JP2001252956A - Self-diagnosis device for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a self-diagnosis device for an injection molding machine which can detect the omen of generation of abnormality early to promote the change of conditions to reduce maintenance such as repair and a load. SOLUTION: An operation part 1 converts a detection signal from a detector to which a command signal and a setting signal which are given to control objects in the injection molding machine individually and detection signals from detectors are input and which corresponds to these corresponding to the input command signal and the setting signal into a fixed point by sampling. An initial state storing device 2 stores data converted into a fixed point which are obtained by the operation part in the initial period of operation. A present state storing device 3 stores data converted into a fixed point which are obtained by the operation part in ordinary operation. A comparison operation part 4 reads data converted into a fixed point concerning the same control object from the device 2 and the device 3 and outputs diagnosis results concerning the same control object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a self-diagnosis device for an injection molding machine.

[0002]

2. Description of the Related Art In recent years, demand for electric injection molding machines has increased. This uses an electric motor (servo motor) as the drive source for the injection device and mold clamping device, which makes it easier to control than hydraulic drive sources, eliminates the need for hydraulic oil piping, and leaks hydraulic oil. Work environment is not polluted.

By the way, various types of monitoring functions have been proposed for this type of electric injection molding machine. For example, the current value supplied to the injection servomotor is detected by a current sensor to monitor whether the drive current of the servomotor is within a predetermined range. The occurrence is notified (for example, Japanese Patent Publication No. 7-80230).

[0004]

However, the monitoring up to now is to detect that an abnormality has actually occurred, and it is not possible to know in advance the possibility of occurrence of an abnormality.

[0005] In addition, conventional monitoring takes a form in which monitoring is performed separately even when there are a plurality of monitoring targets, and monitoring is not performed in consideration of a mutual relationship between monitoring targets. For example, in the case where the injection pressure is to be monitored in the injection device, better results should be obtained by monitoring not only the injection pressure but also other monitoring targets. For example, the electric type has more mechanically movable parts than the hydraulic type, and mechanical parts (ball screws, belts, pulleys, bearings, etc.) may be damaged at the time of heavy load forming, lubrication failure, etc. is there.
If you try to monitor this only with the drive current of the servo motor, if an increase in the drive current is detected, it is determined whether the load has increased or the drive current has actually increased due to poor lubrication of the mechanical parts. Can not do.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a self-diagnosis device for an injection molding machine which can promptly detect a precursor of occurrence of an abnormality and promote maintenance such as repair and change of conditions to reduce a load. It is in.

[0007]

A self-diagnosis apparatus for an injection molding machine according to the present invention comprises: a command signal and a setting signal provided for individually controlling a plurality of control objects in the injection molding machine; Detection signals from a plurality of detectors installed for the control are input, and in accordance with the input command signal and the setting signal, the detection signals from the detector corresponding to these are patterned or An arithmetic unit for performing a fixed point process by sampling, an initial state storage device for storing data subjected to patterning or fixed point processing obtained by the arithmetic unit in an initial operation, and a normal operation after the initial operation. A current state storage device for storing patternized or fixed point processed data obtained by an arithmetic unit, the initial state storage device, By comparing these data the patterned or reads the fixed point processing data related to the same control object and a standing state storage device,
A comparison operation unit for outputting a diagnosis result regarding the same control target.

[0008] The patterning or fixed point processing in the arithmetic section is performed for each cycle of the molding operation.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, with reference to FIG. 2, a description will be given mainly of an injection device in an electric injection molding machine to which the present invention is applied. The electric injection molding machine includes an injection device driven by a servomotor. In this injection device, the rotational motion of the servomotor is converted into a linear motion by a ball screw and a nut to move the screw forward and backward.

In FIG. 2, the rotation of the injection servomotor 11 is transmitted to a ball screw 12. A nut 13 that moves forward and backward by the rotation of the ball screw 12 is fixed to a pressure plate 14. Pressure plate 14
Are movable along guide bars 15, 16 (usually four, but only two are shown here) fixed to a base frame (not shown). Pressure plate 1
The forward and backward movements of the bearing 4 and the load cell 1
8, transmitted to the screw 20 via the injection shaft 19. The screw 20 is disposed so as to be rotatable in the heating cylinder 21 and to be movable in the axial direction. The heating cylinder 21 corresponding to the rear part of the screw 20 is provided with a hopper 22 for supplying resin. The rotation of a rotation servomotor 24 for rotating the screw 20 is transmitted to the injection shaft 19 via a connecting member 23 such as a belt or a pulley. That is, the rotation of the injection shaft 19 by the rotation servomotor 24 causes the screw 20 to rotate.

In the plasticizing / metering step, the screw 20 retreats inside the heating cylinder 21 while rotating, so that the front of the screw 20, that is, the heating cylinder 2
The molten resin is stored in one nozzle 21-1 side. The screw 20 retreats because the amount of molten resin stored in front of the screw 20 gradually increases, and the pressure of the screw 20 increases.
This is because it acts on 0.

In the filling and injection steps, the screw 20 is advanced in the heating cylinder 21 by driving the injection servomotor 11, so that the molten resin stored in front of the screw 20 is filled in the mold. The molding is performed by applying pressure. At this time, the force pressing the molten resin is detected by the load cell 18 as the injection pressure. The detected injection pressure is amplified by the load cell amplifier 25 and input to the control device 26. The pressure plate 14 is provided with a position detector 27 for detecting the amount of movement of the screw 20. The detection signal of the position detector 27 is amplified by the position detector amplifier 28 and
Is input to

The control device 26 outputs a current (torque) command of the servomotor corresponding to each of a plurality of processes to the drivers 29 and 30 in accordance with a preset value through the man-machine controller 34 by the display / setting device 33. I do. The driver 29 controls the drive current of the injection servomotor 11 to control the output torque of the injection servomotor 11. The driver 30 controls the drive current of the rotation servomotor 24 to control the rotation speed of the rotation servomotor 24. The injection servomotor 11 and the rotation servomotor 24 are provided with encoders 31 and 32 for detecting the number of rotations, respectively. The rotation speeds detected by the encoders 31 and 32 are input to the control device 26, respectively. In particular, the rotation speed detected by the encoder 32 is used to know the rotation speed of the screw 20. Control device 2
6, current sensors 35 and 36 for detecting drive currents to the injection servomotor 11 and the rotation servomotor 24, respectively.
Is input.

On the other hand, around the heating cylinder 21, a plurality of heaters 4 for heating and melting the resin from the hopper 22 are provided.
The heaters 40 are controlled by a temperature controller 41. Temperature detection signals from a plurality of thermocouples 42 arranged adjacent to the heater 40 are input to the temperature control device 41. The temperature control device 41 outputs temperature detection signals from the plurality of thermocouples 42 to the control device 26 as thermocouple detection values, and controls the heater 40 based on the heater temperature setting signal indicating the heater temperature set value from the control device 26. Control.

Next, an embodiment of a self-diagnosis device according to the present invention applied to an electric injection molding machine as shown in FIG. 2 will be described with reference to FIG. In FIG. 1, a self-diagnosis device includes a command signal and a setting signal provided for individually controlling a plurality of control targets in an electric injection molding machine, and a plurality of detection signals provided for controlling the plurality of control targets. An operation unit 1 for receiving a detection signal from the detector and for performing a fixed-point process on the detection signal from the detector corresponding to the input command signal and the setting signal by sampling at a fixed period according to the input signal and the setting signal; An initial state storage device 2 for storing fixed-point processed data obtained by the arithmetic unit 1 in the initial stage, and for storing fixed-point processed data obtained by the arithmetic unit 1 in normal operation after the initial operation. From the current state storage device 3, the initial state storage device 2, and the current state storage device 3, the data subjected to the fixed point processing for the same control target is read out, and these data are compared. And a, and a comparison operation portion 4 for outputting a diagnostic result for the same control object of the. A switch 5 is provided on the output side of the operation unit 1. The operation unit 1 sets the changeover switch 5 to the initial state storage device 2 only at the beginning of operation, and thereafter sets the changeover switch 5 to the current state storage device 3 To the side. Further, the fixed point processing in the arithmetic unit 1 is performed for each cycle of the molding operation.

To make the description easier to understand,
As described with reference to FIG. 2, the injection speed command signal in the injection device as the command signal, the heater temperature setting signal as the setting signal are input to the calculation unit 1, and the detection signal is provided to the injection servomotor 11. It is assumed that the detected value of the injection encoder from the encoder 31, the detected value of the current sensor from the current sensor 35, the detected value of the injection pressure from the load cell 18, and the detected value of the thermocouple from the temperature control device 41 are input to the arithmetic unit 1. . The injection speed command signal is a signal given to the driver 29 for driving the injection servomotor 11. In particular, the command signal is input in one of a plurality of steps described above in one cycle of the molding operation.

Therefore, the arithmetic unit 1 responds to the input command signal by detecting the corresponding detector, here, the encoder 31 corresponding to the injection speed command signal, the current sensor 35, and the detection of the injection encoder from the load cell 18. A value, a current sensor detected value, and an injection pressure detected value are selected, and a fixed point process is performed on these detected values by sampling at a constant period. Also, for the thermocouple detection value, a timing that does not overlap with the above-described fixed point processing is selected within one cycle of the molding operation, and the fixed point processing is performed by sampling at a fixed period.
The data obtained by such a fixed point process is a digital value at fixed time intervals. The arithmetic unit 1 further obtains fixed-point processing data for a plurality of molding cycles at the beginning of the operation, but outputs only one cycle of the data to the initial state storage device 2 for storage. On the other hand, when the normal operation starts, the arithmetic unit 1 causes the current state storage device 3 to store the fixed point processing data for each molding cycle.

Here, for example, with respect to fixed point processing data relating to the detected value of the injection encoder, the arithmetic unit 1 stores this data in the same address area of the initial state storage device 2 and the current state storage device 3. The same applies to other fixed point processing data. The reason for this is to facilitate the operation when reading is performed for comparison in the comparison operation unit 4 described below.

The comparison operation unit 4 reads data relating to the detected value of the injection encoder and data relating to the detected value of the injection pressure from the initial state storage unit 2 and the current state storage unit 3, respectively, and stores the data relating to the two detected values of the injection encoder. At the same time, the data on the two injection pressure detection values is compared. As a result of the comparison, if there is no significant difference between the data on the two injection encoder detection values, but the data on the current injection pressure detection value is abnormally larger than the data on the injection pressure detection value in the initial state, the load Is estimated, that is, the lubrication state of the ball screw 12 is not good, and as a result of the self-diagnosis, a notification for prompting the supply of the lubricating oil to the ball screw 12 is performed.

The comparison operation unit 4 also reads data relating to the detected thermocouple values from the initial state storage unit 2 and the current state storage unit 3, respectively, and compares the data relating to the two detected thermocouple values. As a result of the comparison, if the data on the current thermocouple detection value is abnormally small compared to the data on the thermocouple detection value in the initial state, it is estimated that the heater 40 is disconnected, and the self-diagnosis Provides notification to prompt repair.

In the above example, the case where the arithmetic unit 1 performs the fixed point processing is described. However, the present invention is not limited to this. Patterning processing, that is, processing in which a detected value during a certain time is represented as a pattern is performed. May be performed. In this case, the comparison operation unit 4 compares the patterned data. In addition to the detectors shown in FIG. 2, detectors such as resin temperature, mold temperature, and power supply voltage may be added, or some of them may be omitted. Further, it goes without saying that the present invention can be applied to a mold clamping device other than the injection device. Further, the present invention is not limited to the electric type and can be applied to a hydraulic injection molding machine.

[0022]

According to the present invention, by providing a self-diagnosis function, a sign of occurrence of an abnormality is detected early, and a condition change or a lubrication system for reducing a load before a fatal damage is received. Maintenance such as repair of the vehicle. In addition, by replacing the parts which are likely to reach the end of their service life in advance in a planned manner, it is possible to avoid problems such as sudden machine stoppage.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of a self-diagnosis device according to the present invention.

FIG. 2 is a diagram mainly showing an injection apparatus in a configuration of an electric injection molding machine to which the present invention is applied.

[Explanation of symbols]

 12 Ball screw 13 Nut 14 Pressure plate 15 and 16 Guide bar 17 Bearing 18 Load cell 19 Injection shaft 20 Screw 21 Heating cylinder 23 Connecting member 27 Position detector 31, 32 Encoder 35, 36 Current sensor

Claims (2)

[Claims] 1. A command signal or a setting signal provided for individually controlling a plurality of control objects in an injection molding machine;
Detection signals from a plurality of detectors installed for controlling the plurality of control targets are input, and in response to the input command signal and the setting signal, detection from the corresponding detectors is performed. An operation unit for performing a fixed point process by patterning or sampling a signal; an initial state storage device for storing patternized or fixed point processed data obtained by the operation unit in an initial operation; and after the initial operation. A current state storage device for storing data that has been subjected to patterning or fixed point processing obtained by the arithmetic unit in normal operation, and the patterning relating to the same control target from the initial state storage device and the current state storage device. Alternatively, by reading out the fixed-point processed data and comparing these data, the same control target can be obtained. A comparison operation unit for outputting a diagnosis result of self-diagnosis device for an injection molding machine, comprising the. 2. The self-diagnosis device according to claim 1,
The self-diagnosis device for an injection molding machine, wherein the patterning or fixed point processing in the arithmetic unit is performed for each cycle of a molding operation.