JP2014061677A - Temperature control device of injection molding machine having temperature correction function and temperature control method of injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a temperature control device of an injection molding machine having a temperature correction function that can prevent temperature of a molten resin from becoming lower than preset temperature, and to provide a temperature control method of an injection molding machine.SOLUTION: A heater 10 is mounted on a circumference of an injection cylinder 12 of an injection molding machine. Temperature of an injection cylinder 12 heated by the heater 10 is detected by a temperature detector 14. A temperature control device 8 performs temperature control of the heater 10 based on a temperature correction amount Tadj set by a temperature correction quantity setting part, preset temperature Ts set by a temperature setting part 4, and cylinder temperature Tc detected by the temperature detector 14. The temperature control device 8 performs temperature control of the heater 10 based on temperature deviation that is a value in which cylinder temperature Tc is subtracted from a value in which temperature correction amount Tadj and preset temperature Ts are added in a computing element 6. A screw (not illustrated) drive-controlled by a screw rotary drive part 16 is built in inside the injection cylinder 12.

Description

  The present invention relates to a temperature control device for an injection molding machine having a temperature correction function and a temperature control method for an injection molding machine.

  Cylinder temperature control of an injection molding machine is generally controlled without deviation from the set temperature by PID control using temperature measuring means such as a thermocouple mounted on the cylinder and heating means such as a heater. At this time, if the residence time from when the resin material is supplied to the cylinder until it is injected is sufficiently long, heat is transferred from the inner wall of the cylinder to the resin material inside the cylinder and is injected from the cylinder. However, if the residence time from the time the resin material is supplied to the cylinder until it is injected is short, such as in molding or purging operations where the cycle time is short, the inner wall of the cylinder will Since the resin is injected from the cylinder before the heat transfer to the resin material is sufficiently performed, there is a problem that the temperature of the molten resin becomes lower than the set temperature.

  If injection is performed while the temperature of the molten resin is lower than the set temperature, the filling property of the resin into the mold may be deteriorated, or unmelted resin may be clogged in the mold gate. It is desired to prevent the temperature of the molten resin from being lowered.

  In Patent Document 1, when a set temperature corresponding to a location where molten resin is accumulated in front of the screw is set among the set temperatures set by a plurality of heaters, a set temperature other than the heater is calculated based on molding conditions. The technology required by is disclosed.

  In Patent Document 2, the temperature is controlled by the preset temperature during molding from the start of flushing or molding before molding, and when the molding is stopped or finished, the temperature is controlled by switching from the preset temperature during molding to the preset temperature during molding. Techniques to do this are disclosed.

International Publication No. 2007/105646 Japanese Patent Laid-Open No. 11-227019

In the temperature control method disclosed in Patent Document 1, the set temperature corresponding to the location where the molten resin is accumulated in front of the screw at the time of completion of measurement is a set temperature set by the operator based on intuition and experience, and depends on the molding conditions. However, there was a problem that it was difficult to set an appropriate temperature.
In the temperature control method disclosed in Patent Document 2, the set temperature during molding is a set temperature set by an operator based on intuition and experience, and there is a problem that it is difficult to set an appropriate temperature according to molding conditions. .

  Therefore, the present invention calculates the temperature correction amount of the cylinder temperature based on the residence time from when the resin material is supplied to the injection cylinder until it is injected from the injection cylinder, and adds an appropriate temperature correction amount to the set temperature. Provided a temperature control device for an injection molding machine and a temperature control method for an injection molding machine having a temperature correction function capable of preventing the temperature of the molten resin from becoming lower than a set temperature by controlling the cylinder temperature to the temperature. The task is to do.

  The invention according to claim 1 of the present application includes an injection cylinder, a heater for heating the injection cylinder, a temperature detection unit for detecting the temperature of the injection cylinder, a temperature setting unit for setting the temperature of the injection cylinder, Injection molding having a temperature control unit for controlling the detected cylinder temperature so as to match the set temperature, a screw disposed in the injection cylinder, and a screw rotation driving unit for rotationally driving the screw. In the machine, a residence time calculation unit that calculates a residence time from when the resin material is supplied to the injection cylinder until it is injected from the injection cylinder, and a first temperature correction amount of the cylinder temperature based on the calculated residence time is calculated. A first temperature correction amount calculation unit that calculates the first temperature correction amount calculation unit as the calculated residence time becomes shorter The temperature correction amount is calculated so as to increase the first temperature correction amount, and the temperature control unit controls the injection cylinder temperature by adding the calculated first temperature correction amount to the set temperature. This is a temperature control device for an injection molding machine.

According to a second aspect of the present invention, the dwell time calculation unit calculates the elapsed time per cycle to a value obtained by dividing the screw stroke corresponding to the volume in the injection cylinder by the metering stroke, the injection stroke, or the screw stroke moved during one cycle. The temperature control device for an injection molding machine according to claim 1, wherein a value obtained by multiplying time is calculated as a residence time.
According to a third aspect of the present invention, the dwell time calculation unit calculates, as a dwell time, a value obtained by multiplying a value obtained by dividing the volume in the injection cylinder by the measured resin volume per shot and the elapsed time per cycle. The temperature control device for an injection molding machine according to claim 1.

In the invention according to claim 4, the first temperature correction amount calculation unit estimates the temperature of the molten resin injected from the cylinder as an exponential function of the residence time based on the set temperature and the residence time, and the estimation The temperature control device for an injection molding machine according to any one of claims 1 to 3, wherein the first temperature correction amount is calculated so that the temperature of the molten resin matches the set temperature.
According to a fifth aspect of the present invention, the first temperature correction amount calculation unit includes:
Tadj = Ts · e ^−αt / (1−e ^−αt )
4. The first temperature correction amount is calculated based on an expression of Tadj: temperature correction amount, Ts: set temperature, α: coefficient, t: dwell time. 5. This is a temperature control device for an injection molding machine.

  According to a sixth aspect of the present invention, a screw rotation work calculation unit that calculates the work of the screw rotation drive unit per cycle, and a second temperature correction amount of the cylinder temperature based on the calculated screw rotation work. A second temperature correction amount calculation unit for calculating, and the temperature control unit adds a value obtained by subtracting the second temperature correction amount from the first temperature correction amount to the set temperature that has been set. The temperature control device for an injection molding machine according to any one of claims 1 to 5, wherein the temperature of the injection cylinder is controlled.

The invention according to claim 7 is an injection cylinder, a heater for heating the injection cylinder, a temperature detection unit for detecting the temperature of the injection cylinder, a temperature setting unit for setting the temperature of the injection cylinder, and the detection In an injection molding machine having a temperature controller that controls the cylinder temperature to match the set temperature, the residence time from when the resin material is supplied to the injection cylinder until it is injected from the injection cylinder is shortened Accordingly, the temperature control method of the injection molding machine is characterized in that the set temperature is adjusted so that the injection cylinder temperature becomes higher.
In the invention according to claim 8, the value obtained by multiplying the value obtained by dividing the screw stroke corresponding to the volume in the injection cylinder by the metering stroke, the injection stroke or the screw stroke moved during one cycle is multiplied by the elapsed time per cycle. 8. The temperature control method for an injection molding machine according to claim 7, wherein the temperature is calculated as time.
The invention according to claim 9 is characterized in that a value obtained by dividing the volume in the injection cylinder by the measured resin volume per shot and the elapsed time per cycle is calculated as the residence time. The temperature control method of the injection molding machine as described in 1 above.

  According to the present invention, even when the residence time from when the resin material is supplied to the cylinder to when it is injected is short, such as molding or purging operation with a short cycle time, the resin temperature becomes lower than the set temperature. Can be prevented. Further, according to the present invention, since the temperature control device automatically calculates and controls an appropriate cylinder temperature according to the molding conditions, it is possible to reduce the burden of adjusting the temperature setting value by the operator. Control of appropriate resin temperature can be realized regardless of experience and skill.

It is a temperature control block diagram of the injection molding machine which concerns on this invention. It is a figure which shows the graph showing the relationship between residence time and resin temperature. 7 is a flowchart for explaining processing for adding a temperature correction amount calculated based on a residence time to a set temperature during cycle operation to control the cylinder temperature, and clearing the temperature correction amount to zero when not in cycle operation. Describes the process of controlling the cylinder temperature by adding the temperature correction amount calculated based on the residence time to the set temperature during cycle operation, and calculating the temperature correction amount based on the elapsed time from the start of the previous cycle when not in cycle operation It is a flowchart. It is a flowchart explaining the process which calculates the temperature correction amount in consideration of the 1st temperature correction amount by dwell time, and the 2nd temperature correction amount by screw rotation work amount.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a temperature control block diagram of an injection molding machine according to the present invention. A heater 10 is mounted on the outer periphery of the injection cylinder 12 of the injection molding machine. The temperature of the injection cylinder 12 heated by the heater 10 is detected by a temperature detector 14. The temperature control device 8 includes a heater based on the temperature correction amount Tadj set by the temperature correction amount setting unit, the set temperature Ts set by the temperature setting unit 4, and the cylinder temperature Tc detected by the temperature detector 14. 10 temperature control is performed. The cylinder temperature Tc detected by the temperature detector 14 is output to the calculator 6 as a temperature feedback value. The temperature control device 8 controls the temperature of the heater 10 based on a temperature deviation that is a value obtained by subtracting the cylinder temperature Tc from a value obtained by adding the temperature correction amount Tadj and the set temperature Ts in the calculator 6. Inside the injection cylinder 12, a screw that is driven and controlled by a screw rotation drive unit 16 is incorporated.

  The temperature control device of the injection molding machine of the present invention calculates the temperature correction amount Tadj of the cylinder temperature Tc based on the residence time t from when the resin material is supplied to the injection cylinder 12 until it is injected from the injection cylinder 12. Controlling the cylinder temperature Tc to an appropriate temperature obtained by adding the temperature correction amount Tadj to the set temperature Ts prevents the temperature of the molten resin from becoming lower than the set temperature Ts.

A method for calculating the residence time will be described.
<Calculation method of residence time>
A residence time t is calculated by multiplying a value obtained by dividing a screw stroke corresponding to the volume in the injection cylinder 12 by a measuring stroke by an elapsed time per cycle. The volume in the injection cylinder 12 corresponds to the volume of the space existing inside the injection cylinder with the screw inserted into the injection cylinder, and the temperature is controlled in advance based on the dimensions inside the injection cylinder 12 and the dimensions of the screw. You may memorize | store in the apparatus 8, and you may make it input by an operator. The screw stroke corresponding to the volume in the injection cylinder 12 is a value obtained by dividing the volume in the injection cylinder 12 by the screw cross-sectional area.

  The metering stroke X is a value corresponding to the amount of metered resin per cycle. By dividing the screw stroke Xall corresponding to the calculated volume in the injection cylinder 12 by the metering stroke X, the resin material is transferred to the injection cylinder. The number of elapsed shots from the supply to the injection is calculated. By multiplying the number of elapsed shots by the elapsed time C per cycle, the residence time t from when the resin material is supplied to the injection cylinder until it is injected is obtained by the equation (1).

  In addition to the metering stroke X, the residence time t may be calculated based on the injection stroke or the screw stroke moved during one cycle, and the resin volume per cycle is calculated based on the dimensions of the mold cavity and the molded product. The dwell time may be calculated by obtaining the value based on the dimensions and dividing the result by the screw cross-sectional area to obtain a value corresponding to the measurement stroke.

  Alternatively, the value obtained by dividing the volume in the injection cylinder 12 by the metered resin volume V per cycle and the elapsed time C per cycle may be calculated by the formula 2 as the residence time t.

  In addition, one cycle in the present invention is defined as one cycle at the time of molding operation or purge operation. There are various ways of moving the screw in the purge operation. For example, in the case of the purge operation in which the screw advance and the screw rotation reverse are repeated, one cycle is from the start of the screw advance to the start of the next screw advance. In this case, the cycle from the start of the screw rotation backward to the start of the next screw rotation backward may be defined as one cycle.

  The elapsed time per cycle may be the cycle time of the previous cycle during continuous operation, and may be the elapsed time from the start time of the previous cycle while continuous operation is stopped. In this way, the calculated residence time t is gradually increased while the continuous operation is stopped, and the temperature correction amount Tadj calculated based on the residence time t is reduced. It is possible to prevent the temperature of the molten resin from rising above the target resin temperature Tregin at the time of stopping. Alternatively, the temperature correction amount Tadj may be invalidated when the molding operation is stopped or the purge operation is stopped, and the temperature correction may be validated during the molding operation or the purge operation.

<Calculation of first temperature correction amount based on residence time>
When the residence time is short, in order to prevent the temperature of the molten resin from becoming lower than the set temperature, the temperature correction amount is increased and the cylinder temperature is controlled to a temperature higher than the set temperature. Here, calculation of the temperature correction amount will be described.
The resin temperature is expressed as an equation 3 as an exponential function of the residence time, and gradually approaches the cylinder temperature Tc as the residence time t increases as shown in the graph of FIG.

  Here, since the cylinder temperature is controlled to a temperature obtained by adding the correction amount to the set temperature, Equation 4 is established.

  At this time, in order for the resin temperature Tregin to substantially coincide with the set temperature Ts without being lowered, the formula 5 needs to be established.

  According to Equation 3 to Equation 5, the first temperature correction amount Tadj can be obtained from Equation 6.

  The coefficient α may be obtained in advance based on a relationship between the residence time and the resin temperature by performing a preliminary experiment and stored in the temperature control device 8. Alternatively, the coefficient α may be stored in the temperature control device 8 as a table for each type of resin, and a value may be read from the table according to the resin to be molded and used for calculation.

  Further, even if the relationship between the residence time t and the resin temperature Tregin is a function different from Equation 1, if a function or an approximate function indicating the relationship between the residence time t and the resin temperature Tregin can be obtained, The temperature correction value can be obtained in the same manner as described above. For example, the function may be Tregin = f (Ts, t), and Tadj such that Ts = f (Ts + Tadj, t) at time t may be obtained. Further, the temperature correction value can also be obtained from the data of the resin temperature curve that shows the relationship between the residence time t and the resin temperature Tregin.

<Calculation of second temperature correction amount based on screw rotation work amount>
The cylinder temperature Tc may be corrected by calculating the second temperature correction amount Tadj2 in consideration of the shearing heat generated between the screw and the resin material during plasticization. Since heat generation due to shear occurs in the resin, it may be considered that the temperature of the resin immediately increases regardless of the residence time t. Therefore, the amount of temperature increase due to shear heat generation is calculated as the second temperature correction amount Tadj2, and the value obtained by subtracting the second temperature correction amount Tadj2 from the first temperature correction amount Tadj2 is calculated as shown in Equation 7. The injection cylinder temperature Tc may be controlled by adding to the set temperature Ts.

  The amount of heat generated by the shearing heat is approximately equal to the amount of work given from the screw rotation motor that is the screw rotation drive unit 16 during plasticization, and therefore may be calculated based on the amount of work of the screw rotation motor being plasticized. The work amount of the screw rotation motor during plasticization is obtained by, for example, integrating the product of the screw rotation driving force and the screw rotation speed over time from the start to the end of one cycle, as shown in Formula 8.

  The second temperature correction amount Tadj2 is obtained as an increase amount of the resin temperature due to the screw rotation work amount as shown in the equation (9).

Hereinafter, the flow of temperature control in the embodiment of the present invention will be described.
FIG. 3 is a flowchart illustrating a process for controlling the cylinder temperature by adding the temperature correction amount calculated based on the residence time to the set temperature during the cycle operation, and clearing the temperature correction amount to zero when the cycle operation is not performed. Hereinafter, it demonstrates according to each step.
[Step SA01] It is determined whether or not the cycle operation is being performed. If the cycle operation is being performed, the process proceeds to Step SA03. If the cycle operation is not being performed, the process proceeds to Step SA02.
[Step SA02] The first temperature correction amount Tadj is cleared to zero and commanded to the temperature controller.
[Step SA03] The residence time is calculated by t = (Xall / X) · C (see Equation 1).
[Step SA04] The first temperature correction amount Tadj is calculated by the equation (6).
[Step SA05] The first temperature correction amount Tadj is added to the set temperature Ts to instruct the temperature controller.
[Step SA06] The temperature control device controls the cylinder temperature in accordance with the command of Step SA02 or Step SA05.
[Step SA07] It is determined whether or not the temperature control is finished. If not finished (NO), the process returns to step SA01, and if finished (YES), the process is finished.

FIG. 4 shows that during the cycle operation, the temperature correction amount calculated based on the residence time is added to the set temperature to control the cylinder temperature. When the cycle operation is not performed, the temperature correction amount is calculated based on the elapsed time from the start of the previous cycle. It is a flowchart explaining a process.
Hereinafter, it demonstrates according to each step.
[Step SB01] It is determined whether or not the cycle operation is being performed. If the cycle operation is being performed, the process proceeds to Step SB03. If the cycle operation is not being performed, the process proceeds to Step SB02.
[Step SB02] The elapsed time per cycle is the elapsed time from the start of the previous cycle.
[Step SB03] The elapsed time per cycle is the cycle time of the previous cycle.
[Step SB04] The residence time is calculated by t = (Xall / X) · C (see Equation 1).
[Step SB05] The first temperature correction amount Tadj is calculated by the equation (6).
[Step SB06] The first temperature correction amount Tadj is added to the set temperature Ts to instruct the temperature controller.
[Step SB07] The temperature control device controls the cylinder temperature in accordance with the command of Step SB06.
[Step SB08] It is determined whether or not the temperature control is finished. If not finished (NO), the process returns to Step SB01, and if finished (YES), the process is finished.

FIG. 5 is a flowchart for explaining processing for calculating the temperature correction amount in consideration of the first temperature correction amount based on the residence time and the second temperature correction amount based on the screw rotation work amount.
Hereinafter, it demonstrates according to each step.
[Step SC01] It is determined whether or not the cycle operation is being performed. If the cycle operation is being performed, the process proceeds to Step SC03. If the cycle operation is not being performed, the process proceeds to Step SC02.
[Step SC02] First temperature correction amount Tadj and second temperature correction amount Tadj2 are cleared to zero and commanded to the temperature controller.
[Step SC03] The residence time is calculated by t = (Xall / X) · C (see Equation 1).
[Step SC04] The first temperature correction amount Tadj is calculated by Equation (6).
[Step SC05] The shear heating value is calculated by the following equation (8).
[Step SC06] The second temperature correction amount is calculated by Equation (9).
[Step SC07] A value obtained by subtracting the second temperature correction amount Tadj2 from the first temperature correction amount Tadj is added to the set temperature Ts to instruct the temperature controller.
[Step SC08] The temperature control device controls the cylinder temperature in accordance with the command of Step SC02 or Step SC07.
[Step SC09] It is determined whether or not the temperature control is finished. If not finished (NO), the process returns to step SC01, and if finished (YES), the process is finished.

2 Temperature correction amount setting unit 4 Temperature setting unit 6 Calculator 8 Temperature control device 10 Heater 12 Injection cylinder 14 Temperature detector 16 Screw rotation drive unit

Claims (9)

An injection cylinder, a heater for heating the injection cylinder, a temperature detection unit for detecting the temperature of the injection cylinder, a temperature setting unit for setting the temperature of the injection cylinder, and the setting for which the detected cylinder temperature is set In an injection molding machine having a temperature control unit that controls to match the temperature, a screw disposed in the injection cylinder, and a screw rotation driving unit that rotationally drives the screw,
A residence time calculation unit that calculates a residence time from when the resin material is supplied to the injection cylinder until it is injected from the injection cylinder;
A first temperature correction amount calculation unit that calculates a first temperature correction amount of the cylinder temperature based on the calculated residence time;
The first temperature correction amount calculation unit calculates a temperature correction amount so that the first temperature correction amount increases as the calculated residence time becomes shorter, and the temperature control unit calculates the first temperature correction amount. A temperature control device for an injection molding machine, wherein the temperature of the injection cylinder is controlled by adding the temperature correction amount to the preset set temperature.   The residence time calculation unit is obtained by multiplying a value obtained by dividing a screw stroke corresponding to the volume in the injection cylinder by a metering stroke, an injection stroke, or a screw stroke moved during one cycle by an elapsed time per cycle. The temperature control device for an injection molding machine according to claim 1, wherein   The residence time calculation unit calculates a residence time by multiplying a value obtained by dividing a volume in an injection cylinder by a measured resin volume per shot and an elapsed time per cycle. The temperature control apparatus of the injection molding machine as described.   The first temperature correction amount calculation unit estimates the temperature of the molten resin injected from the cylinder as an exponential function of the residence time based on the set temperature and the residence time, and the estimated temperature of the molten resin is the set temperature. The temperature control device for an injection molding machine according to any one of claims 1 to 3, wherein the first temperature correction amount is calculated so as to coincide with the above. The first temperature correction amount calculation unit includes:
Tadj = Ts · e ^−αt / (1−e ^−αt )
4. The first temperature correction amount is calculated based on an expression of Tadj: temperature correction amount, Ts: set temperature, α: coefficient, t: dwell time. 5. Temperature control device for injection molding machine.   A screw rotation work amount calculation unit that calculates the work amount of the screw rotation drive unit per cycle, and a second temperature correction amount that calculates a second temperature correction amount of the cylinder temperature based on the calculated screw rotation work amount A calculating unit, wherein the temperature control unit controls the injection cylinder temperature by adding a value obtained by subtracting the second temperature correction amount from the first temperature correction amount to the set temperature. The temperature control device for an injection molding machine according to any one of claims 1 to 5, characterized in that: An injection cylinder, a heater for heating the injection cylinder, a temperature detection unit for detecting the temperature of the injection cylinder, a temperature setting unit for setting the temperature of the injection cylinder, and the setting for which the detected cylinder temperature is set In an injection molding machine having a temperature control unit that controls to match the temperature,
A temperature control method for an injection molding machine, characterized in that the set temperature is adjusted so that the temperature of the injection cylinder increases as the residence time from when the resin material is supplied to the injection cylinder until it is injected from the injection cylinder becomes shorter. .   The residence time is calculated by multiplying the value obtained by dividing the screw stroke corresponding to the volume in the injection cylinder by the metering stroke, injection stroke, or screw stroke moved during one cycle, and the elapsed time per cycle. The temperature control method for an injection molding machine according to claim 7.   The temperature of the injection molding machine according to claim 7, wherein a value obtained by dividing the volume in the injection cylinder by the measured resin volume per shot and the elapsed time per cycle is calculated as the residence time. Control method.

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