distance b between 1B and 11B 'is a known value, if the sensor detection positions X4 and X4' of both side surfaces 11B and 11B 'are measured and stored, the rotary tool 8' Is obtained and stored.

As described above, by conducting the conduction between the tool 8 and the measuring element 11 by detecting the non-contact discharge phenomenon, no measuring pressure is applied to the tool 8 and the measuring element 11, so that the tool 8 and the measuring element 11 Prevents bending and wear of 、
Not only tools with a diameter but also tools with a small diameter of 0.1 to 0.2 mm can be measured with high accuracy.

Next, a method for measuring the diameter of a tapered tool according to the present invention using the above-mentioned apparatus will be described with reference to the drawings. FIG. 7 is a diagram illustrating the principle of measuring the taper tool diameter according to the present invention.

In this method, as shown in FIG. 7, the discharge gap s is formed by rotating the taper tool 80 'and the ridge 1 of the tracing stylus 11.
There is a characteristic in that it is set between 1C. The taper angle can also be calculated by measuring the tool diameters D1 and D2 at two arbitrary heights h1 and h2 from the tip of the rotary taper tool 80 '. Here, it is assumed that the position of the tracing stylus 11 is accurately grasped. First,
The tool diameter D1 is measured, but is lowered from a standby position (not shown) similar to the straight tool diameter measurement to a measurement reference position. In this case, the measurement reference position of the main shaft 7 is determined by the height h1 based on the Z-axis coordinate Z7 of the tip of the rotary taper tool 80 'measured in advance by the tool length measurement method of the present invention.
Is matched with the Z-axis coordinate of the contact point P between the rotary taper tool 80 'and the ridge 11C, which is calculated in advance from the taper angle (nominal dimension θ of the gradient), and the X-axis coordinate is
The distance between the tool and the contact point P1 on the tool side, which is calculated from the nominal diameter of the tool tip and comes into contact with the corresponding contact point P, is a position separated by a gap u in the X-axis direction. Is located outside the width direction of the side surface 11B which does not interfere with the tracing stylus 11.

Here, the meaning of the gap u is the same as the gap t in the case of the tool length measurement and the gap w in the case of the tool diameter measurement, and is sufficiently larger than the discharge gap s and unnecessarily prolongs the measurement time. It is a value appropriately set within a range of no dimensions, and in this case also, it is 15 μm.

The ridge 11C of the tracing stylus 11 is measured in the same manner as the method for measuring the tool diameter of the straight tool described above.
X at the sensor detection position where electrical continuity is obtained by discharging with
It can be calculated by measuring the coordinate X7. Also, the tool diameter D2 can be measured in exactly the same way as in the case of the tool diameter D1. From the values of the tool diameters D1 and D2 obtained as described above and the distance | h2-h1 | between them, an accurate actual taper angle (gradient θ) can be calculated by the equation θ = tan-1 (| D2-
D1 | / 2 × | h2-h1 |). And the actual taper angle (gradient θ) obtained by measurement
Based on the above, the exact actual tip diameter of the rotary taper tool 80 'is calculated.

Since the minute feed amount at the time of measuring the tool length and the tool diameter described above is performed by a step movement at intervals of 0.5 μm, the measurement has a resolution of 0.5 μm unit. The gap s may be smaller than the set value, but the error is small and is acceptable. Further, if the discharge gap s and the size of the minute step feed are set small, the measurement accuracy is improved, but it is not necessary in practical use.

Note that the measuring element with R used in the present invention is not limited to the above-described embodiment, and R having different dimensions so as to face both ridges as shown in FIG. 3B. R1 (for example, 1 mmR), R2 (for example, 0.
By forming 5 mmR), measurement of tapered tools having different tool dimensions can be performed with one measuring element without changing the setup. Furthermore, it is needless to say that the tool can be replaced with a stylus and the probe can be replaced with a metal workpiece, and can be applied to the dimension measurement of the metal workpiece. Further, in the above embodiment, the spindle is a vertical machining center, but it is needless to say that the present invention can be applied to a machine tool having a horizontal spindle. Further, the X-axis coordinates and the Y-axis coordinates may be interchanged.

[0040]

As described above, according to the method for measuring the tool dimensions according to the present invention, the method for measuring the tool length and the tool diameter performs the final measurement by, for example, minute feed at intervals of 0.5 μm. Therefore, it is needless to say that the tool length can be measured with high accuracy.
A tool with a small diameter of 1 to 0.2 mm can be measured with high precision, and as a result, ultra-high precision machining has been realized. Further, by operating the conduction sensor 10 in a non-contact manner, no measurement pressure is applied to the tool and the stylus, so that bending, scratches and wear of the tool and the stylus are prevented. Therefore, the durability of the tool and the probe has been greatly improved. Furthermore, the use of the R-measurement element allows accurate measurement of the diameter and the taper angle of the tapered tool.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an example of an apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory view of a conduction sensor of the device of FIG.

FIG. 3 is a perspective view of a tracing stylus according to the present invention.

FIG. 4 is a diagram illustrating a principle of measuring a tool length according to the present invention.

FIG. 5 is a flowchart showing a basic procedure for measuring a tool length according to the present invention.

FIG. 6 is a diagram illustrating a principle of measuring a tool diameter according to the present invention.

FIG. 7 is a diagram illustrating a principle of measuring a taper tool diameter according to the present invention.

FIG. 8 is a schematic external view of the tool during rotation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Machining center 3 Table 7 Spindle 8 Tool 8 'Rotating tool 10 Conduction sensor 11 Measuring element 11A Top surface 11B, 11B' Side surface 11C Ridge part 80 Taper tool 80 'Rotary taper tool s Discharge gap

Claims (5)

[Claims] An electric potential difference is provided between a main shaft of a machine tool and a table, and a relative position between a tool attached to the main shaft and a measuring element fixed to the table is detected by electrical conduction to measure the size of the tool. In the method for measuring a tool size, the detection is performed by catching a discharge phenomenon occurring in a non-contact state between the tool and the tracing stylus. 2. A tool length is determined based on a position in a main axis direction detected while relatively moving the main axis in a radial direction at a position close to an upper surface perpendicular to the main axis of the tracing stylus while rotating the tool. The method for measuring tool dimensions according to claim 1, wherein the measurement is performed. 3. At a position close to a plane parallel to the main axis of the tracing stylus while rotating the tool, at a radial position detected while relatively moving the main axis in a radial direction parallel to the plane. 2. The method for measuring tool dimensions according to claim 1, wherein the tool diameter is measured based on the tool diameter. 4. The method according to claim 2, wherein the number of rotations of the tool is substantially the same as the number of rotations during machining. 5. The taper tool according to claim 3, wherein the diameter of the tapered tool is measured by using a measuring element having an R formed at a ridge line between an upper surface perpendicular to the main axis and a side surface parallel to the main axis. How to measure tool dimensions.