JP2010247410A - Method and device for protecting mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for protecting a mold that makes complicated setting unnecessary every time the mold is exchanged, and that exactly stops mold closing operation when a foreign substance is caught between the molds. <P>SOLUTION: When a movable mold (12) is closed to a fixed mold (11) and fastened by a predetermined fastening force, a vibration of a fixed platen (5) is monitored in the area from the open mold position where the movable mold (12) is by a predetermined distance apart from the fixed mold (11) to the closed mold position where the movable mold (12) touches the fixed mold (11), and the mold closing operation is stopped when a velocity of acceleration exceeding a predetermined threshold is detected. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention includes a stationary platen to which a fixed mold is attached, a movable platen to which a movable die is attached, a mold clamping housing, and a plurality of tie bars that penetrate the movable platen and connect the fixed platen and the mold clamping housing. A toggle mold clamping device comprising a toggle mechanism provided between the movable platen and the mold clamping housing, wherein the mold can be opened and closed by driving a crosshead of the toggle mechanism. The present invention relates to a method for detecting foreign matter caught in a movable mold and protecting the mold so that the mold is not damaged, and a toggle type mold clamping device used for carrying out this method.

  The injection molding machine is well known without mentioning the literature name. In general, an injection device that melts and injects an injection material, a pair of molds that are clamped and opened, and the mold is attached. It comprises a mold clamping device or the like that drives the mold in the mold clamping direction or mold opening direction. A toggle type mold clamping device is also well known as a mold clamping device. The toggle type mold clamping device is provided between a stationary platen fixed on the mold clamping bed, a mold clamping housing that is axially movable on the mold clamping bed, and between the stationary platen and the mold clamping housing. Four tie bars, a movable plate provided on the mold clamping bed so as to be movable in the axial direction and through which the tie bar is inserted, a toggle mechanism provided between the mold clamping housing and the movable plate, and the like. It is configured. Therefore, when the toggle mold clamping device is driven to clamp the pair of molds, a cavity is formed in the mold. When the molten injection material is injected and filled into this cavity from the injection device, and after waiting for cooling and solidification, the mold clamping device is driven and the mold is opened to obtain a molded product.

  The molded product molded in this way is ejected by an eject pin provided in the mold, and naturally falls onto a tray provided below. Alternatively, the molded product is ejected by an eject pin and lifted from the mold, and is taken out by a robot arm provided in association with the injection molding machine. However, if the ejection of the eject pin is insufficient or the operation of the eject pin and the robot arm is shifted, the molded product is left in the mold. In this state, when the toggle mold clamping device is driven and the mold is clamped, the remaining molded product is placed on the parting line of the mold and sandwiched between the molds, and the expensive mold is damaged. End up. Even if foreign matter enters between the molds, the mold is similarly damaged when the toggle type clamping device is driven and the mold is clamped.

JP 09-254218 A Special table 2008-512275 gazette

Patent Document 1 describes a toggle type mold clamping device in which a strain sensor is provided on a toggle mechanism, a movable platen, or a mold clamping housing, and a mold protection method for detecting the amount of strain and controlling the mold clamping force. ing. According to Patent Document 1, a mold clamping force is calculated by a predetermined calculation from a strain amount detected by a strain sensor. When the mold clamping force exceeds a preset threshold value, the mold clamping device is controlled so that the mold clamping force does not exceed that level, assuming that a foreign object is in an abnormal state between the molds. To do. Therefore, even if a molded product or a foreign object is caught in the mold, the mold is not damaged.
Patent Document 2 discloses a mold protection method in which a mold clamping force is measured and a mold clamping device is stopped when a deviation amount from a set target mold clamping force exceeds an allowable amount over a predetermined time. Is described. Patent Document 2 does not describe the type of sensor used, the member provided with the sensor, etc., so the method for measuring the mold clamping force is unknown, and the specific implementation method is not clear. However, according to the method described in Patent Document 2, the target mold clamping force is treated as a variable that changes according to the position of the movable mold attached to the movable platen. Therefore, the target mold clamping force is determined in advance as a function of the position of the movable mold. Then, the position of the movable mold and the clamping force are measured, and when the deviation of the clamping force with respect to the target clamping force exceeds an allowable amount over a predetermined time, the clamping device is stopped. . Therefore, even if a molded product or a foreign object is sandwiched in the mold, the mold can be protected without damaging the mold.

  Also by the method described in Patent Document 1 or Patent Document 2, it is possible to control the mold clamping device by monitoring the mold clamping force or to stop the mold clamping device. The mold can be protected. However, there are some points that should be improved. For example, there is a problem in that the object being monitored is a mold clamping force. Since the appropriate mold clamping force varies depending on the mold, the threshold value of the mold clamping force and the target mold clamping force also vary depending on the mold. Therefore, even if the threshold value and the target mold clamping force are set, if the mold attached to the mold clamping device is replaced, the threshold value and the target mold clamping force must be reset, which is complicated. . Further, according to the method described in Patent Document 1, the strain amount that is a basis for calculating the mold clamping force is detected by the strain sensor, but there is a problem in the member provided with the strain sensor. In other words, the strain sensor is provided on the toggle mechanism, movable platen, or mold clamping housing. The toggle mechanism and movable platen move greatly when the mold is opened and closed, and the mold clamping housing also moves slightly to the left and right as the tie bar extends. End up. In such a member, stress is generated inside the member due to acceleration accompanying movement, and distortion that does not originate from the clamping force is generated. Accordingly, there is a case where an accurate mold clamping force cannot be calculated from the detected strain amount, and even if a foreign object is caught in the mold, the detection may be delayed and the mold may be damaged. Further, according to the method described in Patent Document 2, since the target clamping force is set according to the position of the movable mold, it can be considered that the abnormality can be detected relatively accurately. There is a problem in that the mold clamping force is monitored even in the mold open position. That is, the mold opening position where foreign matter is caught in the mold is when the mold opening amount is relatively small, but according to the method described in Patent Document 2, even at the mold opening position where there is no possibility of foreign matter being caught in the mold. Since monitoring is performed in the same way, there is a high possibility of malfunction due to noise picked up.

  The present invention has been made in view of the above-described problems. Specifically, it is not necessary to make complicated settings each time the mold is replaced, and therefore, maintenance is easy and noise is picked up. A mold protection method that can reliably detect that a foreign object has been caught in the mold without causing malfunction, and stop the mold clamping operation, and a toggle mold that is directly used to implement this protection method The object is to provide a fastening device.

  In the present invention, in order to achieve the above object, an acceleration sensor is provided on a stationary plate to which a stationary mold is attached, and the acceleration of the vibration of the stationary plate detected by the acceleration sensor is input to a controller that controls the toggle mechanism. To do. When the movable mold is clamped to the fixed mold by driving the crosshead, the movable mold touches the fixed mold from the mold opening position where the movable mold is opened by a predetermined mold opening amount. The vibration of the stationary platen is monitored until the mold closing position, and when the vibration exceeding the predetermined threshold is detected, the cross head is stopped and the mold closing operation is stopped. The predetermined mold opening amount and mold closing position are determined based on the position of the cross head.

  Thus, in order to achieve the object, the invention according to claim 1 penetrates through the movable platen, the fixed platen to which the fixed die is attached, the movable platen to which the movable die is attached, the mold clamping housing, and the movable platen. A plurality of tie bars connecting the fixed plate and the mold clamping housing, and a toggle mechanism provided between the movable platen and the mold clamping housing, and driving a crosshead of the toggle mechanism. In the mold that can be opened and closed by the mold, when the movable mold is closed with respect to the fixed mold and clamped with a predetermined clamping force, the movable mold is the fixed mold. From the mold open position separated by a predetermined amount from the mold open position where the movable mold touches the fixed mold, the vibration of the fixed platen or the fixed mold is monitored, and a predetermined threshold value is set. If you detect vibration with acceleration exceeding Configured to stop the mold closing operation. According to a second aspect of the present invention, in the protection method according to the first aspect, the mold opening position and the mold closing position are determined based on a position of the crosshead, and the invention according to the third aspect. In the protection method according to claim 1 or 2, the vibration is monitored by an acceleration sensor provided on the fixed platen or the fixed mold.

According to a fourth aspect of the present invention, there is provided a stationary platen to which a fixed mold is attached, a movable platen to which a movable mold is attached, a mold clamping housing, and the movable platen that penetrates the movable platen and connects the stationary platen and the mold clamping housing. A plurality of tie bars, and a toggle mechanism provided between the movable platen and the mold clamping housing, and the mold is opened and closed when the crosshead of the toggle mechanism is driven. In the toggle type mold clamping device,
The fixed plate or the fixed mold is provided with an acceleration sensor, and the acceleration of the fixed plate or the fixed mold measured by the acceleration sensor is input to a controller that controls the toggle mechanism. In the mold clamping process in which the movable mold is closed with respect to the fixed mold and clamped with a predetermined clamping force, the movable mold is moved from the predetermined mold open position to the movable mold. If acceleration exceeding a predetermined threshold is detected while the mold is driven to the mold closing position where the mold is touched, the mold clamping process is stopped by a command from the controller. The invention according to claim 5 is configured as an electric injection molding machine including the toggle type mold clamping device according to claim 4.

  As described above, according to the present invention, in the toggle type mold clamping device, when the fixed mold and the movable mold are closed and clamped with a predetermined clamping force, the fixed mold and the movable mold have a predetermined amount. The vibration of the fixed platen or the fixed mold is monitored from the separated mold opening position to the touching mold closing position, and when vibration with acceleration exceeding a predetermined threshold is detected, the crosshead is stopped and the mold closed. Since the operation is stopped, when a foreign object is caught in the mold, this can be reliably detected and the mold closing operation can be stopped. That is, the object to be monitored is the vibration of a fixed platen or fixed die fixed on the bed, and the fixed platen or fixed die is not a movable member, so that it is not affected by the acceleration caused by the movement of the member. . That is, if a foreign object is caught in a metal mold | die, this can be detected reliably. In addition, since physical quantities that depend on the mold, such as mold clamping force, are not targeted for detection, that is, vibration that does not depend on molds with different mold clamping forces is detected each time, it is set even if the mold is replaced. There is no need to change the value. That is, maintenance is easy. Furthermore, the vibration is monitored from the mold open position where the fixed mold and the movable mold are separated by a predetermined interval to the mold closed position where the touch is made, that is, a state in which foreign matter may be caught in the mold. Because it only monitors, there is no need to pick up unwanted noise. That is, no malfunction occurs. And if it detects that the foreign material was pinched | interposed into the metal mold | die, since a cross head will be stopped and a mold closing operation | movement will be stopped, a metal mold | die can be protected without damaging a metal mold | die. Further, according to another invention, the mold opening position and the mold closing position are determined based on the position of the crosshead, so that the mold opening position and the mold closing position can be easily determined. Can be easily implemented. Furthermore, according to another invention, in the toggle type mold clamping apparatus, an acceleration sensor is provided in the fixed platen or the fixed die, and the acceleration of the fixed platen or the fixed die is input to the controller that controls the toggle mechanism. In other words, since the known toggle type mold clamping device has a simple configuration in which an inexpensive sensor is provided, a toggle type mold clamping device capable of protecting the mold is provided at low cost. Is possible.

It is a front view which shows the toggle type mold clamping apparatus which concerns on embodiment of this invention. It is a graph for demonstrating the effect | action of the toggle type mold clamping apparatus which concerns on this Embodiment, ie, the graph which shows the change of the vibration of the stationary platen in each position of a crosshead.

  Hereinafter, this embodiment will be described. As shown in FIG. 1, the injection molding machine 1 according to the present embodiment includes a toggle type mold clamping device 2 and a conventionally known injection device 3. The toggle type mold clamping apparatus 2 according to the present embodiment is configured in substantially the same manner as a conventional toggle type mold clamping apparatus, as can be easily understood with reference to FIG. That is, the toggle type mold clamping device 2 includes a stationary platen 5 fixedly provided on the bed B, a mold clamping housing 6 provided on the bed B so as to be movable in the axial direction, a stationary platen 5 and the mold clamping. The four tie bars 7, 7,... Provided between the housing 6 and the tie bars 7, 7,... Are inserted and movable in the axial direction, the mold clamping housing 6 and the movable plate 8. And a toggle mechanism 10 provided between them. A fixed mold 11 is attached to the fixed platen 5 thus configured, and a movable mold 12 is attached to the movable platen 8. The fixed platen 5 has a through hole 5a having a predetermined size. The heating cylinder 3b of the injection device 3 is inserted into the through hole 5a, and a sprue in which the injection nozzle 3a at the tip is provided in the fixed mold 11 is provided. Is touching.

  The toggle mechanism 10 also has a conventionally known structure. That is, in the embodiment shown in FIG. 1, a pair of short links 15, 15, a pair of long links 16, 16, a crosshead 17, a pair of crosslinks 18, 18. One end of the short links 15 and 15 is pivoted to the bracket of the clamping housing 6 by the pins 20 and 20, and one end of the long links 16 and 16 is pivoted to the bracket of the movable platen 8 by the pins 21 and 21, respectively. The other ends of the short links 15 and 15 and the other ends of the pair of long links 16 and 16 are rotatably connected by pins 23 and 23. The end portions of the cross links 18 and 18 are rotatably coupled to the cross head 17 by pins 25 and 25, and the other end portions of the cross links 18 and 18 are predetermined portions of the short links 15 and 15. Are connected to each other by pins 26 and 26 in a rotatable manner.

  The cross head 17 is attached to the tip of the ball screw 28 in a conventionally known manner, and the ball screw 28 is inserted into a through hole formed in a substantially central portion of the mold clamping housing 6. A ball nut 29 is rotatably provided in the mold clamping housing 6, and a ball screw 28 is screwed to the ball nut 29. Since the ball nut 29 is provided in the mold clamping housing 6 in a state in which the movement in the axial direction is restricted, when the ball nut 29 is driven to rotate, the ball screw 28 is driven in the axial direction, and the crosshead 17 is closed. It is driven in the direction or mold opening direction. A driven pulley 31 is fixed to the ball nut 29, and the driving pulley 32 and the driven pulley 31 provided on the rotation shaft of the servo motor 33 are wound around by a belt 34. The servo motor 33 is connected to the controller 35 by a signal line S1. Therefore, when the servo motor 33 is driven by a command from the controller 35, the ball nut 29 rotates and the cross head 17 can be driven.

  In the toggle type mold clamping apparatus 2 according to the present embodiment, the fixed platen 5 is provided with an acceleration sensor 36 that detects vibration of the fixed platen 5. As the acceleration sensor, an optical type, a semiconductor type, a mechanical type, and the like are well known, and any type of acceleration sensor can be adopted. However, in this embodiment, a semiconductor type is used. A capacitance type acceleration sensor 36 belonging to the type is provided. Since the acceleration sensor 36 is connected to the controller 35 by the signal line S2, the vibration acceleration detected by the acceleration sensor 36, that is, the vibration acceleration of the stationary platen 5, is input to the controller 35.

  The operation of the toggle type mold clamping apparatus 2 according to the present embodiment will be described. In the mold open state, that is, in the state where the movable mold 12 is separated from the fixed mold 11, the crosshead 17 is located on the left side in FIG. 1 and the toggle mechanism 10 is folded. Perform the mold clamping process. A command is output from the controller 35 to drive the servo motor 33. Then, the ball nut 29 rotates and the ball screw 28 is driven in the axial direction, and the crosshead 17 is driven rightward in FIG. When the cross head 17 is driven to the right, the toggle mechanism 10 is expanded and the movable platen 8 is driven to the right. As the position of the cross head 17 moves to the right, the mold opening amounts of the movable mold 12 and the fixed mold 11 are reduced. When the cross head 17 is further driven, the movable mold 12 touches the fixed mold 11. That is, the fixed mold 11 and the movable mold 12 are closed. When the crosshead 17 is continuously driven to the right, the tie bars 7, 7,... Are elastically stretched and tension is applied to the tie bars 7, 7,..., And the movable mold 12 and the fixed mold 11 are moved with a predetermined clamping force. Clamped.

  The graph of FIG. 2 shows changes in the amplitude of vibration of the fixed platen 5 or the acceleration of vibration of the fixed platen 5 at each position of the crosshead 17. Until the movable mold 12 touches the fixed mold 11, the stationary platen 5 hardly vibrates as indicated by reference numeral 41. However, when the movable mold 12 touches the fixed mold 11, the momentum of the movable mold 12 and the movable platen 8 is transmitted to the fixed mold 11 and the fixed platen 5. As shown, the fixed platen 5 vibrates greatly. In the graph, the position of the crosshead 17 when the movable mold 12 touches the fixed mold 11 is indicated by reference numeral 43.

  In the toggle type mold clamping apparatus 2 according to the present embodiment, the vibration of the stationary platen 5 is monitored when the mold opening amount of the movable mold 12 and the stationary mold 11 is within a predetermined range in the mold clamping process. To do. Specifically, in the mold clamping process, monitoring is started when the movable mold 12 and the fixed mold 11 are narrowed to a predetermined mold opening amount, immediately before the movable mold 12 and the fixed mold 11 are touched. Stop monitoring. In the graph of FIG. 2, the position of the crosshead 17 corresponding to the mold opening amount at which monitoring is started is indicated by reference numeral 42. That is, the vibration of the stationary platen 5 is monitored when the position of the crosshead 17 is in a so-called monitoring range indicated by a range from 42 to 43. As shown in FIG. 1, when a foreign object 38 is sandwiched between the movable mold 12 and the fixed mold 11, the movable mold as indicated by reference numeral 46 in the graph of FIG. 2. Since 12 touches the fixed mold 11 via the foreign substance 38, the fixed platen 5 vibrates with a predetermined amplitude. The acceleration sensor 36 measures this. When the measured vibration amplitude or vibration acceleration is larger than a threshold value set in advance in the controller 35, it is determined that a foreign object is caught between the fixed mold 11 and the movable mold 12, and the controller 35 stops the servo motor 33. That is, the driving of the cross head 17 is stopped and the mold clamping process is stopped. Thereby, the fixed mold 11 and the movable mold 12 are not damaged and are protected.

  The toggle type mold clamping device 2 according to the present embodiment can be variously modified. For example, although the acceleration sensor 36 is described as being provided on the stationary platen 5, the acceleration sensor 36 can be similarly implemented even if it is provided on the stationary mold 11. Further, although it has been described that the mold clamping process is stopped when vibration with acceleration greater than a predetermined threshold is detected, acceleration greater than the predetermined threshold continues for a predetermined time width. The mold clamping process may be stopped. If implemented in this way, noise can be picked up and it is possible to prevent the mold clamping process from stopping even though no foreign matter is caught in the mold.

  The mold protecting method in the toggle type mold clamping apparatus according to the present embodiment can be similarly implemented in the direct pressure type mold clamping apparatus. That is, in a direct pressure type mold clamping device, an acceleration sensor is provided on a fixed plate or a fixed mold attached to the fixed plate, and the fixed plate or fixed die detected from a predetermined mold opening position to a mold closing position. If the vibration of the mold is monitored, it is possible to protect the mold by detecting that a foreign object has been caught in the mold.

DESCRIPTION OF SYMBOLS 1 Injection molding machine 2 Toggle type clamping device 3 Injection device 5 Fixed plate 6 Clamp housing 7 Tie bar 8 Movable plate 10 Toggle mechanism 11 Fixed die 12 Movable die 17 Crosshead 28 Ball screw 36 Acceleration sensor 35 Controller

Claims (5)

A stationary platen to which a fixed mold is attached; a movable platen to which a movable die is attached; a mold clamping housing; and a plurality of tie bars penetrating the movable plate and connecting the stationary platen and the mold clamping housing; In a mold comprising a toggle mechanism provided between the movable platen and a mold clamping housing, and capable of opening and closing the mold by driving a crosshead of the toggle mechanism,
When the movable mold is closed with respect to the fixed mold and clamped with a predetermined clamping force, the movable mold is moved from a mold opening position where the movable mold is separated from the fixed mold by a predetermined amount. The vibration of the fixed platen or the fixed mold is monitored until the mold closing position where the fixed mold touches the fixed mold, and when the vibration of the acceleration exceeding the predetermined threshold is detected, the mold closing operation is stopped. Mold protection method. 2. The mold protection method according to claim 1, wherein the mold open position and the mold close position are determined based on a position of the crosshead. 3. The protection method according to claim 1, wherein the vibration is monitored by an acceleration sensor provided on the fixed platen or the fixed mold. A stationary platen to which a fixed mold is attached; a movable platen to which a movable die is attached; a mold clamping housing; and a plurality of tie bars penetrating the movable plate and connecting the stationary platen and the mold clamping housing; In a toggle type mold clamping device comprising a toggle mechanism provided between the movable plate and a mold clamping housing, and configured to be opened and closed when a crosshead of the toggle mechanism is driven,
The fixed plate or the fixed mold is provided with an acceleration sensor, and the acceleration of the fixed plate or the fixed mold measured by the acceleration sensor is input to a controller that controls the toggle mechanism. And
In the mold clamping process in which the movable mold is closed with respect to the fixed mold and clamped with a predetermined clamping force, the movable mold is moved from the predetermined mold opening position to the fixed mold. A toggle that stops the mold clamping process in response to a command from the controller when an acceleration exceeding a predetermined threshold value is detected while being driven to the mold closing position to be touched. Type mold clamping device. An electric injection molding machine provided with the toggle type clamping apparatus according to claim 4.

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