JP2014240201A - Automatic operational method for injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatize measurement of the viscosity of a molten resin used in injection molding and improve convenience.SOLUTION: During automatic operation of producing a molding, shot number counting means 17 counts the number of shots of injecting a molten resin from an injection nozzle 3. When the counted number of shots reaches a specified value set preliminarily, forward/backward drive means causes the injection nozzle 3 to retreat so as not to touch the mold, and, in this condition, the viscosity of the molten resin injected from the injection nozzle 3 is calculated automatically. When the calculated viscosity of the molten resin lies in a specified range of the resin viscosity, the automatic operation of producing a molding repeatedly is re-started. The measurement of the viscosity of a molten resin is carried out automatically during automatic operation of producing a molding continuously by an injection molding machine, leading to improvement of convenience.

Description

  The present invention relates to an automatic operation method of an injection molding machine for producing a molded product by injecting a resin melted by a heating cylinder into a mold cavity, and in particular, by measuring the viscosity of the molten resin, The present invention relates to an automatic operation method of an injection molding machine that can realize non-defective molding by employing a resin having a predetermined viscosity for injection molding.

  In an injection molding machine that molds a molded product by injection molding, it is required to appropriately maintain the resin viscosity of the molten resin injected into the mold cavity. Patent Document 1 filed by the same applicant as the present application discloses a technique that allows the viscosity of a resin used for injection molding to be measured by the injection molding machine itself.

Japanese Patent No. 3732821

  However, in Patent Document 1, although the viscosity of the molten resin injected into the cavity of the mold can be measured, for example, the same machine (same injection molding) using the same type of resin material from the same manufacturer. When the weighing operation is performed under the same molding conditions, for example, if different resin material lots are used, the resin viscosity varies depending on the lot, so use a resin with a predetermined viscosity. In order to perform injection molding with high accuracy, every time a resin lot is changed, it is measured whether or not the resin viscosity is within a predetermined range.

  The present invention has been made in view of the above-mentioned problems, and improves the convenience by automating the measurement of the viscosity of the molten resin during or before the start of molding, in which a molded product is continuously produced by an injection molding machine. An object is to provide an automatic operation method of an injection molding machine.

The invention of the automatic operation method of the injection molding machine according to claim 1
After the molten resin is metered by reversing the screw in the heating cylinder, the molten resin is moved from the injection nozzle attached to the tip of the heating cylinder to the mold cavity by advancing the screw as an injection process. An injection molding machine for injecting
Shot number counting means for counting the number of shots for injecting molten resin from the injection nozzle, rotation drive means for rotating the screw when performing the measuring step, and advance / retreat drive means for moving the injection nozzle back and forth,
During the automatic operation in which the injection nozzle is advanced by the advance / retreat driving means and the mold is touched to repeatedly mold the molded product, the shot number counting means counts the number of shots for injecting the molten resin from the injection nozzle. When the counted number of shots reaches a predetermined value, the advance / retreat driving means retracts the injection nozzle so that the injection nozzle does not touch the mold.
In a state where the injection nozzle is retracted so as not to touch the mold,
The resin viscosity calculating means calculates the resin viscosity of the molten resin injected from the injection nozzle based on the actually measured injection pressure value,
When the control means determines that the calculated resin viscosity of the molten resin is within a predetermined resin viscosity range,
The advance / retreat driving means touches the injection nozzle to the mold, and restarts the automatic operation for repeatedly forming the molded product.

The invention of the automatic operation method of the injection molding machine according to claim 2
After the molten resin is metered by reversing the screw in the heating cylinder, the molten resin is moved from the injection nozzle attached to the tip of the heating cylinder to the mold cavity by advancing the screw as an injection process. An injection molding machine for injecting
Time counting means for counting the operating time of the injection molding machine, rotation driving means for rotating the screw when performing the measuring step, and advance / retreat driving means for advancing / retreating the injection nozzle,
During the automatic operation in which the injection nozzle is moved forward by the advance / retreat driving means and the mold is touched to repeatedly form a molded product, the operation time of the injection molding machine is counted by the time measuring means, and the counted time is counted. When the operating time reaches a predetermined time, the advance / retreat driving means retracts the injection nozzle so as not to touch the injection nozzle by retreating the injection nozzle,
In a state where the injection nozzle is retracted so as not to touch the mold,
The resin viscosity calculating means calculates the resin viscosity of the molten resin injected from the injection nozzle based on the actually measured injection pressure value,
When the control means determines that the calculated resin viscosity of the molten resin is within a predetermined resin viscosity range, the advance / retreat driving means touches the injection nozzle to the mold, and molds the molded product. It is characterized by resuming repeated automatic operation.

The invention of the automatic operation method of the injection molding machine according to claim 3 is the method according to claim 1 or 2,
The actually measured injection pressure value is measured when the injection speed constant control is performed.

The invention of the automatic operation method of the injection molding machine according to claim 4 is the invention according to claim 3,
The measured injection pressure value is an average value measured a plurality of times during constant injection speed control.

The invention of the automatic operation method of the injection molding machine according to claim 5 is any one of claims 1 to 4,
The resin viscosity η (Pa · sec) of the molten resin is calculated by the following formula.
[Equation 1]
η = (r ⁴ × P) / (32 × L × D ² × V)
Where r: diameter of injection nozzle hole (mm)
P: Injection pressure (Pa)
L: Land length of the injection nozzle (mm)
D: Screw diameter (mm)
V: Injection speed (mm / sec)

  According to the present invention, when performing automatic operation of repeatedly molding a molded product, the number of shots for injecting the molten resin from the injection nozzle is counted by the shot number counting means, and the counted number of shots is preset. When the predetermined value is reached, the advance / retreat driving means moves backward so as not to touch the injection nozzle to the mold, and in this state, as the resin viscosity measurement mode, the viscosity of the molten resin injected from the injection nozzle is automatically calculated, When the calculated viscosity of the molten resin is within a predetermined resin viscosity range, the automatic operation for repeatedly molding the molded product is started again. Therefore, it is possible to automatically measure the viscosity of the molten resin by automatically performing the resin viscosity measurement mode during the automatic operation in which the molded product is continuously manufactured by the injection molding machine, improving convenience. Can be achieved.

  Further, according to the present invention, when the automatic operation of repeatedly molding the molded product is performed, the operation time of the injection molding machine is counted by the time measuring means, and when the counted operation time reaches a predetermined time, The advancing / retreating drive means retracts so that the injection nozzle does not touch the mold, and in this state, as the resin viscosity measurement mode, the viscosity of the molten resin injected from the injection nozzle is automatically calculated, and the calculated viscosity of the molten resin Is within the predetermined resin viscosity range, the automatic operation for repeatedly molding the molded product is started again. Therefore, it is possible to automatically measure the viscosity of the molten resin by automatically performing the resin viscosity measurement mode during the automatic operation in which the molded product is continuously manufactured by the injection molding machine, improving convenience. Can be achieved.

It is a block diagram which shows the structure of the control system of the injection molding machine of this invention. It is a schematic block diagram which shows the heating cylinder comprised by the injection molding machine. It is explanatory drawing which shows an example of the display of the display apparatus in an injection molding machine. It is explanatory drawing which shows the relationship between resin viscosity and a shear rate. It is a flowchart which shows the operation example when adjusting the viscosity of molten resin.

  Embodiments of the present invention will be described below with reference to FIGS. Of course, it is needless to say that the present invention can be easily applied to configurations other than those described in the present embodiment without departing from the spirit of the invention.

  The injection molding machine in the present embodiment performs the molten resin measurement process by rotating the screw 2 provided rotatably in the heating cylinder 1 while rotating it, and then advances the screw 2 as an injection process. As shown in FIG. 1, the injection molding machine includes a control means for controlling the entire injection molding machine. The injection molding machine 3 injects molten resin from the injection nozzle 3 attached to the tip of the heating cylinder 1. 4. Input device 5 such as a keyboard device connected to the control means 4, a display device 6 such as a liquid crystal display device connected to the control means 4, and a sensor group 7 composed of a plurality of sensors provided in each part of the injection molding machine A driver group 8 including a plurality of driver circuits for performing drive control of a plurality of drive sources disposed in each part of the injection molding machine is configured.

  As shown in FIG. 2, a heater (band heater) 10 is mounted on the outer periphery of the heating cylinder 1, and is supplied into the heating cylinder by adjusting the temperature of the heater so that the injection nozzle 3 The temperature of the resin injected from the tip is adjusted.

  The control means 4 is a series of automatic operations for molding a molded product such as a metering operation, a suck back operation after the metering operation, an injection operation for injecting molten resin into the mold cavity, a mold opening / closing operation, and an ejection operation. Control, calculation / storage of actual measurement data during automatic operation, good / defective product judgment processing of molded product, abnormal handling judgment processing, predetermined resin viscosity (viscosity of molten resin used for injection molding) Various processes such as a determination process for determining whether or not, and a molding condition such as resin viscosity are displayed on the display device 6 are performed. Although not shown in FIG. 1, the control means 4 includes a CPU, a ROM, a RAM, and various I / O interfaces, and various processes are executed by various programs created in advance. However, in the present embodiment, as shown in FIG. 1, the control unit 4 includes a molding condition setting storage unit 11, a molding process control unit 12, an actual measurement storage unit 13, a resin viscosity calculation unit 14, and a temperature adjustment unit 15. The display processing means 16 and the like are configured, and the sensor group 7 includes a shot number counting means 17, a time measuring means 18 for counting the operating time of the injection molding machine, and a temperature of the molten resin injected from the injection nozzle 3. The temperature measuring means 19 and the injection pressure measuring sensor 20 are configured. The driver group 8 includes a motor driver 21 that performs feedback control, and a heater driver. 2, the fluid actuator driver 23 and the like are configured.

  Also, the molding condition setting storage means 11 stores various operating condition values input from the input device 5 in a rewritable manner. The operation condition items corresponding to the operation condition values include, for example, a measurement control condition, a suck back control condition, an injection control condition, a mold closing control condition, a mold opening control condition, an eject control condition, as shown in FIG. After displaying the image, the number of shots “N” in step 2 to be described later, the operating time of the injection molding machine, and the like can be mentioned.

  The molding process control means 12 is based on a molding process control program created in advance and a set condition value stored in the molding condition setting storage means 11 and a group of sensors (shot number counting) arranged in each part of the injection molding machine. The driver group 8, a motor driver 21, a heater driver 22, and a fluid actuator as the driver group 8 while referring to measurement information from the means 17, the time measuring means 18, the temperature measuring means 19, the injection pressure measuring sensor 20, etc. The drive control of the corresponding drive source is performed via the driver 23 and the like, and a series of automatic operations for molding a molded product and a resin viscosity measurement mode described later are executed.

  The measured value storage means 13 stores the value of the resin viscosity calculated by the resin viscosity calculation means 14, the number of shots of the molten resin injected from the injection nozzle 3 counted by the shot number counting means 17, and the time count means 18. The operating time of the injection molding machine that has been recorded is stored.

  The resin viscosity calculating means 14 calculates (measures) the resin viscosity by a calculation formula to be described later, using an actually measured injection pressure value (actually measured value of the injection pressure measuring sensor 20) when the injection speed is constant. Based on the calculated viscosity value of the molten resin, the temperature adjustment means 15 changes the set temperature of the heater 10 of the designated channel (ch).

  Further, the display processing means 16 creates display image data of a designated display mode based on a display image creation / control program created in advance by a call signal for a desired display image when the operator operates the input device. To do. The generated image data is transferred to a frame buffer (not shown) and temporarily stored, and the output of the frame buffer is displayed on the screen of the display device 6 in the state shown in FIG. Displayed as image data.

Here, the calculation method of the resin viscosity by the resin viscosity calculation means 14 is demonstrated. When the shear stress τ (Pa) is η (Pa · sec) and the shear rate is γ (sec-1),
.tau. =. eta..times..gamma.

Here, the relationship between the shear rate γ represented by the formula (1) (corresponding to the injection speed represented by the forward speed of the screw 2 in an inline screw type injection molding machine) and the viscosity η (viscosity of the molten resin) That is, it has been confirmed that the viscosity of the resin exhibits the behavior as shown in FIG. 4. If the shear rate γ is in the range of 10 ¹ to 10 ⁵ , the viscosity increases with the change of the shear rate γ. It has been confirmed that η also changes. On the other hand, when the shear rate γ is less than 10 ¹ or exceeds 10 ⁵ , the viscosity η shows a substantially constant value regardless of the change in the shear rate γ. Therefore, when the shear rate (injection rate) maintains a certain predetermined value within the range of 10 ¹ to 10 ⁵ , the viscosity of the molten resin can be calculated from the equation (1). For example, the shear rate γ obtained from the injection speed of 10 mm / sec is generally about γ = 10 ³ to 10 ⁴ regardless of the size of the machine, and satisfies the above-described viscosity calculation conditions satisfactorily. . Meanwhile, the shear rate gamma obtained from the injection speed 100 mm / sec, at 100 tons or more machines also indicate the value of gamma = 10 ⁵ neighborhood, no longer a parameter of appropriate speed settings. Therefore, in the present invention, the resin viscosity is controlled so that the injection speed (screw advancement speed) is controlled to maintain a certain value within the range of 5 to 50 mm / sec, and the above-described viscosity calculation condition is satisfactorily satisfied. I am trying to measure.

In an in-line screw type injection molding machine, according to JIS K7199, the shear stress τ and shear rate γ described above are the injection pressure P (Pa), the injection nozzle hole diameter r (mm), and the injection nozzle land length. When L (mm) and the flow rate are Q (mm3 / sec),
τ = (P × r) / (4 × L)
...... (2) Formula γ = (32 × Q) / (π × r ³ )
... represented by equation (3).

Here, when the flow rate Q is A (mm ² ) for the screw cross-sectional area and V (mm / sec) for the injection speed (screw advance speed),
Since Q = A × V (4), if the diameter of the screw is D, (4)
Q = (π × D ² × V) / 4
...... It is expressed by (5), and substituting (5) into (3),
γ = (8 × D ² × V) / r ³
...... Equation (6).

Therefore, after all, the viscosity η of the molten resin is
η = (r ⁴ × P) / (32 × L × D ² × V)
...... It can be obtained from equation (7). That is, if the injection speed is constant, the value of the injection speed and the mechanical dimension to be controlled are known if the injection pressure P is actually measured, and the resin viscosity is calculated based on the actually measured injection pressure value. It becomes possible.

  According to the measurement method of the resin viscosity in the injection molding machine of the present embodiment using such a calculation formula, the measured resin viscosity can be obtained with a highly accurate value substantially equal to the value presented by the resin material manufacturer. It was confirmed by experiment. In the injection molding machine of the present embodiment, the resin viscosity can be calculated by measuring the injection pressure value during the period when the condition that the injection speed is constant is satisfied. However, when injecting and filling molten resin into the mold, the injection speed may vary depending on the shape of the cavity of the mold, or when performing ultra-high speed injection, the injection speed However, it is also conceivable that the value falls outside the range in which the above-mentioned viscosity calculation conditions are satisfactorily satisfied. Therefore, when measuring the resin viscosity, usually, the injection is performed under the condition that the injection nozzle 3 at the tip of the heating cylinder is not touching the mold and the injection speed is constant by feedback control. In the mode (in the state of free injection with a constant injection speed), the resin viscosity is measured and calculated.

  Next, an example of an operation for calculating the viscosity of the molten resin and adjusting the calculated viscosity of the molten resin will be described with reference to FIG. FIG. 5 shows a case where the automatic operation is started after the temperature of the resin supplied in the heating cylinder is raised to a predetermined temperature, and Steps 2 to 10 represent operations in the resin viscosity measurement mode. For example, when an automatic operation for molding a molded product is started after changing a resin lot (step 1), the number of shots for injecting molten resin from the injection nozzle 3 is counted by the shot number counting means 17 and output to the control means 4 It will be done.

  Next, in Step 2, when the Nth shot which is the preset number of shots is not reached, the automatic operation is continued. On the other hand, when the Nth shot is reached, the process proceeds to Step 3 and the die is moved. The injection nozzle 3 that has been touched is moved backward by the forward / backward drive means and is separated from the mold. The preset number of shots is, for example, “1000” shots as shown in the lower right side of FIG. 3, and by manually changing the setting of the “1000” field in FIG. 3, It is possible to change to an appropriate number of shots.

  Next, the viscosity of the molten resin injected from the injection nozzle that has been retracted so as not to touch the mold by being retracted is calculated by the resin viscosity calculating means 14 using the above formula (step 4), and the calculated melting Determination of the viscosity of the resin is made (step 5). Here, when the viscosity of the molten resin is within the predetermined resin viscosity range, the injection nozzle is advanced (step 6), and the mold is touched. As the state returns, N is reset to “0” (N = 0), and the control means 4 resumes automatic operation (step 1). In addition, you may determine the measurement of resin viscosity here by the average value of several times.

  On the other hand, when the viscosity of the molten resin calculated in step 5 is not within the predetermined resin viscosity range, the temperature of the molten resin injected from the injection nozzle 3 by the temperature measuring means 19 is determined. The temperature adjustment means 15 changes the set temperature of the heater 10 (e.g., rises) using the measurement result and the like, and the viscosity of the molten resin injected from the injection nozzle 3 is set to a predetermined resin viscosity. (Step 7). The operations of steps 7 and 8 are repeated until the set temperature of the heater 10 reaches a predetermined temperature. As shown in step 8, the control means that the set temperature of the heater 10 has reached the predetermined temperature. If it is confirmed at 4, the viscosity of the molten resin injected from the injection nozzle 3 is calculated again by the resin viscosity calculating means 14 (step 4). Note that, in Step 7, “the set temperature of the heater is changed by Y ° C.”, but as shown in FIGS. 2 and 3, the heater 10 of the present embodiment is in the longitudinal direction of the heating cylinder 10. Are provided with heaters 1 to 5 (Xch), and by having a plurality of heaters, fine temperature adjustment is possible.

  Next, after step 4, the viscosity is determined (equivalent to step 5). When the viscosity of the molten resin is not within the predetermined resin viscosity range, the temperature of the heater 10 is changed (step 7). Phase, etc.), confirmation whether the set temperature of the heater 10 has reached a predetermined temperature (equivalent to step 8), viscosity calculation (equivalent to step 4), determination of viscosity (equivalent to step 5), etc. are repeated, This process is performed Z times (predetermined number), and when the viscosity of the molten resin does not fall within the predetermined resin viscosity even after reaching Z times, the injection molding machine is automatically stopped. On the other hand, when the viscosity of the molten resin falls within a predetermined resin viscosity within Z times, the injection nozzle is advanced to return to the state where the mold is touched and N is reset to “0” (N = 0). The control means 4 resumes automatic operation.

  As described above, according to the present embodiment, after the screw 2 in the heating cylinder 1 is rotated and moved backward, the molten resin is metered, and then the screw 2 is advanced as an injection process to be attached to the tip of the heating cylinder. The injection molding machine for injecting molten resin from the injection nozzle 3 into the mold cavity, the shot number counting means 17 for counting the number of shots for injecting the molten resin from the injection nozzle 3, and the screw for performing the metering step 2 is provided with a rotation driving means for rotating 2 and an advancing / retreating driving means for advancing and retreating the injection nozzle 3. The shot number counting means 17 counts the number of shots from which the molten resin is injected from the injection nozzle 3, When the number of shots reached a predetermined value, the advancing / retreating drive means retreats the injection nozzle 3 together with the heating cylinder 1 to inject from the injection nozzle 3 in a state of retreating so that the injection nozzle 3 does not touch the mold. After the viscosity of the molten resin is calculated, the advancing / retreating drive means touches the injection nozzle 3 to the mold and restarts the automatic operation for repeatedly molding the molded product. When the calculated viscosity of the molten resin is determined and the viscosity of the molten resin is not within a predetermined resin viscosity range, the temperature adjusting means 15 is set to the heater 10 provided in the heating cylinder 1. By changing the temperature, the viscosity of the molten resin having the characteristic that the viscosity is lowered by increasing the temperature injected from the injection nozzle 3 is adjusted so as to be within a predetermined resin viscosity range. Therefore, when performing an automatic operation of repeatedly molding a molded product, the number of shots for injecting the molten resin from the injection nozzle 3 is counted by the shot number counting means 17, and the number of shots counted is a predetermined value set in advance. When the numerical value is reached, as the resin viscosity measurement mode, the viscosity of the molten resin injected from the injection nozzle 3 is automatically calculated, and when the calculated viscosity of the molten resin is not within the predetermined resin viscosity range, The setting temperature of the heater 10 is changed by the adjusting means 15 so that the viscosity of the molten resin is adjusted to be within a predetermined resin viscosity. Immediately thereafter, the automatic operation for repeatedly molding the molded product is started again. Therefore, the viscosity of the molten resin can be reduced by performing the resin viscosity measurement mode during the automatic operation in which the molded product is continuously manufactured by the injection molding machine. Automatically it becomes possible to perform the measurement and viscosity adjusting addition, it is possible to enhance the convenience to simplify the viscosity adjustment of the resin by the operator.

  As mentioned above, although an example of this embodiment was explained in full detail, this invention is not limited to the said embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention. In the above example, the number of shots for injecting the molten resin from the injection nozzle 3 is counted by the shot number counting means 17, and the viscosity of the molten resin injected from the injection nozzle 3 when the counted number of shots reaches a predetermined value. However, as shown in FIG. 1, the present injection molding machine is provided with a time measuring means 18 for counting the operation time of the injection molding machine. Therefore, the time measuring means 18 automatically operates the injection molding machine. It is also possible to calculate the viscosity of the molten resin injected from the injection nozzle 3 at the timing when the counted operation time reaches a predetermined time. In the present embodiment, a method is described in which the nozzle is moved backward, but it is also possible to determine the viscosity from the filling pressure during molding.

DESCRIPTION OF SYMBOLS 1 Heating cylinder 2 Screw 3 Injection nozzle 4 Control means 5 Input device 6 Display apparatus 7 Sensor group 8 Driver group 10 Heater 11 Molding condition setting storage means 12 Molding process control means 13 Actual value storage means 14 Resin viscosity calculation means 15 Temperature adjustment Means 16 Display processing means 17 Shot number counting means 18 Timing means 19 Temperature measuring means 20 Injection pressure measuring sensor 21 Motor driver 22 Heater driver 23 Fluid actuator driver

Claims (5)

After the molten resin is metered by reversing the screw in the heating cylinder, the molten resin is moved from the injection nozzle attached to the tip of the heating cylinder to the mold cavity by advancing the screw as an injection process. An injection molding machine for injecting
Shot number counting means for counting the number of shots for injecting molten resin from the injection nozzle, rotation drive means for rotating the screw when performing the measuring step, and advance / retreat drive means for moving the injection nozzle back and forth,
During the automatic operation in which the injection nozzle is advanced by the advance / retreat driving means and the mold is touched to repeatedly mold the molded product, the shot number counting means counts the number of shots for injecting the molten resin from the injection nozzle. When the counted number of shots reaches a predetermined value, the advance / retreat driving means retracts the injection nozzle so that the injection nozzle does not touch the mold.
In a state where the injection nozzle is retracted so as not to touch the mold,
The resin viscosity calculating means calculates the resin viscosity of the molten resin injected from the injection nozzle based on the actually measured injection pressure value,
When the control means determines that the calculated resin viscosity of the molten resin is within a predetermined resin viscosity range, the advance / retreat driving means touches the injection nozzle to the mold, and molds the molded product. An automatic operation method for an injection molding machine, characterized by restarting repeated automatic operation. After the molten resin is metered by reversing the screw in the heating cylinder, the molten resin is moved from the injection nozzle attached to the tip of the heating cylinder to the mold cavity by advancing the screw as an injection process. An injection molding machine for injecting
Time counting means for counting the operating time of the injection molding machine, rotation driving means for rotating the screw when performing the measuring step, and advance / retreat driving means for advancing / retreating the injection nozzle,
During the automatic operation in which the injection nozzle is moved forward by the advance / retreat driving means and the mold is touched to repeatedly form a molded product, the operation time of the injection molding machine is counted by the time measuring means, and the counted time is counted. When the operating time reaches a predetermined time, the advance / retreat driving means retracts the injection nozzle so as not to touch the injection nozzle by retreating the injection nozzle,
In a state where the injection nozzle is retracted so as not to touch the mold,
The resin viscosity calculating means calculates the resin viscosity of the molten resin injected from the injection nozzle based on the actually measured injection pressure value,
When the control means determines that the calculated resin viscosity of the molten resin is within a predetermined resin viscosity range, the advance / retreat driving means touches the injection nozzle to the mold, and molds the molded product. An automatic operation method for an injection molding machine, characterized by restarting repeated automatic operation.   3. The method for automatically operating an injection molding machine according to claim 1, wherein the actually measured injection pressure value is actually measured when a constant injection speed control is performed.   4. The automatic operation method of an injection molding machine according to claim 3, wherein the measured injection pressure value is an average value measured a plurality of times during constant injection speed control. The automatic operation method for an injection molding machine according to any one of claims 1 to 4, wherein a resin viscosity η (Pa · sec) of the molten resin is calculated by the following formula.
[Equation 1]
η = (r ⁴ × P) / (32 × L × D ² × V)
Where r: diameter of injection nozzle hole (mm)
P: Injection pressure (Pa)
L: Land length of the injection nozzle (mm)
D: Screw diameter (mm)
V: Injection speed (mm / sec)

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