JP2008049674A - Control method for mold clamping device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control method for a mold clamping device which can automatically or easily judge a mold touch and can easily set a low pressure mold clamping force even not by a skilled operator. <P>SOLUTION: A low pressure mold clamping force is applied to a movable mold 11b to move toward a fixed mold 11b, thereby performing mold closing. A larger mold clamping force than a low pressure mold clamping force is applied to the movable mold 11b at the position where the movable mold 11b approaches the fixed mold 11a, thereby performing the mold clamping. A set value of the low pressure mold clamping force is obtained based on a correlation between a value of the low pressure mold clamping force and a position where the movable mold 11b is stopped when the low pressure molding force is applied to the movable mold 11b to move toward the fixed mold 11a. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for controlling a mold clamping device, and more particularly to a method for controlling a mold clamping device for setting a mold clamping force in a mold closing process of an injection molding machine.

  In a molding machine such as an injection molding machine, a resin heated and melted in a heating cylinder is injected and filled into a cavity space of a mold apparatus at a high pressure. The resin filled in the cavity space is cooled and solidified to form a molded product. The mold apparatus generally includes a fixed mold and a movable mold, and the mold closing, mold clamping, and mold opening are performed by moving the movable mold forward and backward with respect to the fixed mold by the mold clamping apparatus. . The mold clamping device includes a fixed platen to which a fixed mold is attached, a movable platen to which a movable mold is attached, and a moving mechanism for moving the movable platen back and forth. That is, the mold device is closed, clamped and opened by driving a moving mechanism such as a toggle mechanism to move the movable platen toward or away from the fixed platen.

  In the mold clamping apparatus as described above, the movable platen is moved from the state where the mold is opened to the maximum (the mold opening limit position), the movable mold is moved (mold closing step), and the fixed mold is brought into contact ( Type touch). Thereafter, a desired mold clamping force is generated by further pressing the movable mold against the fixed mold (a mold clamping step).

  In the mold closing process, the mold is in an open state, and the force applied to move the movable platen is small, but a certain amount of force is applied to quickly move the movable platen to the mold touch state, and the movable platen is moved. Need to increase speed. However, if the movable mold comes into contact with the fixed mold at a high speed, it will cause a large impact. Therefore, the moving platen will be moved at a low speed before it comes into contact, and the movable mold is moved closer to the fixed mold. Make contact. At this time, the force applied to move the movable platen at a small speed is generally referred to as “low pressure clamping force”.

  When the movable platen is moved by the low-pressure mold clamping force and the movable mold comes into contact with the fixed mold, a large force is applied to the movable platen in order to apply the mold clamping force to the mold. The force applied to the movable platen at this time is generally referred to as “clamping force”. When the movable platen is moved by the toggle mechanism to generate the clamping force, the movable mold is accelerated by applying the clamping force to the movable platen slightly before the movable mold contacts the fixed mold. In some cases, the fixed platen may be brought into contact. The position where the mold clamping force starts to be applied is generally referred to as a “mold protection position”.

  The low-pressure mold clamping force described above is preferably as small as possible so that the impact during mold touching is small. However, it is necessary to apply a force that does not lose the sliding resistance of the movable platen. Also, sliding resistance may occur when the positioning pins provided on the mold are fitted before the mold touch. Further, even in the case of a compression molding die as shown in FIG. 1, since the weir member 3 of the fixed die 1 contacts the movable die 2 before touching the die, a force that opposes the low pressure clamping force. Occurs.

  Thus, depending on the mold, a force that opposes the low-pressure mold clamping force acts near the mold touch. Therefore, if the low-pressure mold clamping force is too small, the movable platen stops before touching the mold. Therefore, the set value of the low-pressure mold clamping force needs to be obtained for each mold, but the work for obtaining the set value of the low-pressure mold clamp force often depends on the experience and judgment of a skilled operator.

Here, it is proposed that mold closing force is detected a plurality of times, an adjustment value corresponding to an average value and a standard deviation of detection values is obtained, and a threshold value is obtained from the average value and the adjustment value (for example, Patent Document 1). reference).
JP 2004-330529 A

  The adjustment of the mold closing force described in Patent Document 1 described above is to obtain a threshold value of the mold closing force by taking statistics of the mold closing force (corresponding to the low pressure mold clamping force) detected in advance, and the mold touch is performed. The low pressure mold clamping force is still determined and set by the operator.

  The present invention has been made in view of the above-described problems, and can determine a mold touch automatically or easily, so that a low-pressure mold clamping force can be easily set even by an unskilled operator. An object of the present invention is to provide a method for controlling a mold clamping device.

  In order to achieve the above-described object, according to the present invention, the movable mold is closed by applying a low-pressure mold clamping force and moving the movable mold toward the fixed mold, and the movable mold is the fixed mold. A method of controlling a mold clamping device for performing mold clamping by applying a mold clamping force larger than the low pressure mold clamping force to the movable mold at a position close to the low pressure mold clamping force, and a value of the low pressure mold clamping force and the low pressure mold clamping force A setting value of the low-pressure mold clamping force is obtained based on a correlation with a position where the movable mold stops when a force is applied to the movable mold and moved toward the fixed mold. A method for controlling the mold clamping apparatus is provided.

  In the mold clamping device control method according to the present invention, it is preferable to determine that the movable mold and the fixed mold are in contact with each other at a position corresponding to an inflection point that appears when the correlation is represented in a graph. Further, the correlation may be obtained by detecting the stop position of the movable mold by sequentially changing the value of the low-pressure mold clamping force when performing one mold closing process. Alternatively, the correlation may be obtained by detecting the stop position of the movable mold by closing the mold for each value while changing the value of the low pressure mold clamping force stepwise. Further, it is preferable to change the value of the low-pressure mold clamping force at least three times. Further, the correlation may be a relationship between a detection value of a mold clamping force sensor and a position where the movable mold is stopped. Further, a value obtained by adding a predetermined value to the value of the low pressure mold clamping force corresponding to the inflection point may be set as the set value of the low pressure mold clamping force.

  According to the present invention, it is possible to automatically or easily determine the mold touch based on the correlation between the low-pressure mold clamping force and the stop position of the movable mold, and it is easy even without a skilled operator. Low pressure clamping force can be set.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 2 is a schematic view of a mold clamping device of an injection molding machine in which a control method according to an embodiment of the present invention is executed.

  In FIG. 2, the mold clamping device 10 of the injection molding machine is movable with respect to the frame 17 with a predetermined distance between the frame 17, the fixed platen 12 fixed to the frame 17, and the fixed platen 12. And a toggle support 15 disposed. A plurality of (for example, four) tie bars 16 extend between the fixed platen 12 and the toggle support 15.

  The movable platen 13 is disposed so as to face the fixed platen 12, and is disposed so as to be capable of moving forward and backward (moving in the left-right direction in the drawing) along the tie bar 16. The mold apparatus 11 includes a fixed mold 11a and a movable mold 11b. The fixed mold 11 a is attached to a mold mounting surface of the fixed platen 12 that faces the movable platen 13. On the other hand, the movable mold 11 b is attached to a mold attachment surface of the movable platen 13 that faces the fixed platen 12.

  Note that a drive device for moving an ejector pin (not shown) may be attached to the rear end (left end in the figure) of the movable platen 13.

  A toggle mechanism 20 as a toggle type mold clamping device is attached between the movable platen 13 and the toggle support 15. A mold clamping motor 26 for operating the toggle mechanism 20 is disposed at the rear end of the toggle support 15. The mold clamping motor 26 is provided with a motion direction conversion device (not shown) composed of a ball screw mechanism or the like that converts a rotational motion into a reciprocating motion. The mechanism 20 can be activated. The mold clamping motor 26 is preferably a servo motor, and includes a mold opening / closing position sensor 27 as an encoder for detecting the number of rotations.

  The toggle mechanism 20 includes a cross head 24 attached to the drive shaft 25, a second toggle lever 23 attached to the cross head 24 so as to be swingable, a first toggle lever 21 attached to the toggle support 15 so as to be swingable, A toggle arm 22 is swingably attached to the movable platen 13. Between the first toggle lever 21 and the second toggle lever 23 and between the first toggle lever 21 and the toggle arm 22 are linked. The toggle mechanism 20 is a so-called inner volume five-node double toggle mechanism, and has a vertically symmetrical configuration.

  The toggle mechanism 20 can be operated by driving the mold clamping motor 26 and advancing and retracting the cross head 24 as a driven member. In this case, when the cross head 24 is moved forward (moved in the right direction in the figure), the movable platen 13 is moved forward to perform mold closing. Then, a mold clamping force obtained by multiplying the propulsive force of the mold clamping motor 26 by the toggle magnification is generated, and the mold clamping is performed by the mold clamping force.

  In order to adjust the position of the toggle support 15 with respect to the fixed platen 12, a mold clamping position adjusting device 35 is disposed at the rear end (left end in the figure) of the toggle support 15. The toggle support 15 is formed with a plurality of, for example, four tie bar insertion holes (not shown), and the left end of the tie bar 16 in the figure is inserted into each tie bar insertion hole. The right end of the tie bar 16 is fixed to the fixed platen 12 by a fixing nut 16a.

  The tie bar 16 has a screw portion 36 formed with a screw on the outer periphery at the left end in the figure, and an adjustment nut 37 is screwed to the screw portion 36 of each tie bar 16. The adjustment nut 37 is attached to the rear end of the toggle support 15 so as to be rotatable and immovable in the axial direction of the tie bar 16. A driven gear 37 a is attached to the outer periphery of the adjustment nut 37.

  A mold thickness motor 31 as a mold clamping position adjusting drive source is disposed at an upper portion of the rear end of the toggle support 15. A driving gear 33 is attached to the rotation shaft of the mold thickness motor 31. Around the driven gear 37a and the driving gear 33 of the adjustment nut 37, a driving linear body 34 such as a chain or a toothed belt is wound around. Therefore, when the mold thickness motor 31 is driven and the driving gear 33 is rotated, the adjustment nuts 37 screwed into the screw portions 36 of the tie bars 16 are rotated in synchronization. Thereby, the mold thickness motor 31 can be rotated by a predetermined number of rotations in a predetermined direction, and the toggle support 15 can be advanced and retracted by a predetermined distance. The mold thickness motor 31 is preferably a servo motor, and includes a mold clamping position sensor 32 as an encoder that detects the number of rotations.

  The means for transmitting the rotation of the mold thickness motor 31 to the adjusting nut 37 may be any means as long as the adjusting nut 37 screwed into the screw portion 36 of each tie bar 16 can be rotated synchronously. Good. For example, instead of the driving linear body 34, a large-diameter gear that meshes with all of the driving gear 33 and the driving gear 33 may be rotatably disposed at the rear end of the toggle support 15.

  In the present embodiment, a mold clamping force sensor 18 is disposed on one of the tie bars 16. The mold clamping force sensor 18 is a sensor that detects distortion (mainly elongation) of the tie bar 16. The tie bar 16 is applied with a tensile force corresponding to the mold clamping force during mold clamping, and extends slightly in proportion to the mold clamping force. Therefore, the mold clamping force actually applied to the mold apparatus 11 can be known by detecting the extension amount of the tie bar 16 by the mold clamping force sensor 18.

  The above-described mold clamping force sensor 18, mold opening / closing position sensor 27, mold clamping motor 26 and mold thickness motor 31 are connected to the control device 19, and the detection signals output from the mold clamping force sensor 18 and the mold opening / closing position sensor 27 are controlled. Sent to device 19. The control device 19 controls the operations of the mold clamping motor 26 and the mold thickness motor 31 based on the detection signal.

  Here, an operation during normal molding will be described. When the mold clamping motor 26 is driven in the forward direction, the ball screw shaft 25 is rotated in the forward direction, and the ball screw shaft 25 is moved forward (moved in the right direction in FIG. 1) as shown in FIG. Accordingly, when the cross head 24 is advanced and the toggle mechanism 20 is operated, the movable platen 13 is advanced (mold closing process).

  When the movable mold 11b attached to the movable platen 13 comes into contact with the fixed mold 11a (mold closed state or mold touch), the mold clamping process is started. In the mold clamping process, the mold clamping force is generated in the mold 11 by the toggle mechanism 20 by further driving the mold clamping motor 26 in the forward direction.

  And the injection drive part provided in the injection apparatus which is not shown in figure is driven, and a screw advances, The molten resin is filled in the cavity space formed in the metal mold | die 11. FIG. When performing mold opening, when the mold clamping motor 26 is driven in the reverse direction, the ball screw shaft 25 is rotated in the reverse direction. Accordingly, when the cross head 24 is retracted and the toggle mechanism 20 is operated, the movable platen 13 is retracted.

  When the mold opening process is completed, the ejector driving unit (not shown) is driven, and the ejector device attached to the movable platen is activated. Thereby, an ejector pin protrudes and the molded article in the movable mold 11b protrudes from the movable mold 11b. Simultaneously with the drive of the ejector drive unit, a molded product take-out machine (not shown) is driven, and the arm of the molded product take-out machine enters between the fixed mold 11a and the movable mold 11b, and at the molded product take-out position. Stop. And the molded product protruded from the movable mold 11b by the advance of the ejector pin is held and taken out by the arm of the molded product take-out machine, and is conveyed to a conveyor device as a conveying means provided outside the injection molding machine. .

  By the way, the mold clamping force generated by the toggle mechanism 20 is the spring constant of the entire mold clamping device 10 including the fixed platen 12, the toggle support 15 and the tie bar 16, that is, as in the mold clamping device using a general toggle mechanism. The mold clamping rigidity changes as a proportional constant. In the mold clamping device 10, since the rigidity of the tie bar 16 is lower than that of other members, it can be considered that the mold clamping rigidity is equal to the rigidity of the tie bar 16. Therefore, the mold clamping force generated by the toggle mechanism 20 uses the spring constant as the rigidity of the tie bar 16 as a proportional constant, and the toggle support 15 moves relative to the fixed platen 12 from the mold closing of the mold apparatus 11 to the completion of the mold clamping. It can be said that it changes in proportion to the amount to be done. That is, since the rigidity of the members such as the fixed platen 12 and the toggle support 15 is sufficiently high, the mold clamping force generated by the mold clamping device 10 is substantially generated by elastically deforming and extending the four tie bars 16. It can be said that it is proportional to the amount of elongation of the tie bar 16.

  Next, the relationship between the motor torque generated by the mold clamping motor 26 that drives the mold clamping apparatus and the position of the movable platen 13 (that is, the movable mold 11b of the mold apparatus 11) will be described with reference to FIG. To do. FIG. 3 is a graph showing the relationship between the motor torque of the mold clamping motor 26 and the position of the movable platen 13.

  In FIG. 3, the position where the movable platen 13 connected to the toggle mechanism 20 by the operation of the mold clamping motor 26 is most attracted to the toggle support 15 side is the “die opening limit position”, and the movable mold 11b is located at this position. Stops in the state farthest from the fixed mold 11b.

  When the mold clamping motor 26 is driven from the “mold open limit position” to start the movable platen moving forward (moving in a direction approaching the fixed platen), the motor torque of the mold clamping motor 26 peaks due to a torque increase at the time of startup. The state moves to a stable moving speed through the state A and becomes a substantially constant state B.

  When the movable platen 13 advances in a state where the torque is constant and the movable platen 13 approaches the fixed platen 12 to some extent (that is, the position where the movable mold 11b approaches the fixed mold 11a to some extent), the mold clamping motor 26 is started and the torque of the mold clamping motor 26 is controlled to be in a predetermined low torque state C. This motor torque limit start position corresponds to the “low pressure mold clamping start position”. The motor torque is limited so that when the movable mold 11b approaches the fixed mold 11a to some extent, it is provided so as to advance at a low torque and a low speed. For example, a foreign object may move between the movable mold 11b and the fixed mold 11a. This is a restriction provided for advancing the movable mold 11b with a small force that does not damage the mold even if it is sandwiched between them.

  The position immediately before the movable platen 13 further advances from the “low-pressure mold clamping start position” and the movable mold 11b comes into contact with the fixed mold (mold touch) (for example, a position 0.1 mm before the “mold touch position”). Becomes the “pressure increase start position”. At the “pressurization start position”, the output restriction of the mold clamping motor 26 is released, and the movable platen 13 advances toward the fixed platen 12 at full speed. That is, it is possible to move forward with the maximum thrust. Therefore, when the “pressure increase start position” is passed, the movable platen 13 reaches the “type touch position” while the torque rapidly increases (state D). The “pressurization start position” corresponds to the so-called start-up start position for generating the mold clamping force, and if the output restriction is canceled at the “mold touch position”, the torque of the mold clamping motor 26 cannot be quickly increased. This is a position for starting the torque increase slightly before the “type touch position”. However, if the distance from the “pressurization start position” to the “die touch position” is too large, the movable die 11b is brought into contact (collision) with the fixed die 11a while being accelerated more than necessary. 11 may be damaged. Therefore, the mold apparatus is protected by providing only a small running distance. In this sense, the “pressure increase start position” is also referred to as “mold protection position”.

  At the “die touch position”, the movable mold 11b abuts against the fixed mold 11a and the movable platen 13 cannot move forward, but the torque limitation of the mold clamping motor 26 is released, so the torque continues to rise. As a result, a mold clamping force corresponding to the torque of the mold clamping motor 26 is applied to the mold apparatus 11. Accordingly, the mold clamping force rapidly rises from the “mold touch position”, and when the preset mold clamping force is reached, the mold clamping motor 26 is stopped and the set mold clamping force is maintained. The position where the mold clamping force reaches the set mold clamping force is the “position of the set mold clamping force” and is set as the origin of the fixed platen 13.

  Generally, each of the above-described positions is represented by a distance (for example, millimeters) from the origin with the “position of the set clamping force” as the origin. For example, if the distance from the origin to the “mold touch position” is 3 mm, the distance from the origin to the “mold protection position” is set to 3.1 mm, for example.

  Here, the change in the set value of the mold clamping force between the mold closing process and the mold clamping process will be described with reference to FIG. FIG. 4 is a graph showing changes in the set value of the mold clamping force from the mold closing process to the mold clamping process.

  When the movable platen is moved from the mold open limit position, the mold clamping force (that is, the torque generated by the mold clamping motor 26) is set to a value that can move the movable platen 13 at a predetermined speed. The This set value is referred to as a first mold clamping force or a mold closing force. When the movable platen 13 moves to approach the mold touch position and reaches the low pressure mold clamping start position, the value of the mold clamping force is set to a value smaller than the first mold clamping force. This set value is referred to as a low pressure mold clamping force.

  When the movable platen 13 is driven by the low-pressure mold clamping force and further advances at a low speed and reaches a pressure increase start position (for example, a position 0.1 mm before the mold touch position) that is a position retracted by a predetermined distance from the mold touch position. The value of the mold clamping force is set to a large value so that a clamping force to be applied to the mold apparatus 11 at the time of molding can be obtained. This set value is referred to as a second mold clamping force.

  Here, the setting of the low pressure mold clamping force will be described. As described above, the low-pressure mold clamping start position is a position where the value of the mold clamping force is set to the low-pressure mold clamping force, and is, for example, about 1.5 to 2 times the thickness of the molded product molded by the mold apparatus 11. Is set to a position retracted from the die touch position by a distance of. Further, the pressure increase start position at which the value of the mold clamping force is set to the second mold clamping force is also set to a position retracted by a predetermined distance (for example, 0.1 mm) from the mold touch position. Therefore, it is necessary to detect and set the mold touch position with high accuracy.

  The mold touch position is set as a position when the operator visually observes the mold apparatus 11 and the operator determines that there is no gap between the movable mold 11b and the fixed mold 11a. It was. Therefore, the determination of the type touch position is based on the operator's determination, and it is not a quantitative determination and cannot be automatically determined.

  Therefore, in the method of controlling the mold clamping device according to the present invention, the mold touch position can be easily detected and used for the control, the mold touch can be reliably obtained, and an appropriate low pressure mold clamping force that is not too large. Can be set easily.

  When the inventor closes the mold while gradually increasing the low-pressure mold clamping force from zero, the stop position of the movable platen (movable mold) approaches the mold touch position, and reaches the vicinity of the mold touch position. It has been noted that the stop position becomes almost constant even after the low-pressure mold clamping force is further increased after the size becomes movable.

  FIG. 5 is a graph showing a correlation between the magnitude of the mold clamping force (specifically, the mold clamping force setting value) and the stop position of the movable mold. The graph of FIG. 5 shows that the mold clamping force is started from zero, the mold is closed while increasing the second mold clamping force (or the maximum mold clamping force) by 5%, and the movable platen is applied each time for each value of the mold clamping force. The stop position of (movable mold) is read from the screen display of the operation screen of the molding machine and graphed. In the example shown in FIG. 5, when the mold clamping force is set to zero, the mold stop position is 13.18 mm, and when the mold clamping force is set to 5% of the second mold clamping force, the mold stop position is It was 11.92 mm. Thus, when the mold clamping force is increased by 5%, when the mold clamping force becomes 20% of the second mold clamping force, the mold stop position becomes 0.88 mm, and thereafter the mold clamping force. The mold stop position became almost constant even when the value was increased.

  As can be seen from the graph of FIG. 5, an inflection point appears in the graph representing the correlation between the value of the mold clamping force and the mold stop position. That is, when the value of the mold clamping force is small, the movable platen cannot be moved to a position where it comes into contact with the fixed mold due to the sliding resistance of the movable platen described above, and the movable platen stops halfway. As the mold clamping force increases, the mold stop position approaches the position where the movable mold contacts the fixed mold, but when the mold clamping force exceeds a certain value, the mold stops further. Stop position will not change. This position corresponds to an inflection point on the graph, and it can be determined that the movable mold is in contact with the fixed mold. Therefore, if the value of the mold clamping force corresponding to the inflection point is set as the low pressure mold clamping force, the movable mold can be reliably brought into contact with the fixed mold.

  However, in the example shown in FIG. 5, the mold clamping force is increased stepwise every 5% of the second mold clamping force, and the accuracy is not so good. Therefore, in order to investigate the vicinity of the inflection point with higher accuracy, the value of the clamping force is stepped by 1% in a range of ± 5% (that is, 15% -25%) corresponding to the inflection point. The mold stop position was obtained while making it larger. FIG. 6 shows the correlation between the magnitude of the mold clamping force and the stop position of the movable mold, obtained as described above.

  As can be seen from the graph of FIG. 6, even when the value of the mold clamping force was increased stepwise by 1%, an inflection point appeared when the mold clamping force was 16%. This inflection point indicates the position where the movable mold is in contact with the fixed mold, similarly to the inflection point in the graph of FIG. Therefore, if a value of 16% of the second mold clamping force is set as the low pressure mold clamping force, the movable mold can be surely brought into contact with the fixed mold, but due to thermal expansion of the fixed platen, tie bar or the like. Considering the change (increase) in sliding resistance, safety is anticipated, and a value larger by a predetermined value is set as the low pressure clamping force. As a result of investigation by the present inventor, by adding 5% of the second mold clamping force to the value of the mold clamping force obtained from the inflection point of the graph, it is possible to reliably move the movable mold even if the sliding resistance fluctuates. It was found that can be brought into contact with the fixed mold. That is, in the case of the example shown in FIG. 6, 21% obtained by adding 5% which is a predetermined value to 16% corresponding to the inflection point is a value set as the low pressure clamping force.

  After setting the low-pressure mold clamping force to 21% of the second mold clamping force, the mold is closed and the mold stop position is obtained. This stop position becomes the mold touch position. In view of thermal expansion of the mold, a value obtained by adding 0.05 mm to 0.1 mm to the obtained mold touch position is set as the pressure increase start position (in FIG. 4, the mold touch position). The pressure increase start position is set by adding 0.1 mm to the touch position).

  As described above, if the graph representing the correlation between the value of the mold clamping force and the mold stop position is displayed on, for example, the operation input display device of the molding machine, the operator confirms the inflection point, The value of the mold clamping force with which mold contact can be reliably obtained can be known, and that value can be set as the low pressure mold clamping force. Further, the mold touch position can be obtained by performing mold closing using the low-pressure mold clamping force set as described above.

  Increasing the mold clamping force stepwise may be performed in a single mold closing process, or may be performed once every time the mold clamping force value is increased by one stage. . To increase the mold clamping force step by step in a single mold closing process, when the mold stoppage is confirmed with the mold clamping force value set to zero, the mold clamping force value is increased by one step. If the mold stop is confirmed again, the mold clamping force value may be set to a value larger by one step and the mold closing may be continued.

  Moreover, the above-mentioned inflection point can be found by setting the number of times of increasing the mold clamping force stepwise to at least three times. In addition, the mold can be prevented from being damaged by increasing the value in order from a small set value.

  Furthermore, instead of the set value of the mold clamping force, the detected value of the mold clamping force sensor may be used in the correlation shown in FIG. In this case, by using the detection value of the mold clamping force sensor, it is possible to detect the force actually applied to the mold without receiving a change with time such as expansion and contraction of parts due to a change in ambient temperature. Therefore, when the mold clamping device is set again with the same mold, the mold stop position can be accurately obtained in a short time by adjusting the same mold clamping force as that of the previous time.

  Next, a method for setting the low-pressure mold clamping force without using a graph as described above will be described with reference to FIG. FIG. 7 is a flowchart of the low-pressure mold clamping force setting process. Here, as in the example shown in FIG. 5, the mold contact is judged while increasing the mold clamping force stepwise by 5%, and the low pressure mold clamping is performed based on the value of the mold clamping force set at that time. Set the force. In addition, each time the mold clamping force is increased by one step, the mold closing process is performed once.

  First, in step S1, the position of the movable platen when the second mold clamping force is applied to the mold is set to zero as the origin. This setting can be performed, for example, via an operation input display device of an injection molding machine. Next, in step S2, the value of the low-pressure mold clamping force is set to zero, and the mold is closed in step S3. Subsequently, a mold stop position is detected in step S4. Since the mold stop position is normally displayed on the operation input display device of the injection molding machine, the value of the displayed mold stop position may be read.

  Next, in step S5, the mold is opened. Subsequently, in step S6, the value of the low pressure mold clamping force is increased by 5% of the second mold clamping force, and then the mold is closed. In step S7, the mold stop position is detected in the same manner as in step S4.

  In step S8, it is determined whether or not the mold stop position has advanced by 0.1 mm or more (approached to the origin) from the previous mold stop position. If the mold stop position has advanced by 0.1 mm or more from the previous mold stop position, the process returns to step S5 to continue the process. If the mold stop position has not advanced more than 0.1 mm from the previous mold stop position, the process proceeds to step S9. In step S9, a value obtained by adding a predetermined value (5% of the second mold clamping force in the above example) to the value of the low pressure mold clamping force set immediately before is set as the low pressure mold clamping force to be used thereafter. The process ends.

  As described above, according to the present embodiment, the mold is closed by applying a low-pressure mold clamping force to the movable platen (movable mold) and moving the movable platen toward the fixed mold, and the movable mold becomes the fixed mold. In a control method of a mold clamping device that performs mold clamping by applying a mold clamping force larger than the low-pressure mold clamping force to the movable mold at a close position, the value of the low-pressure mold clamping force and the low-pressure mold clamping force are The mold touch can be determined automatically or easily based on the correlation with the position where the movable platen (movable mold) stopped when moved toward the fixed mold in addition to the mold) Even a non-skilled operator can easily set the low pressure clamping force. At that time, it is possible to easily determine that the movable mold and the fixed mold are in contact with each other by expressing the correlation in a graph and obtaining the inflection point.

It is sectional drawing of the metal mold | die for compression molding. It is the schematic of the mold clamping apparatus of the injection molding machine with which the control method by one Embodiment of this invention is performed. It is a graph which shows the relationship between the motor torque of a mold clamping motor, and the position of a movable platen. It is a graph which shows the change of the setting value of the mold clamping force between a mold closing process and a mold clamping process. It is a graph which shows the correlation with the magnitude | size of a mold clamping force, and the stop position of a movable metal mold when the value of a mold clamping force is increased 5% at a time. It is a graph which shows the correlation with the magnitude | size of a mold clamping force, and the stop position of a movable metal mold when the value of a mold clamping force is increased 1% at a time. It is a flowchart of a low pressure mold clamping force setting process.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Mold clamping device 11 Mold apparatus 11a Fixed mold 11b Movable mold 12 Fixed platen 13 Movable platen 15 Toggle support 16 Tie bar 18 Clamping force sensor 19 Controller 20 Toggle mechanism 26 Mold clamping motor 27 Mold opening / closing position sensor 31 Mold thickness Motor 32 mold clamping position sensor

Claims (7)

A mold is closed by applying a low-pressure mold clamping force to the movable mold and moving it toward the fixed mold, and a mold clamping force larger than the low-pressure mold clamping force at a position where the movable mold is close to the fixed mold. Is a control method of a mold clamping device for performing mold clamping in addition to the movable mold,
Based on the correlation between the value of the low-pressure mold clamping force and the position where the movable mold stops when the low-pressure mold clamping force is applied to the movable mold and moved toward the fixed mold, A control method for a mold clamping device, wherein a set value of the low pressure mold clamping force is obtained. A method for controlling a mold clamping device according to claim 1,
A method for controlling a mold clamping device, comprising: determining that the movable mold and the fixed mold are in contact with each other at a position corresponding to an inflection point that appears when the correlation is represented in a graph. A method for controlling a mold clamping device according to claim 1,
Control of a mold clamping device characterized in that the correlation is obtained by detecting the stop position of the movable mold by sequentially changing the value of the low pressure mold clamping force when performing a single mold closing process. Method. A method for controlling a mold clamping device according to claim 1,
A mold clamping apparatus characterized in that the correlation is obtained by detecting the stop position of the movable mold by closing the mold for each value while changing the value of the low pressure mold clamping force stepwise. Control method. A method for controlling a mold clamping device according to claim 4,
A method for controlling a mold clamping device, wherein the value of the low pressure mold clamping force is changed at least three times. A method for controlling a mold clamping device according to claim 1,
The method for controlling a mold clamping device, wherein the correlation is a relationship between a detection value of a mold clamping force sensor and a position where the movable mold is stopped. A method for controlling a mold clamping device according to claim 2,
A method for controlling a mold clamping device, wherein a value obtained by adding a predetermined value to a value of the low-pressure mold clamping force corresponding to the inflection point is used as the set value of the low-pressure mold clamping force.

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