JP2001341182A - Foreign matter detection method for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance production efficiency and productivity by eliminating trouble such that a molding cycle time becomes long and to detect foreign matter certainly and stably. SOLUTION: A monitor section Zs for releasing the synchronism between drive mechanisms 2p and 2q during a period Ta when the drive pressures of the drive mechanisms 2p and 2q become low and for lowering the torques of the drive mechanisms 2p and 2q to predetermined magnitude is set and the inclination of a movable part in the monitor section Zs is monitored and, when the inclination becomes preset magnitude, foreign matter detection processing accompanied by the detection of foreign matter D is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter detection method of an injection molding machine for detecting a foreign matter caught between a fixed part when a movable part is moved by a pair of driving mechanisms.

[0002]

2. Description of the Related Art Conventionally, a movable platen is moved forward and backward by a pair of drive mechanisms using a servomotor and a ball screw mechanism.
A mold clamping device which opens and closes the mold and clamps the mold based on this is known from Japanese Patent Application Laid-Open No. 5-269748.

By the way, in such a mold clamping device, if a molded product protruding from the opened mold is caught in the middle of the mold without dropping normally, the molded product is inserted into the mold in the next molding cycle. It becomes a foreign substance that gets caught, and hinders normal opening and closing of the mold. For this reason, conventionally, if the mold does not close normally even after a certain period of time has passed when the mold is closed, it is determined that foreign matter has been caught in the mold, and the controller determines that the mold clamping device (servo motor) Processing to stop the operation or output an alarm by an alarm was performed.

[0004]

However, such a conventional foreign matter detection method has the following problems.

First, it is necessary to secure a certain amount of time to determine whether or not the mold is closed when a predetermined time has elapsed, and it is necessary to secure a certain amount of time. This leads to a decrease in sex.

Second, since the detection is performed by monitoring the absolute position, for example, when the origin shifts due to a temperature drift or the like, there is a possibility of erroneous detection, and reliable and stable detection cannot be performed. .

The present invention has been made to solve the problems existing in the prior art, and eliminates the problem that the molding cycle time is lengthened, thereby improving production efficiency and productivity, and reliably and stably detecting foreign matter. It is an object of the present invention to provide a foreign matter detection method for an injection molding machine that can be performed in a timely manner.

[0008]

SUMMARY OF THE INVENTION A foreign object detection method for an injection molding machine M according to the present invention comprises a pair of driving mechanisms 2.
When detecting the foreign matter D caught between the fixed part 4 when the movable part 3 is moved by p and 2q, the driving mechanism 2
During a period Ta during which the driving pressures of p and 2q are low, the synchronization between the driving mechanisms 2p and 2q is released, and the driving mechanisms 2p and 2q are released.
monitoring section Zs for reducing the torque of q to a predetermined magnitude
Is set, and the inclination of the movable section 3 in the monitoring section Zs is monitored, and when the inclination becomes a predetermined size, a foreign substance detection process accompanying the detection of the foreign substance D is performed. I do.

In this case, according to a preferred embodiment, the driving mechanisms 2p and 2q include the servo motors 5p and 5q and the ball screw mechanisms 6p and 6q for converting the rotational motion of the servo motors 5p and 5q into a linear motion. Can be configured. Also,
The inclination of the movable section 3 can be detected by a deviation of output values obtained from the rotary encoders 7p, 7q provided in the servo motors 5p, 5q. Further, a movable plate 8m that supports a movable mold Cm provided in the mold clamping device Mc can be applied to the movable portion 3, and a period Ta during which the driving pressure is low is a period during which the high-speed mold closing is shifted to the low-pressure mold clamping. Can be applied.

[0010]

Next, preferred embodiments according to the present invention will be described in detail with reference to the drawings.

First, a schematic configuration of an injection molding machine M capable of performing the foreign matter detection method according to the present embodiment will be described with reference to FIGS.
This will be described with reference to FIG.

An injection molding machine M shown in FIG.
And an injection device Mi indicated by a virtual line. The mold clamping device Mc includes a fixed plate 8c and a drive plate 31 which are spaced apart, and the fixed plate 8c and the drive plate 31 are fixed on a machine base (not shown). Further, a movable plate 8m which can be displaced is arranged between the fixed plate 8c and the driving plate 31. The movable plate 8m has a movable die Cm mounted thereon, and the fixed plate 8c has a fixed die Cc mounted thereon. The movable mold Cm and the fixed mold Cc constitute a mold C.
Note that the fixed platen 8c forms the fixed portion 4, and the movable platen 8m forms the movable portion 3.

On the other hand, a pair of drive mechanisms, ie, a first drive mechanism 2p and a second drive mechanism 2 are provided between the drive board 31 and the movable board 8m.
q is arranged. In this case, it is a more preferable form to arrange the driving mechanisms 2p and 2q up and down in order to carry out the foreign matter detection method according to the present embodiment. First drive mechanism 2p
Has a servo motor 5p attached to the drive board 31 and a ball screw mechanism 6p for converting the rotational motion of the servo motor 5p into a linear motion. A nut portion 6pn of the ball screw mechanism 6p is provided on the rear surface of the movable board 8m. The rear end of the ball screw portion 6ps that is attached to the provided cylindrical nut support portion 32p and that is screwed to the nut portion 6pn is connected to the rotor shaft 5ps of the servomotor 5p. The second drive mechanism 2q includes a servo motor 5q attached to the drive board 31 and a ball screw mechanism 6q that converts the rotational motion of the servo motor 5q into a linear motion. The nut 6qn of the ball screw mechanism 6q Attached to the cylindrical nut support portion 32q provided on the rear surface of the movable plate 8m, the rear end of the ball screw portion 6qs screwed to the nut portion 6qn is
q to the rotor shaft 5qs. The first drive mechanism 2p and the second drive mechanism 2q are arranged symmetrically in the parting line direction with respect to the center of the mold C.

Reference numeral 33 denotes a controller having a computer function for executing various control processing, arithmetic processing, storage processing, and the like. Each servo motor 5p, 5q and each rotary encoder 7 provided for the servo motors 5p, 5q.
p and 7q are connected to the controller 33.

FIG. 3 shows a specific configuration of the controller 33,
In particular, a system for implementing the foreign matter detection method according to the present embodiment is extracted and shown. In FIG. 3, the same parts as those in FIG. 2 are denoted by the same reference numerals, and the configuration is clarified. The signal flow of each part is as follows. In the figure, reference numeral 10 denotes a central command unit, from which a first deviation calculating unit 11p
And a speed command value is given to the second deviation calculating unit 11q, and a reference setting value is given to the comparing unit 12,
A switching command signal is given to the two-axis synchronization control unit 15,
A current limiting signal is provided to the first current limiting unit 13p and the second current limiting unit 13q. Also, the first deviation calculation unit 1
Output values (speed detection values) obtained from the rotary encoders 7p and 7q are given to the 1p and second deviation calculation units 11q, and the respective deviation outputs of the first deviation calculation unit 11p and the second deviation calculation unit 11q are: These are provided to the input unit of the deviation calculation unit 14 for detecting foreign matter and the input unit of the two-axis synchronization control unit 15, respectively. On the other hand, the deviation E output from the deviation calculating unit 14 is applied to the input unit of the comparison unit 12, and the comparison output signal of the comparison unit 12 is applied to the central command unit 10.

One drive control signal output from the two-axis synchronization control unit 15 is applied to the servo motor 5p via the first speed control unit 16p, the first current limit unit 13p, and the first current control unit 17p. In addition, the other drive control signal output from the two-axis synchronization control unit 15
q, the second current limiting unit 13q, and the second current control unit 17q are provided to the servo motor 5q.

Next, the mold clamping operation of the mold clamping device Mc including the foreign matter detection method according to the present embodiment will be described with reference to FIGS. 2 to 5 and the flowchart shown in FIG.

First, the central command unit 10 includes the driving mechanism 2
A period during which the driving pressures of p and 2q are low, specifically, a period (region) in which the high-speed mold closing shown in FIG. 5 is shifted to the low-pressure mold clamping.
At Ta, the synchronization of each drive mechanism 2p, 2q is released,
In addition, a monitoring section Zs in which the torque of each drive mechanism 2p, 2q is reduced to a predetermined value is set. That is, a part of the period Ta is changed to satisfy the condition of the monitoring section Zs.

On the other hand, the mold clamping operation and the foreign matter detection processing are performed as follows. Now, it is assumed that the movable plate 8m of the mold clamping device Mc is at the mold open position shown in FIG. From this state, high-speed mold closing is first performed (step S1). In the high-speed mold closing, a speed command value set to a high speed from the central command unit 10 is applied to the first deviation calculation unit 11p and the second deviation calculation unit 11q, while the output values of the rotary encoders 7p and 7q (speed detection). Values) are respectively given to the first deviation calculation unit 11p and the second deviation calculation unit 11q, and the respective deviation outputs output from the first deviation calculation unit 11p and the second deviation calculation unit 11q are output from the two-axis synchronization control unit. 15 input units.

The two-axis synchronization control unit 15 controls and synchronizes the timing of each deviation output on the first deviation calculation unit 11p side and the second deviation calculation unit 11q side. Also, the first deviation calculation unit 1
The deviation output on the 1p side becomes a drive control signal for one of the servomotors 5p, and is output from the speed control unit 16p and the current limiting unit 1p.
The signal is applied to the servo motor 5p through signal processing by the 3p and the current control unit 17p, and the second deviation calculation unit 11
The q-side deviation output becomes a drive control signal for the other servo motor 5q, and is output from the speed control unit 16q and the current limiting unit 13q.
The signal is applied to the servomotor 5q through signal processing by the q and current control unit 17q. That is, normal feedback control for the mold closing speed V is performed.

As a result, the movable mold Cm moves forward at a high speed from the mold opening position to the mold closing direction. When the movable mold Cm reaches the deceleration start position Xa shown in FIG.
A deceleration process is performed based on the speed command value output from 0 (steps S2 and S3). Further, when the movable mold Cm reaches the low pressure start position Xb shown in FIG. 5, low pressure mold clamping is performed (steps S4 and S5). When the movable mold Cm reaches the low-pressure end position Xc at which the low-pressure mold clamping ends, high-pressure mold clamping by high-pressure control is performed (steps S6 and S7). The above is the mold clamping operation performed normally. In FIG.
o and Io indicate the mold closing speed (mold closing speed) and the drive current of the movable mold Cm in the normal state.

On the other hand, in steps S2 and S3, when a predetermined time has elapsed after the movable type Cm has reached the deceleration start position Xa, a monitoring section Zs for detecting foreign matter starts. At the start of the monitoring section Zs, the central command section 10 gives a switching command signal to the two-axis synchronization control section 15 and
The synchronization between the deviation output obtained from the 1p side and the deviation output obtained from the second deviation calculation unit 11q is released, and a process of reducing the torque to a predetermined magnitude is performed (steps S8 and S9). In this case, a process of giving a current limiting signal from the central command unit 10 to the current limiting units 13p and 13q and reducing the magnitude of the drive current I to reduce the torque is performed. In the low-pressure mold clamping, since the mold clamping pressure is relatively small, the actual drive current I is also small, and the torque may be substantially reduced to a predetermined magnitude. This is a concept included in the process of reducing the size.

Further, in the central command section 10, the monitoring section Z
During s, the magnitude of the deviation E output from the comparison unit 12 is monitored. That is, since the respective deviation outputs obtained from the first deviation calculator 11p and the second deviation calculator 11q are provided to the input unit of the deviation calculator 14, the deviation E between the deviation outputs is obtained by the deviation calculator 14 ( Step S10). In the normal state, the movable plate 8m (movable Cm) and the fixed plate 8c (fixed C
c) If there is no foreign matter in between, the variation range of the deviation E is
Since it falls within a predetermined range as indicated by a virtual line Eo shown in FIG. 5, a normal molding cycle is continued (step S11, step S11).
S12).

On the other hand, movable plate 8m (movable Cm)
When the foreign matter D is caught between the and the fixed board 8c (fixed type Cc), the following processing is performed. Normally, the movable mold Cm is in a position close to the fixed mold Cc during the low-pressure mold clamping period Ta in which the monitoring section Zs is set. Therefore, as shown in FIG. 4, if the movable C
If the foreign matter D is caught between the m and the fixed die Cc, the movable platen 8m
The (movable Cm) slightly tilts due to the presence of the foreign matter D.

As a result, the rotary encoders 7p and 7q
The difference between each output value (speed detection value) obtained from
The deviation E obtained from the deviation calculator 14 also increases. Comparison section 1
In step 2, the set value Es given from the central command unit 10 is compared with the deviation E obtained from the calculation unit 14, and when the deviation E reaches the set value Es, the foreign object detection accompanying the detection of the foreign object D is performed. Processing, that is, the mold clamping device Mc (servo motor 5p,
5q) is stopped or an alarm is output by an alarm (steps S11 and S13). FIG. 5 shows a state where the deviation E has reached the set value Es in the monitoring section Zs.

As described above, in the foreign matter detection method according to the present embodiment, the period T during which the driving pressure of the driving mechanisms 2p and 2q is low is low.
In a, a monitoring section Zs for releasing the synchronization of the driving mechanisms 2p and 2q and reducing the torque of the driving mechanisms 2p and 2q to a predetermined magnitude is set, and the monitoring section Zs is set.
Since the inclination of the movable mold Cm is monitored and the foreign matter detection processing is performed when the inclination is detected, it is necessary to determine whether or not the mold C is closed at a point in time when a predetermined time has elapsed as in the related art. This eliminates the disadvantage that the molding cycle time is prolonged, thereby improving production efficiency and productivity. In addition, since the relative speed (relative position) obtained from the pair of drive mechanisms 2p and 2q is monitored and detected, foreign object detection can be performed reliably and stably even when, for example, an origin shift due to temperature drift occurs. It can be carried out.

The embodiment has been described in detail above.
The present invention is not limited to such an embodiment,
It is possible to arbitrarily change, add, or delete the details of the configuration, method, and the like without departing from the gist of the present invention. For example, reducing the torque of the drive mechanisms 2p and 2q to a predetermined magnitude means that the drive current I is actively limited and the torque is eventually reduced due to other control factors as described above. Is a concept that includes both the passive case and the passive case.
Similarly, releasing the synchronization between the drive mechanisms 2p and 2q is a concept that includes a case where the control for synchronization is not performed from the beginning. On the other hand, the speed detection value is used as an output value obtained from the rotary encoders 7p and 7q, but may be used as a position detection value or data obtained directly. Further, a movable plate 8m (movable C
Although the case where m) is applied has been shown, an ejector pin or the like in the projecting device can also be applied.

[0028]

As described above, according to the foreign matter detection method for an injection molding machine according to the present invention, the synchronization between the drive mechanisms is released and the torque of each drive mechanism is reduced while the drive pressure of the drive mechanisms is low. While setting a monitoring section to reduce to a predetermined size, monitoring the inclination of the movable part in this monitoring section,
When the inclination becomes a predetermined size, the foreign object detection processing is performed in accordance with the detection of the foreign object, so that the following remarkable effects are obtained.

(1) Since it is not necessary to judge whether or not the mold is closed after a certain period of time as in the prior art, the disadvantage that the molding cycle time becomes longer is eliminated, and the production efficiency and productivity are improved. Can be enhanced.

(2) In order to monitor and detect the relative speed (relative position) obtained from the pair of drive mechanisms, for example,
Even when the origin drifts due to the temperature drift or the like, foreign matter detection can be performed reliably and stably.

[Brief description of the drawings]

FIG. 1 is a flowchart for explaining a mold clamping operation of a mold clamping device including a foreign matter detection method according to a preferred embodiment of the present invention;

FIG. 2 is a schematic configuration diagram including a partial cross section of an injection molding machine capable of performing the foreign matter detection method,

FIG. 3 is a block diagram of a controller provided in a mold clamping device of the injection molding machine;

FIG. 4 is a schematic configuration diagram including a partial cross section showing a mold clamping state of the mold clamping device,

FIG. 5 is a timing chart showing a signal change of each unit when the foreign matter detection method is performed.

[Explanation of symbols]

 2p drive mechanism (first drive mechanism) 2q drive mechanism (second drive mechanism) 3 movable part 4 fixed part 5p servo motor 5q servo motor 6p ball screw mechanism 6q ball screw mechanism 7p rotary encoder 7q rotary encoder 8m movable plate M injection molding Machine D Foreign matter Ta Period during which driving pressure is low Zs Monitoring section Mc Clamping device Cm Movable type

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Susumu Ryokaku 2110 Namjo, Nanjo, Hanagi-gun, Hanishina-gun, Nagano Nissei Plastic Industry Co., Ltd.

Claims (4)

[Claims] 1. A foreign matter detection method for an injection molding machine for detecting foreign matter caught between a pair of fixed parts when a movable part is moved by a pair of drive mechanisms. In addition, while setting a monitoring section for releasing the synchronization between the driving mechanisms and reducing the torque of each driving mechanism to a predetermined value, monitoring the inclination of the movable portion in this monitoring section, the inclination is set in advance. A foreign matter detection method for an injection molding machine, wherein a foreign matter detection process is performed in accordance with the detection of a foreign matter when the size becomes large. 2. The method according to claim 1, wherein the drive mechanism includes a servomotor and a ball screw mechanism that converts a rotational motion of the servomotor into a linear motion. 3. The foreign matter detection method for an injection molding machine according to claim 2, wherein the inclination of the movable part is detected by a deviation of an output value obtained from a rotary encoder provided in each servomotor. 4. The movable portion is a movable plate that supports a movable mold provided in a mold clamping device, and the period in which the driving pressure is low is a period in which a transition from high-speed mold closing to low-pressure mold clamping is performed. 2. The method for detecting foreign matter in an injection molding machine according to claim 1, wherein: