Injection molding machine

Abstract

The invention provides an injection molding machine capable of manufacturing a high-quality molded body with high yield. The injection molding machine includes: a cylinder having a nozzle for injecting molten resin into a mold; a screw configured to advance and retreat within the cylinder; the heater is arranged on the periphery of the nozzle; and a control device for controlling the advancing and retreating of the screw and the operation of the heater. In a molding cycle, the control device causes the heater to operate at a predetermined current value to heat the nozzle during a predetermined period in a partial injection process in which the molten resin is injected into the mold by advancing the screw.

Description

Technical Field

[0001] This invention relates to an injection molding machine that produces molded articles by injecting molten resin into a mold. Background Technology

[0002] Patent Document 1 (Japanese Patent Application Publication No. 2006-192646) discloses an injection molding machine for producing molded articles by injecting molten resin into a mold. The injection molding machine includes: a nozzle mounted on the top of a heating cylinder; and a heater wound around and mounted on the nozzle. In this injection molding machine, during a predetermined process period in the molding cycle, specifically during the mold-closing process, the heater is heated only for a predetermined time and with a predetermined current value. By maintaining a constant amount of heat supplied to the nozzle by the heater throughout each molding cycle, high-quality molded articles can be produced. Summary of the Invention

[0003] To improve the yield of molded products, we expect to further improve the quality of the molded products.

[0004] In view of the above, one of the objectives of the present invention is to provide an injection molding machine that can produce high-quality molded parts with high yield.

[0005] The inventors conducted in-depth research on the above-mentioned problems, and the results showed that during the injection process in the molding cycle, the injection pressure of the molten resin from the nozzle is easily disturbed, which affects the quality of the molded product. Based on these research results, the inventors completed the injection molding machine of the present invention, as shown below.

[0006] An injection molding machine according to one aspect of the present invention comprises: a cylinder having a nozzle for injecting molten resin into a mold; a screw configured to move forward and backward within the cylinder; a heater disposed on the outer periphery of the nozzle; and a control device for controlling the forward and backward movement of the screw and the operation of the heater. During the molding cycle, the control device, by advancing the screw, activates the heater with a predetermined current value during a predetermined period of the partial injection process in which the molten resin is injected into the mold, thereby heating the nozzle.

[0007] The injection molding machine of the present invention can produce high-quality molded parts with high yield. Attached Figure Description

[0008] Figure 1 This is a schematic structural diagram of the injection molding machine involved in Embodiment 1.

[0009] Figure 2 yes Figure 1 An enlarged cross-sectional view of the area near the nozzle in an injection molding machine.

[0010] Figure 3 It is shown Figure 1 A schematic structural diagram of an example of an input device is shown.

[0011] Figure 4 This is an explanatory diagram illustrating the processes that constitute the molding cycle.

[0012] Figure 5 This is an explanatory diagram illustrating the specified period during which the heater used to heat the nozzle performs its operation in an injection molding process.

[0013] Figure 6 This is a graph showing the change in resin injection pressure from the nozzle when the heater operation is controlled by PID (Proportional-Integral-Differential Controller) in an injection molding process.

[0014] [Symbol Explanation]

[0015] 1…Injection molding machine

[0016] 10… Mold, 11… Fixed mold, 12… Movable mold, 15… Mold cavity, 19… Molten resin

[0017] 2… Molding unit

[0018] 3…Control device

[0019] 30… processor, 31… storage medium

[0020] 4…Input device

[0021] 40… Housing, 41… Mode designation switch, 42… Operation start switch

[0022] 45… Display Section

[0023] 5… stipulated period

[0024] 51…First period, 52…Second period

[0025] S1, S2 heating start time, E1, E2 heating end time

[0026] 6… Mold opening and closing unit

[0027] 61…Fixed template, 62…Modible template, 63…Tie rod

[0028] 64…Drive mechanism, 65…Toggle mechanism, 66…Tailstock, 69…Passage

[0029] 7…Injection Unit

[0030] 70… Nozzle, 71… Cylinder, 72… Screw, 73, 730… Heater

[0031] 74… Hopper

[0032] 75… Metering motor, 76… Injection motor, 77… Encoder, 78… Pressure measuring element

[0033] 79…Temperature Sensor

[0034] 8…Top unit

[0035] 84…Driver Detailed Implementation

[0036] The injection molding machine according to the embodiments will now be described based on the accompanying drawings. The same symbols in the figures denote the same things. The shapes, sizes, and positional relationships shown in the figures are for illustrative purposes only and do not necessarily represent actual shapes, sizes, or positional relationships. It should be noted that the present invention is not limited to the structures shown in the embodiments, and as indicated by the scope of the claims, it is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

[0037] <Implementation Method 1>

[0038] Figure 1 The injection molding machine 1 of Embodiment 1 shown is an apparatus for producing molded articles by injecting molten material into a mold 10. The injection molding machine 1 includes a molding unit 2, a control device 3, and an input device 4. The molding unit 2 is the main structure of the injection molding machine 1. The molten material in the injection molding machine 1 is molten resin, i.e., molten resin. The input device 4 is a device for inputting instructions into the injection molding machine 1 by an operator. The control device 3 is a device for controlling the molding unit 2 based on the instructions input by the operator. One feature of the injection molding machine 1 in this example is the control of the heater 73 provided in the molding unit 2 of the injection molding machine 1. The various structures of the injection molding machine 1 will be described below, and the control of the heater 73 will be described next.

[0039] Molding Unit

[0040] The molding unit 2 in this example includes: a mold opening / closing unit 6 for opening and closing the mold 10; an injection unit 7 for injecting molten resin into the mold 10; and an ejector unit 8 for removing the molded article from the mold 10. The molding unit 2 may also include a spraying unit for spraying fluids such as gas or release agent onto the inner circumferential surface of the mold 10.

[0041] [Mold opening and closing unit]

[0042] The mold opening and closing unit 6 is a structure for opening, closing, and clamping the mold 10. The mold 10 includes a fixed mold 11 and a movable mold 12. The mold opening and closing unit 6 includes: a fixed template 61 for supporting the fixed mold 11; and a movable template 62 for supporting the movable mold 12. The mold opening and closing unit 6 also includes a pull rod 63, a drive device 64, and an elbow mechanism 65. The first end of the pull rod 63, located on the side of the injection unit 7, is fixed to the fixed template 61. The second end of the pull rod 63, on the opposite side of the first end, is fixed to the tailstock 66. The central portion of the pull rod 63 passes through the movable template 62. The movable template 62 moves along the pull rod 63, for example, by the driving force of a drive device 64 such as a motor, transmitted via the elbow mechanism 65.

[0043] If the movable template 62 moves to the left of the paper surface, the fixed mold 11 separates from the movable mold 12, and the mold 10 opens. If the movable template 62 moves to the right of the paper surface, the fixed mold 11 and the movable mold 12 abut against each other, and the mold 10 closes. If pressure is further applied from the movable template 62 to the movable mold 12 of the closed mold 10 in the right direction of the paper surface, the fixed mold 11 and the movable mold 12 close together.

[0044] [Injection Unit]

[0045] The injection unit 7 is a structure that injects molten resin into the mold 10. The injection unit 7 includes a cylinder 71, a screw 72, multiple heaters 73, and a hopper 74. The top of the cylinder 71 has a nozzle 70. The screw 72 is configured to move forward and backward within the cylinder 71. In this example, the forward direction of the screw 72 is towards the mold 10 with its tip approaching the screw. The backward direction of the screw 72 is the opposite of the forward direction.

[0046] Multiple heaters 73 are respectively disposed on the outer periphery of the cylinder block 71 to heat the cylinder block 71. Each of the multiple heaters 73 can be controlled independently. Among the multiple heaters 73, those disposed on... Figure 2 The heater 730 on the outer periphery of the nozzle 70 has a significant impact on the injection pressure of the molten resin 19 injected from the nozzle 70. Heating the nozzle 70 by the heater 730 can reduce the injection pressure. A temperature sensor 79 is located between the nozzle 70 and the heater 730. The measurement result of the temperature sensor 79 is input to the control device 3 to control the heater 73. If the temperature of the cylinder 71 is too high, the molten resin 19 may deteriorate. Monitoring the temperature of the cylinder 71 by the temperature sensor 79 can prevent the deterioration of the molten resin 19.

[0047] The cylinder body 71 is a cylindrical component, and its nozzle 70 is inserted into the passage 69 of the fixed template 61. The tip of the nozzle 70 contacts the fixed mold 11. Molten resin 19 injected from the nozzle 70 into the mold 10 fills the internal space of the mold 10, i.e., the mold cavity 15, to form a molded article. The hopper 74 is a funnel-shaped component used to supply resin flakes, which serve as the raw material for the molten resin 19, into the cylinder body 71.

[0048] like Figure 1 As shown, the injection unit 7 also includes a metering motor 75 and an injection motor 76. In the metering process described later, the metering motor 75 rotates the screw 72, thereby conveying the resin sheet supplied from the hopper 74 toward the top of the cylinder 71. The conveyed resin sheet melts due to the heat of the heater 73. In the injection process described later, the injection motor 76 advances the screw 72, thereby injecting the molten resin 19 into the mold 10. The rotational force of the injection motor 76 is converted into linear motion of the screw 72 by a suitable mechanism. The injection motor 76 is equipped with an encoder 77, which serves as a position sensor and measures the position of the screw 72 within the cylinder 71. Furthermore, a pressure sensor element 78, which is not shown, is provided at the rear end of the screw 72, and measures the injection pressure of the molten resin 19 injected from the nozzle 70. The pressure sensor element 78 measures the pressure exerted on the screw 72 by the molten resin 19 within the cylinder 71. The pressure on the screw 72 is related to the injection pressure of the molten resin 19 injected from the nozzle 70. Therefore, the injection pressure can be calculated based on the measurement value of the pressure sensing element 78.

[0049] [Top unit]

[0050] Ejection unit 8 is a structure that pushes the molded article out of the open mold 10. Ejection unit 8 includes: multiple pins (not shown) for pushing the molded article out; and a drive device 84, such as a motor, for moving the pins forward and backward.

[0051] Input Device

[0052] The input device 4 is a structure for inputting instructions into the injection molding machine 1 by an operator operating the injection molding machine 1. The operator's instructions include: mode instructions, for specifying a particular operating mode selected from multiple operating modes; operation instructions for the molding unit 2 in each operating mode; and setting instructions for molding conditions such as injection speed.

[0053] The operating modes include "OFF mode," "change mode," "manual mode," "semi-automatic mode," and "fully automatic mode." OFF mode is used to stop the operation of the injection molding machine 1. In OFF mode, the power to the injection molding machine 1 can be turned off. Additionally, molding conditions can be set in OFF mode. Change mode is used to change the mold 10 or adjust the actions of each unit 6, 7, and 8 in a series of molding cycles. In change mode, the actions of each unit 6, 7, and 8 are performed at low speed. Manual mode is a mode in which the operator manually instructs each molding-related action, such as opening and closing the mold 10 and injecting molten resin 19. Semi-automatic mode is a mode in which the operation of molding unit 2 is stopped each time a molding cycle is executed. Fully automatic mode is a fully automatic operation mode that continuously manufactures molded bodies by continuously executing a preset number of molding cycles.

[0054] The operation instruction is an instruction to start the operation of the structure provided by the molding unit 2. For example, in manual mode, the operation instruction is an instruction to close the mold 10 by the mold opening and closing unit 6 or to inject molten resin 19 into the mold 10 by the injection unit 7. In addition, for example, in semi-automatic mode, the operation instruction is an instruction to start a new molding cycle by the molding unit 2.

[0055] Figure 3 This is an example of an input device 4. The input device 4 in this example includes a housing 40, multiple mode selection switches 41, multiple action start switches 42, and a display unit 45. The mode selection switch 41 is, for example, a button-type hardware switch pressed by the operator when specifying an operating mode. The action start switch 42 is, for example, a button-type hardware switch pressed by the operator when instructing the molding unit 2 to operate. By making the mode selection switch 41 and the action start switch 42 hardware switches, it is easier to prevent operator error input. The display unit 45 displays the selected operating mode, the action being executed, and molding conditions, etc. The display unit 45 may have a touch panel-type software switch. The software switch, for example, is used for setting molding conditions, etc. Figure 3 The information displayed in the display unit 45 is as described below.

[0056] Control Device

[0057] Figure 1 The control device 3 shown controls the operation of the injection molding machine 1. Instructions input by the operator to the input device 4 are sent as electrical signals to the control device 3. The control device 3 controls the molding unit 2 based on the specific operating mode selected by the operator.

[0058] The control device 3 is composed of a computer. The computer can be housed within the casing 40 of the input device 4 (see reference). Figure 3The computer includes a processor 30 and a storage medium 31. The processor 30 can be any processor suitable for controlling the computer. Examples of processors include CPUs (Central Processing Units), GPUs (Graphics Processing Units), DSPs (Digital Signal Processors), FPGAs (Field Programmable Gate Arrays), and ASICs (Application Specific Integrated Circuits). There can be one or more processors 30. Multiple processors 30 can be physically separated and cooperate to perform processing. The storage medium 31 stores programs used to cause the injection molding machine 1 to produce molded bodies. Representative storage media 31 include ROMs (Read-Only Memory) and RAMs (Random Access Memory). The processor 30 executes the programs read from the storage medium 31, causing the various structures of the injection molding machine 1 to perform actions.

[0059] The computer that controls the operation of the injection molding machine 1 can be another computer connected to the injection molding machine 1 via a network such as LAN (Local Area Network), WAN (Wide Area Network), or the Internet.

[0060] Heater Control in Injection Molding Processes

[0061] In this example of injection molding machine 1, the control device 3 activates the heater 73 with a specified current value during a predetermined period of the injection process in the molding cycle, thereby heating the heater 73. In this example, the heater 73 is located in... Figure 2 The heater 730 is located around the nozzle 70 shown. The heater 730 will not be turned off during a specified period.

[0062] When explaining the injection process, it will be based on Figure 4 The molding cycle used to produce molded products is described. Figure 4 The diagram illustrates the processes constituting the molding cycle, and the relationship between the actions of the mold opening / closing unit 6 and the injection unit 7 in each process. Figure 4 In the diagram, the direction of time flow is to the right of the paper. The molding cycle includes mold closing, mold clamping, injection molding, metering, and mold opening processes. The molding cycle may include a product removal process (not shown). The product removal process is the process of removing the molded product from the mold 10 using the ejector unit 8.

[0063] In the mold closing process, the mold opening and closing unit 6 performs the mold closing action to close the mold 10. The mold closing action involves bringing the fixed mold 11 and the movable mold 12 closer together, until they come into contact. In the mold closing process following the mold closing process, the mold opening and closing unit 6 performs the mold closing action to fasten the mold 10. The mold closing action involves the movable mold 12 pressing towards the fixed mold 11. As a result, under a specified pressure, the fixed mold 11 and the movable mold 12 are fastened together. Figure 4 In the diagram, the action of the mold opening and closing unit is shown as "mold closing" after "mold closing". After the mold closing process is completed, the mold 10 remains in a tight state under a specified pressure until the mold opening process described later begins.

[0064] In the injection molding process, molten resin 19 is injected from injection unit 7 into mold 10, filling the mold 10 with molten resin 19. During the injection, screw 72 advances within cylinder 71. Following the injection, a holding pressure action is performed. During the holding pressure action, screw 72 advances within cylinder 71 at a slower speed than during the injection. The distance traveled by screw 72 during the holding pressure action is very small.

[0065] In the metering process, a predetermined amount of resin flakes is introduced from the hopper 74 into the cylinder 71 by rotating the screw 72 while it is retracting. These resin flakes are melted by heating with the heater 73. As a result, a predetermined amount of molten resin 19 is metered in the cylinder 71.

[0066] In the mold opening process, the mold opening and closing unit 6 performs a decompression action that gradually reduces the clamping force between the fixed mold 11 and the movable mold 12. In the mold opening process, the mold opening and closing unit 6 further performs a mold opening action that separates the movable mold 12 from the fixed mold 11. In other words, the mold opening process reduces the clamping force between the fixed mold 11 and the movable mold 12, further separating them, thereby enabling the molded product to be removed from the mold 10.

[0067] In the injection molding machine 1 of this example, during a predetermined period of the injection process, the control device 3 controls the heater 730 to heat up. The start and end times of this predetermined period can be set to any point in the injection process. The predetermined period is, for example, at least one of a period of drastic changes in injection pressure and a period of unstable and fluctuating injection pressure. An example of the predetermined period 5 is as follows: Figure 5 As shown. Figure 5 The shaded area in the injection process diagram shows a predetermined period 5 during which the heater 730 performs its action. In this example, the predetermined period 5 includes two periods: a first period 51 and a second period 52. The number of predetermined periods 5 can be one or more.

[0068] The first period 51 includes the early stage of the injection process. The early stage of the injection process is the first half of the period when the time from start to end of the injection process is divided into two equal parts. That is, the early stage of the injection process includes the initial stage of the injection process, which includes the start time of the injection process. The second half of the period when the time from start to end of the injection process is divided into two equal parts is the later stage of the injection process. In this example, the heating start time S1 of the first period 51, i.e., the energization and on-time of the heater 730, coincides with the start time of the injection process. In this example, the heating end time E1 of the first period 51, i.e., the energization and off-time of the heater 730, falls within the range of the early stage of the injection process. The heating end time E1 can fall within the range of the later stage of the injection process.

[0069] The second period 52 includes at least a portion of the later stage of the injection process. In this example, the heating start time S2 of the second period 52, i.e., the energization and on-time of the heater 730, occurs before or after the start of the later stage of the injection process. The heating start time S2 can be within the range of the early stage of the injection process. In this example, the heating end time E2 of the second period 52, i.e., the energization and on-time of the heater 730, occurs within the range of the later stage of the injection process. The heating end time E2 can also relate to the process period after the injection process is performed.

[0070] based on Figure 6 The reasons for selecting the first period 51 and the second period 52 are explained. Unlike this example, Figure 6 This is a graph showing the injection pressure of molten resin 19 from nozzle 70 when heater 730 is turned on or off via PID control during the injection molding process. The horizontal axis represents the top position of screw 72 with its origin at 0, in millimeters (mm). The origin is the top position of screw 72 before the injection process begins. This means that the further to the right along the horizontal axis, the closer screw 72 is to the mold 10. The right end of the graph represents the position of screw 72 at the end of the injection process. It can be assumed that... Figure 5 The horizontal axis roughly corresponds to the time elapsed since the start of the injection process. The value showing the position of screw 72 is calculated by a computer constituting the control device 3 based on information from encoder 77. The vertical axis represents the injection pressure of the molten resin 19 injected from nozzle 70 into mold 10, in megapascals (MPa). The injection pressure is calculated by a computer based on information from pressure measuring element 78.

[0071] like Figure 6As shown, in the initial stage of the injection process, when the screw 72 approaches the origin, the injection pressure becomes very high. This can be attributed to the cooling of the nozzle 70 upon contact with the mold 10, and the increased viscosity of the molten resin near the nozzle 70. When the injection pressure exceeds the specified value, PID control intervenes, the nozzle 70 is heated by the heater 730, and the injection pressure decreases. After the initial stage of the injection process, if the nozzle 70 is heated by PID control, the viscosity of the molten resin decreases, and the injection pressure stabilizes. However, in the later stages of the injection process, specifically from the middle to the end, the injection pressure fluctuates. This can be attributed to the PID control alternately turning on the heater 730 due to a decrease in the temperature of the nozzle 70 and turning off the heater 730 due to a rise in the temperature of the nozzle 70. These fluctuations in injection pressure in the initial and later stages of the injection process can lead to uneven quality of the molded products.

[0072] exist Figure 6 In the example shown, the injection pressure may fluctuate at the beginning and end of the injection process. To reduce this fluctuation, a setting is provided. Figure 5 The first period 51 and the second period 52 are shown. During periods other than the first period 51 and the second period 52, the heater 730 can remain off, or it can be turned on / off via PID control. If the heater 730 is turned off during periods other than the first period 51 and the second period 52, the power consumption of the heater 730 can be reduced. It should be noted that, depending on the type of resin constituting the molded article, the number and timing of the specified periods 5 for heating the heater 730 can be adjusted accordingly. Figure 5 The examples are different.

[0073] During the first period 51 and the second period 52, the heater 730 is continuously energized. The current value energizing the heater 730 can be a preset predetermined value or a fluctuating value that changes based on the measurement results of the temperature sensor 79. In this example, the current value is a preset predetermined value. That is, in this example, the heater 730 is controlled to be on during the first period 51 and the second period 52.

[0074] The heating start times S1 and S2 during the specified period 5 are controlled by the control device 3 using, for example, any of the information in (A) to (C) below as triggers. The heating end times E1 and E2 during the specified period 5 are controlled by the control device 3 using, for example, the information in (A) or (B) below as triggers.

[0075] (A) Position of screw 72 inside cylinder 71

[0076] (B) Time elapsed from any point in the molding cycle

[0077] (C) Injection pressure from nozzle 70

[0078] The information (A) above is the position of the screw 72 obtained from information from an encoder 77, for example, which acts as a position sensor. Since the control device 3 controls the operation of each structure of the molding unit 2, it also controls the start time of the injection process. Based on the position of the screw 72 during the injection process, the control device 3 determines the heating start time S1, S2 and the heating end time E1, E2. At the heating start time S1, S2, the control device 3 turns on the heater 730; at the heating end time E1, E2, the control device 3 turns off the heater 730. For example, the control device 3 performs the following control: when the position of the screw 72 is 1 mm from the origin, the heater 730 is turned on; when the position of the screw 72 is 5 mm from the origin, the heater 730 is turned off. The position of the screw 72 for turning the heater 730 on / off can be obtained by the operator, for example, through pre-molding. Figure 6 The data shown is used to make the determination.

[0079] The information in (B) above refers to the elapsed time from any point in the molding cycle. Any point in time is, for example, the start time of the injection process. For example, for heating start times S1 and S2, control device 3 controls the heater 730 to turn on at the start time of the injection process or after a predetermined time has elapsed from the start time. For heating end times E1 and E2, for example, control device 3 controls the heater 730 to turn off after a predetermined time has elapsed from the start time of the injection process. Here, the heating end time E2, which includes the second period 52 of the latter half of the injection process, can be set by the elapsed time starting from the start time of the mold opening process.

[0080] The information in (C) above is, for example, the injection pressure obtained from the pressure sensing element 78, which functions as a pressure sensor. For instance, when the injection pressure exceeds a threshold, the control device 3 begins heating the heater 730. The information in (C) above is not used as a trigger to terminate heating of the heater 730. Figure 6 As shown, the injection pressure fluctuates slightly, especially in the later stages of the injection process, making it difficult to set a threshold for the injection pressure at which the heater 730 stops heating.

[0081] The information (A) through (C) above can be used in combination. For example, information (A) can be used as a trigger to start heating, and information (B) can be used as a trigger to end heating. Furthermore, information (C) can be used as a trigger to start heating, and information (B) can be used as a trigger to end heating.

[0082] based on Figure 3An example is given of an operator setting the heating start and end times via input device 4. In this example, the display unit 45 of input device 4 shows the columns "Heater", "Start Mode", "Start", "Delay", "Output Stop", and "Stop". The names of the columns are for convenience only.

[0083] The "Heater" field specifies which of the multiple heaters 73 in the injection molding machine 1 performs the operation. In the diagram, "Heater 1" refers to the heater 730 located around the nozzle 70. The type of heater 73 controlled can be changed in the "Heater" field. For example, changing "Heater 2" to "Heater 1" in the diagram allows you to set... Figure 5 The two specified periods are shown in section 5.

[0084] The "Start Mode" column is used to specify the trigger for starting heating. This means that "Injection Start" in the diagram is based on the start time of heating in the injection process. The "Start" column is used to specify the moment when the heater 730 performs an action based on the reference specified in the "Start Mode" column. The unit of the "Start" column is seconds (s). In the diagram, it is "0.00s," in which case the heating of the heater 730 starts simultaneously with the injection process. The unit of the "Start" column changes automatically according to the reference specified in the "Start Mode" column. For example, if the "Injection Position" is specified in the "Start Mode" column based on the position of the screw 72 at the start of the injection process, the unit of the "Start" column changes to millimeters (mm).

[0085] The "Delay" column is used to specify a delay in the heating start time. By using the "Delay" column, the heating start of heater 730 can be delayed by the time specified in the "Delay" column only after the conditions specified in the "Start" column are met. The delay in the heating start time is effective for fine-tuning the specified period 5 to improve the quality of the molded products.

[0086] The "Output Stop" field specifies the trigger for ending heating. This means that the "Injection Position" in the diagram is based on the position of screw 72 at the start of the injection process, setting the trigger for ending heating. The trigger for ending heating can be toggled. The "Stop" field specifies the moment when heater 730 stops operating based on the reference specified in the "Output Stop" field. In the diagram, it is "100mm," meaning that heater 730 stops when screw 72 advances 100mm from the start of the injection process. The unit in the "Stop" field changes automatically based on the reference specified in the "Output Stop" field. For example, if "Injection Start" is specified in the "Output Stop" field, the unit in the "Stop" field changes to seconds.

[0087] By implementing the control of heater 730 as described above, the reduction can be achieved. Figure 6The diagram shows the fluctuations in injection pressure during the initial and later stages of the injection molding process. As a result, because the injection pressure can be kept balanced throughout the entire injection process, high-quality molded parts can be manufactured with a high yield.

Claims

1. An injection molding machine, characterized in that, The injection molding machine has the following features: The cylinder has nozzles for injecting molten resin into the mold; The screw is configured to move forward and backward within the cylinder. A heater is disposed on the outer periphery of the nozzle; and A control device is used to control the forward and backward movement of the screw and the operation of the heater. During the molding cycle, the control device advances via the screw and, during a specified period of the partial injection process in which the molten resin is injected into the mold, activates the heater with a specified current value to heat the nozzle.

2. The injection molding machine according to claim 1, characterized in that, The specified period includes at least a portion of the later stage of the injection process.

3. The injection molding machine according to claim 1 or 2, characterized in that, The injection molding machine also includes an input device for the operator to input the start and end times of heating of the heater during the specified period. The control device controls the start and end of heating during the specified period based on input from the operator to the input device.

4. The injection molding machine according to claim 3, characterized in that, The control device uses the position information of the screw in the cylinder, the elapsed time information from any moment in the molding cycle, or the injection pressure information from the nozzle as triggers to execute the heating start or heating end.

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