Method and apparatus for controlling plasticization in an injection molding machine

Abstract

It suppresses the generation of unnecessary shear insulation, preventing discoloration, yellowing, and burning of molded products, and dramatically improving molding quality. [Solution] In advance, as molding conditions, at least a torque target value Ts for screw rotation torque T and an upper limit value Ru for screw rotation speed R are set. During the plasticization process, the rotation of the screw 3 is controlled with respect to the torque target value Ts. At the same time, a graphic display screen 51 is popped up by a changeover switch 50 from the normal waveform display screen 11nn, which displays at least one change data of injection speed V, injection pressure Pp, and mold parting opening Lm during molding, to display at least one change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process.

Description

Technical Field

[0001] The present invention relates to a plasticization control method and apparatus for an injection molding machine including a plasticization step of plasticizing a molding material introduced into a heating cylinder by controlling the rotation of a screw inserted into the heating cylinder.

Background Art

[0002] Conventionally, an injection molding machine includes a plasticization step of plasticizing a molding material introduced into a heating cylinder by controlling the rotation of a screw inserted into the heating cylinder, and injects and fills a molten resin obtained by plasticization into a predetermined mold by controlling the forward movement of the screw to perform molding. In particular, as a plasticization control method for performing plasticization, a control method for an injection molding machine described in Patent Document 1 and a metering control method for an injection molding machine described in Patent Document 2 are known.

[0003] The control method described in Patent Document 1 is intended to accurately stop both the rotation and the backward movement of the screw at the end of metering to ensure a high metering accuracy with a uniform resin density. Specifically, in advance, a stop target position obtained by adding a predetermined distance to the screw rotation stop position and a rotation speed pattern for rotating the screw are set. During metering, the screw position is detected at predetermined time intervals, and the remaining rotation speed pattern for stopping the rotation of the screw from the detected screw position at the stop target position is predicted by calculation. Then, the rotation of the screw is controlled according to the predicted rotation speed pattern. When the screw reaches the screw rotation stop position, rotation stop control for the screw is performed, and when the backward movement speed of the screw reaches a predetermined speed set in advance, backward movement stop control for the screw is performed.

[0004] Furthermore, the metering control method described in Patent Document 2 aims to ensure normal metering operation when molding super engineering plastics and the like with an injection molding machine with a small injection capacity, thereby improving molding quality and productivity. In this method, upper and / or lower limits are set in advance for the retraction speed (metering time) of the injection screw during metering, and the retraction speed (metering time) of the injection screw is detected during metering. When the retraction speed (metering time) falls outside the upper and / or lower limits, the rotation of the injection screw is stopped for a set time, specifically, for a set time to resolve insufficient plasticization of the molding material, and then the injection screw is restarted. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2007-118406 [Patent Document 2] Japanese Patent Application Publication No. 10-24468 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] However, the conventional plasticization control methods used in injection molding machines described above also had the following problems that needed to be addressed.

[0007] In other words, in the plasticization process, molding material such as pellets is typically fed from a hopper into a heated cylinder, and the plasticization process is carried out by controlling the rotation of a screw inserted into the heated cylinder. In this case, an appropriate rotation speed (rotational velocity) is set for the screw rotation speed, and the rotation speed of the screw is controlled to be kept constant in order to achieve a uniform plasticization process. Note that the rotation speed to be set may include multiple stages.

[0008] Incidentally, the molding material inside the heating cylinder is plasticized by the heated cylinder and sheared by the rotation of the screw. Therefore, depending on the type of molding material, the heating state during the plasticization process of the molding material may vary considerably.

[0009] For example, in the case of powdered resin materials, the molding material itself is prone to absorbing moisture due to its powdery state, and in addition, it has properties that make it difficult to adapt to the rotation of the screw, and the shear pressure fluctuates greatly, making it difficult to plasticize. Figure 8 shows the conventional operating state during the plasticization process. As is clear from the figure, the screw rotation speed R is controlled to remain constant to maintain the set rotation speed, while the screw rotation torque T fluctuates greatly. Moreover, the range of variation in this fluctuation is large, and in addition, the screw retraction position X also fluctuates greatly.

[0010] When shear pressure increases, both shear intensity and its variation increase, leading to greater variation in the plasticization state of the molten resin within the heating cylinder and a decrease in the plasticization quality of the molten resin. As a result, variations in mass of the molded product increase, and in particular, with powdered resin materials, discoloration, yellowing, burning, etc., are more likely to occur, resulting in a decrease in molding quality.

[0011] Moreover, in this situation, it is difficult to obtain sufficient information to make decisions regarding the appropriate screw rotation torque T, making it difficult to easily adjust molding conditions. Therefore, for example, if an inappropriate rotation torque occurs, such as when the rotation torque T becomes too low, it is necessary to check the load pressure fluctuation value during normal operation and then set the appropriate screw rotation torque T. However, there was a difficulty in making quick and accurate adjustments.

[0012] The present invention aims to provide a plasticization control method and apparatus for an injection molding machine that solves the problems present in the background technology described above. [Means for solving the problem]

[0013] The plasticization control method for an injection molding machine M according to the present invention solves the above-mentioned problems by comprising a plasticization step (Sa) in which the molding material introduced into the heating cylinder 2 is plasticized by controlling the rotation of a screw 3 inserted into the heating cylinder 2, and the plasticized molten resin is injected and filled into a predetermined mold 70 by controlling the forward movement of the screw 3 to perform molding. In this plasticization control method for an injection molding machine M, at least a torque target value Ts for the screw rotation torque T and an upper limit value Ru for the screw rotation speed R are set in advance as molding conditions, and the rotation of the screw 3 is controlled with respect to the torque target value Ts during the plasticization process, and a graphic display screen 51 displaying at least one change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process is popped up by a changeover switch 50 on a normal waveform display screen 11nn that displays at least one change data of injection speed V, injection pressure Pp, and mold parting opening Lm during molding.

[0014] On the other hand, the plasticization control device 1 of the injection molding machine M according to the present invention solves the above-mentioned problems by controlling the rotation of a screw 3 inserted into the heating cylinder 2 to plasticize the molding material introduced into the heating cylinder 2, and by controlling the forward movement of the screw 3 to inject and fill the plasticized molten resin into a predetermined mold 70 to perform molding, and includes a molding condition setting function Fs which sets at least a torque target value Ts for the screw rotation torque T and an upper limit value Ru for the screw rotation speed R as molding conditions, and plasticization processing The molding machine controller 10 is characterized by having a plasticization control function unit Fc that controls the rotation of the screw 3 with respect to a torque target value Ts at times, and a plasticization display function unit Fd that, when switched by a changeover switch 50, pops up a graphic display screen 51 that displays at least one change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process, in addition to the normal waveform display screen 11nn of the display 11 which displays change data of at least one change data of injection speed V, injection pressure Pp, and parting opening amount Lm of the mold.

[0015] Furthermore, in a preferred embodiment of the present invention, it is desirable that the molding material contains a powdered resin material when implementing the plasticization control method. During the screw rotation in the plasticization process (Sa), the rotational state of the screw 3 can be monitored, and error processing can be performed if an abnormality in the rotation of the screw 3 occurs. In this case, the abnormality in rotation can include a state in which the rotational speed falls below a lower limit value set for the screw rotation speed R. [Effects of the Invention]

[0016] According to the plasticization control method and apparatus 1 for the injection molding machine M of the present invention, the following remarkable effects are achieved.

[0017] (1) In advance, as molding conditions, at least a torque target value Ts for the screw rotation torque T and an upper limit value Ru for the screw rotation speed R are set, and the rotation of the screw 3 is controlled with respect to the torque target value Ts during the plasticization process. As a result, the problem of excessively large shear pressure in the plasticization process (Sa) is eliminated, the occurrence of unnecessary shear heat is suppressed, and variations therein can be suppressed. This improves the quality of the molten resin, and in particular, prevents discoloration, yellowing, burning, etc. of the molded product, dramatically improving the molding quality.

[0018] (2) The operating state of the heating cylinder 2 can be visualized from multiple angles, allowing the operator to accurately grasp the plasticization state of the molten resin and easily and quickly obtain information for making appropriate decisions regarding the screw rotation torque T. As a result, the operator can quickly and accurately adjust the molding conditions. Moreover, it becomes possible to easily and accurately grasp the operating state of the entire molding process, which can contribute to reducing defective products and improving mass production efficiency, as well as enabling quick preventative measures against troubles.

[0019] (3) In a preferred embodiment, when implementing the plasticization control method, if the powdery resin material is included in the molding material, it is difficult to adapt to the rotation of the screw 3, and the powdery resin material has properties such as high hygroscopicity and is likely to cause deterioration of the material quality. Therefore, the controllability (moldability) of the plasticization control of the powdery resin material can be improved, so that the occurrence of discoloration, yellowing (especially yellowing of white systems), burning, etc. of the molded product made of the powdery resin material can be prevented, and the molding quality can be greatly improved.

[0020] (4) In a preferred embodiment, when the screw is rotating during the plasticization process (Sa), if the rotation state of the screw 3 is monitored and error handling is performed when an abnormal rotation of the screw 3 occurs, even if an adverse effect occurs due to restricting the screw rotation torque T, appropriate error handling can be performed for the adverse effect.

[0021] (5) In a preferred embodiment, as the abnormal rotation of the screw 3, including a state where it is below the lower limit value set for the screw rotation speed R, in particular, appropriate error handling can be performed for adverse effects such as the screw 3 not rotating due to the restriction of the screw rotation torque T.

Brief Description of Drawings

[0022] [Figure 1] A flowchart for explaining the operating state of the plasticization process during production using the plasticization control method according to a preferred embodiment of the present invention, [Figure 2] A configuration diagram of an injection molding machine capable of implementing the plasticization control method, [Figure 3] A block diagram of the control means capable of executing the plasticization control method, [Figure 4] A screen diagram displayed on the display of the molding machine controller used for implementing the plasticization control method, [Figure 5] A screen display diagram of the graphic display unit for graphically displaying the change data according to the plasticization control method, [Figure 6]Another screen display diagram of the graphic display unit that graphically displays change data obtained by the same plasticization control method. [Figure 7] A table listing the mass data of molded products formed by the same plasticization control method. [Figure 8] A diagram showing the screen display of a graphic display unit that graphically displays change data obtained by a conventional plasticization control method. [Figure 9] A list of mass data for molded products formed using conventional plasticization control methods. [Figure 10] A flowchart illustrating the processing procedure of the pre-filling process during production using the plasticization control method according to a preferred embodiment of the present invention. [Figure 11] A flowchart illustrating the processing procedure of the filling and molding process during production using the same plasticization control method. [Figure 12] A screen diagram showing an example of the display shown on the display of the molding machine controller used to implement the plasticization control method. [Figure 13] A diagram showing a pop-up screen displayed on the display of the molding machine controller used to implement the plasticization control method. [Figure 14] A screen diagram showing an example of a change displayed on the display of the molding machine controller used to implement the plasticization control method. [Modes for carrying out the invention]

[0023] Next, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0024] First, the overall main configuration of the injection molding machine M according to this embodiment will be described with reference to Figure 2.

[0025] In Figure 2, M is an injection molding machine, comprising an injection device Mi and a mold clamping device Mc. The injection device Mi is equipped with a heating cylinder 2 having an injection nozzle 2n at its front end and a hopper 2h at its rear end. A screw 3 is inserted inside the heating cylinder 2, and a screw drive unit 23 is provided at the rear end of the heating cylinder 2. The screw drive unit 23 is equipped with an injection cylinder (hydraulic cylinder) 24 that houses a single-rod type injection ram 24r, and the ram rod 24rs protruding forward from the injection cylinder 24 is coupled to the rear end of the screw 3. Furthermore, the shaft of a plasticizing motor (oil motor) 25 attached to the injection cylinder 24 is spline-coupled to the rear end of the injection ram 24r. 26 indicates an injection device moving cylinder that moves the injection device Mi forward and backward to make or release the nozzle from the mold 70. This allows the injection device Mi to touch the injection nozzle 2n to the mold 70 and inject and fill the cavity of the mold 70 with plasticized molten resin.

[0026] On the other hand, the clamping device Mc is a direct-pressure hydraulic clamping device that displaces the movable mold 70m by the drive ram 27r of the clamping cylinder (hydraulic cylinder) 27. This clamping device Mc has a movable platen 30 that is slidably supported by a plurality of tie bars 29... installed between a fixed platen 28 and the clamping cylinder 27, which are fixed in position and spaced apart. The tip of the ram rod 27rs that protrudes forward from the clamping cylinder 27 is fixed to this movable platen 30. A fixed mold 70c is attached to the fixed platen 28, and a movable mold 70m is attached to the movable platen 30. The fixed mold 70c and the movable mold 70m constitute the mold 70. As a result, the clamping cylinder 27 can open and clamp the mold 70.

[0027] Reference numeral 13 denotes a distance measuring sensor, which has the function of detecting the parting gap Cg that occurs between the fixed type 70c and the movable type 70m. The distance measuring sensor 13 described herein is a non-contact type and, as shown in Figure 3, comprises a projection unit 13p installed on the outer surface of the fixed type 70c and a reflecting unit 13r installed on the outer surface of the movable type 70m. By projecting ultrasonic waves or laser light (hereinafter referred to as measurement light) from the projection unit 13p and receiving the measurement light reflected from the reflecting unit 13r, the distance between the projection unit 13p and the reflecting unit 13r, i.e., the parting gap Cg, can be measured.

[0028] On the other hand, in Figure 2, 35 is a hydraulic circuit, which includes a variable discharge type hydraulic pump 36 and a valve circuit 37 that serve as a hydraulic drive source. The hydraulic pump 36 is equipped with a servo motor 39 that serves as a rotation drive source for the hydraulic pump 36. 40 indicates a rotary encoder that detects the rotational speed of the servo motor 39.

[0029] The discharge port of the hydraulic pump 36 is connected to the primary side of the valve circuit 37, and the secondary side of the valve circuit 37 is connected to the injection cylinder 24, plasticizer motor 25, clamping cylinder 27, ejector cylinder 31 (Figure 2), and injection device moving cylinder 26 of the injection molding machine M. Therefore, the valve circuit 37 is equipped with switching valves (solenoid valves) that are connected to the injection cylinder 24, plasticizer motor 25, clamping cylinder 27, ejector cylinder 31, and injection device moving cylinder 26, respectively. Each switching valve is composed of one or more valve components, as well as necessary auxiliary hydraulic components, and has at least a switching function related to the supply, stopping, and discharge of hydraulic fluid to the injection cylinder 24, plasticizer motor 25, clamping cylinder 27, ejector cylinder 31, and injection device moving cylinder 26.

[0030] As a result, by variably controlling the rotational speed of the servo motor 39, the discharge flow rate and discharge pressure of the variable discharge hydraulic pump 36 can be varied. Based on this, drive control can be performed for the injection cylinder 24, plasticizing motor 25, clamping cylinder 27, ejector cylinder 31, and injection device moving cylinder 26, as well as control of each operation process in the molding cycle. Thus, by using a variable discharge hydraulic pump 36 that can set a fixed discharge flow rate by changing the swash plate angle, the pump capacity can be set to a fixed discharge flow rate (maximum capacity) of a predetermined size, and the discharge flow rate and discharge pressure can be varied based on the fixed discharge flow rate, so control by the control system can be easily and smoothly implemented.

[0031] Next, the configuration of the plasticizing control device 1 of the injection molding machine M according to this embodiment will be described with reference to Figures 2-6.

[0032] The plasticization control device 1 includes a molding machine controller 10 as shown in Figure 2, which includes a controller body 15, a display 11, internal memory 16, and a servo amplifier 17 as shown in Figure 3.

[0033] In this case, the controller unit 15 has a computer function that incorporates hardware such as a CPU. The display 11 also includes a display unit 11m and a touch panel 11t attached to the display unit 11m, and the display unit 11m and the touch panel 11t are connected to the controller unit 15 via a display interface 18. Therefore, various setting operations and selection operations can be performed using the touch panel 11t. The display 11 displays various information, in particular the process monitoring screen 61 shown in Figure 4, which relates to the plasticization control method according to this embodiment. This process monitoring screen 61 can be switched by selecting a process monitoring screen switching key 61s.

[0034] As shown in Figure 4, the process monitoring screen 61 is equipped with a graphic display unit 11g that graphically displays change data of various physical operating quantities. At least one or more data points, such as screw position X, screw rotation torque T, and screw rotation speed R, are sent from the controller body 15 to this graphic display unit 11g during the plasticization process, and each data point is graphically displayed. This display function constitutes the plasticization display function unit Fd.

[0035] In this way, when configuring the plasticization control device 1, if a display 11 is provided on the molding machine controller 10, and a plasticization display function unit Fd is provided on this display 11 that graphically displays at least one or more change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process using a graphic display unit 11g, the operating state of the heating cylinder 2 can be visualized, so the operator can easily and quickly grasp the plasticization state of the molten resin.

[0036] Furthermore, the internal memory 16 includes a program area 16p for storing various programs, including control programs (software) for executing various arithmetic and control processes (sequence control), and a data area 16m capable of storing various data (databases). In particular, the programs include a control program (sequence control program) for performing plasticization processing according to the plasticization control method of this embodiment.

[0037] The servo motor 39 described above is connected to the output section of the servo amplifier 17, and the rotary encoder 40 is connected to the encoder pulse input section of the servo amplifier 17. Furthermore, as shown in Figure 2, the valve circuit 37 described above is connected to the control signal output port of the molding machine controller 10, and a pressure sensor 47 for detecting hydraulic pressure and a temperature sensor 48 for detecting oil temperature, as shown in Figure 3, are attached to the primary side of the valve circuit 37, and these pressure sensor 47 and temperature sensor 48 are connected to the control unit 15. In addition, the projection unit 13p of the distance measuring sensor 13 is connected to the sensor support in the controller unit 15.

[0038] As a result, the molding machine controller 10 functions as various functional units for realizing the plasticization control method according to this embodiment, basically as shown in Figure 3, a molding condition setting function unit Fs, a plasticization control function unit Fc, a plasticization display function unit Fd, a normal display function unit Fn, and a graphic display change function unit Fm.

[0039] In this case, as shown in Figure 5, the molding condition setting function unit Fs has the function of setting at least a torque target value Ts for screw rotation torque T and an upper limit value Ru for screw rotation speed R as molding conditions, and the plasticization control function unit Fc has the function of controlling the rotation of screw 3 with respect to the torque target value Ts during the plasticization process. Furthermore, as shown in Figure 4, the plasticization display function unit Fd has the function of graphically displaying at least one or more change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process on the display 11 using the graphic display unit 11g, and as shown in Figure 12, the normal display function unit Fn has the function of graphically displaying at least one or more change data of injection speed V, injection pressure Pp, and mold parting opening Lm during molding. In addition, as shown in Figure 4 as an example of change, the graphic display change function unit Fm has the function of making the normal display function unit Fn and the plasticization display function unit Fd switchable or combinable.

[0040] Next, the operation of the injection molding machine M, including the plasticization control method according to this embodiment, will be specifically described with reference to Figures 1 to 11.

[0041] First, the principle of the plasticization control method according to this embodiment, that is, the verification results of the effectiveness of the plasticization control method, will be explained with reference to Figures 5-9.

[0042] For the verification, a white, rigid PVC (polyvinyl chloride) powdered resin material was used as the molding material. Powdered resin materials are known to be prone to deterioration in material quality due to their properties such as being difficult to adapt to the rotation of screw 3 and having high hygroscopicity. However, in the case of the plasticization control method according to this embodiment, the controllability (moldability) of the plasticization control of the powdered resin material can be improved, thereby preventing discoloration, yellowing (especially yellowing of white materials), burning, etc., of molded products made from powdered resin materials and greatly improving the molding quality. The sample molded product was a large cap component.

[0043] Figures 8 and 9 show data from a conventional control method, specifically, the process of plasticizing the screw 3 from the plasticization start position to a predetermined plasticization end position Xe, where the screw rotation speed R [rpm] (for example, 40 [rpm]) is controlled. Figure 8 is a graphical display of the data changes, and Figure 9 is a table showing data related to the mass [g] of the molded product. As shown in Figure 8, the screw rotation speed R remains almost constant during the plasticization process, and the screw position X recedes approximately proportionally over time. On the other hand, the screw rotation torque T gradually increases from the start of plasticization and then gradually decreases, forming an arc-shaped curve.

[0044] As shown in Figure 9, the number of samples used for verification was "19 samples," and some of the randomly selected samples are shown as change data in Figure 8. As is clear from Figures 8 and 9, it can be confirmed that when using the conventional plasticization control method, the screw rotation torque T can become excessively large, and its variation also becomes large. In the example, as shown in Figure 9, for a product with a standard mass of 3650 [g], the average value was "3647.53 [g]", the maximum value was "3652 [g]", the minimum value was "3645 [g]", the variation range was "7 [g]", the standard deviation was "2.11183 [g]", and the coefficient of variation was "0.34739".

[0045] On the other hand, in the plasticization control method according to this embodiment, a torque target value Ts (example: 20 [MPa]) for the screw rotation torque T and an upper limit value Ru (example: 40 [rpm]) for the screw rotation speed R are set in advance, and the rotation of the screw 3 is controlled with respect to the torque target value Ts during the plasticization process.

[0046] Figures 5 and 7 show data when a plasticization process is performed using the plasticization control method according to this embodiment. Figure 5 is a screen display diagram graphically showing the change data, and Figure 7 is a table showing data related to the mass [g] of the molded product. As shown in Figure 5, the screw rotation speed R initially continues to rotate at the upper limit value Ru, and the screw rotation torque T gradually increases from the start of plasticization, as in the conventional case. Then, when the screw rotation torque T reaches the torque target value Ts, it is limited to this torque target value Ts. Furthermore, as control is performed to limit the screw rotation torque T to the torque target value Ts, the screw rotation speed R decreases in response to this limitation. After this, the screw rotation speed R gradually increases, and when it reaches the upper limit value Ru, it is maintained at the upper limit value Ru, and accordingly, the screw rotation torque T also changes to gradually decrease.

[0047] As shown in Figure 7, the number of samples used for verification was "6 samples," and one of the randomly selected samples is shown as change data in Figure 5. As is clear from Figures 5 and 7, when using the plasticization control method according to this embodiment, the screw rotation torque T is suppressed to the torque target value Ts and does not exceed this value. In the example, as shown in Figure 7, for a product with a standard mass of 3650 [g], the average value was "3651.67 [g]", the maximum value was "3654 [g]", the minimum value was "3650 [g]", the variation range was "4 [g]", the standard deviation was "1.37437 [g]", and the coefficient of variation was "0.22582", confirming that stable molding with little variation is possible.

[0048] In other words, the superiority (effectiveness) of the plasticization control method according to this embodiment compared to conventional control methods was confirmed. In particular, with white molded products, the conventional control method resulted in noticeable yellowing throughout, but with the plasticization control method according to this embodiment, discoloration due to yellowing hardly occurred. Figure 6 is a graphic representation similar to Figure 5, but it shows an example of a molding material in which the screw rotation torque T is not relatively large.

[0049] Next, the specific processing procedure during production using the plasticization control method according to this embodiment will be explained in accordance with the flowcharts shown in Figures 1, 10, and 11, with reference to each figure.

[0050] Figure 1 shows the plasticization process Sa during production, Figure 10 shows the pre-filling process Sb from injection preparation to injection start, and Figure 11 shows the filling and molding process Sc from the start of filling to ejection of the molded product.

[0051] First, a plasticization process is performed in Figure 10 (step Sa). This plasticization process (step Sa) is performed based on the plasticization control method according to this embodiment. The specific processing procedure of the plasticization process is shown in the flowchart of Figure 1.

[0052] In the plasticization process, molding conditions corresponding to the plasticization process are set in advance (step S1). In this case, the setting of molding conditions involves, at least, setting the torque target value Ts [MPa] for the screw rotation torque T (S1a), setting the upper limit value Ru [rpm] for the screw rotation speed R (S1b), and setting the plasticization end position Xe [mm] (S1c), in relation to the plasticization control method according to this embodiment, as well as setting various settings necessary for resin molding, such as temperature and back pressure. These settings can be made by the molding condition setting function unit Fs.

[0053] Meanwhile, in the plasticization process, the plasticization process is performed based on the plasticization control function unit Fc. First, the screw 3 starts rotating due to the plasticization motor 25 in the injection device Mi by switching the valve circuit 37 and controlling the servo motor 39 (step S2). In the initial stage, the molding material is heated by the heated heating cylinder 2, but since almost no shearing occurs due to the rotation of the screw 3, the screw 3 rotates at the upper limit value Ru of the screw rotation speed R (step S3).

[0054] Furthermore, during the plasticization process, the plasticization display function unit Fd displays data on the display 11 shown in Figure 4, showing at least one or more changes in screw position X, screw rotation torque T, and screw rotation speed R, via the graphic display unit 11g. Enlarged views of this graphic display unit 11g are shown in Figures 5 and 6. As the rotation of the screw 3 progresses, shearing gradually occurs, and the screw rotation torque T gradually increases from near zero, as shown in Figures 5 and 6 above. In this case, priority control is performed on the screw rotation torque T (step S4).

[0055] Therefore, if the screw rotation torque T reaches the set torque target value Ts, control is performed to maintain it at the torque target value Ts. Consequently, the screw rotation speed R gradually decreases to maintain the torque target value Ts (steps S5, S6). At this time, the rotational state of the screw 3 is monitored, and if an abnormality in the rotation of the screw 3 occurs, error processing is performed (steps S7, S8). By performing such monitoring, even if any adverse effects occur due to the limitation of the screw rotation torque T, appropriate error processing can be performed for those adverse effects. In this case, if the abnormality in the rotation of the screw 3 is defined as falling below the lower limit value set for the screw rotation speed R, appropriate error processing can be performed, especially for adverse effects such as the screw 3 ceasing to rotate due to the limitation of the screw rotation torque T.

[0056] After this, the plasticization process proceeds, and when screw 3 reaches the predetermined plasticization end position Xe, the rotation of screw 3 is stopped (steps S9, S10). This completes the plasticization process Sa.

[0057] Furthermore, in this plasticization process, unlike typical molding methods, a precise metering step for measuring the resin is not performed. That is, in the injection process, it is sufficient to simply inject the resin until the cavity is filled with resin, so it is enough to measure a slightly larger amount of resin in the metering step. Therefore, although the metering operation of a typical metering process is performed, precise metering control to obtain accurate measurements is unnecessary.

[0058] Therefore, according to the plasticization control method (plasticization control device 1) of this embodiment, as a basic technique, at least a torque target value Ts for the screw rotation torque T and an upper limit value Ru for the screw rotation speed R are set in advance as molding conditions, and the rotation of the screw 3 is controlled with respect to the torque target value Ts during the plasticization process. As a result, the problem of excessively large shear pressure in the plasticization process is eliminated, the occurrence of unnecessary shear heat is suppressed, and variations therein can also be suppressed. This improves the quality of the molten resin, and in particular, the occurrence of discoloration, yellowing, burning, etc. in the molded product is prevented, dramatically improving the molding quality.

[0059] Meanwhile, in Figure 10, upon completion of the plasticization process Sa, the pre-filling process Sb related to injection preparation is performed. In this case, the clamping cylinder 27 of the clamping device Mc is driven by switching the valve circuit 37 and controlling the servo motor 39, and the mold 2 is clamped so that the clamping force becomes the set molding clamping force (steps S21, S22).

[0060] Upon completion of mold clamping, the process related to injection preparation is performed (step S23). This process includes nozzle touch operation and control of the mold temperature. In the nozzle touch operation, the injection device moving cylinder 26 is driven and controlled, and the injection device Mi moves forward to make nozzle contact with the mold 2. In addition, the mold temperature control process is performed so that the mold temperature, which has fluctuated due to mold opening, reaches the normal set temperature. Once these processes related to injection preparation are completed, the injection device Mi enters an injection standby state (steps S24, S25).

[0061] After this, when it is time to start injection, the injection cylinder 24 of the injection device Mi is driven to perform the resin injection process into the mold 70 (steps S26, S27). In this case, the screw 3 should be advanced according to its rated operation. The molding machine controller 10 monitors whether the set reset timing has been reached after the injection standby state of the injection device Mi, and when the reset timing is reached, it performs a zero reset process to reset the distance sensor 13 to zero (step S28).

[0062] With the above steps completed, the pre-filling process Sb is finished, and the process moves on to the filling and molding process Sc. The specific procedure for the filling and molding process Sc is shown in a flowchart in Figure 11. When injection is started at the injection start timing described above, the plasticized and molten resin in the heating cylinder 2 is filled into the cavity of the mold 70 (step S29). As the resin is filled, the injection pressure Pp increases. As it approaches the limit pressure and reaches the limit pressure, control is performed to maintain the pressure at the limit pressure, i.e., control to prevent overshoot, and the injection pressure Pp is maintained at the limit pressure (molding injection pressure) (steps S30, S31). Therefore, effective single-pressure control is performed during the injection operation.

[0063] Furthermore, as the cavity of the mold 70 is filled with resin, the mold 70 is pressurized by the resin, and a parting gap Cg is created between the fixed mold 70c and the movable mold 70m (step S32). This parting gap Cg is generated based on a preset mold clamping force and molding injection pressure.

[0064] Once the injection filling of resin into the mold 70 is complete, the resin solidifies over time, and this solidification process causes natural compression of the resin (step S33). That is, as the volume decreases due to the solidification of the resin, natural compression occurs due to the pressurizing action of the elastic return of the mold 70 (especially the movable mold 70m) to follow this volume reduction. Then, after the set cooling time has elapsed, the clamping cylinder 27 is driven by switching the valve circuit 37 and controlling the servo motor 39, causing the movable mold 70m to retract and the mold to open. At the same time, the ejector cylinder 31 is driven by switching the valve circuit 37 and controlling the servo motor 39 to eject the molded product attached to the movable mold 70m (steps S34, S35). As a result, the molded product is removed, and the filling and molding process Sc is completed.

[0065] If further molding is to be carried out, the plasticization process Sa, pre-filling process Sb, and filling and molding process Sc should be repeated in the same manner, as shown in Figure 10 (steps Sr, Sa, Sb, Sc…).

[0066] On the other hand, Figures 12 and 13 show screen diagrams of examples of displays shown on the display 11 of the molding machine controller 10 in the plasticization control device 1.

[0067] Figure 12 shows the injection / metering settings screen 62 displayed on the display 11. This settings screen 62 can be displayed by selecting the injection / metering screen switching key 62s.

[0068] The injection and metering screen 62 allows various settings related to injection and metering to be made, and the normal waveform display screen 11nn is also displayed. This normal waveform display screen 11nn displays change data for at least one of the following related to injection and metering: injection speed V, injection pressure Pp, and mold parting opening Lm.

[0069] Furthermore, as shown in Figure 12, a changeover switch 50 is provided on the injection / metering screen 62. When this changeover switch 50 is turned ON, a graphic display screen 51 can be displayed as a pop-up, as shown in Figure 13. That is, with the injection / metering screen 62 displayed, a graphic display screen 51 can be displayed as a pop-up, showing at least one change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process.

[0070] Thus, the plasticization display function unit Fd in the molding machine controller 10 has a function that, when switched using a changeover switch 50, pops up a graphic display screen 51 that displays at least one change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process, in addition to the normal waveform display screen 11nn of the display 11 which displays at least one change data of injection speed V, injection pressure Pp, and mold parting opening Lm.

[0071] Therefore, according to the plasticization control method (plasticization control device 1) of the injection molding machine M according to this embodiment, the operating state of the heating cylinder 2 can be visualized from multiple angles, so that the operator can accurately grasp the plasticization state of the molten resin and easily and quickly obtain judgment information for appropriate control of the screw rotation torque T. As a result, the operator can quickly and accurately adjust the molding conditions, etc. Moreover, it becomes possible to easily and accurately grasp the operating state of the entire molding process, which can contribute to reducing defective products and improving mass production efficiency, as well as enabling quick preventive measures against troubles, etc.

[0072] On the other hand, Figure 14 shows an example of a modification to the plasticization display function unit Fd. In this modification example, as shown in Figure 14, the plasticization display function unit Fd is equipped with a graphic display change function unit Fm that can be switched or combined with a normal display function unit Fn that graphically displays at least one or more change data of injection speed V, injection pressure P, and mold parting opening Lm during molding using the normal waveform display unit 11n. As a result, the operator can switch the display as needed to display, on the normal waveform display unit 11n of the display 11, either at least one or more change data of injection speed V, injection pressure Pp, and mold parting opening Lm during molding, or at least one or more change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process, by switching the display, or by combining (overlapping) the display. In this case, by selecting the injection / metering screen switching key 62s, the injection / metering screen 62 can be displayed, which in turn allows the normal waveform display unit 11n to be displayed. The display can be switched using the display switching key (not shown).

[0073] In this way, by enabling the graphic display unit 11g and the normal waveform display unit 11n to be displayed selectively or simultaneously, the operating state during injection and the operating state during plasticization can be compared or checked simultaneously. This makes it possible to take preventative measures against problems or to accurately grasp the operating state of the entire molding process, which can contribute to reducing defective products and improving mass production efficiency.

[0074] Although preferred embodiments, including modified examples, have been described in detail above, the present invention is not limited to these embodiments, and the details of the configuration, shape, quantity, method, etc., can be arbitrarily changed, added, or deleted without departing from the spirit of the present invention.

[0075] For example, while it is desirable to include powdered resin material in the molding material, it is not limited to the shape of the molding material, and can basically be applied to pelletized resin material as well. Furthermore, while it is desirable to monitor the rotation state of the screw 3 and perform error processing when an abnormality in the rotation of the screw 3 occurs, this is not an essential component. It is also desirable to include a state where the rotation abnormality falls below a set lower limit value for the screw rotation speed R, but this does not exclude the possibility of including other rotation abnormalities. In addition, although an example is shown in which all change data of screw position X, screw rotation torque T, and screw rotation speed R during the plasticization process are displayed on the graphic display unit 11g on the display 11, it is also possible to display one or more selected change data of screw position X, screw rotation torque T, and screw rotation speed R, and this does not exclude the possibility of displaying change data of various other physical quantities. On the other hand, although an example using a hydraulic injection device Mi as the injection molding machine M is shown, an electric injection device Mi may also be used. [Industrial applicability]

[0076] The plasticization control method and apparatus according to the present invention can be used in various injection molding machines that have a plasticization step in which a screw is rotated to plasticize the molding material introduced into a heating cylinder. [Explanation of Symbols]

[0077] 1: Plasticization control device, 2: Heating cylinder, 3: Screw, 10: Molding machine controller, 11: Display, 11g: Graphic display unit, 11n: Normal waveform display unit, M: Injection molding machine, Sa: Plasticization process, 70: Mold, T: Screw rotation torque, Ts: Torque target value, R: Screw rotation speed, Ru: Upper limit value, Fs: Molding condition setting function unit, Fc: Plasticization control function unit, Fd: Plasticization display function unit, Fn: Normal display function unit, Fm: Graphic display change function unit

Claims

1. A plasticization control method for an injection molding machine, comprising a plasticization step of plasticizing a molding material introduced into a heating cylinder by controlling the rotation of a screw inserted into the heating cylinder, and injecting the plasticized molten resin into a predetermined mold by controlling the forward movement of the screw, wherein, in advance, at least a torque target value for the screw rotation torque and an upper limit value for the screw rotation speed are set as molding conditions, the rotation of the screw is controlled with respect to the torque target value during the plasticization process, and a graphic display screen showing at least one change data for the screw position, screw rotation torque, and screw rotation speed during the plasticization process is popped up by a switch on a normal waveform display screen that displays at least one change data for the injection speed, injection pressure, and parting opening of the mold during molding, and a switch that displays at least one change data for the screw position, screw rotation torque, and screw rotation speed during the plasticization process.

2. The plasticization control method for an injection molding machine according to claim 1, characterized in that the molding material includes a powdered resin material.

3. The plasticization control method for an injection molding machine according to claim 1 or 2, characterized in that the rotation state of the screw is monitored during the screw rotation of the plasticization process, and error processing is performed when an abnormality in the rotation of the screw occurs.

4. The plasticization control method for an injection molding machine according to claim 3, characterized in that the rotational abnormality includes a state in which the rotational speed falls below a lower limit value set with respect to the screw rotational speed.

5. A plasticization control device for an injection molding machine, comprising a molding machine controller that performs plasticization treatment on a molding material introduced into a heating cylinder by controlling the rotation of a screw inserted into the heating cylinder, and injects and fills a predetermined mold with the plasticized molten resin by controlling the forward movement of the screw, wherein the molding machine controller comprises: a molding condition setting function unit that sets at least a torque target value for the screw rotation torque and an upper limit value for the screw rotation speed as molding conditions; a plasticization control function unit that controls the rotation of the screw with respect to the torque target value during the plasticization treatment; and a plasticization display function unit that, via a switch, pops up a graphic display screen that displays at least one change data of the screw position, screw rotation torque, and screw rotation speed during the plasticization treatment, in addition to the normal waveform display screen of a display that displays change data of at least one change data of the injection speed, injection pressure, and parting opening amount of the mold.

Images