JPH09183041A - Adaptive controller for machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly and easily set the dwell time required for a dwell process that enhances the accuracy of machining work by extremely reducing, in machining the work, the moving speed of a tool relative to the work at the completion of machining. SOLUTION: A dwell time setting table 51 is originated by experimentally obtaining in advance the amount P of pressure leakage corresponding to the accuracy of machining work (e.g. valve seat) for the number N of times that a tool is used. Using the number N of times as a parameter for the set amount Pr of pressure leakage, dwell time Td can be set uniquely by consulting the dwell time setting table 51.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adaptive control device for machine tools capable of optimizing a dwell time set for a tool when machining a work by a machine tool.

[0002]

2. Description of the Related Art Conventionally, for example, when a workpiece is machined by a tool such as an end mill attached to a spindle of a machine tool, the relative movement speed (advance speed) of the tool to the workpiece is extremely increased at the end of the machining. The dwell process is adopted to improve the machining accuracy of the work by making it slower.

Explaining with a concrete example of the work, for example, when the inner peripheral wall of the bottom surface of the ring-shaped valve seat 1 as shown in FIG. 6 is tapered to form the seat surface 2 for the valve, With respect to the valve seat 1 fixed on a mounting base (not shown), the end mill mounted on the spindle is advanced in the arrow direction (the central axis direction of the valve seat 1) to cut or grind the seat surface 2. In order to improve the processing accuracy (grinding accuracy) at the final stage of this grinding, it is effective to perform a so-called dwell processing, that is, processing for controlling the advancing speed of the end mill in the direction of the arrow for finish processing for a predetermined time. It is known. The rotation speed of the spindle that rotates the end mill around the axis is constant.

In order to judge the quality of the result of the dwell process, the ground valve seat 1 is sent to a pressure leak measuring step, and in the inspection room in the step, for example, as shown in FIG. It is attached to the upper end of the cylinder chamber 3 that constitutes the engine.

With the valve seat 1 attached to the cylinder chamber 3, the valve 4 is closed as shown in FIG.
A constant air pressure is applied to the cylinder chamber 3. At this time, the pressure leak amount P (cc / min) in the passage 5 is measured with a pressure gauge, and the measured pressure leak amount P is a prescribed pressure leak amount (also referred to as set pressure leak amount) Pr. On the condition that it is the following, it is indirectly recognized as having obtained the desired processing accuracy (grinding accuracy).

[0006]

By the way, the processing accuracy is premised on that the cutting ability of the blade of a tool such as the end mill which is the processing tool is good.

That is, when the tool is worn out,
Since the desired machining accuracy cannot be obtained, the tool needs to be replaced with a new tool.

Therefore, conventionally, the operator determines the dwell time to be a fixed time by trial and error, and the tool replacement timing, that is, the wear state is managed by the operator's sensual judgment. Was there. That is, the tool replacement timing is determined by visually determining the waviness of the machined surface during cutting, or by a so-called sensory inspection that captures a subtle change in cutting sound.

[0009] However, such a sensory test according to the conventional technique is a work that requires a great deal of skill,
There is a problem in that not only the lack of stability but also the rate at which the desired processing accuracy can be obtained changes depending on the physical condition of the skilled worker.

Therefore, when the worker is an ordinary worker who is not a skilled worker, the set dwell time is too long, and as a result, the man-hour required for the work is increased or the dwell time is set short. There is a problem that the tool cost, that is, the component cost may be extremely high because the tool is frequently replaced and the tool is frequently replaced.

The present invention has been made in view of the above problems, and provides an adaptive control device for a machine tool capable of easily setting a dwell time at which a constant (desired) machining accuracy is obtained. The purpose is to

[0012]

SUMMARY OF THE INVENTION The present invention provides a machine tool adaptive control for setting the dwell time in the machine tool when processing a workpiece with a tool mounted on the machine tool and performing dwell processing. In the device, when the dwell time is controlled to be set according to the desired machining accuracy and the preset wear state judgment standard of the tool, the desired machining accuracy allows the processed work to be mounted on the product. The desired physical quantity at that time is set as a substitute value, and the wear state judgment criterion of the tool is set as the number of times of use of the tool.

Further, the present invention is, for example, shown in FIGS.
As shown in, when the workpiece 1 is machined by the tool 28 mounted on the machine tool 11 and the dwell processing is to be performed, the machine tool adaptive controller for setting the dwell time Td is set in the machine tool. Relative displacement amount detecting means 1 arranged to detect the relative displacement amount Z between the work and the tool.
9, a predetermined dwell time deriving means 51 for deriving a predetermined dwell time Td according to the wear state of the tool and a desired machining accuracy, and a machining time detecting means 32 for detecting the machining time.
And a machining control means 31 connected to the relative displacement amount detecting means, a predetermined dwell time setting means, and a machining time detecting means, and the machining control means, when newly machining a workpiece, uses the workpiece and the tool. Are processed relatively close to each other, and after the relative displacement amount Z detected by the relative displacement amount detection means reaches a predetermined value Za, the processing time detection means starts measuring a predetermined dwell time (FIG. 5). Medium, refer to time t1), when this predetermined dwell time has elapsed (refer to time t2)
In addition, it is characterized in that the work and the tool are controlled to be separated from each other.

According to the present invention, the dwell time for the work can be set appropriately.

As the dwell time deriving means, it is possible to use an arithmetic means using a predetermined arithmetic expression or a look-up table.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In the drawings referred to below, the components corresponding to those shown in FIGS. 6 and 7 described above are designated by the same reference numerals, and detailed description thereof will be omitted. Further, in order to avoid duplication of the drawings, description will be made with reference to FIGS. 6 and 7 as necessary.

FIG. 1 shows a machine station in which an adaptive controller for machine tools according to this embodiment is incorporated.

This machine station is composed of a machine tool 11 and a numerical control panel 12, and the machine tool 11 and the numerical control panel 12 are electrically connected to each other through a wiring 13 such as a communication line and a power line. There is.

The machine tool 11 has a base 15, and a column 16 is vertically arranged on one end side of the base 15. A work mount 17 is arranged in parallel with the column 16. A work holding unit 18 on which a plurality of valve seats 1 that are works can be mounted and arranged is arranged on the main surface of the work mount 17.

A displacement sensor (relative displacement amount detecting means) 19 such as a strain gauge or an electronic micrometer is fixed to the work holding unit 18 via an L-shaped member. The displacement sensor 19 is not limited to a strain gauge or an electronic micrometer, but a length measuring machine using a laser, a magnetic scale, or the like can be used.

The output signal of the displacement sensor 19 is the column 16
In the middle of the base 15, it is taken into the numerical control panel (which functions as a predetermined dwell time deriving means, a machining time detecting means, a work machining control means, and a use count storing means) 12 through the wiring 13.

On the base 15 of the machine tool 11, a hydraulic cylinder 21 driven and controlled by the numerical control board 12 is arranged. Through the rod 22 of this hydraulic cylinder 21,
A slide unit 25 including a spindle motor (spindle unit) is moved in the direction of arrow Z (Z is also used as a displacement amount) (also referred to as forward direction) or in the opposite direction (also referred to as backward direction).

A gang head 26 is provided in front of the slide unit 25 in the direction of arrow Z.
Are integrally arranged in the. A plurality of tool mounting heads 27 that are coupled to the spindle motor via gears are arranged at the tip of the gang head 26, and a tool 28 such as an end mill is mounted on the tool mounting head 27. The valve seat 1, which is a workpiece, is cut or ground by advancing in the arrow Z direction while the tool 28 is rotated by the spindle unit.

A schematic electrical circuit block diagram of the processing station shown in FIG. 1 is shown in FIG. The numerical control panel 12 is
It has a CPU 31 as a body of adaptive control means, and a CPU 3
1 includes a timer 32 as a time measuring means for measuring a dwell time and the like, and a counter 36 as a counting means for counting the number of times N of use of the tool 28, in other words, the number of times of machining (the number of machining) N.

A ROM 33 is connected to the CPU 31,
The ROM 33 stores a system program, an application program for adaptively controlling the hydraulic cylinder 21 and the like, an arithmetic expression program for calculating the dwell time, a look-up table and the like.

The CPU 31 is also connected to a RAM 34 for so-called work, a data input / output device 35 such as a keyboard, a mouse, and a printer, and a CRT 39 for displaying the movement locus of the slide unit 25. As a result, the CPU 31 drives and controls the machine tool 11 as a whole through the hydraulic cylinder 21 and appropriately processes the valve seat 1 as a work.

In FIG. 2, ROM 33 and R
In addition to the semiconductor memory, the AM 34 includes a writable and readable external storage device such as a hard disk, and can be considered to store the above-described programs and the like.

The counter 36 sequentially counts the number of times N the tool has been used. The RAM 34 stores the counted number of times of use N and presets a set pressure leak amount Pr, which is an upper limit value of the pressure leak amount P.

In FIG. 1 and FIG. 2, the output signal of the displacement sensor 19 fixedly arranged on the machine tool 11 is
The data is taken into the numerical control board 12 through the wiring 13, and the so-called sampling processing is performed by the sample-hold circuit 37 and the AD conversion circuit 38 in the numerical control board 12 by the CPU.
It is taken in by 31. The sample hold circuit 37
The AD conversion circuit 38 and the AD conversion circuit 38 are controlled by a control clock (not shown) supplied from the CPU 31.

FIG. 3 shows a dwell time setting table 51 stored in the ROM 33 as a look-up table in advance.
Is schematically shown. This dwell time setting table 51 basically uses the number N of times of machining of the tool 28 as a parameter, and the measured dwell time Td also includes the pressure measured by incorporating the valve seat 1 into a cylinder device (not shown) as a product. It is a table created by plotting the amount of leakage P.

In FIG. 3, the symbol ◯ is the experimental data when the number of times N the tool 28 has been used is N = 500, and from this experimental data, the characteristic including all the experimental data of the symbol ◯ inside (on the origin side) is shown. If the characteristic (characteristic curve) 52 is set, the maximum dwell time (optimal dwell time) for securing the pressure leakage amount P, which is a desired physical quantity from the characteristic 52 to the number of times N of use up to N = 500 times, that is, the setting The dwell time Td can be uniquely derived.

Note that, in consideration of shortening the set dwell time Td to shorten the working time of the whole work, or considering the component cost of the tool 28, all the experimental data of the symbol ◯ is included therein. Instead of the characteristic, the characteristic may include a constant ratio such as 3σ (where σ is the standard deviation). When the dwell time Td is set in this way, defective products are generated in the valve seat 1 at a constant rate, but in some cases, the manufacturing cost can be reduced as a whole. In short, the optimum dwell time can be set according to the cost situation of human resources or physical resources.

In this embodiment, furthermore, the number of times of use N
Where N is 100 times, the characteristic 53 includes all experimental data of the symbol Δ, and the number of times N is N = 0, that is,
The characteristic 54 including all the experimental data of the symbol □ indicating that the tool 28 is new is set in advance. of course,
The characteristics 52, 53, and 54 may be stored in advance in the ROM 33 as an arithmetic expression along the inverse proportionality and used.

Next, the operation of the work station incorporating the above embodiment will be described with reference to the flow chart shown in FIG. The control subject is the CPU 31.

First, a desired machining amount for the valve seat 1 is displaced by using the input / output device 35 (predetermined value) Za.
(Z = Za) is set in the RAM 34 (step S
1).

Next, the pressure leakage amount P corresponding to the desired processing accuracy is set (step S2). The set pressure leakage amount is represented by Pr, and in this embodiment, the set pressure leakage amount Pr is set to Pr = 20 [cc / min] (see FIG. 3).

Further, the number of times of machining, in other words, the number of times N of use of the tool 1 is N = the number of times of use N when the tool 1 is not used.
It is set to 0 times (step S3). The number of times of use N is set in the counter 36. Therefore, it is preferable that the counter 36 is functionally a preset down counter.

Further, the timer 32 is reset to set the measured value T to T = 0 (step S4).

In this state, by pressing a machining start button (not shown), the hydraulic cylinder 21 is driven and the gang head 26 starts to move in the direction of arrow Z (see FIG. 5).
(Refer to the point t0 in the middle), processing of the valve seat 1, which is a workpiece, is started (step S5).

Next, the dwell time Td is automatically set (step S6). The dwell time Td is calculated in step S2
It is possible to uniquely and immediately determine the set pressure leak amount Pr set in step 3 and the number of times of use N set in the counter 36 as a key and referring to the dwell time setting table 51 shown in FIG. . In this case, since the set pressure leak amount Pr is Pr = 20 [cc / min] and the number of times of use N is N = 0, the dwell time Td is Td≈0.15 [from the dwell time setting table 51. s
ec] is set. The set dwell time Td is preset in the timer 32. Of course, the set pressure leak amount P
r and the set dwell time Td can be displayed on the display 39, and the dwell time setting table 51 shown in FIG. 3 is displayed on the display 39 in the state shown in FIG. For confirmation, set pressure leak amount Pr and set dwell time Td
It is also possible to mark and display and with a display cursor or the like.

Then, the displacement amount Z is obtained by sampling processing.
Is detected from the displacement sensor 19 (step S7). The process of detecting the displacement amount Z is shown in FIG. FIG. 5 is a diagram which is also provided for explaining the processing process. The displacement characteristic 55 shown in FIG. 5 is also displayed on the display (C
RT) 39 and can be displayed as a waveform.

The displacement detecting operation is continuously repeated until the displacement amount Z detected by the displacement sensor 19 reaches the set displacement amount Za set in step S1 (step S).
7, S8).

When the result of step S8 is positive,
That is, when the valve seat 1 is processed by the tool 28 by a predetermined amount (see time t1), the dwell process (step S9) is started. That is, the time counting by the timer 32 is started, the measured time T is compared with the set dwell time Td (step S10), and when the measured time T reaches the set dwell time Td (T = Td: step S10 “YE”).
S ”), it is determined that the machining is completed as a whole, the hydraulic cylinder 21 is driven in the direction opposite to the arrow Z direction, and the gang head 26 retracts in the direction opposite to the arrow Z direction (step S11). As a result, the valve seat 1 with desired processing accuracy is manufactured.

At the same time as the backward command in the opposite direction, the number of times of use (the number of times of machining) N is increased by 1 and the count value N of the counter 36 is set to N ← N + 1 (step S12).

By repeating the processes of steps S4 to S12 a required number of times, the required number of valve seats 1 as a finished product can be manufactured.

In this embodiment, when the number of uses N becomes N = 1, the dwell time Td becomes
When Td is reset to 0.45 [sec] and the number of times of use N becomes N = 101 times, the dwell time Td is Td.
Is reset to 0.85 [sec]. Use count N is N
= 501 times, an instruction to replace the tool 1 is given on the display 39 or by an alarm or the like (not shown).

As described above, according to the above-described embodiment, the minimum necessary amount is set in accordance with the amount of pressure leakage Pr corresponding to the desired processing accuracy and the number of times N of use of the tool 28 as a preset wear state determination standard. Since the dwell time Td is set, the optimum dwell time Td can be automatically set (reset). Since it is possible to accurately manage the proper number of workpieces machined by the tool 28, as a result, the effect of reducing the cost of parts of the tool 28 is achieved.

The present invention is not limited to the above-described embodiments, and it goes without saying that various configurations can be adopted without departing from the gist of the present invention.

[0049]

As described above, according to the present invention, since the dwell time is set according to the desired machining accuracy and the preset wear condition judgment standard of the tool, the optimum dwell time is set. Can be easily set (reset). According to the conventional technique, since the dwell time is set to a fixed time, it is difficult to say that the set time is necessarily set optimally. That is, when the dwell time is set to be longer than necessary, there is a problem that the total processing time becomes long and the processing man-hour increases, and if the time is set too short, the desired processing accuracy can be obtained. The number of uses until it disappears becomes small, and as a result, a situation where the tool is frequently changed occurs, but according to the present invention, these inconveniences are eliminated, and, for example, the total cost is reduced. The effect that the minimum dwell time can be easily set is achieved.

Of course, it is also possible to automatically set the dwell time.

If the tool wear condition is determined by the number of times the tool has been used, it is easy to set the reference.

Further, the desired processing accuracy can be a value obtained by substituting a desired physical quantity when the processed workpiece is mounted on the product. By doing so, there is an advantage that it is not necessary to directly measure the processing accuracy, which is relatively difficult to measure, and the desired physical quantity that is finally required can be set.

In particular, when the work is a valve seat, if the desired processing accuracy is the amount of pressure leakage and the wear state determination criterion is the number of times the blade is used, an appropriate dwell time can be set automatically. it can.

Furthermore, the derivative effect that the tool replacement time can be notified can be achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a processing station to which an embodiment of the present invention is applied.

FIG. 2 is a block diagram showing an electric circuit configuration in the processing station of FIG.

FIG. 3 is a characteristic diagram showing an example of a dwell time setting table.

FIG. 4 is a flowchart for explaining the operation of the example of FIG. 1;

FIG. 5 is a characteristic diagram showing a trajectory of a displacement amount of a spindle.

FIG. 6 is a perspective view showing a configuration of a valve seat.

FIG. 7 is a partially omitted cross-sectional view for explaining an operation of detecting a pressure leakage amount of a valve seat mounted on a cylinder.

[Explanation of Codes] 1 ... Valve seat (work) 4 ... Valve 11 ... Machine tool 12 ... Numerical control panel 19 ... Displacement sensor 21 ... Hydraulic cylinder 26 ... Gang head 28 ... Tool 31 ... CPU 51 ... Dwell time setting table

Claims (3)

[Claims] 1. An adaptive control device for a machine tool, which sets the dwell time in the machine tool when a workpiece is machined by a tool mounted on the machine tool and dwell processing is to be performed. When controlling to set the dwell time according to a preset wear state determination standard of the tool, the desired processing accuracy is replaced by a desired physical quantity when the processed workpiece is mounted on a product. And the wear state of the tool is determined as the number of times the tool has been used. 2. An adaptive control device for a machine tool, which sets the dwell time in the machine tool when processing a workpiece by a tool mounted on the machine tool and performing a dwell process, Relative displacement amount detecting means provided for detecting the relative displacement amount of the work and the tool, a predetermined dwell time deriving means for deriving a predetermined dwell time according to the wear state of the tool and the desired processing accuracy, A machining time detecting means for detecting a machining time, a relative displacement amount detecting means, the predetermined dwell time setting means, and a machining control means connected to the machining time detecting means, wherein the machining control means is the tool When a new workpiece is processed by the method, the workpiece and the tool are relatively brought close to each other to process the workpiece, and the phase detected by the relative displacement amount detecting means is detected. After the displacement amount reaches a predetermined value, the processing time detection means starts measuring the predetermined dwell time, and when the predetermined dwell time elapses, the work and the tool are controlled to be separated from each other. Applicable control device for machine tools. 3. The dwell time deriving means includes an arithmetic means using a predetermined arithmetic expression or a look-up table, the wear state of the tool is judged by the number of times of use of the tool, and the desired machining accuracy is The processed workpiece is a value that is replaced by a desired physical quantity when mounted on a product, the product is a cylinder, the workpiece is a valve seat mounted on the cylinder, and the tool is a spindle of the machine tool. It is a cutting tool attached to the unit, the part to which the dwell process is applied is the seat surface of the valve seat, and the physical quantity is a pressure leakage quantity. Control device.