JPH0675004U - Numerical control device with double check function of machine origin - Google Patents

Abstract

(57) [Abstract] [Purpose] When returning to the origin by the closed loop method, check that it is near the origin using another position detector, for example, the positioning control of the pulse coder with built-in motor, and double the origin return of the machine. We provide a numerical control device with a double check function for the machine origin. [Structure] The first and second parameters are set in advance during the return-to-origin adjustment, and the first closed loop method is used during the return-to-origin.
In addition to the position control by the position control means, the motor rotation signal pulse as the second position control means is fetched as a count value after the motor 1 rotation signal is output, and then the count value fetched by the counter in the comparison means is used. The difference from the first parameter is calculated, and it is compared whether or not the calculated difference value is smaller than the allowable error amount of the second parameter. On the other hand, when the difference value is larger than the allowable error amount, an alarm is generated as a mechanical origin deviation.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a numerical control device for a machine tool, and in particular, at the time of returning to the origin by a closed loop feedback system, it has a mechanical origin double check function to check that it is near the origin by another position detector, for example, a pulse coder with a built-in motor. Regarding numerical control equipment.

[0002]

[Prior art]

 The NC machine tool has a machine specific point, that is, a machine origin, for each coordinate axis (for example, a point farthest from the work). This machine origin is used to fix the tool position so that it can always be set at the same position when setting the coordinate system during machining. When machining is performed, the NC program is usually created so that it starts from the machine origin and returns to the machine origin after the machining is completed. Such mechanical origin positioning control includes an open loop method and a closed loop method. In other words, the open loop method leaves the position control to the pulse motor system that is faithful to the command pulse and does not provide a feedback loop.The closed loop method detects the movement amount of the feed axis with the position detector and obtains the position signal obtained. Is fed back to control the position. The position of the moving amount of the feed axis is detected by fixing the scale to the feed axis, providing a mark at the origin position of this scale, and detecting the coordinate value of the mark point of this scale with the position detector. There is. However, the scale of the closed loop system itself may shift due to the dynamic error of the feed axis or the error of the control system (elements of thermal displacement and other position displacement), etc. In the control, there was no measure to deal with the origin deviation of such origin return. For this reason, even if there is a displacement of the origin when returning to the origin, there is a problem that the product is processed as it is without knowing it and a defective product is produced.

[0003]

[Problems to be solved by the device]

 From the above, the purpose of this invention is to check that the position is near the origin by using the positioning control of the pulse coder with a built-in motor, which is another position detector, when returning to the origin by the closed loop method. It is to provide a numerical control device with a double check function for the machine origin.

[0004]

[Means for Solving the Problems]

 In order to solve the above-mentioned problems, the present invention is a first closed loop system in which a home position return position of a feed axis of a servo motor is detected by a position detector, and the obtained position signal is fed back to control the home position return position. Position control means, a rotation signal generator that generates a rotation position signal of the servo motor and a signal for each rotation, and a count value of the number of pulses that is a rotation position signal after the one rotation signal is output. And the counter value that is stored as the first parameter, the count value of the number of pulses at the time of home return adjustment of the machine is stored as the first parameter, and the allowable error amount as the home position of the count value at the time of home return is set as the second parameter. And a storage means for storing the difference between the count value fetched by the counter at the time of returning to the origin and the first parameter, and the calculated difference value is the allowable error of the second parameter. A second position control means including a comparison means for making the case smaller than the positive, and a mechanical origin for returning to the origin by superposing the first position control means and the second position control means on top of each other. This is a numerical control device with a machine origin double check function, which is characterized by checking the position.

[0005]

[Action]

 With the above configuration, the first and second parameters are set in advance during the home return adjustment, and after the position control by the closed loop first position control means during the home return, the comparison means is subsequently operated. The difference between the count value fetched by the counter and the first parameter is calculated, and whether the calculated difference value is smaller than the allowable error amount of the second parameter is compared. On the other hand, if the difference value is larger than the allowable error amount, an alarm is generated as a mechanical origin deviation.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a numerical control device with a machine origin double check function according to the present invention will be described below with reference to the drawings. FIG. 1 is a system block diagram of a numerical control device with a double check function of machine origin according to the present invention. Reference numeral 20 denotes a numerical controller with a machine origin double check function. The structure of the numerical controller 20 will be described below. 1 is a central processing unit (CPU), 2 is a ROM that stores a system program, 3 is an NC program memory that stores a machining program (NC program), 4 is a RAM that temporarily stores various parameters and data being processed, 5 Is a shaft control means of the feed shaft for controlling the servomotor M through the amplifier 6 by executing the NC program by several blocks under the control of the CPU 1, and 7 is a feedback scale connected to the axis control means 5. The first position control means of the closed loop system of the present invention fixes the feedback scale 7 to the feed shaft, provides a mark at the origin position of the feedback scale 7, and sets the coordinate value of the mark point of the scale. Is detected by a position detector, and the obtained position signal is fed back to control the home-return position.

Reference numeral 8 is an input / output means, 8a is a display device (DPL) for displaying input data and a machining program being executed, and 8b is an operation panel (keyboard) used for data input. Reference numeral 9 is a ring counter which outputs a signal for each rotation of the servomotor M and takes in the number of pulses which is a rotational position signal after that as a count value. The second position control means includes a rotation signal generator (motor rotation signal generator 24 in FIG. 2) that generates a rotation position signal of the servo motor M and a signal for each rotation, the ring counter 9, and the machine. A storage unit that stores the count value of the number of pulses during home return adjustment as a first parameter, and stores the allowable error amount as a second parameter as the home position of the count value during home return, and a home return operation. At this time, a difference between the count value fetched by the counter and the first parameter is obtained, and the comparing means 10 is positive when the obtained difference value is smaller than the allowable error amount of the second parameter. Be done.

FIG. 2 is a schematic explanatory diagram of a numerical controller with a mechanical origin double check function of the present invention. In the figure, 4 is a RAM, 20 is a numerical control device, and this numerical control device 20 has a first position control means and a second position control means. A function to check the machine origin position is provided. That is, in the first position control means, 21a is a ball screw nut, 21b is a ball screw directly connected to the servo motor M, 22 is a fixed part of the ball screw nut 21a, and a movable portion that moves in the axial direction by the rotation of the ball screw 21b. The feedback scale 7 is fixed to the movable portion 22. Reference numeral 23 is a position detector that is paired with the feedback scale 7 and performs closed-loop detection. Further, the numerical controller 20 and the position detector 23 are connected by a connection A through an AMP for position signal.

In the second position control means, 24 is a motor rotation signal generator (pulse coder built in the motor). Further, the numerical control device 20 and the motor rotation signal generator 24 are connected by a connection B through an AMP for position signal. Further, the numerical control device 20 and the servomotor M are also connected by a connection C via an AMP as a drive unit. The first position control means forms a closed loop between the feed shaft and the servomotor M via the connections A and C, and the second position control means from the servomotor M via the connection B to the numerical controller 20. Form a closed loop to. The RAM 4 is provided with a count value E and parameters F (first parameter), G (second parameter), H (valid / invalid switching signal for double check function).

FIG. 3 is an explanatory diagram of the motor rotation signal, and the pulse P is generated by the rotation of the motor. D indicates a motor 1 rotation signal, and a pulse D is generated for each rotation of the motor. The ring counter 9 of the numerical controller takes in the pulse P after the signal D for each rotation of the servomotor M is output as the count value E, and the maximum value of the count value E is the pulse for one rotation of the motor. Becomes a number. That is, it is reset by the pulse D and starts counting again. The parameter F (first parameter) is a value obtained by loading the value E of the ring counter 9 at the time of adjusting the mechanical origin into the RAM 4. The parameter G (second parameter) is an input of the set value of the allowable error amount of the origin position. The set value of the permissible error amount is determined in consideration of the thermal displacement of the ball screw 21b and other positional displacement factors. The parameter H (third parameter) is used to switch the devised function between valid and invalid. When the parameter H is valid, the comparison means 10 compares the value E of the ring counter 9 with the value of the parameter F at the time of returning to the origin, and if the difference is smaller than the value of the parameter G, it is determined to be positive, and if it is larger. Abnormal. If it is abnormal, it is displayed on the CRT screen 8a and an alarm of origin abnormality is generated.

Next, the processing flow of this invention will be described with reference to the flow charts of FIGS. 4 and 5. In the processing of this invention, the processing of setting the initial values of the parameters F, G, and H (see FIG. 4) is performed, and then the machine origin double check function processing (see FIG. 5) is performed. Prior to the initial setting process in FIG. 4, for example, the origin adjustment and the origin return of the servomotor M are performed (step 101 and step 102). Then, when the processing is started, the CPU 1 determines whether or not the origin check is correct whether the origin adjustment and the origin return are performed (step 103). If the result of the determination is negative, the origin adjustment processing from step 101 is performed.

If the determination in step 103 is positive, the CPU 1 stores the value E of the ring counter 9 at the origin return position as the parameter F of the RAM 4 (step 104). Next, when the setting value of the allowable error amount of the origin position is input by the keyboard 8b or the like, the CPU 1 stores the setting value of the allowable error amount as the parameter G of the RAM 4 (step 105). When the setting of the parameters F and G is completed, the CPU 1 switches the parameter H from "0 (invalid)" to "1 (valid)" (step 106), and the initial setting of the parameters F, G, H is completed. . When the parameter H 1 is “0”, it means that the parameters F, G and H are not set.

When the initial setting is completed, a normal start becomes possible. That is, in FIG. 5, when the normal origin return process is started (step 201), the CPU 1 judges whether the parameter H of the RAM 4 is "1 (valid)" (step 202). If it is "1", then the CPU 1 The value E of the ring counter 9 is read, the absolute value of the difference between the read value E and the value of the parameter F of the RAM 4 is calculated, and the difference value and the value of the parameter G (set value of the allowable error amount) are compared. Are compared with each other (step 203), and when the value is smaller than the value of the parameter G, the result is positive and the origin return is completed (step 204). On the other hand, if the difference value is larger than the value of the parameter G, it is determined that the origin is abnormal, and the CPU 1 displays it on the CRT screen 8a and issues an origin abnormality alarm. If the home return is completed, normal operation starts. On the other hand, if the alarm of origin abnormality is displayed on the CRT screen 8a, the operator repeats the processing from step 101 of the initial set in FIG.

[0014]

[Effect of device]

 As described above, according to the configuration of the device of the present invention, the first and second parameters are set in advance in the home position return adjustment, and the closed loop type first position control means is set in the home position return. In addition to the position control by the second position control means, the motor rotation signal pulse is fetched as the count value E after the motor 1 rotation signal D is output, and then the count value fetched by the counter in the comparison means and The difference from the first parameter is obtained, and it is compared whether or not the obtained difference value is smaller than the permissible error amount of the second parameter, and the two of the first and second position control means are overlapped to return to the origin. Since it is possible to check the machine origin position at the time of, it is possible to prevent origin deviation when returning to the origin of the machine. Therefore, we do not make defective products due to the origin deviation when returning to origin.

[Brief description of drawings]

FIG. 1 is a system block diagram of a numerical controller with a machine origin double check function of the present invention.

FIG. 2 is a schematic explanatory view of a numerical control device with a machine origin double check function of the present invention.

FIG. 3 is an explanatory diagram of a motor rotation feedback signal.

FIG. 4 is a flow chart of processing for setting initial values of parameters F, G, and H of the machine origin double check function of the present invention.

FIG. 5 is a flow chart of a machine origin double check function process of the present invention.

[Explanation of symbols]

 1 Central Processing Unit (CPU) 2 ROM 3 NC Program Memory 4 RAM 5 Axis Control Means 6 AMP 7 Feedback Scale 8 Input / Output Means 9 Ring Counter 10 Comparison Means

Claims (1)

[Scope of utility model registration request] 1. A first position control means of a closed loop system, which detects a home position of a feed axis of a servomotor by a position detector, and feeds back the obtained position signal to control the home position. A rotation signal generator that generates a rotation position signal of the motor and a signal for each rotation, a counter that outputs the number of pulses that is a rotation position signal after the one rotation signal is output, as a count value, and a home position return adjustment of the machine. The count value of the pulse number at time is stored as a first parameter,
A storage means for storing a permissible error amount of the count value at the time of returning to the origin as the origin position, and a difference between the count value fetched by the counter at the time of returning to the origin and the first parameter. , The obtained difference value is the second
The second position control means is composed of a comparison means for making a positive value when it is smaller than the permissible error amount of the parameter, and the origin is formed by superposing the first position control means and the second position control means on top of each other. A numerical control device with a double check function for the machine origin, which checks the machine origin position when returning.