JP2814278B2 - Two-spindle opposed type CNC lathe and work processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION << Industrial application field >> The present invention relates to a machine tool for processing a rotary-shaped workpiece, and relates to two spindle heads and two processing opposing on one base. Combined CNC with unit
(Computer numerical control) This relates to a lathe.

<Conventional technology> Conventional compound lathes are equipped with a mechanical indexing device equipped with an independent servo motor in addition to the spindle motor. When performing milling or drilling, the spindle is stopped once and the indexing device is stopped. And the spindle were mechanically connected, and the indexing device was used to precisely control the rotation and positioning of the spindle. in this case,
It is very difficult to reduce the time required to disengage the spindle and the indexing device below a certain limit time, and since the spindle is driven via a speed reducer during indexing operation, the rapid traverse speed during indexing must be reduced. There was also a limit, and a crisp indexing operation could not be performed, resulting in a large loss in working time.

Also, when a workpiece is transferred from the first spindle to the second spindle in the flange material processing, or when the workpiece is cut off by cutting the work in the bar material processing, the workpiece is gripped by the chuck of the second spindle before the workpiece is gripped. It is necessary to stop both the first and second spindles at the origin by orienting them, or to stop the two spindles at the predetermined delivery angle in phase. In this case, the same operation as in the above-described indexing operation is required. Along with the loss of time, the time loss required for re-acceleration of the spindle after stopping cannot be ignored. Especially in the case of bar material processing,
It is necessary to accelerate the workpiece to a predetermined speed in a short time in a state where the workpiece is gripped by the first and second two spindles for parting off, and during the acceleration, the rotation phase of the first spindle and the second spindle is changed. If the synchronization is lost, a trouble occurs in which the chuck slips to damage the work or torsionally deform the work. In order to avoid this problem, various types of synchronous control and torque control during synchronous operation have been proposed.

<< Problems to be Solved by the Invention >> However, at present, there is an extremely high demand from users for shortening the machining time, such as shortening the machining time by shortening the acceleration time of the spindle by using a large-capacity motor for the spindle motor. As mentioned above, the time loss at the time of spindle indexing, the time loss required for phase adjustment of the spindle at parting off, and the time loss due to the slow acceleration at the time of spindle acceleration by the conventional method of synchronous control and torque control Is becoming unacceptable.

Therefore, instead of a structure in which a spindle indexing device is mechanically engaged with and disengaged from the spindle, a structure in which the spindle motor for turning is directly servo-controlled to index the spindle has been proposed. However, the first
In connection with the transfer of the workpiece from the spindle to the second spindle, the first
There is a problem that the phase relationship between the main spindles must be accurately transmitted to the second main spindle. Therefore, the spindle orientation or the spindle indexing is performed electrically. In particular, in the case of bar processing, the main spindle must be accelerated to a predetermined rotation for parting off in the state of gripping both sides of the work, but the start-up acceleration at this time is different from the acceleration of each axis alone, If they are not rotated in a synchronized state, slippage of the chuck jaws and torsional deformation of the work occur. In the conventional technology, when high-speed acceleration is performed, synchronization is not achieved, and it is necessary to perform acceleration slowly. Therefore, there is a problem that a time loss required for the acceleration is large. Further, it is difficult to electrically accurately match the phases of the two spindles, and the phase error at the time of workpiece transfer is an error between the indexing position of the first spindle and the indexing position of the second spindle. This is an obstacle to improving the indexing accuracy.

It is an object of the present invention to solve the problems as described above and to obtain technical means capable of efficiently and accurately performing machining including transfer of a work between two opposing main spindles.

<< Means for Solving the Problems >> The present invention solves the above problems by providing technical means for accurately synchronizing the speeds and phases of the two spindles while rotating the spindles.

In the CNC lathe according to the present invention, the first spindle head 2a of the two spindle heads is substantially integrally fixed to the common base 1, and the second spindle head 2b is moved and positioned on the base 1 only in the Z-axis direction. Turret-type first machining unit 3a corresponding to the first spindle head 2a is mounted so as to be movable and positioned in the X and Z-axis directions, and the second spindle head is mounted.
A turret type second processing unit 3b corresponding to 2b is mounted so as to be movable and positioned only in the X-axis direction. The first spindle 11a is supported by the first spindle head 2a, and the first spindle motor 2
A first spindle encoder 27a, which is driven by 1a and detects the rotation angle, is provided. Similarly, the second spindle 11b is supported by the second spindle head 2b, is driven by a second spindle motor 21b, and has a second spindle encoder 27b for detecting a rotation angle thereof.

The first and second spindle encoders 27a and 27b include an origin slit 26 for detecting the origin of the spindle, a unit angle slit 24 for accurately detecting the rotation angle, and a reference angle slit 25 provided for each of a predetermined number of unit angle slits. Have. These spindle encoders 27a and 27b output a rotation speed signal, an origin position signal, a unit angle position signal, and a reference position signal of the respective spindles 11a and 11b to the control device.

The NC device 50 includes a spindle control circuit including servo drive units 52a and 52b and speed command correction circuits 58a and 58b (FIG. 10).
, The first and second spindle motors 21a and 21b are controlled. A spindle control circuit that controls the first and second spindle motors receives signals from the first and second spindle encoders 27a and 27b based on a command from the NC device 50, and outputs synchronization control means 53 that is output based on these signals. 1st and 2nd receiving the correction command from
The spindles 11a and 11b are driven to rotate, and a predetermined angular positioning control is performed. The signal of the main spindle encoder 27b of the second main spindle is inputted to the synchronous control means 53 and receives a correction command of a second main spindle indexing angle correcting means 61, which will be described later, to drive the second main spindle 11b to rotate and to rotate the second main spindle 11b at a predetermined angle. Controls positioning.

The synchronization control means 53 includes a slow discrimination circuit 54, a phase discrimination circuit 59.
And a correction command circuit 56. The phase discrimination circuit 59 receives the outputs of the first and second spindle encoders 27a and 27b and detects the phase difference between the first and second spindles 11a and 11b rotating at a constant speed. In order that this phase difference matches the predetermined delivered phase difference that has been input in advance, the servo drive unit has a phase adjustment function of giving a phase command or a phase command to each servo drive unit. During the synchronous rotation of the first and second spindles 11a and 11b, the signals from the first and second spindle encoders 27a and 27b are received and compared to detect a difference in rotation speed between the two spindles. It has a synchronization command function for giving a minute speed correction command to the first spindle servo drive unit 52a and the second spindle servo drive unit 52b every minute time so as to eliminate them.

The synchronization control means 53 uses, as the main spindle encoders 27a and 27b, one having an origin position slit 27, a unit angle slit 24 and a reference angle slit 25, and performs coarse synchronization based on a pulse of the reference angle slit from the origin position. Control is performed, and after synchronization with the roughness is obtained, switching to synchronization control with the accuracy of the unit angle slit is performed.

Further, the apparatus of the present invention includes a second spindle indexing angle correction means 61 for detecting and storing a phase error when the first and second spindles 11a and 11b both grip the same work 80,
A function of correcting the index angle command from the NC device 50 to the second spindle control circuit with the phase error stored in the means 61, and resetting the stored value when the machining of the work by the second spindle 11b is completed. Can be provided.

Further, in the apparatus of the present invention, the first and second spindles 11a, 11b
Are respectively provided with spindle brake devices 22a and 22b capable of variably controlling the braking force, and the first and second spindle motors 21a and 21b are provided.
By maintaining the rotational force required for indexing at a predetermined value set irrespective of the variation of the cutting reaction force, chatter vibration of the spindles 11a and 11b during contouring is prevented.

In the processing including the transfer of the work between the first main spindle and the second main spindle in the above-described apparatus, the work 80 which is a workpiece is gripped by the first main spindle 11a, and the cooperation between the first main spindle and the first processing unit is performed. A first step of performing a first-stage machining on the workpiece by the operation, and advancing toward the first main shaft 11a while rotating the second main shaft 11b, so that the first main shaft 11a and the second main shaft 11b are synchronized in phase. Alternatively, after controlling the synchronous speed to a predetermined phase difference, the tip of the work 80 is gripped by the second spindle 11b, and the phase error between the first spindle and the second spindle when the grip is performed (from the phase relationship specified by the command). Error), and the first spindle 11a and the second spindle 1 when the workpiece 80 is a bar.
In the state where the workpiece 80 is gripped with the workpiece 1b, the workpiece is cut off by cutting off the workpiece 81 at the tip, and when the workpiece 80 is a flange material, the gripping of the first spindle 11a is released. A third step of separating the main spindle 11a from the main spindle 11a, and controlling the phase of the second main spindle by correcting the command value given to the second main spindle 11b from the NC device 50 with the stored phase error. A fourth step of performing the second stage processing on the workpiece 81 or the workpiece 80 transferred to the second spindle 11b in the third step by the cooperative operation with the second processing unit 3b and then discharging the workpiece without the workpiece; Are performed sequentially. The first step for the second workpiece is performed simultaneously with the fourth step for the preceding workpiece or workpiece.

<< Operation >> In the present invention, the synchronous acceleration start-up which causes a lot of time loss is stopped, and if the first spindle 11a is rotating at the completion of machining on the first spindle 11a, the first spindle 11a is kept rotating, and if the milling hole is stopped, the second spindle 11 is stopped. Before gripping the work 80 with 11b, the first spindle alone accelerates to a predetermined rotation, and the second spindle 11b accelerates independently during the approaching operation to the first spindle side for receiving the work 80, The workpiece is transferred while maintaining a specific phase relationship and rotating synchronously. By doing so, the work 80 is moved from the first spindle 11a to the second spindle 11b.
It is possible to minimize the acceleration time of the spindle when delivering the workpiece.

When the second spindle 11b grips the work 80, the first spindle 1b
The phase relationship between 1a and the second spindle 11b must be a predetermined phase relationship required for delivery of the work 80 (usually a phase difference of zero). Therefore, synchronous control is performed at the time of completion of acceleration. As a method of synchronizing, first, in the first stage, the output signals of the spindle encoders 27a and 27b of the first spindle and the second spindle are compared with respect to the origin slit 26 as a reference. The reference angle slit 25 is counted, and the phase difference between the reference angles is detected every minute time, and the phase advance and retardation commands set in advance to a constant value are added to the speed commands given to the respective spindle servo drive units. When a predetermined phase difference is provided between the two spindles at the time of transfer of the work, the count value is compared with a desired phase difference. With this control, the phases of the first main shaft and the second main shaft can be accurately and promptly matched with the roughness of the reference angle slit without causing hunting. Next, as a second stage, the spindle encoders 27 of the first and second spindles are used.
The output signals of a and 27b are compared, the unit angle slit 24 is counted based on the reference angle slit 25 in a synchronized state, and the slowness and the minute phase difference of the rotational speeds of the two spindles are determined every minute time. And a method of simply adding or subtracting a correction value set in advance to a constant value to a speed command given to the servo drive units 52a and 52b of the second spindle is adopted. As a result, it was possible to stably maintain the first and second spindles 11a and 11b, which have a slight speed difference, at a synchronized speed and maintain a precise phase relationship.

When the gripping of the work 80 by the second spindle 11b is completed, the phase relationship between the first spindle and the second spindle at that time is fixed, and the error from the expected phase relationship at that time is stored as a phase error in the memory. The phase error is stored in the second spindle 11 after finishing the workpiece parting-off in the case of bar machining, and after releasing the grip of the first spindle in the case of flange machining.
When performing the indexing process in b, the indexing angle is corrected as a correction value for the indexing angle command value of the NC device 50. As a result, the indexing position on the second spindle can be accurately matched with the indexing position on the first spindle.

If the second spindle attempts to grip the workpiece when there is hunting during synchronous rotation, a nail defect due to a difference in speed occurs at the moment of gripping. In order to suppress this, according to the present invention, the leading and lagging commands are set to constant values regardless of the magnitude of the phase difference, and the values are set to small values enough to avoid hunting of the main spindle based on the sudden acceleration / deceleration commands. . Furthermore, in the synchronous detection during rotation, the number of slits in the encoder increases as the precision of detection is increased, and the count value of the slit during rotation increases, making it difficult to perform quick response control.
Therefore, in addition to the precise unit angle slit, a reference angle slit having a relatively coarse pitch is provided and counted. By counting this, the two spindles having a large phase difference are smoothly and quickly synchronized to a coarse level, and then the fine unit The work is gripped in a state where the number of angular slits is counted and the phase relationship between the two spindles is maintained at a precise level.

<< Examples >> (1) Overall Configuration (See FIGS. 1, 2, and 3) In the description of the present invention, a main axis direction is referred to as a Z axis direction, and a direction orthogonal to the Z axis is referred to as an X axis direction (FIG. 1). reference). In the figure, 1 is a base, 2a is a first spindle head, 2b is a second spindle head, 3a is a turret type first processing unit processing unit, 3b is the second processing unit, 4 is a chip storage box,
5 is a chip conveyor. The base 1 is a slant type in which the upper surface is inclined forward by 45 degrees, and the second spindle head 2b slides only in the Z-axis direction via the Z slide 6 in opposition to the first spindle head 2a fixed to the base. The processing units 3a and 3b are movably disposed behind the spindle heads 2a and 2b. The first processing unit 3a is slidable in both directions of the Z axis and the X axis via a ZX slide 7 having a Z slide and an X slide, and the second processing unit 3b is movable in the X axis direction via an X slide 8. Only slidably mounted.

Each of the processing units 3a and 3b includes turrets 9a and 9b equipped with a plurality of tools including rotating tools such as a milling cutter and a drill.
The tools are selected by indexing drive at a and 10b, and the machining unit 3 is selected by the face gear joint at each index position.
a, 3b firmly fixed. The rotary tool mounted on the turret is driven to rotate by milling motors 39a and 39b. The work mounted on the first spindle head 2a is processed by the tool of the first processing unit 3a, and the work mounted on the second spindle head 2b is processed by the tool of the second processing unit 3b.

Each slide 6, 7, 8 has its own feed motor 12a, 12
b, 13a, 13b, a feed device consisting of feed screws 14a, 14b, 15a, 15b and a ball nut (not shown) is provided, and by controlling the rotation angle of the feed motors 12a, 12b, 13a, 13b, the second spindle head is provided. 2b and the first and second processing units 3a,
The movement positioning of 3b is performed.

Since the device of this embodiment employs a 45-degree slant type base, chips can be quickly discharged, workability at the time of tool change of the turret is good, and the loader or unloader can be moved upward or forward of the machine. Can be arranged at any position, and an average load acts on the slide surface of the second spindle head 2b and the machining units 3a and 3b, so that the spindle head and the machining unit can be precisely stabilized. is there. In an actual structure, three slide ways are cut and formed integrally on the upper surface of the base 1 to increase rigidity and reduce an increase in cost due to a building block.

(2) Chip storage box (see FIGS. 2 and 3) The chip storage box 4 is separately disposed below the front edge of the base 1 and is formed between the two spindle heads 2a and 2b. The upper surface of the base 1 in the processing area is
It is covered with a telescopic cover 18 mounted between the slide 6 and the first spindle head 2a. A chip conveyor 5 is arranged on the bottom surface of the chip storage box 4 in the lateral direction. Therefore, the chips generated in the processing area slide down on the cover, fall into the chip storage box 4, and are quickly discharged to the machine side by the chip conveyor 5.

In turning, in order to complete roughing in as little time as possible, a heavy-cutting tool is used, the workpiece is rotated at high speed, and the tool is fed at high speed to perform rough cutting. As a result, a large amount of processing heat is generated, so cutting chips are cooled by applying cutting fluid, and the generated chips are quickly removed from the processing area to prevent thermal deformation of machines and workpieces and maintain high processing accuracy. Is an important requirement for Therefore, in this type of machine, the processing of chips is one of the most important problems, and the machine of this embodiment solves this problem by adopting the above structure. The chip conveyor 5 can be configured to discharge chips to the rear of the machine. However, the rear discharge type needs to be configured to collect chips toward the center of the chip storage box. Maintenance work is inconvenient because the conveyor passes through the conveyor, and since a large number of control devices are generally arranged on the back of the machine, it is not preferable for maintenance of the control devices.

(3) Spindle drive (refer to FIGS. 1 and 4 to 7) For the spindle head 2 (when the reference numerals with the suffixes a and b are shown without distinction, the suffixes without the suffixes are used. The same applies hereinafter). A spindle 11, a chuck 19 fixed to the spindle, a chuck cylinder 20 for opening and closing the chuck, a spindle motor 21, a brake device 22, and an encoder 27 are mounted respectively. The main shaft motor 21 drives the main shaft 11 by the transmission of the V-belt 28. The structure shown in FIG.
Large-diameter high-resolution encoder 27 that outputs 10,000 pulses
The structure shown in FIG. 5 is a structure in which a general encoder 27 is connected to the main shaft 11 via a timing belt 29, which is convenient for maintenance of the main shaft.
The scale line pulse of the encoder 27 is divided electrically four times,
It is common practice to obtain five times the resolution and
Since the double evaluation method can be adopted, the spindle 1
It is not difficult to achieve an accuracy of 360,000 pulses per revolution. As shown in FIG. 6, the main spindle encoder 27 has a minute interval unit angle slit 24 as a minimum detection unit,
A reference angle slit 25 for generating a reference angle pulse for each predetermined angle and an origin slit 26 for detecting the origin position of the spindle 11 are provided.

An AC servomotor is used for the spindle motor 21,
The NC device 50 that controls this is a servo drive unit 52
The spindle motor 21 is feedback-controlled via the.
A reference numeral 58 in FIG. 7 is a speed command correction circuit described later. The NC device 50 is switchable between a speed control mode and a C-axis position control mode, and switches the mode by operating a relay according to a program. The speed signal of the spindle 21 detected by the spindle encoder 27 is fed back to the servo drive unit 52 to control the current of the spindle motor 21 by a difference signal from a speed command given from the NC device 50, and detected by the spindle encoder 27. The obtained phase signal of the spindle 21 is fed back to the C-axis position control circuit of the NC device 50, and provides a control signal to the servo drive unit 52 based on a difference signal from a position command given from the arithmetic circuit.
During turning, the spindle motor 21 is controlled in the speed control mode, and during indexing and contouring, C is controlled.
The spindle motor 21 is controlled in the shaft position control mode. Details of such control are disclosed in, for example, Japanese Patent Application Laid-Open No. 62-35907.

(4) Brake device (see FIGS. 8 and 9) The brake device 22 operates in the C-axis position control mode, clamps the main shaft 11 with full force when maintaining the main shaft angle, and uses the same for contouring. The control force is automatically controlled and a half brake is applied. In the present embodiment, a disk brake is adopted, which is composed of a brake disk 31 fixed to the main shaft 11, a brake shoe 32 and a brake cylinder 33 which sandwich the brake disk 31, and controls the hydraulic pressure of the brake cylinder 33 to adjust the braking force. ing. Brake device shown
Reference numeral 22 is attached to the spindle head 2 via a bracket 34.

Here, the operation of the brake device 22 will be described in detail with reference to FIG. For example, when the contouring milling is intermittent cutting, the main shaft 11 may vibrate. The brake device 22 is mounted to absorb such a signal, that is, chatter, and applies a brake to the main shaft 11 to change the braking force according to the magnitude of the machining reaction force. In the present embodiment, a servo drive unit 52 that controls the spindle motor 21
A measuring device 36 for measuring the driving force is attached to the motor, and the output signal is guided to a brake control device 37. The signal output from the brake control device 37 enters a pressure control servo valve 38, which adjusts the hydraulic pressure of the brake cylinder 33. Here, the output of the spindle motor 21 when the spindle 11 is rotated at a low speed for milling with only the brake load is set to a predetermined value (when the brake is not applied, a very small output is output). The brake hydraulic pressure is adjusted in advance so as to achieve a balance. And the spindle motor
When the load of 21 becomes larger, the brake pressure is automatically adjusted by the control device 37 in the direction of releasing the brake by that amount. As a result, the braking force decreases as milling starts and a load is applied, and the spindle motor 21 continues to rotate while maintaining a constant output range. The torque does not fluctuate, the vibration of the main shaft is effectively suppressed, and machining can be performed stably.

As the automatic control brakes, in addition to the hydraulic brakes shown in the present embodiment, all-electric brakes having high responsiveness have been put to practical use, and it is of course possible to employ them according to the purpose.

(5) Synchronous control means (see FIGS. 10 to 14) FIG. 10 shows details of control blocks of the spindle motors 21a and 21b in the speed control mode. First and second spindle motors
When the individual operation is performed, the servo drive units 52a, 52b receive individual speed commands from the NC device 50.
2b individually controls its speed. The synchronization control means 53 enclosed by an imaginary line includes a slow discrimination circuit 54, a phase discrimination circuit 5
9. It comprises a correction value setter 55, a correction command circuit 56 and a switch 57. The slow discrimination circuit 54 and the phase discrimination circuit 59 count the output pulses of the main spindle encoders 27a and 27b in a very short time in milliseconds, and a phase difference or a speed difference occurs between the first main spindle and the second main spindle depending on the magnitude thereof. I'm monitoring for

FIG. 11 shows an example of the slow discrimination circuit 54, in which the count pulses of the spindle encoders 27a and 27b are cut out at a predetermined width, counted by the counters 63a and 63b, and the difference is discriminated by the comparator 64. Things.

The reference angle pulses generated by the spindle encoders 27a and 27b are input to AND gates 69a and 69b that cut out count pulses via one-shot circuits 66a and 66b, AND gates 67a and 67b, and OR gates 68a and 68b.

On the other hand, the acceleration signals and the deceleration signals of the spindle motors 21a and 21b are supplied to the OR gates 70a and 70b by a common signal (acceleration / deceleration signal) Pa,
Pb is supplied to the AND gates 67a and 67b through the OR gate 73a73b of the next stage and is also supplied to the OR gates 68a and 68b via inverters 71a and 71b. The OR gates 73a and 73b are supplied with a precision synchronization command (which is transmitted by the correction command circuit 56), which will be described later, in addition to the signals Pa and Pb. Further, a one-shot circuit 72 for defining the cut-out width of the count pulse is provided. This one-shot circuit is triggered by a timing pulse TP given at a predetermined time interval (sampling time interval), and its output is cut-out and gates 69a, 69b. Input signal. The acceleration signal and the deceleration signal may be output, for example, when the previous and previous count values of the counters 63a and 63b are compared with the previous count value and are larger or smaller than an allowable value.

In the above configuration, when the spindles 11a and 11b are operating at a constant speed, the acceleration / deceleration signals Pa and Pb become L level, and the inverter
Since the outputs of the OR gates 68a and 68b maintain the H level due to the inversion of 71a and 71b, the count pulse is cut out by the pulse width of the one-shot circuit 72 (FIG. 14 (a)). If there is a speed difference between the first spindle 11a and the second spindle 11b, a difference occurs between the count values of the first counter 63a and the second counter 63b, and the magnitude is discriminated by the comparator 64. . Also, when the spindles 11a and 11b are accelerating and decelerating, the output of the spindle encoders 27a and 27b starts after the pulse of the one-shot circuit 66a and 66b triggered by the reference angle pulse rises after the pulse of the one-shot circuit 72 rises. Since the pulses are counted, the count start time of the earlier phase becomes earlier, and the count value of the earlier phase becomes larger even if the speed is the same (FIG. 14 (b)). Accordingly, by comparing the count values of the first counter 63a and the second counter 63b as in the case of the constant-speed rotation, the discrimination of the slow speed is determined by discriminating the phase difference.

FIG. 12 shows an example of the phase discrimination circuit 59, in which the reference angle pulses of the first and second spindle encoders 27a and 27b are cut out by the timing difference between the origin pulse of the own spindle and the origin pulse of the mating spindle encoder. First and second counters 43a, 43b
, And the count difference is compared by the comparator 44, and the spindle 11
The phase difference between a and 11b is discriminated.

That is, the gate circuits (flip-flops) 41a and 41b are set by their own origin pulses of the main spindle encoders 27a and 27b, and the respective gate circuits 41a and 41b are reset by the origin pulses of the mating main spindle encoders 27b and 27a. By opening the AND gates 42a, 42b with the outputs of the circuits 41a, 41b, the respective spindle encoders 27a, 27b between them are opened.
Are counted by the counters 43a and 43b. As a result, the counters 43a and 43b count the number of reference angle pulses between the origin pulses on the first spindle side and the second spindle side as shown in FIG. 13, so that the magnitude of these two count values is determined by the comparator. 4, it is determined that the phase of the smaller number of spindles is too advanced (correction can be made earlier than making the reverse determination), and a correction command is issued in accordance with the correction command circuit 56 in FIG.
Command. By the above control, the phase difference between the first main spindle and the second main spindle is reduced, and when a signal indicating that the counter value of the smaller number has become zero is output, the precise synchronization command from the correction command circuit 56 is delayed. It is provided to a discrimination circuit 54.

When a precise synchronization command is given from the correction command circuit 56 to the slow discrimination circuit 54, a signal equivalent to the acceleration / deceleration signal P is output from the OR gate 73 in FIG. 11 with the signal, and the spindle 11a is connected to the spindle 11a even during constant speed operation. The phase difference of 11b is counted by the counters 63a and 63b, and the correction of the phase difference of FIG. 14 (b) is performed based on the count difference. When the count difference reaches a predetermined minimum value (dead value), the precise synchronization command of the correction command circuit 56 disappears, and the process returns to the speed difference detection control to suppress hunting of the main shaft.

In the correction value setting unit 55 in FIG. 10, a speed correction value to be given for each unit time interval is set. This correction value can be given by an NC program. Correction command circuit
56 receives the outputs of the slow discrimination circuit 54 and the phase discrimination circuit 59 and gives the correction value set in the correction value setting device 55 to the speed command correction circuit 58 as a subtraction or addition command. Of course, a correction value is given as a deceleration command to the side where the phase or speed is advanced, and as an acceleration command to the side where the phase or speed is delayed.

When the switching device 57 is switched to the synchronous control by the NC device 50,
The speed command on the first spindle side is transmitted to the first and second motor control units 52.
a, 52b, and the output of the correction command circuit 56 is supplied to speed command correction circuits 58a, 58b, and the speed command from the NC device 50 is corrected by the speed command circuits 58a, 58b, and the servo drive units 52a, 52b To control the first main shaft 11a and the second main shaft 11b to operate synchronously at a constant speed. At first, the zero count signal is not output from the comparator 44 (FIG. 12) of the phase discriminating circuit 59, and the comparator 64 of the slow discriminating circuit 54 (No.
There is no minimum signal from Fig. 11). At this time, the correction command circuit 56 gives priority to the signal from the slow discrimination circuit 54,
The speed control is prioritized ignoring the signal from the phase discrimination circuit 59.

When this control is in a stable state, a minimum signal is returned from the comparator 64 in FIG. 11, so the correction command circuit 56 receives this signal, ignoring the signal of the slow discrimination circuit 54 and the signal of the phase discrimination circuit 59. Is switched to the control giving priority to. Then, when the phase difference between the first main shaft 11a and the second main shaft 11b with respect to the origin phase is reduced and becomes the same phase due to the roughness of the reference angle pulse, the count discrimination circuit 59 returns a zero count signal (FIG. 12). In response to this, the correction command circuit 56 issues a precise synchronization command to the slow discrimination circuit 54, and at the same time, the correction command circuit 56 ignores the signal of the phase discrimination circuit 59 and gives priority to the signal of the slow discrimination circuit 54. Switch to Here, the slow discrimination circuit 54 switches to the precise phase control, and outputs precise phase correction signals for the first and second spindles. In response to this, the correction command circuit 56 executes precise phase matching control. When this control is completed, the minimum signal is returned again, so the correction command circuit 56
Completes the precise synchronization command, and sends a synchronization completion signal (FIG. 10) to the NC device 50. After that, since the correction command of the precise constant speed control is automatically given to the servo drive unit, the synchronization state is continued.

In the above embodiment, the synchronization control means is shown by a hardware configuration for easy understanding. However, it is also possible to configure the synchronization control means by software of a computer. In practice, the software configuration is more flexible. Is more preferred because

(6) Description of Processing Method (See FIGS. 16 (a) to (d)) The first processing unit 3a is provided with a positioning stopper 16 for abutting the tip of the bar 80. When performing bar processing, the first processing unit 3a is moved to move the positioning stopper 16 to a predetermined position on the spindle axis.
Next, a bar 80 is inserted from a bar feeder (not shown) through the first main shaft 11a until the bar 80 collides with the stopper 16, and the bar 80 is inserted.
The feed length of the bar material 8 with the chuck 19a of the first spindle.
Hold 0. In this state, the first spindle 11a and the first machining unit 3a cooperate with each other to perform the first turning such as the turning on the tip of the bar 80 and the drilling, milling, and contouring milling performed by indexing the spindle. The processing at the steps is performed as necessary using a cutting tool 83a, a drill 84a, a milling cutter 85a, and the like mounted on the turret 9a of the first processing unit. The indexing of the first spindle 11a at the time of indexing is performed with reference to the origin slit 26 of the first spindle encoder 27a (FIG. 16 (a)). When the first-stage machining on the first spindle 11a is completed, the first spindle 11a and the second spindle 11b are precisely rotated at the same phase and at the same speed while the second spindle 11b is moved closer to the first spindle 11a. Let it. The control at this time is performed by the method described above, and the minimum signal is output from the comparator 64 in FIG. 11 while the precise synchronization command is output from the correction command circuit 56 in FIG. 10, and the synchronization completion signal is output. The tip of the bar 80 is gripped by the chuck 19b of the second spindle when sent to the NC device 50, and the phase error between the first spindle 11a and the second spindle 11b when gripped is stored as a correction value (16th row). Figure (b).

Regarding the storage of this phase error, when the above-mentioned precise synchronization command is issued, the switches 45a and 45b in the phase discrimination circuit shown in FIG. 12 are switched, and the unit angular pulses of the spindle encoders 27a and 27b are supplied to the counters 43a and 43b. So that the reference angle pulse is supplied to the gate circuits 41a and 41b in place of the origin pulse of the spindle encoders 27a and 27b,
Each time the reference angle pulse is issued, the sign of the comparator 44 is sent to the memory 48 of FIG. 15 and the count values of the counters 43a and 43b are sent to the calculation circuit 46, and the moving average value of the difference is calculated by the calculation circuit 46. The code and the average value when the second chuck 19b grips the bar 80 and the NC device 50 outputs the clamp completion signal are stored in the memory 48, and the second spindle angle command correction circuit 49 This can be realized by setting as a correction value. The unit angle pulse of the spindle encoders 27a and 27b is the spindle 1
Since the order is 360,000 pulses per revolution,
A large-capacity counter is required to count the unit angle pulse for each rotation of the main shaft. However, since the phase synchronization with the roughness of the reference angle pulse has already been taken, the counter for each angle corresponding to the reference angle slit 25 is required. The unit angle pulses may be counted. If the input pulses are switched by the switches 45a and 45b, the number of the counters 43a and 43b is about three digits, and high-speed tracking is possible. The moving average value of the gripping phase error output from the calculation circuit 46 always indicates the average value of the latest several phase errors, which is opened by the clamping completion signal of the second spindle to open the AND gate 47. This input signal is ignored after being recorded.

When the correction value is set in the second spindle angle command correction circuit 49 as described above, thereafter, the second spindle encoder 27b
Is given to the NC device 50 corrected by the correction value.

Next, the workpiece 81 is cut off from the tip of the bar 80 by a parting-off tool 86 while the bar 80 is gripped by both the spindles 11a and 11b and is rotating synchronously. When this parting off is completed,
The NC device 50 switches the switch of the switch 57 of FIG. 10 to the individual operation to end the synchronous control, and returns the second spindle 11b to the original position (FIG. 16 (c)).

Then, with respect to the work piece 81 gripped by the second main spindle 11b, the second main spindle 11a and the second processing unit 3b cooperate to perform turning and drilling by indexing the main spindle.
The second stage processing such as milling processing and contouring milling processing is performed by the tool attached to the second processing unit 3b.
83b, drill 84b, milling cutter 85b, etc., as needed. In parallel with the processing in the second step by the second spindle 11b, the first spindle performs the processing in the first step shown in FIG. 16 (a) on the next workpiece (FIG. 16 (d)). . The indexing of the second spindle 11b at the time of indexing is performed with reference to the origin slit 26 of the second spindle encoder 27b.
Since the phase signal of 27b is corrected by the second spindle angle command correction circuit 49 and given to the NC device 50, it is assumed that a phase shift remains when the workpiece 81 is transferred from the first spindle 11a to the second spindle 11b. In this case, the phase shift is corrected, and all indexing operations are performed substantially at an accurate position based on the origin of the first main spindle encoder 27a.

When the processing in the second step on the second spindle side is completed, the workpiece 81 is discharged out of the machine by an unloader (not shown), the record in the memory device 48 is cleared, and the work piece 81 is set in the second spindle angle correction command circuit 49. The corrected value is also reset. Then, the second spindle 11b waits until the machining of the first spindle is completed. In some cases, the first spindle 11a may be on standby. The machining program for the bar is created in consideration of minimizing the waiting time at this time.

Although the above is about the bar material processing, the processing of the flange material is also performed by a method according to the above-described bar material, and it is obvious from the above description and the conventionally known flange material processing method. The details are omitted. In the case of a flange material, the work 80 is a single piece from the beginning, and is directly supplied to the chuck 19a of the first main spindle by an autoloader for the flange material. It is natural that the parting-off process is not required when the second main spindle 11b is transferred from the first main spindle to the second main spindle 11b. The delivery is completed just by doing.

<< Effects of the Invention >> As described above, according to the present invention, turning and indexing are performed under the control of the same spindle motor.
In a spindle-facing type CNC lathe, the loss time at the time of transferring the work from the first spindle to the second spindle can be greatly reduced, and the occurrence of work defects and torsional deformation due to slippage of the chuck can be prevented. The phases of the first spindle and the second spindle at the time of indexing can be accurately matched.

[Brief description of the drawings]

The figure shows a two-spindle opposed type CNC lathe according to the present invention.
FIG. 2 is a view showing the arrangement of devices on a base, FIG. 2 is a schematic sectional view of the apparatus, FIG. 3 is a perspective view showing a chip discharge system, FIG. 4 is a plan view of a spindle head portion, and FIG. FIG. 6 is a plan view showing another example of the spindle head portion, FIG. 6 is a diagram showing a slit of the spindle encoder, FIG. 7 is a block diagram showing speed control means of the spindle, FIG. 9 is a block diagram showing a control system of the brake device, FIG. 10 is a block diagram showing a synchronous control means of the spindle motor, FIG. 11 is a diagram showing a circuit example of the slow discrimination circuit in FIG. 10, and FIG. FIG. 10 is a diagram showing a circuit example of the phase discriminating circuit in FIG. 10, FIG. 13 is a diagram for explaining a phase difference of the spindle encoder, FIG. 14 is a diagram illustrating a pulse cut out by the slow discriminating circuit, and FIG. FIG. 16 is a block diagram illustrating the detection and storage means of FIG. It is a diagram. In the figure, 1: base, 2: spindle head 3: machining unit, 11: spindle 16: positioning stopper, 19: chuck 21: spindle motor, 22: brake device 24: unit angle slit, 25: reference angle slit 26: origin Slit, 27: Spindle encoder 53: Synchronous control means, 80: Bar 81: Workpiece, 83: Tool 84: Drill, 85: Milling cutter 86: Parting tool

Claims (3)

(57) [Claims] A first spindle head (2a) substantially integrally fixed to a common base (1), and a second spindle head (2a) which is movable on the same axis as the first spindle head and is movable and positioned in the Z-axis direction. A spindle head (2b), a turret-type first processing unit (3a) capable of moving and positioning in the X-axis and Z-axis directions corresponding to the first spindle head, and an X corresponding to the second spindle head. A turret-type second processing unit (3b) that can move and position only in the axial direction, and first and second main spindles (11a) supported by the first and second main spindle heads (2a) and (2b), respectively. , (11b) and the first and second spindles (11
a) A method of machining a workpiece on a two-spindle opposed type CNC lathe including first and second spindle encoders (27a) and (27b) for detecting a rotation angle phase and an origin phase of (11b), respectively. (27a) and (27b) are the spindles (11a) and (1
1b) An origin pulse for detecting the phase origin, a reference angle pulse having a predetermined angle interval and a unit angle pulse having an angle interval finer than the reference angle pulse are output, and the workpiece (80) to be processed is moved to the first spindle ( 11a), a first step of performing a first-stage processing on the workpiece by the cooperative operation of the first spindle and the first processing unit (3a) while holding the first spindle while rotating the second spindle (11b). The main spindle (11a) is advanced toward the main spindle (11a), and the first main spindle (11a) and the second main spindle (11b) are counted by reference pulse signals extracted by the origin pulse signals of the main spindle encoders (27a) and (27b). Are compared, phase adjustment is performed, and the count values of the unit angle pulses of the first and second spindle encoders (27a) and (27b) at a predetermined time are compared to synchronize the speeds, and then the second spindle (11b) Work (8
0) gripping the tip, storing the phase error detected by comparing the count value of the unit angle pulse cut out with the reference angle pulse signal at the time of gripping, and storing the phase error from the workpiece (80) to the workpiece (81) is separated or the grip of the first spindle (11a) is released, and the workpiece (81) or the work (80) is transferred to the second spindle (11b), and then the second spindle (11b) is connected to the first spindle (11a). A third step of separating from the NC apparatus (50) to the second spindle (11b) with the stored phase error to control the phase of the second spindle while controlling the phase of the second spindle. Main spindle (11b) and second machining unit (3
b) performing a second stage processing on the work piece (81) to the work (80) and then discharging the workpiece in a fourth step, and performing the first step in the first step. A method of machining a workpiece in a two-spindle opposed CNC lathe, which is performed in parallel with the fourth step for a workpiece or a workpiece. 2. A first spindle head (2a) substantially integrally fixed to a common base (1), and a second spindle capable of moving and positioning in the Z-axis direction on the same axis as the first spindle head. Head (2b), X and Z corresponding to the first spindle head
A turret-type first processing unit (3a) capable of moving and positioning in the axial direction, a turret-type second processing unit (3b) capable of moving and positioning only in the X-axis direction corresponding to the second spindle head, The first and second spindle heads (2
a) and (2b) the first and second spindles (1
1a), (11b), first and second spindle encoders (27a), (27b) for detecting the rotation angle phase and the origin phase of the first and second spindles (11a), (11b), respectively, and the NC device ( 50) first and second servo drive units (52a) and (52b) for controlling the drive motors (21a) and (21b) of the first and second spindles based on the speed command issued from the first and second spindle motors; The first and second servo drive units (52a), (52a) are based on the signal difference between the second spindle encoders (27a) and (27b).
In a two-spindle opposed CNC lathe provided with a synchronous control means (53) for correcting the speed command given to b), an origin pulse for detecting the phase origin of the spindles (11a) and (11b) and a reference angle pulse for a predetermined angular interval And a spindle encoder (27a) or (27b) that outputs a unit angle pulse having a smaller angle interval than the reference angle pulse. The synchronization control means (53) includes a first spindle encoder (27).
a) detecting the phase difference between the first main shaft (11a) and the second main shaft (11b) during rotation control from the difference between the count value of the reference angle pulse of the second main shaft encoder (27b) and registering this phase difference in advance; The first and the second are set so as to match the required required transfer phase difference.
Phase synchronizing means (59) and (56) for giving a predetermined speed offset command to the servo drive units (52a) and (52b) at predetermined time intervals, and synchronous rotation of the first spindle (11a) and the second spindle (11b). Inside the first spindle encoder (27a) and the second spindle encoder (27a)
The first step is performed so that the difference between the count values of the unit angle pulse in b) becomes zero.
And synchronization command means (54) and (56) for giving a predetermined speed offset command to the second servo drive units (52a) and (52b) at predetermined time intervals, wherein synchronization based on the difference between the count values of the reference pulses is performed. A two-spindle opposed CNC lathe characterized by switching to control based on the difference between the counts of the unit angle pulses when satisfied. 3. The synchronizing control means (53) includes a phase synchronizing means (59), (56) and a synchronizing command means (5).
4), (56), the phase of the first spindle encoder (27a) and the second spindle encoder (27b) when the first spindle (11a) and the second spindle (11b) grip the same work (80). Detection means (43a) and (43b) for detecting errors, comparison means (44), (4
6) and the storage means (49), and the index based on the detection angle of the second spindle encoder (27b) based on the phase error stored in the storage means (49) at the time of indexing with the second spindle (11b). A second spindle indexing angle correcting means (61) for correcting the output angle command and resetting the phase error of the storage means when the machining by the second spindle (11b) is completed. A two-spindle opposed type CNC lathe according to claim 2.