JP2013244710A - Method for displaying load condition of electric injection molding machine and driving device of electric injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for displaying a load condition of an electric injection molding machine which protects a driving unit against an excess load and also can suppress a reduction in production size of an molded article and to provide a driving device of the electric injection molding machine.SOLUTION: A load condition of servomotors 15a to 15d which drive an injection molding machine 10 over a plurality of cycles is displayed on a display unit 40. A load factor of the servomotors 15a to 15d is determined whenever one cycle CT is carried out and the load condition based on a change in the load factor determined over the plurality of cycles is displayed on the display unit 40.

Description

  The present invention relates to a load status display method for an electric injection molding machine that displays a load status of a drive unit that drives the electric injection molding machine on a display unit, and a drive device for the electric injection molding machine.

  The capacity of the servo motor (drive unit) that drives the electric injection molding machine is desired to be reduced in order to reduce costs. On the other hand, a servo motor with a small capacity easily overheats due to an overload and takes time to recover. This adversely affects the yield of the injection molding machine. Therefore, in order to avoid overheating of the servo motor, the techniques of cited documents 1 and 2 have been proposed.

  The technique disclosed in the cited document 1 measures the current value flowing through the servo motor and the time during which the current flows during the trial operation, and when the measurement result is in a predetermined overload anxiety region, It is intended to prompt the review of servo motor operation setting conditions. Further, the technique disclosed in the cited document 2 obtains an average load level for each molding cycle in the drive unit, and cycle extension time or cycle shortening for lowering or raising the average load level to a preset reference load level. It indicates time directly or indirectly.

JP-A-11-235743 Japanese Patent No. 3801557

  However, the technique of the cited document 1 only warns that the servo motor is overloaded. Further, since the technique of the cited document 2 extends the cycle time required for molding one molded article by the load factor, the number of molded articles produced may be extremely worse than planned.

  The present invention has been made in view of the above circumstances, and a load status display method for an electric injection molding machine and an electric injection molding machine capable of protecting a drive unit from an overload and suppressing a decrease in the number of molded products produced. An object of the present invention is to provide a driving apparatus.

  The load status display method for an electric injection molding machine according to the present invention is a load status display method for an electric injection molding machine that displays the load status of a drive unit that drives the electric injection molding machine over a plurality of cycles on a display unit. The load factor of the drive unit is obtained every time one cycle is executed, and the load state based on the change of the load factor obtained over a plurality of cycles is displayed on the display unit. To do.

  An electric injection molding machine driving device according to the present invention includes a driving unit that drives the electric injection molding machine over a plurality of cycles, a detection unit that detects a temperature or a current value of the driving unit, and the detection unit. And a display unit for displaying the load status of the drive unit calculated by the control unit. Each time a cycle is executed, the load factor of the drive unit is obtained, and a load status based on a change in the load factor obtained over a plurality of cycles is displayed on the display unit.

  According to the present invention, since the load status based on the change in the load factor obtained over a plurality of cycles can be displayed on the display unit, the load status can be predicted, and the drive unit is protected from overload. In addition, a decrease in the number of molded products produced can be suppressed.

It is a block diagram which shows the injection molding apparatus which concerns on 1st Embodiment. It is a timing chart which shows operation of servomotors 15a-15d concerning a 1st embodiment. It is a figure which shows the image displayed on the display part 40 which concerns on 1st Embodiment. It is a flowchart which shows the calculation process of the number of continuous possible shots. It is a figure which shows cycle time CT (time required for 1 cycle) and the temperature change of the servomotor 15a. It is a figure which shows the relationship between thermal time constant (tau) and final temperature Tmax. It is a figure which shows the display method of the continuous shot number display area 43. FIG. It is a figure which shows the overload trend display area 42 which concerns on 2nd Embodiment.

  Hereinafter, a load state display method for an electric injection molding machine and a drive device for the electric injection molding machine according to an embodiment will be described in detail with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 is a block diagram showing an injection molding apparatus according to the first embodiment. As shown in FIG. 1, the injection molding device (drive device) includes an injection molding machine 10, servo amplifiers 21 a to 21 d, a controller 30, and a display unit 40. The injection molding machine 10 is an electric injection molding machine and has servo motors 15a, 15b, 15c and 15d. The mold 11 is filled with resin at a predetermined pressure by the driving force of the servo motors 15a to 15d, and the inside of the mold. The resin is cured with a to produce a molded product. The servo amplifiers 21a to 21d drive the servo motors 15a to 15d based on commands from the controller 30 and feedback signals from the servo motors 15a to 15b. The controller 30 is configured by a computer, monitors the state of the injection molding machine 10, and controls the servo amplifiers 21a to 21d. The display unit 40 is configured by a liquid crystal display or the like, and displays various information such as the number of remaining shots under the control of the controller 30.

  As shown in FIG. 1, the injection molding machine 10 includes servo motors 15 a to 15 d and sensors 16 a to 16 d. The servo motor 15a is for injection servo and moves the screw 13 provided in the nozzle 12 forward and backward. The servo motor 15b is for measuring servo, and rotates the screw 13 to measure the amount of resin. The servo motor 15c is for projecting, and the projecting rod 14 is moved to eject the molded product from the mold 11. The servo motor 15d is for mold clamping servo and performs mold clamping of the mold 11. The sensors 16a to 16d detect the heat generation temperatures of the servo motors 15a to 15d, respectively, and transmit information about the detected temperatures to the controller 30.

  Each of the servo amplifiers 21a to 21d drives the servo motors 15a to 15d with, for example, a three-phase PWM signal based on a comparison value between a command value from the controller 30 and an encoder signal fed back from the servo motors 15a to 15d. That is, the servo amplifiers 21 a to 21 d and the servo motors 15 a to 15 d function as drive units that drive the injection molding machine 10. The servo amplifiers 21 a to 21 d generate position feedback signals based on the encoder signals fed back from the servomotors 15 a to 15 d and transmit the position feedback signals to the controller 30. The encoder signal includes information such as the angular velocity of the servo motors 15a to 15d.

  As shown in FIG. 1, the controller 30 includes a storage unit 31, a CPU (control unit) 32, input units 33a and 33b, and output units 34a and 34b. The storage unit 31 includes an HDD (Hard Disk Drive), an SSD (Solid State Drive), and the like, and stores various programs and data. The CPU 32 executes various operations based on the program read from the storage unit 31. The CPU 32 receives information regarding the temperature of the servo motors 15a to 15d from the sensors 16a to 16d via the input unit 33a, and inputs position feedback signals from the servo amplifiers 21a to 21d via the input unit 33b. The CPU 32 controls the servo amplifiers 21a to 21d via the output unit 34a and calculates the number of remaining shots based on the temperature or current value of the servo motors 15a to 15d. Further, the CPU 32 displays various information such as the number of remaining shots on the display unit 40 via the output unit 34b.

  Next, the operation timing of the servo motors 15a to 15d will be described with reference to FIG. FIG. 2 shows the operation of one cycle for forming one molded article. As shown in FIG. 2, in one cycle, a mold clamping process, an injection process (including forward and backward movement of the nozzle), a metering process, a mold opening process, a protruding process, and a standby process are executed in order.

  As shown in FIG. 2, the servo motor 15a is driven in the injection process and the metering process. The servo motor 15b is driven in the weighing process. The servo motor 15c is driven in the mold clamping process and the mold opening process. The servo motor 15d is driven in the protruding process.

  Next, an image displayed on the display unit 40 will be described with reference to FIG. As shown in FIG. 3, a load factor display area 41, an overload trend display area 42, a continuous possible shot number display area 43, and an overload protection selection area 44 are displayed on the display unit 40. In FIG. 3, the display unit 40 shows an image in a state where the servo motors 15a to 15d are driven over a plurality of cycles.

  In the load factor display area 41, the load factors of the servo motors 15a to 15d obtained most recently are displayed. Here, in the load factor, the limit temperature (overheat temperature) of the servo motors 15a to 15d is set to 100%. The load factor is obtained based on the temperatures of the servo motors 15a to 15d every time one cycle is executed. For example, in the example shown in FIG. 3, the load factors of the servo motors 15a to 15d are displayed as “89.0%”, “76.0%”, “20.0%”, and “31.0%”, respectively. Is done.

  In the overload trend display area 42, changes in the load factors of the servomotors 15a to 15d obtained over a plurality of cycles are displayed. As shown in FIG. 3, the horizontal axis represents the number of cycles, and the vertical axis represents the load factors of the servo motors 15a to 15d. From this overload trend display area 42, the user can know the tendency of the load factors of the servo motors 15a to 15d to change. Therefore, the user can limit the torque of the servo motors 15a to 15d by changing the molding conditions if there is a possibility that the servo motors 15a to 15d may be seized (overheat).

  In the continuous possible shot number display area 43, the number of continuous possible shots is displayed based on the change in the load factor of the servomotors 15a to 15d. Here, the number of continuous shots is the maximum number of times that the servo motor can be driven without being burned over a plurality of consecutive cycles, and is the number of cycles in which the load factor of the servo motor reaches a limit value. The number of continuous shots is estimated based on the temperature change (change in load factor) of the servomotors 15a to 15d. For example, as shown in FIG. 3, “21”, “75”, “∞”, and “992” are displayed for the servo motors 15a to 15d, respectively. This continuous shot number display area 43 allows the user to compare the number of continuous shots with the number of production plans. If the number of continuous shots is larger than the number of production plans, it is not necessary to change the drive conditions of the servo motors 15a to 15d. On the other hand, if the number of continuous shots is smaller than the number of production plans, the drive conditions of the servo motors 15a to 15d may be changed (torque limitation or the like).

  Next, with reference to FIG. 4 to FIG. 6, processing for calculating the number of continuous shots of the servo motor 15 a will be described. FIG. 4 is a flowchart showing a process for calculating the number of consecutive shots. FIG. 5 is a diagram showing the cycle time CT (time required for one cycle) and the temperature change of the servo motor 15a. FIG. 6 is a diagram showing the relationship between the thermal time constant τ and the final temperature Tmax. The calculation process shown in FIG. 4 is executed by the CPU 32. Further, it is assumed that the thermal time constant τ of the servo motor 15a is calculated in advance by measuring the temperature of the servo motor 15a during load operation. In addition, since the calculation process of the number of continuous shots of the servo motors 15b to 15d is the same as that of the servo motor 15a, the description thereof is omitted.

  As shown in FIG. 4, first, before driving the servomotor 15a, the temperature T (n) (where n = 0) of the servomotor 15a is measured (S100, S101). Next, after one cycle is executed, n is incremented (S110), and the cycle time CT and the temperature T (n) of the servo motor 15a are measured (S102). Here, as shown in FIGS. 5 and 6, the temperature increase rate ΔT (n−1) by one cycle can be calculated from the temperatures T (n−1) and T (n) measured in the above steps. Become. Therefore, as shown in FIG. 4, the temperature increase rate ΔT (n−1) is calculated after step S102 (S103). The temperature increase rate ΔT (n−1) is calculated based on “ΔT (n−1) = (T (n) −T (n−1)) / CT”.

  After step S103, the final temperature Tmax is calculated (S104). The final temperature Tmax is calculated based on “Tmax = τ · ΔT (n−1) + T (n−1)”. Subsequently, it is determined whether or not the final temperature Tmax is higher than the warning temperature Ta (Tmax> Ta) (S105). Here, as shown in FIG. 6, the thermal time constant τ represents the time required to change from the temperature T (n−1) to about 63% of the final temperature Tmax. This thermal time constant τ is measured in advance for each of the servo motors 15a to 15d. The temperature of the servo motor 15a increases so that the final temperature Tmax is an asymptotic line. The example shown in FIG. 6 shows a case where the final temperature Tmax is higher than the warning temperature Ta. The warning temperature Ta is a temperature at which the load factor of the servomotors 15a to 15d reaches a limit value unique to each motor.

  In step S105, if the final temperature Tmax is equal to or lower than the warning temperature Ta (Tmax ≦ Ta) (N in S105), “∞” is displayed in the continuous possible shot number display area 43 (S106). And the process of step S102-S105 is performed again.

  On the other hand, when the final temperature Tmax is higher than the warning temperature Ta in step S105 (Tmax> Ta) (Y in S105), the overload abnormality expected time OVt is calculated (S107). The overload abnormality expected time OVt is “Ta−T (n) = (Tmax−T (n)) · (1−exp (−OVt / τ))”, that is, “OVt = −τ · log (1− ( Ta−T (n)) / (Tmax−T (n))) ”.

  Next, the continuous possible shot number Sr is calculated (step S108). Here, the continuous possible shot number Sr is calculated based on “Sr = OVt / CT”, and the fraction is rounded down. After step S108, the continuous possible shot number Sr (for example, “21”) is displayed in the continuous possible shot number display area 43 (S109). And the process of step S110, S102-S105 is performed again.

  Next, a display method of the continuous possible shot number display area 43 will be described with reference to FIG. In the example shown in FIG. 7, only the number of continuous shots of the servo motor 15a is less than 100, and the number of continuous shots of the other servo motors 15b to 15d is 100 or more. In such a case, the color scheme of the display area of the servo motor 15a whose number of continuous shots is less than 100 is changed to the color scheme of the display areas of the other servo motors 15b to 15d. Thereby, a user can be alerted regarding the servomotor 15a.

[Second Embodiment]
Next, an injection molding apparatus according to the second embodiment will be described. The injection molding apparatus according to the second embodiment has the same configuration as that of the first embodiment. However, in the second embodiment, as shown in FIG. 8, the image displayed in the overload trend display area 42 is different from that in the first embodiment. Although FIG. 8 shows an image related to the servomotor 15a, images similar to the servomotor 15a are also displayed for the servomotors 15b to 15d.

  In the second embodiment, the estimated load curve L is displayed in the overload trend display area 42. The estimated load curve L shows the change with the number of cycles of the estimated load factor of the servomotor 15a. The estimated load curve L is calculated based on a function T (t) representing the estimated temperature change (change in load factor) of the servo motor 15a. The function T (t) is obtained by “T (t) = Tmax · (1−exp (−t / τ)”, where “t” is the elapsed time and τ is the time when the servo motor 15a is hot. The constant, Tmax, is the final temperature Tmax obtained in step S104 of the first embodiment.

  From the estimated load curve L, the user can more easily know the tendency of the load factor of the servo motor 15a to change than in the first embodiment.

  Although the embodiments of the invention have been described above, the present invention is not limited to these embodiments, and various modifications and additions can be made without departing from the spirit of the invention. For example, in the first embodiment, the load factors of the servo motors 15a to 15d are obtained from the temperatures of the servo motors 15a to 15d measured by the sensors 16a to 16d. However, in the present invention, the load factor may be obtained based on the integrated value of the current values supplied to the servomotors 15a to 15d. Further, the encoder signals of the servo motors 15a to 15d may be transmitted directly to the controller 30 without passing through the servo amplifiers 21a to 21d.

  DESCRIPTION OF SYMBOLS 10 ... Injection molding machine, 11 ... Mold, 12 ... Nozzle, 13 ... Screw, 14 ... Protruding rod, 15a-15d ... Servo motor, 16a-16d ... Sensor, 21a-21d ... Servo amplifier, 30 ... Controller, 31 ... Storage unit 32 ... CPU 33a, 33b ... input unit 34a, 34b ... output unit 40 ... display unit.

Claims (5)

A load status display method for an electric injection molding machine that displays on a display unit a load status of a drive unit that drives the electric injection molding machine over a plurality of cycles,
Each time one cycle is executed, the load factor of the driving unit is obtained,
A load status display method for an electric injection molding machine, characterized in that a load status based on a change in load factor obtained over a plurality of cycles is displayed on the display section. Based on the change in the load factor, estimate the number of cycles in which the load factor reaches a limit value,
The load status display method for an electric injection molding machine according to claim 1, wherein the estimated number of cycles is displayed on the display unit. Based on the change in the load factor, estimate the change in the load factor with the number of cycles,
The load state display method for an electric injection molding machine according to claim 1 or 2, wherein the change in the estimated load factor is displayed on the display unit. The drive unit includes a servo motor and a servo amplifier that supplies current to the servo motor.
The load status display method for an electric injection molding machine according to claim 1, wherein the load factor is obtained based on a temperature of the servo motor. A drive unit for driving the electric injection molding machine over a plurality of cycles;
A detecting unit for detecting a temperature or a current value of the driving unit;
A control unit that inputs a detection value from the detection unit and calculates a load status of the driving unit;
A display unit for displaying the load status of the drive unit calculated by the control unit,
The control unit obtains a load factor of the driving unit every time one cycle is executed, and causes the display unit to display a load situation based on a change in the load factor obtained over a plurality of cycles. A drive device for an electric injection molding machine.

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