JPH0651260B2 - Cutting condition monitoring device by load cell - Google Patents

Description

Description: (1) Industrial field of application The present invention relates to a cutting state monitoring device using a load cell when turning a workpiece in a head moving type machine tool for industrial machines, particularly steel pipe processing. .

(2) Conventional technology Conventionally, in a head moving type machine tool for processing steel pipes in machine tools, etc., when performing cutting on a steel pipe of a workpiece, in order to accurately position the steel pipe that is the workpiece to be conveyed. , A positioning device was provided. Further, since the stop position is different depending on the type of the work piece, the positioning device is changed.

(3) Problems to be Solved by the Invention In the above-mentioned conventional techniques, there is a problem that a positioning device is required and that the setup change work of the positioning device is troublesome. In addition, there were problems in terms of space for machine arrangement, economy and workability.

(4) Objective Therefore, the object of the present invention was proposed to solve the above-mentioned problems, and it enables cutting work with rough positioning, does not require a positioning device, and further facilitates workability. To provide a cutting condition monitoring device using the load cell described above.

(5) Means for Solving the Problems The present invention is directed to a relative movement direction (Z-axis) of a chuck mounted on a head of a machine tool and holding a workpiece, for example, a steel pipe, and a tool rest supporting the chuck. The load cell is sandwiched between the mounting surface of the base and the chuck, which is orthogonal to the (direction), and the cutting tool mounted on the tip of the spindle moves with the movement of the column and changes from the state of contact with the workpiece to the feed during cutting. It is a device that reads the state of cutting load by changing the voltage and monitors the cutting state.

That is, a base provided on the bed, and a section is provided for gripping a workpiece having a processing portion having a diameter larger than the vicinity of the gripping portion extending in the axial direction in the shape of a cylinder or polygon,
A chuck that is attached to the base by forming a mounting surface on a surface orthogonal to the axial direction of the workpiece, and a chuck provided on the bed and facing the chuck in the axial direction of the workpiece, A tool post to which a cutting tool for machining is attached, a feed motor for relatively moving the workpiece and the cutting tool in the axial direction of the processing object, the processing object and the cutting tool In a machine tool for performing a cutting process on the workpiece by the relative movement and the relative rotation, the main shaft motor for relatively rotating around the axis line is sandwiched between the mounting surfaces of the base and the chuck. A load cell that detects the feed component force of the workpiece during the cutting process as an electric charge, a voltage conversion unit that converts the electric charge of the load cell into a voltage, and a table that displays the output of the voltage conversion unit. Means, setting input means for presetting and inputting, as a reference voltage, a voltage obtained by multiplying the maximum voltage at the time of cutting displayed on the display means by a predetermined ratio, and cutting output from the reference voltage and the voltage converting means. Comparing and discriminating the voltage during machining and comparing and discriminating means for outputting a cutting control signal when the voltage during cutting falls below the reference voltage, and driving and controlling the feed motor and the spindle motor, When the workpiece and the cutting tool are relatively moved and relatively rotated to perform cutting, and when a predetermined time set in advance has elapsed since the cutting control signal was output from the comparison and determination means, the large diameter of the workpiece The control means controls the feed motor and the spindle motor so as to allow the work piece or the cutting tool to escape, when it is judged that the cutting work has been completed up to the work end of the work part. Even if the workpiece is roughly positioned and gripped in the axial direction, the large-diameter machined part of the workpiece is completely processed by continuously performing the cutting process until the cutting control signal is output from the comparison / determination means. It is characterized by finishing processing.

(6) Operation The present invention is mounted on the head of a machine tool, holds a load cell between a chuck and a bed for gripping a work piece, and performs cutting that occurs when the outer diameter of the work piece is processed. The reaction force of the force is detected by the load cell as electric charge, and the detected electric charge is converted into a change in voltage to monitor the cutting state. Therefore, it is possible to perform cutting without precise positioning, and the NC device By working together, cutting can be done easily.

(7) Examples Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a front view of a steel pipe machining head moving type machine tool for explaining the apparatus of the present invention, and FIG. 2 is a view taken in the direction of arrow X in FIG.

In FIGS. 1 and 2, a column 2 is placed on the right upper surface of the bed 1, and the column 2 can slide in the front-back direction, that is, the Z-axis direction by a Z-axis feed motor 3.

A rotatable spindle 4 is mounted below the column 2, and a spindle motor 5 is mounted above the column 2. A cutter head clamping chuck 6 for clamping the cutter head 7 is attached to the tip of the main shaft 4. Therefore, the cutter head 7 is gripped by the cutter head clamping chuck 6. The cutter head 7 is provided with a cutting tool which is a cutting tool 8 preset according to the type of the workpiece W to be cut.

The main shaft 4 is freely rotated at a predetermined rotational speed by a main shaft motor 5 via a pulley 9 and a timing belt 10 which are mounted on the shaft of the motor 5.

On the upper left side of the bed 1, a rigid chuck base 11 for holding the workpiece W is placed. As shown in FIG. 2, the gripping state of the workpiece W by the base 11 of the rigid chuck is such that the chuck claw mounting members 12a, 12 capable of sliding in the left and right directions on both sides of the base 11 of the rigid chuck.
b is placed. Chuck claws 13a and 13b are respectively gripped by the tip ends of the mounting members 12a and 12b in accordance with the outer diameter shape of the workpiece W. Therefore, the chuck claw portion 13
The a and 13b are integrated with the mounting members 12a and 12b and slid in the left and right direction by the cylinders 14a and 14b. The cylinders 14a and 14b are attached to both ends of the base 11 of the rigid chuck.

The workpiece W is gripped by the sliding movement of the chuck claw portions 13a and 13b from the left and right directions, and is roughly positioned in the axial direction of the workpiece.

The load cell 15 which is the main part of the device of the present invention is a base 11
It is held between the rigid chuck 13 and the rigid chuck 13. Spacers 16a, 16 having the same thickness as the load cell 15
b is also sandwiched between the base 11 and the rigid chuck 13 to hold the position of the rigid chuck 13 in parallel.

The load cell 15 has a connecting cable 16 as shown in FIG.
Are connected, and the charge amplifier 17 is connected via the connection cable 16. Further, an instruction recording device 18, for example, a commercially available oscilloscope is connected to the charge amplifier 17.

The reaction force of the cutting force generated at the time of cutting the workpiece W is detected by the load cell 15 as an electric charge (PC). The detected charge (PC) is converted into a voltage (V) proportional to the amount of charge by the charge amplifier 17, and this converted voltage (V)
Is displayed on the screen of the oscilloscope of the instruction recording device 18, which is a display means. The cutting process is monitored while constantly checking the curve displayed on this screen.

The structure of the load cell 15 will be described.

FIG. 4 is a partial sectional view of the load cell 15.

In FIG. 4, the load cell 15 is a ring-shaped crystal plate 20,
It is composed of an electrode 21, a housing 23 with a plug 22, and a polar wall 24. The load cell 15 is set so that the measured force F acts evenly on the ring-shaped surface. Now, due to the mechanical stress, a charge is generated in the crystal of quartz that is directly proportional to the acting force and is independent of the size of the crystal plate 20. (Piezoelectric effect in the vertical direction) The generated charges are collected by the electrode 21 and transferred to the connection portion of the plug 22. The polarities are arranged so that the compressive force produces a negative charge and then converted into a positive voltage by the charge amplifier.

The cutting monitoring state of the outer diameter processing of the steel pipe that is the workpiece W will be described.

Chuck claw portion 13a of the rigid chuck 13 of FIG.
The cylinder 13a is driven by the cylinders 14a and 14b to grip the steel pipe of the workpiece W and roughly position it. As shown in FIG. 5, the cutter head 7 shown in FIG.
Up to 26c, the cutting tools 25a to 25c, that is, the three cutting tools, are set in advance for the shape to be cut, that is, for the outer diameter processing in this embodiment. Then, the column 2 placed on the bed 1 is moved forward by the Z-axis feed motor 3, and the cutter head 7 held by the cutter head clamp chuck 6 is attached to the tip of the spindle 4 by the spindle motor 5. Rotate at required speed.

The column 2 is moved forward by the Z-axis feed motor 3 and comes into contact with the end of the steel pipe which is the workpiece W, and when the outer diameter machining is started, the load cell 15 held between the base 11 and the rigid chuck 13 is held. When the cutting process proceeds in the direction of the arrow as shown in FIG. 6, the load cell 15 detects the reaction force of the cutting force during the cutting process each time, and the charge amplifier 17 converts the charge into a voltage. Then, the cutting state is monitored by detecting the voltage change on the screen of the oscilloscope of the instruction recording device 18 as the cutting time elapses as shown in FIG. The workpiece W'indicated by the two-dot chain line in FIG. 6 is shown before cutting and the workpiece W in the solid line is shown after cutting. That is, in FIG. 7, the horizontal axis represents the time t, the vertical axis represents the load voltage P, and the curve A represents the sixth curve.
The cutting state in which the reaction force at the time of cutting at the time of processing the outer diameter of the steel pipe as shown in the drawing is converted from electric charge to voltage by the load cell 15 is shown. When the cutting tool is brought into contact with the end of the workpiece W while the Z-axis feed rate is kept constant and the cutting process is started, the reaction force of the cutting force rises sharply and then becomes a constant voltage. It is clear from the result of the experiment that the voltage decreases from 0 to 1 and takes a constant voltage value. Thus, the preset Δt
The voltage change Vn is read every (s) and compared with a preset voltage value Vo of about 50% of the voltage during cutting, for example. If it is determined whether Vn ≦ Vo is satisfied, cutting is performed until the condition of Vn ≦ Vo is satisfied, and if the condition of Vn ≦ Vo is satisfied,
The cutting process is completed by retracting the column after a preset time of 0.5 [S] by the timer.

Next, the operation of the device of the present invention will be described.

(B) The steel pipe which is the workpiece W drives the cylinders 14a and 14b as shown in FIG.
The chuck claws 13a and 13b attached to are slid inward so that the chuck claws 13a and 13b are gripped.

(B) As shown in FIG. 5, the cutter head 7 is set with a cutting tool, which is three cutting tools, according to the shape of the steel pipe which is the workpiece W to be cut in advance. Chuck 6 for cutter head clamp shown in Fig. 1
The main spindle 4 is gripped with.

(C) Operate the Z-axis feed motor 3 to move the column 2 forward at a constant speed. Further, the cutter head 7 is rotated by driving the spindle motor 5 to rotate the spindle 4 at a predetermined rotation speed.

(D) When the column 2 moves forward and the cutting tool, which is the cutting tool 8 preset on the cutter head 7, comes into contact with the end of the steel pipe, which is the workpiece W, and the cutting process is started, the base 11 and the rigid The load cell 15 held between the chuck 13 and the chuck 13 detects the reaction force of the cutting force at the time of cutting with an electric charge, and the charge amplifier 17 converts it into a voltage.
Cutting is performed by the voltage change of curve A as shown in FIG.

At this time, the cutting process is monitored based on the flowchart shown in FIG.

(a); Δt [S] For example, the voltage Vn is measured every 0.05 to 0.1 [S].

(b); The voltage value Vo is set to the setting input device L in advance to, for example, about 50% of the voltage at the time of cutting, and the comparison determination circuit M compares Vn measured in (a) above. Therefore, the cutting control signal N
Therefore, continue cutting until the condition of Vn ≦ Vo is satisfied.

(c); When the condition of Vn ≦ Vo is satisfied, a preset timer is activated.

(d); The skip signal of the NC device is activated after 0.5 [S], for example, by the timer, causing the cutting tool 8 to escape and the column 2 to retreat quickly.

With the above operation, the outer diameter processing of the steel pipe as the workpiece W is completed.

In addition to the monitoring of the cutting force in the Z-axis direction, the cutting force in the rotation direction is monitored in the same manner as described above by holding the load cell 15 'between the bed 1 and the base 11 supporting the chuck 13. You can

(8) Effects The device of the present invention holds the load cell between the bed and the chuck that holds the workpiece W, detects the reaction force during cutting by electric charge, and further converts it into a voltage to cut the state. Since it is a device for monitoring, the positioning device that has been conventionally required is unnecessary, and moreover, rough positioning is possible. Therefore, the setup work of the positioning device is eliminated, and the work efficiency is improved. Since this voltage change is discriminated within a certain range and the cutting process is automatically performed by interlocking with the NC device, accurate machining and labor saving of the process can be achieved.

Since a positioning device is unnecessary and only a simple device is arranged on the machine, it is advantageous in terms of space for machine arrangement.

Further, even if the perpendicularity of the cut surface of the workpiece in the previous step is not obtained, it is possible to accurately finish the final shape by the cutting monitoring of the present invention.

[Brief description of drawings]

FIG. 1 is a front view of a steel pipe machining head moving type machine tool for explaining the apparatus of the present invention, and FIG. 2 is a view taken in the direction of arrow X in FIG. FIG. 3 is a system diagram in which the cutting force is changed into voltage in the load cell used in the present invention. FIG. 4 is a partial cross-sectional view of the load cell used in the present invention. FIG. 5 is a side view in which a cutting tool is attached to a cutter head. FIG. 6 is a partial cross-sectional view of a steel pipe to be cut, and FIG. 7 is a voltage change diagram of the cutting force converted into a voltage by a road sail. FIG. 8 is a flow chart for explaining the operation of the present invention. 1 ... Bed, 2 ... Column 3 ... Z-axis feed motor, 4 ... Spindle 5 ... Spindle motor, 7 ... Cutter head 8 ... Cutting tool, 11 ... Base 13 ... Rigid chuck, 13a, 13b …… Chuck claw parts 14a, 14b …… Cylinder, 15 …… Load cell 17 …… Charge amplifier, 18 …… Instruction recording device W …… Workpiece

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Fujio Machii 1 Abiko, Abiko, Chiba Prefecture, within Hitachi Seiki Co., Ltd. (72) Inventor Kazuhiro Nagai 1 Abiko, Abiko, Chiba, within Hitachi Seiki Co., Ltd. (72 Inventor Takeshi Yamamoto 1-1-1, Kawasaki-cho, Handa-shi, Aichi Kawasaki Steel Co., Ltd. Chita Works (56) Reference JP-A-50-79885 (JP, A) JP-A-51-45569 (JP, A) JP-A-56-134155 (JP, A) JP-B-44-3748 (JP, B1)

Claims (1)

[Claims] 1. A base provided on a bed and a work piece having a cylindrical or polygonal cross section and extending in the axial direction and having a processed portion having a diameter larger than the vicinity of the grip portion. A chuck that is attached to the base by forming a mounting surface on a surface orthogonal to the axial direction of the workpiece, and a chuck that is provided on the bed and faces the chuck in the axial direction of the workpiece to process the workpiece. A tool rest to which a cutting tool is attached, a feed motor for relatively moving the workpiece and the cutting tool in the axial direction of the processing object, and the axis of the processing object and the cutting tool A spindle motor for relatively rotating around, in a machine tool for cutting the workpiece by the relative movement and the relative rotation, sandwiched between the mounting surface of the base and the chuck,
A load cell that detects the feed component force of the workpiece during the cutting as electric charge, a voltage conversion unit that converts the electric charge of the load cell into a voltage, and a display unit that displays the output of the voltage conversion unit. Setting input means for presetting and inputting a voltage obtained by multiplying the maximum voltage during cutting shown by means by a predetermined ratio as a reference voltage, and the reference voltage and the voltage during cutting output from the voltage converting means. Comparing and discriminating, and comparing and discriminating means for outputting a cutting control signal when the voltage during cutting becomes equal to or lower than the reference voltage, drive-controls the feed motor and the spindle motor, and the workpiece and the When a cutting operation is performed by relatively moving and rotating the cutting tool, and a predetermined time set in advance has elapsed since the cutting control signal was output from the comparison / determination means. The cutting means is judged to be completed up to the processing end of the large-diameter processing part of the workpiece, and the control means controls the feed motor and the spindle motor so as to escape the workpiece or the cutting tool. Even if the workpiece is roughly positioned and gripped in the axial direction,
A cutting condition monitoring apparatus using a load cell, wherein the large-diameter machined portion of the workpiece is completely machined by continuously performing the machining process until the comparison control unit outputs a cutting control signal. .