Injection molding machine and adjustment method

Abstract

To adjust the clamping force of an injection molding machine to a set value in a short time. [Solution] The control device 100 calculates the increase or decrease in mold thickness, which is the thickness of the mold, based on the mold clamping completion position K, which is the reference position of the crosshead 12 set corresponding to a preset set mold clamping force, and the position C of the crosshead 12 when the mold clamping force is applied in the mold clamping process during injection molding, and corrects the position of the mold clamping housing 7 using a first mechanism based on the increase or decrease in mold thickness.

Description

[Technical Field]

[0001] The present disclosure relates to an injection molding machine and a method for adjusting a mold clamping force. [Background technology]

[0002] Japanese Patent No. 5491487 (Patent Document 1) discloses an adjustment method for adjusting the distance between a movable platen and a fixed platen to a preset mold clamping force. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5491487 Summary of the Invention [Problem to be solved by the invention]

[0004] Molds used in injection molding can deform due to temperature, such as when hot resin is repeatedly poured into the mold. If the mold thickness changes due to temperature, the distance between the movable and fixed platens must be adjusted accordingly to achieve the preset clamping force. Adjusting the distance between the movable and fixed platens by trial and error can be a time-consuming process.

[0005] An object of the present disclosure is to adjust the mold clamping force to a set value in an injection molding machine in a short time. [Means for solving the problem]

[0006] An injection molding machine according to a first aspect of the present disclosure relates to an injection molding machine that adjusts the clamping force for clamping a mold to be integrated by moving a movable platen on which a first mold member is attached relative to a fixed platen on which a second mold member is attached. The injection molding machine includes a clamping housing connected to the fixed platen, a first mechanism for adjusting the distance between the clamping housing and the fixed platen, a second mechanism for applying the clamping force to the mold, and a control device. The second mechanism is a toggle mechanism including a rotationally driven screw shaft and a crosshead that moves with the rotation of the screw shaft. The control device calculates an increase or decrease in mold thickness based on a clamping completion position, which is a reference position of the crosshead set corresponding to a preset clamping force, and the position of the crosshead when the clamping force is applied during the clamping process during injection molding, and corrects the position of the clamping housing based on the increase or decrease in mold thickness using the first mechanism.

[0007] An adjustment method according to a second aspect of the present disclosure relates to an injection molding machine that uses a control device to adjust the clamping force used to clamp a mold formed by moving a movable platen, on which a first mold member is attached, relative to a fixed platen, on which a second mold member is attached, to form a single unit. The injection molding machine includes a clamping housing connected to the fixed platen, a first mechanism for adjusting the distance between the clamping housing and the fixed platen, and a second mechanism for applying a clamping force to the mold. The second mechanism is a toggle mechanism including a rotationally driven screw shaft and a crosshead that moves with the rotation of the screw shaft. The adjustment method includes the steps of: calculating an increase or decrease in mold thickness, which is the thickness of the mold, based on a clamping completion position, which is a reference position of the crosshead set corresponding to a preset clamping force, and the position of the crosshead when the clamping force is applied in the clamping step during injection molding; and correcting the position of the clamping housing using the first mechanism based on the increase or decrease in mold thickness. [Effects of the Invention]

[0008] In the injection molding machine and adjustment method according to the present disclosure, the increase or decrease in mold thickness, which is the thickness of the mold, is calculated based on the mold clamping completion position and the position of the crosshead when the clamping force is applied in the mold clamping process during injection molding, and the position of the clamping housing is corrected using the first mechanism based on the increase or decrease in mold thickness. As a result, even if the mold thickness changes, the position of the clamping housing can be automatically corrected in accordance with the changed mold thickness, making it possible to adjust to the set mold clamping force in a short time. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an injection molding machine. [Figure 2] 10 is a flowchart showing control contents. [Figure 3] FIG. 10 is a diagram showing a relationship for determining the amount of reduction in mold thickness. [Figure 4] 10 is a flowchart showing the control content of a mold thickness reducing step. [Figure 5] FIG. 10 is a diagram showing a relationship for determining an increase in mold thickness. [Figure 6] 10A and 10B are diagrams for explaining a case where there is no change in mold thickness and a case where the mold thickness is increased. [Figure 7] 10 is a flowchart showing the control content of a mold thickness increasing step. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0011] (Configuration of injection molding machine) FIG. 1 is a diagram illustrating the configuration of an injection molding machine 1. For ease of explanation, the floor on which the injection molding machine 1 is placed is defined as the XY plane, and the direction perpendicular to the floor is defined as the Z-axis direction. The positive direction of the Z-axis may be referred to as the upper side or upward, and the negative direction as the lower side or downward. The YZ plane view in FIG. 1 is a view of the injection molding machine 1 as seen from the front. Although the injection molding machine 1 is shown as a horizontal injection molding machine, it is not limited to a horizontal type and may be a vertical injection molding machine.

[0012] 1, injection molding machine 1 includes a mold clamping unit 3 for clamping a mold, an injection unit 2 for melting and injecting an injection material, an operation panel 130, a servo amplifier 160, and a control unit 100. In Fig. 1, mold clamping unit 3 is disposed on the negative side of the X-axis relative to injection unit 2.

[0013] The mold clamping device 3 includes a bed 111, a fixed platen 5, a mold clamping housing 7, a movable platen 6, tie bars 9, a mold clamping mechanism 11, a servo motor 16, a geared motor 20, and gears 18 and 19. The bed 111 is placed on the floor surface, and devices such as the fixed platen 5, the mold clamping housing 7, and the movable platen 6 are mounted on the upper surface thereof. The mold clamping mechanism 11 includes a crosshead 12, a ball nut 13, and a ball screw 14.

[0014] The fixed platen 5 is fixed to the end of the bed 111 that is closer to the injection unit 2 (i.e., in the positive direction of the X-axis). The mold clamping housing 7 is disposed at the end of the bed 111 that is in the negative direction of the X-axis. The fixed platen 5 and the mold clamping housing 7 are connected by tie bars 9 that include multiple bars. The mold clamping housing 7 is movable in the X-axis direction on the bed 111.

[0015] The movable platen 6 is disposed on the bed 111 between the fixed platen 5 and the clamping housing 7. The movable platen 6 is configured to be movable in the X-axis direction. The clamping housing 7 and the movable platen 6 are connected by a clamping mechanism 11. The clamping mechanism 11 has a toggle mechanism. The clamping mechanism 11 is provided with a crosshead 12 that drives the clamping mechanism 11. A ball nut 13 is fixed to the crosshead 12. A ball screw 14 is threadedly engaged with the ball nut 13. In the clamping mechanism 11, two links (arms) are driven by the movement of the crosshead 12, and a large output can be obtained from a small input.

[0016] The mold clamping mechanism 11 can move the movable platen 6 in the X-axis direction relative to the mold clamping housing 7 by driving a servo motor 16 arranged in the mold clamping housing 7 to rotate a ball screw 14. Note that a direct acting cylinder driven by hydraulic pressure may also be used as the mold clamping mechanism 11.

[0017] The gear 18 is fixed by a tie bar nut (not shown). The gear 18 is engaged with a gear 19. In the mold clamping unit 3, the tie bar nuts rotate synchronously via the gears 18 and 19 when the geared motor 20 is driven. The mold clamping unit 3 moves the mold clamping housing 7 by the rotation of the tie bar nuts. The mold clamping unit 3 adjusts the distance between the movable platen 6 and the fixed platen 5 by moving the mold clamping housing 7.

[0018] A mold member 23 is disposed on the movable platen 6. A mold member 22 is disposed on the fixed platen 5. The mold member 23 and the mold member 22 are disposed facing each other between the movable platen 6 and the fixed platen 5. By moving the movable platen on which the mold member 23 is attached relative to the fixed platen 5 on which the mold member 22 is attached, an integrated mold is formed.

[0019] By moving the mold member 23 in the X-axis direction using the mold clamping mechanism 11, the mold member 23 can be brought into close contact with the mold member 22 or moved away from the mold member 22. The dimension of the mold when the mold member 23 and the mold member 22 come into contact and become one unit is referred to as the mold thickness. The position where the mold member 23 and the mold member 22 come into contact is referred to as the mold touch position. In the following explanation, the process of transitioning the mold member 23 and the mold member 22 from a spaced-apart state to a close-contact state is referred to as "mold closing." The process of clamping the mold from the closed state with a large force so that the mold does not open due to the injection pressure is referred to as "mold clamping." The process of transitioning the mold member 23 and the mold member 22 from a close-contact state to a spaced-apart state is referred to as "mold opening."

[0020] With mold member 23 and mold member 22 clamped together in the mold clamping process, a molten material (resin) is filled into the mold and cooled to solidify, thereby molding a product of a desired shape. After the product is molded, with mold member 23 separated from mold member 22 in the mold opening process, an ejector device (not shown) arranged on movable platen 6 is operated to eject and remove the molded product (also referred to as a molded product) from mold member 23.

[0021] The injection unit 2 includes a base 121, a heating cylinder 122, a drive unit 124, a hopper 125, an injection moving unit 127, and a temperature sensor 128. The base 121 is placed on the floor surface on the positive side of the X-axis of the bed 111, and the drive unit 124 is mounted on the upper surface thereof. Servo motors 153 and 154 are arranged in the drive unit 124.

[0022] A heating cylinder 122 extending in the X-axis direction is disposed in the driving device 124. The heating cylinder 122 includes a heater (not shown) for heating the interior, a screw 123, and an injection nozzle 126. The screw 123 is driven by a servo motor 153 in the driving device 124 and is configured to be rotatable around the X-axis direction as its rotation axis. The screw 123 is also configured to be movable in the X-axis direction by the servo motor 154. The injection nozzle 126 is disposed at the end of the heating cylinder 122 on the mold clamping device 3 side (i.e., the end in the negative direction of the X-axis). The heating cylinder 122 heats and melts beads of resin material fed from a hopper 125, and kneads the material using the screw 123 to produce a molten material. This process of melting the resin material is referred to as a "plasticization" process.

[0023] The injection moving device 127 is configured, for example, by a mechanism using a hydraulic cylinder or a mechanism using a ball screw, and connects the drive device 124 to the fixed platen 5 of the mold clamping unit 3. When the injection moving device 127 is configured by a mechanism using a ball screw, the injection moving device 127 is driven by the drive device 124 to move the drive device 124 and the heating cylinder 122 in the X-axis direction. The injection moving device 127 brings the injection nozzle 126 into contact with the sprue bushing of the mold member 22 of the mold clamping unit 3, and injects the molten material from the injection nozzle 126, thereby filling the cavity of the mold members 22, 23 (mold). The servo motor 154 applies pressure to the molten material by moving the screw 123 in the heating cylinder 122 in the negative direction of the X-axis, thereby injecting the molten material into the mold and maintaining a constant pressure of the molten material after injection.

[0024] The process of injecting the molten material into the mold members 22 and 23 is called the "injection" process. After the injection process, the process of maintaining the molten material filled in the mold members 22 and 23 at a constant pressure to adjust the amount of shrinkage is called the "holding" process. After the holding process is completed, a cooling process, in which the molten material is left to solidify in the mold, and a plasticization process, in which the material for the next injection is melted, kneaded, and measured, are carried out in parallel.

[0025] Temperature sensors 128 are arranged at several locations (only one is shown in the figure) from the base of the heating cylinder 122 to the injection nozzle 126. The temperature sensor 128 detects the temperature of the heating cylinder 122 and outputs the temperature to the control device 100. The control device 100 controls the heater based on the value detected by the temperature sensor 128 to adjust the heating cylinder 122 to a desired temperature.

[0026] After the cooling and plasticizing processes are completed, the mold opening and ejection processes are carried out, and the molded product is removed. The injection molding machine 1 can continuously form products by cyclically repeating the mold closing process, mold clamping process, injection process, pressure holding process, cooling and plasticizing process, mold opening process, and ejection process.

[0027] A control panel provided on the base 121 houses a control device 100 and a servo amplifier 160 for driving the servo motors 16, 153 to 154. The control device 100 includes a CPU (Central Processing Unit) 101 and a memory 102. The control device 100 acquires detection values ​​from various sensors arranged in the injection molding machine 1 and controls the injection molding machine 1 in an integrated manner.

[0028] The mold clamping unit 3 is provided with a sensor 25 that detects the mold clamping force. The sensor 25 is, for example, a strain sensor, and is disposed on the tie bar 9. The sensor 25 detects elastic deformation of the tie bar 9. The control device 100 calculates the mold clamping force based on a signal from the sensor 25. The control device 100 drives a servo motor 16 that adjusts the mold clamping force.

[0029] The servo motor 16 is provided with a position sensor 26 (for example, an optical encoder) that detects the rotation angle of the servo motor 16. The geared motor 20 is provided with a position sensor 27 (for example, an optical encoder) that detects the rotation angle of the geared motor 20. Detection signals from the position sensors 26 and 27 are output to the control device 100. The control device 100 can detect the position of the crosshead 12 based on the detection signal from the position sensor 26. The control device 100 can detect the position of the mold clamping housing 7 based on the detection signal from the position sensor 27. The control device 100 adjusts the distance between the mold clamping housing 7 and the fixed platen 5 by driving the geared motor 20.

[0030] The mold clamping mechanism 11 is a toggle mechanism that includes a ball screw 14 that is rotationally driven by a servo motor 16, and a crosshead 12 that moves with the rotation of the ball screw 14. The toggle mechanism is a link mechanism in which two links (arms) are driven by the movement of the crosshead 12, and a large output can be obtained from a small input.

[0031] Here, the injection molding machine 1 drives the geared motor 20 of the clamping unit 3 to move the clamping housing 7 to a predetermined position toward the fixed platen 5. With the clamping housing 7 fixed at a predetermined position, the injection molding machine 1 drives the servo motor 16 of the clamping mechanism 11 to move the crosshead 12 to a preset clamping completion position K. As a result, in the injection molding machine 1, the movable platen 6 moves toward the fixed platen 5 so that the movable platen 6 and the fixed platen 5 come into contact with each other, and in this state, a further load is applied to clamp the mold. That is, the "geared motor 20" in this embodiment corresponds to the "first mechanism" in this disclosure. Furthermore, the "clamping mechanism 11" in this embodiment corresponds to the "second mechanism" in this disclosure.

[0032] In the injection molding machine 1, the mold thickness may change during injection molding due to changes in the temperature of the mold, etc. When the mold thickness changes, it is necessary to adjust the distance between the movable platen 6 and the fixed platen 5 in accordance with the change in mold thickness in order to achieve a preset mold clamping force (also referred to as a set mold clamping force). In such a case, in the injection molding machine 1, the position of the mold clamping housing 7 may be corrected in accordance with the change in mold thickness so that the set mold clamping force is applied to the mold when the crosshead 12 moves to the mold clamping completion position K.

[0033] For example, if the mold thickness is reduced from its initial state, the desired set clamping force may not be secured even when the crosshead 12 moves to the clamping completion position K, which could result in leakage of molten material from the mold or the generation of flash. Therefore, in order to secure the set clamping force, it is necessary to reduce the distance between the movable platen 6 and the fixed platen 5 by changing the position of the clamping housing 7. On the other hand, if the mold thickness increases due to thermal expansion or the like, the clamping force will become too large when the crosshead 12 moves to the clamping completion position K. Therefore, from the perspective of machine protection, it is necessary to prevent excessive force from being applied to the mold by increasing the distance between the movable platen 6 and the fixed platen 5 by changing the position of the clamping housing 7 in accordance with the increase in mold thickness.

[0034] Conventionally, such adjustment of the distance between the movable platen 6 and the fixed platen 5 has been performed by an operator by stopping the apparatus each time and performing the adjustment by trial and error, which has taken time and may have led to a decrease in the operating rate. Therefore, in the injection molding machine 1 of the present disclosure, the position of the mold clamping housing 7 is automatically corrected based on the increase or decrease in mold thickness. As a result, even if the mold thickness changes, the injection molding machine 1 can automatically and quickly correct the position of the mold clamping housing 7 in accordance with the changed mold thickness. Therefore, the injection molding machine 1 can ensure the desired mold clamping force and shorten the processing time, thereby improving the operating rate.

[0035] The following describes specific control details of the injection molding machine 1. Fig. 2 is a flowchart showing the control details executed by the control device 100. In Fig. 2, step S (hereinafter simply referred to as "S") 1 determines the initial position of the mold clamping housing 7 and the initial value of the position of the crosshead 12 at the time of mold clamping completion in accordance with the shapes of the mold members 22, 23 when the mold members 22, 23 are attached to the injection molding machine 1.

[0036] On the other hand, the processes of S2 to S13 are processes for adjusting the clamping force while feeding back the clamping force. Of these, the clamping process shown in S3 to S6 is a process for storing, by feedback control of the clamping force, the position of the crosshead 12 corresponding to the change in mold thickness (also referred to as crosshead position C) and the detected clamping force (detected clamping force) when the injection molding machine 1 is driven corresponding to the initial position of the clamping housing 7 and the initial value of the position of the crosshead 12 at the completion of clamping. Furthermore, the mold thickness adjustment process shown in S8 to S12 is a process for correcting, by feedback control of the clamping force, the position of the clamping housing 7 according to the change in mold thickness during the clamping process during injection molding.

[0037] The control device 100 executes a mold thickness decreasing step S10 when the mold thickness decreases, and executes a mold thickness increasing step S12 when the mold thickness increases. In the following description, the position where the crosshead 12 is at its most advanced position in the mold clamping direction (mold closing direction, positive direction of the X-axis), i.e., the position where the link of the toggle mechanism is fully extended, is defined as zero. In this specification, it is expressed that the amount of movement increases when the crosshead 12 moves in the mold opening direction (negative direction of the X-axis). Taking into account errors, etc., the mold clamping completion position K is set to a position in the negative direction of the X-axis (for example, a position with a margin of about 0.3 mm) from the position where the link of the toggle mechanism is fully extended.

[0038] The control device 100 first executes an initial mold thickness adjustment process in step S1. In the initial mold thickness adjustment process, the control device 100 sets an initial position of the mold clamping housing 7 based on the mold thickness input value input by the operator, and stores it in the memory 102. The initial position of the mold clamping housing 7 is determined in advance using a table or the like depending on the type of mold, and is stored in the memory 102.

[0039] Next, the control device 100 starts the mold clamping force adjustment process, which adjusts the mold clamping force applied to the mold through feedback, and moves the crosshead 12 forward to move the movable platen 6 in the mold closing direction (S2). The subsequent processes of S2 to S13 are repeatedly executed while the injection molding machine 1 is in operation. The control device 100 determines whether the detected mold clamping force has reached the set mold clamping force while the crosshead 12 is moving forward in the mold clamping process of each cycle (S3). If the control device 100 determines that the detected mold clamping force has not reached the set mold clamping force (NO in S3), it proceeds to the process of S4. In S4, the control device 100 determines whether the crosshead 12 has reached the mold clamping completion position K, which is the limit position of its movement (S4).

[0040] If the control device 100 determines in S4 that the crosshead 12 has not reached the mold clamping completion position K, which is the limit position of movement (NO in S4), it continues to move the crosshead 12 forward (S5) and returns to the processing of S3. If the results are NO in S3 and NO in S4, the control device 100 moves the crosshead 12 forward because the mold is not in contact or the crosshead 12 has not reached the limit position.

[0041] When the control device 100 determines in S3 that the detected mold clamping force has reached the set mold clamping force (YES in S3), it proceeds to processing in S6. If YES in S3, it indicates that either the mold thickness has not changed and the set mold clamping force has been reached at the mold clamping completion position K, or the mold thickness has increased and the set mold clamping force has been reached before reaching the mold clamping completion position K. In such cases, the control device 100 stops the crosshead 12 from the perspective of machine protection and proceeds to processing in S6.

[0042] When the control device 100 determines that the crosshead 12 has reached the mold clamping completion position K, which is set as the limit position of movement (YES in S4), it proceeds to processing in S6. If the result in S4 is YES, it indicates that the crosshead 12 reached the mold clamping completion position K (the crosshead 12 is in a fully extended position) before the detected mold clamping force became the set mold clamping force due to a decrease in mold thickness. In such a case, the control device 100 stops the crosshead 12 because the crosshead 12 cannot move any further due to the decrease in mold thickness, and proceeds to processing in S6.

[0043] The control device 100 advances the crosshead 12 in the mold clamping process by repeating the processes of S3 to S5 until S3 becomes YES or S4 becomes YES. When the mold clamping operation is completed, in S6, the control device 100 stores the crosshead position C, which is the position of the crosshead 12 when S3 becomes YES or S4 becomes YES (when the crosshead 12 has stopped), and the detected mold clamping force at crosshead position C in the memory 102. This allows the control device 100 to store the crosshead position C corresponding to the mold thickness and the detected mold clamping force detected at crosshead position C.

[0044] Next, the control device 100 drives the servo motor 16 to open the mold by a predetermined amount (S7), and operates the ejector device to eject and remove the molded product from the mold members 23 (also referred to as a shot). Between the shot executed this time and the shot executed next, the control device 100 executes the subsequent mold thickness adjustment process using the crosshead position C and the detected mold clamping force stored in S6.

[0045] In the mold thickness adjustment process, the control device 100 determines whether the crosshead position C stored in S6 is equal to or less than the mold clamping completion position K (S8). By the processing of S8, the control device 100 compares the crosshead position C with the mold clamping completion position K that is set in advance.

[0046] If the control device 100 determines in S8 that the crosshead position C is equal to or lower than the mold clamping completion position K (YES in S8), it proceeds to processing in S9. If the result in S8 is YES, that is, if the crosshead position C is equal to or lower than the mold clamping completion position K, this indicates either a case where the mold thickness has not changed and the desired set mold clamping force is achieved at the mold clamping completion position K (i.e., a normal state), or a case where the mold thickness has decreased and the desired set mold clamping force cannot be obtained even when the crosshead 12 has moved in the positive direction of the X axis (the direction in which it fully extends and approaches 0) beyond the mold clamping completion position K.

[0047] In S9, the control device 100 determines whether the detected mold clamping force stored in S6 is within the allowable range of the set mold clamping force (S9). Here, the allowable range of the set mold clamping force is a range of mold clamping force that does not affect injection molding. The range that does not affect injection molding in S9 is a range in which a slight shortage of mold clamping force will not have an effect because the crosshead 12 is in the direction of full extension beyond the mold clamping completion position K. If the control device 100 determines that the detected mold clamping force is within the allowable range of the set mold clamping force (YES in S9), the mold thickness has not changed or the amount of reduction in mold thickness is such that it does not affect injection molding, so the control device proceeds to processing in S13 without adjusting the mold thickness.

[0048] If the control device 100 determines in S9 that the detected mold clamping force is outside the allowable range of the set mold clamping force, i.e., that the mold thickness has decreased to such an extent that it will affect injection molding (NO in S9), it executes the mold thickness reduction step of S10 to correct the mold thickness setting. If the result is NO in S9, this means that the mold thickness has decreased, and the mold clamping force is significantly insufficient compared to the set mold clamping force even though the crosshead 12 is in its fully extended position. Thus, if the result is NO in S9, this means that the mold thickness has decreased from the initial value, causing the detected mold clamping force to fall outside the allowable range of the set mold clamping force, and the crosshead position C has moved beyond the mold clamping completion position K.

[0049] The control device 100 calculates the amount of reduction in mold thickness through the processing of S10, and corrects the position of the mold clamping housing 7 using the calculated amount of reduction. By correcting the position of the mold clamping housing 7, mold clamping can be started in the next cycle from the position of the mold clamping housing 7 that corresponds to the reduced mold thickness. By the correction processing of S10, when the crosshead 12 is moved to the mold clamping completion position K in the mold clamping process, the desired set mold clamping force is applied to the mold. The detailed processing of S10 will be described later.

[0050] If the control device 100 determines in S8 that the crosshead position C is greater than the mold clamping completion position K (NO in S8), it proceeds to processing in S11. If the result in S8 is NO, it means that the set mold clamping force is reached before the crosshead 12 reaches the mold clamping completion position K due to an increase in mold thickness, and the crosshead 12 is in the negative direction of the X axis relative to the mold clamping completion position K.

[0051] Next, the control device 100 determines whether the crosshead position C is equal to or less than the allowable position D (S11). Here, the allowable position D indicates the allowable range of the increase in mold thickness. The allowable position D is the range of the increase in mold thickness that does not affect injection molding, and is set on the negative side of the X-axis from the mold clamping completion position K. In other words, as long as the crosshead position C is within the range from the mold clamping completion position K to the allowable position D, no problem will occur. On the other hand, if the crosshead position C is beyond the allowable position D and in the negative side of the X-axis, it means that the mold thickness has increased to an extent that will affect injection molding.

[0052] The allowable position D is set within a range that does not affect the injection molding machine 1, taking into account the load on the geared motor 20. Specifically, when the crosshead position C is greater than the allowable position D, the set clamping force is reached with the arm of the toggle mechanism bent significantly. When the arm is extended, the reaction force of the clamping force is shared by the geared motor 20 and the arm. However, when the arm is bent significantly, the arm cannot share the clamping force, and only the geared motor 20 receives the reaction force of the clamping force. Therefore, when the crosshead position C is greater than the allowable position D, a high load is applied to the geared motor 20, which may cause a malfunction. Therefore, when the control device 100 determines that the crosshead position C is greater than the allowable position D (NO in S11), it executes the mold thickness increasing step in S12 to correct the mold thickness setting.

[0053] The control device 100 calculates the increase in mold thickness by the processing of S12. Then, the control device 100 corrects the position of the mold clamping housing 7 using this increase. By correcting the position of the mold clamping housing 7, mold clamping can be started in the next cycle from the position of the mold clamping housing 7 that corresponds to the increased mold thickness. As a result, when the crosshead 12 is moved to the mold clamping completion position K in the mold clamping process, the desired set mold clamping force is applied to the mold. The detailed processing of S12 will be described later.

[0054] If the control device 100 determines in S11 that the crosshead position C is equal to or less than the allowable position D (YES in S11), it determines that the increase in mold thickness is an amount that will not affect injection molding, and completes the feedback mold clamping force adjustment process (S13). In other words, if the result in S11 is YES, it is determined that although the mold thickness has increased, the bending of the arm of the toggle mechanism is small, and therefore the increase in the load on the geared motor 20 is small.

[0055] Here, the mold thickness decreasing process in S10 and the mold thickness increasing process in S12 can correct the position of the mold clamping housing 7 in a single process using different relationships through the processes shown below. Therefore, the injection molding machine 1 can automatically and quickly correct the position of the mold clamping housing 7 in accordance with the changed mold thickness. This allows the injection molding machine 1 to adjust to the set mold clamping force in a short time.

[0056] First, we will explain the mold thickness reduction step S10. Since the mold clamping step is performed in the elastic deformation region of the tie bars 9, there is a proportional relationship between the position of the movable platen 6 and the mold clamping force, in that the clamping force applied to the mold increases as the movable platen 6 moves in the mold clamping direction from the mold touch position.

[0057] When the mold thickness is reduced, even if the mold clamping process is started from the initial position of the mold clamping housing 7 and the movable platen 6 is moved to the mold clamping completion position K, the actual mold clamping force detected as the detected mold clamping force will not reach the set mold clamping force. This is because the mold touch position is shifted in the mold closing direction from the initial position due to the presence of a gap corresponding to the reduced mold thickness.

[0058] The relationship used in the mold thickness reduction process when the mold thickness is reduced will be explained. Figure 3 is a diagram showing the relationship for calculating the amount of reduction in mold thickness. The horizontal axis of Figure 3 represents the amount of push-in (extension) of the tie bars 9 when the movable platen 6 is moved. The push-in amount of the tie bars 9 is the amount by which the mold is clamped and contracted when the tie bars 9 extend in the negative direction of the X-axis due to the movement of the crosshead 12. The amount by which the mold is clamped and contracts is the same as the amount by which the movable platen 6 moves in the positive direction of the X-axis. In other words, the push-in amount of the tie bars 9 is equal to the change in the distance between the mold clamping housing 7 and the movable platen 6. The vertical axis of Figure 3 represents the generated mold clamping force.

[0059] If the mold thickness has not decreased, a mold clamping force is generated as the crosshead 12 moves from the mold touch position, and when the crosshead 12 moves by a movement amount a from the mold touch position, the crosshead 12 reaches the mold clamping completion position K and the set mold clamping force is reached. However, if the mold thickness has decreased, the mold touch position shifts from the initial position in the mold closing direction, so that no mold clamping force is generated between the mold touch position's initial position and when the mold actually touches the mold, i.e., in the gap corresponding to the decrease in mold thickness. Therefore, even if the crosshead 12 is moved to the mold clamping completion position K, the actual mold clamping force does not reach the set mold clamping force. In other words, the movement amount of the crosshead 12 from the mold touch position after the mold actually touches the mold to the mold clamping completion position K is less than the above-mentioned movement amount a.

[0060] Therefore, as shown in Fig. 3, the amount of reduction in mold thickness can be found by subtracting the amount of movement of the movable platen 6 corresponding to the detected mold clamping force actually detected at the mold clamping completion position K from the amount of movement a of the movable platen 6 when the set mold clamping force is reached at the mold clamping completion position K in the absence of a reduction in mold thickness. In this way, the amount of reduction in mold thickness can be easily found from the relationship of the stiffness diagram shown in Fig. 3. By correcting the mold clamping housing 7 in the mold closing direction by the calculated amount of reduction in mold thickness, the gap corresponding to the reduction in mold thickness is eliminated, and the set mold clamping force can be reached when the crosshead 12 is moved to the mold clamping completion position K.

[0061] FIG. 4 is a flowchart showing the control content of the mold thickness reduction step. The process of FIG. 4 is a process executed as a subroutine in the process of S10 in FIG. 2. When the mold thickness is reduced, the control device 100 calculates the amount of reduction in the mold thickness from the actual mold clamping force when the mold clamping completion position K is reached using the mechanical rigidity (S21). Specifically, in the process of S21, the corresponding movement amount of the movable platen 6 from the mold touch position is calculated from the actual mold clamping force, which is the detected mold clamping force stored in S6 in FIG. 2, and the obtained movement amount is subtracted from the movement amount a of the movable platen 6 corresponding to the set mold clamping force, thereby calculating the amount of reduction in the mold thickness. Next, the control device 100 corrects the position of the mold clamping housing 7 to the positive side of the X-axis based on the calculated amount of reduction in the mold thickness (S22), and ends the process.

[0062] By executing the processes of S21 to S22, the control device 100 can calculate the amount of reduction in mold thickness and correct the position of the mold clamping housing 7 toward the positive side of the X axis based on the calculated amount of reduction in mold thickness. As a result, even if the mold thickness is reduced during injection molding, the injection molding machine 1 can automatically set an appropriate position for the mold clamping housing 7 in accordance with the reduced mold thickness in a single process, and can therefore adjust to the desired set mold clamping force in a short time.

[0063] On the other hand, if the mold thickness increases, the mold will touch the platen 6 before the initial mold touch position is reached, and the clamping force will reach the set clamping force before the preset clamping completion position K is reached. If the crosshead 12 is moved to the clamping completion position K in this state, it is possible to calculate the increase in mold thickness using Figure 3 from the increased clamping force detected at the clamping completion position K. However, since an excessive load may be applied to the mold, which could damage the mold, in order to protect the machine, the crosshead 12 is stopped in the clamping process when the set clamping force is reached. Therefore, if the mold thickness increases, the amount of movement of the movable platen 6 from when the mold touches the platen 6 until the set clamping force is reached will end up being the movement amount a, and the increase in mold thickness cannot be calculated using the relationship in Figure 3.

[0064] However, the actual position of the crosshead 12 when the set mold clamping force is reached and the position of the crosshead 12 corresponding to the mold touch position can be calculated from the position sensor 26. Since there is a correlation between the position of the crosshead 12 and the position of the movable platen 6, in the mold thickness increasing step S12, the increase in mold thickness is calculated from the positional relationship between the position of the crosshead 12 and the position of the movable platen 6.

[0065] The relationship used in the mold thickness increasing process when the mold thickness is increased will be explained. Figure 5 shows the relationship for calculating the mold thickness increase amount. The horizontal axis of Figure 5 indicates the platen position, which is the position of the movable platen 6. The vertical axis of Figure 5 indicates the position of the crosshead 12 (the movement amount of the crosshead 12). The table in Figure 5 shows the positional relationship between the movable platen 6 and the crosshead 12 when only the servo motor 16 is moved, with no increase or decrease in mold thickness. Specifically, the solid line in Figure 5 indicates the relationship between the crosshead position and the platen position when the mold clamping process is performed from the mold touch position, and the dashed line in Figure 5 indicates the relationship between the crosshead position and the platen position during the mold opening and closing process up to the mold touch position. During the mold clamping process (solid line) in Figure 5, the mold is in contact with the platen, so even if the crosshead position moves about 100 mm, the platen position hardly changes. In contrast, during the mold opening and closing process, the platen position also increases or decreases significantly as the crosshead position increases or decreases.

[0066] The increase in mold thickness is determined using Figure 6, which is an enlarged view of the solid line portion of the relationship in Figure 5. Figure 6 is a diagram for explaining the case where there is no change in mold thickness and the case where the mold thickness is increasing. Figure 6(a) is a diagram for explaining the case where there is no change in mold thickness, and Figure 6(b) is a diagram for explaining the case where the mold thickness is increasing. As shown in Figure 6(a), the mold platen position when the mold touch position is reached is set to 0 mm.

[0067] If there is no change in mold thickness, as shown in Figure 6(a), at the mold touch position, the mold platen position will be 0 mm and the crosshead position will be approximately 130 mm. When mold clamping is performed from the mold touch position, the crosshead 12 moves in the positive direction of the X axis (mold closing direction) from the mold touch position, and the movable platen 6 moves in the positive direction of the X axis (mold closing direction). If there is no change in mold thickness, the crosshead 12 will eventually move to the mold clamping completion position K. When the mold clamping completion position is reached, the mold platen position will be approximately -9 mm and the crosshead position will be approximately 0.3 mm.

[0068] The amount of thrust of the tie bars 9 when the crosshead 12 moves from the mold touch position to the mold clamping completion position K is defined as E. The amount of thrust E of the tie bars 9 is the same as the amount by which the movable platen 6 moves in the positive direction of the X axis. Note that when there is no change in the mold thickness, the range of the crosshead 12 from the allowable position D shown in Figure 6(a) to the mold clamping completion position K indicates a range in which an increase in mold thickness does not affect injection molding.

[0069] When the mold thickness is increasing, as shown in FIG. 6(b), the crosshead 12 stops at crosshead position C. This is because the increase in mold thickness causes the crosshead 12 to reach the set mold clamping force before reaching the mold clamping completion position K, and the crosshead 12 stops before the mold clamping completion position K. If the mold platen position corresponding to crosshead position C is A, then the movable platen 6 reaches the set mold clamping force at mold platen position A. In other words, the increase in mold thickness means that the movable platen 6 cannot be moved in the mold closing direction as much as it would be if there was no change in mold thickness.

[0070] Since the amount of penetration E up to the mold clamping completion position K when there is no change in mold thickness is known in advance, the amount by which the movable platen 6 cannot move in the mold closing direction can be determined by subtracting the platen position A corresponding to the crosshead position C from the amount of penetration E up to the mold clamping completion position K. The amount by which the movable platen 6 cannot move is equal to the increase in mold thickness, so the increase in mold thickness can be calculated using the following formula (1).

[0071] Increase in mold thickness = | Push-in amount E to clamping completion position K - platen position A corresponding to crosshead position C | ... (1) In equation (1), the amount of push-in E and the platen position A are negative values, so the absolute value of the difference is taken. Considering the movement amount of the movable platen 6, the increase in mold thickness can be obtained by subtracting the movement amount of the movable platen 6 corresponding to the crosshead position C when the set clamping force is reached in the case of an increase in mold thickness from the movement amount of the movable platen 6 calculated from the position of the movable platen 6 corresponding to the mold touch position in the case of no increase in mold thickness and the position of the movable platen 6 corresponding to the mold clamping completion position K. In this way, the increase in mold thickness can be easily obtained from the relationship in Figure 5. Specifically, the increase in mold thickness can be obtained from the relationship between the crosshead position and the platen position when mold clamping is performed in Figure 6. A table showing the relationship in Figure 5 is pre-stored in memory 102.

[0072] 7 is a flowchart showing the control content of the mold thickness increasing step. The processing in FIG. 7 is processing executed as a subroutine in the processing of S12 in FIG. 2. When the mold thickness increases, the control device 100 calculates the mold platen position A at the current crosshead position C from the relationship in FIG. 5 (S31). The processing in S31 is processing to obtain the position of the movable platen 6 from the crosshead position C when the set mold clamping force is reached. Next, the control device 100 calculates the push-in amount E from the mold touch position to the mold clamping completion position K from the relationship in FIG. 5 (S32). The processing in S32 is processing to obtain the movement amount of the movable platen 6 by obtaining the push-in amount E from the mold touch position to the mold clamping completion position K when there is no change in the mold thickness.

[0073] Next, the control device 100 calculates the increase in mold thickness from the relationship |Amount of push-in E to the clamping completion position K - Platen position A corresponding to the crosshead position C| = Increase in mold thickness (S33). That is, the control device 100 calculates the increase in mold thickness by calculating the absolute value of the difference between the amount of push-in E to the clamping completion position K calculated in S32 and the platen position A corresponding to the crosshead position C calculated in S31. The processing in S33 is the same as the processing for calculating the increase in mold thickness by subtracting the movement amount of the movable platen 6 corresponding to the crosshead position C when the set clamping force is reached in the case where the mold thickness has increased from the movement amount of the movable platen 6 calculated from the position of the movable platen 6 corresponding to the mold touch position in the case where there is no increase in mold thickness and the position of the movable platen 6 corresponding to the clamping completion position K. Next, the control device 100 corrects the position of the mold clamping housing 7 based on the calculated increase in mold thickness (S34), and ends the processing.

[0074] By executing the processes of S31 to S34, the control device 100 can calculate the increase in mold thickness and correct the position of the mold clamping housing 7 based on the calculated increase in mold thickness. As a result, even if the mold thickness increases during injection molding, the injection molding machine 1 can automatically set an appropriate position for the mold clamping housing 7 in accordance with the increased mold thickness in a single process, and can therefore adjust to the set mold clamping force in a short time.

[0075] As described above, the control device 100 calculates the amount of increase or decrease in mold thickness in a single process based on the mold clamping completion position K and the crosshead position C when the mold clamping force is applied in the mold clamping process during injection molding, and corrects the position of the mold clamping housing 7 based on the amount of increase or decrease in mold thickness. As a result, even if the mold thickness changes, the injection molding machine 1 can automatically set the mold clamping housing 7 to an appropriate position in a single process according to the changed mold thickness, and can adjust to the set mold clamping force in a short time. Therefore, the injection molding machine 1 can ensure the desired mold clamping force and shorten the processing time, thereby improving the operating rate.

[0076] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0077] 1 injection molding machine, 2 injection unit, 3 mold clamping unit, 5 fixed platen, 6 movable platen, 7 mold clamping housing, 9 tie bar, 11 mold clamping mechanism, 12 crosshead, 13 ball nut, 14 ball screw, 16, 153, 154 servo motor, 18, 19 gear, 20 geared motor, 22, 23 mold component, 25 sensor, 26, 27 position sensor, 100 control unit, 101 CPU, 102 memory, 111 bed, 121 base, 122 heating cylinder, 123 screw, 124 drive unit, 125 hopper, 126 injection nozzle, 127 injection moving unit, 128 temperature sensor, 130 operation panel, 160 servo amplifier.

Claims

1. An injection molding machine that adjusts a clamping force for clamping molds to be integrated by moving a movable platen on which a first mold member is attached relative to a fixed platen on which a second mold member is attached, a mold clamping housing connected to the fixed platen; a first mechanism for adjusting a distance between the mold clamping housing and the fixed platen; a second mechanism that applies the mold clamping force to the mold; a control device; The second mechanism is a toggle mechanism including a screw shaft that is rotationally driven and a crosshead that moves with the rotation of the screw shaft, The control device calculating an increase or decrease in mold thickness, which is the thickness of the mold, based on a mold clamping completion position, which is a reference position of the crosshead set corresponding to a preset mold clamping force, and a position of the crosshead when the mold clamping force is applied in a mold clamping step during injection molding; an injection molding machine that corrects the position of the mold clamping housing using the first mechanism based on the increase or decrease in the mold thickness.

2. a storage device storing a relationship between the position of the crosshead and the position of the movable platen; 2. The injection molding machine according to claim 1, wherein the control device calculates an increase in the mold thickness from the relationship stored in the storage device when the position of the crosshead when the set mold clamping force is reached has not reached the mold clamping completion position.

3. Further comprising a storage device; the storage device stores an upper limit value and a lower limit value of the set mold clamping force, and a relationship between the mold clamping force and a movement amount of the movable platen from a mold touch position where the first mold member and the second mold member come into contact with each other, 2. The injection molding machine according to claim 1, wherein when the position of the crosshead reaches the mold clamping completion position and the detected mold clamping force detected in the mold clamping process is outside a range determined by the upper limit value and the lower limit value, the control device calculates the amount of reduction in the mold thickness from the relationship stored in the storage device.

4. 3. The injection molding machine according to claim 2, wherein the control device calculates the increase in the mold thickness by subtracting the movement amount of the movable platen corresponding to the position of the crosshead when the set mold clamping force is reached in a case where the mold thickness has increased from the movement amount of the movable platen calculated from the position of the movable platen corresponding to the mold touch position where the first mold member and the second mold member come into contact in a case where there is no increase in the mold thickness and the position of the movable platen corresponding to the mold clamping completion position.

5. 4. The injection molding machine according to claim 3, wherein the control device calculates the amount of reduction in the mold thickness by subtracting a movement amount of the movable platen corresponding to the detected mold clamping force from a movement amount of the movable platen when the set mold clamping force is reached.

6. An adjustment method for adjusting, by a control device, a mold clamping force for clamping molds that are integrated by moving a movable platen on which a first mold member is attached relative to a fixed platen on which a second mold member is attached in an injection molding machine, comprising: The injection molding machine a mold clamping housing connected to the fixed platen; a first mechanism for adjusting a distance between the mold clamping housing and the fixed platen; a second mechanism that applies the mold clamping force to the mold, The second mechanism is a toggle mechanism including a screw shaft that is rotationally driven and a crosshead that moves with the rotation of the screw shaft, The adjustment method includes: a step of calculating an increase or decrease in mold thickness, which is the thickness of the mold, based on a mold clamping completion position, which is a reference position of the crosshead set corresponding to a preset mold clamping force, and a position of the crosshead when the mold clamping force is applied in a mold clamping process during injection molding; and correcting the position of the mold clamping housing using the first mechanism based on the increase or decrease in the mold thickness.

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