JPH0494915A - Control method for injection molding machine - Google Patents

Abstract

PURPOSE:To set easily and securely the optimum resin state in a heating cylinder by sensing the temperature state in the vicinity of a material dropping hole of a material feeding mechanism communicating with the inside of heating cylinder and control variably control elements affecting the resin state. CONSTITUTION:The temperature state in the vicinity of a material dropping hole 7 of a material feeding mechanism 6 communicating with the inside of heating cylinder 3 is sensed by a temperature sensor 5 or the like. The temperature characteristics in the vicinity of a material dropping hole 7 varies up and down periodically synchronized with the molding cycle in the normal time. Therefore, for instance, the size of amplitude of temperature variation is monitored, and the temperature characteristics can be sensed and the resin state can be sensed in the early stage. The temperature state thus obtained, therefore, is compared with, for instance, the preset target value or the monitoring range, and based on said deviation, control elements affecting the resin state, for instance, the material feeding quantity in a material feeding mechanism 6, the heating temperature in a plurality of heating zones in the heating cylinder 3, the heating temperature of the material feeding mechanism 6, the number of rotations of screw 2 and/or back pressure and the like are varied, and respective control elements are controlled successively according to the priority order set preliminarily to provided the optimum resin state as above-referred.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of controlling an injection molding machine equipped with a heating cylinder incorporating a screw and having a material supply mechanism at the rear thereof.

[Prior art and its issues]

Maintaining the optimal resin condition (resin temperature, resin amount, fluidity, etc.) inside the heating cylinder of an injection molding machine is
It is also important for improving molding quality.

By the way, since the resin is transferred inside the heating cylinder by the rotation of the screw, it is necessary to accurately grasp the state of the resin as described above.
And it is not easy to control accurately. For example, the heating zone of a heating tube is divided into multiple sections in the front and back direction, and a different temperature is set for each heating zone, but the temperature is detected individually by a temperature sensor attached to the position of each heating zone. Since the heating is carried out at different times, it is difficult to grasp the actual resin temperature, and the temperature of each heating zone cannot be uniquely determined.

In the end, in the past, operators relied on the overall molding condition and made adjustments based solely on their experience and intuition, which not only made it impossible to make accurate settings, but also took a lot of time and effort. This requires a lot of effort, and since the resin temperature also depends on various other control factors such as the material temperature before the heating tube falls, the amount of resin, and the number of screw rotations, it is difficult to keep the resin temperature and even the resin condition at the optimum state. The problem was that it was difficult to maintain the

The present invention solves the problems that exist in the prior art, and aims to provide a control method for an injection molding machine that can easily and reliably set the optimum resin condition within the heating cylinder.

[Means to solve the problem]

The method for controlling an injection molding machine according to the present invention is to supply material facing the heating cylinder 3 when controlling an injection molding machine 1 comprising a heating cylinder 3 having a built-in screw 2 and a material supply mechanism 6 at the rear. The temperature state near the material dropping lower of the mechanism 6 is detected, and based on the detected temperature state, control elements that affect the resin state, such as the amount of material supplied in the material supply mechanism 6 and the number of heating zones in the heating cylinder 3, are controlled. Heating temperature,
It is characterized in that the heating temperature in the material supply mechanism 6, the rotation speed of the screw 2, the back pressure, etc. are variably controlled. In this case, it is possible to set priorities for a plurality of control elements and sequentially control them according to the priorities.

[For production]

According to the control method for the injection molding machine 1 according to the present invention, the temperature state near the material dropping lower of the material supply mechanism 6 facing into the heating cylinder 3 is detected by the temperature sensor 5 or the like. Under normal conditions, the temperature characteristics near the material drop lower periodically rise and fall in synchronization with the molding cycle, that is, the temperature repeats changes in which it rises during measurement and falls at times other than measurement. Therefore, for example, by monitoring the temperature state such as the magnitude of the amplitude of a fluctuating temperature change, it is possible to detect an abnormality in the temperature characteristics. In this case, since the initial state of plasticization is detected, the state of the resin can be detected early.

Therefore, the obtained temperature state is compared with, for example, a preset target value or a monitor range, and based on this comparison deviation, control elements that affect the resin state, such as the material supply amount in the material supply mechanism 6, heating The heating temperature of the plurality of heating zones in the cylinder 3, the heating temperature in the material supply mechanism 6, the rotation speed and/or back pressure of the screw 2, etc. are varied, and each control is performed according to preset priorities to achieve the optimal resin state. Control elements sequentially.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described in detail based on the drawings.

First, the configuration of a vent type injection molding machine and its control system that can implement the control method according to the present invention will be explained with reference to FIG.

1 is a vent type injection molding machine, and shows the injection device Is excluding the mold side. The injection device Is includes a heating cylinder 3 having an injection nozzle 11 at its front end, and the heating cylinder 3 houses a screw 2 whose rotation and movement are controlled by a screw drive mechanism 12 provided at its rear end. Further, a vent hole 4 is provided at an axially intermediate position of the heating cylinder 3 and at an upper portion thereof.

This vent hole 4 communicates the inside and outside of the heating cylinder 3,
As the screw 2 rotates, water vapor and gas components generated from the plasticized and melted resin are discharged to the outside.

Furthermore, the heating tube 3 is provided with heating zones divided into five in the front and back direction, and band heaters 13a and 13 are provided on the outer periphery of the heating tube 3 corresponding to each heating zone to heat the heating tube 3.
bS Install 13c113d and 13e. On the other hand, a material supply mechanism 6 is provided at the rear of the heating cylinder 3. This material supply mechanism 6 includes a supply pipe 14 that communicates with the inside of the heating cylinder 3, a hopper 15 that communicates with this supply pipe 14, and this hopper 1.
Transfer screw 16a provided below 5 and the same screw 1
A material supply control device 16 is provided that includes a transfer screw drive unit 16b that controls the rotation of the supply pipe 6a, and a band heater 17a that heats the supply pipe 14 is provided on the outer periphery of the supply pipe 14.
, 17b... are provided.

Further, a temperature sensor 5 is attached near (in front of) the material dropping lower of the material supply mechanism 6 facing the heating cylinder 3.

The temperature sensor 5 is connected to the temperature processing section 21, and the processing section 21 is connected to the calculation section 22.
controller 23 directly and via the abnormality determination circuit 25
Connect to.

On the other hand, temperature sensors 24a, 24b, 24c, and
..., and its output side is connected to controller 2.
Connect to 3. Further, the band heaters 13a, . . . , 17a, . . . , the screw drive mechanism section 12, and the transfer screw drive section 16b are also connected to the controller 23, respectively.

Next, a method of controlling the vent type injection molding machine 1 according to the present invention will be explained with reference to FIGS. 1 to 6.

First, during a predetermined molding cycle, the temperature near the material dropping lower is detected by the temperature sensor 5. In this case, as shown in FIG. 4, under normal conditions, the detected temperature repeatedly rises and falls in synchronization with the molding cycle. That is, at the time of measurement, the temperature rises due to frictional heat generation of the molding material, and at times other than the time of measurement, there is no heat generating element and the temperature decreases. In FIG. 4, 8 points indicate the starting point of molding, C indicates one molding cycle, and P indicates the amplitude of temperature change.

On the other hand, the detection signal detected by the temperature sensor 5 is provided to the temperature processing section 21, and, for example, the amplitude P of the temperature change in each molding cycle is determined.

The output of the temperature processing section 21 is then given to the calculation section 22. The calculation unit 22 compares the amplitude P of the temperature change (or detected temperature T, etc.) with a preset target value (or monitor range, limit value, etc.), and uses the obtained comparison deviation to control a predetermined control element. That is, the control information for the heating temperature of each heating zone in the heating cylinder 3, the material supply amount of the material supply mechanism 6 and the heating temperature of the supply pipe 14, the rotation speed and/or back pressure of the screw 2 is calculated, and the control information is sent to the controller 23. Give. Therefore, the controller 23 sends a predetermined control signal to each band heater 13a, 13b, . . . of the heating tube 3 based on the control information.
, the material supply control bag 4116 and the band heater 17a in the material supply mechanism 6, and the screw drive mechanism section 12.

Incidentally, in this case, the calculation section 22 determines the control elements and calculates the control amount according to the control pattern shown in FIG. 2 or 3. First, as shown in FIG. 2, the magnitude of the amplitude P of the temperature change obtained from the temperature processing unit 21 is compared to the target value, "■ amplitude is small", "■ amplitude is large", "■ amplitude is In response to this,
"& Raise the temperature of the heating cylinder", "b Decrease the temperature of the heating cylinder", "C Increase the screw rotation speed during measurement", "d Decrease the screw rotation speed during measurement", "e Increase the back pressure ”
, "f lower back pressure", "g increase material supply amount",
The controller provides control information for executing the following controls: "h Decrease the material supply amount,""i Increase the material supply temperature," and "j Decrease the material supply temperature" according to the connection lines and priorities in Figure 2. Granted to 23. This allows, for example,
If the amplitude P of the temperature change is small as shown by E2 in Fig. 5 (Eo is normal), it corresponds to "■ amplitude is small" in Fig. 2, and in this case, first, "b heating cylinder (Priority 1) Furthermore, if this control does not improve the situation and the amplitude of the temperature change does not increase, then control is performed to "increase the amount of g material supplied" (priority order 2). Until such controls are improved,
They are performed in order of priority. Note that if the problem is not improved even after a predetermined period of time has elapsed after all preset control elements have been controlled, abnormality processing, that is, control such as generation of an alarm and stopping of operation, is performed.

On the other hand, as shown in FIG. 3, the magnitude of the detected temperature T is "
■Rising above the monitor range", "■Lowering below the monitor range",
In the case of "■ The amplitude exceeds the upper limit and the amplitude is larger than the upper limit", corresponding actions such as "a raise the temperature of the heating cylinder" and "
b. Decrease the temperature of the heating cylinder", "C. Increase the screw rotation speed during measurement", "d. Decrease the screw rotation speed during measurement".
, "e increase back pressure", "f decrease back pressure", "g increase material supply amount", "h decrease material supply amount",
The controller 23 is provided with control information for executing each control of "i increase the material supply temperature" and "j decrease the material supply temperature" according to the connection lines and priorities in FIG. 3.

In addition, "rising above the monitor range" means that when the temperature T becomes larger than the upper limit of the monitor range M, as shown by E3 in FIG. 5, "falling below the monitor range" means E4 in FIG.
As shown in , when the temperature T becomes smaller than the lower limit of the monitor range M, "the upper limit is exceeded and the amplitude is larger than the upper limit" means that
As shown by E5 in FIG. 6, this is a case where the amplitude becomes large, exceeds the limit value, and does not decrease even if the control is continued.

Therefore, for example, when the temperature rises above the monitor range (■), the control is first performed to "lower the temperature of the heating cylinder b" (priority order 1). If the amplitude of the temperature change does not increase even with this control, the control is then performed to "reduce the amount of material h supplied" (priority order 2).

Such control is performed sequentially in priority order until improvements are made. In addition, "■The amplitude is larger than the upper limit"
In this case, after a predetermined period of time has elapsed, the abnormality determination circuit 25 performs abnormality processing, that is, controls such as issuing an alarm and stopping operation.

Therefore, by detecting the temperature near the material falling lower as a temperature closely related to the resin condition, early detection and accurate detection can be performed, and the resin condition can be controlled to the optimum resin condition through calculation processing. Ru. Note that the calculation unit 22 can also perform AI control, etc., if necessary.

Although the embodiments have been described in detail above, the present invention is not limited to these embodiments.

For example, the control patterns shown in FIG. 2 and FIG. 3 may be combined and performed simultaneously, and various control elements other than those illustrated may be added. Further, during control, the resin temperature may be displayed, and the control elements may be manually operated in accordance with the display. Furthermore, although a vent type injection molding machine is illustrated, the present invention can be similarly applied to a general injection molding machine without a vent hole by only slightly changing the control pattern. In addition, the detailed structure, method, etc. may be arbitrarily changed without departing from the gist of the present invention.

〔Effect of the invention〕

As described above, the injection molding machine control method according to the present invention detects the temperature state near the material drop port of the material supply mechanism facing into the heating cylinder, and influences the resin state based on the detected temperature state. Since the control elements are variably controlled, the following remarkable effects are achieved.

■ Since the temperature closely related to the resin condition can be detected early and accurately, the optimum resin temperature and even the optimum resin condition can be easily and reliably set, and molding quality can be improved.

■ Since the optimal resin condition is automatically set, labor savings and productivity improvements can be achieved.

[Brief explanation of drawings]

1N: A block system diagram showing a control system of an injection molding machine that can carry out the control method according to the present invention. FIGS. 2 and 3: A pattern diagram showing an example of a control pattern of the calculation unit in the control system. 4N : A temperature characteristic diagram showing the temperature state detected by the method of the present invention. FIGS. 5 and 6: An explanatory diagram showing changes in the temperature state. In the drawing, 1: Injection molding machine 2: Screw 3: Heating tube 4: Vent hole: Material supply mechanism: Material dropping port

Claims (9)

[Claims] (1) In a method for controlling an injection molding machine equipped with a heating cylinder having a built-in screw and a material supply mechanism at the rear, detecting the temperature state near the material drop port of the material supply mechanism facing into the heating cylinder, A method for controlling an injection molding machine, comprising variably controlling control elements that affect a resin state based on a detected temperature state. (2) The method for controlling an injection molding machine according to claim 1, wherein the temperature state is the amplitude of a temperature change that periodically fluctuates in synchronization with a molding cycle. (3) The method for controlling an injection molding machine according to claim 1, wherein the temperature state is a temperature level relative to a preset monitor range. (4) After setting a limit value for the temperature state and variably controlling the control element, if the temperature does not fall within the limit value even after a predetermined period of time has elapsed, abnormality processing is performed. The method for controlling the injection molding machine described. (5) A method for controlling an injection molding machine according to claim 1, characterized in that priorities are set for a plurality of control elements and the control is performed sequentially according to the priorities. (6) The method for controlling an injection molding machine according to claim 1, wherein the control element is the amount of material supplied in the material supply mechanism. (7) The method for controlling an injection molding machine according to claim 1, wherein the control element is the heating temperature in the heating cylinder. (8) The method for controlling an injection molding machine according to claim 1, wherein the control element is a heating temperature in the material supply mechanism. (9) The method for controlling an injection molding machine according to claim 1, wherein the control element is the rotational speed of the screw and/or the back pressure.