JP5755627B2 - Nozzle touch method and touch device for injection molding machine - Google Patents

Description

  The present invention relates to a nozzle touch method and a touch device of an injection molding machine, in which an injection nozzle is touched to a touch part of a sprue bush by a nozzle touch device, and the touch force is gradually increased and pressed with a predetermined touch force. .

  The injection molding machine is generally composed of an injection unit and a mold clamping unit as is well known in the art. The injection unit includes a heating cylinder, a screw that can be driven in the rotation direction and the axial direction inside the heating cylinder, a drive device that drives the screw, and the like, and an injection nozzle is provided in front of the heating cylinder. It has been. On the other hand, the mold clamping unit is composed of a fixed mold attached to the fixed platen and a movable mold attached to the movable plate in the same manner. The mold is tightened. Therefore, when the screw of the injection unit is driven to rotate and the injection material is supplied to the heating cylinder, the injection material is plasticized and measured in a measuring chamber in front of the heating cylinder as is well known in the art. Therefore, when the screw is driven in the axial direction, the injection material in the measuring chamber is injected into the cavity of the clamped mold, and after waiting for cooling and solidification, the movable mold is opened to obtain a molded product having a predetermined shape.

  When measuring and injecting as described above, the injection nozzle is connected to the nozzle touch part of the sprue bush of the fixed mold by the nozzle touch device, for example, back pressure during measurement, during injection It is designed to be pressed with a touch force that resists the reaction force received by the injection pressure or the like. Shift molding methods and touch molding methods are known as molding methods for injecting an injection nozzle by touching a fixed mold in this way. That is, when the injection nozzle is pressed against the sprue bush of the fixed mold, heat is taken away from the low-temperature mold, and the molten resin may harden at the tip of the nozzle. In order to prevent this, after the completion of weighing, the injection nozzle is moved away from the mold, and the shift molding method in which the injection nozzle is touched again and molded as described above immediately before the injection, and the touch molding in which the injection nozzle is kept in contact with the nozzle touch part. The method is known. Such an injection nozzle is separated from the nozzle touch portion of the mold when the heating cylinder assembly is replaced.

JP 11-320611 A Japanese Patent Laid-Open No. 2003-231166 JP-A-6-226787

  There are various types of nozzle touch devices such as a hydraulic type and an electric type. Patent Document 1 describes an example of a hydraulic type, and examples of an electric type are described in Patent Documents 2 and 3, respectively. The hydraulic nozzle touch device described in Patent Document 1 includes a moving cylinder that advances and retracts an injection unit, an electromagnetic switching valve that switches pressure oil supplied to the cylinder, first and second relief valves, and a pressure in the moving cylinder. It consists of a pressure switch to detect. Therefore, by switching the circuit by the electromagnetic switching valve, the injection nozzle can be touched on the touch part of the mold by the moving cylinder and can be retracted. The touch force at this time is determined by the set pressure of one of the first and second relief valves, and the duration of the touch is determined by the time measured by the timer after the pressure switch detects a predetermined pressure. It has become.

  In the nozzle touch device described in Patent Document 2, an induction motor is applied as a drive source of the injection unit. The load of the induction motor is controlled by detecting a current value and a voltage value applied to the induction motor and calculating a power value from the detected value. By accurately controlling the load of the induction motor, the nozzle touch force can be accurately controlled over a wide range.

  A servo motor is applied to the nozzle touch method described in Patent Document 3. The injection nozzle touch force is the minimum touch force that prevents the molten resin from leaking from the tip of the nozzle when injecting the molten resin, while the reaction force that the injection unit receives during holding pressure other than injection. The size is selected by adding the above minimum touch force.

  As can be understood from the above description, if the pressure contact force or touch force to the sprue bush of the injection nozzle is weak, the resin leaks from the tip of the nozzle at the time of injection, which may solidify and cause a touch failure. Can cause short shots. On the other hand, if it is too strong, the injection nozzle, sprue bush and eventually the mold will be damaged. By the way, according to the nozzle touch device described in Patent Document 1, since the pressure of the hydraulic oil supplied to the moving cylinder is controlled by the relief valve, it is possible to avoid insufficient touch force and excessive touch force. Moreover, according to the nozzle touch control method described in Patent Document 2, the current value and pressure value of the induction motor that drives the injection nozzle are detected, the power value is calculated, and the load is controlled. However, there seems to be no such problem. Further, according to the invention described in Patent Document 3, the touch force is set in two stages, and during injection, the molten resin is prevented from leaking between the tip portion of the nosle and the touch portion of the sprue bush due to the filling pressure. An effect is obtained that the clamping unit does not tilt during pressing.

  As described above, even in the conventional nozzle touch device, since a good nozzle touch force is obtained, insufficient pressure contact and excessive pressure contact should be avoided, but problems arise in reality. ing. But the problem is overlooked. For example, when the tip of the nozzle is abnormally worn, when the resin is stuck to the tip of the nozzle, when the tip of the nozzle is bent, when the sprue bush is recessed, etc. This is because the resin leaks, but when the nozzle touch is completed, it is pressed with a predetermined touch force. Further, as shown in FIG. 3, the nozzle touch portion NT of the sprue bush SB of the fixed die KK has a hemispherical surface, while the shape of the tip portion of the injection SN also becomes a hemispherical surface. Since the diameter is smaller than the diameter of the nozzle touch part NT, even if the axis of the injection nozzle SN is deviated from the axis of the nozzle touch part NT, if the touch proceeds, the injection nozzle SN will become the nozzle touch part NT. Forcibly guided by the spherical surface, the axes coincide with each other. Then, the contact is made with a predetermined touch force. As a result, the pressure contact is made with a predetermined touch force, but there is a delay until the touch is completed, and there is a large friction between the nozzle touch part NT and the tip of the injection nozzle SN. Wear occurs during this period and breaks early. However, even in such a case, since it is finally pressed by a predetermined touch force, it cannot be detected by the conventional nozzle touch method.

  Therefore, when the nozzle touch process in which the tip portion of the injection nozzle is pressed against the nozzle touch portion of the sprue bush provided on the mold with a predetermined nozzle touch force, foreign matter is caught, resin leakage, injection It is an object of the present invention to provide a nozzle touch method for an injection molding machine that can detect an abnormality such as misalignment of a nozzle and a nozzle touch device that is used to implement this method.

  The present invention has been made on the basis of the knowledge that the injection nozzle shows a predetermined pattern until it comes into contact with the nozzle touch part of the sprue bush of the mold and is pressed with a predetermined touch force. The pattern is stored in the storage unit of the controller, and compared with the measurement pattern detected in the nozzle touch process, a determination is made based on whether or not an allowable value is exceeded.

That is, in order to achieve the above object, the invention according to claim 1 makes the injection nozzle of the injection unit touch the touch part of the sprue bush of the clamping unit by the nozzle touch device, and gradually increases the touch force. In a nozzle touch process for press-contact with a predetermined set touch force, as a preliminary process, a pattern of change in touch force until the ejection nozzle is normally brought into contact with the touch portion and the set touch force is reached is used as a reference pattern. The measurement pattern, which is a change in touch force obtained in the nozzle touch step, is compared with the reference pattern, and in the measurement pattern, the touch force reaches the set touch force after reaching the set touch force vicinity. When the time is longer than that of the reference pattern, foreign matter is present between the injection nozzle and the touch part. Configured as a nozzle touch method for an injection molding machine and judging that the rare.
According to a second aspect of the present invention, the nozzle touch of the injection unit is made to touch the touch part of the sprue bush of the mold clamping unit with the nozzle touch device, and the touch force is gradually increased to press-contact with a predetermined set touch force. In the process, as a pre-process, the touch that is obtained in the nozzle touch process is obtained as a reference pattern by making the ejection nozzle normally contact the touch part and obtaining a touch force change pattern until the set touch force is reached. The measurement pattern, which is a change in force, is compared with the reference pattern. In the measurement pattern, when the touch force decreases in the middle and then increases, the axes of the injection nozzle and the touch portion become inconsistent. It is determined as a nozzle touch method for an injection molding machine.
According to a third aspect of the present invention, in the injection molding machine including the controller, the injection nozzle of the injection unit is made to touch the touch part of the sprue bush of the mold clamping unit, and the touch force is gradually increased to obtain a predetermined set touch force. A nozzle touch device that performs a nozzle touch process for press-contacting at a pressure, wherein the controller touches the injection nozzle until it normally contacts the touch part of the sprue bush of the mold clamping unit and is pressed by the set touch force. Storage means for storing a reference pattern that is a change pattern of the above, computing means for obtaining a measurement pattern that is a change in touch force for each nozzle touch step, comparison means for comparing the reference pattern and the measurement pattern, Alarm means for issuing an alarm when the measurement pattern is shifted beyond a predetermined allowable range with respect to the reference pattern; Yes and configured as a nozzle touch apparatus for an injection molding machine which comprises carrying out the nozzle touch method according to claim 1 or 2.

As described above, according to the present invention, data consisting of a relationship between a predetermined time and a nozzle touch force between a normal nozzle touch without abnormality and a set touch force that is a predetermined touch force, that is, a reference pattern Is obtained in advance. And compared with the measurement pattern measured in the normal nozzle touch process, when it exceeds the allowable value, it is determined that the nozzle touch is abnormal. Accordingly, it is possible to easily know abnormalities such as foreign object pinching, resin leakage, and misalignment of the injection nozzle. According to the first aspect of the present invention, there is an abnormality in which a foreign substance such as a resin is sandwiched between the injection nozzle and the touch part. According to the second aspect , the axis of the injection nozzle and the touch part is not correct. Since each of the matched abnormalities can be detected, the abnormalities can be determined accurately and reliably.

1 is a front view showing a cross section of a part of an injection molding machine according to an embodiment of the present invention. It is a graph which shows the relationship between the elapsed time and nozzle touch force in a nozzle touch process. It is a front view which shows the relationship between the conventional injection nozzle and a nozzle touch part in a partial cross section.

  The present invention can also be implemented by the hydraulic type as described above, but first, an embodiment of the nozzle touch device by the restoring force of the electric spring will be described, and the other electric type and hydraulic type will be briefly described at the end. explain. As shown in FIG. 1, the injection molding machine according to the present embodiment is externally composed of an injection unit 1, a mold clamping unit 10, and a nozzle touch device 30 in the same manner as a conventional injection molding machine. It is configured. The injection unit 1 includes a heating cylinder 2. A screw is inserted into the heating cylinder 2 so as to be driven in the rotational direction and the axial direction as is well known in the art. An injection nozzle 3 is provided in front of the heating cylinder 2, a hopper 4 is provided near the rear, and a screw drive device 5 is provided at the rear end. The injection unit 1 configured in this way is supported by the gantry 6 so as to be movable in the front-rear direction. Therefore, the tip of the injection nozzle 3 can be touched to the sprue bush 21 of the fixed mold of the mold clamping unit 10 provided in a fixed manner, and can be separated.

  The mold clamping unit 10 includes a fixed platen 12 fixedly provided on the mold clamp 11, a movable platen 13 movably provided in the axial direction, a fixed side mold 14 attached to the fixed platen 12, The movable platen 15 is attached to the movable platen 13, and includes a mold clamping device (not shown). A cavity 16 for forming a molded product is formed between the parting lines of the fixed side mold 14 and the movable side mold 15. A through hole 17 through which the injection nozzle 3 is inserted is formed in the fixed platen 12, and a sprue bush 20 is fitted into a fixed mold 14 corresponding to the through hole 17. A portion of the sprue bush 20 corresponding to the injection nozzle 3 is a nozzle touch portion 21. The nozzle touch portion 21 has a hemispherical shape, and the diameter thereof is larger than the diameter of the hemispherical diameter of the tip portion of the injection nozzle 3. A sprue 22 communicating with the cavity 16 from the nozzle touch portion 21 thus configured is formed.

  According to the present embodiment, the nozzle touch device 30 includes a brake-equipped electric motor 31 to which the brake 32 is applied when stopped, a ball screw 34, a ball nut 35 screwed into the ball screw 34, a spring 38, and the like. The ball screw 34 is driven by the electric motor 31 via a speed reducer or the like. The ball screw 34 has a predetermined length in the front-rear direction, one of which is rotatably supported by a bearing 33 that also receives a thrust load attached to the fixed platen 12, and the other is rotatably supported by a bearing (not shown). The ball nut 35 is movable in the axial direction, but the rotation direction is restricted by a member not shown. Therefore, when the ball screw 34 is driven to rotate, the ball nut 35 screwed to the ball screw 34 is driven in the axial direction. A drive member 37 is integrally attached to the ball nut 35 that moves in this manner.

  A joint 40 is attached to a portion of the injection unit 1 facing the mold clamping unit 10, and one end of a drive rod 41 is attached to the joint 40. The drive rod 41 extends by a predetermined amount toward the mold clamping unit 10. A portion extending downward in a key shape is a load receiving portion 42. A spring 38 is interposed between the load receiving portion 42 and the drive member 37 described above.

  A sensor rod 45 extending toward the mold clamping unit 10 is attached to the drive member 37 configured as described above, and an encoder 46 that outputs a pulse in association with the displacement in the axial direction in relation to the sensor rod 45. Is provided in the load receiving portion 42. The sensor rod 45 and the encoder 46 measure the distance between the drive member 37 and the load receiving portion 42, that is, the compression amount of the spring 38, and thus the touch force of the injection nozzle 3.

  According to the present embodiment, the injection molding machine or nozzle touch device 30 also includes the controller 47. The controller 47 has a comparison function, a calculation function, a timer function, various setting means, etc., as will be described in the operation section. For example, it has a function of calculating the amount of compression of the spring 38, that is, the touch force after a set time from the start of the timer. Such a controller 47 is connected to the encoder 46 by a signal line a and to the brake-equipped electric motor 31 by a signal line b.

  Next, the operation of the above embodiment will be described. First, as a preliminary process, the relationship between the time from when the injection nozzle 3 comes into contact with the nozzle touch portion 21 until it is pressed with a set touch force, which is a predetermined touch force, and the touch force at a predetermined time within that time A reference pattern consisting of At this time, the injection nozzle 3 normally touches the nozzle touch part 21. That is, normal nozzle touch without any abnormality such as foreign object pinching, resin leakage, and misalignment of the injection nozzle is performed. Then, a reference pattern to be a determination reference in the subsequent nozzle touch process is obtained.

  Specifically: The controller 47 sets the position of the injection unit 1 at which a predetermined set touch force can be obtained. That is, the numerical value of the position where the electric motor 31 is stopped is set. Sets the sampling period for measuring the touch force as a pattern. For example, an interval of 0.1 seconds is set. And the electric motor 31 with a brake is started. The ball screw 34 is rotationally driven by the electric motor 31, the ball nut 35, and hence the drive member 37 is driven toward the mold clamping unit 10, and the injection unit 1 is driven toward the mold clamping unit 10 via the spring 38. The spring 38 is not compressed until the injection nozzle 3 touches the nozzle touch part 21. That is, the distance between the drive member 37 and the load receiving member 42 does not change. Therefore, no pulse signal is output from the encoder 46.

  Eventually, for example, after 2.5 seconds, the injection nozzle 3 touches the nozzle touch part 21 of the sprue bush 20 and the spring 38 starts to be compressed. Since the distance between the drive member 37 and the load receiving member 42 begins to narrow, the encoder 46 starts counting the number of pulses and inputs it to the controller 47. The touch force is calculated from the number of pulses, that is, the compression amount of the spring 38. Thereafter, the touch force every 0.1 second is calculated in the same manner.

  The relationship between the time thus obtained and the touch force is shown in Table 1, and the graph is shown by a curve S in FIG. This curve S shows the reference pattern. The curve S of the reference pattern rises smoothly immediately after the ejection nozzle 3 touches the nozzle touch part 21 until it reaches the set touch force Sp that is the final touch force. Such a reference pattern is stored in the controller 47, and an allowable value or threshold value for the reference pattern is set. Complete the pre-process.

  When carrying out the actual process, that is, the actual molding process, the injection unit 1 is activated to plasticize the pellets in the hopper 4. Then, the tip end portion of the injection nozzle 3 is pressed against the nozzle touch portion 21. Or it plasticizes after pressing. The screw of the injection unit 1 is driven in the axial direction to inject and fill the cavity 16 of the mold clamping unit 10. After cooling and solidifying, the movable mold 15 is opened to obtain a molded product.

  In the nozzle touch process, when the tip of the injection nozzle 3 is pressed against the nozzle touch part 21, the controller 47 calculates the touch force every 0.1 second as described above, and measures the change in the touch force. Get a pattern. A curve X in FIG. 2 shows an example of a measurement pattern when a foreign substance such as resin is sandwiched between the injection nozzle 3 and the nozzle touch part 21. In the curve X, when the leaked resin is solidified at the tip of the injection nozzle 3, the nozzle touch portion 21 or the like, or when a solid substance is adhered, the touch is made earlier, and the spring 38 starts to compress. Touch force begins to occur. However, with respect to the rising of the rising curve of the touch force, the change in curvature is almost the same as the reference pattern. That is, if the measurement pattern is moved in parallel in the time axis direction, it almost matches the reference pattern. However, when the touch force approaches the vicinity of the set touch force Sp, the solidified resin changes, such as crushing, and the increase in the touch force becomes dull (Xp point), reaching the set touch force with a predetermined time delay. When the leaked resin adheres to the tip of the injection nozzle 3, the change in the touch force may temporarily deviate from the reference pattern during the increase in the touch force, as indicated by the symbol Xq. .

  In FIG. 2, a curve Y is a graph showing an example of a measurement pattern when the axes of the injection nozzle 3 and the nozzle touch part 21 are shifted. In the curve Y, since the axes of the injection nozzle 3 and the nozzle touch portion 21 are deviated, the spring 38 starts to be compressed at an early stage. On the other hand, with respect to the rising of the rising curve of the touch force, the change in the curvature almost coincides with the reference pattern. That is, if the measurement pattern is moved in parallel in the time axis direction, it almost matches the reference pattern. However, when the touch force increases to some extent, the injection nozzle 3 is forcibly guided by the spherical surface of the nozzle touch portion 21 and gently slides in a direction in which the axes coincide. During this gentle slip, the compression of the spring 38 stops and the touch force (Yp point) does not increase. Thereafter, the injection nozzle 3 quickly slides in a direction coinciding with the axis of the nozzle touch portion 21 without being able to withstand a gentle slip. That is, a knocking phenomenon occurs. As a result, the touch force rapidly decreases like the Yq point. After that, the touch force increases again.

  Since the measurement pattern deviates from the reference pattern in accordance with various abnormalities in this way, a measurement pattern is obtained for each slip touch process, and compared with this and the reference pattern, if the deviation from the reference pattern exceeds the allowable range It can be determined that an abnormality has occurred. Although the measurement pattern and the reference pattern can be compared by various methods, in the nozzle touch method according to the present embodiment, for example, an abnormality of foreign object pinching is detected as follows. In the controller 47, a threshold touch force St in the vicinity of the set touch force Sp is set in advance. The threshold touch force St is determined to be 90% of the set touch force Sp, for example. In the reference pattern, a time Ts from reaching the threshold touch force St to reaching the set touch force Sp is obtained. In the measurement pattern of the nozzle touch process, a time Tx from reaching the threshold touch force St to reaching the set touch force Sp is obtained. If the time Tx is longer than the time Ts of the reference pattern by a predetermined time, it is determined that a foreign object is sandwiched between the injection nozzle 3 and the nozzle touch unit 21, and the controller 47 issues an alarm.

  Abnormalities in the misalignment of the axes of the injection nozzle 3 and the nozzle touch portion 21 can be detected as follows, for example. In the measurement pattern of the nozzle touch process, when the touch force decreases rapidly and then the touch force increases, it is determined that the axes of the injection nozzle 3 and the nozzle touch unit 21 are inconsistent and an alarm is issued. Note that it may be determined that the shaft centers are misaligned when the touch force rapidly decreases.

  The comparison between the measurement pattern and the reference pattern is not limited to the above embodiment, and various comparisons are possible. For example, if a deviation from the reference pattern occurs in the curve where the touch force is increasing, as indicated by the symbol Xq, it can be determined that some abnormality has occurred. Further, even when the generation timing of the touch force is earlier than the reference pattern, it can be determined that some abnormality has occurred.

  In the present embodiment, the touch force is generated by the compression amount or restoring force of the spring, so that there is an advantage that the impact when the tip of the injection nozzle 3 comes into contact with the nozzle touch portion 21 is reduced. The driving force of the electric motor can be obtained from the current value supplied to the electric motor, thereby obtaining the touch force. Alternatively, a touch force can be obtained from a strain sensor or the like. In the case of a hydraulic injection molding machine in which the injection unit is driven by a hydraulic cylinder unit, the touch force can be monitored by a hydraulic pressure sensor.

DESCRIPTION OF SYMBOLS 1 Injection unit 3 Injection nozzle 10 Clamping unit 14 Fixed mold 20 Sprue bush 21 Nozzle touch part
30 Nozzle touch device 34 Ball screw 35 Ball nut 38 Spring
45 Sensor bar 46 Encoder 47 Controller

Claims (3)

In the nozzle touch process in which the injection nozzle of the injection unit is touched to the touch part of the sprue bush of the clamping unit by the nozzle touch device, and the touch force is gradually increased and pressed with a predetermined set touch force,
As a preliminary step, the injection nozzle is normally brought into contact with the touch portion, and a pattern of change in touch force until the set touch force is reached is obtained as a reference pattern.
A measurement pattern that is a change in touch force obtained in the nozzle touch step is compared with the reference pattern, and in the measurement pattern, a time until the touch force reaches the set touch force after the touch force reaches the vicinity of the set touch force. A nozzle touch method for an injection molding machine, wherein when it is longer than the reference pattern, it is determined that a foreign matter is sandwiched between the injection nozzle and the touch part. In the nozzle touch process in which the injection nozzle of the injection unit is touched to the touch part of the sprue bush of the clamping unit by the nozzle touch device, and the touch force is gradually increased and pressed with a predetermined set touch force,
As a preliminary step, the injection nozzle is normally brought into contact with the touch portion, and a pattern of change in touch force until the set touch force is reached is obtained as a reference pattern.
A measurement pattern that is a change in touch force obtained in the nozzle touch step is compared with the reference pattern. In the measurement pattern, when the touch force decreases in the middle and then increases, the injection nozzle and the touch unit A nozzle touch method for an injection molding machine, characterized in that it is determined that the axes of the nozzles are inconsistent. In an injection molding machine equipped with a controller, a nozzle touch process is performed in which an injection nozzle of an injection unit is touched to a touch part of a sprue bush of a mold clamping unit, and the touch force is gradually increased and pressed with a predetermined set touch force. A nozzle touch device,
The controller includes a storage unit that stores a reference pattern that is a change pattern of a touch force until the injection nozzle is normally brought into contact with a touch part of a sprue bush of a mold clamping unit and pressed with the set touch force; and the nozzle A calculation unit that obtains a measurement pattern that is a change in touch force for each touch process, a comparison unit that compares the reference pattern and the measurement pattern, and the measurement pattern exceeds a predetermined allowable range with respect to the reference pattern deviation by chromatic and alarm means for issuing an alarm when that, injection molding machine nozzle touch apparatus which comprises carrying out the nozzle touch method according to claim 1 or 2.

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