JPS5923942B2 - Automatic measurement method and device for numerically controlled machine tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in automatic measuring devices in numerically controlled machine tools.

Conventionally, various methods and devices for measuring the inner diameter, outer diameter, length, etc. of a workpiece have been proposed, and the present applicant also proposed a new automatic measuring device in Patent Application No. 61212 of 1971.

To explain this with reference to the drawings, Fig. 1 shows an embodiment of the automatic measuring device according to the above-mentioned application. A detection head 2 that can be rotated and retracted is installed at position B, and the cross slide 1 is moved by pulse motors 4 and 5 driven based on command information input to the numerical control device 3, and the cross slide 1 is moved to measurement position A. Two differential transformer type sensors 6.7 installed on the detection head 2 rotated to
are brought into contact alternately with two points P1 and P2 that are opposite on the diameter to be measured of the workpiece 9 held by the chuck 8 at the tip of the lathe main spindle, and the amount of deviation from the target dimension of the machined workpiece is measured. are detected, each of these deviation amounts is input to the arithmetic unit 11 via the A-D converter 10, and the sum or average value of each deviation amount is determined. This is converted into a tool position correction amount for the diameter machining tool cutting edge 13 and input to the numerical control device 3.

The above-mentioned automatic measuring device uses two stylus, that is, a differential transformer type sensor 6.7, at two opposing points P on the target diameter of the workpiece.
The average value of the deviation amount between the target value and the actual value that occurs in each of the two stylus 6 and 7 by alternately contacting the stylus 1 and P2 is determined as the tool position correction amount. Measurement can be performed regardless of changes in the main axis due to thermal displacement or discrepancies between mechanical system coordinates and program system coordinates.

However, since the above-mentioned automatic measuring device uses the positioning accuracy of the cross slide 1 through numerical control as the standard for measurement, the positioning accuracy, that is, the measurement accuracy is affected by the heat generated by the pulse motors 4 and 50 that move the cross slide 1 and the meandering of the cross slide 1. Since the detection head 2 also uses a differential transformer type sensor 6.7, it is affected by elastic deformation due to contact pressure with the workpiece, and small hole diameters cannot be measured. There was still room for improvement.

In view of the above circumstances, the present invention has a simple configuration and does not depend on the positioning accuracy of a numerically controlled machine tool (also, even if the position of the measurement point on the workpiece changes, the actual dimensions of the workpiece can be accurately measured). It is an object of the present invention to provide an automatic measurement method and apparatus for a numerically controlled machine tool that can perform measurement or measurement of the final finishing allowance of a workpiece and tool correction of the corresponding tool cutting edge position.

The present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram showing an embodiment in which the present invention is applied to a numerically controlled turret lathe.
A headstock 22 is provided at the left end (in the drawing), and a chuck 24 attached to the tip of a main shaft 23 rotatably supported by the headstock 22 grips the workpiece W with a plurality of chuck jaws 25. It rotates together with the main shaft 23.

The bed 21 has a guideway 26 on its upper surface that is parallel to the axis of the main shaft 23, and a saddle 27 movably placed on the guideway 26 is moved in a direction parallel to the axis of the main shaft 23 (hereinafter referred to as the Z direction). ) and slide it.

Further, a cross guideway 28 is provided on the upper surface of the saddle 27 and is perpendicular to the axis of the main shaft 23. A cross slide 2 movably placed on the cross guideway 28 is provided.
9 is guided and slid in a direction perpendicular to the main shaft 23 (hereinafter referred to as the X direction).

A Z-axis pulse motor 30 is provided at one longitudinal end of the bed 21 (the right end in the drawing), and a numerical control device 31
The Z-axis pole screw 32 screwed into the saddle 27 is rotated by rotation control based on a numerical control command from the saddle 27, and the saddle 27 is moved in the Z direction.

Further, an X-axis pulse motor 33 is provided at one side end (the upper end in the drawing) of the saddle 27, and similarly to the Z-axis pulse motor 30, the rotation is controlled based on a numerical control command from a numerical control device 31. An X-axis pole screw 34 screwed into the cross slide 29 is rotated to move the cross slide 29 in the X direction.

At a predetermined position on the cross slide 29, there is a turret tool rest 35 that is rotated and indexed by a command from a numerical controller 31 about an axis (not shown) perpendicular to the top surface of the cross slide 29. A plurality of tools 38 and 39 can be attached to the turret tool rest 35 by means of a plurality of tool holders 36 and 37 attached to the outer peripheral surface of the turret tool rest 35.

A stylus head 40 is attached to an arbitrary outer peripheral surface of the turret tool rest 35 in the same way as the tool holders 36 and 37, and a stylus 42 is attached to the tip of the stylus head 40 via an electrical insulator 41. is installed.

In detail, the stylus 42 is made of an electrically conductive and non-magnetic material, such as stainless steel, and has a coil spring-like shape with no contact portion (i.e., no friction mechanism). The tip of the tip is exposed to X due to an external force.
direction, Z direction and direction perpendicular to the X-Z plane (Y direction)
It is capable of elastic deformation on the order of several degrees, and is formed to have an extremely good property of returning to its initial position when external force is removed.

A slip ring 43 for conducting electrical signals from the stylus head 40 to the outside is attached on the rotation center axis on the turret tool rest 35, and a rotating portion of this slip ring 430 (not shown) The attachment of the stylus 42 to the electrical insulator 41 is electrically connected to the end point P, and the fixed side (not shown) of the slip ring 43 is connected to the fixed side installed above the turret tool rest 35. A detection signal generation circuit 4 (described later) is connected to the outside via a fixed block 45 fixed to a predetermined position on the cross slide 29 by a pipe 44.
9 is connected.

Furthermore, when the stylus 42 is indexed and positioned at a predetermined position such that the axis of the stylus head 40 is parallel to the Z direction, the axis line is aligned with a line extending from the tip of the stylus 42 in the X direction. A digital linear scale 46 is fixed on the saddle 27 so as to be parallel to the digital linear scale 46. The scale is read by moving on the digital linear scale 46, and the amount of movement of the cross slide 29 and thus the stylus 42 in the X direction is measured. A scale reading head 47 is fixed to the cross slide 29 which outputs a corresponding pulse train.

The digital linear scale 46 and the scale reading head 47 form a digital measuring device.

The reason why the digital measuring device is installed in such a position is that the two opposing points on the workpiece to be measured and the digital measuring device are always on the same straight line in the measurement direction (X direction) or extremely close to this same straight line. This is based on the measurement principle that measurement errors are minimized because they are arranged in parallel.

Therefore, the positioning accuracy of the cross slide is not affected by meandering, as is the case with conventional automatic measuring devices.

Next, the counting control circuit 48 will be explained.

In FIG. 2, 49 is a detection signal generating circuit, the details of which are shown in FIG.

That is, a contact 51 of the switch 50 is connected to the bed 21, and the other contact 52 is connected to the stylus 42 and the slip ring 43.
connected via.

When the power supply 53 and resistors 54 and 55 are configured as shown in FIG. 3, when the stylus 42 is not in contact with the workpiece W (which is electrically connected to the bed 21), the The potential at a point 56 between resistors 54 and 55 is
It holds a predetermined voltage divided by 4 and 55,
When the stylus 42 and the workpiece W are in contact with each other, the potential is the same as that of the head 21.

The logic circuit 57 is a circuit that detects such a change in the potential at the point 56 and, as a result, generates a signal at the moment the stylus 42 leaves the workpiece W.

Further, in FIG. 2, 58 is a control circuit, and this control circuit 58 receives the signal from the detection signal generation circuit 49, the command signal from the numerical control device 31, and the X-axis pulse motor 3.
3 and the pulse train from the scale reading head 47, and selects the pulse train to be counted and determines the start and end of counting.
The pulse train to be counted is sent to.

The counter 59 not only has the function of counting input pulses, but also has the function of being able to set any numerical value set by the digital switch 60 or the like using an external signal.

This counter 59 is connected to a display 61 on the one hand to display the counting contents, and on the other hand to a tool position correction circuit 62 that constitutes a part of the numerical control device 31, and the counting contents are displayed on the tool position correction circuit 62. It is configured so that it can be input.

The detection signal generation circuit 49, the control circuit 58, and the counter 59
, the digital switch 60 and the display 61 constitute a counting control circuit 48 as a whole.

The numerical control device 31 uses an X-axis pulse motor 33 and a Z-axis pulse motor 30 to move the turret turret 35 according to command information input from the outside using a tape or the like.
The tool position correction circuit 62
It has the function of correcting the above-mentioned pulse distribution according to the information input to the input terminal, and also commands the counter 59 to set the initial value set in the digital switch 60, starts counting the pulse train to the X-axis pulse motor 33, and It also has the function of issuing stop commands, etc.

Next, the operation will be explained.

First, with reference to FIG. 4, a case will be described in which, as an example, in the case of internal diameter finishing, the actual dimensions are measured immediately before final finishing cutting, and the deviation from the target dimensions is used as the tool position correction amount.

During measurement, the movement of the turret tool rest 35, that is, the stylus 42, is the same as when moving the tools 3B and 39, and the outer diameter dimension Ds of the stylus 42 and the required final finished dimension of the workpiece are set as the target. The numerical control device 31 can control the X-axis pulse motor 33 and the Z-axis pulse motor 3 by taking this into consideration as the dimension D2, creating a program in advance, and inputting it as command information such as a tape to the numerical control device 31.
0 pulses are distributed, their rotation is controlled, and their movement is controlled via the respective pole screws 34 and 32.

In addition, the outer diameter Ds of the stylus 42 is set to a well-defined value for convenience when assembling the above-mentioned program, and the difference from the actual outer diameter is set as the dimensional correction value ΔDs of the stylus 42. When the actual outer diameter is smaller, it is set as 10ΔDs, and when it is larger, it is set as −ΔDs in the counter 59 using the digital switch 60 or the like.

To explain the measurement operation step by step, first, the turret tool rest 35 is rotated by a command from the numerical controller 31, and the stylus 42 is moved so that its axis is parallel to the Z direction as shown in FIG. index and stop at a predetermined position.

Here, the control circuit 58 is instructed to set the correction numerical value ΔDs of the outer diameter dimension Ds of the stylus 42 and its sign, which have been set in advance in the digital switch 60, in the counter 59.

In this case, the content of the counter 59 becomes +ΔDs (provided that the actual outer diameter of the stylus 42 is smaller than the well-cut value Ds).

Next, pulses are distributed from the numerical control device 31 to the X-axis pulse motor 33 and the Z-axis pulse motor 30, and these are rotated to move the turret tool rest 35, and the stylus 42 is rotated.
Move the stylus 42 in the direction of the arrow a shown in FIG. 4 so that the center point O of the main shaft 23 is located at the 0 point on the center axis S
Then, it is moved along the arrow to point D in the hole of the inner diameter of the workpiece W to be measured.

Here, the numerical controller 31 issues a command to the control circuit 58 to start counting the X-axis pulse train, that is, the pulse train that the numerical controller 31 distributes to the X-axis pulse motor 33,
After that, the outer circumference of the stylus 42 is the hole to be measured (target inner diameter D2)
The center point O of the stylus 42 is moved along the arrow C so as to be in contact with the inner wall of the stylus 42 to a point E, that is, an X coordinate value (D2 Ds>/2).

At this time, the tip of the stylus 42 is elastically deformed by the amount of the final finishing cutting allowance and is stopped.

Generally, a diameter value command system is adopted for the movement of a numerically controlled lathe in the X direction, and the minimum movement unit in the X direction is usually a percentage of the minimum movement unit in the Z direction. For example, Dx When commanded to move, the amount of movement is D
x/2, but the number of pulses sent out is Dx.

Considering this, the content of the counter 59 at the time when the stylus 42 is positioned at the point E is △Ds+(D2 DS
), and the numerical value corresponding to the target dimension D2 is now set in the counter 59.

At this point, the counting of the X-axis pulse train should be stopped (instructed).

Next, the stylus 42 is moved along arrow d to point F, which is diametrically opposite to point E, that is, the X coordinate value -(D2 Ds)/2.

After starting to move in the direction of arrow d, the actual inner diameter just before final finishing cutting is Dl, and the final cutting allowance is the radius value △X
1, the outer diameter contact of the stylus 42 will be separated from the inner diameter contact of the workpiece W when the stylus 42 moves by (ΔX1-ΔDs/2), and at this moment the detection signal generation circuit 49
generates a signal, and the control circuit 58 receives the signal from the detection signal generating circuit 49 and causes the counter 59 to start counting the pulse train from the scale read head 47 from this point.

The number of pulses to be counted from the scale reading head 47 until the center point O of the stylus 42 reaches point F is ((D2
DS )=(△X1-△Ds/2)), therefore, the content of the counter 59 at this point is (△Ds+(
D2-Ds)) -((D2-Ds)-(△X1-△D
s/2)) - (ΔX, +ΔDs/2).

Next, move the stylus 42 from point F in the direction of arrow e,
The main shaft 23 is returned to point D on the central axis S and positioned.

After starting to move in the direction of arrow e, the stylus 42 moves to (△X1-
ΔDs/2), the outer diameter contact point of the stylus 42 is again separated from the inner diameter contact point opposite to the inner diameter contact point of the workpiece W, and at this moment the detection signal generation circuit 4
9 generates a second signal, at which point the control circuit 58 causes the counter 59 to stop counting the pulse train from the scale read head 47.

Therefore, the count content of the counter 59 at this point is (△
X1+△Ds/2)+(△X1-△Ds/2)=2X△
X1, which means that the numerical value to be used to correct the tool edge position, that is, the final cutting allowance has been obtained.

Next, the turret tool rest 35 is moved back to a predetermined position, the numerical value 2×ΔX1 to be corrected calculated and counted as described above is inputted to the tool position correction circuit 62, and then the turret tool rest 350 is indexed. If the corresponding finishing tool, for example 38, is indexed to the machining position and the final finishing cutting is performed, the cutting edge position of the tool 38 will be 2×△ before machining.
Since the correction is made by X1 (however, the diameter value), the target dimension D2 can be accurately obtained.

By the way, when calculating 2×ΔX1 in this way, the number of pulses to be counted from the scale reading head 47 when the stylus 42 moves in the directions of arrows d and e is:
((D2 D8) (△X, -△Ds/2)) -
(△X1-△Ds/2)-D2-Ds-2△X1+△D
It becomes s.

On the other hand, when the stylus 42 moves in the direction of arrow C, the content of the counter 59 is (ΔDs+D2-Ds).

Then, for both of these values, the former is subtracted from the latter, and 2×ΔX1 is calculated as a result.

Therefore, if Ds = Ds - △Ds, that is, the dimensional value Ds of the stylus 42 is set to the actual dimensional value including the dimensional correction value △Ds or its dimensional correction value △Ds = 0, the former value becomes (D2 -Ds-2△X1), and the latter value is (D2-D
s), and 2×ΔX1 is calculated in the same way as in the previous case.

In this way, in any case, the dimensional value Ds of the stylus 42 and its dimensional correction value ΔDs cancel each other out to calculate an accurate ΔX1.

Although not mentioned in the above explanation of the operation, the positioning of the stylus 42 to points E and F, for example, is not always accurate due to elongation due to heat generation of the X-axis pole screw 340, and heat generation in the headstock 22 is the main cause. As a result, the center position of the workpiece W is also slightly deviated from the center axis S of the main shaft 23.

However, according to the present invention, it is possible to obtain the required accurate measurement value (final finishing allowance) without being affected by these thermal displacements.

This point will be explained below with reference to FIG.

In addition, in order to simplify the explanation, in the following, the above △
A case where Ds is O will be explained.

In FIG. 5, the center point 0 of the stylus 42 is
Move the stylus 42 so that it is at point D on the central axis S of the main shaft 23.
move.

The contents of the counter 59 at this point are, in this case, △Ds=O
is set, and the numerical controller 31 issues a command to the control circuit 58 to start counting the X-axis pulse train, that is, the pulse train that the numerical controller 31 distributes to the X-axis pulse motor 33.

Next, the outer circumference of the stylus 42 is set in the hole to be measured (target inner diameter D2
) along arrow C to point E, that is, the X coordinate value (D2-Ds)/2.

Here, the content of the counter 59 is (D2 Ds) regardless of the positioning accuracy, but the actual position of the center point O of the stylus 42 is 8, which is shifted by 6M1 from point E due to thermal displacement etc.
Assume that it is at one point.

Next, the control circuit 5 stops counting the X-axis pulse train.
8, and then move and position the stylus 42 along the arrow d to point F, which is diametrically opposite to point E, that is, X coordinate=(D2-Ds)/2.

After this movement starts (ΔX1+ΔM1), the stylus 42 leaves the workpiece W, and at this moment the detection signal generating circuit 49 emits a signal, and the control circuit 58 receives this signal and starts the counter from this point onwards. 59 to begin counting the pulse train from the scale read head 47.

When the positioning of the stylus 42 to point F is completed, the position of the center O of the stylus 42 is 6M1 from point F if the positioning error is eliminated.
The F0 point should be far away, but if it actually becomes the F2 point ΔM2 away from the F point due to thermal displacement, the number of pulses to be counted from the scale reading head 47 is (((D2 D8) −(△X1+ΔM1)) 10△M
1+△M2], and the contents of the counter 59 are (D2-Ds)-C((D2-Ds) (△X1+△
M1))+ΔM1+ΔM2) = (ΔX1−ΔM2
).

Next, move the stylus 42 in the direction of arrow e, and
Return to point D on the central axis S of and position.

After this movement starts (ΔX1+ΔM2), the contact point on the outer diameter of the stylus 42 leaves the contact point on the inner diameter of the workpiece W, and at this moment the detection signal generation circuit 49 again emits a signal, and the control circuit 58 This signal causes the counter 59 to stop counting the pulse train from the scale read head 47.

Therefore, the content of the counter 59 when the center point 0 of the stylus 42 reaches point D is (△X1 - △M2) + (△X1 +
ΔM2)-2×ΔX, and the tool position correction amount, that is, the final cutting allowance (however, the diameter value) is obtained.

By the way, when calculating 2×ΔX1 in this way, the number of pulses to be counted from the scale reading head 47 when the stylus 42 moves in the directions of arrows d and e is (
((D2 Ds) (△X10△M1))+ΔM1
+ΔM2]-(△X1+ΔM2)-(Ds-D2-2△
DX1).

On the other hand, the content of the counter 59 when the stylus 42 moves in the direction of arrow C is (D2-Ds).

Then, for both of these values, the former is subtracted from the latter, and 2×ΔX1 is calculated as a result.

In this way, 6M1 and ΔM2 are each canceled out, and an accurate value of ΔX1 is calculated.

That is, it has been revealed that according to the present invention, it is possible to obtain the required accurate measurement value (final finishing allowance) without being affected by the positioning accuracy of the machine.

Further, although a detailed explanation will be omitted, it is clear that even if the center position of the workpiece W is slightly deviated from the central axis S of the spindle 23, accurate information can be obtained without being affected by this. It is.

Furthermore, it is clear that measuring the outer diameter can be carried out as accurately as described above.

As mentioned above, the numerical value to be corrected can be obtained accurately, but in reality, depending on the material and temperature of the workpiece W to be measured, the rigidity of the workpiece, and the method of gripping the chuck 24, the set depth of cut may vary. It is necessary to take into account that there is a difference between the actual depth of cut and the actual depth of cut.

However, the errors caused by these various phenomena should be determined in advance as knowledge of the processing technology for each workpiece W, and in the present invention, the above-mentioned stylus 4
When setting the difference between the well-cut outer diameter value of No. 2 and the actual outer diameter dimension, that is, the dimension correction value △Ds, by appropriately adding or subtracting the error amount known for each workpiece W to △Ds. , correction including this amount of error can be easily performed.

The above explanation relates to measurement in the X direction, but when measuring in two directions, a digital linear scale 46 is also prepared in the Z direction, and the scale shown by the two-dot chain line in FIG. The counter 5 is controlled by the control circuit 58 as follows.
If 9 is configured to count biaxial pulse trains, measurement in the Z direction can also be performed in the same way as measurement in the X direction.

Next, the case of determining the actual dimensions of the workpiece will be explained with reference to FIG. 4, in comparison with the case of determining the tool position correction amount described above.

First, the actual outer diameter dimension (denoted as Ds) of the stylus 42 is set using the digital switch 60, etc., and is set in the counter 59 at the start of measurement.

Next, move the stylus 42 by the arrow a shown in FIG.
Then, it is numerically controlled to move along the arrow line to point D in the hole of the inner diameter of the workpiece W to be measured.

Let Dl be the actual dimension of the inner diameter of the workpiece W to be measured,
In order to ensure that the outer periphery of the stylus 42 comes into contact with the inner wall of the hole to be measured, an arbitrary inner diameter dimension slightly larger than the required final finished dimension of the workpiece or the actual dimension is set as the target dimension D2, and the stylus 4
2 is the F point in Fig. 4, that is, the X coordinate value -(D2-
Positioning is performed by numerical control movement in the direction of arrow d to Ds)/2.

Then, the stylus 42 is moved by numerical control in the directions of arrows e and C to point E in FIG. 4, that is, the X coordinate value (D2 Ds), /2.

When the stylus 42 moves by ΔX1 (-(D2-Dl)/2) after the start of this movement, the contact point on the outer diameter of the stylus 42 separates from the contact point on the inner diameter of the workpiece W, and at this moment the detection signal generation circuit 49 outputs a signal. This signal causes the control circuit 58 to cause the counter 59 to count the pulse train from the scale read head 47 from this point on.

The content of the counter 59 when the stylus 42 is numerically controlled and moved along arrows e and C and reaches point E is Ds+(D2-
DS)-ΔX1-(D2-ΔX, ).

Next, the stylus 42 is again numerically controlled and moved along arrow d to point D and returned.

After the start of this movement ΔX, the outer diameter contact point of the stylus 42 leaves the inner diameter contact point of the workpiece W, the detection signal generation circuit 49 generates a signal again, and at this moment the control circuit 58
This signal causes the counter 59 to stop counting the pulse train from the scale read head 47.

The contents of the counter 59 at this point are (D2-△X1)-△
X,=D2-2×ΔX1-D1, and the actual dimension D1 has been found.

This actual dimension D1, that is, the final result of counting by the counter 59, is displayed on the display 61.

By the way, when calculating the actual dimension D1 in this way,
The number of pulses to be counted from the scale reading head 47 when the stylus 42 moves in the directions of arrows d and e is (D2-Ds-△X1)-△X1-D2-Ds-2△
It becomes X.

In contrast, the contents of the preset counter 59 are the same as those of the stylus 4.
The outer diameter dimension Ds of 2 is.

Then, for both of these values, the latter and the former are added, and as a result, the actual dimension D1 becomes D1=
It is accurately calculated from D2-2ΔX1.

Furthermore, even when measuring the actual dimensions mentioned above,
As in the case of calculating the tool position correction amount described above, it is natural that accurate measurements can be made without being equally affected by positioning errors due to thermal displacement of the machine and displacement of the center position of the workpiece W. .

In the above embodiment, the case was explained in which the case was implemented in a numerically controlled turret lathe and the diameter of a round object was measured, but the present invention is not limited thereto, and can be applied to other general numerically controlled machine tools, such as numerically controlled It is also possible to install it on a controlled boring machine, and it is also possible to easily measure the length in the axial direction.

As described above, the present invention uses one stylus, and the stylus moves from the center position between two opposing points on the part of the workpiece to be measured until it touches one of these two points. Selectively measure the travel distance of the stylus, that is, the travel distance to the target dimensional position, and also measure the travel distance of the stylus from the moment the stylus leaves this one point to the moment it hits the other point and breaks. Accordingly, the present invention has the following effects.

(1) Accurate measurement can be performed without being affected by the cross slide when moving the stylus by numerical control, that is, the positioning accuracy of the stylus mount and meandering.

(2) Even if the center position of the workpiece is slightly deviated from the central axis of the spindle, accurate measurement can be performed.

(3) Even if the stylus, which can be elastically deformed, is slightly vibrating due to vibrations generated by the machine, the measurement accuracy is low because it detects the moment when the stylus leaves the workpiece after it makes contact with the workpiece. does not decrease.

(4) The stylus only needs to come into contact with and separate from the workpiece, and its shape is not particularly restricted, so it can be made into an extremely simple shape, making it easy and inexpensive to work with. In addition, it is possible to easily measure not only small hole diameters but also complex shapes such as grooves in holes, grooves on the outer diameter, and diameters.

At the same time, the measurement accuracy is not affected by the contact pressure of the stylus, which has a shape that does not include a friction mechanism.

(5) All that is required for data processing to determine the actual dimensions of the workpiece and the amount of tool position correction is mainly a counter, so the control circuit configuration can be extremely simple compared to conventional ones. .

(6) Therefore, according to the present invention, it is possible to obtain an automatic measuring device that is capable of highly accurate measurement and associated tool position correction, and that is simple in configuration and inexpensive.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an example of a conventional automatic measuring device for a numerically controlled turret lathe, Fig. 2 is a block diagram showing an example of applying the present invention to a numerically controlled turret lathe, and Fig. 3 is a detection signal generation A block diagram of the circuit, Figure 4 is a measurement principle diagram showing the relational operation between the workpiece and the stylus head, and Figure 5
The figure shows the measurement principle when machine positioning errors are included. 29...Cross slide, 40...Stylus head, 42,...Stylus, 46...Digital linear scale, 47... Scale reading head, 48... Counting control circuit, 49...
. . . detection signal generation circuit, 58 . . . control circuit,
59...Counter, 60...Digi switch, 61...Display device, W...Workpiece.

Claims (1)

[Claims] 1. A stylus head having an elastically deformable stylus is mounted on the movable table of a numerically controlled machine tool, and two opposing points to be measured on a workpiece gripped by the numerically controlled machine tool are mounted. The stylus head is numerically controlled to be moved to the target dimension position of the workpiece so that the stylus is brought into contact with each of the workpieces alternately, and the moment the stylus leaves one of the two opposing points on the workpiece. The amount of movement of the stylus head from 1 to the moment it leaves the other point is counted as a measurement pulse train, and the counted value (D2-Ds
-2△ X
, ), or the final finishing allowance ΔX which should be the correction amount of the corresponding tool cutting edge position prior to finishing machining, in a numerically controlled machine tool. 2. Contact with the workpiece to be measured, which is mounted on the moving table of a numerically controlled machine tool and held by this numerically controlled machine tool.
a stylus head having a single elastically deformable stylus that detects non-contact as a potential change; and a stylus head disposed with a measurement axis parallel to an extension line in the measurement direction from the tip of the stylus. It is equipped with a digital measuring device that generates a measurement pulse train corresponding to the amount of movement of the head in the measurement direction, and a counting control circuit, and the counting control circuit is configured to detect the stylus in response to a detection signal from the stylus head. a detection signal generation circuit that emits a signal at the moment of separation from the workpiece that has come into contact; and a detection signal generation circuit that is connected to the digital measurement device and the numerical control device of the numerically controlled machine tool; A control circuit that starts or stops sending out the measurement pulse train from the measuring device and further selects and sends out the numerically controlled movement pulse train from the numerical control device, and D2
-Ds-2ΔX1), and the counted value, the dimension value Ds of the stylus, and the target dimension value D2 of the workpiece
The actual dimension D1 (Dl-
1. An automatic measuring device for a numerically controlled machine tool, comprising: a counter for counting D2-2ΔX1) or a final finishing allowance ΔX1.