Injection molding machine and method for adjusting mold clamping force change amount in injection molding machine

Abstract

To provide an injection molding machine that has low possibility of causing other molding defects even when mold clamping force is adjusted, can respond immediately to changes in the mold clamping force, and is less likely to have difference between operators in setting even when the operator of the injection molding machine changes.SOLUTION: An injection molding machine 10 comprises: a mold clamping device 12 having a fixed mold 30 and a movable mold 33 that constitute a mold 28, and a mold clamping force sensor 27 that detects the mold clamping force of the movable mold 33 relative to the fixed mold 30; an injection device 14 having an injection nozzle 46 and a screw 48 for filling the mold 28 with molten resin via the injection nozzle 46; and a control device 15. The control device 15 monitors a change amount in the mold clamping force from the mold clamping force sensor 27, and when the change amount exceeds a predetermined upper limit, it increases the slow forward movement time at the VP switching timing, and when the change amount falls below a predetermined lower limit, it decreases the slow forward movement time at the VP switching timing.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an injection molding machine having a clamping force adjusting device and a method for adjusting the amount of change in the clamping force of an injection molding machine.

Background Art

[0002] Conventionally, methods for adjusting the clamping force in an injection molding machine have been developed (for example, Patent Document 1).

[0003] Patent Document 1 discloses that when molding by clamping a mold in an injection molding machine, based on the mold displacement detected using a mold gap detection sensor, the injection peak pressure on the injection molding machine side, and the injection forwardmost position, the mold clamping force is adjusted to perform molding with an appropriate mold clamping force that does not cause flash defects and can reduce the energy required for clamping.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of the injection molding machine disclosed in Patent Document 1, since the clamping force is adjusted by changing the basic conditions such as the injection peak pressure and the injection forwardmost position, which are the basis of injection molding, the degree of influence on the entire injection molding is large, and even if flash defects can be avoided, there is a possibility that other problems may occur.

[0006] The present invention has been made in view of such problems, and its object is to provide an injection molding machine in which the possibility of leading to other molding defects is low even when the clamping force is adjusted, immediate response to changes in the clamping force is possible, and it is difficult for human error to occur even when the setter of the injection molding machine changes, and a method for adjusting the amount of change in the clamping force of an injection molding machine.

Means for Solving the Problem

[0007] According to one aspect of the present invention, a clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold; an injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle; and a control device, wherein the control device monitors the change amount of the clamping force from the clamping force sensor, when the change amount exceeds a predetermined upper limit, increases the time of the very slow forward movement at the timing of the VP switching, when the change amount is below a predetermined lower limit, decreases the time of the very slow forward movement at the timing of the VP switching An injection molding machine is provided.

[0008] According to another aspect of the present invention, a clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold; an injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle; and a control device, wherein the control device monitors the change amount of the clamping force from the clamping force sensor, when the change amount exceeds a predetermined upper limit, decreases the holding pressure screw speed, when the change amount is below a predetermined lower limit, increases the holding pressure screw speed An injection molding machine is provided.

[0009] According to another aspect of the present invention, A clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, And a control device, The control device, Monitors the change amount of the clamping force from the clamping force sensor, When the change amount exceeds a predetermined upper limit, Moves the VP switching position to a position far from the injection nozzle, When the change amount falls below a predetermined lower limit, Moves the VP switching position to a position close to the injection nozzle An injection molding machine is provided.

[0010] According to another aspect of the present invention, A clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, A method for adjusting the change amount of the clamping force of an injection molding machine provided with a control device, Wherein the control device, Monitors the change amount of the clamping force from the clamping force sensor, When the change amount exceeds a predetermined upper limit, Increases the time of the slow forward movement at the timing of VP switching, When the change amount falls below a predetermined lower limit, Decreases the time of the slow forward movement at the timing of VP switching A method for adjusting the change amount of the clamping force of an injection molding machine is provided.

[0011] According to another aspect of the present invention, A clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, A method for adjusting the amount of change in the clamping force of an injection molding machine, comprising a control device, wherein the control device, monitors the amount of change in the clamping force from the clamping force sensor, when the amount of change exceeds a predetermined upper limit, reduces the holding pressure screw speed, when the amount of change falls below a predetermined lower limit, increases the holding pressure screw speed. A method for adjusting the amount of change in the clamping force of an injection molding machine is provided.

[0012] According to another aspect of the present invention, a clamping device having a fixed mold and a movable mold constituting the mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, an injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, a method for adjusting the amount of change in the clamping force of an injection molding machine, comprising a control device, wherein the control device, monitors the amount of change in the clamping force from the clamping force sensor, when the amount of change exceeds a predetermined upper limit, moves the VP switching position to a position far from the injection nozzle, when the amount of change falls below a predetermined lower limit, moves the VP switching position to a position close to the injection nozzle. A method for adjusting the amount of change in the clamping force of an injection molding machine is provided.

Advantages of the Invention

[0013] According to the injection molding machine and the method for adjusting the change amount of the clamping force of the injection molding machine according to the present invention, by adjusting the time of "slow forward", the "holding pressure screw speed", and the "VP switching position", the change amount of the clamping force is made within a predetermined range. Therefore, the possibility of leading to other molding defects is low as in the case of directly adjusting the clamping force, immediate response to changes in the clamping force is possible, and it is difficult for human error to occur even if the setter of the injection molding machine changes.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0015] (Configuration of Injection Molding Machine 10) The injection molding machine 10 according to the present embodiment is a machine that manufactures molded products by repeating a molding cycle such as mold closing, clamping, injection filling of molten resin, metering, mold opening, and taking out the molded product. As shown in FIG. 1, it generally includes a clamping device 12, an injection device 14, and a control device 15.

[0016] The clamping device 12 includes a machine base 16, a fixed platen 18, a movable platen 20, a pressure receiving platen 22, tie bars 24, a toggle mechanism 26, and a clamping force sensor 27.

[0017] The machine base 16 is a member that constitutes the clamping device 12 and a member that serves as a base for the injection device 14.

[0018] The fixed platen 18 is fixed on the machine base 16, and the fixed mold 30 that constitutes the mold 28 is attached thereto.

[0019] The movable platen 20 is a member that slides on the machine base 16 so as to approach and separate from the fixed platen 18, and the movable mold 33 that constitutes the mold 28 is attached thereto. When the movable mold 33 contacts the fixed mold 30, a cavity into which the molten resin is filled is formed.

[0020] The pressure receiving platen 22 is a member fixed on the machine base 16 on the side opposite to the fixed platen 18 as viewed from the movable platen 20.

[0021] The tie bar 24 is a round bar-shaped member having one end fixed to the fixed platen 18 and the other end fixed to the pressure receiving platen 22. Further, the tie bar 24 is inserted into a tie bar insertion hole 31 formed in the movable platen 20 disposed between the fixed platen 18 and the pressure receiving platen 22. Thereby, the movable platen 20 can slide in the left-right direction in the drawing along the tie bar 24 on the machine base 16. Note that a plurality of (for example, four) tie bars 24 are used.

[0022] The toggle mechanism 26 is a mechanism for approaching and separating the movable platen 20 from the fixed platen 18, and the mold clamping drive device 32 is attached to the pressure receiving platen 22.

[0023] The movable platen 20 moves along the tie bar 24 (moves in the left-right direction in the drawing) when the driving force of the mold clamping drive device 32 is transmitted through the toggle mechanism 26. When the movable platen 20 moves leftward, the fixed mold 30 and the movable mold 33 separate. On the other hand, when the movable platen 20 moves rightward, the fixed mold 30 and the movable mold 33 come into contact with each other, and a cavity (internal space) is formed inside the mold 28. Then, when a pressure in the direction of moving the movable platen 20 rightward is further applied, the fixed mold 30 and the movable mold 33 are clamped.

[0024] The clamping force sensor 27 is a sensor that measures the clamping force of the movable mold 33 against the fixed mold 30, and is attached to at least one tie bar 24. Specifically, the strain of the tie bar 24 during clamping is measured, and in the control device 15, the clamping force is calculated based on the amount of strain.

[0025] The injection device 14 is a device that injects and fills molten resin into the mold (cavity) 28 formed by the contact of the movable mold 33 with the fixed mold 30, and has a heating cylinder 44 with a heater arranged around it and an injection nozzle 46 whose tip abuts against the mold 28. Inside the heating cylinder 44, a screw 48 for sending the molten resin to the injection nozzle 46 is accommodated.

[0026] (Characteristic control by the control device 15) The control device 15 is a device that controls all of the molding cycles of the injection molding machine 10. Hereinafter, only the characteristic control of the injection molding machine 10 according to the present embodiment will be described (see FIG. 2).

[0027] When repeatedly performing the molding cycle by the injection molding machine 10, in the control device 15, during the period from "clamping" to "injecting and filling molten resin" in the previous molding cycle, the control device 15 always monitors the change amount of the clamping force calculated from the strain amount signal from the clamping force sensor 27.

[0028] If the monitored change amount of the clamping force is within a predetermined range (for example, when the set clamping force is 1,000 kN, after clamping at 1,000 kN, the change in the clamping force due to the increase in the internal pressure of the mold during the filling of the molten resin is in the range of 10 kN or more and 50 kN or less), the control device 15 repeats the same molding cycle as the previous time without performing a special operation. Note that the monitoring of the change amount of the clamping force may be performed not only during the injection and filling of the molten resin but also during clamping, or may be performed for either one of them.

[0029] If the monitored change amount of the clamping force exceeds the predetermined range, the control device 15 is configured to perform a first response.

[0030] (First Correspondence) Normally, when filling the molten resin into the mold 28 by the injection device 14, the screw 48 of the injection device 14 advances by a predetermined length to fill a predetermined amount of molten resin into the mold 28. After this advancement, the screw 48 is operated to perform a pressure holding operation so that the pressure value inside the mold 28 becomes a predetermined value. Note that the switching position and timing between the forward movement and the pressure holding operation of the screw 48 are referred to as "VP switching".

[0031] Here, when the change amount of the monitored mold clamping force exceeds a predetermined upper limit, the control device 15 increases, for example, the "slow forward movement" at the end of this forward movement by 0.5 seconds and then performs a pressure holding operation (for example, if the slow forward movement time of the screw 48 was 0 s, the slow forward movement time is set to 0.5 s). Note that the speed of the forward movement of the screw 48 is, for example, 10 to 300 mm / s, and the speed during the slow forward movement is, for example, 0.1 mm / s.

[0032] The control device 15 confirms the change amount of the mold clamping force when the first correspondence is performed in this way. If the change amount is within a predetermined range, the control device 15 continues to perform the next molding cycle with the time of the previous "slow forward movement".

[0033] If the change amount still exceeds the predetermined upper limit, the control device 15 increases the time of the "slow forward movement" (for example, to 1.0 s) and performs the next molding cycle. If the change amount of the mold clamping force still exceeds the predetermined upper limit even after increasing the time of the "slow forward movement", the control device 15 continues to further increase the time of the "slow forward movement". Then, when the "slow forward movement" reaches a predetermined time (for example, 2.0 s), the control device 15 performs the second correspondence (see FIG. 3).

[0034] (Second Correspondence) As described above, after the VP switching, the screw 48 is operated so that the pressure inside the mold 28 reaches a predetermined pressure value to perform a pressure holding operation. However, when the "very slow forward movement" reaches a predetermined time (for example, 2.0 seconds) in the first response, the control device 15, as a second response, continues the above-described first response and reduces the speed at which the screw 48 advances during the pressure holding operation ("pressure holding screw speed"). For example, if the forward speed of the screw 48 during the normal pressure holding operation was 20 mm / s, it is reduced to 15 mm / s.

[0035] In this way, the control device 15 checks the change amount of the clamping force when the second response is performed. If the change amount is within a predetermined range, the control device 15 continues the next molding cycle at the previous "pressure holding screw speed".

[0036] If the change amount still exceeds the predetermined upper limit, the control device 15 further reduces the "pressure holding screw speed" (for example, to 10 mm / s) and performs the next molding cycle. If the change amount of the clamping force still exceeds the predetermined upper limit even when the "pressure holding screw speed" is reduced, the control device 15 continues to further reduce the "pressure holding screw speed". Then, when the "pressure holding screw speed" reaches a predetermined value (for example, 1 mm / s), the control device 15 performs a third response (see FIG. 4).

[0037] (Third response) When the "pressure holding screw speed" reaches a predetermined value (for example, 1 mm / s) in the second response, the control device 15, as a third response, continues the above-described second response and changes the position of the screw 48 when performing the VP switching ("VP switching position"). For example, when the normal VP switching position is 10 mm, it is changed to +1 mm (a position where the screw 48 is 1 mm away from the injection nozzle 46). As a result, the amount of molten resin entering the mold 28 changes.

[0038] In this way, the control device 15 checks the change amount of the clamping force when the third response is performed. If the change amount is within a predetermined range, the control device 15 continues the next molding cycle at the previous "VP switching position".

[0039] If the change amount still exceeds the predetermined upper limit, the control device 15 moves the "VP switching position" to a position farther from the injection nozzle 46 (for example, to +2 mm) and performs the next molding cycle. If the change amount of the clamping force still exceeds the predetermined upper limit even when the "VP switching position" is further changed, the control device 15 continues to move the "VP switching position" to a position farther from the injection nozzle 46. When the movement amount of the "VP switching position" reaches a predetermined value (for example, +5 mm), the control device 15 ends the response.

[0040] (When the change amount of the clamping force is below the predetermined lower limit) Conversely to the description so far, when the monitored change amount of the clamping force is below the predetermined lower limit, the control device 15 reduces the time of "slow forward movement" (for example, from 0.5 seconds to 0.4 seconds) and performs the next molding cycle (the first response). If the change amount of the clamping force is still below the predetermined lower limit even when the time of "slow forward movement" is reduced, the control device 15 continues to reduce the time of "slow forward movement". When the "slow forward movement" reaches a predetermined time (for example, 0 seconds), the control device 15 performs the second response.

[0041] When the change amount of the clamping force is still below the predetermined lower limit even when the time of "slow forward movement" is reduced, the control device 15 increases the "holding pressure screw speed" (for example, from 15 mm / s to 17 mm / s) and performs the next molding cycle (the second response). If the change amount of the clamping force is still below the predetermined lower limit even when the "holding pressure screw speed" is increased, the control device 15 continues to increase the "holding pressure screw speed". When the "holding pressure screw speed" reaches a predetermined speed (for example, 40 mm / s), the control device 15 performs the third response.

[0042] When the "holding pressure screw speed" reaches a predetermined speed (for example, 40 mm / s) in the second correspondence, the control device 15, as a third correspondence, changes the position of the screw 48 (the "VP switching position") when performing VP switching following the above-described second correspondence. For example, when the normal VP switching position is 10 mm, it is changed to -1 mm (a position where the screw 48 is close to the injection nozzle 46 by 1 mm).

[0043] Even if the change amount still falls below the predetermined lower limit, the control device 15 changes the "VP switching position" to a position closer to the injection nozzle 46 (for example, to a position close to -2 mm) and performs the next molding cycle. If the change amount of the clamping force still falls below the predetermined lower limit even after further changing the "VP switching position", the control device 15 continues to change the "VP switching position". Then, when the change amount of the "VP switching position" reaches a predetermined value (for example, -5 mm), the control device 15 ends the correspondence.

[0044] As described above, in the injection molding machine 10 according to this embodiment, by adjusting the time of "slow forward movement", the "holding pressure screw speed", and the "VP switching position", the change amount of the clamping force is within a predetermined range. Therefore, the possibility of leading to other molding defects as in the case of directly adjusting the clamping force is low, immediate response to changes in the clamping force is possible, and it is difficult for human error to occur even if the setter of the injection molding machine changes.

[0045] (Modification 1) If the change amount of the clamping force is still outside the predetermined range even after performing the above-described "third correspondence", the clamping force may be changed. For example, the mounting position of the movable platen 20 with respect to the toggle mechanism 26 is moved to bring the movable platen 20 closer to the fixed platen 18 (the clamping force increases), or conversely, the movable platen 20 is moved slightly away from the fixed platen 18 (the clamping force decreases).

[0046] (Modification 2) In the injection molding machine 10 according to the above-described embodiment, the clamping force sensor 27 is attached to the tie bar 24. However, as long as the clamping force can be measured, the clamping force sensor 27 can also be attached to other positions.

[0047] (Modification 3) In the injection molding machine 10 according to the above-described embodiment, the first correspondence, the second correspondence, and the third correspondence were applied in this order. However, each correspondence may be applied in a different order. Furthermore, only any one of the correspondences may be applied, or any two of the correspondences may be applied.

[0048] The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and it is intended that all modifications within the meaning and scope equivalent to the claims be included.

Description of Reference Numerals

[0049] 10... injection molding machine, 12... clamping device, 14... injection device, 15... control device, 16... machine base, 18... fixed platen, 20... movable platen, 22... pressure receiving platen, 24... tie bar, 26... toggle mechanism, 27... clamping force sensor, 28... mold, 30... fixed mold, 31... tie bar insertion hole, 32... clamping drive device, 33... movable mold, 44... heating cylinder, 46... injection nozzle, 48... screw

Claims

1. A clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, And a control device, The control device, Monitors the change amount of the clamping force from the clamping force sensor, When the change amount exceeds a predetermined upper limit, Increase the time of the slow forward movement at the timing of VP switching, When the change amount falls below a predetermined lower limit, Decrease the time of the slow forward movement at the timing of VP switching An injection molding machine.

2. A clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, And a control device, The control device, Monitors the change amount of the clamping force from the clamping force sensor, When the change amount exceeds a predetermined upper limit, Reduce the holding pressure screw speed, When the change amount falls below a predetermined lower limit, Increase the holding pressure screw speed An injection molding machine.

3. A clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, And a control device, The control device, Monitors the change amount of the clamping force from the clamping force sensor, When the change amount exceeds a predetermined upper limit, Move the VP switching position to a position far from the injection nozzle, When the change amount falls below a predetermined lower limit, Move the VP switching position to a position close to the injection nozzle An injection molding machine.

4. A clamping device having a fixed mold and a movable mold constituting a mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling molten resin into the mold through the injection nozzle, A method for adjusting the change amount of the clamping force of an injection molding machine provided with a control device, The control device, Monitors the change amount of the clamping force from the clamping force sensor, When the change amount exceeds a predetermined upper limit, Increase the time of the slow forward movement at the timing of VP switching, When the change amount falls below a predetermined lower limit, Reduce the time of very slow forward movement at the timing of VP switching Method for adjusting the amount of change in clamping force of an injection molding machine

5. A clamping device having a fixed mold and a movable mold constituting the mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling the mold with molten resin through the injection nozzle, A method for adjusting the amount of change in clamping force of an injection molding machine, comprising a control device, wherein the control device, monitors the amount of change in clamping force from the clamping force sensor, when the amount of change exceeds a predetermined upper limit, reduces the holding pressure screw speed, when the amount of change falls below a predetermined lower limit, increases the holding pressure screw speed Method for adjusting the amount of change in clamping force of an injection molding machine

6. A clamping device having a fixed mold and a movable mold constituting the mold, and a clamping force sensor for detecting the clamping force of the movable mold with respect to the fixed mold, An injection device having an injection nozzle and a screw for filling the mold with molten resin through the injection nozzle, A method for adjusting the amount of change in clamping force of an injection molding machine, comprising a control device, wherein the control device, monitors the amount of change in clamping force from the clamping force sensor, when the amount of change exceeds a predetermined upper limit, moves the VP switching position to a position far from the injection nozzle, when the amount of change falls below a predetermined lower limit, moves the VP switching position to a position close to the injection nozzle Method for adjusting the amount of change in clamping force of an injection molding machine

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