Injection molding method and injection molding apparatus

Abstract

To provide an injection molding method with a stable metering time that is not affected by a type of a resin material or an additive, a state of resin material supply, a molding cycle, etc.SOLUTION: An injection cylinder 10 is zoned from a rear B to a front F into a transport zone FZ, a compression zone CZ, a melting zone MZ, a storage zone KZ and a nozzle zone NZ, each equipped with temperature control means and temperature measurement means. A first temperature pattern is initially set in temperature correcting means 50, a metering time during a metering process is monitored, and when the metering time exceeds a preset monitoring time CT3, temperature correction of the first temperature pattern is performed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an injection molding method in which a predetermined amount of metered resin is stored in an injection cylinder by rotating a screw in a metering process, and the metered resin is injected and filled into a mold cavity by advancing the screw in an injection process.

[0002] Injection molding involves the following steps: First, resin material is fed into the injection cylinder. The shear heat generated by the rotational motion of the spiral-flighted screw and the heat generated by a heater or other device attached to the injection cylinder plasticizes the resin into a molten resin, which is then transported by rotation toward the tip of the screw and stored as a metered resin in the injection cylinder. As the metered resin is stored, the screw retreats, stopping its rotation at a predetermined retreated position to maintain its position (this is called the metering process). Resistance is applied to this screw retreat to adjust the melt-mixing properties of the stored molding material (this is called backpressure control). Next, the screw advances to the injection process, where the metered resin is injected and filled into the mold cavity; the pressure-holding process compensates for the cooling and solidification shrinkage of the molten resin; and the cooling process cools and solidifies the molten resin within the mold cavity. The mold is then opened and the resulting injection-molded product is removed from the mold cavity. This series of molding operations is repeated until the required number of molded products is obtained.

[0003] The quality of injection molding depends heavily on the stability of the resin temperature, which indicates the melting and mixing of the metered resin stored in the metering process, the starting point of the molding operation. This stability is difficult to correct in the subsequent injection and holding processes. The screw speed and metering back pressure control in the metering process affect the resin temperature as shear heat. With the recent trend toward electrification of injection units, it has become possible to precisely adjust the resin temperature. In addition, the temperature control of the injection cylinder is related to the stability of the resin temperature. Therefore, many proposals have been made to stabilize the quality of injection molding by accurately controlling the temperature of the injection cylinder.

[0004] For example, as shown in Patent Document 1, a thermocouple is inserted into the heating barrel (injection cylinder) to measure the temperature change in the heating barrel during the metering process, and the plasticization state is estimated, followed by changes in the state of plasticization factors such as the screw rotation speed and back pressure. Furthermore, a thermocouple is inserted into the nozzle to measure the change in resin temperature for one shot, taking into account shear heat generation as the resin passes through the nozzle during the injection process, and then the heating temperature of the heating barrel, the screw rotation speed, back pressure, etc. are controlled. This makes it possible to accurately grasp the temperature of the resin injected and filled into the mold cavity, thereby always maintaining a good molding state.

[0005] Furthermore, as shown in Patent Document 2, the temperature state near the supply port of the resin material to the heating barrel is detected, and control elements that affect the resin state are variably controlled based on the detected temperature state. The control elements include the amount of resin material supplied, the heating temperature of the heating barrel, the preheating temperature of the resin material, the screw rotation speed, and the back pressure.

[0006] In addition, as shown in Patent Document 3, a temperature sensor is placed in the injection chamber or in the resin flow path connecting the injection chamber and the mold, and changes in resin temperature are measured. The change in resin temperature is then correlated with the time axis of the injection cycle to identify the heating zone that has had the greatest effect on the temperature change, and the temperature of this heating zone is then controlled. This makes it possible to maintain the temperature of the molten resin at an appropriate value. The injection chamber refers to the limited area at the tip of the heating barrel where the metered resin is stored. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 6-55600 [Patent Document 2] Japanese Patent Application Publication No. 4-94915 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-176983 Summary of the Invention [Problem to be solved by the invention]

[0008] As described in Patent Document 1, the temperature of the heating barrel rises due to frictional heat (shear heat) generated by the rotation of the screw during the metering process. This temperature rise is converted into heat quantity, which is then compared with a pre-calculated inflow heat quantity to estimate the plasticization state. Furthermore, measuring the temperature of the resin discharged from the nozzle during the injection process is said to improve the accuracy of the plasticization state estimation. However, the resin material used in injection molding contains additives such as talc and glass fiber within an allowable range, and there is no means of accurately estimating the inflow heat quantity for resin materials containing additives with a wide range of additives. Furthermore, no consideration is given to fluctuations in the temperature and supply rate of the resin material supplied to the heating barrel. In other words, Patent Document 1 makes it difficult to accurately estimate the plasticization state, making it extremely difficult to achieve stable injection molding quality.

[0009] In response to this, Patent Document 2 proposes detecting temperature changes in the resin material supplied to the heating barrel and variably controlling control elements that affect the resin state, which is expected to stabilize the plasticized and molten state of the metered resin. However, no consideration is given to the heating barrel beyond the resin material supply port. As mentioned above, resin materials often contain additives, and depending on the type of additive, such as glass fiber or carbon fiber, which have very high melting points, or a mixture of two resin materials with different melting points, these can significantly affect the plasticized and molten state of the resin material. Therefore, Patent Document 2 makes it difficult to accurately grasp the plasticized state and stabilize the molten state of the metered resin, and does not ensure stable injection molding quality.

[0010] Furthermore, as shown in Patent Document 3, the temperature of the metered resin stored in the injection chamber changes depending on the elapsed time (molding cycle) between the end of the injection process and the start of the next injection process, eventually approaching the set temperature of the injection chamber. If the metering time during the metering process changes, resulting in a change in the molding cycle, the temperature of the metered resin also changes accordingly. Furthermore, installing a temperature sensor inside the injection chamber is not practical due to interference with the screw. Installing a temperature sensor on the injection chamber wall reduces the accuracy of resin temperature measurement, making accurate resin temperature measurement impossible. Furthermore, installing a temperature sensor in the flow path connecting the injection chamber and the mold would subject the temperature sensor to shear heating due to the resin flow during the injection process, making accurate resin temperature measurement impossible. In other words, it is unrealistic to infer the plasticization state of the resin material passing through each zone of the heating barrel during the metering process from changes in the resin temperature in the injection chamber during the injection process due to unstable factors.

[0011] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an injection molding method with a stable metering time that is not affected by the type of resin material or additive, the supply state of the resin material, the molding cycle, etc. [Means for solving the problem]

[0012] The injection molding method of the present invention comprises: An injection molding method comprising: storing a predetermined amount of metered resin in an injection cylinder by rotating a screw in a metering step; and injecting and filling the metered resin into a mold cavity by advancing the screw in an injection step; The injection cylinder is divided into zones, from rear to front, including a transport zone, a compression zone, a melting zone, a storage zone, and a nozzle zone, each of the zones being provided with a temperature adjusting means and a temperature measuring means, and a first temperature pattern corresponding to the zone division is initially set in the temperature correcting means; The temperature correction means operates the temperature adjustment means based on the temperature measured by the temperature measurement means, based on the first temperature pattern, to control the heating of the injection cylinder, monitors the measurement time during the measurement process, and performs temperature correction of the first temperature pattern when the measurement time exceeds a preset monitoring time.

[0013] In the injection molding method of the present invention, Preferably, the temperature correction involves calculating the limit number of shots when the metering time exceeds the monitoring time, determining the upper limit temperature of the compression zone measured by the temperature measurement means when the limit number of shots is reached, setting the difference between the reference temperature of the first temperature pattern and the upper limit temperature as a first temperature change amount, setting the upper limit temperature as a new set temperature for the compression zone, adding the first temperature change amount to the set temperature of the transport zone as a new set temperature for the transport zone, and resetting this as a second temperature pattern in the temperature correction means.

[0014] In addition, in the injection molding method of the present invention, Preferably, the temperature correction involves calculating the limit number of shots when the metering time exceeds the monitoring time, determining the upper limit temperature of the compression zone measured by the temperature measurement means when the limit number of shots is reached, setting the upper limit temperature as the new set temperature for the compression zone and the transport zone, and resetting it in the temperature correction means as a third temperature pattern.

[0015] Furthermore, in the injection molding method of the present invention, Preferably, the temperature correction involves calculating the limit number of shots when the metering time exceeds the monitoring time, determining the upper limit temperature of the compression zone measured by the temperature measuring means when the limit number of shots is reached and the lower limit temperature of the transport zone measured by the temperature measuring means when the limit number of shots is reached, determining a provisional temperature pattern using the upper limit temperature as the new set temperature for the compression zone and the transport zone, and further setting the difference between the set temperature of the transport zone in the first temperature pattern and the lower limit temperature as a second temperature change amount, adding the second temperature change amount to the set temperature of the transport zone in the provisional temperature pattern as the new set temperature for the transport zone, and resetting this as a fourth temperature pattern in the temperature correction means.

[0016] In addition, in the injection molding method of the present invention, It is preferable that the temperature correction means controls heating of the injection cylinder based on the fourth temperature pattern, and issues an alarm when it is determined that the measurement time does not converge within the range of the monitoring time. [Effects of the Invention]

[0017] According to the present invention, an injection molding method can be provided that has a stable metering time, unaffected by the type of resin material or additive, the supply state of the resin material, the molding cycle, etc. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a conceptual diagram of an injection device used in injection molding according to an embodiment of the present invention. [Figure 2] FIG. 1 is a flow diagram showing an injection molding method according to an embodiment of the present invention. [Figure 3] FIG. 10 shows the change in CZ measurement temperature with metering time during a production shot. [Figure 4] 1A and 1B are diagrams illustrating a first embodiment and a second embodiment of the present invention. [Figure 5] FIG. 10 is a diagram showing a third embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0019] Preferred embodiments for carrying out the present invention will be described below with reference to the drawings. Note that the following embodiments do not limit the inventions according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solutions of the inventions according to the claims. Furthermore, in the present embodiments, the scales and dimensions of each component may be exaggerated, and some components may be omitted.

[0020] [Injection device] First, an injection apparatus used for injection molding according to an embodiment of the present invention will be described with reference to FIG. 1. In the following description, a horizontal injection molding machine will be used as the injection apparatus according to the embodiment of the present invention, but the present invention is not limited thereto. The injection apparatus 100 shown in FIG. 1 includes a cylindrical injection cylinder 10, a screw 20 disposed within the injection cylinder 10, an injection drive unit 30, an injection control unit 40, and a temperature correction means 50. The injection control unit 40 controls the rotation and forward / backward movement of the screw 20 by operating the injection drive unit 30. Furthermore, a drive unit (not shown) or the like controls the connection and separation between the injection apparatus 100 and an injection mold 80, and the screw 20 is in the connected state during injection molding. Regarding the movement of the screw 20, the direction toward the injection mold 80 is defined as forward F, movement toward the forward F as forward movement, the direction away from the injection mold 80 as backward B, and movement toward the backward B as backward movement.

[0021] The injection cylinder 10 is equipped with a material hopper 12 on the rear side B, and resin material is supplied from the material hopper 12 into the injection cylinder 10 by a material supply device (not shown). The injection cylinder 10 is equipped with a nozzle 13 on the front side F, which is connected to a resin flow path 83 of the injection molding die 80. The resin flow path 83 is connected to a mold cavity 84 formed by clamping a fixed die 81 and a movable die 82. The resin flow path 83 is heated and maintained at a predetermined temperature and is equipped with a means for opening and closing the flow path in response to the injection molding operation. If the resin flow path 83 does not have a means for opening and closing the flow path, it is preferable to provide an opening and closing means on the nozzle 13 of the injection device 100. This prevents leakage of resin material when the resin flow path 83 and the nozzle 13 separate. Furthermore, the metering process can be performed simultaneously with other molding processes, such as the opening and closing of the injection molding die 80, greatly contributing to shortening the injection molding cycle. If these advantages are not desired, the opening and closing means of the flow path may be omitted.

[0022] The screw 20 has a spiral flight 22 that spirals from the rear B toward the front F. The spiral direction and angle of the flight 22 are set relative to the rotation direction of the screw 20 so that the resin material supplied from the material hopper 12 can be rotated and transported toward the front F. As shown in FIG. 1, the flight 22 is arranged in a single row at a fixed interval and a fixed angle, but this is not limited to this. For example, the interval and angle may be variable, or multiple flights may be arranged. Alternatively, the flights 22 may be arranged in a multiple row only in a portion of the screw 20.

[0023] The screw 20 is conical in shape, with its diameter gradually increasing from the rear B to the front F. In other words, the volume of the gap between the screw 20 and the injection cylinder 10 gradually decreases from the rear B to the front F, and is configured to have, for example, a transport zone, a compression zone, and a melting zone. As a result, the resin material (solid material) supplied from the material hopper 12 is transported forward by the rotation of the screw 20 and the flight 22 (transport zone). The reduction in volume causes compression and shear heating to act on the resin material (compression zone). The combined effect of the heat provided by the heater 12 causes the resin to melt gradually (referred to as plasticization), and molten resin is generated toward the front F of the screw 20 (melting zone). The generated molten resin passes through a flow path in a backflow prevention device 23 located at the tip of the screw 20 and a screw head 24, and is stored toward the front F of the injection cylinder 10 (referred to as metered resin). As the amount of metered resin increases, the screw 20 retreats to the rear B side, stops rotating at a predetermined retreated position, and maintains that stopped position (this is called the metering process). This retreating movement of the screw 20 is restricted (called metering back pressure) to adjust the melting and mixing properties of the metered resin (this is called back pressure control). In the injection process, the screw 20 is advanced, and the metered resin, including the resin remaining in the nozzle 13, is injected and filled toward the injection molding die 80. In this injection process, the flow path in the backflow prevention device 23 is closed.

[0024] Here, for example, in the case of automotive interior parts, resin materials used in injection molding typically include thermoplastic resins such as polypropylene (PP) resin and polyethylene (PE) resin, with the addition of colorants such as black, red, and blue to adjust the color tone of the part. Various additives are also used, such as plasticizers that impart flexibility to thermoplastic resins, nucleating agents and clarifying agents that control the crystallinity of crystalline resins, flame retardants that inhibit combustion, antistatic agents that suppress static electricity buildup, lubricants that improve fluidity and mold release, weatherproofing agents and UV inhibitors that inhibit degradation due to ultraviolet light, and reinforcing agents such as glass fiber and carbon fiber. Other suitable thermoplastic resins include general-purpose resins such as polypropylene (PP) resin and polyethylene (PE) resin, engineering resins such as polyamide (PA) resin and polycarbonate (PC) resin, and super-engineering resins such as polyphenylene sulfide (PPS) resin and polyether ether ketone (PEEK) resin. Thermoplastic resins and additives are collectively referred to as resin materials. Thermosetting resins such as phenolic (PF) resin and melamine (MF) resin may also be used instead of thermoplastic resins.

[0025] [Temperature control means, temperature measurement means, and temperature correction means] Next, the temperature adjusting means and temperature measuring means of the injection device according to the embodiment of the present invention will be described with reference to FIG.

[0026] The injection cylinder 10 is divided into zones, from the rear B to the front F, into a transport zone FZ, a compression zone CZ, a melting zone MZ, a storage zone KZ, and a nozzle zone NZ. The transport zone FZ, compression zone CZ, and melting zone MZ correspond to the respective zones of the screw 20. The storage zone KZ is the area where the metered resin is stored, and the nozzle zone NZ is the location of the nozzle 13. Each of the zones is provided with a temperature adjustment means (FHH, CHH, MHH, KHH, NHH) such as a heater, and is connected to a temperature correction means 50 for individual temperature adjustment. Each of the zones is also provided with a temperature measurement means (FH, CH, MH, KH, NH) such as a thermocouple, and is connected to a temperature correction means 50 for individual temperature measurement. The temperature correction means 50 controls the temperature of each of the temperature adjustment means (FHH, CHH, MHH, KHH, NHH) so that the measured temperatures measured by the temperature measurement means (FH, CH, MH, KH, NH) match with each set temperature of the temperature pattern of the injection cylinder 10.

[0027] The temperature correction means 50 is also connected to the injection control unit 40, and receives data on the metering time of the metering process to determine whether temperature correction is necessary for the injection cylinder 10. If the temperature correction means 50 determines that temperature correction is necessary for the temperature pattern set in the injection cylinder 10, it performs the temperature correction based on the temperatures measured by the temperature measurement means (FH, CH, MH, KH, NH). This will be explained in detail in the injection molding method described below. The temperature measurement data from the temperature measurement means (FH, CH, MH, KH, NH) is also transferred from the temperature correction means 50 to the injection control unit 40, and is used for safety measures such as cold start prevention, which allows the screw 20 to start rotating or moving forward and backward at the start of injection molding.

[0028] 1 shows one circuit for the temperature adjusting means and temperature measuring means for each zone of the injection cylinder 10, but the present invention is not limited to this. For example, two or more circuits may be provided for each zone, or the number of circuits may be increased for only specific zones. In particular, it is preferable to increase the number of circuits for the transport zone FZ or compression zone CZ, which are considered to have a large effect on the plasticization and melting of the resin material supplied to the injection cylinder 10. Furthermore, the injection cylinder 10 may be entirely or partially surrounded by a heat insulating cover or the like together with the temperature adjusting means, and a cooling means such as an air-cooled fan may be provided to locally cool the injection cylinder 10.

[0029] [Injection molding method] Next, an injection molding method according to an embodiment of the present invention will be described with reference to Figures 2 to 5. Figure 2 shows a flow diagram of the injection molding method, and Figure 3 shows the change in measurement time and measured temperature by the temperature measurement means with respect to the temperature pattern of the injection cylinder 10. Also, Figure 4 shows first and second embodiments of temperature correction, and Figure 5 shows a third embodiment of temperature correction.

[0030] 2, a temperature pattern for the injection cylinder 10 is selected based on the type of resin material and additives used, product weight, number of shots for mass production, metering conditions such as screw rotation speed and back pressure, target molding cycle including metering time, past mass production results, etc., and is initially set as a first temperature pattern in the temperature correction means 50. The temperature correction means 50 controls the heating of the injection cylinder 10 by operating the temperature adjustment means (FHH, CHH, MHH, KHH, NHH) based on the temperatures measured by the temperature measurement means (FH, CH, MH, KH, NH) in accordance with the first temperature pattern.

[0031] An example of the first temperature pattern is shown in Figure 3(a). While it is common for the set temperatures of all zones of the injection cylinder 10 to be set to a reference temperature TK, in Figure 3(a), only the transport zone FZ is set to a preheat temperature TF lower than the reference temperature TK. This is based on the role of the transport zone FZ: to preheat the resin material (solid material) supplied from the material hopper 12 while transporting it to the compression zone CZ without melting it. Melting the resin material in this transport zone FZ is undesirable because it can reduce the transport capacity to the compression zone CZ. Furthermore, if there is a risk of molten resin leaking from the nozzle 13 when the nozzle 13 and the injection mold 80 are separated, the set temperature of the nozzle zone NZ may be set lower than the reference temperature TK. In this way, the first temperature pattern of the injection cylinder 10 selects the optimal temperature setting depending on the situation. The reference temperature TK is the target temperature of the metered resin to be injected and filled into the mold cavity 84, and this target temperature determines factors related to the quality of the injection molding, such as the amount of cooling, solidifying, and shrinkage of the metered resin injected and filled.

[0032] The injection cylinder 10 is heated and controlled to the first temperature pattern, and resin material is supplied from the material hopper 12 to start the metering process of injection molding. During the metering process, the temperature changes in each zone (FZ, CZ, MZ, KZ, NZ) are measured by temperature measurement means (FH, CH, MH, KH, NH) and stored in the temperature correction means 50. It is also possible to prioritize measurement of temperature changes in the compression zone CZ and the transport zone FZ, which are believed to have a significant impact on the plasticization and melting of the resin material. Here, we will focus on and explain in detail the temperature measurements in the compression zone CZ and the transport zone FZ.

[0033] During the metering process, the metering time is also measured and stored in the temperature correction unit 50. Figure 3(b) shows the relationship between the number of injection molding shots and the metering time. If the first temperature pattern is appropriate, the metering time stabilizes near the target metering time CT, as indicated by the dashed line at CT1. If the first temperature pattern is inappropriate, the metering time increases with the number of production shots, as indicated by the solid line at CT2. This is due to a gradual decrease in the degree of plasticization and melting of the resin material in the compression zone (CZ). For example, with resin materials containing reinforcing additives such as glass fiber, which have a very high melting point, or resin materials such as polyethylene resin, which require a large amount of heat for melting, this is thought to be due to insufficient preheating in the transport zone (FZ) or the accumulation of insufficient heat in the compression zone (CZ). Furthermore, if the resin material supplied to the injection cylinder 10 is cold, heat is removed from the transport zone (FZ) or compression zone (CZ), further exacerbating the heat deficiency.

[0034] Here, the critical metering time that affects the molding cycle is defined as the monitoring time CT3, and the number of production shots at the point when the monitoring time CT3 is exceeded is defined as the limit number of shots N1. Furthermore, in the first temperature pattern, in which the metering time increases with the number of production shots, the compression zone temperature TCZ measured by the temperature measurement device CH in the compression zone CZ also increases, as shown in Figure 3(c). This is because the extended metering time increases the time it takes for the resin material to plasticize and melt and pass through the compression zone CZ due to shear heating caused by the rotational movement of the screw 20. In other words, this indicates that the resin material is clogged in the compression zone CZ, causing a longer rotation time (called idle rotation). This idle rotation generates excessive shear heating, resulting in localized heating of the compression zone CZ of the injection cylinder 10. Furthermore, because the temperature is higher than in the first temperature pattern, the temperature adjustment device CHH becomes uncontrollable, and the state of plasticization and melting is also uncontrollable. As a result, the metered resin is produced in a completely uncontrolled melt-kneaded state. The compression zone temperature TCZ when the limit number of shots N1 is reached is defined as the upper limit temperature TCH. The difference between the upper limit temperature TCH and the reference temperature TK is defined as the temperature change amount T1.

[0035] Returning to the explanation of FIG. 2, the temperature correction means 50 begins temperature correction for the first temperature pattern when it confirms that the measurement time of the measurement process has exceeded the monitoring time CT3. Temperature correction is performed in three steps, Step 1 to Step 3. First, in temperature correction Step 1, the limit number of shots N1 when the measurement time exceeds the monitoring time CT3 is calculated. The upper limit temperature TCH of the compression zone CZ measured by the temperature measurement means CH when the limit number of shots N1 is reached is determined. The difference between the reference temperature TK and the upper limit temperature TCH of the first temperature pattern is set as the first temperature change amount T1. The upper limit temperature TCH is then set as the new set temperature CH2 for the compression zone CZ (CH2 = TCH). Furthermore, the temperature obtained by adding the first temperature change amount T1 to the set temperature FH1 (FH1 = TF) of the transport zone FZ of the first temperature pattern is set as the new set temperature FH2 for the transport zone FZ (FH2 = FH1 + T1). This set temperature (CH2, TF2) is then reset to the temperature correction means 50 as the second temperature pattern. The second temperature pattern after the resetting is shown in FIG. 4(a).

[0036] The temperature correction means 50 controls the heating of the injection cylinder 10 by operating the temperature adjustment means (FHH, CHH, MHH, KHH, NHH) based on the temperatures measured by the temperature measurement means (FH, CH, MH, KH, NH) in accordance with the second temperature pattern, and continues injection molding. Note that interrupting the injection molding operation for temperature correction may alter the state of the temperature change in the injection cylinder 10. Therefore, it is preferable to continue injection molding by, for example, performing a trial run until the heating control of the injection cylinder 10 according to the reset second temperature pattern stabilizes. When the injection cylinder 10 is heated and controlled according to the second temperature pattern and the metering time falls within the monitoring time CT3 (metering time ≦ monitoring time CT3), the temperature correction of the injection cylinder 10 is completed, and injection molding continues in this state. If the metering time does not converge within the monitoring time (metering time > monitoring time CT3), the process proceeds to temperature correction step 2.

[0037] Next, in temperature correction step 2, the limit number of shots N1 when the metering time exceeds the monitoring time CT3 is calculated, and the upper limit temperature TCH of the compression zone CZ measured by the temperature measurement means CH when the limit number of shots N1 is reached is determined. This upper limit temperature TCH is set as the new set temperatures for the compression zone CZ and the transportation zone FZ (CH3 = TCH, FH3 = TCH), and is reset in the temperature correction means 50 as the third temperature pattern. Here, the second temperature pattern corrects the set temperatures (FH2, CH2) of the transportation zone FZ and the compression zone CZ to higher temperatures and increases the amount of heat from the temperature adjustment means (FHH, CHH) to help plasticize and melt the resin material supplied from the material hopper 12. For example, if a large amount of resin is set to be metered and a large amount of resin material is supplied, the second temperature pattern may not provide enough heat. Therefore, the third temperature pattern is set to temperatures (FH3, CH3) that further increase the amount of heat from the temperature adjustment means (FHH, CHH), completely eliminating the lack of heat required to plasticize and melt the resin material. As a result, the resin material can pass through the compression zone CZ more easily, and a significant reduction in metering time is expected. The third temperature pattern after resetting is shown in Figure 4(b).

[0038] The temperature correction means 50 controls the heating of the injection cylinder 10 by operating the temperature adjustment means (FHH, CHH, MHH, KHH, NHH) based on the temperatures measured by the temperature measurement means (FH, CH, MH, KH, NH) according to the third temperature pattern, and continues injection molding in the same manner as with the second temperature pattern. The injection cylinder 10 is controlled for heating according to the third temperature pattern, and when the metering time falls within the range of the monitoring time CT3 (metering time ≦ monitoring time CT3), the temperature correction of the injection cylinder 10 is completed, and injection molding continues in this state. If the metering time does not converge within the range of the monitoring time (metering time > monitoring time CT3), the process proceeds to temperature correction step 3.

[0039] The temperature change in the transport zone FZ is shown in Figure 5(a). Due to the temperature rise in the compression zone temperature TCZ in the compression zone CZ, the transport zone temperature TFZ1 (shown by the dashed line) generally rises slightly above the preheat temperature TF in the first temperature pattern. Conversely, as the transport zone temperature TFZ2 (shown by the solid line) decreases with increasing production shot count, the temperature may decrease. This is thought to be due to the loss of heat from the temperature control unit FHH in the transport zone FZ, especially when using a resin material with a high specific heat capacity, such as polyethylene resin. It has also been confirmed that this occurs when a large amount of unpreheated resin material is supplied, especially in winter when the outside temperature drops, resulting in excessive cooling of the transport zone FZ. Under these conditions, a temperature pattern that maximizes the preheating effect on the resin material in the transport zone FZ is desirable.

[0040] Therefore, temperature correction step 3 targets the case of the transport zone temperature TFZ2, which decreases as the number of production shots increases. Specifically, the limit number of shots N1 is calculated when the measurement time exceeds the monitoring time CT3, and the upper limit temperature TCH of the compression zone CZ measured by the temperature measurement device CH when the limit number of shots N1 is reached is calculated. Furthermore, the lower limit temperature TFL of the transport zone FZ measured by the temperature measurement device FH when the limit number of shots N1 is reached is calculated. First, a provisional temperature pattern is set using the upper limit temperature TCH as the new set temperature for the compression zone CZ and the transport zone FZ. Furthermore, the difference between the set temperature FH1 of the transport zone FZ in the first temperature pattern and the lower limit temperature TFL is set as the second temperature change T2. The temperature obtained by adding the second temperature change T2 to the set temperature (TCH) of the transport zone FZ in the provisional temperature pattern is set as the new set temperature FH4 for the transport zone FZ (FH4 = TCH + T2). Furthermore, the upper limit temperature TCH is set as a new set temperature CH4 for the compression zone CZ (CH4=TCH), and is reset as a fourth temperature pattern in the temperature correction means 50. The reset fourth temperature pattern is shown in FIG. 5(b).

[0041] The temperature correction means 50 controls the heating of the injection cylinder 10 by operating the temperature adjustment means (FHH, CHH, MHH, KHH, NHH) based on the temperatures measured by the temperature measurement means (FH, CH, MH, KH, NH) according to the fourth temperature pattern, and continues injection molding in the same manner as with the second or third temperature pattern. The injection cylinder 10 is controlled to be heated according to the fourth temperature pattern, and when the metering time falls within the monitoring time CT3 (metering time ≦ monitoring time CT3), the temperature correction of the injection cylinder 10 is completed, and injection molding continues in this state. If the metering time does not converge within the monitoring time (metering time > monitoring time CT3), it is determined that improvement through temperature correction is difficult, and an alarm is issued, injection molding is interrupted as necessary, and other correction processing is performed.

[0042] Other correction methods include, for example, rescheduling the target molding cycle to a longer time and increasing the heat load time in the transport zone (FZ) and compression zone (CZ). Alternatively, the heat load time can be increased by slowing the screw rotation speed and lengthening the metering time. Setting the screw rotation speed at a slower speed may reduce the degree of shear heat generated by the screw rotation. In this case, the back pressure may be increased to compensate for the reduced shear heat. These correction methods tend to lengthen the metering time and molding cycle, potentially resulting in reduced productivity. While replacing the resin material with one that is more easily plasticized and melted can be an easy solution, changing the type of resin material is difficult in practice due to the required physical properties of injection-molded products. In such cases, reducing the pellet size of the resin material can significantly improve the plasticization and meltability. Setting a higher temperature during the preheating process of the resin material is also effective. Resin material correction methods can also be expected to shorten the metering time and molding cycle. Furthermore, it is necessary to take into consideration fundamental correction measures such as replacing the screw 20 with one having a different shape or replacing the injection device 100 with one having a larger capacity injection cylinder 10.

[0043] In addition, the second to fourth temperature patterns have higher set temperatures (FH2 to FH4) for the transport zone FZ than the first temperature pattern. If, for example, the injection molding operation is temporarily interrupted under these conditions, the resin material remaining in the transport zone FZ may melt. Therefore, before the operation is temporarily interrupted, it is preferable to discharge the resin material from at least the transport zone FZ, preferably including the compression zone CZ (this is called a purging operation). Furthermore, if the interruption lasts for a long period of time, the fourth temperature pattern should be changed back to the third temperature pattern, the second temperature pattern, or preferably the first temperature pattern. Furthermore, when the injection molding operation is resumed, the heating of the injection cylinder 20 is controlled based on the temperature pattern immediately before the interruption, ensuring stable operation of high-quality injection molding.

[0044] [effect] In this way, during continuous injection molding operations, the injection cylinder temperature is corrected when the metering time exceeds the monitoring time. This temperature correction is a simple process of resetting the initial temperature pattern based on the measured temperature of the injection cylinder. This effectively preheats the resin material supplied from the material hopper to the injection cylinder, stabilizing the plasticized and molten state of the resin material and producing a uniformly melted and mixed metered resin. As a result, stable metering times and high-quality injection molding can be ensured, regardless of the resin material, the type and amount of additives, the resin material supply status, or the molding cycle.

[0045] Although the preferred embodiments of the present invention have been described above, the technical scope of the present invention is not limited to the scope described in the above-described embodiments. Various modifications and improvements can be made to the above-described embodiments. [Explanation of symbols]

[0046] 100 Injection device 10 injection cylinder 12 Material hopper 13 nozzles 20 screws 22 flights 23 Backflow prevention device 24 screw head FZ Transportation Zone CZ Compression Zone MZ Melting Zone KZ Storage Zone NZ Nozzle Zone 30 Injection drive unit 40 Injection control unit 50 Temperature compensation means 80 injection molds 81 Fixed mold 82 Movable mold 83 Resin flow path 84 mold cavity F forward B Back TK reference temperature TF preheat temperature TCZ Compression Zone Temperature CT target weighing time CT3 monitoring time N1 Maximum number of shots T1 First temperature change T2 Second temperature change TCH upper limit temperature TFL lower limit temperature CT1, CT2 measurement time TFZ1, TFZ2 transport zone temperature FHH, CHH, MHH, KHH, NHH Temperature adjustment means FH, CH, MH, KH, NH Temperature measurement means CH2~CH4 Compression Zone Setting Temperature FH1~FH4 Transport Zone Temperature Settings

Claims

1. In the metering process, a predetermined amount of metered resin is stored in the injection cylinder by the rotation of the screw. In an injection molding method, the metered resin is injected and filled into a mold cavity by the forward movement of the screw in an injection step, the injection cylinder is divided into zones, from rear to front, into a transport zone, a compression zone, a melting zone, a storage zone, and a nozzle zone, each of the zones is provided with a temperature adjusting means and a temperature measuring means, and a first temperature pattern corresponding to the zone division is initially set in the temperature correcting means; the temperature correction means operates the temperature adjustment means based on the temperature measured by the temperature measurement means, based on the first temperature pattern, to perform heating control of the injection cylinder, monitors a measurement time during the measurement process, and when the measurement time exceeds a preset monitoring time, performs temperature correction of the first temperature pattern; The temperature correction calculates a limit number of shots when the measurement time exceeds the monitoring time, an upper limit temperature of the compression zone measured by the temperature measuring means when the limit number of shots is reached, and a difference between the reference temperature of the first temperature pattern and the upper limit temperature is defined as a first temperature change amount; the upper limit temperature is set as a new set temperature for the compression zone, and the temperature obtained by adding the first temperature change amount to the set temperature in the first temperature pattern for the transport zone is set as the new set temperature for the transport zone, and this is reset in the temperature correction means as a second temperature pattern.

2. The temperature correction calculates a limit number of shots when the measurement time exceeds the monitoring time, 2. The injection molding method according to claim 1, further comprising the steps of: determining an upper limit temperature of the compression zone measured by the temperature measuring means when the limit number of shots is reached; setting the upper limit temperature as a new set temperature for the compression zone and the transport zone; and resetting the third temperature pattern in the temperature correcting means.

3. The temperature correction calculates a limit number of shots when the measurement time exceeds the monitoring time, 2. The injection molding method according to claim 1, further comprising: determining an upper limit temperature of the compression zone measured by the temperature measuring means when the limit number of shots is reached; and determining a temporary temperature pattern using the upper limit temperature as a new set temperature for the compression zone and the transport zone; determining a second temperature change amount as the difference between the set temperature of the transport zone in the first temperature pattern and the lower limit temperature; and setting the temperature obtained by adding the second temperature change amount to the set temperature of the transport zone in the temporary temperature pattern as the new set temperature for the transport zone; and resetting the temperature correction means as a fourth temperature pattern.

4. 4. The injection molding method according to claim 3, wherein the temperature correcting means controls heating of the injection cylinder based on the fourth temperature pattern, and issues an alarm when it is determined that the metering time does not converge within the range of the monitoring time.

5. An injection cylinder which is zoned from rear to front into a transport zone, a compression zone, a melting zone, a storage zone, and a nozzle zone, and is rotatably disposed on a screw; a temperature adjusting means and a temperature measuring means provided in each of the zone classifications; a temperature correction means for initially setting a first temperature pattern according to the zone classification, In the metering step, a predetermined amount of metered resin is stored in the injection cylinder by the rotation of the screw; An injection molding apparatus in which the metered resin is injected and filled into a mold cavity by the forward movement of the screw in an injection step, the temperature correction means operates the temperature adjustment means based on the temperature measured by the temperature measurement means, based on the first temperature pattern, to perform heating control of the injection cylinder, monitors a measurement time during the measurement process, and when the measurement time exceeds a preset monitoring time, performs temperature correction of the first temperature pattern; The temperature correction calculates a limit number of shots when the measurement time exceeds the monitoring time, an upper limit temperature of the compression zone measured by the temperature measuring means when the limit number of shots is reached, and a difference between the reference temperature of the first temperature pattern and the upper limit temperature is defined as a first temperature change amount; the upper limit temperature is set as a new set temperature for the compression zone, and the temperature obtained by adding the first temperature change amount to the set temperature in the first temperature pattern for the transport zone is set as the new set temperature for the transport zone, and this is reset in the temperature correction means as a second temperature pattern.

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