JPH0323295B2 - - Google Patents

Description

[Detailed Description of the Invention] (1) Industrial Application Field The present invention relates to a cutting state monitoring device using a load cell when turning a workpiece in a machine tool, particularly a moving head machine tool for machining steel pipes. .

(2) Conventional technology Conventionally, in a machine tool, particularly a moving head machine tool for steel pipe machining, when cutting a steel pipe as a workpiece, it is necessary to accurately position the steel pipe that is being transported. , a positioning device was provided. Furthermore, since the stopping position differs depending on the type of workpiece, the positioning device must be changed.

(3) Problems to be Solved by the Invention The above-mentioned prior art requires a positioning device and requires time and effort to change the setup of the positioning device. Furthermore, there were difficulties in terms of machine layout space, economy, and processability.

(4) Purpose Therefore, the purpose of the present invention was proposed in order to solve the above-mentioned problems.The purpose of the present invention is to enable cutting with rough positioning, eliminate the need for a positioning device, and further facilitate machining. An object of the present invention is to provide a cutting condition monitoring device using a load cell.

(5) Means for Solving the Problems The present invention provides a means for solving problems in the relative movement direction (Z-axis A load cell is sandwiched between the chuck and the mounting surface of the base, which is perpendicular to the direction), and as the column moves, the cutting tool attached to the tip of the spindle changes from the state in which it is in contact with the workpiece to the feed rate during cutting. This is a device that monitors cutting conditions by reading the state of the cutting load based on changes in voltage.

In other words, the load cell is placed on the bed of a machine tool, and the load cell is sandwiched between the chuck that grips the workpiece and the bed, and as the column moves, the cutting tool attached to the tip of the spindle comes into contact with the workpiece. When bevelling the edge of a workpiece, the load cell detects the reaction force state of the cutting force, which changes with the feed rate during cutting, as an electric charge, converts the detected electric charge into a voltage, and then converts the detected electric charge into a voltage. The present invention is characterized in that the cutting state is monitored while instantly comparing and determining the converted voltage change value within a preset voltage value range.

(6) Function The present invention is installed on the bed of a machine tool, and a load cell is sandwiched between the chuck that grips the workpiece and the bed, and the problem occurs when bevel processing is performed on the end of the workpiece. The reaction force of the cutting force is detected as an electric charge by a load cell, and the detected electric charge is further converted into a change in voltage to monitor the cutting condition. This allows cutting to be performed without accurate positioning, allowing NC Cutting can be easily performed by linking it with a device.

(7) Example Hereinafter, one embodiment of the present invention will be described in detail based on the drawings.

Figure 1 is a front view of a moving head machine tool for steel pipe machining to explain the device of the present invention, and Figure 2 is a front view of a moving head machine tool for steel pipe processing.
It is a view taken along the X arrow in the figure.

1 and 2, a column 2 is placed on the upper right side of the bed 1, and the column 2 can be slid in the front-rear direction, that is, in the Z-axis direction, by a Z-axis feed motor 3. As shown in FIGS.

A rotatable main shaft 4 is mounted below the column 2, and a main shaft motor 5 is mounted above it. 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 has a workpiece W to be cut.
A cutting tool 8, which is set in advance depending on the type of tool, is attached.

Note that the main shaft 4 is connected to the motor 5 by the main shaft motor 5.
It rotates freely at a predetermined rotational speed via a pulley 9 and a timing belt 10, which are attached to the shaft of the motor.

A base 11 of a rigid chuck for gripping a workpiece W is placed on the upper left side of the bed 1. The state in which the workpiece W is gripped by the base 11 of the rigid chuck is as shown in FIG. 2, where mounting members 12a and 12b of chuck claws that can slide in the left-right direction are placed on both sides of the base 11 of the rigid chuck. . Chuck claws 13a, 13b are gripped at the tips of the mounting members 12a, 12b, respectively, in accordance with the outer diameter shape of the workpiece W. Therefore, the chuck claws 13a, 13b are attached to the mounting members 12a, 12b.
cylinders 14a, 14 in the left and right direction.
b. Note that the cylinders 14a, 1
4b are attached to both ends of the rigid chuck 13.

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

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

A connection cable 16 is connected to the load cell 15 as shown in FIG. 3, and a charge amplifier 17 is connected via the connection cable 16. Furthermore, an instruction recording device 18, such as a commercially available oscilloscope, is connected to the charge amplifier 17.

The reaction force of the cutting force generated during cutting of the workpiece W is detected by the load cell 15 using the charge PC.
The detected charge PC is converted into a voltage V at a constant rate by a charge amplifier 17, and changes in the converted voltage V are displayed on the screen of an oscilloscope of an instruction recording device 18. The cutting process is monitored by constantly checking the curves displayed on this screen.

The structure of the load cell 15 will be explained.

FIG. 4 is a partial sectional view of the load cell 15.
In FIG. 4, the load cell 15 has a housing 2 with a ring-shaped crystal plate 20, an electrode 21, and a plug 22.
3 and a polar wall 24. The load cell 15 is set so that the force F to be measured acts uniformly on the ring-shaped surface. The mechanical stress now creates a charge in the quartz crystal that is directly proportional to the applied force and independent of the dimensions of the crystal plate 20.
(Vertical piezoelectric effect) The generated charge is collected by the electrode 21 and transferred to the connecting part of the plug 22. The polarity is arranged so that the compressive force produces a negative charge, which is then converted to a positive voltage by a charge amplifier. A cutting monitoring state of end bevel processing of a steel pipe, which is a workpiece W, will be explained.

The chuck claws 13a and 13b of the rigid chuck 13 shown in FIG. 2 are driven by the cylinders 14a and 14b to grasp and roughly position the steel pipe of the workpiece W. As shown in FIG. 5, the cutter head 7 shown in FIG. It is set. Then, the column 2 placed on the bed 1 is moved forward by the Z-axis feed motor 3, and the cutter head 7, which is held by the cutter head clamp chuck 6, is attached to the tip of the main spindle 5 by the main shaft motor 5. Rotate at the required number of rotations.

When the column 2 is moved forward by the Z-axis feed motor 3 and comes into contact with the end of the steel pipe that is the workpiece W, and end bevel processing is started, the load cell 15 held between the base 11 and the rigid chuck 13 is moved. is activated, and as the cutting progresses in the direction of the arrow as shown in FIG. 6, the reaction force of the cutting force during cutting is detected as an electric charge by the load cell 15 each time, and the charge is converted into voltage by the charge amplifier 17. The cutting state is monitored by recording voltage changes on the screen of the oscilloscope of the recording device 18 as the cutting time elapses as shown in FIG. In FIG. 6, the workpiece W' indicated by the two-dot chain line indicates the workpiece before cutting, and the workpiece W indicated by the solid line indicates the workpiece after cutting. That is, in FIG. 7, the horizontal axis is time t, the vertical axis is load voltage P, and curve A is the reaction force during cutting when beveling the end of a steel pipe as shown in FIG. 6 using the load cell 15. This shows the cutting state converted from electric charge to voltage. That is, when the cutter head (Fig. 5) set to perform the bevel processing shown in Fig. 6 is fed at a constant speed in the Z-axis direction, the processing area is changes (increases) and becomes constant from a certain point. Therefore, it is clear from the results of experiments that the voltage changes over time with the Z-axis feeding speed constant, and after a certain amount of time passes, the voltage becomes saturated and takes a constant value.
Then, read the change in voltage at every preset △t(S), and each time K = |1-Vn-1/Vn| (where Vn-1: previous voltage, Vn: current voltage)
Calculate the value of K. The preset voltage change amount ΔS is compared with the calculated K, and cutting is continued until the condition K≦ΔS is satisfied.
When the condition K≦△S is satisfied, the column is retreated after a preset time using a timer, and the cutting process is completed.

Next, another cutting monitoring state in the end bevel processing of the steel pipe, which is the workpiece K, will be explained.

The gripping of the steel pipe as the workpiece W and the attachment state of the cutter head are the same as in the previous embodiment. The cutting process is monitored under adaptive control by changing the Z-axis feed rate during the cutting process according to the cutting process situation. First, the Z-axis feed rate during cutting is set to be adaptively controlled, and if the adaptive control is OK, the voltage V _p of the load cell 15 is first set. Set the feed override to 100% and start cutting.

The value of K is calculated by the formula of K={(V _p /V ₁ )-1}×100 by changing the cutting voltage V ₁ to the actual side for each preset △t [S], and then calculating the value of K. For example, −
Determine whether it falls within the range of 10≦K≦10, and perform cutting by changing the feed override K until the above range is satisfied.

When the value of K satisfies the range of -10≦K≦10, the cutting process is completed, and the adaptive control is turned off.
Column 2 is moved back. Therefore, in the second embodiment, unlike the first embodiment, where the Z-axis feed rate is constant, the Z-axis feed rate is changed and controlled to a speed suitable for each cutting process. They administer and monitor the situation.

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

First, the operation when the Z-axis feed rate is constant will be explained.

(a) The steel pipe that is the workpiece W is processed by driving the cylinders 14a and 14b as shown in FIG.
By sliding 3a, 13b inward,
It is gripped by chuck claws 13a and 13b.

(b) As shown in Fig. 5, four cutting tools 8, which are bits, are set in advance on the cutter head 7 according to the shape of the steel pipe that is the workpiece W to be cut, and the cutter head 7 is set in the first The main shaft 4 is gripped by the cutter head clamping chuck 6 shown in the figure.

(c) Operate the Z-axis feed motor 3 to advance the column 2 at a constant speed. Furthermore, the cutter head 7 is rotated by driving the main shaft motor 5 to rotate the main shaft 4 at a predetermined number of rotations.

(d) When the column 2 moves forward and the cutting tool 8, which is the cutting tool 8 set in advance on the cutter head 7, comes into contact with the end of the steel pipe that is the workpiece W, and cutting starts, the base 11 and the rigid chuck 13 are connected to each other. The reaction force of the cutting force during cutting is detected as an electric charge by the load cell 15 held between the two, and the charge amplifier 17 converts it into voltage, and the cutting process is performed with the voltage change of curve A as shown in Fig. 7. It will be rubbed.

At this time, monitoring of the cutting process is carried out based on the flowchart shown in FIG.

(a); Measure the voltage every △t [S]. (In advance, △t
For example, set 0.05 to 0.1 [S] in the setting input device L. ) (b); Next, the previous voltage Vn− of △tn−1 [S]
1 and the current voltage Vn of Δtn [S], the value of K is calculated using the following formula.

K=|1-(Vn-1/Vn)| (c); The previously set value of △S and K are compared and judged by the comparison judgment circuit M, and the condition of K≦△S is determined by the cutting control signal N. Cutting is performed until the requirements are satisfied.

(d); When the value of K satisfies the condition K≦△S,
Activate a preset timer.

(e); The skip signal of the NC device is activated by the timer after, for example, 0.5 [S], and the column 2 is immediately retreated.

With the above operations, the end bevel processing of the steel pipe, which is the workpiece W, is completed.

Next, an explanation will be given of the operation when cutting is performed by changing the Z-axis feed rate to a speed suitable for the cutting state under adaptive control.

Same as when the Z-axis feed speed is constant (A) to (C) above.
Instead of the steps (a) to (e) in (d), the procedure is performed based on the flowchart shown in FIG. In step (d), the Z-axis feed rate is set in advance to be adaptively controlled.

(a)′; First, set the voltage of the load cell to V _p .

(b)'; Next, set the feed override K to 100% and start cutting.

(c)′; △t of 0.05 to 0.1 [S] at the same time as cutting starts
Measure the voltage V ₁ at each time. Then, the value of K is calculated for each Δt using the formula K={(V _p /V ₁ )−1}×100.

(d)'; For example, compare and determine whether the value of K calculated in step (c)' falls within the range of -10≦K≦10, and does not satisfy the condition of -10≦K≦10. If so, feed back to before (c)′ and repeat.

(e)′; If the value of K is compared and determined at the K step in step (d)′ and the condition of −10≦K≦10 is satisfied, the cutting process is completed and the adaptive control is turned off. Column 2 is retracted.

In addition to monitoring the cutting force in the Z-axis direction, the cutting force in the rotational direction is
Monitoring can be performed in the same manner as described above by holding the load cell 15' between the base 11 supporting the load cell 15'.

(8) Effects The device of the present invention has a load cell sandwiched between the bed and the chuck that grips the workpiece W, detects the reaction force during cutting as an electric charge, and converts it into voltage to determine the cutting state. By using a device that monitors the positioning, the positioning device that was conventionally required is unnecessary, and moreover, rough positioning can be used. Therefore, there is no need to change the setup of the positioning device, improving work efficiency. This voltage change is determined within a certain range and cutting is performed automatically by linking with an NC device, resulting in accurate machining and labor-saving machining.

This eliminates the need for a positioning device and only requires a simple device to be placed on the machine, which is advantageous in terms of machine layout space.

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

[Brief explanation of the drawing]

FIG. 1 is a front view of a moving head machine tool for machining steel pipes for explaining the apparatus of the present invention, and FIG. 2 is a view taken in the direction of the X arrow in FIG. FIG. 3 is a system diagram for converting cutting force into voltage using a load cell used in the present invention. FIG. 4 is a partial sectional view of a load cell used in the present invention. FIG. 5 is a side view of the cutting tool attached to the cutter head. FIG. 6 is a partial cross-sectional view of the steel pipe to be cut, and FIG. 7 is a voltage change diagram of the cutting force converted into voltage by the road sail.
FIG. 8 is a flowchart for explaining the operation of the present invention, and FIG. 9 is another flowchart for explaining the operation of the present invention. DESCRIPTION OF SYMBOLS 1...Bed, 2...Column, 3...Z-axis feed motor, 4...Main shaft, 5...Main shaft motor, 7...Cutter head, 8...Cut tool, 11...Base, 13...Rigid chuck, 13a, 13b...Chuck claw part, 1
4a, 14b...Cylinder, 15...Load cell, 1
7...Charge amplifier, 18...Instruction recording device, W...
Workpiece.

Claims (1)

[Claims] 1. A chuck provided on a base placed on a bed and gripping a workpiece, a tool rest provided on the bed facing the chuck, and a chuck for holding a workpiece held by the chuck and a tool rest. In a machine tool that performs machining by relative movement and relative rotation in the Z-axis direction, the chuck is held between the chuck mounting surface and the chuck, which is perpendicular to the direction of relative movement with the tool rest on the base, and the reaction of the cutting force is converted into an electric charge. A load cell to be detected, a voltage converting means for converting the electric charge of the load cell into a voltage, a means for setting the electric charge at the time of finishing as a voltage value, a comparing and determining means for comparing and determining the voltage value and an actual measurement value, and the comparing means. It consists of a control means that terminates the machining based on a signal from the discrimination means, and when machining the end face and bevel machining of the workpiece by constant speed relative movement of the workpiece and the tool rest in the Z-axis direction, the tool contacts the workpiece and cuts. The reaction of the cutting force that changes with the feed during cutting from the starting state is detected as an electric charge, the electric charge is further converted to voltage, and the voltage change value is compared and determined within a preset voltage value range over time. A cutting state monitoring device using a load cell, characterized in that the machining state is set to the final machining position when a voltage that increases sequentially shows a constant value.